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Body Logistics > Epithelial Tissues And Exocrine Glands > Flashcards

Epithelial Tissues And Exocrine Glands Flashcards

1
Q

What does a mucous membrane line?

A

MUCOUS MEMBRANES line certain internal tubes which open to the exterior.
i.e. the alimentary tract
the respiratory tract
the urinary tract
(these mucosae bear mucus-secreting cells to varying degrees)

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2
Q

What 3 layers dos a mucous membrane consist of?

A

A MUCOUS MEMBRANE consists of:
- an epithelium (type depends on site) lining the lumen of a tube.
- an adjacent layer of connective tissue often referred to as the
lamina propria (literally ‘one’s own layer’).
- in the alimentary tract, a third layer consisting of smooth muscle
cells, referred to as the muscularis mucosae.

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3
Q

What is a serous membrane and what do they line?

A

SEROUS MEMBRANES are thin, two-part membranes which line certain closed body cavities (spaces which do not open to the exterior). They envelop the viscera.

  • They line the peritoneum……….which envelops many abdominal organs.
  • the pleural sacs……..which envelop the lungs.
  • the pericardial sac…..which envelops the heart.
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4
Q

What do serous membranes secrete?

A

These serous membranes (or serosae) secrete a lubricating fluid which promotes relatively friction-free movement of the structures they surround.

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5
Q

What does a serous membrane consist of?

A

A SEROUS MEMBRANE consists of:
- a simple squamous epithelium (mesothelium) which secretes a
watery lubricating fluid.
- a thin layer of connective tissue which attaches the epithelium
to adjacent tissues (also carries blood vessels and nerves).

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6
Q

When do many organs become surrounded by a serous membrane?

A

During embryonic development the heart, lungs, and gut develop next to a bag-like cavity into which they invaginate. So they each become surrounded by serous membrane.
(NB - they do not lie within the serous cavity itself, but are surrounded by it).
See analogy………

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7
Q

What is the outer “wall” or a serous membrane called?

A

Parietal serosa

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8
Q

What is the inner wall of a serous membrane called?

A

Visceral serosa

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9
Q

What lies in the serous cavity and what is its function?

A

Lubricating fluid; allows movement

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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.

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11
Q

Name some surfaces with epithelial linings

A

Exterior surface:
skin

Interior spaces opening to exterior:
gastrointestinal tract
respiratory tract
genitourinary tract

Interior spaces which do not open to the exterior:
pericardial sac 
pleural sacs 
peritoneum 
blood vessels 
lymphatic vessels
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12
Q

Name some terms to classify the nature of the epithelial layer

A

Simple
Stratified/compound
Pseudostratified

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13
Q

Name some terms to classify the shape of epithelial cells

A

Squamous
Cuboidal
Columnar
Transitional

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14
Q

What is simple epithelium?

A

One cell layer thick

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15
Q

What is stratified/compound epithelium?

A

More than one cell layer thick

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16
Q

What is the basement membrane?

A

Basement membrane is the name given to the thin, flexible, acellular layer which lies between epithelial cells and the subtending connective tissue.

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17
Q

What is the function of the basement membrane

A

The basement membrane serves as a strong flexible layer to which epithelial cells adhere. It also serves as a cellular and molecular filter.

The degree to which malignant cells penetrate basement membrane is highly relevant to prognosis (see Mechanisms of Disease Unit).

NB: the terms basement membrane and basal lamina are used
inconsistently in the literature.

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18
Q

Define simple squamous epithelium

A

A single layer of thin squamous cells

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19
Q

Give examples of vessels which are lined by simple squamous epithelium

A

Blood vessels, lymphatic vessels

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20
Q

What is the name given to the simple squamous epithelium lining all vascular elements?

A

ENDOTHELIUM

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21
Q

What is mesothelium?

A

The name given to simple stratified epithelium lining the pleural sac, the pericardial sac and the peritoneum

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22
Q

What is the function of endothelium?

A

Endothelium can exchange gasses and nutrients, allow certain blood cells to enter the tissues, and regulate platelet coagulation.

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23
Q

Name 4 functions of simple squamous epithelium

A

1) Lubrication (pericardium, pleura, peritoneum/viscera)
Secretion of fluid can be excessive. e.g.:
- hydrocoele around testis – accumulation of clear serous fluid between visceral and parietal layers of tunica vaginalis
- excessive fluid in pleural space around lungs, requiring drainage (see Respiratory system lecture)

2) Gas exchange (Type 1 pneumocytes of pulmonary alveoli)
3) Barrier (Bowman’s capsule)
4) Active transport by pinocytosis (mesothelium & endothelium)

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24
Q

What type of epithelium lines a pancreatic duct?

A

Simple cuboidal

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25
Q

What type of epithelium line thyroid gland follicles?

A

Simple cuboidal

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26
Q

What do epithelial cells in the thyroid gland synthesise?

A

The epithelial cells synthesise thyroxine, store it in colloid, and transport it to the bloodstream.

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27
Q

What type of epithelium lines the collecting ducts of the kidneys?

A

Simple cuboidal

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28
Q

What are 4 functions of simple cuboidal epithelium?

A

Absorption & Conduit (exocrine glands)
Absorption & secretion (kidney tubules)
Barrier/covering (ovary)
Hormone synthesis, storage and mobilisation (thyroid)

29
Q

Describe simple columnar epithelium

A

Simple columnar: a single layer of cells, whose heights are significantly greater than their widths.

30
Q

Give an example of where simple columnar epithelium can be found?

A

Stomach lining and gastric glands

Small intestine and colon e.g. Crypts of liberkuhn

31
Q

What are microvilli

A

Projections on the surface of cells which increase the surface area available for absorption

32
Q

Name some functions of simple columnar epithelium

A

Absorption (small intestine and colon, gallbladder)
intestine and colon)
Secretion (stomach lining & gastric glands, small Lubrication (small intestine and colon)

33
Q

Describe pseudostratified epithelia

A

Those in which all cells make contact with the basement membrane, but not all cells reach the epithelial surface. This results in nuclei lying at different levels, giving a false impression of multiple layers of cells.

34
Q

Name some locations of pseudostratified epithelium

A

Lining of nasal cavity, trachea and bronchi

35
Q

What are some functions of pseudostratified epithelium?

A 
Secretion and conduit (respiratory tract, ductus deferens)
Mucus secretion (respiratory tract) particle trapping and removal (respiratory tract)
36
Q

Describe stratified squamous epithelia

A

Multiple layers of camels, the outermost of which are thin squamous cells

37
Q

Where is stratified squamous non-keratinised epithelium found?

A 
Oral cavity
Oesophagus
Vagina
Part of anal canal
Surface of cornea
Inner surface of eyelid

Moist surfaces, prone to abrasion

38
Q

What are functions of stratified squamous non-keratinised epithelium?

A

Protection against abrasion

Reduces water loss but remains moist

39
Q

Why are stratified squamous non-keratinised cells of the vagina rich in glycogen

A

Glycogen is a substrate for lactobacilli which produce lactic acid and thereby maintain a suitably low pH

40
Q

Describe stratified squamous keratinised epithelium

A

Stratified squamous keratinized epithelium contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and
cornified (i.e. become ‘squames’ of keratin).

41
Q

What is the stratum corneum and what are its functions?

A 
The outermost dead cells of the epithelium are collectively called the stratum corneum. 
This layer
- greatly reduces water loss and ingress
- prevents ingress of toxins
- protects against abrasion
- reduces microbial colonisation.
42
Q

What is the primary site of stratified squamous keratinised epithelium?

A

The epidermis of the skin

43
Q

Is epidermis vascular or avascular?

A

Avascular

44
Q

Describe the dermis

A

Dense irregular connective tissue consisting of collagen and elastin bundles orientated in all directions.

45
Q

What is the main cell type which makes up stratified squamous keratinised epithelium?

A

Keratinocytes

46
Q

What are the 4 layers of the epidermis?

A
  • horny layer (STRATUM CORNEUM)
  • GRANULAR LAYER (stratum granulosum)
  • prickle cell layer ( stratum spinosum)
  • BASAL LAYER (stratum basalt)

(Common terms = capital)

47
Q

Where does keratinocyte mitosis occur primarily, and what then happens to the keratinocytes?

A

Basal layer

Daughter keratinocytes then move upwards, differentiating and losing their ability to divide

48
Q

What are keratins?

A

Keratinocytes synthesise keratins (fibrous proteins) which contribute to the strength of the epidermis. Keratins are also the main constituents of hair and nail, and animal horns.

49
Q

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

A

28-40 days

However in diseased like psoriasis the transit time is reduced

50
Q

What are melanocytes?

A
  • occur at intervals (1:8 of basal layer of epidermis)
  • difficult to see histologically without special stains
  • produce melanin, the main pigment that gives the skin its colour
  • produce more melanin but are not increased in number in black or tanned skin

Same ratio of melanocytes to keratinocytes in all skin colours, it’s just the amount of melanin. Paler skin - melanocytes destroyed faster

51
Q

What are Langerhans cells?

A
  • difficult to see histologically without special stains
  • highly specialised capacity to present antigens to T lymphocytes
  • mediate immune reactions e.g. Allergic contact dermatitis
52
Q

Where are melanosomes found?

A

Mature melanosomes containing melanin are transferred to neighbouring keratinocytes by pigment donation, involving phagocytosis of the tips of the dendritic processes

53
Q

Where is stratified squamous keratinised epithelium found?

A

Surface of the skin

Limited distribution in oral cavity

54
Q

Name some functions of stratified squamous keratinised epithelium

A
  • protection against abrasion and physical trauma
  • prevention of water loss
  • prevention of microbial ingress
  • shielding against UV light damage
55
Q

Describe transitional epithelium

A

Surface ce;;s vary in shape from columnar/cuboidal to flattened

56
Q

Where is transitional epithelium found?

A

Urinary tract; renal calyces, ureters, ladder, urethra

57
Q

Name some functions of transitional epithelium

A

Protection of underwing tissue from toxic chemicals

58
Q

What is a gland

A

An epithelial cell or collection of cells specialised fo secretion
The secretion can be into the bloodstream or onto an epithelial surface (i.e. Of the gut, respiratory or reproductive tracts)

59
Q

What is an adenocarcinoma?

A

A malignant growth derived from glandular cells of epithelial origin

60
Q

Define exocrine glands

A

Glands with ducts which secrete onto an epithelial surface (e.g. Salivary glands and the breast)

61
Q

Define endocrine glands

A

Ductless glands which secrete directly into the bloodstream? (E.g. Thyroid and adrenal glands)

62
Q

Can glands be both endocrine and exocrine?

A

Yes, e.g. The pancreas

63
Q

Are glands unicellular or multicellular?

A

Can be either

64
Q

What are goblet cells?

A

Unicellular exocrine glands which reduces and secretes mucus into the respiratory and intestinal tracts

65
Q

What is the name given to the endocrine tissue of the pancreas?

A

Islets of Langerhans

66
Q

What is the name given to the exocrine tissue of the pancreas?

A

Acini

67
Q

Describe the problems associated with mucus in cystic fibrosis

A

Insufficiently hydrated mucus is formed in the respiratory tract and gut with resultant pathologies

68
Q

What is an acinus?

A

The secretory unit of many exocrine glands

69
Q

What are myoepithelial cells?

A

Cells around each acinus which constrict simultaneously to assist the secretion of:

  • milk from the lumens of the acini in the breast
  • unmodified sweat of eccrine sweat glands towards the duct

Body Logistics (15 decks)

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