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urinary system

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urinary system

  1. 1. BIOLOGY URINARY SYSTEM Block 4, Case 1, G5, PBL
  2. 2. Objectives ● What is Urinary System ● Organs: kidney, ureters, urinary bladder and urethra ● Anatomy of kidney ● Definition of nephron ● Structure of Nephron ● The process of filtration ● Relationship of urinary with other systems ● Diseases of urinary system
  3. 3. The Urinary System The urinary system is the organ system of the body that plays a major role in maintaining the salt, water, and pH homeostasis of the blood. It include: pair of kidney and ureters and a urinary bladder. Collectively, these organs carry out the process of excretion, or the removal of metabolic waste from the body. These metabolic waste materials are the by -products of the normal activities of the cells and tissues.
  4. 4. Function of the Urinary System A) Maintenance of Water–Salt Balance A principal function of the kidneys is to maintain the appropriate water–salt balance of the blood. B) Maintenance of Acid–Base Balance. The kidneys regulate the acid–base balance of the blood. For a person to remain healthy, the blood pH should be just about 7.4. The kidneys monitor and help control blood pH C) Secretion of Hormones The kidneys assist the endocrine system in hormone secretion. The kidneys release renin, an enzyme that leads to aldosterone secretion d) Excretion of Metabolic Wastes The kidneys excrete metabolic wastes, notably nitrogenou wastes. Urea is the primary nitrogenous end product of metabolism in human beings
  5. 5. Kidney histology Two bean shaped kidneys are attached to the posterior abdominal wall, one on each side of the vertebral column. The kidneys have a tough fibrous capsule (irregular dense connective tissue) for protection. Otherwise they have very little connective tissue between the nephrons. The kidney has a granular cortex (outer region). It has this appearance because it is full of ovoid filtration units. And a medulla (inner region) which has a more striated appearance.The kidney is organised into many lobes, organised in a pyramidal structure, where the outer portion is made up of cortex, and the inner portion is made up of the medulla.
  6. 6. Ureters Ureter:is a tube that carries urine from the kidney to the urinary bladder. *There are two ureters.The upper half of the ureter is located in the abdomen and the lower half is located in the pelvic area. *The ureter is about 25 cm long in the average adult. *The tube has thick walls composed of a fibrous, a muscular, and a mucus coat, which are able to contract.
  7. 7. Histology The wall of the ureter have 3 layers: 1- The outer layer: the fibrous coat. 2 - The middle layer: the muscular coat./ The main function of this layer is peristalsis to ……..push the urine. 3 - The inner layer (the mucosa): is transitional epithelium./This layer secretes mucus which ……. coats and protects the surface of the cells. * smooth muscle layers in the walls contract to propel urine into the bladder. * once urine has entered the bladder, it is prevented from flowing back into the ureters by small valve.
  8. 8. The Urinary Bladder ● The urinary bladder stores urine until it is expelled from the body. ● The bladder has three openings: two for the ureters and one for the urethra. ● The bladder wall is expandable. ● It is lined with mucosa of transitional epithelium.
  9. 9. ● The muscularis layer of the urinary bladder has 3 layers of smooth muscle .
  10. 10. Kidney anatomy ● Renal Capsule – outer membrane that surrounds the kidney; it is thin but tough and fibrous ● Renal Pelvis – basin-like area that collects urine from the nephrons, it narrows into the upper end of the ureter ● Calyx – extension of the renal pelvis; they channel urine from the pyramids to the renal pelvis ● Cortex – the outer region of the kidney; extensions of the cortical tissue, contains about one million blood filtering nephrons ● Nephron – these are the filtration units in the kidneys
  11. 11. ● Medulla – inner region of the kidney contains 8-12 renal pyramids. The pyramids empty into the calyx. ● Medullary pyramids – formed by the collecting ducts, inner part of the kidney ● Ureter – collects filtrate and urine from renal pelvis and takes it to the bladder for urination ● Renal Artery – branches off of the aorta bringing waste-filled blood into the kidney for filtering in the nephrons; the renal artery is further subdivided into several branches inside the kidney. Each minute, the kidneys receive 20% of the blood pumped by the heart. Some arteries nourish the kidney cells themselves. ● Renal Vein – removes the filtered blood from the kidneys to the inferior vena cava
  12. 12. Anatomy of Kidney
  13. 13. Nephron The nephron is the main functional unit of the kidney which is responsible for filtering the blood and concentrating the solution to produce urine. ● Types of Nephron : 1-Cortical nephron: Located entirely in the cortex and includes most nephrons. 2-Juxtamedullary nephron:Found at the margin of the cortex and medulla.
  14. 14. Nephron There are two parts of a kidney nephron: the renal corpuscle, and the renal tubule. (1) Renal Corpuscle: Each renal corpuscle consists of : 1- glomerulus: is a knot of capillaries 2-the glomerular capsule or Bowman’s capsule: a cup shaped hollow structure that completely surrounds the glomerulus like a well-worn baseball glove encloses a ball. Glomerular filtration: Water and solutes smaller than proteins are forced through the capillary walls and pores of the glomerular capsule into the renal tubule.
  15. 15. Nephron (2) Renal Tubule They are the : ● proximal convoluted tubule (PCT)-nearest the glomerulus; have permeable cell membranes that reabsorb glucose, amino acids, metabolites. ● The distal convoluted tubule (DCT) – farthest from the glomerulus; helps regular potassium excretion.
  16. 16. The collecting ducts: Each of which receives urine from many nephrons, They deliver the final urine product into the calyces and renal pelvis. The nephron loop, or loop of Henle Has an ascending and descending limb, these loops along with their blood vessels and collecting tubes form the pyramids in the medulla.
  17. 17. The Process of Filtration. The kidneys filter unwanted substances from the blood and produce urine to excrete them. There are three main steps of urine formation: ● Glomerular filtration, ● Reabsorption, ● Secretion.
  18. 18. Glomerular filtration ● Glomerular filtration is the process by which the kidneys filter the blood, removing excess wastes and fluids. ● Blood enters the kidney via the renal artery.It forms many afferent arterioles, each of which delivers blood to an individual kidney nephron.each consist of microscopic filter called glomerulus. ● The pressure of the blood inside the glomerulus is increased due to the difference in diameter of the incoming and out-going arterioles ● The diameter of the afferent arteriole is greater than the diameter of the efferent arteriole.
  19. 19. ● This increased blood pressure helps to force water,salts,glucose and urea from the blood out of the glomerular capillaries. ● The components of blood are filtered based on their particle size. ● The water and salts forced out of the glomerular capillaries pass into the Bowman's Capsule and are called the glomerular filtrate. ● The glomerular filtrate then passes from the renal corpuscle to the renal tubule.
  20. 20. Reabsorption Occurring more commonly within the nephron system than filtration, this is a form of active transport which takes the useful substances for the body from the tubules and places them back into the blood filled capillaries. Within the PROXIMAL CONVOLUTED TUBULE reabsorption occurs when pH needs to be maintained and bicarbonate ions are reabsorbed back into the bloodstream. Glucose, Amino Acids and Potassium Ions are all beneficial for the body so they are actively transported into the blood as well. Sodium and Chlorine Ions are also moved back into the capillaries so that some salt regulation can occur. On the other end of the scale, substances such as hydrogen ions and toxins are actively secreted from the blood into the tubule.
  21. 21. Reabsorption Within the LOOP OF HENLE, the descending limb allows for the reabsorption of water through osmosis whereas the ascending limb allows for the passive and active transport of salts such as sodium to move out of the tubules and be reabsorbed. The DISTAL CONVOLUTED TUBULE is where the final adjustments are made to the passing urine within the tubule systems. This is where highly selective reabsorption takes place allowing for small adjustments to be made especially between the presence of Potassium and Sodium.
  22. 22. Secretion The third process by which the kidneys clean blood (regulating its composition and volume) is called tubular secretion and involves substances being added to the tubular fluid. This removes excessive quantities of certain dissolved substances from the body, and also maintains the blood at a normal healthy pH (which is typically in the range pH 7.35 to pH 7.45). The substances that are secreted into the tubular fluid (for removal from the body) include: ● Potassium ions (K+ ), ● Hydrogen ions (H+ ), ● Ammonium ions (NH4 + ), ● creatinine, ● urea, ● some hormones, and ● some drugs (e.g. penicillin).
  23. 23. Tubular secretion occurs from the epithelial cells that line the renal tubules and collecting ducts. It is the tubular secretion of H+ and NH4 + from the blood into the tubular fluid (i.e. urine - which is then excreted from the body via the ureter, bladder, and urethra) that helps to keep blood pH at its normal level. The movement of these ions also helps to conserve sodium bicarbonate (NaHCO3 ). The typical pH of urine is about 6. Urine formed via the three processes outlined above trickles into the kidney pelvis. At this final stage it is only approx. 1% of the originally filtered volume but includes high concentrations of urea and creatinine, and variable concentrations of ions. The typical volume of urine produced by an average adult is around 1.5 - 2.0 dm3 per day.
  24. 24. Relationship between urinary system and other systems Nervous System: ◄ Kidneys dispose of nitrogenous wastes;maintain fluid,electrolyte, and acid-base balance of blood; renal regulation of Na+, K+, and Ca2+ content in ECF essential for normal neural function ◄ Neural controls involved in micturition;sympathetic nervous system activity triggers the renin-angiotensin mechanism Endocrine System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood; produce the hormone erythropoietin; renal regulation of Na+ and water balance essential for blood pressure homeostasis and hormone transport in the blood ◄ ADH, aldosterone, ANP, and other hormones help regulate renal reabsorption of water and electrolytes
  25. 25. Relationship between urinary system and other systems Respiratory System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood ◄ Respiratory system provides oxygen required by kidney cells; disposes of carbon dioxide; cells in the lungs convert angiotensin I to angiotensin II Lymphatic System/Immunity ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood ◄ By returning leaked plasma fluid to cardiovascular system, lymphatic vessels help maintain normal systemic blood pressure needed for kidney function; immune cells protect urinary organs from infection, cancer,and other foreign substances
  26. 26. Relationship between urinary system and other systems Cardiovascular System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood; renal regulation of Na+ and water balance essential for blood pressure homeostasis. Na+, K+, and Ca2+ regulation help maintain normal heart function ◄ Systemic arterial blood pressure is the driving force for glomerular filtration; heart secretes atrial natriuretic peptide; blood vessels transport nutrients, oxygen, etc. to urinary organs Digestive System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood; also, metabolize vitamin D to the active form needed for calcium absorption ◄ Digestive organs provide nutrients needed for kidney cell health; liver synthesizes most urea, a nitrogenous waste that must be excreted by the kidneys Reproductive System • Kidneys dispose of nitrogenous wastes ;maintain fluid, electrolyte, and acid-base balance of blood
  27. 27. Relationship between urinary system and other systems Muscular System ◄ Muscles of pelvic diaphragm and external urethral sphincter function in voluntary control of micturition; creatinine is a nitrogenous waste product of muscle metabolism that must be excreted by the kidneys Integumentary System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood ◄ Skin provides external protective barrier; serves as site for vitamin D synthesis and water loss (via perspiration) Skeletal System ◄ Kidneys dispose of nitrogenous wastes; maintain fluid, electrolyte, and acid-base balance of blood ◄ Bones of rib cage provide some protection to kidneys
  28. 28. Urinary Tract Infections (UTI) ● The UTIs occur mainly in women and affect the bladder and urethra. A woman has a shorter urethra than a man does, which shortens the distance that bacteria must travel to reach the bladder. ● Infection of the bladder is cystitis. Escherichia coli by far is the most common pathogen of UTIs. Most common symptoms include dysuria, frequent urination, hematuria and lower abdominal pain. ● Infection of the urethra is urethritis. Because the female urethra is close to the vagina, sexually transmitted infections, such as herpes, gonorrhea, chlamydia and mycoplasma, can cause urethritis. The main symptom of urethritis is dysuria.
  29. 29. ● The infection of kidneys is called pyelonephritis. The causative agents of pyelonephritis are similar to those of cystitis, with E.coli accounting for more than 75% of the infections. Catheterization can also cause pyelonephritis. Symptoms of pyelonephritis are lower back or abdominal pain, fever, sweat, headache, vomiting and malaise and often include symptoms of cystitis.
  30. 30. Benign Prostatic Hyperplasia ➔ It is the enlargement of the prostate gland ➔ The prostate gland surrounds the urethra, the tube that carries urine from the bladder out of the body. As the prostate gets bigger, it may squeeze or partly block the urethra. This often causes problems with urinating. ➔ As prostate compresses the urethra the bladder cannot force itself to empty completely. ➔ The prostate gland continues to grown throughout a man’s life. Hence BPH is common in aging men. Up to 90% of men over age 80 have BPH. ➔ Its symptoms include: ◆ Nocturia ◆ Frequent urination ◆ Urinary retention (Also known as Benign prostatic Hypertrophy)
  31. 31. References : Books: ◆ Essentials of Human Anatomy Physiology - Marieb, Elaine N. chapter 16 page534. , 516 . ◆ Human biology Mader/Windelspecht 14 edition ,chapter 11 , page 218 ◆ Essentials of Human Anatomy Physiology - Marieb, Elaine N. chapter 15 page520 .
  32. 32. References : Wibesites: ● http://www.healthhype.com/nephron-glomerulus-and-tubule-structure-diag ram-functions.html

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