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The Kidney
The Kidney
The kidney is part of the excretory system (urinary system) and plays a crucial role in osmoregulation, or water and ion balance in the body.
What kind of beans are these?
What shape is this swimming pool?
Small group discussion: with a few classmates, choose either kidney beans or the swimming pool. Come up with ways that a human kidney is like or is not like the bean or the pool. Be prepared to share with the class!
The Kidney
The Excretory System
• The excretory system consists of two fist sized kidneys located in the lower back on either side of the spine. • Kidneys receive blood from the renal arteries and blood leaves them via the renal veins. • The waste products filtered from the blood are released into the ureters, which carry the fluid to the bladder for temporary storage. • Drainage of the urine from the bladder is controlled by two sphincters (one voluntarily controlled, the other involuntary) leading to the urethra.
The Kidney
Kidney Function: Waste FiltrationThe kidney's principal function is to remove cellular waste products from the blood:
Celluar Metabolic Wastes
(all contain nitrogen)
CREATININE
URIC ACID
UREA
Amino Acid Breakdown
DNA and RNABreakdown
N compounds are potentially harmful to the body and must be removed
Waste Product from Muscle Action
The Kidney
Kidney StructureIn addition to removing nitrogenous wastes, the kidney is structured in such a way that it is also a major homeostatic organ:• controls water balance• controls blood pH• controls ion balance in blood (sodium, potassium, bicarbonate, and calcium)• secrete hormones
The kidney has three main sections:• an outer cortex• inner layer called the medulla• renal pelvis where urine accumulates before travelling to the bladder
contain functional units called nephrons
The Kidney
The NephronKidneys contain about one million of these tiny filters that loop from the cortex to the medulla and back again.
There are 5 major parts to a nephron, all belonging to the set of tubes that carry the blood filtrate (what becomes urine).
1) Bowman's Capsule surrounds a ball of capillaries called the glomerulus from which blood plasma and small particles enter the ball shaped capsule.2) Proximal Tubule receives the fluid, now called nephric filtrate, from the Bowman's Capsule. This is where the majority of reabsorbtion of essential particles from the filtrate occurs.3) Loop of Henle the descending portion dips down into the renal medula, and the ascending portion returns to the cortex. This is where water is reabsorbed from the filtrate. 4) Distal Tubule location of Tubular Secretion, where substances such as hydrogen ions, creatine and drugs join the filtrate.5) Collecting Duct fluid from several distal tubules drains here and is sent to the renal pelvis.