It occurs in pairs, just above the kidney on either side of the spinal column.
It consists of 2 parts:
- Outer Adrenal cortex
- Inner Adrenal medulla.
Present outer to the cortex is a fibrous capsule.
- It is formed from embryonal mesoderm.
- Adrenal cortex produces corticosteroids/ corticoids. They are modifications of cholesterol.
- Corticotrophin-releasing hormone of Hypothalamus stimulates anterior Pituitary to secrete Adrenocorticotrophic hormone (ACTH). ACTH then stimulates Adrenal cortex to secrete Corticosteroids
Adrenal cortex consists of 3 layers:
Outer Zona Glomerulosa
Middle Zona Fasiculata
Inner Zona Reticularis
Hormones secreted by Adrenal Cortex:
MINERALOCORTICOIDS: secreted by Zona Glomerulosa.
- Target cells: Kidney cells.
- Its main hormone is ALDOSTERONE ( salt balancing hormone).
- It regulates electrolyte-water balance. It acts on Distal Convoluted Tubules & Collecting Ducts of Kidney, activating Na+K+pump. Causes reabsorption of Na & excretion of K. Due to this water enters by osmosis, increasing the blood volume.
It helps in maintenance of electrolyte, body fluid volume, the osmotic pressure of blood & blood pressure.
Hyposecretion causes loss of Na, Cl & water by urine and increases K in blood, thus reducing blood pressure (Hypotension)
Hypersecretion causes high blood pressure (Hypertension), nervous & muscular weakness.
GLUCOCORTICOIDS: secreted by Zona Fasciculata.
- Target cells: Liver cells.
- Its main hormone is CORTISOL.
- It causes the liver to synthesize carbohydrate from non-carbohydrate precursors like amino acids & glycerol (Gluconeogenesis). Increasing glucose level in blood – so it’s a Hyperglycemic hormone.
- Causes Proteolysis – breakdown of proteins & stimulates an increase of amino acids in the blood.
- Causes Lipolysis – breakdown of fats in adipose tissue. Releases fatty acid in the blood.
- Has anti-insulin effect.
- Anti-inflammatory: it helps in reducing pain by preventing the phagocytic action of WBC. Hence used for persons suffering from Oedema, Arthritis, Rheumatism.
- Immuno-suppressive: checks immune reactions by antibodies. It suppresses synthesis of antibodies. Hence used in the treatment of allergies and also in organ transplant.
- Maintains cardiovascular system as well as kidney function.
- Stimulates RBC production.
- Stress hormone: as it has the capability to cope stress.
GONADOCORTICOIDS/ SEX HORMONES: secreted by Zona Reticularis.
- Target cells: Gonads.
- Similar to sex hormones of gonads.
- Produced in very small amounts.
- Male hormone is ANDROGEN & female hormone is OESTROGEN.
- They cause the development of secondary sexual characters.
Disorders of adrenal cortex:
Occurs due to deficiency of Aldosterone & Cortisol.
It causes low BP, low blood sugar, low Na, high K, nausea, vomiting, & diarrhea.
Occurs due to excess of Cortisol.
It causes high blood sugar, high BP, the appearance of sugar in urine, rise in Na & fall in K in plasma.