Endocrine System: Hormone Transport and Hypothalamic-Pituitary Axis

Comprehensive vocabulary flashcards covering the mechanisms of hormone transport, protein binding, and target tissue interaction, alongside the functional anatomy and blood supply of the hypothalamic-pituitary axis.

Liver

The organ that synthesizes and secretes transport proteins into the capillary bloodstream to bind and transport hydrophobic hormones.

Endocrine gland

A ductless gland composed of secretory cells that release free hormones directly into adjacent capillaries for systemic distribution.

Target tissue

Specific cells or tissues equipped with complementary hormone receptors that bind circulating free hormones to elicit a cellular response.

Transport protein

A plasma protein produced by the liver that circulates in capillaries to bind free hormones, increasing their solubility and circulating half-life.

Capillary

A microscopic blood vessel through which free hormones, transport proteins, and bound hormone complexes circulate and exchange with surrounding tissues.

Unoccupied transport protein

A circulating plasma transport protein with an empty binding site that is available to bind a molecule of free hormone.

Bound hormone

A hormone molecule reversibly attached to a transport protein in circulation, serving as an inactive physiological reserve.

Free hormone

The unbound, biologically active fraction of circulating hormone that is capable of diffusing out of capillaries to bind target tissue receptors.

Hormone receptor

A specialized binding protein located on the surface or within the cytoplasm or nucleus of target cells that specifically recognizes and binds a hormone.

Hormone-receptor complex

The molecular unit formed by the binding of a free hormone to its specific receptor in target tissue, which triggers downstream intracellular signaling.

Hypothalamus

The brain region located superior to the pituitary gland that integrates neural signals and synthesizes regulatory neurohormones.

Pituitary gland

The endocrine gland situated inferior to the hypothalamus, comprising the anterior, intermediate, and posterior lobes to control various body functions.

Neuroendocrine cells

Specialized hypothalamic neurons that produce and release regulatory hormones into local capillaries or project axons directly into the posterior pituitary.

Hypothalamic artery

An arterial vessel that delivers oxygenated blood to the primary capillary network at the base of the hypothalamus.

Capillary network (Hypothalamic)

The primary capillary plexus in the hypothalamus that collects hypothalamic hormones secreted by neuroendocrine cell terminals.

Hypothalamic hormone

Releasing and inhibiting chemical messengers released by hypothalamic neuroendocrine cells into the portal circulation to regulate anterior pituitary endocrine cells.

Anterior lobe

The glandular lobe of the pituitary gland (adenohypophysis) that synthesizes and secretes hormones in response to hypothalamic releasing and inhibiting hormones.

Endocrine cell (Anterior lobe)

Glandular cells residing in the anterior pituitary that synthesize and secrete anterior lobe hormones into the local secondary capillary plexus.

Capillary network (Anterior lobe)

The secondary capillary network within the anterior pituitary where hypothalamic hormones act on endocrine cells and newly secreted anterior pituitary hormones enter the circulation.

Anterior lobe hormone

Hormones produced and released by anterior pituitary endocrine cells that enter the venous bloodstream to regulate peripheral endocrine glands and body tissues.

Posterior lobe

The neural lobe of the pituitary gland (neurohypophysis) that stores and releases hormones delivered via the axons of hypothalamic neuroendocrine cells.

Posterior lobe hormone

Peptide hormones synthesized in the cell bodies of hypothalamic neuroendocrine cells, transported along axon tracts, and released into the capillaries of the posterior lobe.

Intermediate lobe

A distinct anatomical region of the pituitary gland located between the anterior and posterior lobes.