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ESA 1 Revision > ToB > Flashcards

ToB Flashcards

1
Q

State the relationship between

  • meters
  • millimetres
  • micrometres
  • nanometres
  • angstroms
A

Metre = m

Millimetre = 10 to the -3 m

Micrometre = 10 to the -6 m

Nanometre = 10 to the -9 m

Angstrom = 10 to the -10 m

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2
Q

State the meaning of the term tissue.

A

A collection of cells specialised to perform a particular function.

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3
Q

What to aggregations of tissues constitute?

A

Organs.

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4
Q

Define histology.

A

The study of the structure of tissues by means of special staining techniques combined with light and electron microscopy.

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5
Q

Why is histology valuable in diagnosis?

A

In many diseases such as Crohn’s, treatment is not given until the histopathologists have given a diagnosis. A biopsy and histology is the final proof for many diseases, like lung/breast cancer.

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6
Q

Define the term biopsy.

A

The removal of a small piece of tissue from an organ or part of the body for microscopic examination.

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7
Q

Describe a smear and give an example of a tissue that can be sampled by this method.

A

Collecting cells by spontaneous/ mechanical exfoliation, and smear on the slide.

Example tissue: cervix, buccal cavity.

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8
Q

Describe a curettage and give an example of a tissue that can be sampled by this method.

A

Removal of tissue by scooping/ scraping.

Example of tissue: endometrial lining of the uterus.

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9
Q

Describe a needle biopsy and give an example of a tissue that can be sampled by this method.

A

Put needle into tissue to gather cells.

Example of tissues: brain, breast, liver, kidney, muscle.

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10
Q

Describe a direct incision biopsy and give an example of a tissue that can be sampled by this method.

A

Cut directly into the tissue of interest and remove the tissue.

Example of tissue: skin, mouth, larynx.

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11
Q

Describe an endoscopic biopsy and give an example of a tissue that can be sampled by this method.

A

Removal of tissue via instruments through an endoscope.

Example of tissue: lung, intestine, bladder.

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12
Q

Why does tissue in a slide need to be fixed?

What does it do the proteins?

A

To confer stability; unfixed tissues are subject to putrefaction and attack by autolytic enzymes.

It makes proteins insoluble. Macromolecular cross linkage.

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13
Q

Name two common fixatives.

A

Formaldehyde and glutaraldehyde.

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14
Q

Describe how tissue processing can lead to the formation shrinkage artefacts.

A

During slide preparation the tissue is dehydrated then rehydrated, which can lead to abnormalities in the final slide.

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15
Q

Describe the 5 steps of tissue preparation for microscopy.

A
  1. FIXATION: add formaldehyde/glutaraldehyde, cross linking adjacent proteins, arresting biological activity.
  2. DEHYDRATION AND CLEARING: Ethyl alcohol replaces water, cleared with xylene/toluene to make miscible with wax.
  3. WAX EMBEDDING: wax impregnation at 56C, solidifies so it can be sectioned.
  4. STAINING: xylene clears wax, hydrated with descending % of alcohol, as most stains are water soluble. Dyes selectively stain components based on chemical nature.
  5. MOUNTING: Slides are dehydrated, placed in xylene, mounted on xylene based medium, coverslip placed on top.
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16
Q

What does H&E stand for?

A

Haemotoxylin and Eosin

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17
Q

What does PAS stand for?

A

Periodic Acid-Schiff

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18
Q

What does haemotoxylin stain in cells, and what colour does it stain them?

A

It stains ACIDIC compoonents of cells, PURPLE/BLUE.

  • Nucleolus (RNA)
  • Chromatin (DNA)
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19
Q

What does eosin stain in cells, and what colour does it stain them?

A

It stains BASIC components of cells, PINK.

  • Most cytoplasmic proteins
  • Extracellular fibres
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20
Q

What does Periodic Acid-Schiff stain, and what colour does it stain them?

A

It stains CARBOHYDRATES and GLYCOPROTEINS.

MAGENTA

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21
Q

What is PHASE CONTRAST microscopy?

Advantages?

A

Using the interference effects of two combining light waves.

Advantage: It enhances the image of unstained cells.

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22
Q

What is DARK FIELD microscopy?

Advantages?

A

Exclude unscattered beam (light/electron) from the image.

Advantages: can use live and unstained samples.

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23
Q

What is FLUORESCENCE microscopy?

Advantages?

A

Targets molecule of interest with fluorescence.

Advantage: can use multiple fluorescent stains on one specimen.

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24
Q

What is CONFOCAL microscopy?

Advantages?

A

Tissue labelles with one or more fluorescent probes.

Advantage: Eliminates ‘out of focus flare’, 3D imaging from a series of 2D images, imaging of living specimens.

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25
Q

Define epithelia

A

Sheets of continguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces.

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26
Q

2 examples of an exterior surface with an epithelial lining.

Which germ layer do they come from?

A

Skin

Cornea of eye

ECTODERM

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27
Q

3 examples of interior surfaces opening to the exterior that have epithelial linings.

Which germ layer do they come from?

A

Gastrointestinal tract. ENDODERM

Respiratory tract. ENDODERM

Genitourinary tract. MESODERM

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28
Q

5 examples of interior spaces not opening to the exterior which have epithelial linings.

Which germ layer do they come from?

A

Pericardial sac

Pleural sac

Peritoneum

Blood vessels

Lymphatic vessels

All come from the MESODERM

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29
Q

What are the two main ways of classifying epithelium? (explain both)

A

SIMPLE: one cell layer thick

STRATIFIED: more than one cell layer thick

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30
Q

What are the 4 types of simple epithelia?

A

Squamous

Cuboidal

Columnar

Pseudostratified

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31
Q

What are the 5 types of stratified epithelia?

A

Squamous - keratinised

Squamous - non keratinised

Cuboidal

Columnar

Transitional

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32
Q

Name some locations and functions of simple squamous epithelia.

A

Locations: blood vessel lining (ENDOTHELIUM), lining of body cavities (MESOTHELIUM, pericardium, pleura, peritoneum), alveoli, Bowman’s capsule, Loop of Henle. inner and middle ear.

Functions: lubrication (viscera), gas exchange, barrier (Bowman’s), active transport via pinocytosis (meso/endothelium).

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33
Q

Name some locations and functions of simple cuboidal epithelium.

A

Locations: Glands (thyroid follicles, small ducts of many exocrine glands), kidney tubules, germinal epithelium surface of ovary.

Functions: absorption and conduit (exocrine glands), absorption and secretion (kidney tubules), barrier/covering (ovary), hormone synthesis, storage and mobilisation (thyroid).

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34
Q

Name some locations and functions of simple columnar epithelium.

What feature might it have on its apical surface?

A

Locations: stomach lining and gastric pits, small intestine and colon, gallbladder, large ducts of some exocrine glands, uterus, oviducts, ductuli efferents of testis (epididymis)

Functions: absorption, secretion, lubrication, transport.

MICROVILLI

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35
Q

What is a zona occludens?

A

A tight junction

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36
Q

What does occludin do?

A

Binds adjacent plasma membranes together tightly, so membrane proteins can not bypass and are restricted to the apical surface, and segregate others to the lateral and basal surfaces.

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37
Q

Name some locations and functions of simple pseudostratified epithelia.

What other features might they have?

A

Locations: URT (lining of nasal cavity, trachea and bronchi), epididymis and ductus deferens, auditory tube, tympanic cavity, lacrimal sac, large excretory ducts.

Functions: secretion and conduit (URT, ductus deferens), absorption (epididymis), mucus secretion (URT), particle trapping and removal (URT).

CILIA, MUCUS SECRETION

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38
Q

Name some locations and functions of stratified squamous keratinised epithelium.

A

Locations: surface of skin, limited distribution in oral cavity.

Functions: prevents water loss, protection against abrasion and physical trauma, prevents ingress of microbes, shields against UV light damage.

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39
Q

Name some locations and functions of transitional stratified epithelium.

A

Locations: renal calcyes, ureters, urethra, bladder

Functions: distensibility, protection of underlying tissue from toxic chemicals.

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40
Q

What and where is the basement membrane?

A

The thin, flexible, acellular layer which lies between the epithelial cells and the subtending connective tissue.

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41
Q

What lays down the basal lamina?

A

The epithelial cells

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42
Q

What is the structure of the basement membrane?

A

The basement membrane and various other layers. There is also a reticular fibre (type III collagen) layer, the thickness of which can be changed.

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43
Q

What is the function of the basement membrane?

A

A strong, flexible layer to which epithelial cells adhere. Also serves as a cellular and molecular filter.

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44
Q

How is the basement membrane related to prognosis of cancer?

A

The degree to which malignant cells penetrate the basement membrane is related to prognosis.

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45
Q

Cell renewal rate in epithelial tissues is normally constant. What can accelerate it?

A

Injury.

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46
Q

How long does it take from cell division in the basal layer of the epidermis to finally being sloughed off?

A

28 days.

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47
Q

How often are small intensinal epithelial cells replaced from the base of the crypts?

A

4-6 days

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48
Q

What are sterocilia?

Where might they be found?

A

Very long microvilli, which may have an absorbative function.

Ductus deferens and epididymis.

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49
Q

What is the average size of a human cell?

A

10 to 20 micrometers

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50
Q

What makes us the epithelial basement membrane?

A

Basal lamina (lamina lucida and densa) and lamina reticularis

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51
Q

What are microvilli?

A

Extensions of the cell membrane, core of which is a cluster of actin fialmenets embedded in villin

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52
Q

What is metaplasia?

Give an example

A

Transforming to another cell type

Stratified squamous epithelium is replaced by simple columnar epithelium with goblet cells

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53
Q

What does the basement membrane do?

A

Molecular filter

Regulates cell migration

Epithelial regeneration

Cell to cell interactions

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54
Q

What is a zonula occludens?

A

A tight junction between cells that makes it virtually impermeable to fluid

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55
Q

What is a gap junction?

A

Permits cells to communicate

Can be closed

Directly connects cytoplasm

Analagous to plasmodesmata in plants

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56
Q

What is a desmosome?

What is a hemidesmosome?

A

Desmosome: macula adherens, anchoring junction for cell to cell adhesion. Lateral, help to resist shearing forces in simple and stratified squamous epithelium

Hemidesmosome: mediate adherence to the basal lamina.

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57
Q

How are most glands formed?

What are the secreting cells of a gland called?

A

By epithelial downgrowths into surrounding connective tissue

Parenchyma

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58
Q

Define a gland.

A

An epithelial cell or collection of cells that are specialised for secretion

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59
Q

How are glands classified by destination?

A

Exocrine: a gland with ducts that open into the lumen of an organ or onto the surface of the skin

Endocrine: a gland that secretes directly into the bloodstream or lymphatic system, ductless. Arranged as cords, follicles or clusters around a profuse blood supply for transport

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60
Q

How are glands classified by structure?

A

Unicellular, such as goblet cells, release secretion onto surface epithelium

Multicellular: duct system, extends from surface to underlying connective tissue

Uncoiled, coiled

Simple, complex

Unbranched, branched

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61
Q

What is a mixed gland?

Give an example

A

A gland with both endocrine and exocrine components

Pancreas

Exocrine secretes enzymes through ducts to the duodenum, D2. Acinar cells

Endocrine, Islets of Langerhans, Insulin and Glucagon to the blood

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62
Q

What is a goblet cell?

What does it secrete?

What type of epithelium is it?

A

Unicellular gland

Secretes mucin which combines with water to form mucus

Mucus onto the apical surface to lubricate respiratory tract, intestines etc

Simple columnar eputhlium

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63
Q

What is an acinus?

Give an example of an organ in which acini are found in

A

Swelling of secretory glands at the end of a tube

The pancreas is multi acinar

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64
Q

What types of simple glands are there?
Give examples

A

Simple tubular: intestinal cells

Simple coiled: merocrine sweat glands

Simple branched tubular: gastric glands, mucous glands of oesophagus, tongue, duodenum

Simple branched acinar: sebaceoud glands.

Simple acinar is only a developmental stage

Acinar is aka alveolar

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65
Q

What typre of compound glands are there?

Give examples

A

Compund tubular: mucous glands in mouth, bulbourethral glands in males, testes in the seminiferous tubule

Compound acinar: mammary glands

Compound tubuloacinar: salivary, pancreas, glands of respiratory tract

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66
Q

How are glands classified by their method of secretion?

Give examples

A

Merocrine: exocytosis, most glands. Salivary glands, pancrease

Holocrine: disintegration of the entire cell, sebaceous gland disintegrate to fill hair follicle with sebum

Apocrine: Non membrane bounded lipid secretion, mammary glands, myoepithelial cells assist

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67
Q

How are glands classified by their nature of secretion?

How effectively are they stained by H and E?

A

Mucous: contain mucus and are high in mucins, which are highly glycosylated polypeptides. They stain poorly with H and E.

Serous: often contain enzymes, are watery and free of mucus. Stain pink with H and E, so are eosinophilic.

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68
Q

Describe the process of merocrine secretion

A

Membrane bound vesicle approaches cell surface

Fuses with plasma membrane

Contents of vesicle released into extracellular space

Plasma membrane is transiently larger

Membrane is retrieved which stabilises the cell surface area

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69
Q

Describe apocrine secretion

A

Non membrane bound lipid particle approaches the cell surface

Fuses with the plasma membrane, pushes up apical membrane

Thin layer of apical cytoplsam drapes around the droplet, surrounding droplet pinches off the cell

Plasma membrane transiently smaller

Membrane added to regain cell surface area

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70
Q

Describe holocrine secretion

A

Disintegration of entire cell

Release of contents

Discharge of the whole cell

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71
Q

What is endocytosis?

A

Engulfing of material initially outside of the cell

Opposite of exocytosis

Coupled wtuih exocytosis in transepithelial transport

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72
Q

What is transepithelial transport?

A

When a molecule is too large to penetrate membranes it can be shunted across from one bodily compartment to another

Material is endocytosed at one surface

Transport vesicle shuttles it across the cytoplasm

Vesicle and material is exocytosed at the oppostie surface

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73
Q

Describe the structure of the Golgi apparatus

A

Stack of disc shaped cisternae

One side is flate, the other side is concave

Discs have swellings at their edges where vesicles bud off: migratory Golgi vacuoles

Cis face to trans face

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74
Q

What is the function of the golgi apparatus?

A

Sorting into different compartments

Packaging through condensation of contents

Adding sugars to proteins and lipids: GLYCOSYLATION, in the cisternae, vesicles move to the flat face

Transport

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75
Q

What are the destinations of products from the golgi apparatus?

A

Majority extruded in secretory vesicles

Some retained for use in the cell e.g lysosomes

Some eneter the plasma membrane , glycocalyx

Or are secreted

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76
Q

How does glycosylation in the golgi apparatus increase specificity?

What happens if enzymes destory the glycocalyx ?

A

SUGARS MAKE MOLECULES MORE SPECIFIC

Branching sugars offer complex shapes for specific interations in the glycocalyx

Destruction of the glycocalyx by enzymes alters specificity of cells: adhesions to substrates and neighbouring cells, communication with neighbouring cells, contact inhibition of movement and division, mobility of cells

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77
Q

Name 4 types of control of secretion? Examples

A

Nervous: sympathetic netvous stimulate of the adrenal medulla leads to the release of adrenaline

Endocrine: ACTH stimulate release of cortisol from the cortex of the adrenal glands, zona fasciculata

Neuroendocrine: Nervous cells of the hypothalamus control the release of ACTH by CRH

Negative feedback chemical mechanism: inhibitory effect of high t3/4 on TRH and TSH

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78
Q

What are the 3 major salivary glands?

What is the nature of secretion from each?

A

Parotid: serous

Sub-mandibular: mixed, mucous and serous

Sub-lingual: more mucous but mixed

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79
Q

Classify the following glands as exocrine or endocrine

Goblet cells in jejunum/colon, Pancreas, Thyroid Gland, Parotid glands, Parathyroid glands, Adrenal glands, Sub mandibular glands

A

Exocrine: Goblet cells, Parotid glands, Sub mandibular glands

Endocrine: Thyroid, Parathyroid, Adrenals

Mixed: Pancreas

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80
Q

What is a serous demilune?

A

Artefactual structure squeezed out by conventional fixation

Salivary glands

A gland with this structure produces both serous and mucous secretions, mixed

Mucosal and serosal cells actually aligned in the acinus

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81
Q

What type of epithelium is found in the thyroid gland?

A

Simple cuboidal epithelium

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82
Q

What surfaces do mucosal membranes line? Examples

What cells do they have?

A

Certain internal tubes which open to the exterior

Alimentary tracts

Respiratory tract

Mucus secreting cells to varying degrees

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83
Q

What is the structure of a mucous membrane?

Constitution

A

Epithelium (type depending on site) lining the lumen of a tube

An adjacent layer of connective tissue, the LAMINA PROPRIA

In the alimentary tract, there is a layer of smooth muscle, MUSCULARIS MUCOSAE

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84
Q

What are serous membranes?

What do they envelope? Examples

A

Serous membranes are two part membranes that line certain closed body cavities (do not open to exterior)

They envelope the viscera/organs

Examples

Peritoneum envelopes the abdominal organs

Pericardium envelopes the heat

Pleural sac envelopes the lungs

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85
Q

What is secreted by serosal membranes?

What is the function of this?

What are the two layers of a serosal membrane called?

A

Secretes lubricating fluid

Promotes relatively friction free movement of structures that they surround

Visceral (inside) and parietal (outside)

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86
Q

What does a serosal membrane consist of?

A

Simple squamous epithelium MESOTHELIUM which secretes a watery lubricating fluid

A thin layer of connective tiossue which attaches to epithelium of adjacent epithelium, and carries blood vessels and nerves

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87
Q

What is the gut mesentry?

A

Double layer of peritoneal membrane which supports the small intestine

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88
Q

Describe the layer structure of the alimentary tract

A

Mucosa: epithelium, basement membrane, lamina propria (aggregrates of lymphocytes, Peyers patches, loose connective tissue), muscularis mucosae

Submucosa: connective tissue layer, arteries, veins, nerves

Muscularis externae: circular muscle inside, longitudinal muscle outside, peristaltic waves

Serosa: mesothelium if peritoneal OR Adventitia: loose connective tissue if retroperitoneal (behind)

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89
Q

Describe the layer structure of the oesophagus

A

Epithelium: stratified squamous non-keratinised

Lamina propria: loose connective tissue with blood and lymph vessels, some smooth muscle and immune cells

Muscualris mucosae: smooth muscle thin layer

Submucose: subtending layer of connective tissue with mucus secreting glands

Muscularis externa: circular and longitudinal smooth muscle, peristalsis

Adventitia: thin outermost layer of connective tissue

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90
Q

Describe the layer structure of the stomach?

A

Gastric mucosa: secretes acid, digestive enzymes and gastrin. Simple columnar epithelia for absorption. RUGAE: folds of the gastric mucosa forming longitudinal ridges in an empty stomach.

Muscularis mucosae

Sub mucosa

Muscularis externa: oblique, circular and longitudinal layers of smooth muscle

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91
Q

Describe the layer structure of the jejunum

A

Pilicae circulares: circular folds of mucosa and submucosa that project into the gut lumen.

Jejunal mucosa: epithelia (simple columnar), lamina propria, muscularis mucosae

Submucosa

Muscularis externa: circular and longitudinal smooth muscle

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92
Q

Describe the layer structure of the large intestine/colon

A

Epithelium: simple columnar for absorption

Crypts of lieberkuhn producing lots of mucus and supplying cells to the surface. Absorbs water and electrolytes on the surface.

Structure same as rest of GI tract: mucosa, submucosa, muscularis externae, serosa

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93
Q

What makes up the conducting portions and respiratory portions of the respiratory tract?

A

Conducting: nasal cavity to the bronchioles

Respiratory: Bronchioles to the alveoli

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94
Q

What is the layer structure of the trachea?

A

Epithelium: pseudostratified ciliated

Submucosa: connective tussue with sero mucous glands which decrease as they go closer to the bronchioles

Fibroelastic membrane with trachealis muscle

C shaped Hyaline cartilage: C shaped to prevent oesophageal collapse, also in bronchus but no further.

Adventitia: loose connective tissue.

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95
Q

Describe the layer structure of the bronchus

A

Pseudostratified epithelium

Smooth muscle

Submucosa

Crescent shaped cartilage

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96
Q

Describe the layer structure of a bronchiole

A

Simple columnar/cuboidal/ciliated.

Samller bronchioles are not cilitaed. In terminal bronchioles small sacs extend, lined by ciliated cuboidal epithelium

Smooth muscle

Alveoli: no cartilages because surrounding alveoli keep the lumen open

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97
Q

What are the cell types of the alveoli? What are their functions?

A

One cell thick, purely epithelial

Type 1 cells: squamous, cover 90% of surface area and permit gas exchange with capillaires

Type 2 cells: cuboidal, cover 10% of the surface area. Produce surfactant.

Numeroud macrophages line the alveolar surface, phagocytose particles

Gas exchange across blood air barrier

Alveoli are surrounded by a basketwork of capillaries and elastic fibres

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98
Q

Describe the layer structure of the ureter in the urinary tract

A

Transitional epithelium

Lamina propria: fibroelastic

Muscularis externa: circular

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99
Q

Describe the layer structure of the bladder wall

A

Transitional epithelium, impermeable to urine due to thick plasma membrane and intercellular tight junctions

Smooth muscle in the lamina propria

Muscularis externae, three interwoven layers

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100
Q

Describe the layer structure of the urethra

How long is it in males and females?

A

Transitional epithelium. In penile urethra the epithelium is stratified columnar.

Lamina propria

Muscularis externae, circular and longitudinal

Adventitia

Stellate (star shaped) urethral lumen becomes ovoid as urine passes through

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101
Q

Describe the regenerative capabilites of various glands

A

Glandular cells of the mucous membranes of the digestive, respiratory and urinary tractscontinue to multiple throughout life, cells from the apical surface are continually replaced

Liver, thyroid and pancreatic cells cease to multiply at puberty, but can regenerate in the case of tissue injury

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102
Q

What is neoplasia?

A

A malignant neoplasm derived from glandular epithelium is called an adenocarcinoma

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103
Q

Define the term limit of resolution

A

The minimum distance at which two objects can be distinguished at

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104
Q

Why are electron microscopes capable of finer resolution than light microscopes?

What is the theoretical limit of resolution of light and electron microscopes?

A

The limit of resolution

is proportional to wavelength

Electrons, much shorter wavelength than visible light

Light: 0.2mm

Electron: 0.002nm

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105
Q

What are the main differences between prokaryotic and eukaryotic cells?

A

Prokaryotic: no internal membranes, all processes in one compartment

Eukaryotic: compartmentalised by internal membranes, ordely biochemical processes

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106
Q

Describe the properties and functions of membranes

A

Phospholipid (amphipathic molecules) bilayer

Proteins are freely mobile, fluid mosaic

Some proteins within the membrane are attached to the cytoskeleton

Some proteins are glycosylated, pointing outwards, forms the glycocalyx

FUNCTIONS: intercellualr adhesion, recognition, signal transduction, compartmentalisation, selective permeability, exocytosis and endocytosis

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107
Q

Describe the nucleus

A

Contains DNA, nucleoproteins and RNA

Dense heterochromatin and lucent euchromatin

Inactive: small and dense

Active: large and sparse

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108
Q

Describe the nucleolus

A

Electron dense structure

Site of ribosomal RNA synthesis for ribosome assembley, sub units exported

Disappears in cell division

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109
Q

Describe the nuclear envelope

A

Double layer of membranes

Nuclear pores

Type of special ER, the perinuclear cisterna between inner and outer nuclear membranes, is continuous with the ER

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110
Q

Describe the rough ER

A

Ribosomes on surface

Protein synthesis site

Generates proteins for transport out of cell or to lysosomes

Flattened cisternae

Extensive

Interconnecting membranes, vesicles

Lysosomal enzymes made here, N linked glycosylation, intial

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111
Q

Describe the structure of cilia

A

Nine pairs of peripheral microtubules

Two single central microtubules

Plasmolemma covered extensions of cytoplasm

Move material along the cell surface

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112
Q

Describe the smooth ER

A

No ribosomes

Lipid and steroid synthesis: liver, mammary glands, testis, adrenals

Not as flat as rough ER, less extensive

Intracellular transport

Continous with rough ER enclosing single lumen

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113
Q

Describe the golgi apparatus

A

Stacks of cisternae, cis and trans face

Prioteins from the rough ER bud off and fuse with the convex cis face

Proteins migrate to the concave trans face

Sort, concentrate, package and modify proteins

O linked glycosylation, add mannose 6 phosphate marker for lysosomal enzymes

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114
Q

Describe lysosomes

A

Generated by the Golgi apparatus

Hydrolytic enzymes

pH 5

Highly glycosylated membrane for protection

Diverse in shape

Primary and secondary - phagolysosome

Many found in neutrophils and macrophages

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115
Q

Describe peroxisomes

A

Roughly spherical

Granualr matricx bound by single membrane

Self replicating, no genome

in all cells, especially the liver and kidney

Major sites of o2 utilisation and H2O2 production

Detoxification

Oxidises phenols, alcohols, fomic acid, formaldehyde

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116
Q

Describe mitochondria

A

Double membrane with inner membrane in ditinct folds, cristae

Generation of ATP by oxidative phosphorylation

Main substrates are glucose and fatty acids

Matrix: enzymes and mitochondrial DNA, own genetic info, can divide. Female lineage
Inner membrane is impermeable to small ions

ATP synthase enzymes

Endosymbiosis theory

Many found in the liver and skeletal muscle

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117
Q

Describe the cytoskeleton

A

Maintains and changes cell shape

Structural support for the plasma membrane and organelles

Means of movement inside the cell

Contractiblity in muscles

Locomotor mechanisms for amoeboid movements like lymphocytes, and also for cilia and flagella

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118
Q

Describe microfilaments

A

Part of the cytoskeleton

5nm diameter

Two strings of actin twisted together

Associated with ATP - contractile

Can assemble and dissociate, so is dynamic

Core of actin filaments maintains microvilli

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119
Q

Describe intermediate filaments

A

Part of cytoskeleton

Not dynamic, 10nm diameter

Commonn in nerve and neuroglial cells

Also common in epithelial cells that are made of cytokeratin. Tough supporting meshwork in cytoplasm and atr anchored to plasmamebrane at strong intracellular junctions - desmosomes

Forming nuclear lamina

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120
Q

Describe microtubules

A

Part of cytoskeleton

13 alpha and beta subinits polymerise to form the wall of the hollow microtubules

Originate from the centrosome

Found at sites where structures in crlld are moved

Long hollow cylinders of tubulin, 25nm diameter

9+2 arrangement in cilia and flagella

Attachment proteins can attach to organelles and move them along microtubules

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121
Q

Define the term connective tissue

Explain some functions

A

A tissue of MESODERMAL origin

With three basic components: cells, extracellular fibres and ground substance

If forms a huge continnum throughout the body, linking together muscle, nerve and epithelial tissue, in a strcutural, metabolic and physical way

Its functions include supporting organs, filling spaces between them and forming tendons and ligaments

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122
Q

What are the main functions of connective tissue?

A

Provide substance and form to body and organs

Medium for nutrient and waste diffusion

Attach muscle to bone, and bone to bone

Cushion between tissues and organs

Defend against infection

Aid in injury repair

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123
Q

What are the main resident cell types in connective tissue?

A

Fibroblasts: synthesise and maintain extracellular components. Synthesise collagen, elastin and reticular fibres and ground substance. Fibrocytes are mature and less active cells.

Mesenchymal cells: undifferentiated cells, differentiate into other cells and maintain extracellular materials

Macrophages: tissue histocytes derived from monocytes. Ingest foreign material such as bacteria, dead cells and cell debris. Specific names, in liver KUPFER cells, in CNS MICROGLIAL cells, in bone OSTEOCLASTS.

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124
Q

How do different connective tissue types vary in their composition?

A

Cell type

Abundance and densitry of cells

Constitution of extracellular matrix

Ground substance composition

Fibre type, abundance and arrangement

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125
Q

What are the main visitant cell types in connective tissue?

A

Mast cells: seen near blood vessels containing granules with histamine and heparin. They release phamacologically active molecules.

Plasma cells: derived from lymphocytes.

Fat cells - adipocytes: occur in small clusters or aggregates acting for storage. They store lipids and act as an insulator and shock absorber, cushioning organs and joints.

Leukocytes (WBCs) - derived from blood vessels, responsible for the production of immunocompetent cells

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126
Q

What does the extracellular matrix of connective tissue define?

A

Whether the function is of primary mechanical importance or if it is loose packing material

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127
Q

What are the classes of connective tissue?

A

Embryonic: mesenchyme (gives rise to others) from mesoderm, mucous connective tissue

Connective tissue proper: loose (areolar), dense (regular/irregular)

Specialised: adipose, blood, cartilage, bone, lymphatic tissue, haeemopoietic tissue

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128
Q

What makes up ground substance in connective tissue?

A

Gel like matric which the fibres and cells are embedded in, and the ECF diffuses through it

Core proteins with glycosaminoglycans attached (GAGs)
, proteoglycans and glycoproteins

Hyaluronic acid molecules with many proteoglycan molecules, incterweave with collagen fibrils

Negative charges on GAGs attract water, forming a hydrated gel

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129
Q

What fibres are found in connective tissue, explain a bit about each

A

Collagen: occurs as bundles of non elastic fibres of varied thickness. Lots of different types but most commonly type 1, synthesis is on RER of cells.

Reticular fibrils: type III collagen, thin branching fibres. Delicate network around smooth muscle cells, some epithelial cells, blood vessels, adipocytes and nerve fibres. Also makes the structural framework around organs such as the spleen, liver, bone marrow and lymphoid organs.

Elastic: highly elastic, able to stretch 150% of resting length due to lysine content. Composed of amorphous protein, elastin and surrounded by fibrillin.

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130
Q

Explain types of collagen and its distribution in the body

A

Type I: 90% of collagen, tendons, skin dermis, organ capsules, fribrils, fobres, fibre bundles

Type II: no fibres, hyaline and elastic cartilage

Type III: RETICULIN, fibres around muscle and nerve cells, within lympathic tissues and organs

Type IV: basal lamina of the basement membrane

Most common protein in the body

Tunica adventitia

28 types

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131
Q

Describe the type I collagen fibril structure

A

Periodic banding every 68 nm

Each fibril, staggered collagen molecules

Each molecule is a triple helix of alpha chains, every third amino acid is glycine, 1.5nm wide

Left handed helices into right handed super helix

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132
Q

What do fibroblasts secrete?

A

PROCOLLAGEN

Intamitely associated with collagen fibrils

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133
Q

Describe the properties and distribution of elastin

A

Occurs in most connective tissue to varying degrees

Primary component of elastic fibres, surrounded by microfibrils called fibrillin

Low electron density

Found in the dermis of the skin, tunica media of the arteries, elastic cartilage in the epiglottis, ear pinna and eustachian tube

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134
Q

What condition is caused by abnormal fibrillin?

What are the symptoms of the condition?

A

Marfan’s

Tall, arachnodactyly, joint dislocation, aortic rupture

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135
Q

What are the different types of loose connective tissue and where are they found?

A

Blood

Mucous connective tiissue e.g. Wharton’s jelly

Areolar connective tissue, in skin, submucosa, below periteoneal mesothelium, adventitia of blood vessels, surrounding gland parenchyma

Adipose

Reticular tissue: framework of lymphoid tissues and the liver

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136
Q

What are some examples of dense regular connective tissue?

A

Tendons

Ligaments

Aponeuroses

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137
Q

What are some examples of dense irregular connective tissue?

A

Skin dermis, periosteum, perichondrium, dura mater, capsules, large septa and trabeculae of organs, deep fascia of muscles

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138
Q

What does loose connective tissue do?

What is it made up of?

What happens to it in oedema?

A

Forms the septa and trabeculae that make up the framework inside organs and adipose tissue. Divides glands into lobules.

Loosely packed fibres that are seperated by amorphous ground substance. Lots of hyaluronic acid, sparse collagen

In oedema it becomes greatly distended with ECF

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139
Q

What is mucous connective tissue?

Where is it found?

What it is its composition?

A

Loose connective tissue: Such as Wharton’s Jelly

Only found in the umbilical cord and subdermal CTof the embryo

Made up of large stellate fibroblasts, which fuse with similar adjacent cells. Some macrophages and lymphocytes are present.

The ground substance is soft and jelly like with lots of hyaluronic acid.

Delicate mesh of collagen fibres

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140
Q

What is areolar connective tissue?

Where is it found?

What is its composition?

A

Loose connetive tissue

Found deep under the skin, in the submucosa, below the mesothelium of the peritoneum, associated with adventitia of blood vessels, surrounds the parenchyma of glands

Contains fibroblasts, macrophages and some mast cells

Collagen fibres are the most abundant, but there are some elastic fibres present

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141
Q

What is reticular connective tissue?

What is it made up of?

Where is it found?

A

Loose connective tissue

Made up of type III collagen

Forms the framework of lymphoid tissues and the liver

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142
Q

What is adipose tissue?

What are its properties?

A

Loose connective tissue

Composed mostly of adipocytes, occuring singly or in groups

Between collagen fibres

Nuclei are often compressed against the cell membrane

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143
Q

What is the constitution of dense connetive tissue?

What are some properties?

A

Close packing of fibres

Proportionally fewer cells

Less ground substance

Achieves mecahnical support and transmit forces (tendons)

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144
Q

How are fibre bundles in dense regular connective tissue organised?

A

Fibres in parallel to provide maximum tensile strength

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145
Q

What is the composition of ligaments?

What do they do?

A

Collagen fibres interspersed with fibroblasts

Less regularly arranged than tendons

Elastic ligaments are mainly composed of elastin

Connects bone to bone

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146
Q

What does a tendon do?

What is its composition?

A

Connects muscle to bone

Collagen fibres interspersed withflattened fibroblasts, fascicles (bundles of collagen and fibroblasts), seperated by endotendium (loose CT) and held together by peritendium.

A fibrous sheath surrounds the whole tendon

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147
Q

What are aponeuroses?

A

Flattened tendons

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148
Q

What is the make up of irregular dense connective tissue?

What is its function?

A

Interwoven bundlesof colagen

Small amount of reticular and elastic fibres

Counteracts multidirectional forces to which the tissues are subjected

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149
Q

Where is irregular dense connective tissue found?

A

Dermis of the skin, to withstand multidirectional forces and prevent tearing, elastic fibres allow a degree of stretch

Capsules of some organs

Large septa and trabeculae of many organs

Deep fascia of muscles

Periosteum

Preichondrium

Dura mater

150
Q

What is heparin?

A

An anticoagulant

151
Q

What i histamine and what does it do?s

A

Increases blood vessel wall permeability

Substance attracting neutrophils and eosinophils

Secretions for reactions

152
Q

What are the two types of adipose tissue?

What are the functions of adipose?

A

White: single fat droplet in cells

Brown: seperate droplets

153
Q

What are some disroders of connective tissue?

A

Systemic sclerosis: all organs have excessive accumulation of collage: fibrosis, hardening and functional impairment of skin, digestive tract, muscels, kidneys etc

Keloid: forms scars on skindue to abnormal amounts of collagen

Scurvy: vitamin D deficiencvcy, defective collagen synthesis as cofactor for prolyl hydroxylase. Degeneration of connective tissue, periodontal ligament affected, loosengng of teeth with loss, bleeding gums.

Marfan’s: defect in gene coding for fibrillin, which affects elastic fibres. Large elastic arteries like the aorta rupture due to bulging caused by a smaller lumen.

Ehlers danlos: deficiency in reticular fibres (type III collagen) causing rupture in tissues with high reticulin

154
Q

What are types of variation in the macroscopic structure of human skin?

A

Colour: ehinicity, site (lips/areolae), UV exposure

Hair: site (palms, soles, lips have none), sex (more body hair in men),, age (male baldness, greying), ethinicity (colour, character)

Thickness

Laxity: site, age, UV exposure (injury to dermal collagen/elastin)

Oiliness: puberty, site

155
Q

How do some variation in the macroscopic structure of skin influence the susceptiibility/ manifestations of some skin diseases?

A

VITILIGO (autoimmune depigmentation): less of a problem in fair skin, hardly noticeable. Psychosocial effects in dark skinned as obvious.

ALOPECIA AREATA/TOTALIS (autoimmune hair loss): More impact in women, psychosocial, especially if on scalp.

ACNE: common in puberty

UV INDUCED: more susceptible in fair skinned, to UV induced acute sunburn, freckling, ageing and skin cancer, especially if red hairded and blue eyed. No sunburn in blacks. Low basal cell carcinoma and malignant melanoma in blacks

156
Q

What is the epidermis made of?

What are the different layers of the epidermis?

A

Stratified squamous keratinsied epithelium, made up mainly of keratinocytes and their products

4 layers

Horny layer: stratum corneum

Granular layer: stratum granulosum

Prickle cell layer: stratum spinosum

Basal layer: stratum basale

157
Q

What is the process of keratinocyte differentiation in each of the 4 layers of the epidermis?

A

Keratinocyte mitosis mainly in the basal layer, the daugther cells then move up to the prickle cell layer.

In the prickle cell layer terminal differentiation begins and they lose the ability to divide. Keratinocytes synthesise keratins for strength. Joined by prickle like desmosomes.

In the granular layer they lose their plasma membrane and begin to differentiate into corneocytes. This layer contrains keratohyalin granulesm, which are aggregations of keratins, other fibrous proteins (filaggrin and involucrin) and enzymes which degrade membranes.

The horny layer is made up of layers of flattened corneocytes, highly keratinised squams, they have a major role in skin barrier function.

158
Q

What are keratins?

What are they found in?

A

Heterodimeric fibrous proteins

Epidermis

Hair

Nails

159
Q

What is the transit time of a keratinocyte from the basal layer to the horny layer?

A

30 to 40 days

160
Q

What other epidermal cells are there besides keratinocytes?

What do they do and where are they found?

A

MELANOCYTES: dendritic cells of neural crest origin. Occur at invtervals along the basal layer. DIfficult to see without special stains. They produce melanin, the main skin pigment, more melanin is produced in dark skin.

LANGERHANS CELLS: dendritic cells of bone marrow origin. Scatted throughout the prickle cell layer. Difficult to see without special stain. Specialised capacity to present antigens to T lymphocytes and mediate immune reactions - allergic contact dermatitis

161
Q

What are some disorders of the epidermis?

A

Psoriasis

Akkergic contact dermatitis

Malignant melanoma

Vitiligo

162
Q

Describe psoriasis

A

A disorder of abnormal epidermal growth and differentiation

Common: 1 in 50 people

Cause is unknown, but runs in families

Autoimmune and T cell mediated

Extreme proliferation of epidermal basal layer, causing gross thickening of the prickle cell layer

Production of excessive stratum corneum

Clinically manifests as excessive scaling

Treat with immunosuppresant

Often causes psychosocial issues

163
Q

Describe allergic contact dermatitis

A

Mediated by Langerhans cells

Present antigens to T lymphocytes

Often in response to nickel

164
Q

Describe malignant melanoma

A

Aggressive neoplasm of melanocytes

Retention above basement membrane of epidermis is associated with good prognosis

More penetrating nodular melanomas have a poor prognosis

Common moles are benign growths of melanocytes, sometimes hard to distinguish from melanomas clinically

165
Q

Describe vitiligo

A

Autoimmune attack of melanocytes

Causes depigmentation

Often symmetrical, may be due to neural control down to neural crest embryological origin of melanocytes

Much more visible in dark skin, psychosocial issues

166
Q

What is alopecia areata?

A

Autoimmune attack of hair follicles

167
Q

Describe the dermo-epidermal junction

A

Basement membrane below the basal layer of the epidermis

Best seen with a PAS stain: Period Acid Schiff

InterdigitatingB

asal cells connected by hemidesmosomes

168
Q

What is the structure of the dermis?

A

Dense irregular connective tissue: spiindle shaped fibroblasts. ECM main constituent with mainly type 1 collagens and elastins

Blood vessels: small in the superficial dermis, large in deeper dermis.

Lymph vessels

Mast cells: arround blood vessels, histamine release in allergic reaction, leakage of plasma causing oedema.

Nerves: cutaenous sensory nerves transmit sensation

169
Q

What is the main component of scar tissue?

A

Collagen

170
Q

What causes birthmarks and port wine stains?

A

Birthmarks: malformation of blood vessels

Port wine stain: congenital malformation of blood vessels, always dilated

171
Q

What is the result of damage to collagen and elastin?

A

Solar elastosis

Stretch marks: straie

Scars: keloids

172
Q

What are examples of skin appendages?

A

Hair follicles and sebaceous glands: pilosebaceous unit

Sweat glands: eccrine/apocrine

Nails

173
Q

Describe a pilosebaceous unit

A

Sebaceous gland feeds into the hair follicle, side of hair shaft

Sebaceous glands are a branched type of acinar gland

Holocrine secretion of sebum, cell distintegration

Arrector pili muscle for goosebumps

Large on face, produce lots of sebum, obstructed in acne- infection

174
Q

Describe eccrine and apocrine sweat glands

A

ECCRINE: major sweat glands, found in skin and porduce clear odourless substance of water and NaCl which is reabsorbed in the duct. Active in thermoregulation, controlled by the hypothalamus. Composed of intraepidermal spiral duct, stright dermal portion and coiled acinar portion in the dermis

APOCRINE: large sweat glands, most abundant in axillae (underarms), genital and submammary areas. No function of value, produce odourless protein rich apocrine secretion. Digestion by cutaneous microbes produces odour.

175
Q

What are the main functions of the skin?

A

Barrier function: stratum corneo prevents exogeneous absorption. Much studies as most be overcome by percutaneous absorption of drugs, can be disrupted in disorders like psoriasis (loss of fluid, protein, nutrients, heat. Excessive exogeneous absorption)

Sensation: sensory nerves allow sense of touch, temperature, tissue damage. Disrupted in leprosy (peripheral nerves disorder) and diabetic sensory neuropathy

Thermoregulation: vascular dilation leading to heat loss, contriction retains heat, gives pallor. Failure leads to serious consequences. Eccrine sweating, evaporation.

Psychosexual communication: manipulated as a means of communication and expression, tattoos and piercings

176
Q

What are some properties and functions of cartilage?

A

Non-vascular, strong, pliable

Semi solid, firm, tough jelly

Support of organs, articulating surfaces of bones, greater part of the fetal skeleton

177
Q

Describe the composition of cartilage generally

A

Originates from mesenchyme which differentiates into chrondorblasts, which secrete the matrix

The matrix surround and entraps these cells in lacunae, they are then referred to as chondrocytes

Isogenous clusters of cells

Ground substances made up of type I collagen, glycosaminoglycans, gproteoglycans

Lots of hyaluronic acid for resistance to pressure

No inorganic substances

Mesenchymal cells

178
Q

What usually surrounds cartilage?

What type of connective tissue is this?

What are its layers?

A

Perichondrium

Dense irregular connective tissue

Couterfibrous layer, and inner cellular (CHONDROGENIC) layer with chondroblasts

179
Q

How does cartilage develop in the embryo?

A

Cartilage first appear in the 5th week of development

Embryo skeleton composed of hyaline cartilage, until it is replaced by bone

Hyaline cartilage remains in the epiphyseal growth plates and articular cartilage

180
Q

Describe where hyaline cartilage is found

A

Respiratory passages: C shaped cartilage

Articulating surfaces of long bones

Anterior ends of the ribs

Fetal skeleon

Nose

Epiphyseal growth plates

181
Q

Describe the structure and function of hyaline cartilage

A

Matrix with proteoglycans, hyaluronic acid and type II collagen, bound to fine collagen matrix fibres

Has perichondrium except on articular surfaces

Avascular so must rely on diffusion for nutrient supply

Offers firm and flexible support

Only singular chondrocytes

182
Q

Describe where elastic cartilage is found

A

Ear (pinna)

Eustachian tube

Epiglottis

183
Q

Describe the structure and function of elastic cartilage

A

Matrix is like hyaline cartilage

With collagen and many elastic fibres

Has perichondrium and is avascular

Provides support and maintains the shape of structures

Gives extra flexibility, easier rebound

184
Q

Describe where fibrocartilage is found

A

Intervertebral discs

Menisci of the knee

Pubic symphysis

Portions of the tendons

Temporomandibular joint

Sterno clavicular joint

185
Q

Describe the structure and function of fibrocartilage

A

Matrix like hyaline cartilage

Abundant type I collagen in thick bundles

Gives support and rigidity, strongest cartilage

Very strong and resistant to stretching and compression, weight bearing

Cells in rows in isogenous groups

No perichondrium

186
Q

What is an articular surface?

A

Where bones and joints meet

187
Q

Describe how cartilage grows

A

Appositional growth inwards from the periphery, perichondrium

Deeper in cartilage, interstitial growth from isogenous groups

188
Q

What clinical conditions can arise concerning hyaline cartilage?

A

Can calcify/ossify in old age and disease

Susceptible to degenerative aging process, which is normal but accelerates in aging via the calcification of matrix due to increase in size and number of chondrocytes and cell death

Joint pain can be the result of articular cartilage erosion at the ends of bones (osteoarthritis)

Rheumatoid arthritis occurs when secondary destruction occurss by granulating synovial membrane tissue, autoimmune

189
Q

How does elastic cartilage differ from hyaline cartilage when an individual ages?

A

It does not calcify/ossify in old age

190
Q

What clinical conditions can arise concerning fibrocartilage?

A

Rupture of annulus fibrosus (intevertebral disc capsule) leads to a slipped disc

Tearing of menisci

191
Q

What are the characteristics of bone?

A

Hardest tissue in the bone: can withstand compression, stress and deformation

High vascular and well supplied with lymphatics and nerves (especially sensitive to pain in the periosteum)

Contains cells, fibres and ground substance (calcified matrix)

192
Q

What are the main functions of bone?

A

Support

Protection

Mineral storage (calcium and phosphate)

Haemopoiesis

193
Q

What are the two types of bone?

A

Spongey/cancellous/trabecular/medullar bone

Compact/dense/cortical bone

194
Q

What is the structure of compact bone?

A

Hard, outer bone layer

80% of skeletal mass

Covered and lined by connective tissue, PERIOSTEUM, tough, vascular fibrous layer

Concentric lamellae with central neurovascular Haversian Canal, which communicate via Volkmann’s canals

Concentric circles are osteons

195
Q

What is the structure of spongey bone?

A

Deep, porous, highly vascular

Meshwork of trabeculae filled with marrow, fine bony columns

No haversian or volkmann’s canals

Irregular lamellae remodelled by osteoblasts and osteoclasts

Osteocytes in lamellae

196
Q

What is marrow made up of?

A

Red marrow: RBC synthesis

Yellow marrow: WBC synthesis

Marrow cavity is lined with a thin cellular layer: ENDOSTEUM

197
Q

What is the difference in structure of immature and mature bone?

A

Immature bone: random arrangement of osteocytes - woven bone

Mature bone: osteocytes arranged in concentric lamallae of osteon. Reabsorption cancals parallel with long axis

198
Q

What cells are found in bone?

Describe each type

A

Osteogenitor - OSTEOBLASTS: synthesise the organic components of bone, making bone. They produce the osteoid matrix.

OSTEOCYTES: found in lacunae cavities, maintaining bone. Trapped osteocytes. Slender cytoplasmic process, reach out to adjacent osteocytes via canaliculi. Nutrient transfer, also connect with central Haversian canal.

OSTEOCLASTS: large multinucleated cells from monocytes, which digest bone. Release H+ ions, lysosomal enzymes.

199
Q

Describe the composition and properties of the bone matrix

A

65% inorganic, 35% organic

Calcium hydroxyapatite crystals, calcium phosphate, calcium carbonat

23% Type 1 collagen, 10% water, 2% non collagen proteins

Hardness and rigidity is due to interactions between calcium salts and collagen

Flexibility is due to collagen

200
Q

What is the primary microstructure of bone - woven, immature bone

A

First bone to appear in development and repair, then replaced by mature bone

Collagen fibrils arranged randomly in an interwoven fashion

More cells and less minerals

201
Q

What is the secondary microstructure of bone - lamellar, mature bone

A

Compact dense bone: series of haversian canals, osteon, consisting of concentric lamellae of bone laid around a central canal containin blood vessels

Spaces between Haversian systems are filled with bony lamellae (interstitial lamellae)

Outer surface has extended lamellae (circumferential)

Songey bone: meshwork of bone plates which are filled with marrow,. ALways surrounded by compact bone

202
Q

Briefly explain endochondral ossification

A

Cartilage to bone

Cartilage is reabsorbeds and replaced with bone

Begins at the primary centre in the diaphysis

Later at each end at the seconday centre in the epiphyses

Growth in length is at the epiphyseal growth plates

203
Q

Briefly explain how loose connective tissue or mesenchyme becomes bone

A

Intramembranous ossification

Bone begins as highly vascularised loose connective tissue

Mesenchymal cells differentiate to osteoblasts, surrounded by collagen fibres and ground substance

Secrete uncalcified osteoid and then become osteocytes

204
Q

Briefly explain how bone is remodelled and repaired

A

ACtions of osteoblasts and osteoclasts

Release and incorporation of calcium into and from the matrix

205
Q

what is a fracture?

A

Bleeding from multiple bleeding blood vesselsHa

emotoma between broken bone ends

206
Q

Describe the cellular processes involved in bone repair following a fracture

A

Bone breaks, bone matrix is destroyed and bone cells adjoining the fracture will die
. Blood vessels in periosteum and bone break.

Haemtoma forms with fibrous tissue (PRE CALLUS or PRO CALLUS if periosteum is intact). Inflammatory cells invade to form this.

New blood vessels into haemotoma, collagen spans break, hyaline cartilage forms.

Osteoblsats start to reconstruct spngey bone, OSTEOCALLUS. Calcified to primary then secondary bone. New cancellous bone formed for about two months

Bone remodelled via tendons, mechanical stress. Osteoclasts. Mature bone forms

Bone heals without forming a scar

207
Q

Describe 5 steps in healing of a fracture

A

Break

Haemotoma PRE/PRO CALLUS

Cartilage callus

Primary Bone

Secondary Bone

208
Q

What are the three types of bone grafts used from bone banks?

A

AUTOGRAFT: donor is recipient, most successful

HOMOGRAFT: donor is different human, may be rejected as foreign

HETEROGRAFT: donor is of a different species, least successfulm although calf bone loses antigenicity with refridgeration

209
Q

What are the two types of ossification?

Briefly explain the difference

A

Endochondral: from cartilage

Intramembranous: from mesenchyme or loose connective tissue sheet

210
Q

Describe endochondral ossification

A

Bone formation in hyaline cartilage model, which is reabsorbed and replaced by bone = mineralised

Most bones formed in this way, long bones such as femur and humerus

STEPS: initial cartilage model, collar of periosteal bone in shaft

Central cartilage in diaphyses calcifies, nuterient artery penetrates, osteogenic cells. Primary ossification centre

medulla to cancellous bone. Secondary ossification centre at the epiphyses.

Epiphyses ossify and growth plates move further apart, increased length

Growth in diameter by depostion of bone at periphery of shaft, external modification by osteoblasts to create narrow diaphysis

Epiphyseal growth plates replaced by bone when growth stops, hyaline cartilage at articular surface

211
Q

Where does intramembranous ossification occur?

A

Within condensations of mesenchyme

Flat bones: skull (parietal, occipital, temporal, frontal), maxilla, mandible, pelvis, clavicle

Also thickens long bone

212
Q

Describe the process of intramembranous ossification

A

Bone development starts in highly vascularised connective tissue e.g. flat skull bones

Focus of activity is primary ossification centre

Mesenchymal cells differentiate into osteoblasts, surrounded by collagen fibres and ground substance

Osteoblasts secrete osteoid which later calcifieds

Osteoblasts become osteocytes, embedded in osteoidMineral depostis in trabeculae radiate outwards from POC

213
Q

How is compact bone formed?

A

Initially spongey bone is formed

Later transformed to compact

Structure changes constantly by remoedelling

214
Q

Describe osteogenesis imperfecta (brittle bones)

A

Group of rare genetic disorders, affecting synthesis of type I collagen by osteoblasts and fibroblasts

Weaknesses in structure which rely on collagen for strength: sclearae, skin, tendons, ears, skeleton, teeth, joints

Various types: one of which is lethal before birth.

Multiple fractures, bone deformities due to weak callus, bowing of bones, thin bones, some have blue sclearae

Medicolegal importance as multiple fractures can be confused with deliberate injury = abuse

215
Q

Decribe osteoporosis

A

Loss of bone mass as age increases, reduced so there is a increased risk of fracture, as no longer provides adequate mechanical support

Osteoclasts> osteoblasts. Inadequate filling of osteoclasts resorption bays

Risk areas: neck of femur, vertebral column, distal radius

2 types: Type 1 post menopausal due to loss of osteoclast inhibition by oestrogen. Type 2 senile, after age 70, lss of osteoblast function

Risk factors: insufficient calcium intake, insufficient vitamin D, lack of physical activity, cigarette smoking, being female, genetic, blacks have high bone mass peak

216
Q

Describe the consequences of vitamin D and calcium deficiency on bone

A

Needed for normal ossification, promotes mineralisation of bone

Rickets in children: bone matrix does not calcify normally, epiphyseal plate distorted by strains of body weight, bones grow slowly and become deformed. Pliable osteoid, bendy bones, fractures. Bowing of femur, enlarged chostochondral rib junctions, bossing of skull.

Osteomalacia in adults: softening of bones. Deficient calcifcation of recently formed bone, partial decalcification of older matrix, causing fragility anf increased risk of fractures. Bone pain, back ache, muscle weakness

217
Q

Explain the importance of vitamin D in normal bone development

A

Both dietary and skin synthesised, essential for normal ossification

As involved in calcium and phosphate absorption in small intestine

In its absence, bone is poorly mineralised, a pliable matrix called osteoid (uncalcified, secreted by osteoblasts)

Affected bones can’t support weight and bend.

Common cause of osteomalacia

218
Q

Hoow can osteomalacia be prevented?

A

Adequate intake of calcium, vitamin D and phosphate

Adequate sun exposure (especially in dark skinned individuals)

219
Q

Outline the cause and features of achondroplasia

A

Congential and often hereditary skeletal disorder, caused by failure of proliferation and column formation of epiphyseal cartilage cells

Defect in endochondral bone formation impirs longitudinal growth of the tubular bones, short limbs

Skull unaffected as formed by intramembranous ossification

Autosomal dominant, gain of function in fibroblast growth factor, increased proliferation of chondrocytes in growth plates, less matrix

Epiphyseal growth plates are thin, few cells in the proliferating zone, hypertrophic cartilge cells form irregular columsn, zone of provisional calcified cartilage is smalll and does not provide adequate scaffolding for bone matrix depostion by metaphyseal osteoblasts

220
Q

What is the effect of growth hormone on bone??

Lack and excess

A

Lack of GH affects epiphyseal cartilage causing pituitary dwarfism if before puberty. After, no effect, no growth plates in epiphyses

Excess before pubery, excess long bone growth, gigantism. In an adult, periosteal growth, acromegaly. Usu

ally due to benign anterior pituitary tumour

221
Q

What is the effect of sex hormones on bone?

A

Influence time and appearance of ossification centres

Precocious sexual maturity close epiphyseal growth plates prematurely retarding bone growth

Sex hormone deficiencies delay plate closure causing tall statuere, later puberty.

Androgens and oestrogens influence pubertal growth spurt.

222
Q

What is the effect of thyroid hormone deficiency on bone?

A

In newborn hypothyroidism causes cretinism

Stunted physical and mental development

Short stature

223
Q

What are the three types of muscle?

A

Striated: cardiac and skeletal

Non striated: smooth

224
Q

What is the banding structure of muscle?

A

MHAZI

M line is in the H band, which is in the A band

Z line is in the I band

225
Q

Describe actin and myosin simply, and where they are

A

Thin filament is ACTIN, mainly in I band

Thick filament is MYOSIN, mainly in A band so H and M too

226
Q

What is a sarcomere?

A

Z line to Z line distance

227
Q

What forms the thin filaments in skeletal and cardiac muscle?

A

Actin and tropomyosin molecules wrap around each other

Troponin complex attached to each tropomyosin molecule, covering the binding sites for the myosin filament

TnI binds to Actin

TnC binds to clcium

TnT binds to tropomyosin

228
Q

What makes up the thick filament?

A

Many myosin molecules

Heads protrude at opposite endsCent

Centre of sarcomere is devoid of heads

229
Q

Describe the sliding filament theory of muscle contraction

A

A band length is constand

Length of the H and I bands decrease

Actin filaments move in to overlap with myosin

230
Q

Describe the sarcotubular system of skeletal muscle

A

AI junction, one transverse (T) tubule

T tubule extends from sarcolemma

2 terminal cisternae per tubule, TRIAD

231
Q

Explain the mechanism of the sliding filament model of muscle contraction

A

Troposmyosin blocks actin binding site for myosin. Calcium ions bind to TnC, moving tropomyosin away, allowing myosin heads to bind actin and begin contraction.

  1. Myosin head is tightly bound to actin in rigor conformation. Lack of ATP.
  2. ATP binds to the myosin head causing it to uncouple from actin.
  3. Hydrolysis of ATP causes uncoupled myosin head to bend and advance 5nm
  4. Myosin head binds weakly to actin releasing Pi, causing power stroke. in which myosin head returns to former position. Actin moves to M line, binds to myosin head tightly again.

Myosin heads attach at different times causing movement

232
Q

Describe the mechanism of muscle innervatio and excitation contraction coupling

A

ACtion potential at presynaptic neron terminal, calcium infklux from ECF to ICF

Influx causes presynaptic vesicles to release ACh in synaptic cleft

ACh binds to nicotinic acetyl choline receptors bound to motor end plate, ligand gated ion channels open allowing sodium ions to diffuse in, depolarising the sarcolemma, spreading to the T tubules

Voltage senor proteins of T tubule membrane change their conformation. Gated calcium ion release channels in adjacent terminal cisternae of SR are activated by this

Rapid release of calcium into sarcoplasm

Calcium binds to TnC, initiating the contraction cycle

Calcium ions return to the terminal cisternae of the SR

233
Q

Describe the structure of skeletal mucl from the epimysium to the muscle fibres

A

Epimysium: thick connective tisssue around muscle, sheath

Perimysium: around fascicles, a group of fibres, carries nerves and blood vessels

Endomysium: surrounds individual muscle fibresIn

Interdigitation of muscle fibres with surrounding connective tissue such as tendon at myotendonous junction - sarcolemma always between collagen bundles and muscle fibres microfilaments

234
Q

What connective tissue is associated with skeletal muscle?

A

Tendons connect muscle to bone

Aponeuroses: muscle to bone or adjoining structures, flat and broad

Layers of dense connective tissue bind muscles into functional groups, DEEP FASCIA. Contain large blood vessels, nerves, and some fat.

235
Q

What are muscle fibres (cells) composed of?

A

Myofibrils, which are composed of myofilaments, actin and myosin

Sarcolemma

Mitochondria

Nucleus

236
Q

How do the A band and I band of skeletal muscle appear under a microscope?

A

A is dark

I is light

237
Q

How are skeletal muscle cells formed?

A

Derived from the mesoderm, from multipotent myogenic stem cells

Give rise to myoblasts, which fuse to form a primary myotube, a chain of multiple central nuclei

The nuclei are displaced to the cell periphery by myosin and actin filaments

238
Q

Describe the features of red muscle

A

Would fnid lots in a marathon runner

Smaller

Rich vascularisation

Rich myoglobin

Numerous mitochondria

Slow, weak contraction

SLow fatigue

Rich in oxidative enzymes, poor in ATP ase

Few neuromuscular junctions

239
Q

Describe the features of white muscle

A

Wider

Poor vascularisation

Little myoglobin

Few mitochondria

Fast, strong contraction

Rapid fatigue

Poor in oxidative enzymes, rich in ATPase

More NM junctions

240
Q

Describe the main features of skeletal muscle?

A

Long fibres, cylindrical

Many peripheral nuclei

Fascicle bundles, tendon connect to bone

Somatic neuronal voluntary control

Rapid forceful contraction

Striated

241
Q

Describe the main features of cardiac muscle

A

Short branched cylindrical fibres

Single central nucleus, 1 or 2

Striated

Adherens type junctions join cells end to end, anchor cells and provide achorage for actin

Gap junctions for electrical coupling with adjacent cells, intercalated discs, Z bands

Intrinsic rhythm, involuntary, autonomic

Life long variable rhythm

T tubules on Z disc

SR less developed, diad not triad

242
Q

Descibr the main features of smooth muscle cells

A

Spindle shaped with tapering ends

Central single nucleus

Gap and desmosome type junctions

Not striated, no sarcomeres or T tubules

Contraction still actin myosin based

Slower more sustained contraction, longer

Involuntary, autonomic, local stimuli

Form sheets, bundles or layers

Thick and thin filmaents are arranged diagonally, spiralling down the long axis for a twisting contraction

243
Q

What is the term to describe the spontaneous and rhythmic contractile capabilites of the heart?

What sort of cells transmit action potentials from the atrioventricular node to the ventrical walls?

A

Myogenic

Purkinje fibres

244
Q

Describe the microscopic structure of a cardiac muscle cell

A

T tubules on Z disc

Sarcoplasmic reticulum less developed

Diad not triad

245
Q

Describe the conduction of the action potential in cariac muscle

Describe how purkinje fibres are involved

A

Action potential in sino atrial node

To atrioventricular node

Carried to ventricles by purkinje fibres by rapid conduction, enabling the ventricles to contract in a synchronous manner

246
Q
A
247
Q

Describe the structure of purkinje fibres

A

Large cells, modified monocytes

ABundant glycogen

Sparse myofilaments

Extensive gap junction sites

248
Q

Compare the regenerative capabilities of the three muscle types

A

SKELETAL: cells can not divide by tissue can regenetate by mitotic activity of satellite cells, so that hyperplasia follow muscle injury. Satellite cells fused with existing muscle cells to increase mass, hypertrophy. Gross damage repaired by connective tissue leaving a scar. If nerve or blood supply is interrupted, muscle fibres degenerate and are replaced by fibrous tissues

CARDIAC: incapable of regeneration, following damage, fibroblasts invade and divide, laying down scar tissue

SMOOTH MUSCLE: reatin mitotic capabilities, can form new smooth muscle cells. Evident in pregnant uterus, muscle wall becomes thicker with hypertrophy and hyperplasia of individual cells

249
Q

Where is smooth muscle found?

How is it innervated?

A

Found in contractile walls of cavities, passageways, vasculature, gut, airways, genitourinary, uterus, ducts, glands, iris

Innervated by autonomic, unmyelinated nerves

250
Q

What is the clinical significance of smooth muscle?

How can smooth muscle be modified for different functions?

A

Hypertension, dysmenorrhoea, asthma, atherosclerosis

Modified in myoepithelial cells in acini of gland, myofibroblasts producing collagen and contract

251
Q

Explain the use of troponin assays

A

TnI and TnT are useful markers

Cardiac ischaemi

Release in one hour

Must measure within 20 hours

Smallest change in troponin is MI

252
Q

How often are contractile proteins replaced in skeletal muscle?

A

Every 2 weeks

253
Q

What is atrophy?

What problems can it cause and how does it arise?

A

Wasting of muscle due to lack of use, in the aged, loss of nerve supply following injury. Muscle cell shrinks in size.

Disuse atrophy: maintenance requires frequent movement against resistance or fibres shrink and weaken

Loss of protein so reduced fibre diameter, loss of power

More atrophy with age

Destruction is greater than replacement of myofibrils

Can also be caused by denervation

254
Q

Describe how atrophy occurs with age

A

Above the age of 30, muscle mass decreases

50% loss of muscle by age 80

Important in temperature regulation, so loss of non shivering thermogenesis

255
Q

What are the general functions of skeletal muscle?

A

Movement

Posture

Stability of joints

Heat generation

256
Q

How does muscle atrophy occur due to denervation?

A

Muscle no longer receives contractile signals which are required to maintain normal size

Indications of lower motorneurone lesions include: weakness, flaccidity, muscle atrophy with fasciculatations (spontaenous twitiching of small groups of muscle fibres), and degeneration of muscle fibres 10 to 14 days after injury.

Reinnervation within 3 months for good recovery, completely lost after 2 years

Muscle fibres are replaced with fibrous and fatty tissue which requires daily stretching as it causes shortening

257
Q

What occurs in hypertrophy of skeletal muscle?

A

Replacement of fibrils is greater than destruction

Increase in muscle mass from work performed against load leads to

More contractile proteins, increase in fibre diameter

Metabolic changes: enzyme activity for glycolysis, mitochondria, stored glycogen, blood flow

Increased muscle length, addition of sarcomeres

258
Q

Outline the physiology of the neuromuscular junction

A

Motor neurone synaptic knob releases acetyle choline into synapse as a result of calcium influx

ACh binds to nicotinic receptor on folded end plate region

Sodium ion channel opens, action potential down T tubules

Causes calcium ion release from SR, muscle contraction

Only 25% of ACh receptors need filling for a contraction

259
Q

What is ACh terminated by?

At high motor neurone firing rates, what happens?

A

ACh is terminated by acetylcholinesterase

ACh release decreases at high neurone firing rates

260
Q

Describe the pathophysiology of myasthenia gravis

A

Automimmune destruction of the end plate ACh receptors

and loss of end plate junctional folds

Widening of the synaptic cleft

261
Q

Describe the symptoms of myasthenia gravis and when the crisis point occurs

A

Fatigability and sudden falling due to reduced ACh release, muscle relaxes

Drooping eyelids

Double vision

Affected by general state of health and emotion

Test: hold out arm when sat down, see if it collapses quickly

Crisis when it affects respiratory muscles

262
Q

How is myasthenia gravis treated?

A

Acetylcholinesterase inhibitors

Stops it beraking down ACh

Neostigmine, physostigmine

Also can place eyes on the eyelids to decrease acetylcholinesterase activity

263
Q

How is neuromuscular transmission affected in botulism?

A

Toxins block ACh release

Clostridium botulinium bacteria in soill

Can not breath properly

Used in botox

264
Q

How is neuromuscular transmission affected in organophosphate poisoning?

A

Inhibits acetylcholinesterase irreversibly

ACh remains in the receptors

Muscle stays contracted

265
Q

What are muscular dystrophies?

A

Genetic disorders group

Progressive muscle wasting and weakness

Failure of body to produce proteins, or not enough, in the muscle cell membrane

266
Q

What is dystrophin?

A

Long rod shaped protein

Anchors sarcolemma to actin and myosin fibrils

267
Q

Describe the pathophysiology of duchenne muscular dystrophy

A

Complete absence of dystrophin

Actin not anchored to sarcolemma, so fibres tear themselves apart on contraction

Creatine kinase liberated into serum

Calcium enters cell causing necrosis

Pseudohypertrophy (swelling), before fat and connective tissue replace muscle fibres

268
Q

Describe the symptoms of duchenne muscular dystrophy

Describe some possible treatments

A

Early onset, Gower’s sign, push hands on knees to push strength up

Slow, late walking, falls

Contractures: stiff joints. Imbalance between agonist and antagonist muscles

Steroids: prednisolone, helps to build up muscle fibres

Genetic reseatch, to make dystrophin with stem cells, gene therapy.

Ataluren drug trials, ribosomal interaction to make dystrophin

269
Q

Give examples of myopathies

A

Inflammatory: poliomyostitis (chronic inflammation, viral/autoimmune), myalgia (muscle pain) and influenza

Electrolyte imbalances: cramps, diuretic therapy (hypokalaemia)

Thyrotoxicosis: increased BMR and protein catabolism

Hypoparathyroidism: hypocalcaemia causing tetany

Channelopathies: malignant hyperthermia

270
Q

Describe the pathophysiology of malignant hyperthermia

A

Rare, autosomal dominant condition, life threatening reaction to some general anaesthetics

Volatile anaesthetic agens and NM blocking agent succinylcholine, which is a non competitive inhibitor of ACh on muscle nicotinic receptors. It is degraded by butyrlcholinesterase much more slowly than ACh by acetylcholinersterase

Uncontrolled increase in calcium release in the muscle, and uncontrolled increase in oxidative metabolism, overwhelming body’s capactiy to supply o”, remove co2 and regulate body metabolism. Heat production, circulatory collapse and death.

Can be treated with dantrolene a muscle relaxant

271
Q

How are nerve fibres structured outside the CNS?

A

Bound together by connective tissue
To form the peripheral nerves

272
Q

What are fibres that carry impulses towards the CNS called?

A

Afferent or sensory fibres

273
Q

What are fibres that carry impulses away from the CNS called?

A

Motor or efferent fibres

274
Q

What is an entire nerve sheathed by?

A

Epineurium

275
Q

What is a nerve fascicle ensheathed by?

And what travels in this? What is the clinical relevance?

A

Perineurium

Point where blood vessels travel within the nerve

Potential malignancy transport

276
Q

What is a single nerve axon ensheathed by?

A

Endoneurium

277
Q

Describe the structure of a neuron

A

All neurones have one axon

Cell body with or without dendrites

Myelinated or unmyelinated

Axonal terminal

278
Q

Describe the basic neuron types

A

Multi polar: multiple dendrites, one axon, motoneuron

Bipolar: one dendrite and one axon, interneuron, rare, in retina of eye

Unipolar/ pseudounipolar: no dendrites, one axon, sensory neuron

279
Q

Describe how peripheral nerves are myelinated

A

Sleeve of Schwanna cells, the neurolemma

Wound in several concentric layers

Discntionous, with gaps called nodes of ranvier

To increase the speed of conduction, correlates to level of axonal myelination

280
Q

How are myelin sheaths histologically processed?

A

Myelin is mainly lipid, so poorly preserved in routin processing techniques

Special fixatives and stains

Osmium tetroxide

281
Q

How are axons myelinated in the CNS?

A

Glial cells called oligodendrocytes

Produce and maintain the myelin coating

Covering up to 250 axons

282
Q

Describe the myelination in the autonomic and somatic nervous systems

A

Autonomic (involuntary): myelinated (CNS) and unmyelinated (PNS) neurones

Somatic (voluntary): all myelinated neurones for faster action potentials

283
Q

What neurotransmitters do excitatory neurones use?

What to they do to the next neuron?

A

Glutatmate/aspartate

Depolarise next neuron

284
Q

What neurotransmitters to inhibitroy neurones use?

What do they do to the following neuron?

A

Glycine or GABA (g amino butyric acid)

hyperpolarises the next neuron

285
Q

What causes neurotranmitters to be released?

A

DepoAddlarisation of the axon terminal

Influx of calcium ions

Presynaptic vesicles release contents

286
Q

What is the neuron proximal to the synapse called?

What is the neuron distal to the synapse called?

A

Pre synaptic is proximal

Post synaptic is distal

287
Q

How does demyelination cause a slowing of conduction veloctiry within a nerve?

A

Impulse has further to travel as saltatory propagation is inhibitied, slower response

EG Multiple Sclerosis

288
Q

Describe multiple sclerosis

A

The myelin sheath is destructively removed from the axon and replaced by scar tissueOligodendrocytes and axons can also be damaged

Condction velocity and saltatory propagation is impaired

Scar tissue does not permit conduiction therefore the axon is useless

289
Q

Describe the structure of a nerve cell body (perikaryon)

A

Engine of neurone, 4 to 120 micrometres in diameter

Varies in shape, may have dendrites, axonal hillock last site of summation

Nissl substane, aggregration of RER for protein synthesis

Golgi packages neurotransmitters into vesicle

290
Q

Describe dendrites

A

Specialisations to increase cell body surface area

From cell body, proximal, further away, distal

Dendritic tree

Dendritic spines for learning experiences, Down’s can’t express

Does not matter where the signal is received, it is maintained

291
Q

Describe the variety of connections between neurones

A

Lightly (one cell to one cell)

to heavily (one nerve cell to thousands)

292
Q

How many pairs of spinal/segmental nerves are there?

A

31

293
Q

What s the nervous system made up of?

What are nerves from the brain called?

A

Brain, spinal cord and nerves

Cranial nerves

294
Q

How is the central nervous system encased?

A

3 layers of connective tissue

Meninges

295
Q

What are the 3 meninges, from outside to inside?

A

Dura Mater

Arachnoid Mater

Pia Mater

296
Q

What is CSF?

A

Cerebrospinal fluid

Equivalent to arterial and venous fluid of the CNS

Formed by choroid plexus of arteries

Butrition and oxygenation of CNS neurones, carries away metabolites

297
Q

What are the clinical implications of too much CSF?

A

Brain death

High hydrostatic pressure

298
Q

What are the leptomeninges?

A

Arachnoid mater and pia mater

299
Q

What is the sub arachnoid space?

A

The space between the pia mater and arachnoid mater

300
Q

What is within the subarachnoid space?

How does it arise?

A

Cerebral spial fluid flows here, and blood vessels

Dilations occur floowing failures of arachnoid mater to follow brain furrows, and adher to pia mater

Dilations are CSF cisterns

Important clinically to confine brain bleeds

301
Q

What are the two major cell types in the CNS?

A

Neurons, functional 10%

Glial cells, make sure neurones thrive, 90%

302
Q

What is the function of glial cells generally?

A

Support neurones, help maintain homeostasis, form myelin, insulate neurones, destroy pathogens

303
Q

What are various glial cell types?

What are their functions?

Where are they found?

A

Astrocytes: blood brain barrier, assist in transfer of nutrients and waste, in the CNS

Oligodendrocytes: myeliantion, up to 250 axons per cell, in CNS

Microglia: immune and inflammatory reactions, macrophages, in CNS and PNS

Schwann cell: myelination, many cells per axon, in PNS

Satellite cells: physical support of peripheral neurones (afferent and efferent), PNS

304
Q

What are the types of input summation?

A

+ excitatory

  • inhibitory

SPATIAL: summated with respect to spatial location on cell

Temporal: summated with respect to time of arrival on cell body

305
Q

What are the functions of an axon?

A

Summates all inputs to the neuron

Initiates action potentials

Conducts action potentialsm away from the cell body to the terminals

Depolarisation of terminals leads to release of neurotransmitters

Communicates with follower cell

306
Q

What are the functional classes of neurone? Explain each

A

Sensory, pseudounipolar: receptros that transduce to electrical impulses
. Conduct to cell body, then spinal cord/brain
, some are fastest conducting neurones in body, AFFERENTS

Motor, multipolar: carry out brain instructions to move muscles, conduct from brain to muscle, largest neurones, integrate large array of inputs to one output, clinically very important. EFFERENTS

Inter, multipolar: 95% of nervous system, smallest, wholly in CNS, info relays between sensory and motor neurones, probably most complex neurones in the body. RELAYS

307
Q

Describe the cell membranes of neurones

A

Bilipid, selectively permeable to certain ionic species.

Development of ionic concentration gradients between inside and outside of cells.

ELECTROCHEMICAL GRADIENT

Makes the neurone electrically charged

308
Q

How are ion channels gates on neurones?

A

Voltage gates: opened or closed by voltage changes

Others opened by nurotransmitters: ligand gated

309
Q

What value is the neuron hyperpolarised at? resting potential

A

-70mV

310
Q

Describe the charges of the neuron at rest

A

Net negartive inside, net negative outside

Active transport of Na+/K+ pumps

More sodium out, potassium in 3:2, potassium can get back out, sodium can’t get back in

311
Q

Describe how an action potential is generated?

A

Stimulus above threshold -55mV, causes Na+ channels to open, Na+ flows back in, membrane is depolarised, local area positive

Depolarisation moves along membrane

After actional potential, K+ channels open, flow out and restore the resting potential

Goes too far: refractory period

312
Q

What is a ganglion?

A

Accumulation of nerve cell bodies outside the CNS

Afferent cell bodies are in the spinal or cerebral ganglia in the dorsal root of spinal nerves

313
Q

What is the autonomic nervous system?

A

The involuntary nervous system

314
Q

What are the two main divisions of the autonomic nervous system?

A

Sympathetic

Parasympathetic

315
Q

TheANS is comprised of a series of how many neurones?

Describe

A

Series of 2 neurone, pre-ganglionic and post-ganglionic

1 cell has a cell body in the CNS, the other cell has a cell body in the PNS

316
Q

What to ANS neurones exert actions on?

A

Viscera

Smooth muscle

Secretory glands

317
Q

What is grey matter?

What is white matter?

What is in the central canal?

What is used to stain a TS spinal cord?

A

Grey matter: neuronal cell bodies

White matter: neuronal axons

CSF in the central canal

Cresyl violet stain

318
Q

In the CNS, what is the name for collections of:

Neuronal cell bodies?

Neuronal axons?

A

Nuclei

Fibre tracts

319
Q

In the PNS, what is the name for collections of:

Neuronal cell bodies?

Neuronal axons?

A

Ganglia

Nerves

320
Q

How is the nervous system divided into different levels and areas?

A

CNS and PNS

to Afferent and Efferent

Efferent to Somatic and Autonomic

Autonomic to Sympathetic, Parasympathetic and Enteric

321
Q

Describe somatic efferents

A

Voluntary

Simplest possible layout

1 neurone carries output, terminates directly on effector organs

Activate when needed, otherwise inactive

Efferents undeveloped at birth, fully developed at puberty

322
Q

What are the functions of the autonomic nervous system?

A

Fundamental life functions, non stop

Balance of opposing systems, sympathetic and parasympathetic

Maintains constant homeostasis

Promotes excretory mechanisms intermittently

323
Q

Describe autonomic innervation

A

Most innervated by ANS dually, PNS and SNS

Dominance of each depends

Exception: sweat = SNS only

324
Q

What happens when the sympathetic or parasympathetic nervous systems are overactive?

A

SNS overactive: constriction of blood vessels (oreserve heat)
, shortage of substrate to body tissues

PNS overactive: dilated blood vessels, shortage of substrate to brain

325
Q

Describe CNS and PNS neurones in the autonomic nervouse system

A

CNS: pre-ganglionic, myelinated, white rami communicantes

PNS: post-ganglionic, not myelinated, Grey rami communicantes

326
Q

What is the main function of the sympathetic nervous system?

A

Involved in the fight/flight/fright response

Expressed mainly in stress situations

Diversion of blood to muscles and heart, increase in heart rate, increase in blood pressure, reduced blood floow to GIT and skin, pale, hyperventilation.

327
Q

Describe the outflow of the sympathetic nervous system

A

Thoraco-Lumbar

Nerve fibres have cell bodies in all 12 thoracic sections, and first 2 lumbar sections

Dorsal, LATERAL and ventral horns in TS spinal cord

328
Q

Describe the two nerve fibres of the sympathic nervous system and their synapsing

A

Short pre ganglionic, long post ganglionic

Paravertabral chain of ganglia along sympathetic trunk, parallel to vertebrae, skull to sacrum

May synapse at same levels as origin (paravertebral origin)

May synapse a different level to origin

May not synapse in the paravertebral chain (splanchnic nerves)

329
Q

Describe the neurotransmitters and receptors in the sympathetic nervous system

A

Preganglionic neurones are CHOLINERGENIC (Acetylcholine)

So post ganglionic receptors are NICOTINIC

Post ganglionic receptors are NORADRENERGENIC (noradrenaline)

Two classes of adrenoreceptors: alpha 1 and 2, and b 1 and 2

Exceptions: some synapses are cholinergenic, perspiration and ejaculation pathways

330
Q

In the ejaculation pathway, which division of the ANS is responsible for

erection?

ejaculation?

A

Erection: Parasympathetic POINT

Ejaculation: Sympathetic SHOOT

331
Q

What are the main functions of the parasympathetic nervous system?

A

BASAL, relaxation, calm

Reduced heart rate and force of contraction

Promotes digetion

Promotes bodily functions such as bladder emptying

Promotes sleep

332
Q

Describe the outflow of the parasympathetic nervous system

A

Cranio sacral outflow

333
Q

Describe the two nerve fibres of the parasympathetic nervous system

A

Long pre ganglionic

Short post ganglionic

Post ganglionic neurones in walls of effector organs

334
Q

Describe the neurotransmitters and receptors in the parasympathetic nervous system

A

Pre ganglionic neurones are CHOLINERGENIC (acetyl choline)

Post ganglionic receptors are NICOTINIC

Post ganglionic neurones are CHOLINERGENIC

Effector organs are MUSCARINIC

335
Q

How can neurotransmitters be exploited in the therapeutic domain?

A

Agonist (triggers response) and antagonists (block agonists)

Beta blockers in heart stop sympathetic stimulation

336
Q

What are blood cells initially produced by in the foetus?

A

Mesoderm of the yolk sac

Liver

Spleen

Bone marrow

337
Q

What is haemopoeisis?

A

The production of red and white blood cells, and platelets

338
Q

Describe the process of haemopoeisis

A

PROLIFERATION:stem cell divides into 2, one replaces the original step cell (self renewal) and the other cell differentiates

DIFFERENTIATION: Haemopoetic progenitor will first differentiate to form either a myeloid blast (RBC, WBC, platelets) or a lymphoid blast (immunoresponse cells)

The progenitor will differentiate into a certain cell type under the influence of a particular cytokine

339
Q

What is a cytokine?

Give some examples

A

A hormone, signalling molecule

Some types cause differentiation of blood cells

Erythropoietin: RBCs when pO2 is low

Thrombopoeitin: platelets

G-CSF, GMCSF, IL-6: colony stimulating factors

340
Q

How many types of white blood cell are there?

Where do they circulate?

A

5 types

Blood and lymphatic systems

341
Q

Where do T cells mature?

A

Thymus

342
Q

Describe Neutrophils

A

Multilobed nucleus, small granules in cytoplasm (polymorphonuclear granulocyte)

Most common circulating WBCs, inactive in circulation, 10 hour lifespan

Migrate out to site of infection CHEMOTAXIS

PHAGOCYTOSIS

G-CSF (granulocyte CSF) increases production

343
Q

Describe eosinophils

A

Bi lobed nucleus, large granules (polymorphonuclear granulocytes)

PHAGOCYTOSIS, of antigen antibody complexes, releases cytotoxic particles

Hypersensitivity reactions

Lifespan 8 to 12 days

Migration to serosa

344
Q

Describe basophils

A

Quite rare, bi or tri lobed nucleus, dense granules, polymorphonuclear granulocytes

Mediate acute inflammatory reactions with histamin and heparin: oedema

Also hyaluronic acid and seratonin

Half life 2.5 days

345
Q

Describe monocytes

A

Large kidney shaped single nucleus, mononuclear cells, no granules

Migrate to tissues to become macrophages

PHAGOCYTOSIS, interact with T cells, CHEMOTAXIS

DIAPEDESIS: intact through capillaries

Response to inflammatio and antigenic stimuli

346
Q

Describe lymphocytes

A

Large deep staining nucleus, mononuclear cells

B: humoral immunity, stimulated by antigens, transform to plasma cells, secrete immunoglobulins, antibody forming

T: express CD4 on surface (helper), can be killer cells, permit transformation of B cells into plasma cells, CD8+ suppressor cells. Mature in thymus

Natural killer cells too

347
Q

Describe the structure of erythrocytes

A

8 micrometre diameter
, biconcave disc

Carries haemoglobin, 4 globin chains, 2 alpha, 2 beta, each with a haem group

Spectrin and actin affect shape

Membrane with glycoproteins and antigens

If changes in shape, congenital or acquired, removed by spleen

348
Q

What is the lifespan of a red blood cell?

A

120 days

349
Q

What is the function of an erythrocyte?

A

Carrie oxygen to the tissues from the lungs, and carbon dioxide to the lungs

Maintains osmotic eqbrm of the circulation

Generates ATP from glucose making lactate

Flexible to pass through narrow capillaries

Provides oxygen when low, increase RBC production in response to hypoxia

350
Q

What are the two main metabolic pathways in RBCs?

A

Glucose to lactate and ATP, glycolysis and lactate dehydrogenase

Hexosemonophophate - G6P to ribose sugars by glucose 6 phosphate dehydrogenase to generate NADPH

351
Q

Describe haem catabolism

A

RBCs broken down in spleen, Hb to Haem

The iron is conserved

Unconjugated bilirubin yellow

Bilirubin conjugated in the liver, more watersoluble with glucaronic acid, less toxic

Liver to kidney, urobilinogen, yellow

Liver, gall bladder, in bile through bile duct, into intestines stercobilin, brown, egested

352
Q

What does bilirubin in the blood cause?

A

Yellow colour, in the skin and sclearae

Bilirubin produced when prophyrin opens up

Toxic

Attaches to albumin as not very water soluble

353
Q

Describe the structure and fucntion of reticular cells

A

Synthesise reticular fibres and surround them with cytoplasm

Type of fibroblast, type III collagen

Direct T and B lymphocytes to specific regions with the lymphatic tissues

354
Q

What is the structure of platelets?

How are they formed?

A

Small round blue particles

Cell fragments, stored in the spleen

Produced from megakaryocytes in the bone marrow

Complex surface membrane

Alpha granules with fibrinogen and von Willebrand’s factor

Dense granules with ADP and calcium ions

355
Q

What is a reticulocyte?

A

An immature RBC

356
Q

What is the function of platelets?

A

Adhesion to damaged cell walls and aggregate together

Provides phospholipid surface as a binding site for clotting factors in the cascade

Aggregation: release of ADP from granules, glycoprotein receptors exposed

Interacts with factors VII, IX and X

Fibrin mesh traps platelets and RBCs

357
Q

What does the bone marrow do?

Where is it found?

A

Produces RBCs, platelets and WBCs

Extensive bone marrow in infant

More limited in adult, mainly pelvis, sternum, skull, ribs and vertebrae

Blood cells released into sinusoids then the blood stream

358
Q

What is the reticuloendothelial system?

A

Part of the immune system, containing phagocytic cells:

Monocytes, kupffer cells, macrophages, tissue histiocytes, microglial cells

Cells of RES identify and mount an appropriate immune resposne to antigens

Main organs: spleen, liver and LN

359
Q

What are the types of T cells?

A

CD4 helper cells

CD8 suppressor cells

360
Q

Describe the components of the innate humoral immune system

A

Transferrin and lactoferrin, deprive microorganisms of iron

Interferons, inhibit viral replication

Lysozyme, breaks down petptidoglycan in cell walls of bacteria

Antimicrobial peptides

Fibronectin: opposes bacteria and promotes their phagocytosis

Complemet: causes microbe destruction directly with or without phagocytic help

TNF a: suppresses viral replication and activates phagocytes

361
Q

Describe the cellular components of the innate immune system

A

Macrophages/monocytes: phagocytosis and antigen presentation to lymphocytes

Neytrophils: phagocytic and antibacterial

Eosinophils: anti parasite and allergic respoinse

Basophils and mast cells, allergic response

Natural killer cells, recognise and kill abnormal cells such as tumours

362
Q

Describe the humoural components of the adaptive immune system

A

Cytokines: promote differentation and proliferation of lymphocytes

Perforin: released by T killer cells to destroy cell walls

Antibodies: protect host by neutralisation, prevents binding to epithelia, opsonisation and complement activation

363
Q

Describe the cellular components of the adaptive immune system

A

T cells: T helpers which become activated when CD4 binds to a specific antigen on MHC/antigen complex of an antigen presenting cell. Once activated, it clones itself to form active T helper cells and T memory cells

T killer, releases perforin when cell is already infected

B cells: divide to form plasma cells and memory cells when activated by a T helper, and release cytokines. Plasma cells produce specific immunoglobulins for a non self antigen

364
Q

What are the roles of proteins in pathogens?

A

Nutrient acquisition

Reproduction

Respiration

Locomotion

365
Q

How is the immune system alerted to damage?

A

By causing damage, breaking barriers to prosperous regions

Detect differences in proteins, different amino acid sequences

366
Q

What does epithelial tissue do as the first barrier to pathogens?

A

Innate immune system

Adaptations to clear pathogens from the surface, cilia, regeration, tears, nasal hairs, coughin, enzymes etc

Natural antibiotics

Cytokines

Chemokines (attracts other cells)

When pathogens break through, endothelium is leaky to let cells out, phagocytosis, opsonisation

367
Q

What is opsonisation?

A

Pathogen marked for ingestion and destruction by phagocyte

368
Q

Describe the features of the innate immune system

A

Present from birth

Non specific

Not enhanced by second exposure

No memory

Poorly effective without adaptive response

Cellular and humoral

Triggers and amplifies adaptive response

Importance shown by rarity of innate inherited disorders

369
Q

Describe features of the adaptive immune system

A

Arises from exposure to microorganisms

Specific pathogen immunity

Enhanced by second exposure

Acquires memory (memory cells)

Poorly effective without innate immunity

Cellular and humoral

Antibodies reflect infections to which they have been exposed, diagnostic tool

370
Q

When do the innate and adaptive immune systems start to work?

A

Innate: immediate, quicker to respond

Adaptive: slower to respond, multiplication of cells, but lasts much longer after infection

371
Q

What happens if innate or adaptive immune systems are lacking?

A

Innate lacking: does not respond well at all, microbes quickly multiply

Adaptive lacking: innate initially responds, then microbes proliferate

ESA 1 Revision (8 decks)

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