Glands 5

Question 1

What is a gland?

Answer 1

An aggregate of epithelial cells that are specialised for the secretion of a substane

Question 2

How do glands regulated human physiology?

Answer 2

They receive stimuli from the CNS (brain), circulating levels of chemicals and neighbouring cells

Question 3

What are the two types of gland?

Answer 3

Endocrine (ductless, secrete to IS space so their hormones can act on distant parts of the body, eg. pituitary, thyroid, parathyroid, prolactin, all of these cells secrete) and exocrine (ducted, specific location, mostly enzymes of lubricants, eg salivary, pancreas, sweat, only cells at apex of duct secrete)

Question 4

What are the two parts of the pituitary gland, and what does each produce?

Answer 4

Anterior - hormones (ACTH, LH, FSH, TSH, growth hormone) which regulate most of the glands of the endocrine system
Posterior - vasopressin (ADH) which prevents water loss from kidneys (alcohol prevents production of ADH), and oxytocin, which signals uterus for delivery

Question 5

What does the thyroid gland do?

Answer 5

Produces thyroid hormones T3 and T4 which control metabolism, thermoreulation, and produces calcitonin which is involved in calcium homeostasis

Question 6

What does the parathyroid gland do?

Answer 6

Produces parathyroid hormone which cancels the action of calcitonin, increases calcium levels

Question 7

How are glands formed in utero? (week 4-5 of gestation)

Answer 7

Fibroblast GF (mostly FGF10) is produced by mesenchymal cells sitting under epithelium
Cells proliferate and produce extracellular protein degradation enzymes (collagenase, elastase etc.) so they can grow down through connective tissue
Exocrine - central cells die to form duct 
Endocrine - produce angiogenic factors to stimulate blood vessel growth in and around epithelial cells, link to mother cells broken through apoptosis

Question 8

How does branching occur?

Answer 8

Epithelial cells move towards signal, tubule can elongate or branch depending on which GFs are active
Elongating and branching stopped by Shh

Question 9

What types of gland ducts are there?

Answer 9

Can be tubular or alveolar
Each of those can be simple (T-intestine), simple branched (T-stomach, A-sebaceous), or compound (T-duodenal, A-mammary)
Also, compound tubuloalveolar (salivary)

Question 10

What does acinar mean?

Answer 10

Alveolar (acinus means berry)

Question 11

How can cells at ends of ducts specialise to help eject secretions?

Answer 11

By changing morphology and turning into myoepithelial cells

Question 12

What secretions does the salivary duct produce?

Answer 12

Mucous and serous

Question 13

How do breasts develop?

Answer 13

Prepuberty - terminal end buds form, stops until puberty
Puberty - estrogen and progesterone cause ductal elongation and side branching
Pregnancy - prolactin causes lactogenic differentiation

Question 14

What are the different ways a gland cell can secrete?

Answer 14

Merocrine - exocytosis (acinar, endocrine of pancreas)
Apocrine - top of cell is pinched off (usually duct) (lactating mammary, sweat in axilla, ext. genitalia)
Holocrine - entire cell dies to become product (sebaceous, tarsal in eyelid)
Cytocrine - cells released as secretion

Question 15

What are the two pathways of merocrine secretion?

Answer 15

Regulated - large vesicles of many secretory granules, need calcium ions to stimulate release, usually modified by Golgi, uses ATP
Constitutive - small vesicles, continuously released, not modified, used to repopulate plasma membrane with proteins

Question 16

How do vesicles move towards the cell surface?

Answer 16

Along microtubules (uses dynein), uses SNARE protein to help fuse with plasmalemma

Question 17

How is insulin released?

Answer 17

When glucose enters a beta cell in the pancreas and is metabolised, ATP closes the channel which usually pumps potassium out of the cell, causing the membrane to depolarise. This causes calcium channels to open to calcium flows in, causing vesicles with insulin to move to the surface and release their contents by regulated merocrine secretion

Question 18

How do you treat a patient with type 1 diabetes?

Answer 18

They don’t have enough insulin so either insulin is injected or sulphonylurea is given which binds to the ATP sensitive potassium channel, causing an increased release of insulin

Question 19

What is the difference between the neonatal period and the lactating period in terms of secretion?

Answer 19

Neonatal - only fats secreted by apocrine secretion (signet fragment), proteins released by merocrine
Lactating - both fats and proteins released by apocrine

Question 20

What colour does sebum stain in a H&E stain?

Answer 20

Pink

Question 21

What does the Golgi apparatus do to regulated secretion?

Answer 21

It modifies the proteins (using glycosal transferases to glycosylate them) and targets them to correct addresses

Question 22

What is the difference between glycosylation and glycolation?

Answer 22

Glycolation doesn’t use enzymes, the other uses glycosal transferases

Question 23

What is the role of glycosylation?

Answer 23

Aids correct protein folding, prevents digestion by proteases and lipases, cell recognition
All known disorders of glycosylation are rare and often lethal

Question 24

How does glycosylation aid cell recognition?

Answer 24

Proteins are glycosylated in two places - on asparagines (N-glycosylation) and tyrosines (O-glycosylation), so any enzyme that recognises either of these won’t digest it
Sugars on surfaces of cells are detected by selectins; cancer cells don’t produce them so go undetected

Question 25

What types of glandular control are there?

Answer 25

Hormonal (endocrine), humoral (endo, essentially feedback loops), neural (only does salivary (exo))

Question 26

How does the hypothalamus communicate with the pituitary gland?

Answer 26

Via neurocrine secretion

Neurones continue into posterior pituitary