Question

Complete the following:
a. Urinary excretion $=$ tubular reabsorption $+$ tubular secretion $–$
b. Dialysis fluid $=$ Plasma $–$

Answer 1

Solution(a):
Glomerular filtration:

Glomerular filtration is the first step of urine formation.Water and solutes in blood are filtered by glomerulus and form the glomerular filtrate.

Tubular reabsorption:

Tubular reabsorption refers to the passage of selected materials from the ultrafiltrate or glomerular filtrate into the blood.

Tubular secretion:

Tubular secretion refers to the addition of selected materials from the blood to the ultrafiltrate or glomerular filtrate.

Summary :

Urine composition:
As in tubular reabsorption and secretion, the selected materials are exchanged between the blood and filtrate.These materials are reabsorbed in blood and then returned to the filtrate to form urine.The composition of urine is different from that of glomerular filtrate due to loss and gain of selected materials.

Final answer:

Urinary excretion $=$ tubular reabsorption$+$ tubular secretion $–$ glomerular filtration.

Solution:(b)

Dialysing unit:

• The dialysing unit is composed of three components dialyser,dialysis membrane and dialysing fluid

Dialyser:

• The dialyser has two parts, the patient’s blood and dialysing fluid ,having the same composition as that of plasma except the nitrogenous wastes.
• A thin dialysis membrane separates these two parts. Blood cells and proteins remain in the blood because they are too big to pass through the membrane. Smaller nitrogenous waste products in the blood pass through the membrane and are washed away to clear the blood

Diagram:


Final answer:

Dialysis fluid $=$ Plasma $–$ Nitrogenous waste