Pituitary Histology Flashcards
The Anterior pituitary is embryonically derived form the
oropharynx ectoderm
The Posterior Pituitary is embryonicall derived from the
neuroectoderm
The Adenohypophysis is comprised of what 3 components?
Pars tuberalis
Pars distalis
Pars intermedia
The Neurohypophysis is comprised of what 2 components?
Pars nervosa – infundibular process
(neural lobe)
Infundibulum
(neural stalk)
The pituitary blood supply is from what system?
Hypothalamohypophyseal Portal System
The pituitary blood supply comes from what 2 sets of vessels?
Superior hypophyseal arteries
and Inferior hypophyseal arteries
These arteries arise from internal carotid arteries & posterior communicating artery of circle of Willis. They
Supply pars tuberalis, median eminence & infundibulum
Superior hypophyseal arteries
These arteries arise from internal carotid arteries and
Supply pars nervosa
Inferior hypophyseal arteries
Most of ______ lobe has no direct arterial supply
anterior
describe the portal blood supply
Arteries give rise to fenestrated capillaries (primary capillary plexus) that
drain into portal veins that
drain into hypophyseal portal veins that
give rise to a second fenestrated sinusoidal capillary network (secondary capillary plexus)
Neuroendocrine secretions of hypothalamus nerves are carried through median eminence and infundibulum into the ____________
pars distalis
which (anterior or posterior) is darkly and lightly stained
Anterior = dark Posterior = light (nerves don't stain well)
which lobe makes hormones, so cells are filled with rER and ribosomes that stain dark with H&E stains?
anterior
which lobe is primarily nonmyelinated axons, nerve endings and blood vessels that stain faintly with H&E stains?
Posterior
what is the pars nervosa?
neurohypophysis (posterior pituitary)
what is the pars distalis?
adenohypophysis (anterior pituitary) 75% of anterior pituitary Parenchyma Anastomosing cords of cells Sinusoidal capillaries Colloid (cysts) Cell types: chromophobes & chromophils
Where are chromophobes & chromophils found?
Pars distalis
Chromophobes are what type of cells?
Degranulated chromophils
Faintly stained
Chromophils are what type of cells?
Acidophils (~40%) - Pink stained
Basophils (~10%) - Purple stained
Acidophil somatotropes secrete what?
Growth hormone (GH) or somatotropin (STH) Acidophilic secretory vesicles
Acidophil Mammotropes (Lactotropes) secrete what?
Prolactin (PRL)
Acidophilic secretory vesicles
Increase during pregnancy & lactation
Basophil Thyrotropes secrete what?
Thyroid stimulating hormone (TSH)
Basophilic secretory vesicles
Basophil Gonadotropes secrete what?
The largest cells in the adenohypophysis
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH) in female or Interstitial stimulating hormone (ICSH) in male
Secretory vesicles contain both FSH & ICSH
Basophil cotricotropes secrete what?
Adrenocorticotropic hormone (ACTH) Melanocyte-stimulating hormone (MSH)
Pars intermedia is what? what does it secrete?
function unclear
Basophilic cells & chromophobes
Produce melanocyte-stimulating hormone (MSH), corticotropes
Rathke’s cysts = remnants of Rathke’s pouch = colloid
Follicles lined by cuboidal epithelium and filled with colloid
What highly vascularized area has…
Superior hypophyseal arteries terminate here to form primary plexus of portal system
Basophilic cells arranged in cords alongside blood vessels
Cells contain FSH and LH
Pars tuberalis
What Consists largely of secretory nerve cells
(100,000 unmyelinated axons
Cell bodies lie in supraoptic and paraventricular nuclei of hypothalamus)
Pars nervosa
What tract Passes through infundibular stalk, Ends in pars nervosa, and Terminate in rich capillary (fenestrated) plexus
Hypothalamic-hypophyseal tract
What storage vesicles synthesized in cell bodies
Contain oxytocin or vasopressin/ADH (in different neurons), ATP, and neurophysins (specific binding proteins for oxytocin and vasopressin/ADH)
Neurosecretory vesicles of the pars nervosa
What are the “supportive” cells found throughout posterior lobe
(Specialized neuroglial cells
, Nuclei stain dark purple with an H&E stain)
Pituicytes
What are the functions of Oxytocin?
Small polypeptide (9 amino acids)
Secretion induced by suckling (milk-ejection reflex)
Causes contraction of myoepithelial cells surrounding alveoli and alveolar ducts of mammary glands
Stimulates uterine smooth muscle contraction
What are the functions of Vasopressin (anti-diuretic hormone, ADH)?
Small polypeptide
Increases permeability of distal convoluted and collecting tubules to water in the kidney
(Increases water resorption and concentrates urine)
ADH secretions stimulated by:
Increase in plasma osmolality
Decrease in blood volume
This disorder is characterized by a Lack of ADH or mutation of receptor
Victims may excrete 20 liters of urine/day (polyuria) and drink enormous quantities of water
Diabetes insipidus
