Chapter 11: The Endocrine System

Vocabulary flashcards covering core terms, concepts, and anatomical structures from Chapter 11 (The Endocrine System) of Vander's Human Physiology.

Endocrine Glands

Ductless glands that secrete hormones directly into the body fluids.

Hormones

Chemical messengers secreted into body fluids that are carried through the blood to their target cells.

Thyroid Follicles

Spherical structures within the thyroid gland surrounded by follicular cells and filled with protein-rich colloid containing thyroglobulin.

Calorigenic Action of $T_3$

The stimulation of cellular $\text{Na}^+/\text{K}^+\text{-ATPases}$ by $T_3$, leading to high rates of ATP consumption and heat production essential for body temperature homeostasis.

Autoimmune Thyroiditis

An autoimmune condition (such as Hashimoto's disease) that causes destruction of thyroid tissue, serving as the most common cause of hypothyroidism in the United States.

Graves' Disease

An autoimmune disorder characterized by high thyroid hormone secretion, serving as the most common form of hyperthyroidism (thyrotoxicosis) in the United States.

Goiter

An abnormal enlargement of the thyroid gland caused by an excess of TSH due to a thyroid hormone imbalance.

Stress

In its broadest physiological meaning, any real or perceived threat to homeostasis.

Cushing's Syndrome

A condition resulting from chronically elevated plasma cortisol concentrations, characterized by uncontrolled catabolism of tissues, osteoporosis, muscle weakness, hypertension, and fat redistribution.

Growth Hormone (GH)

Anterior pituitary hormone that serves as the major stimulus of postnatal growth, promoting cell division via IGF-1, stimulating protein synthesis, and exerting anti-insulin metabolic effects.

Insulin-Like Growth Factor 1 (IGF-1)

A peptide hormone induced by GH in precursor cells and liver that directly stimulates cell division and promotes tissue growth.

Somatostatin (SST)

A hypothalamic hypophysiotropic hormone that inhibits the secretion of growth hormone from the anterior pituitary gland.

Osteoblasts

Bone-forming cells located along the surface of calcified matrix that synthesize bone matrix and favor increased bone mass.

Osteoclasts

Large, dome-shaped bone cells that resorb calcified bone matrix, releasing $\text{Ca}^{2+}$ into the blood.

Osteocytes

Mature bone cells embedded within the surrounding calcified matrix of bone.

Parathyroid Glands

Four small endocrine glands located on the posterior surface of the thyroid gland that secrete parathyroid hormone (PTH) in response to decreased plasma $\text{Ca}^{2+}$.

Parathyroid Hormone (PTH)

Hormone secreted by the parathyroid glands that acts on bone, kidneys, and GI tract to increase plasma $\text{Ca}^{2+}$ concentration.

Calcitonin

A peptide hormone secreted by parafollicular cells in the thyroid gland that decreases plasma calcium concentration by inhibiting osteoclasts and reducing bone resorption.

$1,25\text{-(OH)}_2\text{D}$ (1,25-dihydroxyvitamin D)

The active form of vitamin D synthesized in the kidneys, which stimulates intestinal absorption of calcium and phosphate ions into the blood.

Rickets

A metabolic bone disease in children characterized by deficient mineralization of bone matrix, making bones soft and easily fractured, most commonly caused by vitamin D deficiency.

Osteomalacia

A condition in adults characterized by deficient mineralization of bone matrix, resulting in soft and fragile bones.

Osteoporosis

A condition caused by an imbalance between bone resorption and formation, resulting in decreased bone mass and strength and increased risk of fractures.

Thyrotropin-Releasing Hormone (TRH)

A hypothalamic hypophysiotropic hormone that stimulates the anterior pituitary gland to secrete thyroid-stimulating hormone (TSH).

Corticotropin-Releasing Hormone (CRH)

A hypothalamic hypophysiotropic hormone secreted in response to stress and circadian rhythms that stimulates ACTH secretion by the anterior pituitary gland.

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone that stimulates the adrenal cortex to synthesize and secrete cortisol.