The Adrenal glands

Adrenal Cortex

Derived from mesoderm of same region that gives rise to gonadal tissue; makes up 90% of the adrenal gland at age 3, the 3 layers develop

Adrenal Medulla

Functionally part of sympathetic nervous system developing from neural crest cells give rise to postganglionic sympathetic neurons; secretes catecholamine hormones

Classification of arteries

Short capsular arterioles, intermediate cortical arteries (long branches that go through cortex to the medulla), medullary sinusoids

Adrenal Gland physiology

Produces regulatory hormones

Adrenal Cortex physiology

Mineralocorticoids, glucocorticoids, anabolic and sex hormones

Adrenal Medulla physiology

Epinephrine, norepinephrine, stress-response hormones under direct autonomic nervous system control

Zona glomerulosa hormone

Aldosterone: responsible for 95% of mineralocorticoid hormone activity

Zona glomerulosa function

Regulates sodium and potassium levels, which affect fluid and electrolyte homeostasis, including extracellular fluid volumes. Primary activation through renin-angiotensin system

Zona glomerulosa regulation

Complex process; release triggered by: dehydration, sodium deficiency, hemorrhage or elevated potassium levels. ACTH has minor role in stimulation secretion

Zona fasciculata hormone

Glucocorticoids, including cortisol or hydrocortisone (most abundant), cortisone, and corticosterone

Zona fasciculata function

Major effect on metabolism of lipids, proteins and carbohydrates; encourages fat storage. When more energy is required, assists in gluconeogenesis, which helps resist both mental and physical stress. Hormones trigger anti-inflammatory and immune-suppress responses

Zona fasciculata regulation

High stress or low blood concentration (negative feedback mechanism)

Zona reticularis hormone

Secretes male & female gonadocorticoids (estrogens & androgens)

Zona reticularis function

Promotes normal development of bones and reproductive organs; affects secondary sex characteristics but not as much as hormones from ovaries and testes

Zona reticularis regulation

Low blood concentration (negative feedback mechanism)

Hormones secreted by Adrenal Medulla

Catecholamine, Epinephrine (adrenaline) 80% and norepinephrine (noradrenaline),

Release of epinephrine and norepinephrine

Stimulated through sympathetic nervous system

Hormone secretion is controlled by

Autonomic nervous system

Testing medullary function

24 hour ruined samples used for catecholamines, metanephrines measured in urine, dopamines measured via blood or urine samples

Agenesis

Most important congenital disorders are adrenocortical hyperplasias; causes alterations and increases in steroid synthesis

Anecephalic fetus

Usually stillborn, adrenal gland consists only of provisional cortex with no fetal zone; causes either cerebral pituitary or hypothalamic

Cytomegalic type

Unknown cause, unusual adrenal cortex made up of large eosinophilic cells, gland weighs <1 g; with early diagnosis, replacement steroid therapy promotes long-term survival

Ectpopy

Consist mainly of accessory cortical material and can occur anywhere from diaphragm to pelvis including: kidney, liver, retroperitoneal tissues, ovary, testes and tissues accompanying spermatic cord