EXCRETORY SYSTEM

Excretory System How does the excretory system maintain homeostasis? It regulates heat, water, salt, acid-base concentrations and metabolite concentrations

Removal of Metabolic Waste The Kidney’s play a crucial role in removing waste, balancing blood pH, and maintaining water balance. The Liver transforms ingested toxins and hazardous products of protein breakdown into compounds that can be eliminated by the kidneys. The Lungs remove carbon dioxide.

ORGANS OF EXCRETION Skin and associated glands: Removes heat and salts Lungs: Removes carbon dioxide

ORGANS OF EXCRETION Kidneys (part of the Urinary system): MAJOR excretory organs that excrete metabolic wastes, regulate water-salt balance and acid-base balance. Liver: Removes metabolic wastes

Males vs. Females Male’s urethra= sperm and urine Female’s urethra= urine and reproductive tract are separate.

PARTS OF THE URINARY SYSTEM Kidneys: filter blood to produce urine. Ureters: carry urine from the kidneys to the urinary bladder

PARTS OF THE URINARY SYSTEM Urinary Bladder: stores urine. Urethra: carries urine from the bladder to the outside of the body.

IMPORTANT BLOOD VESSELS Renal Artery: carries contaminated blood into the kidney. Renal Vein: carries purified blood from the kidney and returns it back into circulation by way of the inferior vena cava.

The Kidney

KIDNEY PARTS Cortex: the outer part Medulla: the middle part Pelvis: the inner cavity where urine collects

MAJOR FUNCTIONS OF KIDNEYS 1. Filters blood of: Ø Urea – formed in the liver from the breakdown of ammonia Ø Creatinine – formed in the muscles Ø Uric Acid – formed as a result of the breakdown of nucleic acids (DNA and RNA)

MAJOR FUNCTIONS OF KIDNEYS 2. Controls the balance of water in our bodies 3. Regulates pH of the blood 4. Regulates the concentration of dissolved ions in the blood

MAJOR FUNCTIONS OF KIDNEYS 5. Secretes a hormone that causes a production of red blood cells 6. Activates Vitamin D production in the skin

NEPHRONS Tiny filtering units called nephrons fill the cortex and medulla of the kidney. Each kidney contains 1 to 1.25 million nephrons.

Each nephron is composed of 5 main parts: Bowman’s capsule, proximal tubule, loop of Henle, distal tubule & collecting duct

Nephron Afferent arteriole (bringing blood in) Glomerulus: ball of capillaries Efferent arteriole (blood out to Loop of Henle) Bowman’s Capsule: carries filtrate (filtered waste) Proximal convoluted tubule Loop of Henle: exposed to capillaries to reabsorb water Distal Convoluted tubule Collecting duct

How urine is made Filtration Glomerulus to Bowman’s Capsule Small substances pass (ions, water, glucose, amino acids) through diffusion Large substances can’t pass (proteins, blood cells)

How urine is made Reabsorption Elimination Reabsorption from tubules through capillaries Salts, water, nutrients Left over filtrate is urine. Elimination The fluid than enters the collecting duct as urine. It passes through the pelvis into the ureter. Most of the water, ions and useful nutrients (glucose, amino acids) have been reabsorbed.

How urine is made Secretion To maintain pH, H+, potassium, ammonium ions secreted into tubule

Hormones of Kidney Vassopressin (antidiuretic hormone - ADH) Controls volume of urine Reabsorbs water from collecting duct Concentrates urine if dehydrated Aldosterone Reabsorbs sodium and water increases blood pressure and volume

Control of Water Balance When water levels are too low: The hypothalamus stimulates the pituitary gland to secrete a hormone called anti-diuretic hormone (ADH). ADH travels through blood to kidneys.

Control of Water Balance 2) ADH increases the permeability of the tubules and collecting ducts 3) More water is reabsorbed into the blood so the urine is more concentrated

Control of Water Balance When water levels are too high: Hypothalamus doesn’t stimulate ADH secretion Little water is reabsorbed into the blood so the urine is more dilute.

200mL: stretches slightly and signals to the brain. 400mL: almost full and stretch receptors send a more urgent message. 600mL: voluntary control is lost.