Nephron

Kidneys usually function in osmoregulation and excretion. They help regulate our blood and maintain our body’s calcium levels. After the kidney finishes processing the blood from the renal artery, the blood is returned to the body by the renal vein. During this, the wastes and other substances are removed in the urine. A nephron is a functional unit of the vertebrate kidney which consists of a single long tubule and a ball of capillaries known as the glomerulus. The blind end of the tubule forms a cup-shaped swilling called the Bowman’s capsule which surrounds the glomerulus. The nephron will restore vital nutrients and water back into the blood while retaining the waste products. Filtration occurs when the blood pressure forces the fluid from the blood from the glomerulus to the lumen of the Bowman’s capsule. From the Bowman’s capsule, the filtrate passes through three regions of the nephron, the proximal tubule, the loop of Henle, and the distal tubule, which releases the filtered wastes into the collect duct, also known as the urine and prepares to leave the body.
The hydrostatic skeleton is similar to how nephrons work. To change an organism’s shape and further producing movement, the hydrostatic skeleton needs the pressure of its fluid and muscles. Just like the hydrostatic skeleton, filtration occurs in the nephron when pressure forces the fluid from the blood from the glomerulus to the lumen of the Bowman’s capsule. Both need pressure to start their processes.

Source: Campbell book