TOB Flashcards
State the meaning of the term tissue?
A group or later of cells that performs a specific function
How many mm in 100,000 nm?
0.1 mm
How many um?
Explain the value of histology in diagnosis
Gold standard of diagnosis
Final proof of a disease and can determine the appropriate treatment
What is histology
The study of the structure of tissues by means of a special staining techniques and light electron microscopes
What technique involves the removal of a small piece of tissue from an organ or part of the body for microscopic examination?
Biopsy
List 6 common biopsy techniques, and give examples of tissues that can be sampled by each method.
Endoscopic. Intestine, lung, bladder
Direct incision. Close to surface. Skin, mouth, larynx
Needle. Liver, kidney, brain, breast, muscle
Transvascular, liver, heart
Cutterage, endometrial lining of uterus surface
Smear, cervix
In biopsys why does tissue need to be fixed?
To preserve the cellular structure. Prevents autolysis (destruction of itself by its own enzymes) and putrefaction
name 2 common fixatives
Glutaraldehyde
Formaldehyde
Describe the process of fixing in biopsy
Fixation of a fresh sample
Dehydration with ethanol
Clearing with xylene or toluene
Embedding in wax at 56 degrees
How do you process a sample embedded in wax for viewing under a microscope?
Thin section into of the wax block Rehydration. With water and ethanol and xylene Staining Dehydration Mounting Microscope
How are shrinkage artefacts formed?
Dehydration by ethanol
And then rehydration by ethanol water and xylene
When is the stain PAS used. Periodic acid Schiff reaction,
Carbohydrates. E.g. Glucose, starch, glycogen , ribose (ATP, FAD, NAD) Statins
Glycoproteins
Stains pink
When is haematoxin and eosin stain used?
Haematoxin stand acidic componants, purple and blue
E.g. DNA chromatin. And RNA
Eosin, stains basic components pink.
E.g.mcyroplasmic proteins and extracellular fibre.
Describe and explain advantages of phase contrast
Uses two light waves,
Keeps cell alive
Dark field.
In light and electron microscopy
Excludes in scattered beam from the image,
Therefore field around specimen (no specimen to scatter beam) is dark
Used to detect syphilis or malaria
Fluorescence.
Target molecule of interest with fluorescent stain. Can Use multiple different stains on the sample so can test for multiple things at once
Can detect undetected uv Rays
Confocal
Eliminates out of focus flair.
Used in living specimens
Define epithelial
Sheets of continuous cells that cover the external surface of the body, internal spaces that open to the exterior and interior spaces
Name the three locations where mesothelium are located.
Cavities Pleural sac Pericardial sac Peritoneal Blood vessels
Give examples of open cavities in the body where epithelia are located.
Digestive
Respiratory
Urgogenital tract
Where is the basement membrane (basal lamina) located?
What is its function?
In between epithelial cells and subtending connective tissue
Function: cellular and molecular filter, and a strong flexible layer for epithelial cells to adhere to
Also surrounds cells, e.g. Muscle fibres
Underneath sheets of epithelial cells
Separates 2 sheets of cells
Made of collagen, glycoproteins, to make a thin extracellular matrix
Name a purpose of reticular fibres (type 3 collagen)
Used in connective tissue in lymphoid organs and adipose tissue
How do we classify epithelia?
Simple/stratified
Shape
Give an location of simple squamous epithelia
Lining of blood vessels, pulmonary alveoli, Bowmans capsule, middle ear Functions. Thin so good for diffusion, Lubrication Barrier Active transport by pinocyctosis.
Location and function of simple cuboidal epithelia
Functions. Absorption and conduit (exocrine) Locations: Ducts in Exocrine glands Thyroid follicles Kidney tubules
Simple columnar (& with micro villi)
Functions: absorption, secretion, lubrication, transport
Stomach lining, small intestine, colon
Nucleus positioned basally
Micro villi to assist absorption in GI.
Stratified squamous (non keratinized)
Resists abrasion and trauma, reduces water loss
Oesophagus, vagina, oral cavity
Stratified squamous keratinized
Waterproof, no nuclei as dead,
Skin surface
Protects against uv, water, abrasion, microbes
(Simple) pseudo stratified
Secretion, absorption,mp article trapping and secretions, mucous secretion
Lining of nasal cavity, trachea and bronchi
Epididymis
Can have cilia
Stratified transitional
Distends when full. Protects tissue from toxic chemicals
Bladder
Ureters
Explain the reason for different rates of renewal at each type of epithelium
Cell renewal rate is high and In most epithelia is occurs regularly
It is Different in different locations e.g. Bladder every 4-5 days and epidermis every 28. Some don’t change after puberty
Name three surface specialisations of epithelium. And describe how their structure is related to its function
Microvilli, apical extensions that greatly increase the SA for absorption in the intestines
Stereocillia, very long microvilli. Surface or ductus deferens and epidermis
Cilia. Beat in consecutive waves. Lining of trachea and Fallopian tubes
Give examples of when epithelial cells would regenerate or be replaced
Regeneration would occur in skin wound healing
Replacement of surface cells on skin
Renewal of uterine lining cells after menstuation
Describe metaplasia .
Give an example
Epithelial cells that have the capacity to change from one type of epithelial cells to another
E.g. In heavy smokers. Pseudo stationed columnar epithelium of respiratory tract can change to stratified squamous
Describe neoplasia
In disease, e.g. Cancer, changes may occur in epithelia giving rise to a tumour (neoplasm) - a carcinoma
Where is the glomerulus located? And what is its function
Network of blood capillaries within renal corpuscle
Primary site of blood filtration in the kidneys.
What cell is located in the darker staining region of the kidney cortex?
Its function is to filtrate the blood?
The renal corpuscles.
Comprises of renal tubule (Bowmans capsule) surrounded by glomerulus
Why is DNA acidic ( roughly)
you compare the structures of phosphoric acid (Figure 1) and a short strand of DNA (Figure 2), you’ll see that in the latter, two protons of phosphoric acid are replaced by carbon atoms either in, or attached to, the five-membered ring.
In chemical terms, such a group is called a phosphate diester. The remaining proton is now quite acidic, and is relatively easily lost, thereby giving DNA its acidic character.
Indeed, under neutral conditions, DNA is deprotonated at this site, and the oxygen atom bears a negative charge. Despite the fact that DNA does contain many basic groups, their basic properties are masked somewhat because of the fact that they hydrogen bond with each other to form base pairs. Hence it’s the acidic part of the molecule that dominates, and that is why we know DNA as an acid.
Describe what a gland is
An epithelial cell or aggregate of cells specialised for secretion.
Name the type of gland that secretes substances directly into the blood stream. And give an example
Endocrine.
E.g. Adrenal glands
Cords (adrenal cortex)
Follicles (thyroid)
Clusters (pituitary)
Give an example of an exocrine gland and state how they secrete
Secrete through ducts to epithelium and lumens of organs.
E.g. Goblet cells, parotid glands
Can be unicellular (release secretions mucus to surface epithelium) or multicellular (to underlying connective tissue).
Name the three types of secretion
Merocrine.
Apocrine
Holocrine
Describe Merocrine secretion
Sweat glands
Exocytosis
Secretion contained within membrane bound vesicle.
Fuses with plasma membrane
Makes plasma membrane larger
Contents released into extracellular space
Membrane retrieved and stabilises cell surface area.
Describe apocrine secretion and give an example
Lactation ,mammary glands
Non membrane bound structure, e.g. Lipid
Pushes against apical membrane and pinches off from the cell
Makes the plasma membrane smaller so more membrane is added
Describe holocrine secretion
The cell disintegrates and releases the contents
Sebaceous glands
Describe endocytosis
Cell engulfs the material and takes it into the cell
Describe how material is transported across the epithelium
Coupling reaction between ends and exocytosis .
Engulfed by endocytosis.
Transport vesicle transports the material across the cell.
Secreted by exocytosis
What is the function of the Golgi apparatus and where do its products go?
Packages its contents through condensation
Adds sugars to proteins and lipids (glycosylation)
Secreted in vesicles
Some retained in the cell, e,g. Lysosomes
Some to plasma membrane (glycocalyx)
Why do we glycosylate some proteins and lipids?
To make more complex shapes for specific interactions in the glycocalyx.MORE SPECIFIC
For adhesion, mobility, communication,
How is secretion controlled
Negative feedback
Nervous
Endocrine
Neuro-endocrine
Where are goblet cells found, and what do they look like when Staines with alcian blue. What colour are they under haemotoxin and eosin?
Jejunum, intestinal epithelia, tubular glands in large intestine
Mucins stains vivid blue
Not stained,
Give an example of a compound serous exocrine gland.
Parotid gland, occurs in pairs- part of salivary glands
Located below and in front of each ear,
Enzymes are located in the cytoplasm of its acinar cells as zymogen granules
Give an example of a mixed, compound, tubule acinar gland and describe it
Submandibular glands
Serous, mucous and mixed acini
Large glands surrounded by connective tissue capsule, sends septa into the glands which divides it into lobes
Location : just below the mandible of either side of the neck. Release secretions (saliva) into floor of mouth
Are Most secretions of endocrine glands are stored intracellularly or extracellulary? Give an example of the most common type? And explain its function?
Most e doctrine glands the secretions are stored intracellularly.
For example the adrenal gland
Made up of the cortex and the medulla
What does each part of the adrenal cortex secrete?
Zona glomerulosa- aldosterone, mineralocorticoids
Zona fasiculata- glucocorticoid hormones e.g. cortisol,
Zona reticularis - androgens and (some glucocorticoids)
Adrenal medulla- catecholamine hormones: adrenaline noradrenaline
What does the parathyroid gland secrete? What does this stimulate?
Is the parathyroid gland exocrine or endocrine?
PTH secreted by chief cells
Stimulates osteoclasts to reabsorb bone and reduce calcium loss as urine
Promotes calcium uptake by gut
Exocrine
Give an example of gland that stores secretory products extracellulary in follicles
Thyroid gland
Follicles lined by glandular cells
Lots of capillaries
Name an organ with mixed endo and exocrine glands, and describe
Lies behind stomach and one end by curve of duodenum
Endocrine gland, islets of langerhans, scattered within exocrine tissue.
Exocrine, most of the tissue, closely packed secretory acini that drain into a highly branched duct system lined with simple columnar epithelium and goblet cells.
Secretes digestive enzymes into duodenum and hormones into bloodstream
What do the islets of langerhans secrete?
Insulin (alpha cells
Glucagon (B cells)
Somatostatin (delta)
What do the pancreatic acini secrete. The exocrine part of the pancreas
Pro enzymes:
- e.g. trypsinogen
Pancreatic amylase and lipase
How does cystic fibrosis affect the pancreas?
Mucus secretions become thicker which block the duct, preventing fat digestion (digestive enzymes not secreted, decreased lipase) and causing pancreatitis.
This is due to the mucus secretions contain too little water.
The CFTR gene causes a transmembrane regulator is effective which means that cl and Na ions are not transported effectively disrupting osmosis.
Give examples of mucous membranea and their functions
Line internal tubes that open to the exterior
Alimentary, (GI)
Respiratory
Urinary
Label on histology, the layers of the wall
Epithelia lining
Connective tissue (lamina propria)
Muscularis mucosae (ailmentsry tract, smooth muscle)
Name examples of serous membranes
Closed cavities, shiny look Peritoneum (envelops abdominal organs) Pleural sacs, lungs Pericardial sacs Mesothelium secretes lubricating fluid, 2 layers: mesothelium, and thin connective tissue,
What is connective tissue made up of (broadly)
Cells, including fibroblasts, defence cells, storage cells, and mesenchymal (undifferentiated) Fibres, (collagen, elastin, reticulin) Ground substance (protein, glycoprotein, gags, lipid, water)
What is connective tissue and what is its function?
Links together muscle nerve and epithelial tissue
Provides support in metabolic and physiological processes (diffusing medium)
Injury repair
What are mesenchyme cells and what can they develop into? Give an example of a connective tissue where they are found
From middle embryonic germ layer. Multi potent. E.g, in mucous connective tissue in umbilical cord
Form fibroblasts that secrete collagen found in ligaments, tendons, supporting tissues
Lipoblasts, fat cells
Chondroblasts, cartilage
Osetoblasts, bone
Myoblasts, skeletal muscle
Describe the extracellular matrix in connective tissue
Hyaluronic acid (GAG) with attached proteoglycan aggregates Interwoven with collagen
Describe the types of collagen and their functions
Ty1: most common, Triple helix found in bundles. In skin, tendons, vascular, organs, bone
Ty2: cartilage
Ty3: reticulate in reticulum fibres. Supporting mesh in soft tissues e.g. Liver and bone marrow. lymphatic tissue
List three common cells found in connective tissue and their properties
Fibroblasts, lots of RER and secretory vesicles
Synthesis and secretion of ground substance proteins - Collagen, and glycoproteins
Macrophages. In loose connective tissue, from blood monocytes
Mast cells. Granules contain histaminses and heparin. Binds allegens
Describe and give locations and types of dense irregular connective tissue
Connects epithelial tissue of skin to underlying tissue
Irregular: interwoven bundles of collagen. Criss cross, to counter multidirectional forces.
E.g. Dermis of skin, periosteum around bone, perichonfium around cartilage.
Dermis, found below epidermis containing blood vessels, skin appendages (hair follicles, sweat glands, sebaceous glands) sensory neurones
Describe and give examples of dense gulag connective tissue
Parallel collagen fibres, more tensile strength
Tendons (muscle to bone) , ligaments (bone to bone), open neurones
Tendons have flattenend fibroblasts - looks like slender nuclei
Not striated and nuclei more squished than in muscle
Describe and give examples of loose connective tissue
Less closely packed fibres,
More ground substance and cells
E.g. Beneath epithelial surfaces, around blood vessels, nerves and lymph nodes. Used as packing
E.g. Mucous connective tissue
How does vitiligo form?
Autoimmune depigmentation
Less noticeable in whites
Often symmetrical
Describe three other skin diseases caused by variations in macroscopic structure of skin (hair ,thickness, colour, laxity, oiliness)
Alopecia areata (hair loss)
Uv induced, ageing, sunburn, cancer
Acne
Describe how the epidermis is formed
1) keratinocytes mitosis in basal layer
2) daughter keratinocytes move up to prickle cell layer and produce keratins
3) keratinocytes terminally differentiate into corneocytes, main cells of the stratum corneum
4) stratum corneum made up of layers of flattened corneocytes
Takes 30-40 days