Excretory System

• Excretion - removal of metabolic wastes from the body
• Excretion is different from defecation
• The waste in defecation are mostly undigested materials and bacteria that were not previously present in your body cells
• The skin, lungs, liver, and kidneys remove metabolic wastes
• Excretory System: Major Organs and Structures:

  • kidneys, ureters, urinary bladder, urethra
• Excretory System: Accessory Structures

  • lungs
  • skin
  • liver
• Excretory System: Functions

  • removal of metabolic wastes
  • fluid and electrolyte balance
  • acid-base balance
  • blood pressure regulation
• Organs of Excretory System: Skin

  • removes salt, lactic acid, and urea through sweat
• Organs of Excretory System: Lungs

  • removes carbon dioxide with every humidified and expired breath
• Organs of Excretory System: Liver

  • removes bilirubin by putting it in a bile
• Organs of Excretory System: Kidney

  • removes nitrogenous wastes, excess minerals, bilirubin and excess hydrogen ions by producing urine
• Nitrogenous Wastes - can be lethal to the body if these accumulate in the blood in excess amount
• Nitrogenous Wastes: Ammonia

  • produced from the breakdown of amino acids
  • extremely toxic which is why it is converted by the liver to urea, a less toxic waste
• Nitrogenous Wastes: Urea

  • most common nitrogenous waste
  • 50% of nitrogenous waste
  • formed from the breakdown of proteins
• Nitrogenous Wastes: Uric acid

  • formed from the breakdown of nucleic acids
• Nitrogenous Wastes: Creatinine

  • formed from the breakdown of creatine phosphate which is stable energy storage molecule
• Role of Kidney

  • excretion
  • blood volume control
  • ion concentration regulation
  • pH regulation
  • RBC concentration
  • vitamin D synthesis
• Kidneys Function in multiple systems

  • Skeletal System and Integumentary System = Vitamin D Synthesis
  • Cardiovascular and Endocrine System = Renin and Erythropoietin
  • Excretory System = Elimination of wastes
• Components of Urinary System

  • 2 kidneys
  • 2 ureters
  • 1 urinary bladder
  • 1 urethra
• Kidney Anatomy

  • Dark red, bean-shaped organs about the size of a tightly clenched fist
  • Weighs 5 ounce
  • Located in the abdomen
  • Not surrounded by peritoneum - retroperitoneal
  • Extend between the 11th thoracic and 3rd lumbar vertebrae on each side of the vertebral column and are somewhat protected superiorly by the ribs
  • the right kidney is slight lower than the left due to the position of the liver
• Kidney Anatomy: Renal Capsule

  • acts as a barrier to protect the kidney
  • fibrous
• Kidney Anatomy: Perirenal fat capsule

  • adipose tissue
  • protects the kidney
  • absorbs the mechanical shock to the kidney that may occur with a fall
• Kidney Anatomy: Renal fascia

  • anchors kidney to posterior muscle wall of the body's abdomen
  • connective tissue covering
• 3 Layers of the Kidney

  • Renal Capsule
  • Renal Cortex
  • Renal Medulla
• Kidney Anatomy: Renal Hilum

  • notch in a kidney
  • all structures entering or leaving the kidney do so at the hilum
• Kidney Anatomy: Renal artery, renal vein, renal pelvis

  • renal artery enters the kidney, while the renal vein and renal pelvis (leading to the ureter) exit the kidney
• Kidney Anatomy: Renal Sinus

  • space left if the renal artery, renal vein, and renal pelvis will be removed
• Kidney Anatomy: Renal Pyramids

  • 3D cones, each leading to a funnel-like structure called minor calyx
• Kidney Anatomy: Calyces

  • two or more minor calyces may merge to form a major calyx
• Anatomy of Nephron

  • functional unit of kidneys
  • microscopic
  • each kidney contains over 1 million nephrons
  • produce urine
• Anatomy of Nephron: Two basic parts

  • renal corpuscle
  • renal tubule
• Anatomy of Nephron: Renal Corpuscle

  • elaborate filter in a cup
  • composed of the glomerulus and glomerular capsule (Bowman's capsule)
  • afferent arteriole delivers blood to the glomerulus inside the glomerular capsule
• Anatomy of Nephron: Glomerulus

  • capillary bed
  • the filter
• Anatomy of Nephron: Glomerular capsule

  • aka Bowman's capsule
  • walls of the cup
• Anatomy of Nephron: Renal tubule

  • composed of the proximal convoluted tubule (PCT), the nephron loop (loop of Henle), and the distal convoluted tubule (DCT)
  • simply a hollow tube
• Anatomy of Nephron: Proximal convoluted tubule

  • responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins
• Anatomy of Nephron: Nephron loop

  • aka loop of Henle
  • plays a role in reabsorbing water and sodium chloride from the filtrate
• Anatomy of Nephron: Distal convoluted tubule

  • a short nephron segment
  • interposed between the macula densa and collecting dust
  • it is short
  • plays a key role in regulating extracellular fluid volume and electrolyte homeostasis
• The renal corpuscle and convoluted tubules are located in the renal cortex.
• The nephron loop and collecting duct are located in the pyramid.