Bowman's capsule
The cup-shaped first part of the kidney tubule found in the outer cortex region
Blood vessels
The tubes through which blood is carried around the body eg arteries, veins and capillaries
Renal tubule
The main part of the kidney tubule where reabsorption takes place, found in the medulla of the kidney
Capillary
Very small blood vessel with walls made of a single layer of epithelial cells. Exchange of materials, such as nutrients, oxygen and carbon dioxide, takes place between the blood and the cells of the body across the capillary walls.
Glomerulus
The knot of capillaries in the Bowman's capsule.
Medulla
The inner region of the kidney containing the renal tubules
Nephron
The kidney tubule in which reabsorption of substances and the balancing of the concentration of the blood takes place
Hormone
A chemical messenger produced by a particular gland or cells of the endocrine system. Hormones are transported throughout the body in the blood stream but they produce a response only in specific target cells
Cortex
The outer region of the kidney containing the Bowman's capsules
Antidiuretic hormone
Hormone produced in the hypothalamus that is produced by the pituitary gland when the body needs to lose less water. It affects the permeability of the distal convoluted tubule and the collecting duct of the kidney to water
How the kidney works
Each kidney contains about a million tiny structures called nephrons. A nephron has a cup-shaped Bowman's capsule leading into the renal tubule. The two sections of each nephron extend across the two different regions of the kidney:
- the Bowman's capsules are found within the outer cortex region
- the renal tubules run from the cortex into the darker medulla
How does the kidney balance the blood?
Placed end to end, the nephrons of one kidney would stretch about 8 km. Their function is to remove waste products such as urea and balance the water and mineral ion concentration of the blood. How does the process work?
A branch of the renal artery supplies the nephrons with blood. In the Bowman's capsule, the artery splits up into a network of capillaries called the glomerulus. These capillaries join into a single vessel again as they leave the capsule, and then split into a second set of capillaries that are wrapped around the renal tubule. The blood leaves the tubule in the renal vein.
Water regulation is controlled by Anti-Diuretic Hormone (ADH). For more information see ADH and control of the water balance.
Question 4
a) When blood leaves the capsule, the concentration of some substances has changed. Give four substances whose concentration has changed and say what has happened to the concentration.
b) What causes substances to pass out of the blood into the renal capsule?
c) Look at the picture below. Click on the picture where you would expect to find the greatest concentration of glucose in the renal tubule.
d) As the glomerular filtrate passes along the tubule, most of the water is absorbed back into the blood. How does this affect the concentration of urea?