Structure of Kidney
A kidney is made up of a pelvis, renal cortex and medulla. It has many nephrons. Nephrons are sections of capillaries and tubules that clean blood.
Ultrafiltration & Selective Reabsorption🧐
There are two types of filtration that happen in the kidney, these are ultrafiltration and selective reabsorption, you will have to know about both in detail in I/GCSE Biology. Ultrafiltration happens at high pressures between the glomerulus and Bowman’s capsule. Large molecules such as blood cells and proteins stay in the blood whereas smaller molecules such as glucose, urea, ions and water are pushed through. The substances move through the first convoluted tubule where selective reabsorption begins. All the glucose is reabsorbed and sufficient water is reabsorbed, depending on the concentration of ADH. The liquid continues to be pushed through the nephron via the Loop of Henlé to the second convoluted tubule. Anything left at the end of the second convoluted tubule is moved along the ureter to the bladder where it stored before excretion through the urethra.
ADH🧪
ADH stands for Anti-Diuretic Hormone and is secreted by the pituitary gland in the brain – it changes the permeability of the walls of the tubules in the nephrons so more or less water can be reabsorbed. When the concentration of water in the blood is low, more ADH is secreted by the pituitary gland to make the walls more permeable and more water is reabsorbed. When normal levels have been reached, the pituitary gland stops secreting ADH in negative feedback. When we are over-hydrated, less ADH is secreted so walls become less permeable and we excrete more water.
Reference: https://upload.wikimedia.org/wikipedia/commons/d/d6/Blausen_0592_KidneyAnatomy_01.png
Drafted by Catrina (Biology)