EXCRETION n Living cells are constantly active, they are always building up and breaking down chemical compounds. Ammonia is a byproduct of protein synthesis (and very toxic) PROTEINS ----> NH 3 cmpds ---> urea (mammals) ---> uric acid (birds & reptiles) ---> ammonia (fish) n Excretion - the process of eliminating metabolic wastes from the circulatory fluids or cells of an organism. Excretion crash course

n Excretory System has 2 functions: 1. Eliminate metabolic waste 2. Maintain homeostasis by : filtration, re- absorption & secretion. (osmoregulation) n In addition to gaseous and nitrogenous wastes, excess water, salts and organic materials must also be eliminated.

The major organs involved in filtering the blood and excreting metabolic wastes include: 1.Skin - removes heat, urea, and other wastes found in sweat. 2.Lungs - removes CO 2 3.Liver - removes toxic chemicals – alcohol 4.Kidneys - remove urea, uric acid, extra water and salts.

n Omit 3,7,8 Cortex Medulla Pelvis Renal Artery Renal Vein Ureter

The Kidney n Kidney functions to… –Regulate blood pressure –Dissolve water and other nutrients and gases. n Main purpose is to filter fluid out of the blood. 99% of which gets reabsorbed by the kidney. Only 1% gets converted to urine and excreted from the body. The Nephron does most of the filtering.

The Nephron n The nephron is the basic structural and functional unit of the kidney. n Its function is to regulate the concentration of water and soluble substances like Na salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine. n A nephron –eliminates wastes from the body, –regulates blood volume and blood pressure, –controls levels of electrolytes and metabolites, –and regulates blood pH.

n Its functions are vital to life and are regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone n 100 million nephrons

Nephron in the Kidney

Three Basic Kidney Processes Filtration n occurs in the Nephron 1. Glomerulus (starting point) –High pressure so it pushes fluid out of blood (20%) (Fluid is called Filtrate) –Empties into the Bowmans capsule –The capsule absorbs wastes, glucose, water, urea & salt –RBC & large food molecules are too big so remain in the capillaries 2. Filtrate flows into proximal convoluted tubule. (curly tube near beginning) –Organic solutes including amino acids, glucose, Na, H 2 O, and K are reabsorbed. (osmoregulation)

Reabsorption - Loop of the Henley (long loop) n Passes through 2 layers of kidney –Outter – renal cortex –Inner – medulla n Most of reabsorption happens in the loop of Henley including 3 important things… –Extracts H2) –Pumps out salts –Makes medulla hypertonic (very salty) – creates gradient n The further down the loop, the saltier it gets and the more concentrated the filtrate gets –Salt keeps coming out of the filtrate as the fluid goes back up the loop.

n Concentrated filtrate enters the distal convoluted tubule (further away curly tube) –Regulates levels of Na, K, Ca, by pumps and hormones. Secretion n The liquid that remains is Urine n Enters a line of collecting ducts going down to the medulla. n If your body is lacking H2O, pours will open that allow more H2O to be absorbed making the urine more concentrated. (or visa versa) n Urine is 95% water, 3% Urea, 2% salt, and other substances. n Collects in bladder until expelled.

n Excretory system is chemically controlled n Amount of H 2 O in urine is regulated by a hormone - ANTIDIURETIC HORMONE (ADH) n ADH is released by the PITUITARY GLAND when the body is dehydrated n ADH controls the amount of water in the blood by affecting the permeability of nephron tubules. n When ADH is present more H 2 O is reabsorbed into the blood and less urine is produced. Control of Excretion (Homeostasis)

n Alcohol inhibits the production of ADH, therefore you get very dehydrated because water isn’t reabsorbed into the blood = the HANGOVER HEAD ACHE! Hangovers

Value of Urine - Urinalysis n Can reveal diseases –ie. Diabetes, urinary tract infections n Fast, cheap analysis n Normal fresh Urine is: –Pale to dark yellow –Clear –pH usually ranges from 7.4 – 6. –< 0.1% glucose

Urinary Disorders Gout – Uric acid crystallizes in the joints causing severe pain. Exact cause unknown. Higher incidence of the disease in men, menopausal women, in people that are obese, & diabetics.

Uric acid crystals found in Urine or Joint Fluid aid in Gout diagnosis.

Kidney Stones n Can be caused by urinary tract infections, enlarge prostate, pH imbalances or an intake of too much calcium. n Stones are a hard granule of calcium, phosphate & protein n If large they will block renal pelvis or Ureter and the pressure build up will destroy the nephrons

n Urethritis – an infection in the urethra n Cystistis – an infection of the bladder n Uremia – the end result of kidney/nephron damage by some other problem (ie. Kidney stones). – Protein, WBC & RBC are found in the urine meaning the 2/3 of the nephrons are damaged. – It can lead to retention of protein wastes, salt and water. –The end result is an imbalance of ions in the blood = loss of consciousness and heart failure.

Kidney Failure