The keeping of constant conditions in the body => e.g water intake being equal to exhaled air, sweat and cell respiration
Is important because cells will only function properly if they are bathed in tissue fluid => provides them with their optimum conditions
Factors that affect tissue fluid: pH (affects activity of cell's enzymes), body temp. (37 degrees), being too dilute (causes swelling of water)
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The urinary system diagram
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The urinary system
Each kidney is supplied with blood via a short renal artery => leads straight from body's main artery (aorta) => suggests that is at high pressure
Inside kidneys = blood is filtered + cleaned blood passes out via each renal vein
Urine passes out of kidney via two tuves => ureters (stored in a muscular bag called the bladder)
Bladder has a tube leading to the outside = urethra
Wall of urethra contains two ring-like muscles => sphincters
Sphincters can contract to close urethra and hold back urine
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The kidneys diagram
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The kidneys
Darker outer region = cortex
Filtering units = nephrons
Nephrons run down the middle layer of the kidney = medulla
Medulla has bulges called pyramids that consist of tubules that eventually lead to the tips of these pyramids and empty urine into a space called the pelvis
Pelvis is connected with the ureter in which carries the urine to the bladder
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Nephrons
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The Nephron (part 1)
At the start of the nephron = hollow cup => Bowman's capsule
Bowman's capsule surounds a ball of blood capillaries known as the Glomerulus
It is here that blood is filtered => blood enter the kidney via the renal artery, which divides into smaller and smaller arteries
Smallest arteries (arterioles) supply the capillaries of the glomerulus
A blood vessel with a smaller diameter carries blood away from the glomerulus => capillary networks which surround other parts of the nephron
Because of resistance to flow caused by glomerulus, pressure of the blood in the arteriole leading to the glomerulus is very high
This pressure forces fluid from blood through walls of the capillaries + bowman's capsule and into the space of the bowman's capsule
Blood and glomerulus and space in capsule are separated by two layers of cells => act like a filter, allowing water, ions and small molecules to pass through whilst holding back blood cells and large molecules
Fluid that enturs the capsule space is called the GLOMERULAR FILTRATE
This process that separates different sized molecules under pressure is called ULTRAFILTRATION
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The Nephron (part 2)
There are two coiled regions of the tubule (aka. cortex) that are separated by a U shaped loop that runs down into the medula => Loop of Henle
After the second coiled tubule, several nephrons join up to form a collecting duct where the final urine passes out into the pelvis
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