Question

The next morning when Nurse Nan started her shift, she immediately checked on Mr. Helms. His cardiovascular and
respiratory conditions were still deteriorating, but Nurse Nan discovered something new. Mr. Helms’ urine output was
almost nonexistent. Nurse Nan informed Dr. Collins, who was gravely concerned. Dr. Collins met with Mrs. Helms
to tell her that her husband could not survive kidney failure. Mrs. Helms looked shocked. She then became very upset
and angry. “What did you do, Dr. Collins? My husband had a heart attack, but his kidneys were fine; he’s never had
a kidney problem! How could you let this happen?” Nurse Nan put her arm around Mrs. Helms’ shoulders and Dr.
Collins handed her a tissue. Dr. Collins explained, “The damage to your husband’s heart is very serious. The kidneys
rely on blood pressure to work and his heart failure is causing the kidney failure.”

What is the force that causes the filtration of the blood by capillaries in the kidneys to occur?

Answer 1

Kidney is the organ that filters blood and removes all the waste material from it. It consists of several functional units called nephrons.

Each nephron has a Bowman’s cup and renal tubule. The blood is filtered in the Bowman’s capsule and the filtrate is processed in the tubule.

Bowman’s cup houses a capillary network called glomerulus. The glomerulus is formed by an incoming afferent arteriole and an outgoing efferent arteriole. The renal artery gives rise to afferent arteriole that brings blood into the glomerulus.

The afferent arteriole is wider than the efferent arteriole. As a result more blood flows into the glomerulus and less blood leaves it. This develops a hydrostatic force in the glomerulus which filters the blood.