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Urinary System and Excretion

Urinary System and Excretion. Bio105 Lecture Packet 20 Chapter 16. Outline – Urinary System. Function Organs of the urinary system Kidneys Function Structure Disorders of the urinary system. Urinary System.

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Urinary System and Excretion

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  1. Urinary System and Excretion Bio105 Lecture Packet 20 Chapter 16

  2. Outline – Urinary System • Function • Organs of the urinary system • Kidneys • Function • Structure • Disorders of the urinary system

  3. Urinary System • The digestive system eliminated waste from the digestive tract. But we also need a way to eliminate waste from the rest of the body. • Function of urinary system is: Excretion of metabolic wastes and to maintain homeostasis of blood.

  4. Which of the following system does not function to excrete waste? • Digestive • Urinary • Integumentary • Circulatory

  5. Urine • Urine contains: • Water • HCO3- • Inorganic salts • H+ • Urea • Uric acid • Creatinine

  6. Excretion • Excretion - the majority of the metabolic wastes removed from the body is mainly due to the action of the kidneys.

  7. Organs of the Urinary System • Kidneys – main organ in the urinary system, produces urine. • Ureters - conduct urine from the kidneys to the bladder by peristaltic contractions produced from contractions of smooth muscles in ureter wall.

  8. Organs of the Urinary System • Urinary bladder - stores urine until it is expelled from the body. • Urethra - small tube that extends from the urinary bladder to an external opening. In males the urethra also functions as a reproductive tract organ.

  9. Functions of the Kidneys • Filter waste from blood • Maintenance of water-salt balance of the blood. • Regulates blood pressure • Maintenance of acid-base balance of the blood. • Secretion of hormones = renin and erythropoietin.

  10. Urinary System Kidney • Produces urine • Conserves water • Regulates pH • Stimulates production of red blood cells • Transforms vitamin D into active form Ureter • Transports urine from kidneys to bladder Urinary bladder • Stores urine Urethra • Transports urine from urinary bladder to outside the body Figure 16.2 (1 of 2)

  11. The kidneys are located in this cavity: • Cranial • Thoracic • Abdominopelvic • Pleural

  12. The Kidneys Adrenal gland Renal artery Renal vein Ureter Outermost connective tissue layer Innermost connective tissue layer Adipose capsule (a) Blood vessels and protective layers around kidneys Figure 16.3a

  13. The Regions of the Kidneys • Each kidney has three regions: • Renal cortex • Renal medulla • Renal pelvis/sinus

  14. Figure 16.3b Structure of the kidney Renal cortex Renal pyramid (of renal medulla) Renal column (extension of renal cortex) Renal pelvis (b) Internal kidney structure

  15. Regions of the Kidney • Renal cortex - an outer granulated layer. • Renal medulla - consists of cone-shaped tissue masses called renal pyramids. • Renal pelvis - a central cavity that is continuous with the ureter.

  16. Nephrons • The functional units of the kidneys. • Over 1 million nephrons per kidney • Nephrons extend from the Renal cortex, into the renal medulla

  17. The Nephron Figure 16.3b–c

  18. The Nephron Glomerular Capillaries at start of nephron Afferent (incoming) arteriole Efferent (outgoing) arteriole Distal convoluted tubule Glomerular capsule Proximal convoluted tubule Surrounding capillaries Loop of the nephron Collecting duct (b) A nephron and its blood supply Figure 16.4b

  19. Parts of the Nephron • The renal corpuscle • The glomerulus • The glomerular capsule • The renal tubule • Proximal convoluted tubule • Loop of the nephron (Loop of Henle) • Distal convoluted tubule • The collecting Duct

  20. The Nephron Glomerular capsule (glomerulus within) Renal corpuscle Proximal convoluted tubule Renal tubule Loop of the nephron Distal convoluted tubule (c) Simplified view of a nephron, showing the basic structural components but not the associated capillaries Figure 16.4c

  21. The renal corpuscle • The renal corpuscle is where fluid is filtered from blood • Consists of • The glomerulus - The network of capillaries • The glomerularcapsule (Bowman’s capsule) -Surrounds the glomerulus

  22. The Nephron • The nephron performs three functions • Glomerular filtration • Tubular reabsorption • Tubular secretion

  23. The Nephron - Glomerular filtration • Glomerular filtration occurs as blood pressure forces water, ions, and other small molecules in the blood through the pores in the glomerulus and into the glomerularcapsule • The filtrate passes into the renal tubule

  24. The Nephron Path of filtrate Path of blood Movement of water and small solutes Glomerulus Glomerular capsule Afferent (incoming) arteriole Space within the glomerular capsule Efferent (outgoing) arteriole Proximal convoluted tubule Filtrate (a) The renal corpuscle consists of the glomerular capsule and a ball of capillaries called the glomerulus. Capillary wall Figure 16.5a

  25. The Nephron Figure 16.5b

  26. The renal tubule • Proximal convoluted tubule (PCT) - where reabsorption of filtrate components occurs, tubular secretion can also occur here. • Loop of the Nephron (Loop of Henle) - consists of a descending limb and an ascending limb that regulates osmotic balance. • Distal convoluted tubule (DCT) – Further absorption of water and salts; leads to the renal pelvis

  27. Collecting Ducts • Collecting ducts - carry urine to the renal pelvis.

  28. The Nephron Step 3: Tubular secretion Wastes, excess ions, and drugs are actively secreted into the distal (and proximal) convoluted tubules from the surrounding capillaries. Some secretion also occurs along the collecting duct. Afferent (incoming) arteriole Efferent (outgoing) arteriole Drugs NH4+ H+ Nitrogen- containing waste Nitrogen- containing waste Step 1: Glomerular filtration Water, ions, amino acids, glucose, nitrogen-containing wastes, and other small molecules move from the glomerulus to the inside of the glomerular capsule to form glomerular filtrate. K+ H2O Glomerular capsule Glucose Ions Amino acids Glomerulus Glucose Ions H2O Artery Renal cortex Vein Renal medulla Step 2: Tubular reabsorption Water, essential ions, and nutrients are reabsorbed from the proximal convoluted tubule into the surrounding capillaries. Some reabsorption of water and ions occurs along other sections of the renal tubule and collecting duct. Collecting duct Surrounding capillaries Path of filtrate Loop of the nephron Urine Path of blood Movement of substances from blood to filtrate Renal pelvis within kidney Movement of substances from filtrate to blood Figure 16.7

  29. Urine Formation • Tubular reabsorption - many molecules are reabsorbed – transported from the lumen into the tissues then into capillaries. Occurs mainly in the PCT (H2O, nutrients, salts) and DCT • Tubular secretion - substances are removed from the blood and added to the tubular fluid, mainly in the DCT (H+, creatinine, and drugs like penicillin) and PCT

  30. This structure conducts urine from the kidneys to the bladder • Urethra • Ureters

  31. What is the functional unit of the kidney? • Renal medulla • Nephron • Renal cortex

  32. C C. Glomerular capsule, contains glomerulus A A. Renal Cortex F. Distal Convoluted Tubule B. Renal Medulla F D. Proximal Convoluted Tubule D B E. Loop of Henle E G. Collecting Duct G

  33. Regulation of Urine • Diuretics increase urinary output, making more dilute urine • Examples: • Caffeine • Lasix • Alcohol

  34. Hormonal Regulation of Urine • Antidiuretic hormone (ADH) • Makes more concentrated urine • Increases blood volume and pressure • Aldosterone • Makes more concentrated urine • Increases blood volume and pressure • Atrial Natriuretic Peptide (ANP) • Makes more dilute urine • Decrease blood volume and pressure

  35. Table 16.3 Review of Hormones

  36. Hormonal Regulation of Urine - ADH • Antidiuretic hormone (ADH) • Makes the collecting duct more permeable to water therefore, increases the water reabsorption in the collecting duct, making more concentrated urine. • Produced by the hypothalamus, stored in the posterior pituitary gland. • Site of action: collecting ducts.

  37. Diabetes insipidus • Diabetes insipidus is caused by producing too little ADH • Symptoms: excrete large amounts of dilute urine

  38. Kidney Function and ADH Decrease in concentration of water in blood is detected by the hypothalamus. An increase in the concentration of water in the blood causes: • Increase in blood volume • Increase in blood pressure • Decrease in urine volume Hypothalamus Nerve cells produce antidiuretic hormone (ADH) More water moves from the filtrate back into the blood. Anterior lobe of pituitary gland Posterior lobe of pituitary gland Antidiuretic hormone (ADH) is produced by the hypothalamus and released by the posterior lobe of the pituitary gland. ADH prompts an increase in the permeability to water of distal convoluted tubules and collecting ducts of nephrons. Figure 16.9

  39. Hormonal Regulation of Urine - Aldosterone • Aldosterone • Hormone produced and released by the adrenal cortex • Increases sodium reabsorption in the distal convoluted tubule and the collecting duct, water follows • Making more concentrated urine.

  40. Juxtaglomerular apparatus and Aldosterone • Aldosterone is released in response to blood pressure monitored by the juxtaglomerular apparatus • The cells in the juxtaglomerular apparatus release the hormone renin. • Renin is converted to an active form that stimulates the adrenal cortex to release aldosterone

  41. Kidney Function and Hormones Figure 16.10

  42. Hormonal Regulation of Urine - ANP • Atrial Natriuretic Peptide (ANP) • Hormone produced by the heart in response to increased blood volume and pressure • Decreases sodium reabsorption in the distal convoluted tubule and the collecting duct, water stays in the filtrate • Also inhibits production of aldosterone and renin • Making more dilute urine. Lowers blood pressure and blood volume

  43. Hormones Produced by the kidneys • Renin – Increases blood pressure by triggering the release of aldosterone by the adrenal cortex • Erythropoietin – speeds up the maturation process of RBCs, target = stem cells in bone marrow

  44. The Kidney’s role in Vit D • Vitamin D is produced in the skin in response to sunlight, and provided by certain foods in diet • The kidneys and liver transform Vitamin D into the active form, calcitrol. • Calcitrol promotes the absorption of calcium into the small intestine and reabsorption of calcium in the kidneys.

  45. Kidney’s role in Acid-Base Balance • H+ is secreted into the tubules and bicarbonate is reabsorbed out of the tubules

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