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Systems Physiology > Epithelia > Flashcards

Epithelia Flashcards

1
Q

What are the common functions of epithelia

A

protection, sensation, absorption, digestion, secretion (glands), excretion and cleaning

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2
Q

What separates epithelia from underlying connective tissue

A

basement membrane that varies in thickness depending on the type of epithelium

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3
Q

What functions/roles does the basement membrane have

A
  • anchor down the epithelium to its loose CT (in dermis)

- The basement membrane has a supportive function

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4
Q

What is the basement membrane formed of

A

proteoglycans and collagen types 3 and 4

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5
Q

What kinds of cells are found in simple epithelia

A
  • Comprise a single layer of cells which all rest on the basement membrane
  • Consist of cells that vary in shape from flattened to columnar according to their function.
  • may have microvilli and cilia
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6
Q

Where can simple epithelia be found

A
  • Are found lining absorptive or secretory surfaces (e.g. intestines)
  • Where minimum barrier to passive diffusion is required (e.g. alveoli, vessels)
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7
Q

What cells are found in simple squamous epithelia

A

Consists of a single layer of flattened cells and are found lining surfaces

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8
Q

What kind of surface does simple squamous epithelia line

A 
Surfaces involved in the transport of :
- gases (e.g. lung alveoli)
- fluids (e.g. lymphatics,
blood vessels)
- Series body cavities
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9
Q

What cells are in simple cuboidal cells

A

Consists of a single layer of square shaped cells.

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10
Q

What kinds of things does simple cuboidal epithelia line and give examples

A
  • Line small ducts and tubules that have secretory, excretory or absorptive function
  • eg. bile duct, renal medulla, salivary glands
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11
Q

What cells are in simple columnar cells

A

Are similar to cuboidal epithelium except that the cells are taller and have elongated nuclei usually at the base of the cell.

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12
Q

What surfaces do simple columnar cells line

A
  • absorptive surfaces (eg. small intestine)

- secretory surfaces (eg. stomach)

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13
Q

What cells are found in the stratified epithelia

A

Consist of two or more layers of cells

Can be keratinised, e.g. in skin in order to resist friction, bacteria infection and to be waterproof

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14
Q

What is used to classify stratified epithelia

A

only the surface layer of cells

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15
Q

What is the main function of stratified epithelia

A

Protection

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16
Q

What determines the degree and nature of the stratification

A

the type of stress to which the surface is exposed

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17
Q

What kind of cells are usually found in stratified squamous epithelia

A
  • Usually several layers, thick (eg. skin)
  • Matures progressively from the basal layer which has cuboidal-shaped cells through to the surface layer where the cells are flattened
18
Q

Give an example of non-keratinised stratified squamous epithelia

A

oral mucosa

19
Q

What kind of cells are found in the stratified cuboidal epithelia

A

Consists of two or three layers of cuboidal cells

20
Q

What does the stratified cuboidal epithelia line and give examples

A

Is found lining larger excretory ducts, such as those of

the salivary glands, sweat glands and pancreas

21
Q

What functions do the stratified cuboidal provide

A

Does not have an absorptive or secretory function but provides a more robust lining than that of simple epithelium

22
Q

Describe the cells found in the pseudo-stratified epithelium

A
  • All cells rest on the basal lamina but not all reach the surface and thus nuclei are at different levels giving the appearance of a stratified epithelium
  • May be ciliated (trachea/upper respiratory tract) or non-ciliated
23
Q

Where can transitional epithelium be found

A

Is a special form of stratified epithelium found in the urinary tract

24
Q

Why is the transitional epithelium found in the urinary tract

A
  • Is specialised to withstand the toxicity of urine
  • Can accommodate to distension, a high degree of
    stretching
25
Q

Why is transitional epithelium termed “transitional”

A

Has an appearance intermediate between that of stratified cuboidal epithelium and stratified squamous epithelium, hence “transitional”

26
Q

What is a tight epithelial junction

A

seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them

27
Q

What is a gap epithelial junction

A

Cell-Cell junction allowing the passage of small water soluble ions and molecules

28
Q

What is the mucous membrane made of

A
  • Epithelium
  • Basement membrane
  • Lamina propria (loose
    CT)
  • smooth muscle
29
Q

What specialised cells can be found in the mucous membrane

A
  • Mucus secreting goblet cells

- Absorptive enterocytes

30
Q

What are the different portions of a gland

A

Composed of a secretory portion and a non- secretory or excretory portion (exocrine glands).

31
Q

What are the 2 types of gland

A
  • Exocrine glands discharge their secretory product via
    a duct onto an epithelial surface
  • Endocrine glands secrete hormones directly into the bloodstream and are composed of highly specialised epithelial cells.
32
Q

What are the sections of the exocrine glands

A
  • excretory ducts

- secretory portions

33
Q

In exocrine glands what can the secretory portions be

A

Tubular or acinar (alveolar)

34
Q

What are the 3 secretory mechanisms of exocrine glands

A
  • Eccrine/Merocrine
  • Apocrine
  • Holocrine
35
Q

What can be the 4 secretion contents of exocrine glands

A
  • Sweat-water
  • Mucous-Mucous
  • Serous-proteins/enzymes
  • Sebum-lipids
36
Q

Describe the mechanism of Eccrine/merocrine secretion

A
  • Secretory granules fuse to plasma membrane and are secreted-exocytosis
  • e.g. eccrine sweat gland (thermoregulation)
37
Q

Describe the mechanism of Apocrine secretion

A
  • Unbroken, membrane-bound vesicles accumulated in apical cytoplasm, which then pinched off, the cell losing part of cytoplasm in the process
    e. g. apocrine sweat gland (body odour)
38
Q

Describe the mechanism of Holocrine secretion

A
  • The whole cell lysis and entire contents secreted, thus the cells are lost in the process
  • e.g. sebaceous gland
39
Q

Describe the features of endocrine glands

A
  • Much simpler than exocrine (no duct)
  • Supporting tissue is thin and sparse (reticular CT)
  • and associated with a very rich blood capillary
40
Q

What are the 2 types of endocrine gland

A

Cord and clump - most common

Follicle - thyroid glands

Systems Physiology (28 decks)

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