Performs the vital function of removing the organic waste products generated by cells throughout the body. –Regulates blood volume, pressure, and pH –Regulates plasma concentration of ions –Conserving valuable nutrients –Excreting unnecessary waste (salts and nitrogen) The Urinary System (17.1)

The Urinary System (17.2/10) Kidneys (17.3) –Filter urea out of the blood –Control water balance in the blood –Produce urine Ureters –Tubes that carry urine from the kidneys to the urinary bladder

The Urinary System (17.10) Urinary Bladder –A flexible sack that stores urine until excretion Urethra –A tube that exits through male and female genitalia –Expulses urine from the system

Your kidneys are located higher than you may think… (17.2)

Inside the kidney (17.2)

How much urine is produced per day? It varies depending on the following: Quantity of water ingested Types of food ingested Quantity of water eliminated through perspiration Level of physical activity Ambient temperature

Homeostasis of body water (17.4) Too little waterToo much water ↓ blood volume↑ blood volume not enough blood Tissues deprived of O 2 and nutrients ↑ blood pressure Heart attack, stroke, etc DEATH

How do the kidneys maintain homeostasis of body water? (17.4) - EXCRETE wastes (eg. urea, uric acid) - Selectively reabsorb (into the bloodstream) substances that are in short supply (eg. Water, salts, sugar).

Function of the Kidneys (17.3): The main function of the kidneys is to filter blood and eliminate wastes –Kidneys are selectively permeable: some substances pass through them, others do not this allows the kidneys to filter the blood: unwanted material (waste) is kept inside the kidney and disposed of through the ureters wanted material remains in the bloodstream or is selectively reabsorbed into the bloodstream

Selective reabsorption of water ADH (antidiuretic hormone) is released from the pituitary gland and travels through the blood to the kidney where it promotes water reabsorption, thus preventing its loss in the urine.

Anatomy of the kidney (17.2) Renal artery: –Blood enters the kidneys here –Branches off to form renal arteriole which leads blood into the nephron Renal vein –Receives purified/filtered blood from the kidney

Cross Section of a Kidney (17.2)

Anatomy of the Kidney: - the nephron (17.3/5) where filtration occurs in the kidney each kidney contains nearly 1 million nephrons located in the outer layer (renal cortex) of the kidneys Consists of the glomerulus, the bowman’s capsule and the collecting tubules

Anatomy of the Kidney: - the nephron (17.5) Glomerulus –Ball of vessels –Wastes, water and minerals diffuse from the blood into: Bowman’s Capsule –Surrounds the glomerulus –Receives the diffused material from the glomerulus Collecting tubule –Collects remaining waste that was not reabsorbed in to blood Proximal convoluted tubule Distal convoluted tubule

Where does the excretion of wastes and reabsorption of water occur? (17.8) During this journey water is then reabsorbed, into the renal venule Wastes are excreted into Bowman’s capsule, and continue into the collecting tubule Bowman’s Capsule Animation:

filtrate (water, salt) BOWMAN’S CAPSULE MEMBRANE BASEMENT sand, salt, water residue: sand ultrafiltrate (water,salt, sugar, urea) large molecules (proteins), salt, sugar, urea, water residue: large molecules (proteins) PAPER FILTER ERLENMEYER FLASK (17.6)

Filtration Process (17.6) 1) Blood enters the kidneys through the renal arteries, 2) The renal arteries branch into smaller arterioles which bring blood to the nephron. 3) Inside the nephron, the arterioles branch into an even smaller ball of capillaries called the glomerulus. 4) Wastes, water and minerals diffuse from the capillaries (glomerulus) into Bowman’s capsule

Filtration Process (17.6) 5) Necessary salts and water will re-enter the blood stream at the venules which flow into the renal vein and then the inferior vena cava. 6) The remaining waste passes through the proximal convoluted tubule, loop of Henle, and DCT and is then collected in the collecting tubule 7) The collecting tubules empty into the ureter, which takes waste to the bladder where it is stored. 8) When the bladder becomes full it will send a signal to the brain. 9) The brain then sends a signal back to the bladder for the waste to be excreted out of the body through the urethra.

Overview of the Urinary System