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Med 2024-2028 > Tissues of the Body L2.2 > Flashcards

Tissues of the Body L2.2 Flashcards

1
Q

Define the term “gland”

A

Epithelial cell / collection of epithelial cells involved in SECRETION of a substance

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2
Q

Describe the classification of glands

A
  1. Destination of secretion
    (exocrine (via duct), endocrine (ductless, direcrtly into blood, affect distant tissues).
  2. Means of secretion (types):
    merocrine/eccrine - most glands
    apocrine - mammary gland
    holocrine - sebaceous glands
  3. Morphology: Duct system can be branched (compound - MULTIPLE BRANCHED DUCTS) and unbranched (simple - `SINGLE UNBRANCHED DUCTS). Secretory component can be tubular or acinar (berry like)
  4. Nature of secretion: Serous / Mucous
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3
Q

State an example of a mixed glandular tissue

A

Exocrine and Endocrine
Pancreas

Endocrine part: islet (produces insulin)

Exocrine part: serous acini bear zymogen granules

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4
Q

Give an example of a mixed serous mucous gland

A

Submandibular gland

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5
Q

State an example of a unicellular gland

A

Goblet cells - release mucins

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6
Q

How are mucins detected?

A

PAS staining
Mucins are highly glycosylated
Therefore, hydrophillic
washed away during histological preparations
Residual olisaccharides detcted by PAS staining

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7
Q

Describe what happens to mucins produced from goblet cells

A

Hydrated to form mucus

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8
Q

Look at the diagrm. Given what you know about the nature of goblet cell secretions, explain why goblet cells have an extensive Golgi network

A

Important for glycosylation
Mucins are highly glycosylated proteins

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9
Q

Describe the classification of glands by nature of secretions

A

Mucous / Serous

  1. Mucous glands: Secretions contain mucous (rich in mucins, highly glycosylated polypeptides).
  2. Serous glands: Secretions are watery and protein rich (contain enzymes).
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10
Q

Describe the appearance of mucous glands in H&E staining

A

Stain poorly / less intense than serous glands
Foamy appearance
Because mucus washed away during H&E staining

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11
Q

Describe the appearance of serous glands in H&E stainining

A

Highly eosiniphilic
Stain intensely with haemotoxylin (due to abundant RER)

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12
Q

Describe merocrine secretion

A
  1. Membrane-bound secretory vesicle released from golgi apparatus
  2. Fuses with plasma membrane
  3. Now, it is non-membrane bound and secretes its contents into extracellular space
  4. Plasma membrane becomes transiently larger
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13
Q

Describe transcytosis

A

Endocytosis + secretion combined

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14
Q

Why is the glycosylation of newly-synthesised proteins in the golgi apparatus important?

A

Gives them distinct structure

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15
Q

Describe the cause of cystic fibrosis

A
  1. Mutation in CFTR gene (encodes Cl- channel protein - Cystic Fibrosis Transmembrane Regulator). Mutation prevents expression of CFTR on apical epithelial membranes,
  2. Decrease in Cl- secretion. Increase in intracellular Cl-, retention of Na+ in epithelial cells. Water follows salt, warer reabsorption by osmosis increases
  3. Secreted mucus therefore not adequately hydrared, becomes viscous, difficult for mucus to be moved to oropharynx for swallowing
  4. Results in obstruction in airways, therefore, infections
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16
Q

Describe why “salty sweat” can be seen as a risk factor for cystic fibrosis / confirm diagnosis of cystic fibrosis

A

Absence of CTFR in apical membrane of epithelial cells of sweat duct
Poor reabsorption of Cl-
Suppresses Na+ resorption

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17
Q

Why was Cystic Fibrosis previously known as the fibrocystic disease of the pancreas?

A

During CF, exocrine secretions dehydrated
Thickened, block ducts
Exocrine pancreas inflamed (pancreatitis) + fibrotic
Gut receives insufficient pancreatic digestive enzymes (lipase), leads to malabsorption, and therefore, fatty stools, diarrhoea etc

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18
Q

Major salivary glands

A
  1. Submandibular
  2. Parotid
  3. Sublingual
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19
Q

Table comparing submandibular, parotid and sublingual glands

A
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20
Q

How is saliva release stimulated?

A

Ingestion of food
Parasympathetic innervation

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21
Q

Describe xerostomia

A

Strong sympathatic (when nervous) innervation
Leads to DRY MOUTH

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22
Q

State function of straited ducts in submandibular gland

A

Facilitate ELECTROLYTE RESORPTION

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23
Q

State the epithelium present in the sublingual gland

A
24
Q

Describe the structure and function of the mammary glands

A

Compound (multiple branches), tuboloacinar gland

Myoepithelial cells secrete milk from acini

Mammary glands stimulated by PROLACTIN.
Ducts become more developed after activation due to PROLACTIN, shown in histology

25
Q

Describe the experience of “let down” in the mammary glands

A

When oxytocin released,
myoepithelial cells contract

26
Q

Describe the methods of secretion in mammary glands

A

Apocrine secretion

Lipid droplets move towards plasma membrane
Pushes through plasma membrane
Now, lipid droplets coated with bits of plasma membrane and have apical cytoplasm
The cell membrane becomes transiently smaller. Therefore, needs to be compensated with extra membrane, this is done by SER

Merocrine secretion

other milk constituents - proteins, minerals, lactose

27
Q

State types of sweat glands and their differences

A
  1. Merocrine / Eccrine
  2. Apocrine

Merocrine distrobuted throughout body
Aporcrine develop during puberty in
- axillae (arm pits)
- areola of nipples
- genital + perianal regions

28
Q

Describe the role of apocrine glands in body odour

A

Scent glands
Sweat secretion produced rich in protein
Protein easily metabolised by bacteria (this is what gives the smell)

29
Q

State the method of secretion used my apocrine sweat glands

A

Merocrine secretion
(despite their name, apocrine sweat glands function via merocrine secretion, only called apocrine to differntiate between normal ones and ones that develop at puberty)

30
Q

State the method of secretion of merocrine glands

A

Merocrine secretion

31
Q

Is the thyroid gland endocrine or exocrine?

A

Endocrine

32
Q

Describe the position of the thyroid gland

A

Anterior (in front) + inferior to larynx (below)

33
Q

State the name of the cells present in the thyroid glands

A

Thyrocytes

34
Q

State the role of thyrocytes

A

Active thyrocytes produce cuboidal epithelium producing
T3 - Triiodothyronine
T4 -Thyroxine

These hormone regulate basal metabolic rate

35
Q

State the role of parafollicular cells

A

C cells
Secrete calcitonin
Slows down bone turnover, reducing plasma calcium

36
Q

Histology showing simple cuboidal epithelium of thyroid gland

A
37
Q

Describe the control and synthesis of thyroid hormones

A
  1. Controlled by TSH (thyroid stimulating hormone, anterior pituitary) (ENDOCRINE CONTROL)

Thyroid hormones T3 + T4 synthesised as follows:

  1. Thyroglobulin (tyrosine rich glycoprotein) synthesised by thyrocytes (ER of thyrocytes) (thyroid follicular cells), release it into colloid by exocytosis
  2. Tyrosine on thyroglobulin undergoes iodination at one or two positions:
    - di-iodinated tyrosine residue is conjugated with a mono-iodinated tyrosine residue to form pre-t3
    -di-iodinated tyrosine residue is conjugated with mono-iodinated tyrosine residue to form pre-T4
  3. Modified thyroglobulin edocytosed during TSH stimulation. Undergoes proteolytic cleavage (in LYSOSOMES)to produce mature T3 and T4
  4. T3 + T4 released from cells via exocytosis + enter blood stream, transported by help of transport proteins (e.g. albumin)
38
Q

State the most abundant thyroid hormone and explain why it is most abundant

A

T4
More stable (because less active than T3)

T3 + T4 BIND TO SAME RECEPTORS

39
Q

Describe how T4 can be converted to T3

A

Removal of iodine molecule from T4
Deiodinase enzyme

40
Q

Describe what can happen if further iodine molecules are removed from T3?

A

Inactive forms (rT3, T2)

41
Q

How does the body respond to high thyroid hormone levels?

A

Inhibits release of TSH
(-ve feedback)

42
Q

Describe the structure and location of the parathyroid gland

A

4 small glands on posterior surface of thyroid.

43
Q

State the 2 cells present in the parathyroid gland

A

Cheif cells / principal cells
Oxyphil cells

44
Q

Which cells secrete parathyroid hormone?

A

Chief cells / principal cells

45
Q

State functions of PTH

A

Stimulates bone resoroption by osteoclasts
Raises blood calcium levels

46
Q

State the role of the parathyroid gland

A

Regulates calcium levels

47
Q

State the function of oxyphill cells

A

Unclear

48
Q

Describe the location of the adrenal glands

A

perirenal adipose
superior poles of each kidney

49
Q

Histology of adrenal gland

A

Adrenal CORTex - 3 laters, secretes CORTicosteroid hormones

Medulla - secretes adrenaline + noradrenaline

50
Q

State the role of the outer cortex of adrenal gland

A

Fibrous
Provides protection
Consists of
1. Zona glomerulosa - produces mineralcorticoids (e.g. aldosterone)

  1. Zona fasciculata -produces glucocorticoids (cortisol)
51
Q

Is the Zona Reticularis located in the inner or outer cortex?

A

Inner

52
Q

State the role of the zona reticularis

A

Produces weak androgens

53
Q

State the role of the medulla

A

Adrenaline
Noradrenaline

54
Q

State the function of aldosterone

A

Regulates Na+ uptake by renal tubules

55
Q

State the role of cortisol

A

Regulates carb metabolism

56
Q

State the role of adrenaline / noradrenaline

A

Catecholamines
Stress response

Med 2024-2028 (56 decks)

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