Endocrine Flashcards
Tobias ch 120-121
What structures border the right adrenal gland?
lateral - right kidney
cranial - covered by caudate process (liver)
medial - CVC
caudal - renal artery/vein
dorsal - T13
ventral - phrenicoabdominal vein
Which adrenal gland is at the level of L2?
Left
Which vessel transects the adrenal glands ventrally?
phrenicoabdominal vein
Which adrenal gland lies closes to the aorta?
Left
The right adrenal gland is often contiguous with adventitia of which vessel?
CVC
Blood supply to adrenal glands
Phrenicoabdominal aa
Renal aa
Cranial abdominal aa
Aorta
True/false - the left adrenal gland empties directly into the vena cava
False. Right AG into CVC. Left AG into L renal vein
3 zones of the adrenal glands (outer to inner)
Zona Glomerulosa
Zona fasciculata
Zona reticulata
What is the primary hormone produced by the zona glomerulosa?
mineralocorticoids
What compound makes up the difference between aldosterone and cortisol?
17-alpha-hydroxylase
Which zone of the adrenal produces glucocorticoids?
Zona fasciculata
What zone of the adrenal glands produces sex steroids?
Zona reticulata
How are steroid hormones transported through blood?
Lipids - transported by binding to plasma proteins
Majority of cortisol in circulation is bound to what plasma protein?
Transcortin
Glucocorticoid negative feedback system
Glucocorticoids –>
Inhibit corticotropin-releasing hormone (hypothalamus) –>
Decreased corticotropin secretion (pituitary gland)
Functions of glucocorticoids
regulation of metabolism by stimulating hepatic gluconeogenesis
Inhibit glucose metabolism in muscle,fat
Stimulate lipolysis
Inhibit protein synthesis
Enhance protein catabolism
Increase GFR
Inhibit ADH
Stimulate gastric acid secretion
Suppress inflammation/immune response
Function of mineralocorticoids
electrolyte balance
Blood pressure homeostasis
What are the effects of angiotensin II?
Peripheral vasoconstriction
Secretion of aldosterone from AGs
Where in the body is angiotensin I converted to angiotensin II?
Pulmonary capillary endothelium
Function of aldosterone in renal tubules
promotes Na, Cl, H2O reabsorption
What cells produce catecholamines?
Chromaffin cells (adrenal medulla)
What hormones are produced from the adrenal medulla?
Catecholamines (epi, norepi, dopamine)
What regulates adrenal medulla?
sympathetic nerve stimulation
What ratio of catecholamines is secreted by the adrenal gland in cats/dogs?
Cats
-70% epi
-30% norepi
Dogs
- 60% epi
- 40% norepi
Function of epinephrine
Beta 2 receptors:
-increase BG conc (promote hepatic glycogenolysis, gluconeogenesis)
-stimulates glycogenolysis in muscle
Alpha 2 receptors:
-inhibit insulin secretion
- stim pancreas glucagon to increase BG
-promotes lipolysis
increase force of cardiac contraction
increase HR
Alpha 1 and 2 receptors control catecholamine release where in the body?
pre/post synaptic sympathetic nerve endings
Epinephrine has highest affinity for which receptors?
Beta 2
-control metabolism, increase BG conc
-vasodilation in skeletal muscle, coronary arteries, veins
what characteristics of adrenal glands raise concern for mass/neoplasia?
max width > 1.5cm
loses kidney bean shape
asymmetric to contralateral AG
Adrenal masses greater than __mm are likely to be malignant?
20mm
Which thyroid gland sits more cranially?
right
isthmus glandularis
narrow bridge of thyroid parenchyma between both thyroid glands (present in some dogs)
Which thyroid gland(s) is in contact with the carotid sheath normally?
right
(left displaced by esophagus)
What structure forms the dorsolateral boundary of the left thyroid gland?
Esophagus
What structures are in close proximity to the thyroid glands?
carotid artery
internal jugular vein
vasosympathetic trunk
tracheal duct
Esophagus (left)
recurrent laryngeal nerves
Components of the carotid sheath
carotid artery
internal jugular vein
vasosympathetic trunk
Where are the recurrent laryngeal nerves relative to the thyroid glands?
dorsomedial
the cranial thyroid artery is a branch of which artery?
common carotid
The cranial and caudal thryoid arteries arise from which major arteries?
cranial - common carotid
Caudal - brachiocephalic
In most cats, which vessel of the thyroid gland is absent?
caudal thyroid artery
venous drainage of the thyroid gland
cranial/caudal thyroid veins –> internal jugular vein
Innervation to thyroid gland
thyroid nerve (branch of cranial laryngeal, branch of vagal nerve)
Which parathyroid gland is found within the thyroid parenchyma?
Internal parathyroid gland (usually caudal)
The parathyroid glands sit on which aspect of the thyroid glands
dorsolateral
Which set of parathyroid glands are typically more cranially located? (internal vs external)
External
functional unit of the thyroid gland
thyroid follicle
What amount of T4 and T3 circulate free/unbound in circulation?
<1%
What glycoprotein is the precursor for thyroid hormone synthesis?
thyroglobulin
Which thyroid hormone has more biological activity? T3 or T4
T3
TSH is secreted by the ____
pituitary gland
TRH is stimulated by the ___
hypothalamus
thyroid hormone has a negative feedback effect to inhibit secretion from ______?
pituitary gland (secretes TSH)
Where do calcium and phosphorus homeostasis occur
bones
kidneys
intestines (indirect)
Effect of PTH on the kidneys?
decrease Ca excretion
Increase Phos excretion
increase calcitriol formation from Vit D in kidneys
The primary effect of PTH is to:
a. decrease serum conc of Phos
b. increase serum conc of Ca
b - increase serum conc of Ca
Function of calcitriol
increase absorption of Ca and Phos from intestines
Where is calcitonin produced?
thyroid gland parafollicular cells (C-cells)
function of calcitonin
decrease bone resorption (decrease Ca conc)
