Endocrine System
Pineal Gland
CA
Pinealocytes are modified neutrons with large prominent spherical nuclei that secert melatonin (inhibits growth and maturation of gonads until puberty and may be involved in cyclical regulation of gonadal activity, its made in the dark)
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Interstitial cells(dark ovoid nuclei) are thought to be astroglia-like cells.
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Corpora Arenacea (CA)(brain sand)) composed of calcium phosphate and carbonate deposits are characteristic of pineal gland.
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There is a CT sheath (Pia mater) surrounding the pineal gland
Pituitary Hypophysis
The pituitary is the main hormonal control center of the body and has 2 major divisions, the Adenohypophysis and the Neurohypophysis with three minor divisions
1) Pars Distalis (Adenohypophysis)
2)Pars Intermedia (Neurohypophysis)
3) Pars Nervosa (Neurohypophysis)
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Pars Distalis
Pars Intermedia
Pars Nervosa
The Pars Distalis
BV
The Pars Distalis cells secrete directly into blood vessels. Which is why we see a heavy investment of blood vessels in the Pars Distalis. There are 3 types of cells in the Pars Distalis,
1)Chromophils
-Acidophils : produce Growth Hormone and Prolactin (small pink granules in the cell)
-Basophils : Produce ACTH, LH, TSH, FSH (have small bluish granules)
2)Chromophobes : stain extremely pale or not at all.
Chromophobes
Pars Nervosa
Pars Intermedia
The Pars Intermedia secretes melanocyte stimulating hormone, and is made of basophilic cells and fibroblasts in a CT matrix.
Pars Intermedia
The Pars Nervosa is an extension of the nervous system (hypothalamus), The neurons are found in the hypothalamus and the axons extend down and form the Pars nervosa. These cells secrete oxytocin and vasopressin (produced in the hypothalamus but secreted from PN), Herrings bodies are the dark rounded granules and are aggregations of neurosecretory substance (Oxytocin and Vasopresin) stored in nerve endings.
HB
Pituicytes
Thyroid
The follicles are comprised of simple epithelium which varies from low cuboidal to tall cuboidal depending on cell activity. The parafolicular or "C" cells are located within the follicle epithelium and in the interfolliclular spaces (cells are larger pale staining). Follicle cells produce thyroglobulins/colloid and the thyroid hormones
Parafollicular cells produce calcitonin
This bilobed organ has a fibrous CT capsule, septa, and lobules with prominent follicles filled with colloid and surrounded by blood capillaries and delicate CT.
The Colloid is T4 and T3 bound to thyroglobulin, upon need the thyroid hormone will be taken from the colloid and passed onto the blood stream
Parafollicular cells C cells that secrete calcitonin.
Thyroid
Parathyroid
Parathyroid
The parathyroid is four small glands behind the thyroid. It is of endodermal origin.
It is composed of 2 types of cells, Oxyphil Cells that are larger cells with many mitochondria and have an unknown function.
Chief cells are smaller and secrete PTH which increases the number and activity of osteoclasts (this will increase blood calcium levels).
Adrenal Gland
Zona Glomerulosa
Zona Fasiculata
Zona Reticularis
Medulla
The Adrenal Gland sits on top of the kidneys, it has a cortex with 3 zones; Zone Glomerulosa, Zone Fasciculata, Zone Reticularis, and a medulla.
The Zone Glomerulosa is clusters of columnar epithelial cells secreting mineralocorticoids which regulate fluid and ion balance at the renal tubule.
The Zone Fasiculata is characterized by long cords of lipid rich cells secreting glucocorticoids controlling carbohydrate, fat, and protein metabolism
The Medulla is formed from Chromaffin cells that are of neural crest origin, these cells produce the characteristic hormones of the adrenal gland Epinephrine and Norepinephrine. These increase alertness, heart rate, and release glucose from the liver. The Medulla is rich with blood vessels to facilitate rapid spread of the hormones it produces.
The Zone Reticularis is characterized by darkly staining cells arranged in reticulated mesh, secreting weak androgens.
Pancreas Islets of Langerhans
This is the endocrine portion of the pancreas and is found interspresed throughout the exocrine acinus. These clusters of cells surrounded by acinar tissue. The islets are permeated by a fine network of capillaries which will pick up the hormones secreted by the cells.
There are three principal cell types in the Islets
1) Alpha cells - secrete glucagon (darker cytoplasm and often near edges)
2) Beta cells - produce insulin (lighter cytoplasm, most numerous cell type)
3) Delta cells - secrete somatostatin
There are also some less known cells
C, D, E.
Blood capillary
