Urinary System Functions of the Urinary system (renal) A. B. C.

Transcription

1 Urinary System Functions of the Urinary system (renal) A. B. C. I. Overview of fluids A. Normal volumes 1. fluid intake a. = 1500 ml b. = 750 ml c. = 250 ml (remember ETS) d. total = 2500 ml/day 2. fluid output a. = 1500 ml b. = 700 ml (evaporation + respiration) c. = 200 ml d. = 100 ml = 2500 ml/day B. Variations in Volumes 1. causes concentration of solutes to increase 2. - hot weather, exercise 3. normal, diarrhea, constipation 4. help to control urine production II. Anatomy - overview of Urinary System (all retroperitoneal) A. (2) see functions of urinary system B. (2) hollow tubes to urinary bladder C. (1) storage of urine D. (1) hollow, drainage tube to outside body

2 III. Kidney (Renes) macroscopic structure A. bean shaped with medial hilus 1. renal artery ( into kidney) 2. ureter ( out of kidney) 3. renal vein ( out of kidney) B. located retroperitoneal and protected by fat and capsule C. receives about of cardiac output D. regions 1. cortex a. outer layer b. = beginning of blood filtration c. extend into medulla and separate pyramids 2. medulla a. middle layer b. 8 to 18 cone-shaped red tissue with a base and an apex (papilla) 3. pelvis a. medially located and connecting to hilus b. contains tubes that collects urine which has dripped from papilla of pyramids c. - pyramids to minor calyces to major calyces to ureter IV. Ureters A. hollow tubes connecting kidneys to urinary bladder B. retroperitoneal C. 3 layers 1. fibrous layer ( ) 2. muscularis ( ) circular and longitudinal - responsible for peristalsis 3. mucosa = mucus membrane ( ) stratified transitional epithelium

3 V. Urinary bladder A. collapsible muscular sac that stores urine B. C. 3 layers 1. fibrous layer (outer) 2. thick muscularis called detrusor muscle to thrust out 3. mucosa mucus membrane = stratified transitional epithelium D. trigone 1. 3 openings ( ) 2. located on posterior wall 3. infections tend to occur here E. internal folds when empty F. sphincters 1. internal a. smooth muscle b. found at junction of bladder and urethra 2. external a. skeletal muscle around urethra b. found in sheet of tissue called urogenital diaphragm 3. control a. - in general, less control because urethra and vagina pass through urogenital diaphragm b. in general, more control because only urethra passes through urogenital diaphragm

4 VI. Urethra A. hollow tube to void urine from body B. epithelium lining 1. beginning - end - C. gender differences 1. female a. about 1.5 inches in length b. short urethra means more urinary tract infections ( ) c. opening in vestibule just anterior to vagina 2. male a. about 8 inches in length b. carries urine and semen c. 3 regions of urethra i. connects to urinary bladder and passes through prostate gland swollen prostate can cause problems with urination - connects with 2 ejaculatory ducts (so reproductive fuses with urinary) - prostate just anterior to rectum (physical exams) ii. passes through urogential diaphragm iii. - passes through penis VII. Micturition = voiding = urination A. micturition reflex 1. young children can t control external ( ) sphincter 2. Post-Potty Trained Individuals (PPTI s) working cerebral cortex means control over external sphincter 3. inability to control urination 4. urinary retention a. bladder unable to expel urine b. common after anesthesia c. may indicate prostate problems d. catheter inserted to drain urine

5 Microscopic Structure of Kidney I. Nephron - general A. functional unit of kidney ( ) B. 1 million per kidney C. contains blood vessels and tubes for making filtrate and urine D. filtrate in and urine out E. good and bad from blood plasma (except blood proteins) F. filtrate processed in tubules of the nephron II. Nephron blood supply = the pathway for blood A. aorta B. renal artery C. renal artery branches B. afferent arterioles 1. found in the cortex 2. diameter larger then efferent arterioles C. glomerulus ( ) 1. found in the cortex 2. tuft of capillaries surrounded by the beginning of the tubules 3. high pressure area that forces everything in blood plasma out of capillaries except blood proteins D. efferent arterioles 1. found in the cortex 2. diameter smaller then afferent arterioles E. peritubular capillaries 1. found in the cortex and medulla 2. surround kidney tubules 3. reabsorb most ( ) of the filtrate back to the blood F. renal vein branches G. renal vein H. inferior vena cava

6 III. Nephron kidney tubules = the path of fitrate A. tube with a single layer of epithelium performing 3 functions 1. - good and bad from blood plasma (except blood proteins) move from blood (glomerulus) into tubules (glomerular capsule) 2. - most filtrate (99%) is put back into the blood 3. second chance to move bad solutes from blood (peritubular capillaries) into tubules (mostly DCT) B. Bowman s capsule or glomerular capsule 1. found in the cortex 2. surrounds collection of capillaries called glomerulus 3. site of filtration 4. podocytes for holding on to glomerulus and receiving filtrate C. proximal convoluted tubule (PCT) 1. found in the cortex 2. winding tube leaving Bowman s capsule 3. simple cuboidal with microvilli for reabsorption D. loop of Henle 1. found in the medulla 2. contains descending and ascending sections 3. gives the renal pyramids their striped appearance 4. - simple squamous for easy exchange of water/ions E. distal convoluted tubule (DCT) 1. found in the cortex 2. last segment before entering collecting duct 3. - simple cuboidal without microvilli for secretion F. collecting duct 1. found in the medulla 2. receives urine from nephrons G. papillary ducts H. papilla ( ) of pyramids I. minor calyces J. major calyces K. ureter

7 IV. Nephron renal corpuscle = blood meets tubules A. 2 main parts 1. glomerulus 2. Bowman s capsule or glomerular capsule analogy B. three layers of tissue between glomerulus and Bowman s capsule 1. endothelium of glomerular capillaries a. - epithelium b. fenestrated (many holes) 2. basement membrane shared by glomerulus and Bowman s capsule 3. visceral membrane of Bowman s capsule a. made from ( specialized epithelium) b. wrap around glomerular capillaries like fingers c. forms filtration slits C. 2 filters 1. fenestrated glomerular capillary 2. filtration slits D. Function of the filters 1. filters keep large molecules ( ) in capillary and allows small molecules ( ) to enter Bowman s capsule 2. filtrate will move from glomerular capillary to Bowman s capsule based on pressure difference (just like our discussion of capillary dynamics!) 3. filtrate is the good and the bad from the blood plasma ( ) to be sorted out later

8 Draw a Nephron in 3 easy steps 1. Draw renal corpuscle 2. Draw blood flowing to and from renal corpuscle 3. Draw kidney tubules 3 Main Functions of Nephron 1. Glomerular filtration filtrate out of blood 2. Tubular reabsorption good stuff back in to blood 3. Tubular secretion second chance to pull solutes from blood to tubules

9 Glomerular Filtration I. General A. movement of fluids from glomerulus ( ) to glomerular capsule ( ) B. glomerular filtration rate ( ) 1. amount of filtrate formed per minute 2. normal GFR = 125 ml/min = 180 L/day (you filter your plasma 60 times/day) 3. remember systemic capillaries filtrated out an extra 3 liters/day. We called that. C. Why 180 L/day in the kidneys and only 3 L/day in the rest of the body? 1. glomerulus membrane 1000 times more than systemic capillaries 2. glomerulus under a much higher than systemic capillaries II. 3 factors that affect the amount of filtrate formed A. surface area of filtration membrane ( ) B. membrane permeability ( ) C. net filtration pressure ( with blood pressure) ********

10 III. components of Net Filtration Pressure (NFP) A. Glomerular (Blood) Hydrostatic Pressure (BHP) 1. force that blood out of glomerulus and into Bowman s capsule 2. equal to 55 mm Hg (compared to 30 mm Hg in systemic capillaries) B. Capsular Hydrostatic Pressure (CHP) 1. force that blood out of Bowman s capsule and into glomerulus 2. resistance by fluid already in - 3. Don t rush me I ve got enough to do resistance 4. equal to 15 mm Hg C. Glomerular (Blood) Osmotic Pressure (BOP) 1. water goes where the stuff is pressure 2. proteins in blood to large to get into Bowman s capsule. 3. proteins tend to water out of capsule and back to glomerulus. 4. equal to 30 mmhg D. Capsular Osmotic Pressure (COP) 1. water goes where the stuff is pressure 2. proteins in blood to large to get into Bowman s capsule. 3. if no proteins in Bowman s capsule, then the on water is zero IV. Total equation NFP = net glomerular net capsular = ( + ) ( + ) = (55 mm Hg + 0 mm Hg) (15 mm Hg + 30 mm Hg) = 55 mm Hg 45 mm Hg = 10 mm Hg out of glomerulus (capillaries) to Bowman s capsule V. ********GFR is directly proportional to NFP********* 1. If NFP increase, then GFR 2. If NFP decreases, then GFR

11 VI. What if A..blood pressure drops? 1. glomerular BHP goes 2. less blood pushed out of glomerulus 3. less filtrate being formed 4. kidney/nephrons B..blood pressure rises? 1. glomerular BHP goes 2. too much blood pushed out of glomerulus 3. too much filtrate being formed 4. can t filter properly and Bowman s capsules destroyed under high pressure (hypertensive kidney C..dehydration 1. blood volume decreases 2. BOP increases (Why? ) 3. BHP decreases (Why? ) VII. regulation of Glomerular Filtration Rate (GFR) A. renal autoregulation changing diameter of to control BHP 1. myogenic mechanism a. smooth muscle response to stretch b. increased systemic BP causes afferent arteriole to decreasing flow and decreasing BHP c. decreased systemic BP causes afferent arteriole to increasing flow and increasing BHP 2. tubuloglomerular feedback mechanism a. juxtaglomerular apparatus equals afferent arteriole (blood in) and macula densa of distal convoluted tubule b. macula densa cells ( )of the juxtaglomerular apparatus sense speed of filtrate flow and solute concentrations (osmolarity) c. slow flow/low osmolarity triggers causes afferent arteriole to increasing flow and increasing BHP d. fast flow/high osmolarity triggers afferent arteriole to decreasing flow and decreasing BHP

12 B. Neural Controls 1. sympathetics at rest, afferent arteriole 2. sympathetics active, afferent arteriole wants to constrict to divert blood to the skeletal muscles but other factors help keep BHP normal C. renin-angiotensin system 1. juxtaglomerular apparatus equals afferent arteriole (blood in) and macula densa of distal convoluted tubule 2. juxtaglomerular cells ( )of the juxtaglomerular apparatus sense low blood pressure 3. If blood pressure is too low, juxtaglomerular cells release rennin ( ) which causes angiotensinogen ( ) to change to angiotensin I and then to angiotensin II. 4. Angiotension II causes: a. of efferent arteriole -shutting door out increases BHP b. to be produced i. more salt reabsorbed therefore more water reabsorbed ii. more water increases blood volume which causes blood pressure to increase c. (ADH) to be produced i. water is reabsorbed ii. results in water retention and smaller amounts of urine production iii. more water increases blood volume which causes blood pressure to increase

13 Tubular Reabsorption I. Overview A. about 99% of filtrate is returned to bloodstream B. nephrons ability to remove or partially remove a substance from blood (urea, creatinine) C. movement into peritubular capillaries is fast because: 1. hydrostatic pressure-loss of filtrate into glomerular capsule 2. osmotic pressure proteins stayed in blood II. Reabsorption mechanisms A. 1. cost is ATP and a carrier molecule is needed 2. result a. ions (Na +, K +, Ca +, etc ) and molecules (glucose, amino acids, etc ), are transported from kidney tubules to blood (peritubular capillaries) b. mechanisms like sodium potassium pump are working 3. renal threshold a. maximum amount of an ion or molecule that can be shipped out of tubules b. glucose workers, sodium workers, etc B. 1. sodium reabsorbed first 2. water follows Why? water goes were the stuff is 3. then other ions follow Why? ions are more concentrated now that water has left so they follow their concentration gradient

14 III. Location of Reabsorption A % of reabsorption 2. active transport ( ) and passive transport (sodium first, then water, then ions) B. loop of Henle 1. major area that regulates urine we make 2. countercurrent mechanism a. descending loop of Henle loses water, but not salt, therefore filtrate gets more concentrated b. ascending loop of Henle loses salt and not water c. concentrate and pump out, repeat C. distal convoluted tubule and collecting ducts - under hormonal control 1. antidiuretic hormone ( ) a. if solute in high concentration (not enough water) b. ADH released c. water reabsorbed in DCT and collecting duct d. results in water retention and less urine production e. alcohol and caffeine ADH from being released. Therefore you urinate more than normal and become dehydrated.

15 2. aldosterone and sodium a. most sodium reabsorbed in PCT ( ) b. some saved for loop of Henle (countercurrent mechanism) c. aldosterone controls reabsorption of any remaining sodium in DCT and collecting duct. i. sodium means: - higher levels of aldosterone produced - more sodium reabsorbed - water follows so more water reabsorbed from DCT and collecting duct - less urine produced - example ii. in sodium means: - lower levels of aldosterone produced - less sodium reabsorbed - water follows so less water reabsorbed from DCT and collecting duct - more urine produced - example 3. aldosterone and potassium a. most potassium reabsorbed in PCT b. then most secreted back into filtrate in kidney tubules c. aldosterone controls reabsorption of any remaining potassium in DCT and collecting duct. i. in potassium means: - higher levels of aldosterone produced - more potassium reabsorbed - water follows so more water reabsorbed from DCT and collecting duct - less urine produced ii. in potassium means - lower levels of aldosterone produced - less potassium reabsorbed - water follows so less water reabsorbed from DCT and collecting duct - more urine produced d. high potassium levels are dangerous and could stop heart e. potassium overrides sodium to make/not make aldosterone

16 4. parathyroid hormone a. most calcium reabsorbed in PCT b. if calcium levels low, parathyroid hormone increases reabsorption of calcium in DCT and collecting duct c. bones and digestion other sources of more calcium

17 Tubular Secretion I. Secretion pertaining to endocrine system II. Secretion pertaining to kidney (opposite of reabsorption) III. Kidneys last chance to get certain materials out of peritubular capillaries to kidney tubules IV. What is being secreted? A. certain things that were not filtrated ( ) B. urine samples to test for drugs C. wastes that had been reabsorbed ( ) D. extra potassium E. regulating ph 1. if blood is too acidic (low ph), then is secreted making the filtrate acidic and increasing blood ph 1. if blood is too basic (high ph), then is secreted making the filtrate basic and increasing blood ph