The excretory system regulates homeostasis by removing metabolic, liquid, and gaseous waste from the body. The kidneys filter blood and produce urine by removing wastes and excess water. Urine contains urea, uric acid, ammonia, hormones, dead blood cells, proteins, salts, and toxins. The kidneys filter blood through nephrons, which collect the filtrate and modify it into urine by selectively reabsorbing necessary substances and secreting others. Urine is stored in the bladder and expelled through the urethra.
2. Responsibilities of the Excretory System Excretory system is a collection of passive processes that maintain homeostasis by regulating proper chemical composition by: Removal of metabolic waste Removal of liquid waste Removal of gaseous waste
3. The Minor Constituents The skin plays a minor role as an excretory function - recognized for the trace amounts of metabolic waste sweat contains. The lung also plays a minor role – responsible for secreting gaseous wastes from the blood.
4. Process of Defecation Undigested solid and semisolid (or even liquid) waste material, known as feces, exit the large intestines into the rectum. Once enough waste builds up, the rectum contracts, expelling the waste through the anus.
5. Urination The urinary system controls urination, our body’s most active process in waste elimination. The system is composed 4 major organs: Kidneys Ureters Urinary Bladder Urethra
6. Kidneys Filters blood, redirecting wastes as urine through the ureter and to the urinary bladder. Each kidney consists of millions of nephrons – the fundamental units of the kidney.
7. Nephrons Blood enters the nephron at the Bowman’s capsule and is filtered by the glomerulus, a ball of capillaries. Bowman’s capsule collects filtrate, plasma forced out of the blood. Filtrate passes through the entire nephron becoming modified into urine.
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9. What is Urine? Urine is a liquid waste that is 95% water. The remainder consists of: Urea (majority) and uric acid Ammonia Hormones Dead blood cells, Proteins, salts, and minerals Various Toxins.
10. How Urine is Made? Filtration – blood is filtered through the glomerulus, allowing small substances to pass further: ions, urea, amino acids, etc. Reabsorption – Small solutes, necessary solutes such as water, nutrients, and salts are reabsorbed. Urine is what remains. Secretion – Substances including H+, potassium, and ammonium ions enter the tubules as part of urine. The final urine is goes to the collecting duct and into the ureters.
11. Final Destination Urine exits the kidney into the ureters, a foot long muscular duct which bring the urine to the urinary bladder. Urine is collected in the hollow, muscular urinary bladder. Voluntary sphincter muscles allow passage of urine through urethra. Urine is finally excreted from the body through the urethra.
