D4.3 Maintaining Excretory System (Updated 2024) - PDF

D4.3 - Maintaining Excretory System I can… Describe the function of the kidney in excreting metabolic waste Identify the role of antidiuretic hormone (ADH) and aldosterone in water & sodium ion reabsorption, excretion and blood pressure regulation. Water Balance Osmo...

D4.3 - Maintaining Excretory System I can… Describe the function of the kidney in excreting metabolic waste Identify the role of antidiuretic hormone (ADH) and aldosterone in water & sodium ion reabsorption, excretion and blood pressure regulation. Water Balance Osmotic pressure: Force generated by osmosis ○ Affects exchange of materials between cells and blood Solute concentration of blood remains constant, despite variations in amount of water consumed Water Balance If you… Drink too much water - Kidneys allow more water into urine Don’t drink enough water - Water is scarce and kidneys conserve water by producing concentrated urine Regulating ADH Antidiuretic hormone (ADH): Increases the permeability of the collecting ducts to H2O ○ Regulates water reabsorption in the nephron If ADH is released, more concentrated urine is produced ○ ADH makes upper part of distal tubule and collecting duct permeable to water Osmoreceptors: Cells that are sensitive to osmotic pressure ○ Located in hypothalamus - the part of the brain that regulates hunger, thirst, blood pressure, body temperature, fluid balance, and salt balance Regulating Reabsorption of Water If blood plasma becomes too concentrated → osmotic pressure increases ○ Osmoreceptors in the hypothalamus send impulses to pituitary gland in brain that causes release of ADH ADH travels through the blood to the kidneys, where it increases permeability of distal tubule and collecting duct, allowing more water to be reabsorbed ○ Dilutes blood and lowers osmotic pressure to normal Regulating Reabsorption of Water If blood plasma is too dilute → osmotic pressure decreases ○ Osmotic receptors stop/prevent release of ADH ○ Distal tubule and collecting duct becomes less permeable to water ○ Allows more water to be excreted with urine Diabetes Diabetes is a disease in which your body either can't produce insulin or can't properly use the insulin it produces Insulin is a hormone produced by your pancreas to regulate the amount of glucose (sugar) in the blood 3 types of diabetes: ○ Diabetes mellitus ○ Diabetes insipidus ○ Gestational diabetes: Develops in pregnant women who have never had diabetes before Diabetes Mellitus Diabetes mellitus is caused by inadequate secretion of insulin from cells in the pancreas ○ This affects the function of the kidneys, as insulin is required for cells to absorb glucose from the bloodstream Without insulin, blood glucose levels remain higher than necessary, causing much of this glucose to be excreted in the urine (smells sweet) Water is unable to be reabsorbed into the bloodstream from the nephron (disrupts passive transport of H2O). ○ As a result, large amounts of water are lost, explaining why individuals with this form of diabetes are often thirsty Diabetes Insipidus Diabetes insipidus: Results from a defect antidiuretic hormone (ADH), which regulates water reabsorption in the nephron Without ADH, the nephron becomes less permeable to water, and less H2O is removed from the filtrate As a result, individuals with diabetes insipidus also produce large volumes of urine (however, their urine does not contain high concentrations of glucose) ○ Will experience intense thirst because water is excreted quicker than it can be consumed ○ Leads to severe dehydration and ion imbalances ○ Treatment: Synthetic ADH to restore water and ion balance Diuretic Diuretic: A substance that increases volume of urine ○ Stimulates urine production by decreasing ADH release which decreases permeability of tubules and collecting ducts Increases water loss to urine, leads to dehydration Ex. Alcohol, coffee, tea, carbonated drinks Reabsorption of Salts Kidneys regulate salt balance in blood by controlling excretion and reabsorption of ions When blood Na+ concentration drops, a hormone called aldosterone stimulates distal tubules and collecting ducts to reabsorb Na + ○ Cl- ions follow Na+ by charge attraction ○ Water follows by osmosis ○ Net effect of retaining both salt and water Aldosterone also stimulates secretion of K+ ions into distal tubules and collecting ducts if K+ concentration in blood is too high Balance of Excretory System Often, the balance of materials in out urine depends on a number of factors However, diet, physical activity, stress, and fatigue can affect levels of materials in urine Many factors must be taken into account by healthcare professionals when they analyze urine to look for indicators of disease (Ex. diabetes) Urinary Tract Infection (UTI) Cystitis: Bladder is affected by a bacterial/viral infection Urethritis: Only urethra is involved UTIs are more common in women than men, based on anatomical differences Can result in permanent damage to kidneys Urinary Tract Infection (UTI) Symptoms: Painful, burning sensation during urination Need to urinate frequently, even if no urine is present Bloody/brown urine Tenderness, chills, fever, nausea, voming Urinary Tract Infection (UTI) Treatment: Antibiotics Surgery (in serious cases) Preventative measures include maintaining hygiene and personal behaviors. Kidney Stones Kidney stones: Crystalline formations due to excess calcium in urine Treatment: ○ Medication can be used to break down formations ○ Ultrasound shock waves can be used on stones less than 20 mm (2 cm) in diameter ○ Surgery may be needed for larger stones Problems with Kidney Function Renal insufficiency: State in which kidneys can’t maintain homeostasis due to damage to their nephrons Causes of nephron damage: ○ Kidney infection ○ High blood pressure ○ Trauma (injury to kidney) ○ Poisoning ○ Atherosclerosis (causes high blood pressure) ○ Blockage of tubules (nephrons) If 75% or more nephrons are destroyed, urine output is inadequate to maintain homeostasis ○ Requires kidney transplant/artificial kidney that performs dialysis (blood cleansing process) Dialysis Diffusion of dissolved substances through a semipermeable membrane ○ Substance moves across membrane from high → low concentration ○ Substances more concentrated in blood diffuse into dialysis solution, called dialysate ○ Substances more concentrated in dialysate diffuse into blood Two main types of renal dialysis: ○ Hemodialysis ○ Peritoneal dialysis Hemodialysis Utilizes an artificial membrane in an external device (artificial kidney), connected to an artery and a vein in person’s arm ○ Solution contains same ingredients as clean blood plasma ○ Patient’s blood (known as dialysate) is passed through this tube and wastes diffuse into surrounding solution ○ Dialysis treatments take between 2-5 hours, may be repeated 3x a week ○ Patients must have a strictly regulated diet to prevent excess levels of toxins to build in their systems Peritoneal Dialysis Uses lining of intestines (peritoneum) as dialysis membrane Is introduced into abdominal cavity, where large surface area and rich supply of capillaries slowly filter blood Kidney Transplants One permanent solution to dialysis is to replace damaged kidney with a fully functional one Often involves a close family member donating one of their kidneys to the patient Result: Both donor and recipient will have one fully functional kidney However, because both only have one kidney, they should closely monitor their diet in the future Kidneys can also be obtained from cadaver as long as organ donation card has been filled out Kidney-Coronary Connection Kidneys can fail due to high blood pressure (BP) If blood vessels in kidneys are damaged due to high BP, they lose the ability to filter wastes effectively Unfortunately, symptoms of high BP and kidney impairment don't appear until damage has already been done