Endocrinology Flashcards
What is positive feedback?
The response to change is to enhance change
In what three ways can a hormone negative feedback loop go wrong?
- Too much hormone secreted
- Too little hormone secreted
- Change in sensitivity of the target cells
List all the main endocrine glands
Hypothalamus Pituitary gland Parathyroid and thyroid glands adrenal glands Pancreas Ovaries and testes
Where is the hypothalamus?
Below the thalamus, just above the brainstem. It forms the ventral part of the diencephalon. bThis is the central core of the cerebrum and has connections to both right and left hemispheres.
Where is the pituitary gland?
It is a midline structure in the pituitary fossa of the sphenoid bone.
What connects the hypothalamus to the pituitary gland
Infundibulum
What it the pituitary gland anatomically and functionally divided into?
The anterior and posterior pituitary gland
What hormones are released by the posterior pituitary gland?
Oxytocin
ADH
How do hormones get from the hypothalamus to the posterior pituitary?
- Axons of hypothalamic neurones pass down the infundibulum into the posterior pituitary. These hypothalamic neurones manufacture 2 hormones (ADH and oxytocin)
- These hormones are then transported to the posterior pituitary within the axoplasm by axoplasmic transport.
What is an axoplasm?
The cytoplasm of axons
What hormones does the anterior pituitary gland release?
GH Prolactin TSH (thryroid stimulating hormone) ACTH (adrenocorticotrophic hormone) LH FSH
How do the hypothalamus and anterior pituitary gland work?
Hypothalamic neurones secrete either releasing hormones or inhibitory hormones to stimulate or prevent the release of its hormones into the bloodstream.
What do the hypothalamic neurones secreted their hormones into?
A portal system of veins “The hypophyseal portal system” This drains venous blood from the hypothalamus to the anterior pituitary capillary beds.
How does the anterior pituitary get its hormones into the blood stream?
A second set pof veins drains the venous blood to the hypophyseal veins and then eventually to the SVC. (and then around the body)
What is the definition of a portal system?
A capillary bed that lies between 2 sets of veins.
What does the thyroid gland need to manufacture its hormones?
Iodine
What are the two thyroid hormones?
Triiodothyronine (T3)
Thyroxine (T4)
What do thyroid hormones do?
Regulate the metabolism and stimulate growth. T3 is essential for life
What is an enlarged thyroid gland called? What can cause this?
Goitre
Dietary lack of iodine
What is the thyroid gland attached to?
The larynx
Where are the parathyroid glands?
On the posterior surface of the thyroid gland’s lobes
What do parathyroid glands do?
They manufacture and secrete parathyroid hormone (PTH) which controls the amount of calcium in the blood and bones?
How are the parathyroid glands controlled?
Not by the pituitary but they monitor the blood calcium levels directly and respond to this.
What is the blood supply to the thyroid gland?
The superior thyroid artery which is a branch off the external common carotid, and the inferior thyroid artery which is a branch of the subclavian artery
Where is the pancreas?
Int he retroperitoneal between the duodenum and the spleen
Where does the pancreas receive blood from?
Coeliac trunk and SMA (due to the fact it is foregut and midgut)
Where does the pancreas drain int venous blood?
Splenic vein, SMV and then into hepatic portal vein
Is the pancreas under pituitary control?
No
What are the endocrine cells of the pancreas?
Islets of langerhans
When is insulin secreted into the blood?
In response to islet cells detecting increased blood glucose.
What are the 2 parts of the adrenal glands?
The adrenal cortex and the adrenal medulla
What does the adrenal cortex secrete?
Glucocorticoids
Mineralocorticoids
Androgens
What controls the release of glucocorticoids?
Pituitary ACTH
What is secreted from the adrenal medulla?
Adrenaline and noradrenaline in response to sympathetic signals
What do glucocorticoids do?
Control metabolism
What do mineralocorticoids do?
Control blood pressure
What are the three unpaired branches of the abdominal aorta?
Coeliac trunk
SMA
IMA
What are the three paired branched of the abdominal aorta?
Adrenal arteries
Renal arteries
Gonadal arteries
What three arteries supply each adrenal gland?
- Superior suprarenal artery
- Middle suprarenal artery
(both branches of AA) - Inferior suprarenal artery
(branch of renal artery)
Where does the right suprarenal vein drain into?
IVC
Where does the left suprarenal vein drain into?
Left renal vein, which then drains into IVC
What does the scrotum secrete?
Testosterone and LH from the anterior pituitary
What does the broad ligament of the female pelvis secrete?
Oestrogen and progestrerone in response to FSH and LH front he anterior pituitary
Where does the right gonadal vein drain??
IVC
Where does the left gonadal vein drain?
Left renal vein
What do testosterone and oestrogen do?
- Control the development of secondary sexual characteristics
- Promote closure of the epiphyseal growth plates
- Stimulate sperm/ovum development
What does progesterone do?
Prepares the uterus for pregnancy
