The Excretory System http://www.youtube.com/watch?v=qxb2_d9ilEw

REGULATION Excretory & Nervous Systems Regulation within animal systems requires maintaining homeostasis- the ability of the body or a cell to seek and maintain stability within its internal environment when dealing with external changes There are several organ systems that work together to maintain an organism’s internal environment, despite changes that occur in its external environment. The nervous system maintains homeostasis by controlling and regulating the other parts of the body. The excretory system helps regulate the concentration of water and other components of body fluids.

Homeostasis Every organ system plays a role in maintaining the constancy of the internal environment. Examples: Blood level of nutrients, blood pressure, heart activity, wastes must not be allowed to accumulate, body temperature must stay within normal limits

Homeostatic Control Mechanisms Communication within the body is essential for homeostasis. Homeostasis is accomplished primarily by: Endocrine system (blood borne hormones) Nervous system (electrical signals)

Negative Feedback vs. Positive Feedback Mechanisms Negative Feedback Mechanism – The net effect of the response to the stimulus is to shut off the original stimulus or to reduce its intensity. Examples: Thermostat or body temperature, heart rate, blood pressure, breathing rate, blood levels Positive Feedback Mechanism – Feedback that tends to cause a variable to change in the same direction as the initial change; enhances the stimulus Examples: Blood clotting, birth of a baby More rare in the body

Excretion Excretion – the process by which metabolic wastes are eliminated from the blood One part of the many processes that maintain homeostasis. Every cell in the body produces metabolic wastes, such as excess salts, carbon dioxide, and urea

Excretory System Function The Excretory System Maintains Homeostasis In 3 Steps: Filtration- Filters substances from the blood Reabsorption- Regulate the chemical composition of body fluids by retaining the proper amounts of water, salts, and nutrients Secretion- Elimination of wastes in the form of urine

Evolutionary Trends in Excretion Aquatic Invertebrates Excretory System Evolutionary Trends in Excretion Simple Complex Animal Taxon Aquatic Invertebrates Worms and Mollusks Insects Vertebrates Release Wastes By… diffusion to remove waste across their cell membranes directly into the water Use of nephridia- tiny pores along the body excrete wasste Using malpighian tubules to collect and excrete wastes Use of kidneys, ureters, and a bladder to collect and excrete waste Picture of system   Examples Sponges, jellyfish, planaria Earthworm, clam, octopus Grasshopper, ants, bees mammals, birds, reptiles, fish, amphibians

Main Organs of the Excretory System Kidneys Renal artery Renal Vein Ureters Urinary Bladder Urethra

Major Organs of the Excretory System Kidneys (renal = kidney)- Located on either side of the spinal column near the lower back. Paired organs that receive blood via the renal artery The main filtering units are tissues called nephrons that separate the components of the blood Every 45 minutes kidneys filter all the blood in your body Excess water and urea in the form of urine leave the kidney via the ureter where it leaves as urine out the urethra Filtered blood leaves kidneys and returns to circulation carrying nutrients, salts, and water via the renal vein

Ureter A tube, called the ureter, leaves each kidney carrying urine to the urinary bladder

Urinary Bladder The urinary bladder is a saclike organ where urine (a mixture of urea, water, and salt) is stored before being excreted. When bacteria get into the bladder or kidney and multiply in the urine, they may cause a UTI. Foley Catheter

Urethra Tube that carries urine from bladder to the outside of the body The state of the reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory fibers from the bladder and urethra. At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder. At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge.

Levels of Organization Excretory System Levels of Organization Nephrons Kidneys, Bladder, Ureter, Urethra Excretory Renal cells, bladder cells, etc…

Kidney Stones Sometimes substances such as calcium, magnesium, or uric acid salts in the urine crystallize and form kidney stones. When kidney stones block the ureter they cause great pain. Often treated using ultrasound, in which the sound waves pulverize the stones into smaller fragments Prevent by: drink lots of water, diet lower in protein (N), sodium

Releases ADH into bloodstream ADH Process Antidiuretic Hormone Hypothalamus | Tells pituitary that amount of water in blood is low. Tells pituitary that amount of water in blood is high. High amounts of water in blood and low amount of urine produced. Low amounts of water in blood and high of urine produced Pituitary | Stops releasing ADH into bloodstream Releases ADH into bloodstream Kidneys | Reabsorbs more water. Reabsorbs less water.

Other Organs: Lungs of the respiratory system remove CO2 from blood. Skin of the integumentary system excretes water, urea, salts, and other wastes through sweat. The circulatory system brings wastes to the lungs, kidneys, and skin for excretion.

Kidney Damage Humans have two kidneys and can survive with only one. If both kidneys are damaged by disease or injury, there are two ways to keep an individual alive. Kidney Transplant Kidney Dialysis Machine Expensive Time consuming (3 X /week for few hours)