Urinary System Urinary System A. Kidneys A. Kidneys 1. External anatomy 1. External anatomy 2. Internal anatomy 2. Internal anatomy 3. Nephron 3. Nephron a. Parts of the nephron a. Parts of the nephron b. Cortical and b. Cortical and juxtamedullary juxtamedullary nephrons nephrons c. Histology of the c. Histology of the nephron nephron 4. Blood and nerve supply 4. Blood and nerve supply B. Physiology of urine formation B. Physiology of urine formation 1. Glomerular filtration 1. Glomerular filtration a. Net filtration a. Net filtration pressure pressure b. Glomerular filtration b. Glomerular filtration rate rate c. Regulation of GFR c. Regulation of GFR 2. Tubular reabsorption 2. Tubular reabsorption 3. Countercurrent multiplier 3. Countercurrent multiplier and and exchange system exchange system 4. Tubular secretion 4. Tubular secretion 5. Renal clearance 5. Renal clearance C. Ureters C. Ureters 1. Structure 1. Structure 2. Histology 2. Histology 3. Physiology 3. Physiology D. Urinary bladder D. Urinary bladder 1. Structure 1. Structure 2. Histology 2. Histology 3. Physiology 3. Physiology E. Urethra E. Urethra 1. Histology 1. Histology 2. Physiology 2. Physiology
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Urinary System A. Kidneys 1. External anatomy 1. External anatomy 2. Internal anatomy 2. Internal anatomy 3. Nephron 3. Nephron a. Parts of the nephron.
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Urinary SystemUrinary SystemA. KidneysA. Kidneys 1. External anatomy1. External anatomy 2. Internal anatomy2. Internal anatomy 3. Nephron3. Nephron a. Parts of the nephrona. Parts of the nephron b. Cortical and juxtamedullary b. Cortical and juxtamedullary
nephrons nephrons c. Histology of the nephronc. Histology of the nephron 4. Blood and nerve supply4. Blood and nerve supplyB. Physiology of urine formationB. Physiology of urine formation 1. Glomerular filtration1. Glomerular filtration a. Net filtration pressurea. Net filtration pressure b. Glomerular filtration rateb. Glomerular filtration rate c. Regulation of GFRc. Regulation of GFR 2. Tubular reabsorption2. Tubular reabsorption 3. Countercurrent multiplier and 3. Countercurrent multiplier and
exchange system exchange system 4. Tubular secretion4. Tubular secretion 5. Renal clearance5. Renal clearance
What is excretion? What is excretion? How is it different from secretion?How is it different from secretion?Why do we need a urinary system?Why do we need a urinary system?
1. protein catabolism yields toxic 1. protein catabolism yields toxic nitrogenous wastes nitrogenous wastes
(ammonia and urea)(ammonia and urea)
2. water and essential ions tend to 2. water and essential ions tend to accumulateaccumulate
Organs that contribute to the function of Organs that contribute to the function of waste elimination from the body include:waste elimination from the body include:
1. location1. location a. T12 - L3a. T12 - L3 b. retroperitonealb. retroperitoneal2. gross appearance2. gross appearance3. hilus3. hilus4. coverings4. coverings a. renal fasciaa. renal fascia b. adipose capsuleb. adipose capsule c. renal capsulec. renal capsule
Kidney-internalKidney-internal1. medulla1. medulla a. renal pyramidsa. renal pyramids b. renal papillaeb. renal papillae2. cortex2. cortex a. renal columnsa. renal columns b. cortical b. cortical vsvs
juxtamedullary nephronsjuxtamedullary nephrons3. renal pelvis and calyces3. renal pelvis and calyces
Nephrons, the functional units of the Nephrons, the functional units of the kidneys, have three basic functions:kidneys, have three basic functions:
1. filtration1. filtration
2. reabsorption2. reabsorption
3. secretion3. secretion
Types of NephronsTypes of Nephrons
1. cortical (85%)1. cortical (85%)
2. juxtamedullary (15%)2. juxtamedullary (15%)
juxtamedullary nephron(with very long loop of Henle)
cortical nephron(with relatively short loop of Henle)
Parts of a NephronParts of a Nephron
1. renal corpuscle1. renal corpuscle a. glomerulusa. glomerulus b. Bowman's capsuleb. Bowman's capsule (parietal vs visceral)(parietal vs visceral)2. renal tubule2. renal tubule a. proximal convoluteda. proximal convoluted b. loop of Henleb. loop of Henle c. distal convolutedc. distal convoluted
Bowman's capsule and the endothelial-Bowman's capsule and the endothelial-capsular membranecapsular membrane
1. parietal vs. visceral layers1. parietal vs. visceral layers2. fenestrated endothelial cells2. fenestrated endothelial cells (restrict formed elements)(restrict formed elements)3. fused basement membranes3. fused basement membranes (restrict plasma proteins)(restrict plasma proteins)4. visceral layer = podocytes4. visceral layer = podocytes a. pedicelsa. pedicels b. filtration slitsb. filtration slits
Nerve supply of the kidneysNerve supply of the kidneys
Renal nerves arise from the superior Renal nerves arise from the superior mesenteric ganglion- mostly mesenteric ganglion- mostly sympathetic fiberssympathetic fibers
Regulate blood flow and stimulate Regulate blood flow and stimulate secretion of reninsecretion of renin
Nephrons carry out three Nephrons carry out three important functions:important functions:
1. control blood concentration and 1. control blood concentration and volumevolume
2. regulate blood pH2. regulate blood pH
3. remove toxic wastes from the blood3. remove toxic wastes from the blood
What do nephrons accomplish?What do nephrons accomplish?
Urine formation requires three Urine formation requires three processes:processes:
1. glomerular filtration by the renal corpuscle1. glomerular filtration by the renal corpuscle
2. tubular reabsorption by the renal tubule2. tubular reabsorption by the renal tubule
3. tubular secretion by the renal tubule3. tubular secretion by the renal tubule
Glomerular filtration is the first Glomerular filtration is the first step in urine formation.step in urine formation.
1. principle of filtration1. principle of filtration
Features of the renal corpuscle that Features of the renal corpuscle that enhance its blood-filtering capacity:enhance its blood-filtering capacity:
1. glomerular capillaries are long1. glomerular capillaries are long
2. endothelial-capsular membrane is 2. endothelial-capsular membrane is porous and thinporous and thin
3. glomerular blood hydrostatic 3. glomerular blood hydrostatic pressure is high due to relationship pressure is high due to relationship between afferent and efferent arteriolesbetween afferent and efferent arterioles
Net filtration pressure (NFP)Net filtration pressure (NFP)
When BP is too high, ANP is produced When BP is too high, ANP is produced by the heart which inhibits sodium and by the heart which inhibits sodium and water reaborption and the secretion of water reaborption and the secretion of renin and ADH. Kidneys eliminate renin and ADH. Kidneys eliminate more sodium and water and lower more sodium and water and lower blood pressureblood pressure
Neural Regulation of GFRNeural Regulation of GFR
Sympathetic Nervous SystemSympathetic Nervous System
Tubular Reabsorption of SolutesTubular Reabsorption of Solutes1. tubular maximum (TM)1. tubular maximum (TM)2. active transport2. active transport a. receptors (carriers)a. receptors (carriers) b. glucose and amino acidsb. glucose and amino acids (100% of the time)(100% of the time) c. Na+ and K+c. Na+ and K+ (aldosterone controlled)(aldosterone controlled) d. Ca++d. Ca++ (PTH and CT controlled)(PTH and CT controlled)3. passive transport (diffusion)3. passive transport (diffusion) a. diffusion or electricala. diffusion or electrical b. Cl-, PO4--b. Cl-, PO4--
Tubular Reabsorption of WaterTubular Reabsorption of Water
RECEPTORHypothalamic osmoreceptors respond to increased blood osmotic pressure and
send nerve impulses to appropriate neurons in hypothalamus
CONTROL CENTERHypothalamic neurons, via the posterior pituitary gland, secrete ADH in the blood
EFFECTORSIn response to ADH, aquaporins in distal
tubules and collecting ducts become more permeable to water
RETURN TO HOMEOSTASISIn response, there is increased water
reabsorption, and blood osmotic pressure decreases
Blood osmotic pressure (decreased water concentration) is increased in response to
some stressor
The concentration gradient in The concentration gradient in interstitial fluidinterstitial fluid
Contributing factors:Contributing factors:
1.1.The nephron loop via the countercurrent multiplierThe nephron loop via the countercurrent multiplier
2.2.The Vasa recta via the countercurrent exchange systemThe Vasa recta via the countercurrent exchange system
3.3.Urea RecyclingUrea Recycling
The countercurrent multiplier-Responsible for The countercurrent multiplier-Responsible for establishing the salt concentration gradient with the establishing the salt concentration gradient with the interstitial fluid.interstitial fluid.
If H+ secretion = HCO3- filtration then no change occurs in extracellular fluid pH.
If H+ secretion > HCO3- filtration, then extracellular fluid (blood)pH increases.
If H+ secretion < HCO3- filtration, then extracellular fluid(blood) pH decreases.
Secretion and Neutralization of Secretion and Neutralization of H+ ions in KidneyH+ ions in Kidney
Renal ClearanceRenal Clearance
Renal clearance is the volume of blood Renal clearance is the volume of blood plasma from which a particular waste is plasma from which a particular waste is completely removed in 1 minute.completely removed in 1 minute.
What would you expect the renal What would you expect the renal clearance of glucose to be in a normal clearance of glucose to be in a normal individual?individual?
Summary of Nephron FunctionsSummary of Nephron Functions
Urine DrainageUrine Drainage
1. papillary ducts --->1. papillary ducts ---> minor calyces --->minor calyces ---> major calyces --->major calyces ---> renal pelvis --->renal pelvis --->2. ureters2. ureters a. locationa. location b. anatomyb. anatomy c. functionc. function
Urinary BladderUrinary Bladder
1. location1. location
2. anatomy2. anatomy
3. histology3. histology
a. detrusor musclea. detrusor muscle
b. sphinctersb. sphincters
4. micturition reflex4. micturition reflex
UrethraUrethra
1. anatomy1. anatomy
2. location2. location
a. femalea. female
b. maleb. male
(1) prostatic(1) prostatic
(2) membranous(2) membranous
(3) penile(3) penile
Micturition reflex (in the adult)Micturition reflex (in the adult)
1. stretch of the bladder (1/2 full) stimulates stretch 1. stretch of the bladder (1/2 full) stimulates stretch receptors receptors 2. sacral parasympathetic area output, causing:2. sacral parasympathetic area output, causing: a. contraction of the detrusor muscle; anda. contraction of the detrusor muscle; and b. reflex relaxation of the internal urethral sphincterb. reflex relaxation of the internal urethral sphincter3. association neuron carries information to cerebrum 3. association neuron carries information to cerebrum for conscious awareness for conscious awareness4. voluntary relaxation of the external urethral 4. voluntary relaxation of the external urethral sphinctersphincter
(in the infant, this is also reflexive)(in the infant, this is also reflexive)5. expulsion of urine through urethra5. expulsion of urine through urethra
Neural Control of MicturitionNeural Control of Micturition