The Human Body

Excretory System

Excretion

• The process in which the body gets rid of wastes

– protein => energy and waste

The Urinary System

Kidneys: The body’s Janitors

Urinary system Actors

• Two kidneys

• A pair of Ureters

• Bladder

• Urethra

Kidneys

• Very complex

• ~500 gallons of blood go through the ~174 miles of tubules per day!

• Absorption and reabsorption is a very complex process

– deals with osmotic pressure and permeability of molecules

Function of the Kidneys

• Filter blood to remove waste from it.

• Maintain homeostasis of the body fluids

Location

• Located just above the waist, behind the stomach.

• One on each side of the spine partially surrounded by ribs.

• Each kidney is connected to a tube called a ureter, leading to a bladder.

• Bladder-a smooth muscle bag that contains a solution of waste called urine

Nephron: Unit of the Kindey

• Acts as the filter for the kidney removing impurities from the blood.

• Each kidney contains about one million of these tiny filters

• Each little filter is known as a NEPHRON

How a Nephron works…..

• Blood into the nephron carries wastes produced by body cells.

• Blood enters nephron it is under high pressure and flows into capillaries known as the glomerulus.

• Pressure causes water, glucose, vitamines, amino acids, protein waste products, salts, and ions from the blood passo ut of the capillaries into the bowmans capsule

How a nephron works…

• Blood cells and proteins are to large to pass through the walls of the capillary, so they stay in the blood.

• Liquid in the capsule passes through a u shaped tubule. All the important stuff is reabsorbed into the body.

• Conserve water…..

Make up of urine

• No glucose, amino acids, or cells

• low loss of water

• high loss of urea and hydrogen wastes

• 1-2 liters are produced per day

– increase water intake: increases urine volume

– decrease water intake: decreases urine volume

• anything smaller than proteins can be excreted

Skin

• Important for excretion and heat loss

• 2 layers

– epidermis: outer layer, cell rejuvenation, protection

– dermis: connective tissue, thick layer

• under skin is a layer of fat called:

– subcutaneous tissue

Body Homeostasis

• Nitrogenous waste from protein breakdown

• Ammonia and Urea

• Toxic and must be removed

• Salt control by absorbing and excreting

• Ph

– Bicarbonate in blood and filtering out H ions