Excretory System The Kidneys!

Facts about the Kidney Humans have two kidneys. They are the size of a fist. Found in the lower back on each side of the spine. The major waste product is urine. At any time, 20% of the body’s blood is in the kidneys. If for any reason a person only has one kidney, pay attention to what is taken into his/her body as it has double the work.

Objectives 1 & 2 Homeostasis & Excretory organs. The excretory system maintains homeostasis by removing metabolic wastes such as water, salt, and metabolite concentrations in the blood. the lungs, the skin, and the liver. Lungs: removes CO 2 and water vapor Skin: removes heat, water, salts Liver: removes metabolic wastes (eg. urea)

Objective 3 - the kidneys as organs of excretion: Kidneys: Functions to filter blood in order to remove cellular waste products from the blood. Also controls water balance, pH, and the body’s levels of sodium, potassium, and bicarbonate.

Objective 4 -The Urinary System (Fig 11-17, p. 374) Composed of Two kidneys, ureters, a urinary bladder, and urethra. Ureters: Tubes that carry urine from the kidneys to the bladder. Urinary bladder: A temporary storage for urine. Can hold about 600 ml. When it contains 250 ml. We become aware. Two sphincters control urine release: one involuntarily controlled by the brain and the other we learn to control as children. Urethra: Urine exits the bladder through the urethra. In males it is approx. 20 cm long. In females it is approx. 4 cm.

Objective 5 - Structure of the kidney (Fig , p. 375) A kidney has three major sections: the cortex, the medulla, and the pelvis. Cortex: The outer layer of the kidney contains the nephrons) Medulla: The inner (middle) part of the kidney Pelvis: Where urine accumulates before it travels to the bladder. (an open sac) – Urinary System Part 1 – the kidneys (5:37)

Removal of nitrogenous wastes main metabolic wastes: urea, uric acid, and creatinine (all have nitrogen as a major component). Urea is produced in the liver from the breakdown of amino acids (protein) Other waste products in the blood are uric acid, which is produced from the breakdown of nucleic acids (DNA), and creatinine, the waste product from muscle action.

Objective 6 – the Nephron ***Within the cortex and medulla, there are approx. one million tiny filters known as nephrons. Each nephron consists of five major parts: The Bowman’s capsule, the proximal tubule, the loop of Henle, the distal tubule, and the collecting duct.

Nephron Structure: The Bowman’s capsule: Blood enters the cavity of the ball-shaped Bowman’s capsule through an artery that branches to form a capillary network known as the glomerulus. Here, some plasma and small particles are forced into the surrounding cavity while larger components remain in the capillaries. Fluid in the Bowman’s capsule is referred to as nephric filtrate. Proximal tubule: The nephric filtrate enters the proximal tubule where materials required by the body are returned to the bloodstream by osmosis, diffusion, and active transport. (Water, glucose, amino acids, and ions) Tiny villi increase the surface area of this tubule.

Loop of Henle: Filtrate next moves into the loop of Henle. Its main function is to remove water from the filtrate by osmosis. The medulla has a high sodium concentration which helps draw the water out. Distal tubule: Next the filtrate moves to the distal tubule, which is responsible for tubular secretion, whereby active transport pulls substances such as creatinine and drugs out of the blood and into the filtrate. Collecting duct: Fluid from many nephrons now empty into a common collecting duct, which carries the urine to the pelvis Nephron Structure: – nephron anatomy (5:18)

– nephron function (7:55)

Objective 7 - Excretory System Disorders (p. 379) UTI - refers to urinary tract infection. It can occur in different places: 1)Bladder – Cystitis 2)Urethra – Urethritis More common in women than in men (urethral and anal openings are closer together in women). easier for bacteria from the colon to enter the urethral opening causing infection. Symptoms: Frequent and/or painful urination (burning sensation) Bloody or brown urine A tender back; Chills, fever, nausea If this infection reaches the kidneys it is referred to pyelonephritis. This can be caused by prostate obstruction (older men), or an infection, which traveled up from the bladder (young children). All UTIs are serious (can result in permanent damage to the kidneys, even kidney failure). Treatment is usually by antibiotics. UTI Video: Nurse Describes - Causes and symptoms. UTI Video: Symptoms and Prevention.

Objective 7 - Kidney Stones Form when chemicals in the urine precipitate out and form crystals More common in men than in women Caused by: UTI Insufficient water consumption Low activity levels Too much vitamin C and D Symptoms include: Severe pain in the lower back and abdomen Bloody urine Nausea and vomiting Kidney Stones: Video.

Kidney stones continued... Treatment: Patients are asked to drink lots of water Small stones can pass through the urinary tract on their own Medication can help breakdown the crystals Lithotripsy Large stones may require surgery

Dialysis (p. 377) Hemodialysis or kidney dialysis is a procedure in which blood is removed from an artery, purified, vital substances are added, and returned to a vein. (fig 11-22) Used to treat patients with renal failure (kidney failure) Wastes that are accumulating in the blood must be removed These patients are usually waiting on a kidney transplant Wastes are removed by diffusion Blood is pumped through the dialysis tubing, which is submersed in dialysate. Waste leaves the blood and enters the dialysate by diffusion. Materials can be added to the blood by the same process. The dialysate contains a lower concentration of waste; hence waste from the blood will move out.

Kidney Transplant Issues (p. 380) The first kidney transplant was 40 years ago 1112 transplants performed in Canada The major problem is finding suitable donors; most donors are victims of stroke or head trauma. Why? A doctor must have permission from the victim’s family before organs can be removed. Do you agree with the opting out policy? Do you feel it is right to remove a healthy person’s kidney? Do you feel it is right for a healthy person to sell his/her kidney? Do you agree with transplanting animal (pig) organs to humans?