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Med 2024-2028 > TOB L3 > Flashcards

TOB L3 Flashcards

1
Q

Describe surfaces with epithelial linings

A

EXTERIOR SURFACES:

  • Skin
  • Surface of cornea

INTERIOR SPACES OPENING TO EXTERIOR

  • GI tract
  • Respiratory tract
  • Genitourinary tract

INTERIOR SPACES THAT DO NOT OPEN TO EXTERIOR

  • Pericardial sac
  • Pleural sacs
  • Peritoneum
  • Blood + lymphatic vessels
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2
Q

Describe how epithelial cells are derived

A

Epithelial cells are derived from all three germ layers of the embryo

Ectoderm =
- Epithelium (epidermis) of skin
- Corneal epithelium of eye

Mesoderm:
- Epithelium of urogenital tract
- Blood + lymphatic vessel lining
- Pericardial + pleural sac lining
- Peritoneal lining

Endoderm
- Epithelia of respiratory tract
- Epithelia of GI tract
- Epithelium of liver + glands including thyroid, thymus, salivary glands

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3
Q

Diagram showing the three germ laters of the embryo

A
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4
Q

Describe the different types of epithelia

A

Simple = (one cell layer thick)
-squamous
-cuboidal
-columnar
-pseudostratified

Stratified/compound = (>once cell layer thick)
-squamous
-cuboidal
-columnar
-transitional

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5
Q

What is the relation between epithelia and basement membranes?

A

All epithelia are anchroed to an underlying basement membrane

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6
Q

Describe the structure and function of the basement membrane

A
  1. Strong, sheet-like, flexible layer of ECM
  2. Supports epithelium + important in cellular signalling

Basement membranes are mostly compised of type III (reticular fibrils), type IV (basal lamina) and type VII collagens.

BM forms a thin, flexible, acellular layer separating epithelial cells from underlying connetive tissue

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7
Q

State how glycoproteinsw in the basement membrane are identified

A

PAS - Periodidc Acid Schiff stainining

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8
Q

How can we distinguish simple squamous epithelium?

A
  1. Nuclei bulge from cell surface
  2. Single layer
  3. Thin scale-like flat cells
  4. All rest on basement membrane
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9
Q

State locations of simple squammous epithelia

A
  1. Lining of blood and lymph vessels (endothelium
  2. Lining of body cavitities - pericardium, pleura, peritonduem (mesothelium)
  3. Respiratory epithelium - pulmonary alveoli
  4. Bowman’s capsule (kidney)
  5. Loop of henle (kidney)
  6. Inner and middle ear
  7. Intercalated pancreatic ducts
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10
Q

What is “endothelium” and state its function ?

A

Simple squamous epithelium lining vasculature (arteries, veins, capillaries, lymphatic vessels)

  1. Exchanges gases + nutrients
  2. Allows specific blood cells to enter tissues
  3. Regulates platelet coagulation
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11
Q

What is “mesothelium”?

A

Epithelium lining the body cavities (pleural + abdominal)

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12
Q

Functions of simple squamous epithelia

A
  1. Lubrication - to allow movement of viscera (pericardium, pleura, peritoneum)
  2. Gas exhange - in Pulmonary alveoli
  3. Barrier - in Bowman’s capsule
  4. Passive transport of water and ions - in loop of henle
  5. Active transport by pinocytosis (mesothelium + endothelium)
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13
Q

How can we distinguish simple cuboidal epithelium?

A
  1. Cells equal width + height
  2. Nucleus centrally placed + round
  3. May / may not feature brush border of microvilli
  4. All rest on basement membrane
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14
Q

State locations of simple cuboidal epithelia

A
  1. Thyroid follicles
  2. Small ducts of many exocrine glands
  3. Kidney tubules
  4. Respiratory bronchioles
  5. Mesothelium of ovary
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15
Q

Histology of simple cuboidal epithelium of pancreatic duct

A
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16
Q

State the role of simple cuboidal eputhelium in thyroid gland follicles

A

Simple cuboidal epithelium of thyroid gland follicles is made up of thyrocytes

Thyrocytes synthesise thyroxine, which is stored in its precursor form, thyroglobulin in the colloid

C cells (parafollicular cells) secrete CALCITONIN

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17
Q

State the role of simple cuboidal epithelium in the kidney tubules

A
  1. 65% of golumerular filtrate absorbed by PCT
  2. Na+ resorbed in DCT under control of aldosterone (secreted by adrenal cortex)
  3. ADH secreted by posterior pituitary gland increases permeability of collecting ducts leading to production of hypertonic urine
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18
Q

Histology of mesothelium of ovary

A
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19
Q

State functions of simple cuboidal epithelia

A
  1. Absoroption + conduit (exocrine glands)
  2. Absorption, conduit, secretion (kidney tubules)
  3. Barrrier / covvering (ovary)
  4. Hormone synthesis + mobilisation (thyroid)

conduit - channel liquid
mobilisation - moving

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20
Q

How can we distinguish simple columar epithelium ?

A
  1. Rectangular cells
  2. Ovoid, basal nucleus
  3. May be cilliated or may have microvilli
  4. All rest on basement membrane
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21
Q

State locations of simple columnar epithelium

A
  1. Stomach lining + gastric glands
  2. Small intestine + colon
  3. Gallbladder
  4. Large ducts of exocrine glands
  5. Oviducts
  6. Uterus
  7. Ductuli efferentes of testsis
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22
Q

Histology of simple columnar epithelium in the colon

A

Simple columnar epithelium: Crypts of Lieberkuhn in the colon

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23
Q

State the role of simple columnar epithelium in the gall bladder

A
  1. Concentrates bile (produced by liver) by absorbing water + electrolytes
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24
Q

State the role of simple columnar epithelium in straiated duct of parotid salivary gland

A
  • Removes Na+ to make saliva hypotonic (lots of energy + transporters needed)

Why is the simple columnar epithelium of this duct striated?

  • due to in foldings of the cell membranes
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25
Q

State 4 types of intercellular junctions

A

Interceullular junctions create a contiguous (boarders touching), functional epithelium

  1. Tight junctions
  2. Gap Junctions
  3. Adherance Junctions
  4. Spot Junctions

(make sure to recognise on diagram)

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26
Q

Tight Junctions

A
  1. Also called Zonula occludens
  2. Consist of occludins + connect microfilaments of adjascent cells
  3. Control diffusion in apical regions
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27
Q

Adherens junctionjs

A
  1. Formed of belts of cadherin proteins linking microfilaments of adjascent cells
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28
Q

Spot Junctions

A
  1. Also called maculae adherens / desmosomes) are comprised of integrins + provide a contigous epithelium
  2. Anchored to intermediate filaments
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29
Q

State the function of hemidesmosomes

A

Anchor cells to basal lamina via integrins

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30
Q

State the function of Junctional Complexes

A

Control passafe of luminal complexes between cells

Junctional complexes isolate the luminal sapce from the intercellular space.

Fluid is moved from e.g. the intestinal lumen into cell, then into intercellular sapce, then across basement membrane into connective tissue, int vasculature

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31
Q

State the functions of Cholera Toxins

A

Disrupt complex junctions in gut
This increases intestinal permeability

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32
Q

Give an example of a specialisation of epithelia

A

Simple columnar epithelia cells with microvilli

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33
Q

Describe the structure and function of microvilli in the context of simple columnar epithelia

A

Microvilli are apical extensions that greatly increase the surface area for selective absorption of intestinal contents

Supported by actin microfilaments + join microfilaments of cytoskeleton at the terminal web

34
Q

Describe how the surface area of the small intestine is increased

A
  1. Plicae circulares
  2. Villi
  3. Microvilli

The mucosa of the samll intestine have a series of folds called plicae circulares

Outgrowth of villi from mucosa further increase SA

Microvilli increase SA of plasma membrane for absorption

35
Q

Describe the sturcture and function of lacteals

A

Lacteals (dilated lymphatic vessels)
In lamina propria
Absorption of fat

Smooth muscle produces local rythmc movements to improve efficiency of absorption

36
Q

State the structure and function of cilia

A

Short, motile, membrane extensions
Supported my microtubules
Move substances (e.g. mucus) over cell surface

37
Q

Describe how cillia are motile

A

Motile means they can move themselves
This is due to transient interactions between dynein + microbules

38
Q

How are cillia anchored?

A

Cillia are anchored at BASAL BODIES

39
Q

Give a structural difference between cilia and microvilli

A

Longer + wider
core structure = axoneme

40
Q

Give an example of cilliated simple colunnar epithelium

A

Oviduct
Cillated cells propel ova towards uterus
Non-cilliated peg cells produce mucus (arrow on diagram)

41
Q

State functions of simple columnar epithelia

A
  1. Absorptiuon - small intestine, colonn, gallbladder
  2. Secretion - stomach lining, gastric glands, small intestine, colon
  3. Lubrication (small intestine + colon)
  4. Transport (oviduct)
  5. Lining of some larger exocrine ducts
42
Q

How can we distinguish pseudostratified columnar epithelium?

A
  1. Some cells tall, some short
  2. All rest on basement membrane
  3. Some cilliated
  4. Nucleu found in basal 2/3?
43
Q

State locations of pseudostratified columnar epithelia

A
  1. Lining of nasal cavity, trachea, bronchi
  2. Epididymis, extending into ducturs (vas) deferens
  3. Large excretory ducts e.g. of salivary glands
  4. Auditory rube + part of tympanic cavity
  5. Lacrimal sac
  6. Parts of male urethra
44
Q

Histology of upper (conducting) respiratory tract

A
  • Motile cilia
  • Mucus secreting goblet cell
  • Nuclei at different levels
  • Thick basement membrane
45
Q

Describe the mucocillary escalator

A
  1. Cillia associated with epithelium of upper respiratory tract beat at 12 Hz within a watery SOL (solution?) exuded (released) by epithelial cells
  2. Above “sol” lies a “gel” viscoelastic blanket of mucus.
  3. Mucus immobilises particles + lubricates their passage as cillacry action moves them in one direction to the oropharynx, where they are swallowed
46
Q

Diagram of upper respiratory tract

A
47
Q

State the meaning of viscoelastic

A

Substance with both viscous + elastic properties when deformed

48
Q

Describe the structure and function of the epididymis

A

Coiled tube behind each testis
Pseudostratified epithelium
Sperm from testis mature + aquire motility as they move through it
They have principal cells

49
Q

State the function of principal cells in the epididymis

A

Absorb fluid
Secrete substances to promote maturation of sperm, phagocyte residual bodies + degenerating sperm

50
Q

What are the stem cells of the epithelium?

A

Basal cells

51
Q

Describe the structure and function of stereocilia in the epididymis

A

Giant microvilli
Immotile
Supported by actin

Increase SA for absorption, phagocytosis, secretion
(including phagocytosis of degenerate spermatoaoza)

52
Q

Histology of interlobular duct of parotid gland

A
53
Q

Describe the structure and function of the salivary glands

A

Anterior + inferior to opening of ear + produces serous (watery) secretions

54
Q

Functions of pseudostratified columnar epithelium

A
  1. Secretion and conduit (a channel) (respiratory tract, ductus deferens/sperm duct/vas deferens)
  2. Absorption in epididymis
  3. Particle trapping + removing (respiratory tract)
55
Q

How can we distinguish stratified squamous epithelium (non-keratinised)?

A

Squamous cells are the most outer layer

56
Q

State locations of stratified squamous epithelium (non-keratinised)

A
  1. Oral cavity
  2. Oesophagus
  3. Larynx
  4. Vagina
  5. Part of anal canal
  6. Surface of cornea
  7. Part of inner surface of eyelid
  8. Distal urethra
57
Q

State the function of stratified squamous non-keratinised epithelium in the oesophagus

A
  1. Provides protection from abrasion
  2. Minimises water loss
58
Q

Describe how shedding flattened cells are replaced within the stratified squamous non-keratnised epithelium in the oesophagus

A

Flattened cells shed from surface replaced by:

  1. Proliferation (rapid reproductio of cell)
  2. Differntiation of basal cells
59
Q

Describe the sturcture and function of the epiglottis

A

Flap of tissue that sits beneath your tongue at the back of the throat

Closes windpipe (trachea) while eating to prevent food entering the airway

60
Q

Describe the epithelium present in the epiglottis

A

Two sides of epiglottis are lined by 2 different types of epithelium.

  1. Stratified squamous non-keratnised epithelium (buccal cavity, oesophagus)
  2. seudostratified columnar epithelium
    (characteristic of upper respiratory tract)

PAY ATTENTION TO HISTOLOGY
MAKE SURE YOU TELL THE DIFFERENCE IN EPITHELIUM

61
Q

Histology of epithelium of epiglottis

A

PAY ATTENTION TO HISTOLOGY
MAKE SURE YOU TELL THE DIFFERENCE IN EPITHELIUM

62
Q

Histology of stratiefied squamous non-keratanised eipithelium in the cornea

A
63
Q

Describe the function of stratified squamous non-keratinised epithelium in the vagina

A

Produces glycogen under influence of oestrogen
Glycogen is substrate for lactobacilli, which reduces pH by producing lactic acid
Prevents colonisation by pathogenic organisms
Epithelium degenerates post menopause

64
Q

State functions of stratified squamous non-keratinised epithelium

A
  1. Protection against abrasion
  2. Reduces water loss, but itself is moist
  3. Secretion (vagina)
65
Q

How can we distinguish stratified squamous keratinised epithelium?

A
66
Q

State locations of stratified squamous keratnised epithelia

A
  1. The skin (Epidermis)
  2. Limited distrobution in oral cavity (e.g. gums)
67
Q

Histology of stratified squamous keratinsied epithelium in epidermis (thin skin)

A
68
Q

Histology of stratified squamous keratinsied epithelium in epidermis (thick skin, sole of foot)

A
69
Q

State functions of stratified squamous kerinised epithelia

A
  1. Protection against abrasion + physical trauma
  2. Prevention of water loss
  3. Prevention of microbe ingress
  4. Shield against UV light damage
70
Q

How can we distinguish transitional epithelium?

A
71
Q

Describe the location of transtional epithelium

A

Lines upper (proximal) parts of urinary tract

  1. Renal calyces (singular: calyx)
  2. Ureter
  3. Bladder
  4. Urethra (proxomal)
72
Q

Describe the structure and function of the transitional epithelium in the urether

A

Transitional epithelium is distensible, Allowing structures to stretch as they fill with urine.

Protection of underlying tissue from cytotoxic effects of urine

RECOGNISE BINUCLEATE DOME CELL

73
Q

Define the term “distensible”

A

Stretching by internal pressure

74
Q

Histology showing the difference between a relaxed and distended ureter

A
75
Q

Describe how the organisation of transitional epithelium changes in the ureter

A

Chanegs from smapp basal cells to intermediate layers of more columnar cells, with a superficial layer of bulbous umbrella cells

76
Q

Describe the rates of renewal of epithelia

A

Epithelia constantly proliferate to maintain protective barriers

Cell renewal rate of epithelia higher than other tissues

Renewal rate increases following injury

Time taken from cell division in basal layer of epidermis to eventually being rid of is 28 days

77
Q

Which epithelium has the longest turn over time?

A

Respiratory epithelium

78
Q

Describe how enterocytes are replaced

A

By regeneratvive cells in base of intestinal crypts
(every 3.48 days)

79
Q

State the 3 different shapes of epithelia

A
  1. Squamous
  2. Cuboidal
  3. Columnar
80
Q
A

Med 2024-2028 (56 decks)

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