The Excretory System http://www.benet.org/teachers/meraci/Biology/FrBioReviews/Review-Excretory_System/HumanKidney.jpg http://www.benet.org/teachers/meraci/ExcretorySystemBio.gif http://www.crews.org/curriculum/science/human_6.gif

A System Based on Regulation In general, excretory systems help maintain homeostasis in organisms by regulating water balance and by removing harmful substances. Osmoregulation- the absorption and excretion of water and solutes so that proper water balance and osmotic pressure is maintained between the organism and its surroundings. Homeostasis-

Evolution of the Excretory System 1. Contractile Vacuoles 2. Flame cells 3. Nephridia (or metanephridia) 4. Malpighian tubules 5. Kidneys http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/darkfield/images/grasshoppermalpighian1.jpg http://www.troy.k12.ny.us/faculty/smithda/Media/neph_earthw.jpg

What is being excreted? Nitrogenous wastes  NH3  Urea or Uric acid Water Salts http://www.uyseg.org/greener_industry/pages/ammonia/images/ammonia.gif http://jetex.org/cja/images/propellants/fuel-chemical_structure-urea.gif

Major Components of the Human Excretory System Skin The Urinary System - Kidneys - Ureter - Urinary Bladder - Urethra

The Skin The largest organ in the body ( large SA) 2.5 million sweat glands Three layers: Epidermis, Dermis, Subcutaneous (fatty) tissue Functions: 1. Excrete excess salt, water, and urea 2. Regulate body temperature

The Skin Contd. The sweat gland is a tubular structure tangled with capillaries.  This close association of tubes allows wastes (namely water, salts and urea) to diffuse from the blood  & into the sweat gland. Then, when body temperature rises, the fluid is released from the gland, travels through the duct, and reaches the skin surface through openings called pores. http://www.medicinenet.com/images/illustrations/skin.jpg

The Urinary System http://images.main.uab.edu/healthsys/ei_0273.gif

The Nephron: the Kidney’s subunit Glomerulus Bowman’s capsule Convoluted tubule (distal and proximal) Loop of Henle Collecting duct http://www1.shore.net/~straub/labsk_nephron.gif

The Creation of Urine 1. Filtration 2. Secretion 3. Reabsorption

Filtration Blood enters the glomerulus and pressure forces water and solutes through the capillary walls and into the Bowman’s capsule. The filtrate then flows into the convoluted tubule.

Secretion As the filtrate passes through the proximal tubule and distal tubule additional materials from the interstitial fluid join the filtrate. “Selectively secreted” into the convoluted tubule by both active and passive transport.

Reabsorption Movement up and down the loop of Henle. The filtrate descends through the collecting duct towards the renal pelvis. Once drained into the renal pelvis it is considered concentrated urine.

Final steps The urine travels through a pair of ureters to the urinary bladder The urine is held here until excreted out of the body by way of the urethra

Hormonal Influence Antidiuretic hormone (ADH)- increases the reabsorption of water by the body and increases the concentration of salts in the urine. Aldosterone- increases both the re-absorption of water and Na+.

Diseases Renal (kidney) failure results when the kidneys are not able to regulate water and chemicals in the body or remove waste products from your blood. Acute renal failure (ARF) is the sudden onset of kidney failure. This can be caused by an accident that injures the kidneys, loss of a lot of blood, or some drugs or poisons. ARF may lead to permanent loss of kidney function. But if the kidneys are not seriously damaged, they may recover. Chronic kidney disease (CKD) is the gradual reduction of kidney function that may lead to permanent kidney failure, or end-stage renal disease (ESRD). You may go several years without knowing you have CKD.

Nephritis- an inflammation of the glomeruli, due to a number of possible causes, including things like strep throat. Symptoms include bloody urine, scant urine output, and edema (swelling/puffliness). Another, more severe form, is due to an autoimmune attack on the glomeruli. Other types of nephritis affect the tubules

Urinary tract infections (UTIs) are caused by Gram negative bacteria such as E. coli in the urinary tract. Women get UTIs more often than men. UTIs are treated with antibiotics. Drinking lots of fluids also helps by flushing out the bacteria.The name of the UTI depends on its location in the urinary tract. An infection in the bladder is called cystitis. If the infection is in one or both of the kidneys, the infection is called pyelonephritis. This type of UTI can cause serious damage to the kidneys if it is not adequately treated

Diseases Contd. Kidney stones- is the term commonly used to refer to stones, or calculi, in the urinary system. Stones form in the kidneys and may be found anywhere in the urinary system. They vary in size. Some stones cause great pain while others cause very little. The aim of treatment is to remove the stones, prevent infection, and prevent recurrence. Both nonsurgical and surgical treatments are used. Kidney stones affect men more often than women.

Nephrosis- also affects the glomeruli, and is characterized by excretion of abnormally large amounts of protein (often causing “foamy” urine) and generalized edema (water retension/swelling) throughout the whole body, especially noted as “puffy” eyelids. Because these people’s kidneys often do not handle sodium properly, a low-salt diet is usually prescribed.

Resources 1.http://biology.clc.uc.edu/courses/bio105/kidney.htm 2.http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEXCRET.html 3.http://www.sirinet.net/~jgjohnso/urinary.html 4.http://www.hartnell.cc.ca.us/faculty/asteinhardt/mywebs/excretory_organs.htm 5. http://www.borg.com/~lubehawk/hexcrsys.htm 6.http://library.thinkquest.org/19347/frameless_excretory_and_urinary_system.htm