Study Excretion and Osmoregulation for MH-CET 2014
Study Excretion and Osmoregulation
for MH-CET 2014
1. Urinary bladder is provided with transitional epithelium and detrusor
i. Transitional epithelium helps in the expansion of the urinary bladder.
ii. The detrusor muscles are smooth muscles which help in making the wall of
urinary bladder though and thick.
iii. Since in the urinary bladder, about half to one litre of urine is stored
temporarily, it needs to be expandable and tough.
iv. Urinary bladder is provided with such transitional epithelium and detrusor
muscles as they help in this function.
2. EFP is crated in the glomerulus.
i. EFP or effective filtration pressure is a hydrostatic pressure.
ii. It is created because the blood enters the glomerulus at a faster rate than the rate
by which it leaves.
iii. This is because the diameter of afferent renal arteriole is larger than the
diameter of efferent renal arteriole.
iv. The glomerular capillaries therefore create glomerular hydrostatic pressure
called EFP in the glomerulus.
3. Distal convoluted tubule is important for homeostatic regulation of
acidity of blood.
i. During the last phase of urine formation, i.e. during tubular secretion, some
nitrogenous waste substances which have eventually entered the blood circulation
through peritubular capillaries are secreted back into the DCT.
ii. The substances routinely secreted back are creatinine, potassium and hydrogen
iii. The secretion of hydrogen ions occurs chiefly in DCT and collecting tubule.
iv. This regulates the acidity of the blood through homeostasis. Therefore, distal
convoluted tubule is said to be important for homeostatic regulation of the acidity
4. Osmoregulation and excretion go hand in hand.
i. Kidneys are the organs of excretion and osmoregulation.
ii. The water is removed by the kidney as per the requirement of the body.
iii. While doing so the solute concentration is also maintained to a constancy by
iv. Hormones like ADH which maintain osmoregulation act on renal tubules in
kidney. Similarly aldosterone, parathormone, etc. also maintain ionic balance in
kidney. Thus, osmoregulation and excretion go hand in hand.
5. Low secretion of ADH causes diabetes insipidus.
i. Diabetes insipidus is a disorder in which excessive urine is produced with
ii. Polydipsia and polyuria are due to lack of sufficient ADH secretion.
iii. ADH causes antidiuretic effect. When ADH is in more amount every drop of
water is reabsorbed through the loop of Henle. Due to this hypertonic urine is
iv. But when ADH level is low water reabsorption is suppressed. This produces
v. When ADH secretion is low then person concerned produces excessive urine
due to faulty reabsorption of water leading to diabetes insipidus.
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