Anatomy and Cell Biology 3309 Lecture Notes - Lecture 15: Pars Intermedia, Pars Tuberalis, Paraventricular Nucleus Of Hypothalamus
15 May 2018
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Lecture 15 – Pituitary Gland
- Integrates the nervous system (what we receive as input) with reactions that are based on
hormonal secretions
- Majority of glands (pineal, thyroid, parathyroid, adrenal, ovaries, testes) are regulated by
the pituitary gland (master control gland)
- There is a protection of bone surrounding the pituitary gland (depression is called the sella
turcica)
- This indicates the importance of the gland because it is protected
Embryonic development
- There are two regions that come together to form the pituitary gland
- It starts with Floor of Diencephalon (brain): neural epithelium (nervous tissue)
- It forms an outgrowth towards the roof of the mouth (epithelial cells)
- Nervous tissue and epithelial cells from the roof of the mouth come together
- They interact structurally and functionally with one another
- Nervous tissue forms a stalk like structure vs. epithelium forms a loop
- The loop closes on itself and forms Rathke’s Pouch
- In the adult, there is evidence of the pouch
- As the gland develops, can distinguish several regions that give the gland its name
- Two lobes develop:
o Posterior (pars nervosa – nervous part of the pituitary gland)
o Anterior (pars distalis – located distal away from the pars nervosa)
- Tissue of anterior lobe that lies adjacent to pars nervosa is the pars intermedia (part of
Rathke’s pouch)
- Pars intermedia has no special function that is different from the pars distalis (it is a
structure that can be recognized in histological sections)
- Pars tuberalis: epithelial part of the pituitary gland (anterior) wraps around the stalk-like
structure that comes from the diencephalon
o Forms a tube-like wrapping around
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*** Pituitary and hypothalamus
- Since the pituitary gland is made of nervous tissue, it lies directly under the hypothalamus
- Hypothalamus and pituitary gland communicate because part of the pituitary gland is
nervous tissue
- In the hypothalamus, there are three regions (nuclei) where there are cell bodies of neurons
o Concentration of cell bodies develop the capacity to produce hormones
o Rather than signaling electrically, they produce signaling molecules
(neurotransmitters) that are not designed to stimulate other nerves but are
designed to be released into the blood stream
- Paraventricular nucleus is adjacent to the ventricle which is adjacent to the hypothalamus
- Supraoptic nucleus are nerve cells that sit over the region where the optic nerve crosses
(optic chiasma)
- Paraventricular and supraoptic nuclei send axons into the pars nervosa
- Pars nervosa receives axons from the paraventricular nucleus and the supraoptic nucleus
- Another name for the pituitary gland is the hypophysis
- Pars nervosa (posterior lobe) is also called the neurohypohysis (made of neural tissues,
axons and glial cells coming from the hypothalamus)
- Axons pass through stalk called the infundibulum and it is divided into two components
o Infundibular process
o Median eminence: adjacent to the brain
▪ Location where axons or nerve cell processes end
▪ Nerve cell processes come from the hypothalamo-hypophysiotropic nuclei
▪ Nuclei are located in the hypothalamus and feed the anterior lobe of the
hypophysis
- Anterior lobe of the hypophypsis is epithelial tissue and is called the adenohyophysis
o Adeno means epithelial
- Pars tubularis is an extension of the adenohypohysis that wraps around the infundibulum
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Blood supply
- Blood comes into the pituitary gland from two locations
- Inferior hypophyseal artery comes from below and it feeds into a capillary network within
the pars nervosa
o Inferior artery supplies the pars nervosa with blood through a capillary plexus
- Superior hypophyseal artery supplies the pars distalis with blood
o Does not directly go into the pars distalis
o It forms a capillary network in the median eminence of the infundibulum (primary
capillary plexus)
o Blood flows through veins and venules into the pars distalis where it forms a
secondary capillary network
o There is a portal system: pars distalis is supplied by a secondary capillary network
called the hypothalamohypophysial portal system
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Document Summary
Integrates the nervous system (what we receive as input) with reactions that are based on hormonal secretions. Majority of glands (pineal, thyroid, parathyroid, adrenal, ovaries, testes) are regulated by the pituitary gland (master control gland) There is a protection of bone surrounding the pituitary gland (depression is called the sella turcica) This indicates the importance of the gland because it is protected. There are two regions that come together to form the pituitary gland. It starts with floor of diencephalon (brain): neural epithelium (nervous tissue) It forms an outgrowth towards the roof of the mouth (epithelial cells) Nervous tissue and epithelial cells from the roof of the mouth come together. They interact structurally and functionally with one another. Nervous tissue forms a stalk like structure vs. epithelium forms a loop. The loop closes on itself and forms rathke"s pouch. In the adult, there is evidence of the pouch.
