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