Endocrine Hormones & Glands
adrenal capsule
connective tissue surrounding gland
hypothalamus
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ovary
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pancreas
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pineal gland
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testis
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thyroid gland
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adrenal glands
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ovaries
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adrenal glands
Location: Abdomen (upper quadrants) Adjacent to superior pole of kidney Description: Paired, pyramidal-shaped, endocrine gland Two parts: cortex (outer) and medulla (inner) • Cortex: secretes hormones (corticosteroids and androgen) • Medulla: chromaffin cells secrete catecholamines (epinephrine and norepinephrine) Epinephrine and norepinephrine also known as adrenaline and noradrenaline
pancreas
Location: Abdomen, posterior to stomach. In upper abdominal quadrants; in epigastric region and left hypochondriac region (tail) Description: Accessory digestive organ/elongated nodular gland. Divided into head, neck, body, and tail Head adjacent to duodenum • Endocrine function = regulation of glucose metabolism: islet cells release hormones (insulin, glucagon, and somatostatin) into blood • Exocrine function = digestion: acinar cells produce digestive enzymes (juice) and (gland) duct cells produce bicarbonate ions; these are released into duodenum via (gland) ducts Reduction in insulin production or release by islet cells can result in diabetes mellitus
thymus gland
Location: Anterior and superior mediastinum gland can extend into inferior neck Description: Large, bilobed gland in children Atrophies during adolescence. Remnant in adults consists primarily of fibrous and adipose tissue • Secretes thymopoietin and thymosins that stimulate and promote differentiation, growth and maturation of T-lymphocytes • Site for maturation and differentiation of T-lymphocytes (primarily in young individuals)
adrenal medulla
Location: Central part of suprarenal (adrenal) gland Description: reddish-brown, core of gland. Composed primarily of chromaffin cells • Produces epinephrine (adrenaline) and norepinephrine (noradrenaline) that work with sympathetic nervous system in "fight-or-flight" responses
pineal gland
Location: Diencephalon (epithalamus) Description: Pea-sized endocrine gland, attached to roof of third ventricle • Secretes melatonin (involved in sleep/wake cycles) • Modified activity in endocrine organs (pituitary, pancreas, parathyroid, suprarenal, and gonads)
pituitary gland
Location: Midline of middle cranial fossa, rests in hypophysial fossa of sphenoid bone Description: Small, oval bilobed endocrine gland Two functional lobes: anterior (adenohypophysis) and posterior (neurohypophysis) Connected by infundibulum to hypothalamus • Anterior gland produces the following hormones: thyroid-stimulating (TSH), prolactin (PRL), adrenocorticotropic (ACTH), growth (GH), luteinizing (LH), melanocyte-stimulating (MSH), and follicle-stimulating (FSH) • Posterior gland stores and releases: antidiuretic hormone (ADH) and oxytocin (OT) Also known as: Hypophysial gland or hypophysis Comment: Posterior does not produce any hormones; ADH and OT produced in hypothalamus
thyroid gland
Location: Neck (anterior inferior) Description: Bilobed endocrine gland, normally composed of left and right lateral lobes connected across midline by isthmus of gland. An additional, superiorly-directed, conical pyramidal lobe present 50% of the time • Follicular cells: synthesize and secrete gland hormones T3 (triiodothyronine) and T4 (thyroxine) • Parafollicular cells: synthesize and secrete calcitonin Comment: Lobes lie lateral to trachea and larynx Enlarged gland known as a goiter, typically due to insufficient dietary iodine
ovary
Location: Pelvis (lateral wall). Near distal end of uterine tube. Extends into lower abdominal quadrants Description: Paired, female gonad. Almond shape and size. Contains oocytes (egg). Suspended by mesovarium of broad ligament (a peritoneal fold). Suspensory ligament contains vessels and nerves • Maturation (oogenesis) and release (ovulation) of oocytes • Produces the female sex hormones progesterone, estrogen, and inhibin Size decreases after menopause
testis
Location: Scrotum Description: Paired, oval, male gonad w/ dense outer capsule (tunica albuginea testis) Interior divided into 200-300 lobules Each lobule contains up to three seminiferous tubules • Produces sperm cells • Produces androgens (male sex hormones) such as testosterone • begins development near the kidney, and later descends along the posterior abdominal wall to the scrotum Development of sperm cells is temperature dependent (scrotal temperature ~3° lower than body cavity) Temperature of testis regulated by: (1) distance from body cavity, and (2) heat exchange between testicular artery and pampiniform venous plexus Testosterone regulates hair pattern, sperm production, skeletomuscular growth, and libido
hypothalamus
Location: Ventral diencephalon Description: Collection of nuclei located inferior to thalamus, includes infundibulum and mammillary bodies • Considered master control center for endocrine system • Secretes releasing and inhibiting hormones that control anterior pituitary gland • Produces hormones that are transported to and stored in posterior pituitary gland • Controls autonomic nervous system • Regulates body temperature, food, and water intake • Regulates emotional behavior • Maintains sleep/wake cycle