Pineal, Hypothalamus, and Pituitary Glands

Question 1

Pineal Gland Location and structure

Answer 1

• adjacent to the third ventricle ( right at the back of the third ventricle)
• encapsulated by CT (trabeculae) creating lobules
• Contains pinealocytes
• Glial cells (phagocytic)

Corpora arenacea (brain sand)
- accumulation of material that cant be secreted

Question 2

Functions of Pineal

Answer 2

• Controls the sleep awake cycle
• secretes serotonin and melatonin
• During the day time, serotonin levels peak
• As we approach night, serotonin is converted to melatonin by HIOM
• At night, we have peak melatonin levels

Question 3

Innervation of Pineal

Answer 3

• Direct autonomic sympathetic input from superior cervical ganglion promotes melatonin synthesis
• Visual input from retina through suprachiasmatic nucleus (hypothalamus) inhibits melatonin synthesis during the day

Question 4

Pinealocytes

Answer 4

• main cell types producing serotonin and melatonin
• secretes product into fenestrated capillaries in the pineal so that it can be carried elsewhere through the body to carry out its function

Question 5

Hypothalamus

Answer 5

• Immediately above the pituitary
• adjacent to the 3rd ventricle
• Contain Nuclei (clusters of cells with similar function)
• mainly cell bodies of neurons
• Anterior hypothalamus - regulates parasympathetic autonomic NS
• Posterior Hypothalamus - regulates sympathetic autonomic NS

Question 6

Ventromedial Nuclei

Answer 6

• Project to the median eminence of the pituitary
• Median eminence is infundibular region of the stem region of pituitary that has a prominent vascular bed (fenestrated capillaries)
• capillaries are called primary capillary plexus
• hormones pass into the capillaries and down into the pars distalis of pituitary

Question 7

Supraoptic Nuclei

Answer 7

• synthesizes vasopressin/ADH
• Hormone goes to kidney and promotes fluid uptake
• Axons project through the stalk and stem and into the pars nervosa in the pituitary
• Synthesizes hormone in hypothalamus and releases them in the pituitary
• Hormones are stored in the herring bodies which can be released at a later time

Question 8

Paraventricular Nuclei

Answer 8

• Synthesizes oxytocin
• regulates birth and nurture of infant
• Project axons through the stalk and stem and into the pars nervosa in the pituitary
• Hormones are stored in herring bodies which can be released at a later time
• herring bodies are terminal vesicles

Question 9

Hypothalamo-Hypophyseal Portal System

Answer 9

• Fenestrated capillaries of median eminence originate from superior hypophyseal artery
• Inferior hypophyseal artery branches and supplies vasculature for pars nervosa

Question 10

Hypothalamic Releasing Hormones

Answer 10

• GRH
• PRH
• TRH
• GnRH
• CRH
• MRF (melanocyte stimulating hormone releasing factor)

Question 11

Neurohypophysis

Answer 11

• Neuronal component of pituitary
• Consists of infundibular stalk which is filled with axonal projections from the hypothalamus
• Pars nervosa - containing the herring’s bodies filled with oxytocin and vasopressin
• embryologically arises from neronal tissue growing down from base of the brain
• contains unmyelinated axons

Question 12

Adenohypophysis

Answer 12

• Epithelial component of pituitary
• Pars Distalis - major component
• Pars intermedia - small region between distalis and nervosa
• Pars Tuberalis - sleeve or collar around part of the infundibular stalk
• embryologicaly grows from oral epithelial tissue

Question 13

Pituicytes

Answer 13

• highly branched glial cells

- found throughout the neurohypophysis

Question 14

ADH

Answer 14

• vasopressin
• secrted by cell bodies in the supraoptic nucleus
• promotes water reabsorption in kidney collecting ducts

Question 15

Oxytocin

Answer 15

• secreted by paraventricular nucleus

- Stimulates milk ejection in mammary gland and uterine smooth muscle contractions

Question 16

Neurophysin

Answer 16

• carrier glycoprotein associated with oxytocin and vasopressin

Question 17

Pars Distalis

Answer 17

• 3/4 of pituitary gland
• controlled by releasing/inhibiting hormones released at median eminence
• drained down to the highly fenestrated capillaries in the pars distalis
• Contains Chromophobes and Chromophils

Question 18

Chromophobes

Answer 18

• lack granules
• either follicular (support) or undifferentiated cels
• stain poorly

Question 19

Chromophils

Answer 19

• Secretory cells
• Stain well

Acidophils
- stain yellow/orange
- simple proteins
Basophils
- stain purple/blue
- glycoproteins

Question 20

Acidophils

Answer 20

• secrete Mammotrophs (Prolactin)

- secrete somatotrophs (GH)

Question 21

Basophils

Answer 21

Secrete:

• Thyroid stimulating hormone
• Gonadotrophs (FSH and LH)
• Corticotrophs (ACTH, B-lipotropin, B-endorphin, MSH)
• Corticotrophs are secreted as one big product (pro-opio-melano-cortin) that is chopped up to have different functions

Question 22

Pars Tuberalis

Answer 22

• Forms a partial collar around infundibular stalk
• histologically stains as basophils
• Secretes mostly gonadotrophins (LH and FSH)
• contains primary capillary plexus

Question 23

Pars Intermedia

Answer 23

• Right between nervosa and distalis
• most of the hormone secreted here is malanoctye stimulating hormone (MSH)
• melanotrophs