Endocrine System

Pituitary

Pituitary - known as the "master gland" and is located below the hypothalamus

Hypothalamo - Hypophyseal Portal System:

Blood flow: superior hypophyseal artery (SHA) → primary portal Plexus (PPP) → portal vessels (PV) → secondary portal plexus (SPP) → hypophyseal Vein (HV)

Anterior Lobe: The Anterior Lobe is truly glandular. It is responsible for the production of LH, FSH, Prolactin, ACTH, TSH, GH

Posterior Lobe: The Posterior Lobe is nervous tissue. Axons from the pVN and SON int he hypothalamus terminate on blood vessels in the posterior pituitary. Oxytocin and ADH enter the blood in the posterior lobe. No Portal System.

Thymus

The Thymus is located .... in the bovine. In Cattle, the thymus has two lobes composed of multiple lobules. Each lobule consists on an outer cortex, and inner medulla. The function of the thymus is to create lymphocytes. Lymphocytes in the cortex do not express either Class I or Class II MHC antigens. The lymphocytes in the medulla express lymphocytes.

Testes

Testis - Male Reproduction Organ. The testes contain Leydig Cells and Sertoli Cells

Leydig Cells: LH stimulates leydig cells to produce androgens.
Sertoli Cells: act as nurse cells to sperm. FSH binds to receptors on Sertoli Cels and stimulates spermatogenesis.

Ovaries

Ovaries - Female Reproduction Organ. The Ovaries contain Theca Cells, Granulosa Cells and after ovulation the Corpus Luteum produces important hormones as well.

Theca Cells - LH stimulates theca cells to produce androgens
Granulosa Cells - FSH Stimulates granulosa cells to convert androgens to estrogens.
Corpus Luteum - post ovulation, release of progestins and relaxin

Adrenal Glands

Adrenal - The Adrenal Glands are located above the kidney, and have a cortex and a medulla portion.

Cortex:

Zona Glomerulosa - produces aldosterone
Zona Fasciculata - produces cortisol and corticosterone
Zona Reticularis - Cortisol, Corticosterone and androgens

Medulla:

Chromaffin cells produce Epinephrine and Norepinephrine

Pancreas

Pancreas - The Pancreas has a left and right lobe in ruminants and has a distinguishable short body. It has both Exocrine and Endocrine functions.

Exocrine Function: Produces digestive enzymes and Sodium Bicarbonate.

Endocrine Function: within the pancreatic islets, Beta Cells produce Insulin and Alpha Cells produce Glucagon.

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