D4.1 - Overview of Excretory System PDF

D4.1 - Overview of Excretory System Excretory System Basic function is to regulate volume and composition of body fluids by removing wastes and returning needed substances to body for reuse Waste is any substance that is produced by body and is present in excess of body’s...

D4.1 - Overview of Excretory System Excretory System Basic function is to regulate volume and composition of body fluids by removing wastes and returning needed substances to body for reuse Waste is any substance that is produced by body and is present in excess of body’s needs Excretion: Process of separating wastes from body fluids and eliminating them ○ Respiratory system: Excretes CO2 ○ Skin: Excretes water, salts, and urea ○ Digestive system: Excretes water, salts, and lipids Feces is not a process of excretion Organs of Excretory System Kidneys ○ Located in area of lower back ○ Can survive with one kidney Ureters ○ Muscular tubes which kidneys release urine into ○ Urine is moved by peristalsis action of smooth muscle tissue into urinary bladder where it’s stored ○ Damage from bladder is controlled by two muscular rings, called a sphincter (both must relax to drain urine) Urethra ○ Urine exits bladder and body through urethra (tube) Importance of Kidneys Body’s cells break down complex compounds into smaller ones Many simple compounds can be toxic Liver removes amine group from protein - forming ammonia ○ Liver then combines ammonia with CO2 to form urea ○ Kidneys then filter out urea and uric acid from blood Urea and uric acid contain ammonia - we don’t want it! Urinary System Renal arteries branch from aorta and enter kidneys ○ “Renal” means related to kidneys Waste is filtered from blood in kidneys and sent to bladder via urethra Urinary sphincter at base of bladder releases urine into urethra where it leaves body Bladder Volume When urine volume reaches 200 mL, bladder stretches and sends message to brain, indicating that it needs to be emptied 400 mL - More urgent message produced 600 mL - Voluntary control of bladder is lost, empties itself The Kidney Has 3 different structures: ○ Renal cortex ○ Renal medulla ○ Renal pelvis The Kidney Renal tissue can be divided into two sections: ○ Outer layer: Renal cortex ○ Inner layer: Inner renal medulla, found beneath cortex Renal pelvis: Hollow chamber which joins kidney with ureter ○ Receives urine from renal tissue Embedded within renal cortex and extending into renal medulla are millions of microscopic structures called nephrons ○ Nephrons are associated with network of blood vessels ○ Responsible for filtering substances from blood and transforming it into urine Nephrons are organized into three main regions: ○ Filter ○ Tube ○ Duct Nephron Diagram Three Regions of Nephron 1. Filter Bowman’s capsule: At the top of each nephron, filtration structure Renal artery enters and splits into the glomerulus (capillaries), which also acts as a filtration device Filtrate: The filtered fluid from the glomerulus, enters the Bowman’s capsule 2. Tube Bowman’s capsule is connected to a long tube that has three sections: proximal tubule, loop of Henle, distal tubule Absorbs useful substances (more on this later) 3. Duct Collecting duct: Water conservation device, reclaims water The water reclaimed is returned to the body via renal veins Remaining filtrate is water, solutes, particles - this is urine!