Prepared by

Faiza Hameed Jan

The Adrenal glands

Adrenal glands

• Humans have two adrenal glands

Adrenal Gland

Outer portion

Cortex( 80%)

Steroid hormones

Inner portion

Medulla(20%)

Catecholamine

Anatomy of Adrenal gland

• Pyramid shaped

• Rests like a cap just above the upper end of each kidney

• No direct physical connections between adrenals and kidneys

• Weight: In normal adult 3-4g

• 5 cm (2in) at widest point

Shapes of Left and right adrenal glands

The Adrenal cortex

• Cortex is the upper portion

• Divided into 3 zones

Adrenal cortex

*Outer zone

Zona glomerulosa

*Middle zone

Zona fasciculata

*Inner zone

Zona reticularis

Zones of Cortex

Adrenal Histology

Adrenals

Zona ReticularisSecretes Sex steroids (androgens)

Zona FasciculataSecretes Glucocorticoids (Cortisol)

Glucose homeostasis and many others

Zona Glomerulosa

Secretes Mineralocorticoids(Aldosterone)

Na+, K+ and water homeostasis

Medulla: “Catecholamines”

Epinephrine, Norepinephrine, dopamine

CORTEX

Hypothalamic-pituitary-adrenal axis

• Activity of adrenal cortex is primarily controlled by ACTH

Hypothalamus---------CRH↓

Anterior Pituitary-----Corticotropes----ACTH↓

Adrenal Glands--------Catecholamines, Glucocorticoids

• This relationship between CRH,ACTH and adrenal is called Hypothalamic-pituitary-adrenal axis.

Hypothalamic-pituitary-adrenal (HPA) axis

Pathology of adrenal cortex

• Adrenal insufficiency leads to Addison’sdisease.

• Excess cortisol secretion give rise to Cushioning syndrome.

Adrenal medulla

• Inner portion

• Important component of sympathetic nervous system, together referred as sympathoadrenalsystem.

• Medulla is located centrally in each adrenal gland

• Blood flows from cortex to medulla, for this reason medulla contains high concentrations of glucocorticoids

Chromaffin tissue

• Functional unit of adrenal medulla is chromaffin cell.

• Functions as neuroendocrine cell

• Named so because the cells are readily stained by solutions containing chromium

• Pathway: Spinal cord preganglionic fibers Sympathetic chain innervate chromaffincells stimulate epinephrine secretion in blood effector organs

Hormones of Medulla

• Primary hormone secreted by medulla is Epinephrine (80%).

• Norepinephrine is normally secreted in small amounts (20%).

• Also called adrenaline or nor-adrenaline

• Collectively known as catecholamines.

• Stimulus: Sympathetic stimulation

Steps of Synthesis

• Site of synthesis : chromaffin cells of medulla • Steps:

Tyrosine↓ Tyrosine hydroxylase

DOPA↓

Dopamine↓

Norepinephrine↓PNMT

Epinephrine

DOPA=Dihydroxy phenylalninePNMT= Phenylethanolamine-N-methyl transferase

• Epinephrine is then packaged and cocentratedwithin chromaffin cells into dense membrane bound vesicle called chromaffin granules.

• Chromaffin then release epinephrine form granules into blood.

Actions of Epinephrine

• Same actions as sympathetic nervous system.

• Triggers responses appropriate to “fight or flight” situations.

• Effects on cardiovascular system

Increases cardiac output

Increases heart rate

Increases strenght of cardiac contractions

Vasodilation in skeletal muscles

Vasoconstriction in skin and visceral organs ie.GIT.

• Effects on CNS

Increases mental alertness (advantageous in life-threatening situation.

• Effects on tissues

Relaxes smooth muscles of GIT, urinary bladder, airways of lung.

• Effects on metabolism

Increases glycogenolysis in liver and muscles

Increases lipolysis in adipose tissues (conversion of TAGs into fattyacids and glycerol).

Decreses insulin secretion.

Increases glucagon secretion.

In short, epinephrine increases body capability to perform vigorous muscle activity.

The End