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Body Logistics Revision > 5 - Glands > Flashcards

5 - Glands Flashcards

1
Q

What is a gland?

A

An aggregate of epithelial cells specialised for the secretion of a substance

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2
Q

What are the two ways that glands can be classified?

A
  • By their structure (endocrine/exocrine)

- By the mechanism of product release (merocrine, apocrine, holocrine, cytocrine)

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3
Q

What is an endocrine gland? Give some examples.

A

Secrete hormones into the blood, which act at distant parts of the body
E.g.
- Pituitary gland - ACTH, LH, FSH, TSH, prolactin, somatotrophin, vasopressin, oxytocin
- Thyroid gland - T3/T4 in metabolism & calcitonin (Ca2+ homeostasis)
- Parathyroid gland - parathyroid hormone (Ca2+ homeostasis)

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4
Q

What is an exocrine gland? Give some examples.

A
  • Secrete enzymes or lubricants through ducts
    E.g.
  • Salivary gland
  • Pancreas - amylase, trypsin, lipase
  • Mammary
  • Sweat glands - secrete sweat onto skin
  • Sebaceous glands - secretes sebum onto the skin to protect from pathogens
  • Lachrymal glands - moisten the eye and makes lysozyme
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5
Q

How are glands developed in utero?

A
  1. Epithelial cells proliferate in response to growth signal and produce extracellular protein degradation enzymes
  2. Epithelial cells invade the space they create

Exocrine glands - central cells die off to make a duct (canalicularisatrion)
Endocrine glands - angiogenesis around the epithelial cells, link to ‘mother’ cells is broken by apoptosis (independent from epithelial surface)

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6
Q

What is the difference between simple and compound duct structure?

A

Simple - duct does not branch

Compound - duct branches

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7
Q

What are the different shapes of gland ducts? Give an example for each.

A
  • Simple tubular - intestinal glands
  • Simple branched tubular - stomach (gastric) glands
  • Simple alveolar - none in humans
  • Simple branched alveolar - sebaceous glands
  • Compound tubular - duodenal glands of small intestine
  • Compound alveolar - mammary glands
  • Compound tubuloalveolar - salivary glands
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8
Q

What are the two functions of cells in exocrine glands?

A
  1. Cells lining the ducts

2. Cells making secretory products

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9
Q

What is a myoepithelial cell of a duct?

A
  • Cells at secretory ends of ducts with features of both epithelial and smooth muscle cells
  • Eject secretions from ducts
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10
Q

What are the two types of acini in salivary glands?

A
  • Serous

- Mucous

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11
Q

What is merocrine secretion?

A

Fusion of vesicles with apical membrane (form of exocytosis)

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12
Q

What is apocrine secretion?

A

Partial loss of the cytoplasm

  • E.g. lactating mammary gland, sweat glands in axilla
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13
Q

What is holocrine secretion?

A

Complete loss of cytoplasm or cell

E.g. sebaceous gland in skin and tarsal glands in eyelid

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14
Q

What is cytocrine secretion?

A

Cells released as a secretion

E.g. spermatozoa in the testis

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15
Q

What are the 2 types of merocrine secretion?

A
  • Regulated - vesicles released on stimulation

- Constitutive - vesicles continuously released

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16
Q

How does regulated merocrine secretion occur? Give a clinically relevant example of this.

A
  1. vesicle migrates to cell surface along microtubules
  2. in presence of Ca2+ ions, vesicle fuses with plasma membrane due to SNARE complex and synaptotagmin
  3. cargo released by exocytosis

E.g. release of insulin from pancreatic B-cells

17
Q

Give an example of apocrine secretion.

A

In the breast:

  • fats are secreted by apocrine secretion in neonatal period
  • during lactation both fats and proteins are released by apocrine secretion
18
Q

Give an example of holocrine secretion.

A

Sebaceous glands:

  • secretory cell gradually fills with secretory granules
  • cell dies and plasma membrane ruptures, releasing contents
  • Dead cells replaced by mitotic division of those below
19
Q

What is the role of the golgi apparatus in secretion?

A
  • Newly synthesised proteins are transferred from the RER to the golgi in vesicles
  • The golgi chemically modifies them and targets them to the correct locations
20
Q

What are the cis and trans faces of the golgi apparatus?

A

Cis - faces the RER
Trans - faces the plasma membrane

Material flows cis –> trans

21
Q

What is glycosylation? How is it different from glycation?

A

Covalent attachment of sugars BY ENZYMES to proteins/lipids, forms glycoproteins/glycolipids

Glycation - same but without the presence of enzymes

22
Q

What is the role of glycosylation?

A
  • Aids protein folding
  • Prevents protein/lipid digestion
  • Cell recognition (e.g. blood groups)
  • Cell-ECM attachment
23
Q

What is phagocytosis? Name some cells that use this process.

A

Cells engulf other cells or particles.

E.g. macrophages, dendritic cells, neutrophils, basophils and eosinophils

24
Q

What is pinocytosis? What cells use this most often?

A

Liquid droplets are ingested by cells - sampling the environment

  • Used by all cells but especially in smooth muscle
25
Q

What are the 4 pathways of transcytosis (transport across an epithelium)?

Give an example of each.

A
  1. move through aqueous channels between cells (paracellular transport) - e.g. amino acids
  2. move through lipid cell membranes (transcellular transport) - e.g. steroid hormones
  3. transported by carrier proteins - e.g. thyroxine across a follicular cell
  4. endocytosis and exocytosis - cholesterol transport
26
Q

What are the different pathways for control of an endocrine gland?

A
  1. Humoral - feedback due to concentration in the blood
  2. Neural - under neural control
  3. Hormonal - most prevalent in endocrine glands (e.g. HPA axis)
27
Q

What specialised form of neural communication occurs between the hypothalamus and anterior pituitary?

A

Neurocrine communication:

  • Neurones in hypothalamus release trophic hormones into the portal vessels when excited
  • trophic hormones carried to endocrine cells of anterior pituitary

Body Logistics Revision (25 decks)

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