Adrenal Glands Anatomy
There are two adrenal glands which are situated on the upper pole of each kidney. They are about 4cm long and 3cm thick. The blood supply to these glands is done by abdominal aorta and renal arteries, while the venous return is through suprarenal veins.
The glands are composed of two parts, the outer part is the cortex and the inner one is known as medulla, both of the parts have different structure and functions. We will discuss both the parts in detail.
This part of the gland is essential for life, the adrenal cortex produces 3 different groups of steroid hormones from cholesterol, all these hormones are collectively known as adreno-corticoids , which are as follows-
• Glucocorticoids:- there are 3 glucocorticoid- cortisol corticosterone and cortisone. Commonly these are collectively known as steroids. These are essential for life as they regulate metabolism and also response to stress. Glucocorticoids are stimulated by ACTH of anterior pituitary and by stress, and secretion of glucocorticoids increases in response to infection, stress and surgery.
Glucocorticoids have numerous metabolic effects like-
1. Hyper-glycaemia, that is high blood glucose level due to the breakdown of glucogen
2. Lypolysis , that is breakdown of triglycerides into fatty acids and glycerol which raises the circulatory level of fatty acids
3. Stimulate breakdown of protein
4. Promote absorption of Na and water from renal tubules.
Glucocorticoids also have some pathological and pharmacological effects like
1. Anti-inflammatory action
2. Suppression of immune system
3. Delayed wound healing.
• Mineral-corticoids:- the main mineral-corticoid is aldosterone. aldosterone is involved in maintain the water electrolyte balance, it stimulates the reabsorption of sodium through a negative feedback system and also promotes excretion of potassium in the urine. Thus aldosterone is required in the regulation of blood volume and blood pressure
Secretion of aldosterone is regulated by blood potassium level. When the blood potassium level rises, more aldosterone is secreted.
Angiotensin also stimulates the release of aldosterone, When the blood flow is reduced or sodium level falls, the kidney cells secrete an enzyme known as rennin. Rennin converts the angiotensin to angiotensin-I. Then the angiotensin converting enzyme(ace) converts angiotensin1 to angiotensin 2, which in turn forms aldosterone. Angiotensin-II also causes vasoconstriction and BP rises
• Sex hormones:-sex hormones secreted by adrenal cortex are mainly the male sex hormone known as androgens.
The medulla parts of adrenal glands is completely surrounded by the cortex. It develops from nervous tissue and is the part of sympathetic nervous system. When sympathetic nerve supply is higher, the adrenal medulla is stimulated and it releases hormone adrenaline(epinephrine) and non adrenalin(non epinephrine).
Adrenalin and non adrenalin
Non adrenalin is a postganglionic neurotransmitter of sympathetic division of ANS. Adrenalin and some of non adrenalin are released in response to the sympathetic nervous system. Structurally they are similar. Together they have fight and flight responses
1. Increases heart rate
2. Increases BP
3. Increase metabolic rate
4. Dilate the pupils
Adrenaline has greater effect on heart and metabolic processes while non adrenaline shows more effect on diameter of blood vessel.
Multiple choice question(MCQs)
1. Where is the adrenal gland located?
A. upper pole of each kidney
B. near the ureters
c. urinary bladder
2. The blood supply to these glands is done through the branches of which artery?
A. renal arteries
B. femoral arteries
C. internal iliac arteries
D. external iliac arteries
3. Which of the following is the group of steroid hormones?
C. sex hormones
D. all of the above
4. Which of the following is not the metabolic effect shown by glucocorticoids?
B. breakdown of proteins
C. suppression of immune responses
5. Which of the following statement is NOT true?
A. glucocorticoids is stimulated by ACTH from posterior cavity
B. adrenal cortex is essential for life but not medulla
C. sex hormones mainly secreted by adrenal cortex are male hormones
D. adrenaline has greater effect on heart.
6. Which of the following works as vasoconstrictor to maintain blood pressure?
C. angiotensin converting enzyme
7. Which of the following is the main glucocorticoid?
D. all of the above
8. Match the following-
1. glucocorticoids a) known as adrenaline
2. sex hormones by cortex b) also known as steroids
3. mineralcorticoids c) mainly male hormones
4. epinephrine d) aldosterone
9. Which of the following does not contribute in stimulating the secretion of aldosterone?
C. angiotensin converting enzyme
D. none of the above
10. Adrenaline and non adrenalin are extensively secreted by the nerve impulses of which system?
A. parasympathetic system
B. central nervous system
C. somatic nervous system
D. sympathetic system
1. upper pole of each kidney
2. renal arteries
4. suppression of immune responses
5. glucocorticoids are mainly stimulated by ACTH of posterior pituitary
6. angiotensin 2
7. all of the above
8. A – 2 B – 3 C – 4 D – 1
9. none of the above
10. sympathetic system
REFERENCE:-. Ross and Wilson-Anatomy and physiology in health and illness; 12th edition; page no.-: 224-226.