Endocrine System Anatomy and Physiology Vocabulary

Flashcards defining major endocrine organs, cellular structures, and hormones based on unit lecture notes.

Endocrine system

A diverse group of ductless glands that maintains homeostasis by secreting hormones into the bloodstream to regulate cellular processes over relatively long durations.

Hormones

Chemical messengers secreted by endocrine glands into the bloodstream that typically act on distant target cells to regulate their functions.

Hypothalamus

A neuroendocrine organ located in the inferior part of the diencephalon that connects the nervous and endocrine systems and acts as the chief executive officer (CEO) of the endocrine system.

Infundibulum

A stalk-like structure that attaches the pituitary gland to the inferior surface of the hypothalamus.

Anterior pituitary gland

Also known as the adenohypophysis; the portion of the pituitary gland composed of glandular epithelium that produces and secretes hormones in response to hypothalamic signals.

Posterior pituitary gland

Also known as the neurohypophysis; the portion of the pituitary gland composed of nervous tissue that stores and releases oxytocin and antidiuretic hormone (ADH) produced by hypothalamic neurons.

Hypothalamic-hypophyseal portal system

A specialized network of blood vessels that transports releasing and inhibiting hormones directly from capillaries in the hypothalamus through portal veins to a second capillary bed in the anterior pituitary.

Oxytocin

A hormone synthesized in the hypothalamus and stored in the posterior pituitary that triggers uterine contractions and milk ejection from the mammary gland.

Antidiuretic hormone (ADH)

A hormone produced by hypothalamic neurons and stored in the posterior pituitary that causes water retention by the kidneys.

Tropic hormones

Hormones produced primarily by the anterior pituitary that influence the growth and secretory functions of other endocrine glands.

Thyroid-stimulating hormone (TSH)

An anterior pituitary tropic hormone that stimulates growth of and secretion from the thyroid gland.

Adrenocorticotropic hormone (ACTH)

An anterior pituitary tropic hormone that stimulates secretion from the adrenal cortex.

Growth hormone (GH)

An anterior pituitary hormone possessing tropic and nontropic effects that increases the rate of cell division and protein synthesis in tissues across the body.

Pineal gland

A tiny neuroendocrine organ located in the posterior and superior diencephalon that secretes melatonin to regulate sleep-wake cycles.

Melatonin

A hormone secreted by the pineal gland in response to decreased light levels that acts on the reticular formation of the brainstem to induce sleep.

Thyroid gland

An endocrine gland located in the anterior and inferior neck consisting of right and left lobes connected by an isthmus that secretes thyroid hormones and calcitonin.

Colloid

A gelatinous, iodine-rich substance found inside thyroid follicles where thyroid hormone precursors interact with iodine.

Thyroxine ($T_4$)

A thyroid hormone containing four iodine atoms produced by thyroid follicle cells that increases metabolic rate and regulates protein synthesis and cardiovascular function.

Triiodothyronine ($T_3$)

The most active thyroid hormone containing three iodine atoms that acts on almost all body cells to increase metabolic rate and protein synthesis.

Parafollicular cells

Cells located between the follicles of the thyroid gland that secrete calcitonin.

Calcitonin

A hormone produced by parafollicular cells in response to high blood calcium levels that stimulates osteoblast activity and bone deposition.

Parathyroid glands

Small glands located on the posterior surface of the thyroid gland that secrete parathyroid hormone (PTH) to regulate blood calcium levels.

Parathyroid hormone (PTH)

A hormone secreted in response to low blood calcium levels that triggers osteoclast activity, bone resorption, intestinal calcium absorption, and renal calcium reabsorption.

Antagonists

Hormones that produce opposite physiological effects on the body, such as calcitonin and parathyroid hormone.

Thymus

An endocrine organ located in the superior mediastinum that secretes hormones stimulating T lymphocyte development during infancy and childhood before gradually replacing with fat in adulthood.

Adrenal cortex

The outer glandular region of the adrenal gland that secretes steroid hormones such as aldosterone, cortisol, and androgens.

Aldosterone

A steroid hormone secreted by the outermost zone of the adrenal cortex that maintains fluid, electrolyte, and acid-base homeostasis.

Cortisol

A steroid hormone secreted by the middle and innermost zones of the adrenal cortex that helps regulate the body's stress response, blood glucose levels, fluid homeostasis, and inflammation.

Adrenal medulla

The inner deep region of the adrenal gland composed of modified postsynaptic sympathetic neurons that secretes epinephrine and norepinephrine.

Pancreatic acini

Clusters of exocrine cells in the pancreas that produce digestive secretions.

Pancreatic islets

Small islands of endocrine cells scattered throughout the pancreas that secrete insulin and glucagon.

Insulin

A hormone produced by beta cells in pancreatic islets that decreases blood glucose concentration by stimulating cellular uptake of glucose.

Glucagon

A hormone produced by alpha cells in pancreatic islets that increases blood glucose concentration by stimulating glycogen breakdown and gluconeogenesis in the liver.

Testosterone

A steroid hormone produced by interstitial cells in the testes that stimulates sperm cell production and male secondary sex characteristics.

Estrogens

Steroid hormones produced by the ovaries that promote oocyte development and female secondary sex characteristics.

Progesterone

A steroid hormone produced by the ovaries that exerts effects to prepare the body for pregnancy.