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BL - SEM1 > Session 4: Endocrine glands & tissues > Flashcards

Session 4: Endocrine glands & tissues Flashcards

1
Q

What are epithelial cells with muscle function called? What is their function? Give an example.

A

Myoepithelial cells
Help eject secretions from the duct by contracting
Eg contract so that ducts can secrete milk from breasts

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2
Q

Where are simple branched alveolars found?

A

Where hair is present

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3
Q

Give an example of glands with simple branched alveolar branching.

A

Sebaceous glands

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4
Q

What are the types of epithelial cells in exocrine glands? (2)

A

Cells lining the ducts & cells that make secretory products

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5
Q

What is the difference between simple duct structure & compound duct structure?

A

simple duct structure = duct does not branch
compound duct structure = duct branches

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6
Q

Give an example of a gland with a simple tubular structure.

A

Intestinal glands

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7
Q

Give an example of a gland with a simple BRANCHED tubular structure.

A

Stomach glands

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8
Q

Give an example of a gland with a compound tubular structure.

A

duodenal glands of small intestine

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9
Q

Give an example of a gland with a compound alveolar structure.

A

mammary glands

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10
Q

Give an example of a gland with a compound tubuloalveolar structure.

A

salivary glands

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11
Q

What is a gland?

A

an epithelial cell or an aggregate of epithelial cells that are specialised for secretion of a substance.

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12
Q

What are endocrine glands?

A

Ductless glands that secrete hormones directly into the blood to reach parts of the body

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13
Q

Give examples of endocrine glands.

A
  • Pituitary gland: anterior - ATCH, FSH, TSH, LH, prolactin, somatotropin. Posterior: ADH, oxytocin
  • Thyroid gland - T3 & T4, calcium metabolism, calcitonin
  • Parathyroid gland - parathyroid hormone, calcium hormone
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14
Q

Which cells secrete hormones in endocrine cells?

A

All cells secrete hormones

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15
Q

What are exocrine glands?

A

Ducted glands that secrete enzymes & lubricants into a location/region through a duct

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16
Q

Give examples of exocrine ducts.

A
  • Mammary glands
  • Salivary glands
  • Pancreas
  • Sweat glands
  • Sebaceous glands
  • Larynchymal glands
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17
Q

What type of substances do exocrine glands release?

A

Enzymes and lubricants

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18
Q

What type of substances do endocrine glands release?

A

Hormones eg T4, T3, ADH

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19
Q

Which cells of exocrine glands secrete products?

A

Only cells at the apex of duct, parenchymal cells

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20
Q

What are the 3 modes of secretion?

A

Merocrine, apocrine and holocrine secretions

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21
Q

What is a merocrine gland?

A

Fusion of vesicles with apical membrane eg endocrine glands of pancreas

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22
Q

What is an apocrine gland?

A

Partial loss of cytoplasm eg lactating mammary gland and sweat glands on skin

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23
Q

What is a holocrine gland?

A

Complete loss of cytoplasm or cell eg sebaceous gland in skin, tarsal gland in eyelid

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24
Q

What is merocrine secretion? Explain regulated & constitutive secretion.

A
  • Form of exocytosis

Regulated secretion:
- secretory granules accumulate in large vesicles & released by exocytosis upon receiving a Ca2+ signal
- Vesicles fuse with the plasma membrane
- Active process, uses energy & requires Ca2+
- Cargo released to extracellular space

Constitutive secretion:
- secretory products packaged into small vesicles & continuously released to cell surface
- used to repopulate plasma membrane with plasma proteins

25
Q

What is apocrine secretion?

A

Non-membrane bounded structure (e.g. lipid) approaches cell surface, makes contact and pushes up apical membrane, thin layer of apical cytoplasm drapes around droplet, membrane surrounding droplet pinches off from cell

26
Q

What happens to the membrane in apocrine secretion?

A
  • Plasma is temporarily smaller
  • Membrane added to regain original area
27
Q

What occurs during the neonatal period (secretion)?

A
  • Only fats are secreted by apocrine secretion
  • Proteins made in rough endoplasmic reticulum & free ribosomes are packed in vesicles and released by merocrine secretion
28
Q

What occurs during lactation? (secretion)

A

Apocrine secretion releases both fats and proteins

29
Q

Describe the process of holocrine secretion in 5 steps.

A
  1. Secretory cell fills up with secretory granules
  2. Cell disintegratees and dies
  3. Plasma membrane breaks & contents are released
  4. Cell is discharged into extracellular space
  5. Dead cells are replaced by mitosis of basal cells
30
Q

Give an example of a gland that undergoes holocrine secretion

A

Sebaceous gland

31
Q

How does endocytosis work?

A

Engulfing of molecules inside the cell via vesicle formation

There are 2 types: phagocytosis and pinocytosis

32
Q

Describe how endocytosis and exocytosis combine to give transepithelial transport

A
  1. Material is endocytosed at one surface
  2. Transport vesicle transports across cytoplasm
  3. Material is exocytosed at opposite surface
33
Q

Describe phagocytosis and pinocytosis.

A

Phagocytosis: phagocytes engulf cells and particle (immune cells)
Pinocytosis: liquid droplets are ingested by cells (all cells esp SMCs)

34
Q

What is glycosylation?

A

Covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids

35
Q

What is the importance of glycosylation?

A
  • Aid protein folding
  • Prevent protein digestion by intracellular proteases
  • Prevents lipid digestion by intracellular lipases
  • Cell recognition
  • Role in cell to ECM attachment
36
Q

What is a humoral stimulus?

A

control of hormone release in response to changes in extracellular fluids eg blood or ion concentration in the blood. Eg: rise in blood glucose levels triggers the pancreatic release of insulin.

37
Q

What is a neutral stimulus?

A

the nervous system directly stimulates endocrine glands to release hormones. Eg neural stimulus is the only stimulus used in salivary (exocrine) gland secretion
- Neurocrine communication = nerve cell releases hormones in blood and acts on target cell

38
Q

What is a hormonal stimulus?

A

release of a hormone in response to another hormone. Eg hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland => stimulates anterior pituitary to release hormones that regulate hormone production by other glands

39
Q

Describe the process of base gland formation (before forming into exocrine/endocrine gland).

A
  1. Growth signal received
  2. Proliferation of daughter cells occurs and extracellular protein degradation enzymes are produced
  3. Epithelial cells invade the space created.
40
Q

Describe the formation of endocrine glands in 3 steps.

A
  1. Produce angiogenic factors to stimulate blood vessel growth in and around epithelial cells
  2. Link to mother cells broken through apoptosis
  3. No branching occurs
41
Q

Describe the formation of exocrine glands in 3 steps (after first process)

A
  1. Central cells die off to produce a duct (canalicularisation)
  2. Link to mother cells remain
  3. Significant amount of branching
42
Q

How does branching occur?

A

Immature fibroblasts release FGF10

2 different fates:

  1. Tubule elongation: Growth factor 1 is active & Growth factor 2 is inactive
  2. Tubule branching: Growth factor 1 is inactive & Growth factor 2 is active

Elongation and branching stopped by Sonic the Hedgehog (Shh)

43
Q

Describe how endocrine glands are derivatives of epithelial cells.

A

Formed by invagination from an epithelial sheet and initially have ducts connecting them to the free surface of the epithelial sheet.
During embryonic development, they will lose their ducts and thus are called ductless glands => NO FREE SURFACE – ENDOCRINE GLANDS

44
Q

Describe the portal circulatory system.

A
  • It involves blood passing through 2 sets of capillary beds (as opposed to 1 in normal) before returning to the heart to be oxygenated
  • Blood from the first set of capillaries collects in the portal veins which then branch again to supply a capillary network to a second location before entering veins to the heart.
45
Q

Give an example of a type of portal system.

A

Hypothalamic-hypophyseal portal system
- connects hypothalamus to anterior pituitary

46
Q

What is the exocrine function of the pancreas? Which 7 hormones does it release?

A

Digestion
It releases:
- Trypsinogen which is converted to trypsin (protein)
- Chymotrypsinogen which is converted to chymotripsin (protein)
- Lipase (lipids)
- Amylase (carbohydrates)
- Ribonuclease
- Deoxyribonuclease
- Gelatinase

47
Q

Which part of the pancreas has the exocrine function?

A

The acini

48
Q

Which part of the pancreas has the endocrine function?

A

The islets of Langerhans

49
Q

What is the endocrine function of the pancreas? Which 8 hormones does it release?

A

Regulation of blood sugar and glandular secretion

  • Glucagon - alpha cells (catabolises glycogen to glucose)
  • Insulin - beta cells (uptake and storage of glucose)
  • Somatostatin (inhibits insulin & glucagon secretion)
  • Pancreatic polypeptide (inhibits bile, pancreatic enzyme & bicarbonate secretion)
  • Vasoactive intestinal peptide
  • Secretin
  • Ghrelin
  • Gastrin
50
Q

What are 3 functions of calcitonin?

A
  • Monitors plasma calcium & decrease it (counteracts PTH)
  • Inhibits osteoclast activity in bone
  • Inhibits renal calcium & phosphate reabsorption in tubular cells so more calcium & phosphate excreted
51
Q

Describe the structure of the thyroid gland.

A
  • Located at base of the neck
  • Lateral lobes connected by isthmus
  • Made up of thyrocytes which produce & store T3 & T4
52
Q

What is the function of T3 and T4?

A

Regulate how the body uses energy - energy metabolism

53
Q

Which hormones does the thyroid gland secrete? What type of gland is it?

A

T3, T4 and calcitonin
Endocrine gland

54
Q

Describe the structure of the parathyroid gland.

A

4 nodular structures are located on the dorsum of the thyroid at each of its 4 corners.

55
Q

Which hormone does the parathyroid hormone release? What is its function?

A

Parathyroid hormone (PTH) monitors serum calcium and is secreted to stimulate the release of calcium when it is low.

56
Q

Which hormones do the adrenal glands secrete?

A
  • Glucocorticoids (cortisol) - released during stress response, regulates blood glucose & anti-inflammatory response
  • Mineralocorticoids (aldosterone) - maintains salt and water balance (important for BP). Helps kidneys conserve salt
  • Catecholamines (adrenaline, noradrenaline & dopamine) - responsible for physiological characteristics of stress response -increase HR, BP, breathing, dilated pupils, flushed/pale.
57
Q

What are the 3 layers of the cortex of adrenal glands?

A
  • zona glomerulosa (outer) - aldosterone
  • zona fasciculata (middle) - glucocorticoids
  • zona reticularis (inner) - androgen precursors
58
Q

What are the cells found in the medulla of adrenal glands? What are they?

A

Chromaffin cells are modified neurons equivalent to post-synaptic neurons.

BL - SEM1 (7 decks)

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