D4.1 - Overview of Excretory System (Updated 2024) PDF

D4.1 - Overview of Excretory System I can… Identify the principal structures of the excretory system (kidneys, ureters, urinary bladder, urethra) Waste Excretion and Internal Equilibrium The process of cellular respiration generates a number of harmful waste products that must...

D4.1 - Overview of Excretory System I can… Identify the principal structures of the excretory system (kidneys, ureters, urinary bladder, urethra) Waste Excretion and Internal Equilibrium The process of cellular respiration generates a number of harmful waste products that must be eliminated or excreted by the body Lungs eliminate carbon dioxide The liver breaks down ingested toxins The kidneys eliminate these toxins and help maintain pH and water balance in the bloodstream ○ The excretory system is therefore comprised of a number of different systems, each of which work to eliminate different types of waste from the body. The Urinary Tract Excretion of toxins by the kidneys occurs via the urinary tract, which consists of the: ○ Bladder ○ Kidneys ○ Ureters ○ Urethra A human kidney is about the size of a fist and weighs approximately 1 pound Importance of Kidneys Our body cells break down complex compounds into smaller ones Many simple compounds can be toxic Liver removes amine group from protein, which forms 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 Tract Terminology Renal arteries: Branch from the abdominal aorta and carry blood to the kidneys Kidneys: Remove waste and extra water from the blood (as urine) and help keep chemicals (such as sodium, potassium, and calcium) balanced in the body Ureter: A tube that conducts urine from the kidneys to the bladder Urethra: The tube that carries urine from the bladder to the exterior of the body Renal veins: Carries blood from the kidney back to the heart Anatomy of the Urinary Tract 1. The aorta carries oxygenated blood to the kidneys through the renal arteries. 2. Wastes and excess water are filtered from the blood by the kidneys, where they are then conducted through ureters to the bladder. 3. As the bladder begins to fill, receptors in the brain are activated. Eventually, urine will exit the body through the urethra. 4. Once blood is filtered by the kidneys, it returns to the heart through the renal veins. Kidney Terminology Cortex: The outer layer of the kidney Medulla: The area inside the cortex Renal pelvis: The hollow area where the kidney joins the ureter Anatomy of the Kidneys A cross-section of the kidney reveals three layers: 1. An outer layer of connective tissue known as the cortex encircles the kidney. 2. An inner layer known as the medulla lies beneath the cortex. 3. A hollow chamber known as the renal pelvis joins the kidney with the ureter. The Nephron Nephron: A functional unit of the kidney Kidneys are composed of millions of slender tubules called nephrons. There are approximately one million nephrons in the kidneys Filters blood by removing waste and returning needed substances to the blood The Nephron Nephrons span the cortex and medulla of each kidney, and act to remove waste products and other solutes from the blood They also allow for the reabsorption of water and solutes back into the bloodstream, maintaining homeostasis. Any solutes and water that are not reabsorbed into the blood are excreted in the form of urine Nephron Diagram Bladder Volume When urine volume reaches 200 mL, the bladder stretches and sends message to brain, indicating that it needs to be emptied At 400 mL, a more urgent message produced At 600 mL, voluntary control of bladder is lost, empties itself