Pituitary Gland Flashcards
Steroid secreting cells contain……while peptide hormone secreting cells contain…..
Mitochondria & sER (containing enzymes for hormone synthesis + lipid droplets, store the precursor
Golgi apparatus, rER, secretory granules containing the hormone
Enumerate scattered cells with endocrine function & hormones they secrete
- Enteroendocrine cells e.g. ghrelin
- Juxtaglomerular cells of the kidney, renin. Fibroblasts adjacent to renal tubules, erythropoietin
- Cardiac muscle fibers, ANF
- White adipocytes, leptin
- Epithelial reticular cells hormones for maturation & differentiation of T-lymphocytes
An example of paracrine secretion is…….
Gastrin from Pyloric G cells reaches target cells in fundic glands
Define juxtacrine secretion
In which a signaling molecule remians on secreting cell surface or adjacent ECM and affects target cells when they contact
Stroma of pituitary is composed of……while parenchyma is composed of….
Fibrous capsule & reticular CT
Epithelial endocrine cells arraned in branching and anastomosing cords separated by fenestrated capillaries
Enumerate types (theories) regarding chromophobic cells
- Partly degranulated chromophils containing sparse granules representing resting state in secretory cycle.
- Undifferentiated stem cells
- Follicular stellate joined by gap junctions may be supoorting or phagocytic cells
Subtypes of acidophils and basophils can be identified by……
TEM granular morphology or immunohistochemistry
Acidophil granules are stained by……
Eosin/Orange G
Function of somatotrophs
Secrete somatotropic/growth hormone that induces liver cells to secrete somatomedins which stimulate protein syntehsis in all tissues with particular effects on chondrocytes of epiphyseal plate leading to growth & elongation of bone.
Describe control of GH secretion
Stimulated by GHRH from hypothalamus & ghrelin
Inhibited by GHIH (somatostatin, -feedback) from hypo.
Granules of mammotrophs are stained….by…..
Red
Erythrocin
Hypertrophy & hyperplasia of mammotrophs occurs under effect of……
High estrogen during pregnancy & lactation
Mention function & control of secretion of mammotrophs
Secrete prolactin which stimulates mammary gland development during pregnancy. It initiates & maintains milk secretion during lactation.
Controlled by PRH & PIH which is dopamine (-feedback) from hypothalamus
The least cells with smallest granules are…..
Thyrotrophs
Function & control of secretion of thyrotrophs
They secrete TSH
It is stimulated by TRH from hypthalamus & inhibited by -feeback inhibition by thyroid hormones at levels of pit & hypo.
Mention the function of gonadotrophs
Secrete:
FSH: In f regulates maturation & growth of ovarian follicles. In m initiates spermatogenesis & stimulates synthesis of androgen binding protein by sertoli cells
LH: in f, induces ovulation & differentiation of cells of corpus luteum. In m called ICSH, stimulates interstitial cells to secrete testosterone.
Function of corticotrophs
Secrete propiomelanocortin which is cleaved into:
1. ACTH stimulates zona fasciculata of adrenal cortex
2. B-lipotrophin: regulates lipid metabolism
Decsribe control of corticotrophic hormone secretion
Stimulated by CRH from hypo, inhibited by -feedback by cortisol at pit & hypo.
Granules of basophils are staine by…….bec……
PAS
Glycoprotein in nature
Releasing & release inhibiting hormones reach capillaries from…….then to ant pituitary by….., thus the connection is……
Tuberoinfundibular tract
Hypothalamic-hypophyseal portal circulation
Nervous & vascular
LH & FSH are stimulated by…..
GnRH
Pars tuberalis contains mostly……
Basophil gonadotrophs
Describe microscopic structure of pars intermedia
Contains colloid containing cysts lined by cuboidal cells
It also posseses basophilic cells like corticotrophs secrete POMC cleaved into ACTH, B-lipoprotein & MSH (induce melanocytes to produce melanin)
Mention contents of neurohypophysis
- Pituicytes
- Herring bodies
- Fenestrated blood capillaries
- Reticular fibers
- Hypothalamo-hypophyseal tracts (from PV & SO nuclei)
Describe function of pars nervosa
Secretes: 1. Oxytocin stimulates uterine smooth muscle contraction during delivery & myoepithelial cells contraction for milk ejection
2. Vasopressin: acts on cells of distal convuluted tubukes & collecting tubules causing reabsaorption of water & urine concentration.
Deficiency of ADH leads to…..
Diabetes insipidus (polyuria)
Detail blood supply of pituitary
Arterial:
1. Right & left superior hypophyseal arts serve pars tuberalis, infundibulum, median eminence
2. Rt & lt inferior hypophyseal arts serve pars nervosa
2. Hypophyseal portal system:
a. Primary capillary plexus arises from superior hypophyseal art, located in median eminence where hypothalamic neurosecretory hormones enter the blood. It is drained by hypophyseal portal veins which descend through the infundibulum to adenohypophysis
b. 2ry capillary plexus found in pars distalis where neurosecretory hormones are released
Both capillary sers are fenestrated
Hypothalamus is connected to post pit by……
Hypothalamo-hypophyseal tract (axons of PV & SO nuclei)
Classify cells of pars distalis with percentage
- Chromophobes (50%)
- Chromophils (50%)
A. Acidophils (35%)
i. Somatotrophs (50%)
ii. Mammotrophs (15-20%)
B. Basophils (15%)
i. Thyrotrophs (5%)
ii. Gonadotrophs (10%)
iii. Corticotrophs (15-20%)