Question

How does the urinary system influence the circulatory system?

Answer 1

Urinary system plays a role in excretion of waste products from the animal body to regulate composition of body fluids and tissues. Circulatory system consists of the blood vascular system and lymphatic system. The blood vascular system constitutes heart, blood vessels and blood which is circulated in the body.

Complete answer:
The urinary system and circulatory system work in collaboration. Urine formation includes three processes: Glomerular filtration (ultrafiltration), selective reabsorption and tubular secretion. In the first process i.e., ultrafiltration, kidneys filter the blood every 4-5 minutes. This takes place in glomerulus which is a tuft of capillaries. Blood enters into glomerulus through afferent arteriole and leaves through an efferent arteriole. Around 1300 ml of blood passes through glomerulus per minute. The glomerular capillaries of kidneys are narrower than the afferent renal arterioles, which increases the blood pressure in the glomerular capillaries. This results in a continuous process of ultrafiltration (filtration under pressure) through the semipermeable glomerular capillaries. Thus, many dissolved substances and water from the blood are filtered into the lumen of the Bowman's capsule.
The glomerular filtrate contains a large amount of water and other dissolved substances such as creatinine, amino-acids, urea, uric acid, sodium, potassium, glucose, vitamins, etc. The blood flows into efferent renal arterioles. Around 15-20 percent of water and solutes are removed from blood plasma passing through glomerulus. The glomerular filtration rate in a normal person is 125 ml per minute. A total of about 180 litres of glomerular filtrate is formed per day. Glomerular filtration is regulated by two mechanisms, namely, myogenic mechanism and Juxtaglomerular mechanism.

Note: Blood plasma and glomerular filtrate are similar except that the latter does not have proteins and fats. Even though 180 litres of glomerular filtrate are produced in a day, only about 1.5 litres of urine are passed per day by a person. This is because the renal tubules absorb around 99 percent of filtrate.