HUMAN ORGANS OF EXCRETION

LUNGS  Excrete carbon dioxide and water  These are the wastes of cellular respiration

LIVER  Removes toxic substances from the blood  Disposes of Hemoglobin – old RBC’s are broken down in the liver and hemoglobin is released  The liver converts the hemoglobin to bile pigments (waste products) which are eliminated in the feces

LIVER  Disposal of nitrogenous wastes Breaks down excess amino acids (deamination) Breaks down excess amino acids (deamination) The amino group is converted to ammonia and then to urea The amino group is converted to ammonia and then to urea Urea is transported to the kidneys by the blood Urea is transported to the kidneys by the blood

SKIN  The excretory structures of the skin are the sweat glands  The sweat glands are in contact with capillaries

Water, salt and some urea diffuse from the blood into the sweat gland and are excreted as perspiration Perspiration acts to regulate body temperature by removing excess heat

URINARY SYSTEM  Includes kidneys, ureters, urinary bladder and urethra

URINARY SYSTEM The kidneys (2) are bean shaped organs, approximately 10 cm long and are located below the diaphragm near the back

 Kidneys have 2 main functions: 1. Remove wastes of cellular metabolism form the blood 2. They regulate the concentrations of substances found in body fluids

 Blood vessels carry blood to the kidneys, where wastes and other dissolved substances are removed from the blood  The wastes are excreted from the body and the useful substances are reabsorbed

Kidney Structure  Kidneys consist of microscopic structures called NEPHRONS.

A NEPHRON is made of : Glomerulus: a network of capillaries Bowman’s capsule: cup- like structure surrounding the glomerulus

 A nephron works in 2 stages: Filtrations stage: water, minerals, salts, urea, amino acids and glucose are filtered out of the blood Filtrations stage: water, minerals, salts, urea, amino acids and glucose are filtered out of the blood

 Reabsorption stage:  water, minerals, amino acids and glucose are reabsorbed by active transport from the renal tubule into the capillaries

 The remaining material is urine which contains water, salt and urea

URETERS  Tubes that carry urine from the kidney to the bladder

URINARY BLADDER  Stores urine

URETHRA  Tube that carries urine from the bladder to the outside of the body

Malfunctions  Kidney Diseases:  Include various conditions in which the kidneys are unable to properly excrete nitrogenous wastes

MALFUNCTIONS  Kidney stones:  Substances crystalize out of the urine in the urinary tract or in the kidney  Some pass out in the urine on their own  Some can be shattered with lasers or sound waves  Some are surgically removed

 Dialysis – can some times be used to treat various kidney diseases  Kidney transplants are also successful