3. Nuts and bolts of Endocrine System

Question 1

endocrine system composition

Answer 1

system of hormone-secreting glands

Question 2

endocrine system objectives

Answer 2

normal growth and development
adaptation to internal and external environment
contribute to process of sexual reproduction

Question 3

endocrine gland properties

Answer 3

ductless
hormone is released into interstitial space, then to blood or lymphatic stream
highly vascularised

Question 4

how are the nervous and endocrine systems different?

Answer 4

mediator molecules - NS neurotransmitters, ES hormones
speed - NS v fast, ES much slower
action - NS locally across a synapse, ES anywhere in the body

Question 5

types of hormone

Answer 5

steroid
protein/peptide
amine

Question 6

steroid hormones

Answer 6

oestradiol, testosterone
source: ovaries, testis, adrenal cortex
derived from embryonic mesodermal tissue

Question 7

protein/peptide hormones

Answer 7

ADH, oxytocin, insulin
source:
adenohypophysis - ectodermal tissue of oral cavity
thyroid, parathyroids, pancreas - endodermal origin of GI tract
scattered endocrine cells in epithelium of GI tract and lungs

Question 8

amine hormones

Answer 8

adrenaline, noradrenaline, dopamine
source: thyroid, adrenal medulla
derived from ectoderm

Question 9

endocrine sources

Answer 9

discrete glands (separate): hypophysis, thyroid, parathyroid, adrenal 
larger glands (endocrine and exocrine function): kidneys, ovaries/testis, placenta 
diffuse neuroendocrine system

Question 10

hypophysis

Answer 10

pituitary gland
compound gland suspended from hypothalamus by stalk (infundibulum)
located in sella turcica (sphenoid bone)
2 divisions - adenohypophysis and neurohypophysis
master gland - controls secretions of other glands

Question 11

adenohypophysis

Answer 11

glandular part
out pouching of ectoderm of oral cavity (Rathke’s pouch)
secretes FSH, LH, TSH etc

Question 12

neurohypophysis

Answer 12

neural part
down growth from diencephalon of brain
secretes oxytocin, ADH

Question 13

pituitary arterial supply

Answer 13

branches of internal carotid 
superior hypophyseal (median eminence, upper stalk)
inferior hypophyseal (neurohypophysis, lower stalk) 
arteries supplying medium eminence and stalk end as capillary plexus

Question 14

pituitary veins

Answer 14

capillary plexuses in median eminence and stalk ending are drained by portal veins
veins pass to anterior lobe and form a secondary plexus
provides route for neurosecretory substances released from hypothalamus to reach anterior lobe

Question 15

thyroid gland

Answer 15

bilobed land in neck
lateral lobes connected by isthmus, anterior to trachea
derived from endoderm - growth from floor of pharynx
regulated tissue metabolism, growth and development (T3, T4)

Question 16

thyroid arterial supply

Answer 16

superior thyroid (from external carotid) 
inferior thyroid (from subclavian)

Question 17

thyroid veins

Answer 17

internal jugular vein

brachiocephalic vein

Question 18

parathyroid glands

Answer 18

4 - 2 superior, 2 inferior
embedded in capsule of thyroid, posterior aspect
very small, develop mostly from 3rd/4th pharyngeal pouches
secrete parathyroid hormone
must be preserved during thyroidectomy - Ca2+ levels fall without

Question 19

what does parathyroid hormone do?

Answer 19

regulates calcium and phosphate levels within homeostasis

Question 20

parathyroids VAN

Answer 20

arteries: primarily inferior thyroid (+superior)
veins: superior, middle and inferior thyroid
nerves: middle and inferior cervical ganglions

Question 21

adrenal glands

Answer 21

suprarenal, superior pole of kidneys (T12)
retroperitoneal
coronal cut: outer capsule, cortex, medulla
pyramidal/semilunar shape

Question 22

adrenal cortex

Answer 22

derived from mesoderm
secretes corticosteroids
cells subjacent to capsule and deeper parts produce different hormones
cortex also produces adrenal androgens, eg. testosterone

Question 23

mineralocorticoids

Answer 23

secreted by adrenal cortex cells subjacent to capsule 
e.g. aldosterone
function to maintain electrolyte balance

Question 24

glucocorticoids

Answer 24

secreted by deeper parts of adrenal cortex eg. hydrocortisone
affect metabolism and electrolyte balance

Question 25

adrenal medulla

Answer 25

secretory cells = chromaffin cells
regarded as modifier sympathetic ganglion (ANS)
derived from same embryonic tissue as sympathetic ganglia
medulla cells secrete adrenaline + smaller amounts of noradrenaline, ie catecholamines
responsible for fight/flight response

Question 26

adrenal gland blood supply

Answer 26

superior suprarenal artery (from inferior phrenic)
middle suprarenal artery (from aorta)
inferior suprarenal artery (from renal)
arteries branch before entering capsule, rami supply cortex ad medulla
cortical arteries gives rise to sub capsular plexus
cortical sinusoids: distribute blood to cortical cells

Question 27

adrenal blood course

Answer 27

medullary arteries pass through cortex to supply medulla
hence, hormones produced in cortical cells influence activity of cells in medulla - cortisol mediates NA conversion fo adrenaline

Question 28

adrenal glands venous drainage

Answer 28

adrenal veins, drain into IVC or renal vein

Question 29

how is adrenal gland activity controlled?

Answer 29

hypothalamus: ACTH from hypophysis

sympathetic division of ANS, coeliac plexus, splanchnic nerves

Question 30

medullary control

Answer 30

direct from ANS = fast response
release is initiated by imputes from preglanglionic fibres
fibres end in chromatin cells
chromatin cells release catecholamines