endocrine histology Flashcards
location of pituitary
situated in the sella turcica
components of pituitary
- The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence. 1. The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence. 1. The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence.
embryonic origins of pituitary
The anterior pituitary is derived embryonically from an outgrowth of endoderm called Rathke’s pouch, while the posterior pituitary is really an extension of the brain (the hypothalamus).
What hormones are released from anterior pituitary and what are the cells that release them
growth hormone (somatrotrophs), prolactin (lactotrophs), follicle stimulating hormone and luteinizing hormon (gonadrotrophs), adrenocorticotropin hormone (corticotrophs) and thyroid stimulating hormone (thyrotrophs)
vasculature of anterior pituitary
Blood enters median eminence from superior hypophyseal arteries which carry regulatory peptides (releasing factors) secreted by hypothalamic neurons and then travels through the pars tuberalis. These vessels then go to the pars distalis where an extensive vascular network is located and anterior pituitary cells secrete their horomones into capillaries. Blood leaves pituitary via hypophyseal veins
List the releasing factors secreted by hypothalamic neurons
TSH-releasing hormone (TRH), gonadotropin releasing hormone (GnRH), corticotropin releasing hormone (CRH), growth hormone releasing hormone (GHRH) and the inhibitory factors, somatostatin and dopamine.
function of pars intermedia
Poorly developed in humans- consists of colloidal cysts. Some cells are corticotropes and produce melanocyte stimulating hormone
staining of cells in anterior pituitary
Growth hormone and prolactin are associated with acidophils (reddish). TSH, ACTH, LH and FSH are associated with basophils (bluish)
hormones of the posterior pituitary and how they are made
Antidiuretic hormone (ADH, vasopressin) and oxytocin, are released from the ends of axons that arise from cell bodies of neurons present in the hypothalamus. They are released as prohormones vasopressin-neurophysin and oxytocin-neurophysin which are cleaved during vesicular transport down the axon.
structure of posterior pituitary
cell bodies in the hypothalamus extend unmyelinated axons through the infundibular stalk into the post. Pituitary where the axons expand into bulbous structures containing neurosecretory vesicles (herrings bodies). There are nuclei in the posterior piuitary of pituicytes- supportive astrocyte-like glial cells which don’t produce hormones.
anterior vs posterior pituitary on staining
anterior pituitary will be highly vascular and have large number of clumped endocrine cells with large round nuclei. Posterior pituitary has a few nuclei (pituicytes) but mostly just the ends of axons
structure of thyroid gland
multi-lobed gland with series of follicles wich each contain a single layer of epithelial cells surrounding a central chamber called the colloid. Thyroid hormone is stored in the colloid.
What produces thyroid hormone
The epithelial cells produce the colloid and eventually the thyroid hormone group.
What cells produce calcitonin and what is its function
scattered “C” cells of the thyroid between follicles. This hormone decreases release of calcium from bones by down regulating osteoclast activity.
blood supply to and from the thyroid
Blood supply to the thyroid is via the inferior thyroid artery (from the thyrocervical trunk) and the superior thyroid artery (from the external carotid artery); drainage is from the inferior thyroid vein (to the subclavian vein) and the superior thyroid vein (to the jugular vein)
Where is thryoglobulin synthesized
The thyroid epithlium secretes thyroglobulin into interior of follicle and then digests it to generate thyroid hormone
What cofactor is required for thyroid hormone synthesis
iodide- Extensive vascularization around the follicles
enables iodide pumping from the blood and conversion to iodine by the epithelial cellsiodide- Extensive vascularization around the follicles
enables iodide pumping from the blood and conversion to iodine by the epithelial cells
Function of TSH
Stimulates synthesis of thyroglobulin and its uptake/breakdown from the colloid with consequent release of T3 and T4
steps of thyroid hormone production
epithelial cells uptake iodide > convert to iodine > secrete into central colloid > epithelial cells then make thyroglobulin and secrete it into the colloid > in colloid, thyroglobulin is iodinated >epithelial cell uptakes iodinated thyroglobulin and digests it in lysosomes to generate T3 and T4 which are secreted into blood
Structure of parathyroid gland
4-8 may be present, close to the thyroid. Contain Chief cells, oxyphil cells and adipose cells
Function of chief cells in parathyroid
Produce parathyroid hormone which increases osteoclast release of calcium from bone and increases Ca uptake in GI tract and by kidney. Overall increases calcium levels
Function of oxyphil cells
function is unknown but contain a number of mitochondria.
Structure of adrenal gland
Contains an outer cortex and an inner medulla.
function of adrenal gland
cortex produces steroids and medulla produces aa derived hormones
Blood supply to adrenal gland
Blood is delivered via superior, middle and inferior suprarenal arteries which form an outer subcapsular arterial plexus. Blood then passes via a netowrk of capillaries in medulla. Blood drains into the central medullary vein then into the suprarenal vein
structure of adrenal cortex
Contains an outer zona glomerulosa, middle zona fasciculata and inner zona reticularis. The cells are all high in lipid content due to lipid/steroid metabolism and they are arranged in vertical columns separated by capillaries that drain to the medulla. The mitochondria of the cells have tubular cristae characteristic of steroidogenic cells
which zone contains the largest amount of stored lipid
zona fasciculata
function of zona glomerulosa
Produces mineralcorticoids- aldosterone is main one. Controlled by angiotensin system
funcion of zona fasciculata
produces glucocorticoids such as cortisol. Controlled by ACTH
function of zona reticularis
produces androgens of modest potency. Controlled by ACTH
Function of adrenal medulla
Produces epinephrine and norepinephrine.
Structure of adrenal medulla
Cells are arranged as clusters around venous sinusoids that drain towards central medullary vein.
What controls release of hromones from adrenal medulla
sympathetic and parasympathetic control
function of pineal
production of seretonin, melatonin and peptides. Involved in gonadal regulation and circadian rhythms
