Human Excretory System I The human excretory system

Human Excretory System I. The human excretory system has two major excretory functions: A. Remove cellular wastes B. Maintain homeostasis -keep a stable internal environment

II. There are four types of waste products: A. CO 2 B. H 2 O C. Urea (nitrogenous waste) D. Mineral salts III. There are four organs of excretion: A. Liver B. Kidneys C. Lungs D. Skin

IV. Liver A. The liver is a large, brown gland located underneath the diaphragm. B. The liver has three jobs: 1. Detoxification - The liver detoxifies blood that flows through it. Harmful substances such as drugs and alcohol are changed into inactive or less poisonous forms. These less toxic forms are returned to the blood and eventually excreted by the kidney.

2. The liver is responsible for the breakdown of worn-out red blood cells. 3. In the liver excess amino acids are broken down into urea. Urea will enter the blood to be taken to the kidney from which it is excreted.

V. Kidney – Components of the Urinary System A. The kidneys are paired, bean-shaped organs approximately 10 cm in length. The kidneys lie in a relatively unprotected spot against back muscles on either side of the vertebral column. B. The bladder stores urine. It is a single, midline, muscular organ which lies in the lower abdomen above the pubic bone. C. The tube that carries urine from the kidney to the bladder is the ureter. D. The tube that carries urine from the bladder to the outside world is the urethra. It is found in both male and females. In males, however, it also carries semen.

E. Anatomy of the urinary system: Kidney (makes urine) Ureter (transports urine from kidney to bladder) Bladder (stores urine) Urethra (tube for exit)

VI. Anatomy of the Kidney – The kidney has three parts. In a length-wise section of the kidney you can see the cortex, medulla, and pelvis. Cortex (blood filtered here) Pelvis (urine collects here) Medulla (collecting ducts) Ureter http: //www. youtube. com/watch? v=Wtr. Yotj. Yvt. U

VII. Functions of the Kidney A. The kidney removes wastes (urea) from blood. B. The kidney controls the concentration of most of the constituents of body fluid. C. Higher magnification of the kidney reveals that the kidney is made up of millions of small units called nephrons. Nephrons are responsible for filtering of the blood. Nephrons are considered the functional units of the kidney. D. A nephron is composed of a series of tubules which filter blood.

Nephron: Bowman’s capsule Glomerulus Capillaries – takes out “good stuff” water, glucose, amino acids) Renal artery Renal vein Collecting duct (to renal pelvis and ureter) – carries salts and urea Loop of Henle

Bowman’s Capsule and Glomerulus: Bowman’s capsule H 2 O, Glucose, Amino acids, Urea, Salts Glomerulus

START E. At one end of the nephron is Bowman’s capsule, which leads into a system of tubules which eventually empty filtrate into the Collecting duct. END F. In the nephron, blood from an arteriole off of the renal artery enters the Bowman’s capsule and forms a tuft (ball) of capillaries called a glomerulus. Another arteriole exits Bowman’s capsule and forms a capillary network over a nephron’s tubules. The capillaries eventually unite to form a venule which contains filtered blood exiting the nephron. Venules will return filtered blood to the systemic circulation via the renal vein.

G. How is blood filtered? In the Bowman’s capsule, filtrate from blood (liquid part of the blood minus the large proteins and cells) passes from capillaries to space in Bowman’s capsule. The filtrate travels through the tubules of the nephron. As it does, H 2 O, glucose, and amino acids are reabsorbed back into the capillary network around the tubules and returned to the bloodstream. Wastes, such as urea, H 2 O, and mineral salts, stay in the tubule and are deposited as urine in the collecting duct. From the collecting duct urine is deposited in the pelvis. The ureter takes the urine from the pelvis to the bladder. On occasion, the urine exits the body from the bladder through the urethra.

VIII. Lungs A. CO 2 and H 2 O which are waste products of respiration diffuse from the blood into the alveoli. These gases are removed from the body when you exhale.

IX. Skin A. The skin secretes sweat. Sweat is composed of 98% H 2 O and 2% salts and urea. C. There are four functions of the skin: 1. Excretes sweat (urea) 2. Protection 3. Prevents dehydration 4. Temperature regulation - evaporation of water on body cools off body

Skin:

I. Cirrhosis results from overloading the liver with harmful substances such as alcohol. The liver enlarges to try to detoxify the huge amounts of alcohol, however, this decreases blood flow through the liver (greater area for same amount of blood to flow though). A result of the decrease in blood flow is that there is a limit on the amount of purification that can be performed. Consequently, toxic substances accumulate.

II. Kidney Stones occur when substances (salts) crystallize out of urine. If the stones are too big to pass out with urine then they must be either surgically removed or broken up by laser treatments.

III. Dialysis is performed using an artificial kidney machine. Dialysis is needed when both kidneys fail because excess fluid and waste build up. The machine is used to filter blood and is used several hours every week or two as necessary. In cases of kidney failure, the machine is life-saving.

IV. Gout is a disease resulting from excess uric acid in the blood. Often the uric acid is deposited around joints causing swelling and inflammation. The symptoms are similar to arthritis. The disease is linked to an excess of protein intake.

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