Organisms Respond To Changes In Their Environment: - Control of Blood Water Potential

- Structure Of The Nephron - 

Osmoregulation = the homeostatic control of the water potential of the blood. 

Structure of the mammalian kidney

In the mammal there are two kidneys found at the back of the abdominal cavity. 

A section through the kidney 

Fibrous Capsule = outer membrane that protects the kidney 

Cortex = lighter coloured outer region made up of renal (Bowman's) capsule, convoluted tubles and blood vessels. 

Medulla = darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels 

Renal pelvis = funnel-shaped cavity that collects urine into the ureter 

Ureter = tube that carries urine to the bladder 

Rental artery = supplies the kidney with blood from the heart via the aorta

Renal vein = returns blood to the heart via the vena cava 

Structure of the nephrons 

Renal (Bowman's) capsule = closed end at the start of the nephron. It cup-shaped and surrounds a mass of blood capillaries - Glomerulus. The inner layer of the renal capsule made of specialised cells - podocytes 

Proximal convoluted tubules = series of loops surrounded by blood capillaries. It's walls made epithelial cells - have microvilli 

Loop of Henle = long hairpin loop extends from cortex into medulla of kidney and back again. Surrounded by blood capillaries 

Distal convoluted tubule = series of loops surrounded by blood capillaries. Walls are made of epithelial cell - surrounded by fewer capillaries than proximal tubule. 

Collecting duct = tube number of distal convoluted tubules from a number of nephrons empty. Lined by epithelial cells and becomes increasingly wide as it empties into the pelvis of kidney. 

Associated with each nephron there are number of blood vessels:

Afferent arteriole = tiny vessel arise from renal artery - supplies the nephron with blood // Afferent arteriole enters the renal capsule of the nephron 

Glomerulus = many-branched knots of capillaries from which fluid is forced out of the blood. Glomerulus capillaries recombine.

Efferent arterioles = tiny vessel leaves the renal capsule // smaller diameter than afferent arteriole causes an increase in blood pressure within the glomerulus. Efferent arterioles carries blood away from the renal capsule. 

Blood capillaries = concentrated network of capillaries surrounding the proximal convoluted tublue, loop of Henle mineral salts, glucose, and water. These capillaries merge to form venules, merging to form the renal vein.