Urinary System

Introduction Consists of Consists of 1. Two kidneys 2. Two ureters 3. One urinary bladder 4. One urethra

Introduction Urine is excreted from each kidney through its ureter and is stored in the urinary bladder Urine is excreted from each kidney through its ureter and is stored in the urinary bladder

Introduction Urine is expelled from the body through the urethra Urine is expelled from the body through the urethra

Anatomy of Kidneys Retroperitoneal organs Retroperitoneal organs

External Anatomy of Kidneys Hilus – A vertical fissure near the center of the concave medial border Hilus – A vertical fissure near the center of the concave medial border

External Anatomy of Kidneys Ureters leave and blood vessels, lymphatic vessels, and nerves enter and exit at the hilus Ureters leave and blood vessels, lymphatic vessels, and nerves enter and exit at the hilus

Internal Anatomy of Kidneys Consists of Consists of 1. Cortex 2. Medulla 3. Pyramids 4. Papillae 5. Columns 6. Minor and Major calyces 7. Renal pelvis

Internal Anatomy of Kidneys Nephron – functional unit of the kidney Nephron – functional unit of the kidney

Blood and Nerve Supply of the Kidneys Blood enters the kidney through the renal artery Blood enters the kidney through the renal artery

Blood and Nerve Supply of the Kidneys Blood exits via the renal vein Blood exits via the renal vein

Nephrons Consists of Consists of 1. Renal corpuscle 2. Renal tubule

Renal Corpuscle Where fluid is filtered Where fluid is filtered

Renal Corpuscle Consists of 1. Glomerulus 2. Glomerular Capsule

Renal Corpuscle Glomerulus – capillary knot Glomerulus – capillary knot

Renal Corpuscle The glomerular capsule consists of The glomerular capsule consists of 1. Visceral layer 2. Parietal layer 3. Capsular Space

Renal Corpuscle The visceral layer consists of modified simple squamous epithelial cells called podocytes The visceral layer consists of modified simple squamous epithelial cells called podocytes

Renal Corpuscle The parietal layer consists of simple squamous epithelium and forms the outer wall of the capsule The parietal layer consists of simple squamous epithelium and forms the outer wall of the capsule

Renal Corpuscle Fluid filtered from the glomerular capillaries enters the capsular space Fluid filtered from the glomerular capillaries enters the capsular space

Renal Corpuscle Capsular space – the space between the two layers of the glomerular capsule Capsular space – the space between the two layers of the glomerular capsule

Renal Tubule Filtered fluid passes through here Filtered fluid passes through here

Nephron Renal tubule Renal tubule 1. Proximal convoluted tubule 2. Loop of Henle 3. Distal convoluted tubule

Nephron Distal convoluted tubules of several nephrons drain into to a single collecting duct Distal convoluted tubules of several nephrons drain into to a single collecting duct

Nephron Many collecting ducts drain into a small number of papillary ducts Many collecting ducts drain into a small number of papillary ducts

Nephron These empty urine into the minor calyces These empty urine into the minor calyces

Nephron Loop of henle consists of Loop of henle consists of 1. Descending limb 2. Thin ascending limb 3. Thick ascending limb

Nephron Two types of nephrons Two types of nephrons 1. Cortical nephron 2. Juxtamedullary nephron

Cortical Nephron Has its glomerulus in the outer portion of the cortex Has its glomerulus in the outer portion of the cortex

Cortical Nephron And a short loop of Henle that penetrates only into the outer region of the medulla And a short loop of Henle that penetrates only into the outer region of the medulla

Juxtamedullary Nephron Has its glomerulus deep in the cortex close to the medulla Has its glomerulus deep in the cortex close to the medulla

Juxtamedullary Nephron Its long loop of Henle stretches through the medulla and almost reaches the papilla Its long loop of Henle stretches through the medulla and almost reaches the papilla

Renal Tubule and Collecting Duct Most of the cells of the distal convoluted tubule have receptors for ADH and aldosterone Most of the cells of the distal convoluted tubule have receptors for ADH and aldosterone

Juxtaglomerular Apparatus (JGA) Helps regulate blood pressure and the rate of blood filtration by the kidneys Helps regulate blood pressure and the rate of blood filtration by the kidneys

Juxtaglomerular Apparatus (JGA) Consists of Consists of 1. Juxtaglomerular cells 2. Macula Densa

Juxtaglomerular Cells Located on an afferent arteriole Located on an afferent arteriole

Macula Densa Located on the distal convoluted abutting the JG cells Located on the distal convoluted abutting the JG cells

Renal Physiology Nephrons and collecting ducts perform three basic processes while producing urine Nephrons and collecting ducts perform three basic processes while producing urine

Renal Physiology 1. Glomerular filtration 2. Tubular secretion 3. Tubular reabsorption

Glomerular Filtration Glomerular filtrate - the fluid that enters the capsular space Glomerular filtrate - the fluid that enters the capsular space

Glomerular Filtration The principle of filtration – to force fluids and solutes through a membrane by pressure The principle of filtration – to force fluids and solutes through a membrane by pressure

Glomerular Filtration Glomerular Filtration rate (GFR) – the amount of filtrate formed by both kidney per minute Glomerular Filtration rate (GFR) – the amount of filtrate formed by both kidney per minute

Glomerular Filtration GFR – 125ml/minute GFR – 125ml/minute

Glomerular Filtration This amounts of 180 liters of filtrate per day This amounts of 180 liters of filtrate per day

Glomerular Filtration Because of further processing we only excrete 1-2 liters of urine per day Because of further processing we only excrete 1-2 liters of urine per day

Glomerular Filtration Only call it urine after it drips out of the collecting ducts into the calyceal system Only call it urine after it drips out of the collecting ducts into the calyceal system

Neural Autoregulation Through the ANS Through the ANS

Neural Autoregulation During extreme emergencies such as shock, sympathetics to afferent arterioles cause them to constrict During extreme emergencies such as shock, sympathetics to afferent arterioles cause them to constrict

Neural Regulation Blood flow into glomerular capillaries is greatly decreased and GFR drops Blood flow into glomerular capillaries is greatly decreased and GFR drops

Neural Regulation Lowering of renal blood flow has two consequences Lowering of renal blood flow has two consequences

Neural Regulation 1. Reduces urine output, which conserves blood volume

Neural Regulation 2. It permits greater blood flow to other body tissues

Neural Regulation Severe hypotension can cause death of part of the tubules, decreases urine output, and kidney failure Severe hypotension can cause death of part of the tubules, decreases urine output, and kidney failure

Hormonal Regulation With mild drops of BP sympathetics stimulate renin secretion on JG cell by targeting B1 receptors With mild drops of BP sympathetics stimulate renin secretion on JG cell by targeting B1 receptors

Hormonal Regulation Renin converts angiotensinogen to angiotensin I Renin converts angiotensinogen to angiotensin I

Hormonal Regulation Angiotensin I is converted by angiotensin converting enzyme to angiotensin II Angiotensin I is converted by angiotensin converting enzyme to angiotensin II

Hormonal Regulation Angiotensin II causes efferent arteriole to constrict more than afferent arterioles, maintaining filtration Angiotensin II causes efferent arteriole to constrict more than afferent arterioles, maintaining filtration

Hormonal Regulation Angiotensin II also leads to the formation of aldosterone Angiotensin II also leads to the formation of aldosterone

Hormonal Regulation Aldosterone causes sodium and water retention and potassium excretion Aldosterone causes sodium and water retention and potassium excretion

Principles of Renal Transport Reabsorption – returns most of the filtered water and many of the filtered solutes (such as glucose, sodium, etc.) to the bloodstream Reabsorption – returns most of the filtered water and many of the filtered solutes (such as glucose, sodium, etc.) to the bloodstream

Principles of Renal Transport Tubular secretion – the transfer of materials from the blood and tubule cells into tubular fluid Tubular secretion – the transfer of materials from the blood and tubule cells into tubular fluid

Principles of Renal Transport Tubular secretion helps control blood pH and helps eliminate other substances from the body Tubular secretion helps control blood pH and helps eliminate other substances from the body

Principles of Renal Transport Solute reabsorption drives water reabsorption Solute reabsorption drives water reabsorption

Reabsorption in the Proximal Convoluted Tubule The majority of the solute and water reabsorption from filtered fluid occurs in the proximal convoluted tubules The majority of the solute and water reabsorption from filtered fluid occurs in the proximal convoluted tubules

Reabsorption in the Proximal Convoluted Tubule Reabsorption of Na and other solutes creates an osmotic gradient that promotes reabsorption of water by osmosis Reabsorption of Na and other solutes creates an osmotic gradient that promotes reabsorption of water by osmosis

Reabsorption in the Proximal Convoluted Tubule Proximal convoluted Na transporters promote reabsorption of organic solutes such as Proximal convoluted Na transporters promote reabsorption of organic solutes such as 1. Glucose 2. Amino acids 3. Bicarbonate ions 4. Water 5. Na 6. K 7. Cl 8. Other ions and vitamins

Secretion of NH3 and NH4 in the Proximal Convoluted Tubule The deamination of the amino acid glutamine by PCT cells generates NH3 and new HCO3- The deamination of the amino acid glutamine by PCT cells generates NH3 and new HCO3-

Secretion of NH3 and NH4 in the Proximal Convoluted Tubule Most NH3 quickly binds to H+ and becomes NH4+ Most NH3 quickly binds to H+ and becomes NH4+

Secretion of NH3 and NH4 in the Proximal Convoluted Tubule NH4+ can substitute H+ aboard the Na+/H+ antiporters and be secreted into tubular fluid NH4+ can substitute H+ aboard the Na+/H+ antiporters and be secreted into tubular fluid

Reabsorption in the Loop of Henle Water reabsorption is not directly coupled with sodium reabsorption Water reabsorption is not directly coupled with sodium reabsorption

Reabsorption in the Loop of Henle In the descending limb, water is reabsorbed via osmosis In the descending limb, water is reabsorbed via osmosis

Reabsorption in the Loop of Henle As water is reabsorbed from the descending limb, the osmolality of the filtrate increases As water is reabsorbed from the descending limb, the osmolality of the filtrate increases

Reabsorption in the Loop of Henle In the ascending limb, Na+, K+, Cl- symporters reclaim Na+, Cl-, and K+ ions from the tubular lumen fluid. In the ascending limb, Na+, K+, Cl- symporters reclaim Na+, Cl-, and K+ ions from the tubular lumen fluid.

Reabsorption in the Loop of Henle As sodium and chloride are reabsorbed from the ascending limb, the osmolality of the filtrate decreases As sodium and chloride are reabsorbed from the ascending limb, the osmolality of the filtrate decreases

Reabsorption in the DCT As fluid flows along the DCT, reabsorption of Na+ and Cl- continues due to Na+ - Cl- symporters As fluid flows along the DCT, reabsorption of Na+ and Cl- continues due to Na+ - Cl- symporters

Reabsorption in the DCT The DCT serves as the major site where parathyroid hormone stimulates reabsorption of Ca2+ and excretion of phosphate The DCT serves as the major site where parathyroid hormone stimulates reabsorption of Ca2+ and excretion of phosphate

Reabsorption and Secretion in the Collecting Duct Aldosterone increases Na+ and water reabsorption as well as K+ secretion by the collecting ducts and late distal convoluted tubules Aldosterone increases Na+ and water reabsorption as well as K+ secretion by the collecting ducts and late distal convoluted tubules

Reabsorption and Secretion in the Collecting Duct Some cells secrete H+ into the filtrate and reabsorb HCO3- into the bloodstream Some cells secrete H+ into the filtrate and reabsorb HCO3- into the bloodstream

Reabsorption and Secretion in the Collecting Duct These cells help maintain body fluid pH by excreting excess H+ when the pH is too low or by reabsorbing less HCO3- when the pH is too high. These cells help maintain body fluid pH by excreting excess H+ when the pH is too low or by reabsorbing less HCO3- when the pH is too high.

Reabsorption and Secretion in the Collecting Duct ADH regulates water reabsorption by increasing permeability in the Collecting Duct and DCT ADH regulates water reabsorption by increasing permeability in the Collecting Duct and DCT

Production of Dilute and Concentrated Urine The rate at which water is lost from the body depends mainly on ADH The rate at which water is lost from the body depends mainly on ADH

Production of Dilute and Concentrated Urine When ADH level is very low, the kidneys produce dilute urine and excrete excess water When ADH level is very low, the kidneys produce dilute urine and excrete excess water

Production of Dilute and Concentrated Urine When ADH level is high, the kidneys secrete concentrated urine and conserve water When ADH level is high, the kidneys secrete concentrated urine and conserve water

Ureters Each of the two ureters connects the renal pelvis of one kidney to the urinary bladder Each of the two ureters connects the renal pelvis of one kidney to the urinary bladder

Urinary Bladder Located in the pelvic cavity posterior to the pubic symphysis Located in the pelvic cavity posterior to the pubic symphysis

Urinary Bladder In the floor of the urinary bladder is a small, smooth triangular area, the trigone. In the floor of the urinary bladder is a small, smooth triangular area, the trigone.

Urinary Bladder The ureters enter the urinary bladder near two posterior points in the triangle The ureters enter the urinary bladder near two posterior points in the triangle

Urinary Bladder The urethra drains the urinary bladder from the anterior point of the triangle The urethra drains the urinary bladder from the anterior point of the triangle

Urinary Bladder In the area around the opening to the urethra, the circular fibers of the muscularis form the internal urethral sphincter In the area around the opening to the urethra, the circular fibers of the muscularis form the internal urethral sphincter

Urinary Bladder The internal urethral sphincter contracts in response to sympathetics, and relaxes in response to parasympathetic stimulation The internal urethral sphincter contracts in response to sympathetics, and relaxes in response to parasympathetic stimulation

Urinary Bladder Below the internal sphincter is the external urethral sphincter, which is composed of skeletal muscle Below the internal sphincter is the external urethral sphincter, which is composed of skeletal muscle

Urethra A tube leading from the floor of the urinary bladder to the exterior A tube leading from the floor of the urinary bladder to the exterior

Urethra Functions to discharge urine from the body Functions to discharge urine from the body

Urethra The male urethra also serves as the duct for ejaculation of semen The male urethra also serves as the duct for ejaculation of semen

Incontinence A lack of voluntary control over urination A lack of voluntary control over urination

Retention Failure to void urine completely or normally Failure to void urine completely or normally