anatomy Flashcards
location of the pituitary gland
at the base of the brain beneath the third ventricle
embryology of the anterior pituitary (adenohypophysis)
epithelial upgrowth from Rathkr’s pouch, the roof of the primitive oral cavity (aka the pharynx)
embryology of the posterior pituitary (neurohypophysis)
downgrowth of nervous tissue from the hypothalamus/neuroectoderm (diencephalon)
hormones produced by the anterior pituitary (7)
follicule stimulating hormone, luteinizing hormone, thyroid stimulating hormone, prolactin, growth hormone, adrenocorticotropic hormone, melanocyte stimulating hormone
hormones produced by the posterior pituitary
antidiuretic hormone, oxytocin
anterior pituitary staining under H&E stain
darkly stained
posterior pituitary staining under H&E stain
lightly stained
parts (pars) of the anterior pituitary and the cells they contain
pars tuberalis, pars intermedia (contains MSH-secreting melanotrophs), pars distalis (contains gonadotrophs, acidophils, basophils)
difference between chromophils and chromophobes (both found in anterior pituitary)
chromophils: contain large number of granules which appear as dense large dots
chromophobes: degranulated, do not stain under H&E stain
types of chromophils in anterior pituitary and their secretions
acidophils (stained rich pink): somatotrophs (GH), mammotrophs (PRL)
basophils (stained darkly blue): gonadotrophs (FSH, LH), corticotrophs (ACTH), thyrotrophs (TSH)
posterior pituitary cells
non-myelinated axons of specialized neurons - the cell bodies are located in the supraoptic nuclei (SON) and paraventricular optic nuclei (PVN) of the hypothalamus where ADH and oxytocin are produced and stored
what are Herring bodies? (found in posterior pituitary)
neurosecretory granules containing ADH or oxytocin, accumulating in neuronal axons where they contact a large number of capillaries. they are supported by pituicytes (specialized highly branched glial cells)
blood supply of the anterior pituitary
internal carotid artery branching into superior hypophyseal arteries branching into secondary capillary plexus
blood supply of the posterior pituitary
internal carotid artery branching into inferior hypophyseal arteries
how is the release of hormones from the pars distalis of the anterior pituitary regulated?
controlled by the hypothalamic hypophyseal portal system: release of regulatory hormones from the hypothalamus into the primary capillary plexus –> secondary capillary plexus
additional control by negative feedback
location of the thyroid gland
anterior and inferior to the larynx in the neck
shape of the thyroid gland
butterfly shaped gland with two lobes connected by an isthmus
embryology of the thyroid gland
develops from foregut endoderm near the base of the developing tongue
functional units of the thyroid gland (histology)
thyroid follicles, composed of a single layer of flattened squamous (inactive) or columnar (active) epithelial cells bounded by a basement membrane
and C / parafollicular cells found as individual scattered cells in the follicle lining or small clumps between follicles
contents of thyroid follicles
colloid material storing thyroglobulin (storage form of thyroxine T4 and tri-iodothyronine T3)
function of C / parafollicular cells
secrete calcitonin hormone which lowers blood Ca2+ level
location of parathyroid gland
4 ovoid masses lying on the posterior surface of the thyroid gland within its capsule
parathyroid histology
chief cells that secrete parathyroid hormone, oxyphil cells (large degenerated chief cells) which are stained dark pink
function of parathyroid hormone
increases blood Ca2+ levels by activating osteoclasts:
a) stimulating bone resorption (releasing Ca2+ into blood)
b) increasing absorption of Ca2+ (in small intestine via vit D absorption)
c) decreasing Ca2+ excretion in DCT of renal cortex
location and description of adrenal gland
small flattened endocrine glands which are applied to the upper pole of each kidney, consisting of the adrenal cortex and medulla
adrenal cortex components (and histology)
zona glomerulosa: secretes mineralocorticoids, mostly aldosterone
zona fasciulata: vacuolated appearance, lightly stained due to lipids, secretes glucocorticoids, mostly cortisol (and some androgens)
zona reticularis: heavily stained, secretes glucocorticoids and androgens
what hormone controls the secretions of zona fasciulata and reticularis
ACTH (adrenocorticotropic hormone)
adrenal medulla histology
clusters of cells (chromaffin cells and ganglion cells) that are large, pale staining, polyhedral, and electron-dense granules containing catecholamines
adrenal cortex embryology
develops from the mesoderm
adrenal medulla embryology
develops from the neural crest
endocrine pancreas cells and secretions
α cells (glucagon), β cells (insulin), delta cells (somatostatin), PP/F cells (pancreatic polypeptide)
endocrine pancreas (islets of Langerhans) histology
α-cells stain deep pink, β-cells stain light pink, islets of Langerhans present in cords separated by fenestrated capillaries
