Endocrine Glands Flashcards
What is the function of the endocrine system?
Maintaining homeostasis
What are some features of the endocrine system?
Network of glands
No ducts - secrete hormones directly into the bloodstream
Diffuse with endocrine organs in the cranium, neck, thorax, abdomen and pelvis
Found where there are major blood supplies
What do the endocrine organs do?
Secrete hormones to regulate bodily functions, including growth and metabolism
What does the pituitary gland secrete?
ACTH - adrenocorticotrophic hormone TSH - thyroid stimulating hormone LH - lutenising hormone FSH - follicle-stimulating hormone PRL - prolactin GH - growth hormone MSH - melanocyte stimulating hormone ADH - antidiuretic hormone oxytocin
What are some features of the pituitary gland?
Infundibulum
Hypothalamus
Anterior lobe (glandular tissue) (adenohypophysis)
Posterior lobe (neural tissue) (neurohypophysis)
What are ADH and oxytocin released by? Where do they then go?
ADH - supraoptic nuclei
Oxytocin - paraventricular nuclei
Both from posterior lobe
Axons transport oxytocin and ADH from nuclei -> hormones secreted directly into the capillary bed -> ADH acts on kidneys and oxytocin acts on reproductive system
What is secreted by the adrenal cortex?
Aldosterone
Cortisol
Androgens
What is secreted by the adrenal medulla?
Adrenaline
Noradrenaline
What is the adrenal medulla?
A specialised sympathetic ganglion with preganglionic sympathetic fibres synapsing and stimulating adrenaline release
What are the zones of the adrenal cortex and what do they secrete?
Zona reticularis -> androgens (testosterone precursor)
Zona fasciculata -> glucocorticoids (cortisol)
Zona glomerulosa -> mineralocorticoids (aldosterone)
Where are the adrenal glands located?
- between the superomedial aspects of the kidneys and crura of the diaphragm
- in perineal fat
- not always in direct contact with the kidneys
- develop in the abdomen not in the pelvis like the kidneys so separate
What is the shape of the adrenal glands?
Right - pyramidal shape, contacts liver and IVC
Left - crescent shape, contacts spleen, stomach and pancreas
What is the arterial blood supply to the adrenal glands?
- superior suprarenal arteries (from inferior phrenic)
- middle suprarenal artery (from abdominal aorta)
- inferior suprarenal (from renal artery)
What is the venous drainage of the adrenal glands?
Large suprarenal vein
(right side from IVC)
(left side from left renal vein)
At what level does the thymus gland lie?
C5-T1
What are some features of the thymus gland?
Composed of left and right lobe connected by a thin isthmus
Highly vascular
Sits on top of the cricoid cartilage, is actually lower than the thyroid cartilage
Shaped like a bow tie
Has a pyramidal accessory lobe in some cases where glandular tissue sticks up from it
What is the role of the pancreas?
Exocrine - secretion of powerful digestive enzymes into small intestine
Endocrine - releases insulin and glucagon into the bloodstream to determine how the body uses food for energy
What is the arterial blood supply to the pancreas?
coeliac trunk -> splenic artery (travels transversely across the posterior border of the pancreas)
coeliac -> common hepatic artery -> gastroduodenal -> superior pancreatoduodenal
SMA behind the neck of the pancreas -> inferior pancreatoduodenal supplying the head of the pancreas
What does a gall stone do?
Blocks the bile duct stopping flow of bile
- depends on its location to see where bile flow is stopped
What are some examples of cushing-like symptoms?
Fat deposits around the face
Thinning Skin
Weight gain
Reddish purple stretch marks
What may pituitary gland adenoma present as?
Bitemporal hemianopia
Pituitary gland squashed on the above optic chiasm
Where is the pituitary gland located?
In the sphenoid bone skull
In the sella turcica specifically
Hangs down from the hypothalamus (continuous with it)
What is the blood supply to the pituitary gland?
ICA comes into the skull -> superior hypophyseal artery goes to the pituitary gland and divides into the hypothalamus -> primary plexus where hormones from hypothalamus drain into -> hypophyseal portal vein down to secondary plexus -> efferent hypophyseal veins -> cavernous sinus
All to anterior love, posterior lobe is just a neural connection so no blood supply
How is T3 and T4 released from the pituitary gland?
Low levels of T3 and T4 stimulates thyrotropin releasing hormone which travels through the portal veins acting on the anterior pituitary gland to stimulate TSH release which travels into the cavernous sinus to act on the thyroid gland releasing T3 and T4
What does the anterior pituitary gland secrete?
ACTH TSH GH LH and FSH Prolactin
What does the posterior pituitary gland secrete?
Oxytocin
Vasopressin
What does the cavernous sinus contain? Where is it?
Either side of the pituitary gland/sella turcica
Only vein in the body which has an artery running through it -> ICA
Also has cranial nerves running through it -> oculomotor, trochlear, ophthalmic, maxillary, abducens more medial
Also has sphenoid air sinus
What would be the hormonal affect of an anterior pituitary adenoma?
Anterior pituitary hormones affected, more cells so excessive hormone production:
- LH and FSH: rare, irregular menstrual periods/decreased sex interest
- Prolactin: irregular menstrual periods, abnormal milk production
- GH: gigantism in children, acromegaly in adults
- TSH: hyperthyroidism, weight loss, rapid heart rate, tremors
- ACTH: excessive cortisol = Cushing’s
What is the difference between the adrenal cortex and medulla?
Cortex is the more glandular part on the outside secreting aldosterone, cortisol and androgens
Medulla is neural part with preganglionic fibres running out of the spinal cord going to the sympathetic chain into the abdomen where they synapse in the medulla secreting adrenaline and noradrenaline into the blood
What are anterior to the thyroid gland?
Infrahyoid muscles
inferior to the hyoid bone
sternohyoid, thyrohyoid, omohyoid, sternothyroid
What is the blood supply to the thyroid?
From arch of aorta -> brachiocephalic trunk -> subclavian artery -> thyrocervical trunk -> inferior thyroid artery
Arch of aorta -> brachiocephalic trunk -> common carotid artery -> at bifurcation of internal and external carotid artery you get the superior thyroid artery
Also in 10% of cases there is a thyroid ima artery which is midline coming from the brachiocephalic trunk
What is the venous drainage of the thyroid gland?
Superior and middle thyroid veins -> IJV -> subclavian -> brachiocephalic -> SVC
Inferior thyroid vein -> brachiocephalic -> SVC
What are the posterior relations of the thyroid gland?
Recurrent laryngeal nerve - go behind the thyroid gland back up to reach the larynx
Parathyroid - 4 of them, 2 on each side, secreting PT hormone to regulate calcium in blood
What structures do you need to be careful of when operating on the thyroid gland?
- recurrent laryngeal = dysphonia
- parathyroid gland = tetany (calcium deficiency so muscular spasms)
- thyroid ima artery = post operative haemorrhage, compressed trachea
Where is the pancreas located?
In the curve of the duodenum
What is the formation of the biliary tree?
Bile is produced in the liver -> left and right hepatic ducts -> common hepatic duct -> cystic duct to gall bladder where it is stored or common bile duct -> meets with major pancreatic duct to enter the duodenum at the sphincter of oddi/hepatopancreatic ampulla at the major duodenal papilla
Where can gall stones be and where can they be harmful?
- in gall bladder = not really a problem as bile can still be stored and move
- in cystic duct = stops bile leaving gall bladder so gall bladder contracts to squeeze bile out -> biliary colic (pain)
- in common bile duct = stops bile from liver and gall bladder -> bile backs up into the liver, bilirubin not broken down = jaundice and biliary colic
- in sphincter of oddi = blocks bile from liver, gall bladder and stops pancreatic enzyme release into the duodenum -> backs up and damages pancreas -> jaundice, biliary colic and pancreatitis
