L2 - Nuts and Bolts of Endo (anatomy)

Question 1

PITUITARY GLAND

i) what is it suspended from the hypothalamus by?
ii) where is it located?
iii) what type of tissue is the adenohypophysis? where does it originate from?
iv) what type of tissue is the neurohypophysis? where does it originate from?

Answer 1

i) pit stalk/infundibulum
ii) found in sella turcica in sphenoid bone

iii) adeno is glandular tissue
- originates from an outpouching of ectoderm of oral cavity (rathkes pouch)

iv) neuro is a neural tissue
- originates from a downgrowth from the diencephalon

Question 2

PITUITARY GLAND BLOOD SUPPLY

i) which two blood vessels supply the PG? which two structures does each supply?
ii) label picture A and B
iii) what do arteries supplying the median eminence and stalk end as? what are they drained by?
iv) describe the route taken by a hormone released from the hypothalamus to when it reaches systemic circ? (4)
v) what part of the PG are hormones released from in response to signals from the HT?

Answer 2

i) superior hypophyseal artery
- supplies median eminence and upper stalk
inferior hypophyseal artery
- supplies neurohypoph and lower part of stalk

ii) A = sup hypoph artery and B = inf hypoph artery

iii) arteries supplying the median eminence and stalk end as capillary plexuses
- then drained by the portal vein

iv) hormone > portal vein > ant pit > rest of body
v) HT signals can cause rel from both ant and post pit

Question 3

THYROID GLAND

i) is it anterior or posterior to the trachea?
ii) what connects the two lobes?
iii) where does it sit in relation to the thyroid cartilage and which tracheal ring does it end at?
iv) which germ layer is it derived from? which structure does it develop as a growth from its floor?
v) which two hormones is it under the influence of? where are these released from?
vi) name three roles

Answer 3

i) ant to the trachea
ii) isthmus connects the two lobes
iii) sits just below oblique line of thyroid cartilage and runs to 5/6th tracheal ring
iv) derived from endoderm and develops as a growth from the floor of the pharynx near the base of the tongue
v) under the influence of TRH from hypothal and TSH from ant pit
vi) roles in tissue metabolism, growth and development

Question 4

THYROID GLAND BLOOD SUPPLY

i) which two arteries supply the thyroid? what is each a branch of?
ii) where does blood drain into? (2)
iii) which nerve supplies it? what happens when this is damaged?

Answer 4

i) superior thyroid artery (branch of ext carotid)
inferior thyroid artery (branch of subclavian)

ii) drains into am extensive venous plexus then into the IJV and brachiocephalic vein

iii) supplied by vagus -> recurrent laryngeal
- damage = hoarse voice and had to swallow

Question 5

PARATHYROID GLANDS

i) how many are there? where do they sit?
ii) where do they originate from? what structure do they they migrate with?
iii) what hormone secrete and name two things this regulates
iv) what happens if they are removed?
v) what is the V(3, )A(2), N(2) supply to the parathyroids?

Answer 5

i) there are four (two sup and two inf), sit in the capsule of the thyroid
ii) originate from the 3rd/4th pharyngeal pouches and migrate caudally with the thymus
iii) secrete parathyroid hormone and this regulates caalcium and phosphate levels
iv) if removed -> blood calcium falls -> tetanic contrac -> death

v) venous drainage = sup, middle and inferior thyroid vein
arterial supply = inf thyroid (and sup)
nerve = middle and inferior cervical ganglions

Question 6

ADRENAL GLANDS

i) at what level do they sit? are the intra or retroperitoneal?
ii) in what situation are they activated in?
iii) what germ layer is the cortex derived from?
iv) what cells is the medulla derived from?

Answer 6

i) sit at T12 and are retroperitoneal
ii) activated in stress
iii) cortex is derived from mesoderm
iv) medulla is derived from neural crest cells

Question 7

ADRENAL CORTEX

i) what does it secrete?
ii) what do the cells subadjacent to the capsule secrete? give an example
iii) what does the deeper part of the cortex secrete? give an example
iv) what other hormones does the cortex produce? give an example

Answer 7

i) corticosteroids
ii) cells subadj to capsule secrete mineralocorticoids eg aldosterone
iii) deeper cortex secretes glucocorticoids eg hydrocortisone
iv) also secretes adrenal androgens such as testosterone

Question 8

ADRENAL MEDULLA

i) what are the secretory cells of the medulla? which nervous tissue do they develop from the same embryonic tissue as?
ii) what part of the nervous system is the medulla regarded as a modified version of?
iii) name two hormones that the medulla secretees
iv) what nervous response does it elicit

Answer 8

i) chromaffin cells which dev from the same embryonic tissue as the sympathetic ganglia
ii) medulla is seen as a modified sympathetic ganglion (ANS
iii) medulla secretes adrenaline and some noradrenaline (catecholamines)
iv) elicits fight or flight response

Question 9

ADRENAL GLANDS - BLOOD SUPPLY

i) which three arteries supply the adrenals and where does each branch from?
ii) what plexus do the cortical arteries give rise to? what do these turn into and what is there function?
iii) where do arteries supplying the medulla pass through first? what does this allow and given an example
iv) which veins drain the adrenals? where do these drain into?

Answer 9

i) superior suprarenal - from inferior phrenic
middle suprarenal - from aorta
inferior suprarenal - from renal

ii) cortical arteries give rise to subcapsular plexus
- then to cortical sinusoids which distribute blood to cortical cells

iii) arteries supplying the medulla pass through the cortex first
- this allows cortical cells to influence activity

iv) adrenal veins
- R drains into IVC and L drains into renal vein

Question 10

ADRENAL GLANDS - ACTIVITY

i) which brain area controls the adrenals?
ii) which division of the nervous system controls the adrenals? give two examples
iii) which hormone released from the brain stimulates corticosteroid release from the adrenals?
iv) which type of fibres do the blood vessels receive? which area is required for the fight or flight response?
v) what speed of response is elicited from the medulla? which type of symp fibres end in the chromaffin cells of the medulla?
vi) what do the chromaffin cells then release as a result of receiving impulses from these fibres?

Answer 10

i) hypothalamus
ii) sympathetic divison of the ANS eg coeliac plexus and pelvic splanchnic nerves
iii) ACTH release from the HT causes corticosteroid release from adrenals

iv) blood vessels recieve post gang fibres
- medulla is required for fight or flight response

v) the medulla elicits a fast response
- pre gang symp fibres end in the chromaffin cells

vi) chromaffin cells then release catecholamines