Lecture 13 Urinary System PDF

Urinary System Major Functions of the Urinary System 1. ​Excretion of organic wastes, such as urea, from body fluids 2. ​Elimination of these wastes into the external environment 3. ​Homeostatic regulation of volume and solute concentration of blood Organs of the Urinary System Two kidneys...

Urinary System Major Functions of the Urinary System 1. ​Excretion of organic wastes, such as urea, from body fluids 2. ​Elimination of these wastes into the external environment 3. ​Homeostatic regulation of volume and solute concentration of blood Organs of the Urinary System Two kidneys Produce urine that flows through urinary tract Urinary tract includes: Two ureters that transport urine from kidneys to bladder Urinary bladder stores urine Urethra transports urine from urinary bladder to exterior of body Elimination of urine is process called urination or micturition The Organs of the Urinary System. Organs of the Urinary System Kidney Produces urine Ureter Transports urine toward the urinary bladder Urinary bladder Temporarily stores urine before urination Urethra Conducts urine to exterior; in males, it also transports semen Anterior view Homeostatic Functions of the Urinary System In addition to removing organic wastes, urinary system also: Regulates blood volume and blood pressure Regulates concentration of plasma ions, such as sodium, potassium, chloride, and calcium Helps stabilize blood pH Conserves valuable nutrients like glucose and amino acids  Bozeman: Urinary System https://www.youtube.com/watch?v=H2VkW9L5QSU  Checkpoint Name the three major functions of the urinary system. Identify the organs of the urinary system.  Located on either side of vertebral column Between last thoracic and 3rd lumbar vertebrae Right kidney sits slightly lower Kidney Location than left Displaced somewhat by the liver Situated behind (dorsal to) peritoneum Position called retroperitoneal Adrenal gland located on superior surface of each kidney  Diaphragm 11th and Adrenal gland 12th ribs Left kidney Lumbar (L1) vertebra Right kidney Ureter Renal artery Inferior and vein vena cava The Position of the Kidneys. Iliac crest Aorta Urinary bladder Urethra This posterior a view of the trunk shows the positions of the kidneys and other organs of the urinary system. Kidney Positioning Kidneys held in place by: Overlying peritoneum Contact with adjacent organs Supportive connective tissue Fibrous capsule covers each kidney Capsule surrounded by adipose tissue Outer fibrous layer anchors to surrounding structures Damage to suspensory fibers of outer layer may result in displaced or floating kidney The Position of the Kidneys. Parietal Renal Renal peritoneum Stomach vein artery Aorta Hilum of Pancreas kidney Ureter Spleen Left kidney Vertebra Fibrous capsule Adipose tissue Inferior vena cava A superior b view of a section at the level indicated in part (a) shows the kidney’s retroperitoneal position. Superficial Anatomy of the Kidneys About 10 cm long, 5.5 cm wide, 3 cm Kidneys thick Indentation on one side is the hilum are bean Point of entry for renal artery and renal nerves shaped Point of exit for renal veins and ureter Fibrous Covers outer surface capsule Lines renal sinus, an internal cavity  Renal cortex is outer layer In contact with fibrous capsule Projects into medulla as renal columns Sectional Renal medulla is inner layer Contains 6–18 cone-shaped Anatomy of the renal pyramids Tip of each pyramid called renal Kidney papilla Projects into renal sinus Kidney lobe Contains pyramid, overlying cortex, and renal columns Sectional Anatomy of the Kidney (cont.) Urine production begins in nephrons in cortex of each kidney lobe About 1.25 million nephrons in each kidney Ducts within renal papilla drain urine into a cup-like structure called the minor calyx 4–5 minor calyces merge to form major calyx 2–3 major calyces combine to form large funnel-shaped chamber called the renal pelvis Renal pelvis connected to the ureter The Structure of the Kidney. Renal cortex Renal medulla Renal cortex Renal pyramids Renal medulla Renal Renal sinus sinus Major calyx Hilum Renal Major calyx pelvis Minor calyx Renal Hilum Renal pyramid pelvis Minor Renal Kidney lobe Ureter calyx papilla (dashed lines) Renal Renal columns Renal papilla columns Ureter Fibrous capsule Fibrous capsule a A diagrammatic view of a frontal section through the left kidney b A frontal section through the left kidney Blood Supply to the Kidney Kidneys receive 20–25 percent of total cardiac output (about 1200 mL of blood each minute) Blood flow starts with renal artery → Interlobar arteries (run between renal pyramids) → Arcuate arteries (along cortex-medulla boundary) → Cortical radiate arteries (or interlobular arteries) → Afferent arterioles (delivering blood to individual nephrons) → Glomerular capillaries → Efferent arterioles → Peritubular capillaries (surrounding nephron) → Cortical radiate veins (or interlobular veins) → Arcuate veins → Interlobar veins → Exits kidney by the renal veins The Blood Supply to the Kidneys. Medulla Adrenal artery Renal Cortical radiate artery veins Renal vein Cortical radiate arteries Interlobar arteries Interlobar Arcuate veins veins Arcuate arteries Thisasectional view of a kidney shows the major arteries and veins. Blood Flow from Peritubular Capillaries Blood from the peritubular capillaries follows two possible paths 1. In cortical nephrons (located almost entirely within renal cortex): Blood flows from peritubular capillaries directly into cortical radiate veins 2. In juxtamedullary nephrons: Peritubular capillaries are connected to the vasa recta Vasa recta run parallel to long nephron loops deep into the medulla Blood flows from vasa recta into cortical radiate veins The Blood Supply to the Kidneys. Nephrons Cortex Afferent arterioles Medulla This b enlarged view shows the circulation in a single kidney lobe.  Nephrons Efferent arteriole Cortex Afferent Peritubular arteriole capillaries Renal Afferent corpuscle arterioles Peritubular capillaries Collecting duct Medulla Nephron loop b This enlarged view c Further enlargement shows the shows the circulation circulation to a cortical nephron. in a single kidney lobe. Proximal Peritubular convoluted capillaries tubule (PCT) The Blood Supply to the Kidneys. Efferent Distal arteriole convoluted Glomerulus tubule (DCT) Afferent arteriole Vasa recta Collecting duct Nephron loop d Further enlargement shows the circulation to a juxtamedullary nephron.  Basic functional unit of the kidney The Nephron Consists of two main parts ​ enal R ​ enal R corpuscle tubule The Structure of the Kidney. Renal corpuscle Proximal convoluted tubule Distal convoluted tubule Collecting duct Nephron Papillary duct loop c enlarged view showing An the location and general structure of a nephron  Renal Corpuscle Spherical structure consisting of: Cup-shaped glomerular (Bowman’s) capsule containing: Network of capillaries known as glomerulus Blood flows into glomerulus from afferent arteriole and leaves by efferent arteriole Fluid and dissolved solutes forced out of glomerular capillaries and into surrounding capsular space Process called filtration Produces solution called filtrate Renal Tubule Filtrate flows into segments of renal tubule in order: Proximal convoluted tubule (PCT) Nephron loop, or loop of Henle Distal convoluted tubule (DCT) Filtrate at end called tubular fluid Each nephron empties into collecting duct Beginning of collecting system Collecting ducts drain into papillary ducts and into minor calyces Fluid at this point called urine  NEPHRON COLLECTING SYSTEM Proximal Convoluted Tubule Distal Convoluted Tubule Nephron and the Collecting System. Renal Corpuscle Renal tubule Efferent arteriole Collecting Duct Afferent arteriole Glomerulus Loop begins Loop ends Nephron Loop Thick Descending limb ascending limb Ascending limb Thin descending limb Papillary Duct KEY Flow of tubular fluid Solute reabsorption Minor Filtrate or secretion calyx Water reabsorption Variable solute Variable water reabsorption reabsorption or secretion © 2017 Pearson Education, Inc. Functions of the Nephron Corpuscle Produces filtrate by a passive process Filtrate includes valuable nutrients, ions, and water Tubules 1. Reabsorb useful molecules and ions from filtrate back into blood 2. Reabsorb >90 percent of water back into blood 3. Secrete any waste products missed by filtration process  Forms outer wall of renal corpuscle Encloses the glomerular capillaries The Glomerular Formed by two layers of cells Capsule separated by capsular space Outer layer, or capsular epithelium, forms wall of corpuscle Inner layer, or visceral epithelium, encloses glomerular capillaries Cells in this layer are called podocytes Have foot processes called pedicels that wrap around capillaries Renal Corpuscle. Glomerular capillary Glomerular Capsule Parietal epithelium Efferent arteriole Capsular space Visceral epithelium Juxtaglomerular (podocyte) Complex Macula densa Juxtaglomerular cells Proximal convoluted Distal convoluted tubule tubule Afferent arteriole a sectional view illustrates This the important structural features of a renal corpuscle. Filtration Membrane Nucleus Capillary Podocyte endothelium Podocyte Pedicels Pores Basement membrane Filtration slits Supporting cell RBC This cross section b Pedicels through a segment of the glomerulus A podocyte SEM × 2300 shows the Capsular space components of the This c colorized photomicrograph shows the filtration membrane Capsular glomerular surface, including individual of the nephron. epithelium podocytes and their processes. The Renal Corpuscle. Glomerular capillary Glomerular Capsule Parietal epithelium Efferent arteriole Capsular space Visceral epithelium Juxtaglomerular (podocyte) Complex Macula densa Juxtaglomerular cells Proximal convoluted Distal convoluted tubule tubule Afferent arteriole This a sectional view illustrates the important structural features of a renal corpuscle.  First segment of renal tubule The Majority of reabsorption occurs here Proximal Cells lining PCT reabsorb organic nutrients, plasma proteins, and ions Convolut from tubular fluid Substances are moved from tubule ed Tubule to interstitial fluid, or peritubular fluid Materials re-enter the blood Water follows by osmosis Reduces volume of tubular fluid The Nephron Loop Composed of descending limb and ascending limb Fluid in descending limb flows toward renal pelvis Epithelium permeable to water, not solutes Tubule makes 180-degree turn Fluid in ascending limb flows toward renal cortex Epithelium not permeable to water Actively transports sodium and chloride out of tubule Result is unusually high solute concentration in peritubular fluid of renal medulla Water from descending limb moves out by osmosis The Distal Convoluted Tubule Passes adjacent to afferent and efferent arterioles Site for three vital processes 1. Active secretion of ions, acids, drugs, and toxins 2. Selective reabsorption of sodium 3. Selective reabsorption of water  Combination of closely associated cells in the DCT and afferent arteriole Macula densa The Region of clustered cells in DCT closest to the glomerulus Juxtaglomerular cells Juxtaglomerular Unusual smooth muscle fibers in wall of afferent arteriole Complex Involved in regulation of blood volume and blood pressure Through secretion of erythropoietin and renin The Renal Corpuscle. Glomerular capillary Glomerular Capsule Parietal epithelium Efferent arteriole Capsular space Visceral epithelium Juxtaglomerular (podocyte) Complex Macula densa Juxtaglomerular cells Proximal convoluted Distal convoluted tubule tubule Afferent arteriole This a sectional view illustrates the important structural features of a renal corpuscle. The Collecting System Many DCTs empty into one collecting duct Several collecting ducts merge to form a papillary duct Papillary duct empties into minor calyx Functions of the collecting system Transports tubular fluid from nephron to renal pelvis Adjusts final fluid composition Determines final osmotic concentration of urine Determines final volume of urine © 2017 Pearson Education, Inc. Metabolic Wastes in Urine Must be excreted to maintain homeostasis Eliminated dissolved in urine, which requires water loss 1. ​Urea Most abundant organic waste Formed during breakdown of amino acids 2. ​Creatinine Generated in skeletal muscle tissue from breakdown of creatine phosphate 3. ​Uric acid Formed from breakdown and recycling of RNA The Ureters Paired muscular tubes conduct urine from kidneys to urinary bladder Each ureter begins at funnel-shaped renal pelvis Ends at posterior, slightly inferior bladder wall Slit-like ureteral openings prevent urine backflow Ureter wall contains three layers 1. Inner layer of transitional epithelium 2. Middle layer of smooth muscle that moves urine through tube by peristalsis 3. Outer connective tissue layer (continuous with renal capsule) Kidney Stones Also called calculi Solid substances made of calcium deposits, magnesium salts, or crystals of uric acid Can form within kidney, ureter, or urinary bladder Results in painful condition called nephrolithiasis Obstruct flow of urine May reduce or prevent filtration The Urinary Bladder Location and Size Hollow muscular organ that stores urine Size varies with amount of distention When full, can contain up to a liter of urine Held in place in pelvic cavity by peritoneal folds (umbilical ligaments) and connective tissue In males: Base lies between rectum and pubic symphysis In females: Sits inferior to the uterus and anterior to the vagina Internal Anatomy of the Urinary Bladder Base has triangular area called trigone, formed by: Two ureteral openings Urethral entrance Area surrounding urethral entrance is neck of bladder Contains involuntary internal urethral sphincter Bladder wall contains: Transitional epithelium Layers of smooth muscle called detrusor muscle Contraction of muscle expels contents into urethra The Urethra Extends from neck of urinary bladder to exterior of body Circular band of skeletal muscle surrounds urethra as passes through muscular floor of pelvic cavity External urethral sphincter under voluntary control In males: Extends 18–20 cm to external opening, or external urethral orifice, at tip of penis In females: Very short (2.5–3.0 cm) from bladder to external urethral orifice near anterior wall of vagina Organs for the Conduction and Storage of Urine. Left ureter Rectum Peritoneum Urinary bladder Pubic symphysis Prostate gland External urethral sphincter Urethra External urethral a Male orifice Organs for the Conduction and Storage of Urine. Rectum Right ureter Peritoneum Urinary Uterus bladder Pubic symphysis Internal urethral sphincter External urethral sphincter Vagina Urethra b Female Organs for the Conduction and Storage of Urine. Ureter Ligaments Detrusor muscle Ureteral openings Center of trigone Neck Internal urethral sphincter Prostate gland External urethral Urethra sphincter c Urinary bladder in male Crash Course: Urinary System part 1 https://www.youtube. com/watch?v=l128tW 1H5a8  Crash Course: Urinary System part 2 https://www.youtube.com/watch?v=DlqyyyvTI3k