Question

Hydrostatic pressure of blood while flowing in glomerulus of nephron is
A. 10 mm Hg
B. 18 mm Hg
C. 32 mm Hg
D. 60 mm Hg

Answer 1

Hint: The kidneys are the chief organs of the excretory system. They are paired organs which are bean shaped and are present on either side of the spine behind the belly. The cells of the kidney are associated with the function of removal of waste products and excess water from the body in the form of urine. The kidneys are attached to the ureter which is a tube like structure that carries the excreted urine into the bladder.

Complete answer:
The kidney is associated with the excretion of excessive water and also eliminates toxic and waste products from the body. The kidneys are composed of specialized cells known as the nephrons. The nephrons are the basic unit of the kidneys. The nephron consists of two main parts which are the renal corpuscle and the renal tubule. The renal corpuscles are a tuft or group of capillaries and are called the Bowman’s capsule. The renal corpuscles are the initial filtrating site of the nephrons and they are followed by the renal tubule. The endothelial cells are present in the capsule as well as in the renal corpuscles.

The process of filtration of the blood into urine occurs in four important steps which are filtration, reabsorption, secretion and excretion. The initial process of filtration occurs in the glomerulus. It depends on the intracapillary blood pressure and is mostly passive. The other steps of the process such as reabsorption and secretion takes place in the renal tubules.

When the hydrostatic force pushes the solutes along with the water through the filtration membrane it causes the process of filtration in the glomerulus. The volume of filtrate produced by both the kidneys is known as glomerular filtration rate or GRF. The blood which is present inside the glomerulus creates a pressure that is known as glomerular hydrostatic pressure and this pressure causes the fluid to move from the glomerulus to the capsule. The fluid contained in the glomerulus capsule in turn exerts a pressure and it pushes the fluid out of the capsule back into the glomerulus. This pressure is termed as capsular hydrostatic pressure and it creates an opposition to the glomerular hydrostatic pressure. The filtrate does not allow the passage of most of the proteins and it results in movement of water out of the capsule and towards the glomerulus. This pressure is known as the colloidal osmotic pressure and it acts to draw water into the glomerulus.

The glomerular filtration takes place when the hydrostatic pressure of the blood is more than the hydrostatic pressure of the glomerulus capsule as well as the blood osmotic pressure. The sum of all osmotic pressures and hydrostatic pressures are referred to as the net filtration pressure or NFP. It is calculated as the difference between glomerular hydrostatic pressure and the sum of blood colloid osmotic pressure and the capsular hydrostatic pressure. The glomerular hydrostatic pressure is about sixty mm of Hg whereas the values of blood colloid osmotic pressure and the capsular hydrostatic pressure are maintained at thirty mm of Hg and twenty mm of Hg respectively.

Hence, The correct answer is option (D).

Note: The renal corpuscles bearing the tuft of glomerulus capillaries along with the tubules are the actual site of filtration of blood. The filtration of blood into urine depends upon maintaining proper pressure. The pressure must be maintained at an optimum level. The hydrostatic pressure of the blood plays an important role as filtration takes place when the rate of hydrostatic pressure of blood is more than that of the glomerular capsular hydrostatic pressure and the blood osmotic pressure.