glands - pituitary Flashcards
location of pituitary
Suspended by pituitary stalk/infundibulum
Sits in depression in sphenoid bone
function of the pituitary
Site of production and secretion of hormones that control a variety of processes across multiple body systems
gross structure of pituitary
Has an anterior lobe (adenohypophysis)
Has hypophyseal portal vessels that communicate between the hypothalamus and anterior lobe
Has a posterior lobe (neurohypophysis)
Essentially an extension of the hypothalamus
blood supply:
superior hypophyseal artery = loops round hypothalamus first
venous drainage
anterior and posterior hypophyseal veins
histology of the anterior pituitary
Anterior pituitary is made up of different endocrine cell types (e.g. lactotroph cells) that secrete different hormones
histology of the posterior pituitary
Posterior pituitary is made up of the axons and terminals of secretory neurons from the hypothalamus.
Glial cells surround each termina
Hormones are only stored and released in the posterior pituitary - they are synthesized in the supraoptic and paraventricular nuclei of the hypothalamus
hormones of the Adenohypophysis
- growth hormone
- TSH
- ACTH
- LH/FSH
- prolactin
hormones of the ineurohypophysis
- oxytosin
2. ADH/vasopressin
TSH - action and control
Thyroid stimulating hormone (TSH)
Acts at the thyroid to stimulate production of T3/T4
increases iodine take up by the thyroid and stimulates thyroid growth
Controlled by TRH secreted by the hypothalamus, that reaches the anterior pituitary via the portal system.
TRH is controlled by a negative feedback of T3/T4.
ACTH action and control
Adrenocorticotropic hormone (ACTH)
Stimulates the adrenal cortex to synthesise cortisol.
Also stimulates the production of sex steroids
Release is stimulated by CRH from hypothalamus
CRH is controlled by negative feedback of glucocorticoids (e.g. cortisol)
prolactin - action and regulation
Prepares body for lactation = stimulates growth of secretory alveoli in breast
Inhibits menstrual cycle
Increased secretion by oestrogen and suckling
Decreased by dopamine from hypothalamus
growth hormone
Growth hormone
Stimulates growth of long bones and soft tissues
Secretion is increased by hypoglycemia, stress and exercise detected by the hypothalamus which releases GHRH
Somatostatin will inhibit it.
Controlled by negative feedback.
LH/FSH - actin and control
Gonadotrophins (LH and FSH)
FEMALES: LH and FSH control follicle development, ovulation and synthesis of sex steroids by ovaries and corpus luteum
MALES: LH controls testosterone production of Leydig cells
FSH stimulates sertoli cells for sperm production
Control varies with different cycles (e.g. menstruation) and inhibited by various hormones (e.g. inhibin inhibits LH in males)
ADH/vasopressin - action and control
ADH/Vasopressin
Increases water reabsorption in collecting ducts of kidney
Constricts peripheral arterioles and veins
Controlled by negative feedback detected by hypothalamus:
Increases in reduced blood pressure or high osmolarity
