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Urinary system

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محمد زكي

The urinary system functions to maintain homeostasis by filtering the blood and regulating fluid balance, electrolyte and acid-base levels. The kidneys filter around 180 liters of plasma per day to form urine through glomerular filtration, tubular reabsorption and secretion. Urine is stored in the bladder and emptied through the urethra in a process called micturition which is controlled by the brain and spinal cord.

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Urinary system Dr. mohamed saki
Urinary system: physiology • The major work of the urinary system is done by the nephrons. • The other parts are primarily passageways and storage areas. • The eliminated materials are collectively collected urine.
Functions of the urinary system The primary function of the kidneys is to maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism.
Functions of the urinary system six important roles of the kidneys are 1. Regulation of plasma osmolarity. 2. Regulation of plasma volume 3. Regulation of plasma hydrogen ion concentration (pH). 4. Removal of metabolic waste products and foreign substances from the plasma 5. Secretion of Hormones 6. Regulation of plasma ionic composition
Formation of Urine • Urine is formed in three steps: – Filtration – Reabsorption, and – Secretion.
Urine formation Glomerular Filtration • Blood enters the afferent arteriole and flows into the glomerulus. • Blood in the glomerulus has both: – Filterable – Non-filterable blood components Filterable blood components move toward the inside of the glomerulus while non-filterable blood components bypass the filtration process by exiting through the efferent arteriole.
Filtration cont…. filterable blood components are •water • nitrogenous waste •nutrients and •salts (ions) Nonfilterable blood components include formed elements such as •blood cells and platelets along with plasma proteins.
Volume of blood filtered • Kidneys are 1% of body weight and use 20-25% of the oxygen. • ¼ of the cardiac output is delivered to the kidneys each minute • 1000 to 1200ml of blood go through each glumeruli of each nephron every minute. – Equals 650 ml of plasma (blood cells cannot be filtered)
Volume of blood filtered cont… • 1/5 of this goes through the renal tubules. • The entire plasma volume is filtered 60X a day or 180 liters of water per day. – Normal urine output = 0.5ml/kg body weight/hr – 30 to 40 ml per hour for an adult Not all of the filtered material is excreted
• The volume and concentration of urine is controlled by: – Antidiuretic hormone – Aldestrone – The Renin – angiotensin mechanism
Urine formation: Tubular Reabsorption • Glomerular filtrate  proximal convoluted tubule • Molecules and ions are reabsorbed back into the blood. – Peritubular capillary network – This reabsorption process allows water (H2O) to pass from the glomerular filtrate back into the circulatory system
Urine formation: Reabsorption • Glucose and various amino acids also are reabsorbed into the circulatory system. • Carrier molecules
Urine formation: Tubular Secretion • Some substances are removed from blood through the peritubular capillary network into the distal convoluted tubule or collecting duct. • These substances are – Hydrogen ions – creatinine and – drugs
Tubular Secretion cont… • Urine is a collection of substances that have not been re-absorbed during glomerular filtration or tubular re- absorbtion.
• Urine flows into the ureter, that connects each kidney to the bladder. – Is facilitated by peristaltic waves from contraction of the smooth muscle in the ureter wall. Bladder: – Adult bladder capacity is about 300 to 600 ml – Functions as a muscular sac that allow storage of urine until voiding is convenient.
Urethra • The urethra is a muscular tube that drains urine from the body. • Female – 3-4 cm long • Male – 20 cm long
Micturition • Micturition: – Is the process by which the urinary bladder empties when it becomes filled. • This involves two main steps: 1. The bladder fills progressively until the tension in its walls rises above a threshold level. 2. a nervous reflex called the micturition reflex that empties the bladder.
Facilitation or Inhibition of Micturition by the Brain • The micturition reflex is a completely autonomic spinal cord reflex, but it can be inhibited or facilitated by centers in the brain. – strong facilitative and inhibitory centers in the brain stem, located mainly in the pons, and – Several centers located in the cerebral cortex that are mainly inhibitory but can become excitatory

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Urinary system

  • 2. Urinary system: physiology • The major work of the urinary system is done by the nephrons. • The other parts are primarily passageways and storage areas. • The eliminated materials are collectively collected urine.
  • 3. Functions of the urinary system The primary function of the kidneys is to maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism.
  • 4. Functions of the urinary system six important roles of the kidneys are 1. Regulation of plasma osmolarity. 2. Regulation of plasma volume 3. Regulation of plasma hydrogen ion concentration (pH). 4. Removal of metabolic waste products and foreign substances from the plasma 5. Secretion of Hormones 6. Regulation of plasma ionic composition
  • 5. Formation of Urine • Urine is formed in three steps: – Filtration – Reabsorption, and – Secretion.
  • 6. Urine formation Glomerular Filtration • Blood enters the afferent arteriole and flows into the glomerulus. • Blood in the glomerulus has both: – Filterable – Non-filterable blood components Filterable blood components move toward the inside of the glomerulus while non-filterable blood components bypass the filtration process by exiting through the efferent arteriole.
  • 7. Filtration cont…. filterable blood components are •water • nitrogenous waste •nutrients and •salts (ions) Nonfilterable blood components include formed elements such as •blood cells and platelets along with plasma proteins.
  • 8. Volume of blood filtered • Kidneys are 1% of body weight and use 20-25% of the oxygen. • ¼ of the cardiac output is delivered to the kidneys each minute • 1000 to 1200ml of blood go through each glumeruli of each nephron every minute. – Equals 650 ml of plasma (blood cells cannot be filtered)
  • 9. Volume of blood filtered cont… • 1/5 of this goes through the renal tubules. • The entire plasma volume is filtered 60X a day or 180 liters of water per day. – Normal urine output = 0.5ml/kg body weight/hr – 30 to 40 ml per hour for an adult Not all of the filtered material is excreted
  • 10. • The volume and concentration of urine is controlled by: – Antidiuretic hormone – Aldestrone – The Renin – angiotensin mechanism
  • 11. Urine formation: Tubular Reabsorption • Glomerular filtrate  proximal convoluted tubule • Molecules and ions are reabsorbed back into the blood. – Peritubular capillary network – This reabsorption process allows water (H2O) to pass from the glomerular filtrate back into the circulatory system
  • 12. Urine formation: Reabsorption • Glucose and various amino acids also are reabsorbed into the circulatory system. • Carrier molecules
  • 13. Urine formation: Tubular Secretion • Some substances are removed from blood through the peritubular capillary network into the distal convoluted tubule or collecting duct. • These substances are – Hydrogen ions – creatinine and – drugs
  • 14. Tubular Secretion cont… • Urine is a collection of substances that have not been re-absorbed during glomerular filtration or tubular re- absorbtion.
  • 15. • Urine flows into the ureter, that connects each kidney to the bladder. – Is facilitated by peristaltic waves from contraction of the smooth muscle in the ureter wall. Bladder: – Adult bladder capacity is about 300 to 600 ml – Functions as a muscular sac that allow storage of urine until voiding is convenient.
  • 16. Urethra • The urethra is a muscular tube that drains urine from the body. • Female – 3-4 cm long • Male – 20 cm long
  • 17. Micturition • Micturition: – Is the process by which the urinary bladder empties when it becomes filled. • This involves two main steps: 1. The bladder fills progressively until the tension in its walls rises above a threshold level. 2. a nervous reflex called the micturition reflex that empties the bladder.
  • 18. Facilitation or Inhibition of Micturition by the Brain • The micturition reflex is a completely autonomic spinal cord reflex, but it can be inhibited or facilitated by centers in the brain. – strong facilitative and inhibitory centers in the brain stem, located mainly in the pons, and – Several centers located in the cerebral cortex that are mainly inhibitory but can become excitatory