VMED 5127 Dr. Al Part I: Pituitary Gland
Terms in this set (29)
What are the 6 endocrine glands?
- Ductless glands
- Release hormones into the blood to influence target cells
- Enteroendocrine cells are also present in the respiratory, digestive and reproductive systems
- Very vascularized
Origins of the pituitary gland/ hypophysis?
Ectodermal origin from:
1. Evagination of the roof of the oral cavity (adenohypophysis)
2. Downgrowth of the floor of the diencephalon (neuroohypophysis)
- Both pats of the hypophysis are surrounded by the meninges
A depression of the sphenoid bone that they pituitary gland sits in.
- Dura mater that covers and underlies the pituitary gland/ hypophysis.
The hypophysis/ pituitary gland is connected to the brain via the
- Infundibular stem and
- Neural pathways
What are the subdivisions of the hypophysis?
1. Adenohypophysis (Anterior Pituitary)
- Pars distalis/ Pars anterior
- Pars intermedia
- Pars tuberalis
2. Neurohypophysis (Posterior Pituitary)
- Median eminence
- Pars nervosa
Remnants of Roethke's Pouch
- Epithlial cells between the anterior and posterior lobes of the pituitary that surround colloid substance.
- Forms a sleeve around the stem of the infundibulum
Arterial blood supply of the hypophysis:
- Arises from the internal carotid artery as:
1. Superior hypophyseal artery - forms the primary plexus in the median eminence)
2. Inferior hypophyseal artery- forms the secondary plexus in the pars distalis
hypothalamic neurohormones are delivered by axons to the ------ of the pituitary gland.
The hypophyseal portal system of veins delivers neurohormones (that have been brought to the median eminence from the hypothalamus) from:
1. The primary capillary plexus at the median eminence to
2. The secondary capillary plexus at the pars distalis where the hormones leave to stimulate or inhibit adenohypophysis cells.
2 main hormones that the hypophysis releases:
1. TRH (Thyrotrophic Releasing Hormone) stimulates the release of TSH (Thyroid Stimulating Hormone)
2. PIF (Prolactin Inhibiting Factor)- inhibits the secretion of prolactin
Pars Nervosa (of the Posterior Pituitary) receives the axons from the hypothalamic nuclei and:
- Para centricular nucleus= releases Oxytocin
- Supraoptic nucleus= releases Vasopressin (ADH)
- Released by para ventricular nucleus
- Causes muscle contractions of pregnant uterus at parturition and the myoepithelial cells of the mammary glands for milk ejection.
- Released by supraoptic nucleus
- Conserves body water
- Raises blood pressure
Pars Distalis (in the Anterior Pituitary) has these parenchyma cells:
- Acidophils (stain red/orange)
- Basophils (stain blue)
2. Chromophobes (no staining affinity)
Pars distalis is covered by ----- and its ----- facilitates its contents diffusion.
- Pars distalis is covered by a fibrous capsule.
- It's fenestrated sinusoids facilitate its contents diffusion
Acidophils (chromophils that their granules stain red/orange in Eosin) are:
Basophils (chromophils that their granules stain blue with basic dyes) are:
Most of the pars distal is cells are ----
- Have very little cytoplasm
- Dont stain
- Could be degranulated chromophils
- Could be non-specific stem cell
- Lies in between the pars distal is and pars nervosa
Pars Tuberalis (in the Anterior Pituitary)
- Surrounds the hypophyseal stalk
- Composed of basophilic cells
- No specific hormones are known to come from here
- Some cells have granules that contain FSH and LH
The hypophyseal tract is the axons of neurosecretory cells of these 2 nuclei
1. Supraoptic nuclei (make vasopressin)
2. Paraventricular nuclei (make oxytocin)
- Extends into the Posterior Pituitary capillaries (Pars Nervosa)
- These axons form the posterior pituitary gland
- A carrier protein that binds to each hormone to carry them to the posterior pituitary so they can be released into the blood stream from the axon terminals near the blood vessels in the pars nervosa
The Pars Nervosa (of the Posterior Pituitary)..
- Is not an endocrine gland.
- The pars nervosa receives terminals of the neurosecretory hypophyseal tract and then stores the neurosecretions.
- The axons have distended ends that look like bulbs (Herring bodies) that contain membrane-bound granules of hormones.
- Distended ends of axons of the hypothalamohypophyseal tract in the pars nervosa that contain membrane bound granules of hormone.
- Looks like a bulb
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