CBSE Class 10 Answered

Ultrafiltration is filtration under pressure, carried out in kidneys. Here, filtration is carried out through the  semipermeable capillary wall, which allows small molecules to pass but holds back larger ones.

Ultrafiltration occurs at the barrier between the blood and the filtrate in the Bowman's capsule in the kidneys. The Bowman's capsule contains the glomerulus. 

The high pressure within the glomerulus forces small molecules such as water, glucose, sodium chloride, urea etc. through the filter 's capsule and into the nephron. This type of high pressure filtration is ultrafiltration. Filtrate formed after ultrafiltration is glomerular filtrate.