Overview of the Endocrine System and Hormones (lab)

Endocrine glands

Secrete hormones (chemical messengers) directly into the bloodstream: pituitary, thyroid, parathyroid, adrenal, pancreas, pineal gland.

Organs with endocrine function

Thymus, ovaries, testes.

Hormones

Powerful chemical messengers that alter the activity of organs.

Hypersecretion

Over-secretion of hormones.

Hyposecretion

Under-secretion of hormones.

Negative feedback

The presence of a hormone causes its secretion to stop.

Pituitary Gland (hypophysis)

Master gland located below the hypothalamus and connected through the infundibulum; divided into two lobes, posterior and anterior.

Anterior pituitary (adenohypophysis)

Composed of glandular tissue, regulated by the hypothalamus; secretes growth hormone, ACTH, TSH, FSH, LH, PRL, MSH.

Growth hormone (GH)

Targets bones, muscles, and other tissues, stimulates cell growth and division.

Adrenocorticotropic hormone (ACTH)

Targets the adrenal cortex, stimulates the release of adrenal cortex hormones.

Thyroid stimulating hormone (TSH)

Targets the thyroid, stimulates the release of thyroid hormone.

Follicle-stimulating hormone (FSH)

Targets the gonads, stimulates gamete production and development.

Lutenizing hormone (LH)

Targets the gonads, stimulates the secretion of sex hormones.

Prolactin (PRL)

Targets the mammary glands, stimulates milk production.

Melanocyte-stimulating hormone (MSH)

Targets melanocytes, stimulates melanin production.

Posterior lobe (neurohypophysis)

Composed of neurons that originate in the hypothalamus; secretes Antidiuretic hormone and Oxytocin.

Antidiuretic hormone (ADH)

Targets the renal tubules and stimulates water reabsorption.

Oxytocin (OXT)

Targets the uterus and mammary glands and stimulates uterine contractions during labor and delivery and release of milk.

Thyroid

Butterfly-shaped organ in the anterior neck, partially wrapping around the trachea; secretes thyroid hormone and calcitonin.

Thyroid hormone

T3 + T4; Synthesized by follicular cells, then stored in colloid until it is time to be secreted. Secreted by follicle cells and target every cell of the body. regulates oxygen utilization and the rate of metabolism of the cells.

Calcitonin

Secreted by parafollicular (Clear/C cells); targets the bone and kidneys and reduces blood calcium levels.

Parathyroid

Four pea-like glands located on the posterior surface of the thyroid gland; secretes parathyroid hormone.

Parathyroid hormone (PTH)

Secreted by chief cells. Targets the bone and kidneys, raises blood calcium levels.

Adrenal glands

One above each kidney, secretes steroid hormones(corticosteroids)and fight or flight hormones.

Adrenal cortex

Divided into 3 zones, secretes mineralocorticoids, glucocorticoids, and androgens.

Mineralocorticoids (aldosterone)

Secreted by the zona Glomerulosa. Targets the kidneys, increases renal absorption of sodium.

Glucocorticoids (cortisol)

Secreted by the zona fasiculata. Targets most cells, affects the rate of glucose metabolism.

Androgens

Secreted by the zona reticularis . Precursor to male and female sex hormones.

Adrenal medulla

Center part of the Adrenal gland, secretes epinephrine and norepinephrine.

Epinephrine (Adrenaline)

Targets most cells, increases cardiac activity, blood pressure and blood glucose.

Norepinephrine (NEP)

Targets most cells, increases cardiac activity, blood pressure and blood glucose.

Pancreas

Has both endocrine and exocrine function.

Pancreatic acini

Exocrine cells that secrete digestive enzymes and buffers into the duodenum

Pancreatic islets of langerhans

Endocrine cells that secrete insulin and glucagon.

Insulin

Secreted by beta cells. Lowers blood glucose by stimulating the uptake of glucose from the bloodstream.

Glucagon

Secreted by alpha Cells. Raises blood glucose level by stimulating the liver to break down glycogen and release glucose into the bloodstream.

Thymus

Secretes thymosin, plays a crucial role in the development of T-lymphocytes.

Pineal gland

Pinealocytes secrete melatonin which regulates circadian rhythms.

Testes

Contains Interstitial (leydig) cells which secrete testosterone.

Ovaries

Follicular cells secrete estrogen, corpus luteum secretes progesterone.

Glands that function independently of their accompanying organs

Adrenal glands, parathyroid

The lobe of the pituitary that secretes the most hormones

Anterior pituitary