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Body Logistics > Glands > Flashcards

Glands Flashcards

1
Q

Define ‘gland’

A

An epithelial cell (or aggregate of cells) specialised for secretion.

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2
Q

What are the 2 types of glands?

A

Endocrine:

  • Ductless
  • Secrete hormones directly into blood
  • ALL epithelial cells secrete hormones in the gland
  • (e.g. pituitary, thyroid)

Exocrine:

  • Ducted
  • Secrete enzymes / lubricants
  • Only cells at APEX of duct secrete
  • (e.g. salivary, sweat)
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3
Q

What are the gland classifications by secretion method?

A
  1. MEROCRINE:
    - Fusion of vesicles with apical membrane (exocytosis)
  2. APOCRINE:
    - PARTIAL loss of cytoplasm
    - Pinched off section of cell is the secretion
  3. HOLOCRINE:
    - TOTAL loss of cytoplasm
    - Mature cell dies and becomes the secretion
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4
Q

Describe the process of merocrine secretion

A
  • Exocytosis
  • Membrane bound compartment approaches cell
  • Fuses with plasma membrane
  • Contents dispersed by diffusion
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5
Q

Describe the process of apocrine secretion

A
  • Non membrane bound structure approaches cell
  • Pushes up apical membrane
  • Layer of cytoplasm drapes around droplet
  • Membrane surrounding droplet pinches off
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6
Q

Describe the process of holocrine secretion

A
  • Cell disintegrates
  • Releases contents
  • Discharge of whole cell into extracellular space
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7
Q

State the 3 control mechanisms for hormone release

What kind of feedback loop do these use?

A
  • Neural (nervous system)
  • Hormonal (hypothalamus)
  • Humoral (plasma)

Negative feedback loops
- Secretory product inhibits own secretion

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8
Q

Define glycosylation

A

Attachment of sugars, by enzymes, to proteins and lipids to form glycoproteins and glycolipids

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9
Q

Describe the process of glycosylation

A
  • Vesicles from ER travel to golgi cis face
  • Vesicle fuses and empties contents into lumen
  • Proteins and lipids travel through golgi
  • Sugar molecules added
  • New glycolipids and glycoproteins tagged
  • Packed in secretory vesicles at trans face
  • Fuse with plasma membrane and empty outside cell
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10
Q

What are the 2 pathways for merocrine secretion?

A

REGULATED:

  • Secretory granules accumulate in large vesicles
  • Released by exocytosis on stimulation
  • Requires Ca2+ ions

CONSTITUTIVE:

  • Secretory product packaged in small vesicles
  • Continuously released to cell surface
  • Repopulates plasma membrane with plasma proteins
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11
Q

Define phagocytosis

A

Process by which cells engulf other cells or particles

e.g. macrophages and immune cells engulfing pathogens or infected cells

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12
Q

State the role of glycosylation in the golgi apparatus

A
  1. Aid protein folding
  2. Prevent protein / lipid digestion by intracellular enzymes
  3. Cell recognition (blood types)
  4. Role on cell to extracellular matrix attachment
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13
Q

Where in the cell are proteins synthesised?

A

Ribosomes (bound to RER)

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14
Q

Where in the cell are steroid hormones synthesised?

A

SER

Smooth endoplasmic reticulum

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15
Q

Briefly outline the negative feedback loop for neural control of hormone release

A

Nervous system > endocrine gland > target cells > action

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16
Q

Briefly outline the negative feedback loop for humoral control of hormone release

A

Change in substance level in plasma > endocrine gland > target cells > action

17
Q

Briefly outline the negative feedback loop for hormonal control of hormone release

A

Hypothalamus > anterior pituitary > peripheral endocrine gland > target cells > action

18
Q

Describe the processes of endocytosis and exocytosis.

A

Endocytosis:

  • Bulk transport into cell
  • Cell membrane pouch surrounds particles outside
  • Vesicle formed
  • Contents released into cytoplasm

Exocytosis:

  • Bulk transport out of cell
  • Vesicle moves to cell membrane - fuses
  • Contents secreted as membrane smoothes.
19
Q

Describe the location, structure and function of the thyroid gland

A

Location:

  • Anterior to trachea (2 lobes)
  • Butterfly shape

Secretes:

  • Thyroxine (T4)
  • Triodothyroinine (T3)
20
Q

Describe the location, structure and function of the parathyroid gland

A

Location:

  • Posterior surface of thyroid gland
  • 4 glands, 2 pairs
  • Lots of adipose tissue

Function:

  • Monitor plasma calcium concentrations
  • Classic negative feedback loop

Secretes:
- Parathormone (PTH) - Ca2+ resorption

21
Q

Describe the location, structure and function of the adrenal glands

A 
Location:
- Top of each kidney
- 2 sections 
(medulla = inner, cortex outer)
- Right = pyramid, left = half moon

MEDULLA
Chromaffin cells
- Adrenaline 80%
- Noradrenaline 20%

CORTEX 3 zones: - (Salt, Sugar, Sex)

Zona Glomerulosa
- Mineralocorticoids

Zona Fasiculata
- Glucocorticoids

Zona Reticularis

  • Glucocorticoids
  • Androgens
22
Q

Describe location, structure and function of pancreas

A

Location:
- Left of and behind stomach

Structure:

  • 99% Exocrine 1% Endocrine
  • Intercalated ducts
  • Acinar glands (grouped into lobules)

Secretes:
EXOCRINE (Acini)
- Digestive enzymes and HCO3-

ENDOCRINE (Islet of Langerhans)

  • Glucagon (alpha)
  • Insulin (beta)
  • Somatostatin (delta) inhibits insulin/glucagon secretion
23
Q

Describe the location, structure and function of pituitary gland

A

Location:
- Base of brain
- 2 lobes (Anterior / Posterior)
(Neurosecretory axons from hypothalamus extend directly into PP)

Anterior (epithelial) secretes:

  • Growth factor hormones
  • TSH, ACTH, FSH, LH, GH, MSH, Prolactin

Posterior (nerve) secretes:

  • Antidiuretic hormone (ADH) - kidney water resorption
  • Oxytocin - lactation / labour
24
Q

Which part of the brain is central to homeostasis?

A

Hypothalamus

25
Q

What does the hypothalamus deal with?

A
  1. Thermoregulation
  2. Plasma osmolality
  3. Heart rate and BP
  4. GI Tract regulation (feeding, satiety)
  5. Circadian rhythms
  6. ANS stimuli
  7. Emotion / mood
  8. Lactation
26
Q

What does the hypothalamus produce?

A

To POSTERIOR PITUITARY via NERVES:

  • Vasopressin (ADH)
  • Oxytocin

To ANTERIOR PITUITARY via HYPOTHALAMO-HYPOPHYSEAL PORTAL SYSTEM (blood):
- 6 hormones

27
Q

Define ‘stress response’

A

A complex range of responses to aversive stimuli, involving the endocrine, nervous and immune systems (to maintain homeostasis).

28
Q

Levels in HYPOthyroidism and HYPERthyroidism

A

HYPOthyroidism (Hashimoto’s)

  • Low T3 / T4
  • High TSH

HYPERthyroidism (Graves Disease)

  • High T3/T4
  • Low TSH

Negative feedback:
Low T3/T4 > pituitary releases TSH
High T3/T4 > pituitary less TSH

29
Q

How are glands classified?

A
  • Tubular (tube)
  • Acinar (berry)
  • Simple (single duct)
  • Compound (multiple ducts)
  • Serous (watery / enzymes)
  • Mucous (mucins)
30
Q

Secretion of parotid salivary glands

A
  • Serous acini
DUCTS:
- Intercalated
> Striated
> Interlobar
> Principle
31
Q

Secretion of salivary submandibular glands

A
  • Serous / mucous / mixed (demilune) acini
32
Q

Structure and function of myoepithelial cells

A
  • Contain actin > Contract

- Contraction squeezes secretion into / along duct

Body Logistics (7 decks)

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