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Semester 1 - Body Logistics > 4. Epithelial Cells And Surface Specialisations > Flashcards

4. Epithelial Cells And Surface Specialisations Flashcards

1
Q

Where are mucous membranes found? Give some examples.

A

Line certain internal tubes which open to the exterior.

E.g. GI Tract, Urinary Tract, Respiratory Tract.

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2
Q

What does a mucous membrane consist of?

A
  • Epithelium lining the lumen of the tube
  • Adjacent layer of connective tissue called Lamina propia.
  • Third layer consisting of smooth muscle called muscularis mucosae.
  • (blood and lymphatic vessels and nerves)
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3
Q

What are serous membranes?

A

thin, two part membranes that line certain closed body cavities (spaces which do not open up to the exterior) and envelope the viscera.

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4
Q

Where are serous membranes found?

A
  • Peritoneum (envelops many abdominal organs).
  • Pleural sacs (envelops the lungs).
  • Pericardial sacs (envelops the heart).
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5
Q

What does a serous membrane consist of?

A
  • A simple squamous epithelium (mesothelium) that secretes the watery lubricating fluid.
  • A thin layer of connective tissue that attaches the epithelium to the adjacent tissue.
  • (also carries blood and lymphatic vessels and nerves).
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6
Q

What do serous membranes exude?

A

A lubricated fluid that promotes relatively friction free movement of the structures they surround

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7
Q

How are serous membranes formed around organs?

A

During embryonic development the heart, lungs and gut develop next to a bag like cavity into which they invaginate. So they become surrounded by a serous membrane that has an inner (visceral) and outer (parietal) part.

(Organs do not lie in the cavity, rather they are surrounded by it)

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8
Q

Differentiate between the visceral and parietal serosal membranes aswell as the serous cavity

A

Outer wall is called the parietal serosa (next to tissue) and the inner wall is called the visceral serosa. Space within is the lubricating serous cavity

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9
Q

What volume of fluid is present in each serous membrane?

A
  • Peritoneum has 10 ml
  • Pleural sacs each have 5 ml
  • Pericardium has 2 ml
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10
Q

What are epithelia?

A

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces, including the body’s vessels.

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11
Q

What are the different classifications of epithelial tissue?

A

Simple: squamous, cuboidal, columnar, pseudostratified.

Stratified/Compound: squamous, cuboidal, columnar, transitional.

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12
Q

What are epithelial tissues derived from?

A

All of the embryological germ layers:

  • the epidermis is derived from the ectoderm
  • the inner and outer lining of the GI tract are derived from the endoderm
  • the inner linings of body cavities are derived from the mesoderm
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13
Q

What exterior surface has an epithelial lining?

A

Skin

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14
Q

Which interior spaces opening to the exterior have epithelial linings?

A

GI tract, respiratory tract, genitourinary tract

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15
Q

Which interior spaces which do not open to the exterior have epithelial linings?

A

Pericardial sac, pleural sacs, peritoneum, blood vessels and lymphatic vessels

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16
Q

Define simple and stratified/compound epithelium?

A

Simple epithelium are only one cell layer thick.

Stratified epithelium are more than one cell layer thick.

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17
Q

Where are simple squamous epithelium found?

A
  • Alveoli,
  • endothelia lining heart, blood vessels and lymphatic vessels
  • Bowmans capsule
  • serosa of lungs, heart and viscera (mesothelium) —> tissue lubrication
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18
Q

Define mesothelium

A

the simple squamous epithelium that lines the body cavities enclosing the lungs, heart and abdominal organs

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19
Q

What functions do simple squamous epithelia have?

A
  • Fast material exchange and barrier to fluids.e.g. vasculature and lymphatics, respiratory space in the lung
  • Barrier in the brain and CNS.
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20
Q

Where are simple cuboidal epithelium found?

A
  • Thyroid gland follicles,
  • Lining of the pancreatic duct,
  • Lining of collecting ducts in kidney.
  • glands
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21
Q

What types of cells line most ducts and why are these better than squamous?

A

Simple cuboidal - thicker than squamous so substances can’t travel across the membrane too quickly

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22
Q

Describe simple cuboidal epithelia

A

a single l;layer of polygonal cells, whose height and width are approximately equal

23
Q

What functions do simple cuboidal epithelia have?

A
  • Absorption and conduit (exocrine glands),
  • Absorption and secretion (kidney tubules),
  • Barrier/covering (ovary),
  • Hormone synthesis, storage and mobilisation (thyroid).
24
Q

What is a conduit?

A

A channel for conveying water and fluid

25
Q

What organ(s) stores its product outside of the cells that produce them?

A

Thyroid organ is the only organ that stores product outside the cell.

It stores thyroglobulin in the centre (lumen) of the follicle called colloid.

26
Q

What do epithelial cells bounding the thyroid gland follicles do?

A

Synthesise thyroglobulin and store it in the centre of the follicle (colloid).

There, thyroglobulin is reprocessed to produce thyroxine which is released into the blood (hormone)

27
Q

Why are the follicles of the thyroid gland follicles only approximately spherical?

A

When processed some water is removed from the follicle which makes it lose some of its shape

28
Q

Why do collecting ducts of the kidney have thick basal lamella?

A

Prevent fluids from going back into the tissue when it is full of urine

29
Q

Where are simple columnar epithelium found?

A
  • lining of Stomach and gastric glands.
  • Small intestine and colon.
  • gallbladder
30
Q

Describe simple columnar epithelia

A

a single layer of cells whose heights are greater than widths

31
Q

What functions do columnar epithelium have?

A
  • Absorption (Small intestine & colon, gallbladder).
  • Secretion (Stomach lining & gastric gland, Small intestine & colon).
  • Lubrication (Small intestine &colon).
32
Q

What are the intestinal glands called?

A

Crypts of Lieberkuhn.

33
Q

What is the role of vacuoles in goblet cells?

A

they are small secretory vesicles that produce mucins and water.

34
Q

What is the role of the lacteal vessels present in the villi of the small intestine?

A

Absorbs dietary fats from the villi and transports it into the blood stream as chylomicrons at the subclavian vein. This then takes the fat to the liver to be absorbed there.

35
Q

Why do pseudostratified give the give impression of having several layers?

A

All the cells make contact with the basement membrane but not all of them reach the epithelial cell surface. This results in nuclei lying at different levels giving the impression of multiple cell layers

36
Q

Where are the nuclei in simple columnar cells?

A

Always near the basal lamina

37
Q

what specialisation can be found on simple columnar epithelium?

A

MICROVILLI

38
Q

Where are psuedostratified columnar epithelium found?

A
  • Lining of the nasal cavity,
  • Trachea,
  • Bronchi.
39
Q

What functions do psuedostratified columnar epithelium have?

A
  • Secretion and conduit (respiratory tract, ductus deferens),
  • Mucus secretion (respiratory tract),
  • Particle trapping and removal (Respiratory tract (ciliated epithelium)).
40
Q

What specialisation can be found on psuedostratified columnar epithelium ?

A

cilia

41
Q

What rate to cilia beat at?

A

12Hz

42
Q

Where are non-keratinised stratified squamous epithelium found?

A
  • Oral cavity,
  • Oesophagus,
  • Vagina,
  • Part of the anal canal,
  • Surface of the cornea,
  • Inner surface of eyelid.

Found in areas that are moist and subject to varying degrees of abrasion.

43
Q

What functions do non-keratinised stratified squamous epithelium have?

A
  • Protect against abrasion,

- Reduce water loss but remains moist.

44
Q

Which part of the stratified epithelium divides to replace cells lost at the surface?

A

The basal cells of the epithelium.

45
Q

What do the stratified squamous, non-keratinised epithelium of the vagina do?

A

The cells are rich in glycogen, a substance for lactobacilli, which produce lactic acid and thereby maintain a suitably low pH. This helps to destroy non-native bacteria and viruses

46
Q

Where are keratinised stratified squamous epithelium found?

A

Found mainly at the epidermis, Can also be found at the end of the urethra, and oral cavity.

47
Q

What do stratified squamous keratinised epithelium look like?

A
  • contain multiple layers of cells
  • outermost cells are squamous cells that have lost their nuclei and cornified (become ‘squames’ of keratin)
  • outermost dead cells are called the stratum corneum
48
Q

What do the stratum corneum do?

A
  • greatly reduces water loss and ingress
  • prevents ingress of toxins
  • protects against abrasion
  • reduces microbial colonisation
49
Q

What does the epidermis consist of?

A
  • keratinized stratified squamous epithelium

- no blood vessels (avascular)

50
Q

What does the dermis consist of?

A
  • dense irregular connective tissue, consisting of collagen and elastin bundles orientated in all directions’
51
Q

What type of cell makes up majority of the keratinised stratified squamous epithelium and what do they produce?

A

Keratinocytes, which synthesise keratins (fibrous protein) which contributes to the strength of the epidermis.

52
Q

How are the cells of the stratum corneum replaced?

A

Keratinocyte mitosis occurs, mainly in the basal layer.

Daughter cells then move towards the surface differentiating and losing their ability to divide.

53
Q

How long does it take for a keratinocyte to move from the basal layer to the stratum corneum?

A

28-40 days.

54
Q

What is Psoriasis?

A

Epidermal cells replaced quicker than usual.
Transit time from basal layer to stratum corneum is greatly reduced to about 2-4 days. Stratum corneum is therefore produced in abundance as silvery, flaky scales.

Semester 1 - Body Logistics (16 decks)

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