Lecture 17 - Pineal, Hypothalamus, Pituitary Flashcards
Pineal gland embryology
neuroectodermal cell origin (neural tube epithelium)
Pineal gland location and structure
adjacent to the third ventricle. lobular parenchyma invaginated by CT trabeculae
Function of pineal gland
produced melatonin and serotonin; regulation of circadian rhythm; seasonal biorhythms; suppresses gonadal functions
How is serotonin converted to melatonin
HIOM - hydroxyindole-o-methyltransferase
Innervation that promotes melatonin synthesis
direct autonomic sympathetic input from superior cervical ganglion
Innervation that inhibits melatonin synthesis
visual input from retina through suprachiasmatic nucleus (hypothalamus)
Cells found in the pineal gland
pinealocytes - producing the melatonin and serotonin.
glial cells - derivatives of monocytes.
Corpora arenacea
brain sand, accumulation of material that cant be secreted.
Hypothalamus location and structure
adjacent to the third ventricle and above the pituitary gland (anterior to pineal). clusters of different neurons in an indistinct region of the brain
Nuclei in hypothalamus
(whole cell) different types of specialized neurons that are grouped together.
Anterior hypothalamus function
regulates parasympathetic autonomic NS (decreases heart rate, vasodialation), and body temp
Posterior hypothalamus function
regualtes sympathetic autonomic NS (increases heart rate, vasoconstriction)
Ventro-medial nucleus function
project to median eminence to regulate appetite, sleep and wake center; emotions, behavior
Supraoptic nucleus
regulates water/mineral metabolism (vasopressin/ADH). projects to the pars nervosa of the pituitary
Paraventricular nucleus
regualtes parturition and milk ejection (oxytocin). projects to pars nervosa of the pituitary
Bed of capillaries in the median eminence and where they come from
primary capillary plexus from the superior hypophyseal artery
Herring’s bodies
terminal dialation points in the pars nervosa where the supraoptic and paraventricular neurons deposit vasopressin and oxytocin to be stored.
What artery supplies the pars nervosa and pars distalis?
inferior hypophyseal artery
Anterior pituitary (pars distalis) hormones that terminate in the medial eminence
FLAT PiG and M- FSH, LH, ACTH (adrenocorticotropic hormone), TSH, Prolactin, GH; Melanocyte-stimulating hormone
Hypothalamic releasing hormone
intermediate secreting hormones. Will drain to the pars distalis. They are ‘releasing’ hormones.
Pituitary location
in the sella turcica - cup of bone
Neurohypophysis and its embryology
pars nervosa, infundibular stalk (stem and medial eminence). Neuronal development from the base of brain (diencephalon)
Adenohypophysis and its embryology
pars distalis, pars intermedia, and pars tuberalis. Epithelial in origin from the oral region (oral ectoderm)
Pars intermedia appearance
between the pars nervosa and pars distalis. small cyst like region.
Type of axons in the neurohypophysis
unmyelinated axons (~ 100,000)
Pituicytes in the neurohypophysis
highly branched glial cells.
What type of nuclei are found in the pars nervosa?
only pituicytes. no neuron nuclei since those will be in the hypothalamus.
Where does the fenestrated capillary bed of the pars nervosa drain to?
cavernous sinuses
Hormones in the neurohypophysis
ADH (promotes water reabsorption in the kidney collecting ducts); oxytocin (stimulates milk ejection in mammary gland & uterine smooth muscle (myometrium) contraction
binding protein in the neurohypophysis
neurophysin - carrier glycoprotein associated with the two hormones
What controls the pars distalis?
hypothalamic releasing/inhibiting hormones that are released in the medial eminence.
2 types of parenchymal cells in the pars distalis
Chromophobes (stain poorly) and Chromophils (stain intensely)
Chromophobes
lack granules. follicular cells (support cells). undifferentiated.
Chromophils
secretory cells. separated into acidophils and basophils
Acidophils
stain with eosin and orange G (stain yellow/orange). Mammotrophs (prolactin) and somatotrophs (GH)
Basophils
stain with hematoxilin and PAS (stain purple/blue). Thyrotrophs (TSH), Gonadotrophs (FSH and LH), Corticotrophs (ACTH, B-Lipotropin, B-Endorphin, MSH)
How are corticotrophs secreted?
type of chromophil - basophil. secreted as one large molecule (pro-opio-melano-cortin)
Pars tuberalis
partial collar around infundibular stalk. Basophils which secrete gonadotrophins (LH and FSH).
