Copy of Chapter 9 Excretion

Page 2: Main function of the Excretory system

  • The main function of the Excretory system is to regulate the volume and composition of body fluids

  • Removes wastes and returns needed substances back to the body for reuse

  • Examples of wastes include CO2, water / Na+ and Cl-, H+ ions / and ammonia

Page 3: Biological Wastes

  • Biological Wastes: anything that there is more of than the body needs

Page 4: Excretion

  • The process of separating wastes from the body fluids and eliminating them

Page 5: Excretory System Anatomy

  • The organs of the excretory system

    • include two kidneys,

    • two ureters

    • the urinary bladder

    • and the urethra

  • The renal artery and renal vein are part of the circulatory system but are intimately connected with the excretory system

  • The word "renal" comes from the Latin

Page 6: Excretion Of Urine

  • Urine travels from renal tubule to renal pelvis to ureters that connects to bladder

  • Urine is stored in the bladder and exits the body through the urethra

Page 7: Kidneys

  • Functions of the kidneys:

    • filter the blood

    • remove metabolic wastes

    • return water and nutrients back to the blood

    • form urine for excretion

Page 9: Renal Circulation

  • Renal circulation: unfiltered blood enters the kidney through the renal artery and filtered blood exits through the renal vein

Page 10: Kidney Anatomy

  • Kidney anatomy:

    • renal medulla: inner layer of the kidney

      • regulates salt/water balance of blood

    • renal cortex: Outer layer of the kidney

      • site of filtration of wastes from blood

    • nephrons: Filters blood inside the kidneys

    • renal pelvis: Funnels urine to the ureter

    • ureter: takes urine from the kidney to the bladder

Page 11: Nephrons

  • The nephron filters blood in the kidney.

  • It has three parts:

    • proximal tubule,

    • Bowman's capsule,

    • and distal tubule.

  • Filtration happens in the nephron, where plasma and particles go into Bowman's capsule. The renal tubule reabsorbs water, nutrients, and salts.

Page 13:

  • Overview of the nephron and its three functional regions: proximal tubule, Bowman's capsule, distal tubule

  • Proximal tubule is located near the Bowman's capsule, distal tubule is located more distantly

Page 16: Urine (pee)

  • Urine is formed from filtrate from the nephron

  • Composition of urine: 95% water, neutral pH, urea, salts, other organic compounds

  • Urine should not contain glucose and should be normally sterile

Page 19: Glomerular Filtration

  • Glomerular filtration forces water and dissolved substances from blood plasma into Bowman's capsule

  • 2 Factors contribute to filtration:

    • Permeability: Capillaries in glomerulus have many pores to allow passage of many materials – except proteins and blood cells •

    • Blood Pressure: about 4x greater in these capillaries compared to other body areas

  • Permeability and blood pressure contribute to filtration

Page 22:

  • Nephron structures: Bowman's capsule, renal tubule (proximal tubule, loop of Henle, distal tubule)

  • Filtrate is filtered out of the blood in the Bowman's capsule and carried through the renal tubule

Page 24:

  • Proximal tubule reabsorption: substances are reabsorbed back into the blood

  • About 65% of the filtrate that passes through the proximal tubule is reabsorbed and returned to the body

  • Active transport and passive transport mechanisms are involved in reabsorption

    • (Active) Pump Na+ ions, glucose, other solutes back into blood

    • (Passive) Negatively charged ions follow / Water through osmosis

Page 26: Loop of Henle reabsorption

  • Loop of Henle reabsorption

    • Function: reabsorb water and ions from filtrate

    • Kidney’s becomes saltier as it moves deeper into the medulla

    • Water diffuses from the filtrate to capillaries as it moves down the descending limb

    • Maximum concentration of sodium ions at the bottom of the loop

  • Changes in permeability in the ascending limb of the loop of Henle

    • Now impermeable to water and slightly permeable to solutes

    • Sodium ions move out of the filtrate into the blood through diffusion and active transport

    • Maintains the saltiness of the medulla

Page 29: Distal Tubule Reabsorption and Secretion

  • Distal tubule reabsorption and secretion

    • Reabsorption: depends on the needs of the body (sodium ions) or occurs by electrical attraction (chloride ions)

      • Water is reabsorbed by osmosis, decreasing the concentration of the filtrate

    • Secretion: of potassium and hydrogen ions into the distal tubule helps maintain salt and pH balance

      • Some drugs, like penicillin, are also secreted into the distal tubule

Page 30: Distal Tubule Reabsorption and Secretion

  • Reabsorption from the collecting duct

    • Filtrate in the collecting duct still contains a lot of water

    • Increased permeability to water in the distal tubule if the body is dehydrated, leading to more water reabsorption

    • Controlled by hormones like ADH (anti-diuretic hormone)

    • Final reabsorption of water concentrates the filtrate, now called urine

Page 31:

  • Steps in the formation of urine

Page 34: The amount of water reabsorbed from filtrate influences

  • 2 important characteristics of blood:

    • Amount of water reabsorbed influences blood volume and blood pressure

    • Concentration of plasma solutes remains constant in the blood

Page 37: Regulating Reabsorption of Water

  • Regulation of water reabsorption by osmoreceptors

    • Osmoreceptors sense increased osmotic pressure and release ADH (anti-diuretic hormone) to increase water reabsorption

    • ADH (vasopressin) - Increases the amount of water that is reabsorbed by the kidneys

Page 39: Antidiuretic Hormone (ADH)

  • Antidiuretic Hormone (ADH)

    • Release of ADH is stopped if blood is too dilute

    • Distal tubule and collecting duct become less permeable to water

    • Volume of urine increases

    • Disorder: Diabetes insipidus, low or no secretion of ADH, leading to excessive water loss

Page 40: Reabsorption of Salts (aldosterone)

  • Reabsorption of salts (aldosterone)

    • Salt balance controlled by excretion and reabsorption of ions (Na+, K+)

    • Aldosterone stimulates reabsorption of Na+ ions, followed by Cl- and water

    • Stimulates secretion of K+ into tubules if blood K+ concentration is too high

Page 41: Regulating Blood pH

  • Regulation of blood pH by the excretory system

    • Acid-base buffers in blood can add or remove excess H+ ions

    • Changes in breathing rate generate more CO2, making the blood more acidic

    • Kidneys excrete excess H+ ions if needed and can excrete or conserve excess bicarbonate (HCO3-)

Page 42: Urinary Tract Infections

  • Urinary tract infections

    • Bladder or kidney infection caused by virus or bacteria, mainly E. coli

    • Treated with antibiotics

    • Symptoms include pain when urinating, frequent urination, bloody urine, back pain, and nausea

    • Can lead to permanent kidney damage if untreated

Page 43: Kidney Stones

  • Kidney stones

    • Small kidney stones made from calcium and uric acid can pass through urine

    • Caused by repeated infections, insufficient water consumption, inactivity, and acidic urine

    • Treatment includes breaking up small crystals with ultrasonic shock waves or surgical removal of large crystals

Page 44: Kidney Failure & Dialysis

  • High blood pressure, reduced blood flow, diabetes, or poisoning can cause damage to nephrons

  • Nephrons can regenerate but may become permanently damaged over time

  • Dialysis: a temporary solution using an external artificial kidney or peritoneal dialysis using the lining of the intestines

  • Kidney transplant is considered a cure for kidney failure, while dialysis is not

Page 45:

  • Dialysis

    • Diffusion of dissolved substances through a semi-permeable membrane

    • Hemodialysis uses an artificial kidney outside the body

    • Peritoneal dialysis uses the lining of the intestines as the membrane

    • Kidney transplants may be necessary

Page 48:

  • What you need to know about water balance, salt balance,