The Urinary System Pages 720-734 24 PART 1 The Urinary System Pages 720-734

Organs of the Urinary System Kidneys Ureters Urinary bladder Urethra

Organs of the Urinary System Renal artery Renal hilum Renal vein Kidney Ureter Urinary bladder Urethra (b) Esophagus (cut) Inferior vena cava Adrenal gland Hepatic veins (cut) Iliac crest Aorta Rectum (cut) Uterus (a) Figure 24.1

Location and External Anatomy of Kidneys Located retroperitoneally Lateral to T12–L3 vertebrae Average kidney is 12 cm tall, 6 cm wide, 3 cm thick Hilum On concave surface Vessels and nerves enter and exit Fibrous capsule surrounds the kidney Perirenal fat—external to renal capsule Renal fascia—external to perirenal fat

Position of the Kidneys with in the Posterior Abdominal Wall Body wall Perirenal fat capsule Renal artery vein Inferior vena cava Aorta Fibrous capsule Renal fascia anterior posterior Supportive tissue layers Body of vertebra L2 Peritoneum Peritoneal cavity (organs removed) Anterior Posterior (a) (c) Vertebra L1 Erector spinae muscle in posterior abdominal wall Left kidney Left renal vein Right kidney Inferior vena cava Aorta Liver Duodenum Jejunum Figure 24.2a, c

Internal Gross Anatomy of the Kidneys Frontal section through the kidney Renal cortex Renal pyramids Renal pelvis Major calices Minor calices Gross vasculature Renal arteries branch into segmental arteries Segmental arteries branch into interlobar arteries Arcuate arteries branch from interlobar arteries

Internal Gross Anatomy of the Kidneys Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Ureter Minor calyx Renal column Renal pyramid in renal medulla Fibrous capsule hilum (a) Photograph of right kidney, frontal section (b) Diagrammatic view Figure 24.3

Summary of Blood Vessels Supplying the Kidney Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal artery Renal vein Renal pelvis Ureter Renal medulla Renal cortex (a) Frontal section, posterior view, illustrating major blood vessels Figure 24.4a

Summary of Blood Vessels Supplying the Kidney Aorta Renal artery Segmental artery Interlobar artery Arcuate artery Cortical radiate artery Afferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 24.9) Inferior vena cava Renal vein Interlobar vein Arcuate vein Cortical radiate vein Peritubular capillaries and vasa recta Efferent arteriole (b) Path of blood flow through renal blood vessels Figure 24.4b

Organs of the Urinary System Renal artery Renal hilum Renal vein Kidney Ureter Urinary bladder Urethra (b) Esophagus (cut) Inferior vena cava Adrenal gland Hepatic veins (cut) Iliac crest Aorta Rectum (cut) Uterus (a) Figure 24.1

Mechanisms of Urine Production Filtration Filtrate of blood leaves kidney capillaries Reabsorption Most nutrients, water, and essential ions reclaimed Secretion Active process of removing undesirable molecules

Basic Kidney Functions Cortical radiate artery Afferent arteriole Glomerular capillaries Efferent arteriole Glomerular capsule Rest of renal tubule containing filtrate Peritubular capillary To cortical radiate vein Urine Glomerular filtration Tubular resorption Tubular secretion Three major renal processes Figure 24.5

Nephron Structure Nephron is composed of Renal corpuscle Renal tubule

Renal Tubule Figure 24.7 Fenestrated endothelium of the glomerulus Microvilli Cortex Medulla Podocyte Basement membrane Mitochondria Highly infolded plasma Proximal convoluted tubule Distal Descending limb Nephron loop Ascending limb Glomerular capsule Renal corpuscle Glomerulus Thick segment Collecting duct Intercalated cell Principal cell Thin segment Proximal convoluted tubule cells Glomerular capsule: parietal layer Glomerular capsule: visceral layer Distal convoluted tubule cells Nephron loop (thin-segment) cells Collecting duct cells Renal cortex Renal medulla Renal pelvis Ureter Kidney Figure 24.7

Renal corpuscle—first part of nephron The Nephron Renal corpuscle—first part of nephron Glomerulus and glomerular capsule Glomerulus—tuft of capillaries Capillaries of glomerulus are fenestrated Glomerular (Bowman’s) capsule Parietal layer—simple squamous epithelium Visceral layer—consists of podocytes

The filtration membrane Filter that lies between blood in the glomerulus and capsular space Consists of three layers Endothelium of the capillary Slits between foot processes of podocytes Basement membrane

Basement membrane and slit diaphragm Filtration Membrane Basement membrane and slit diaphragm Hold back most proteins Allow through Water Ions Glucose Amino acids Urea

Renal Corpuscle and the Filtration Membrane Glomerular capillary covered by podocyte- containing visceral layer of glomerular capsule Proximal convoluted tubule Parietal layer of glomerular capsule Afferent arteriole Glomerular capsular space Efferent (a) Renal corpuscle (b) Glomerular capillary surrounded by podocytes Glomerular capillary endothelium (podocyte covering and basement membrane removed) Fenestrations (pores) Podocyte cell body Foot processes of podocyte Filtration slits Cytoplasmic extensions of podocytes Figure 24.6a, b

Renal Corpuscle and the Filtration Membrane (d) Three parts of the filtration membrane Fenestration (pore) Filtrate in capsular space Foot processes of podocyte Filtration slit Slit diaphragm Basement membrane Capillary endothelium Capillary Filtration membrane Foot processes of podocyte of glomerular capsule Plasma Figure 24.6d

Filtrate proceeds to renal tubules from glomerulus Proximal convoluted tubule Nephron loop Descending limb Thin segment Thick segment Distal convoluted tubule Collecting ducts Receive urine from several nephrons Play an important role in conserving body fluids

Renal Tubule Figure 24.7 Fenestrated endothelium of the glomerulus Microvilli Cortex Medulla Podocyte Basement membrane Mitochondria Highly infolded plasma Proximal convoluted tubule Distal Descending limb Nephron loop Ascending limb Glomerular capsule Renal corpuscle Glomerulus Thick segment Collecting duct Intercalated cell Principal cell Thin segment Proximal convoluted tubule cells Glomerular capsule: parietal layer Glomerular capsule: visceral layer Distal convoluted tubule cells Nephron loop (thin-segment) cells Collecting duct cells Renal cortex Renal medulla Renal pelvis Ureter Kidney Figure 24.7

Figure 24.8a Histology of the nephron. Distal convoluted tubules (clear lumens) Renal corpuscle Squamous epithelium of parietal layer of glomerular capsule Glomerular capsular space Glomerulus Proximal convoluted tubules (fuzzy lumens due to long microilli) Photomicrograph of renal cortical tissue (230 )

Micrograph through the Renal Medulla (b) Photomicrograph through the renal medulla (215X) Collecting ducts Thin segments of nephron loop Vasa recta with blood cells within Figure 24.8b

Juxtamedullary nephrons Classes of Nephron Cortical nephrons 85% of nephrons Juxtamedullary nephrons 15% of nephrons Contribute to kidney’s ability to concentrate urine

Classes of Nephron Figure 24.9 Corticomedullary junction Peritubular capillary bed Efferent arteriole Afferent Glomerulus (b) Ureter Renal pelvis Kidney Cortex Medulla (a) Cortical radiate vein Cortical radiate artery Afferent arteriole Collecting duct Distal convoluted tubule Vasa recta Nephron loop Arcuate artery Arcuate vein capillaries Glomerular capillaries (glomerulus) Glomerular (Bowman’s) capsule corpuscle Ascending or thick limb of the nephron loop Descending or thin limb of Proximal convoluted tubule • Has short nephron loop and glomerulus further from the corticomedullary junction • Efferent arteriole supplies peritubular capillaries Cortical nephron • Has long nephron loop and glomerulus closer to the corticomedullary junction • Efferent arteriole supplies vasa recta Juxtamedullary nephron Figure 24.9

Blood Vessels Associated with Nephrons Nephrons associate closely with two capillary beds Glomeruli Peritubular capillaries in cortical nephrons or vasa recta in juxtamedullary nephrons

Blood Vessels Associated with Nephrons Glomeruli Produce filtrate that becomes urine Fed and drained by arterioles Afferent and efferent arteriole Efferent arteriole has a smaller diameter than afferent arteriole Generate 1 liter of fluid every 8 minutes 99% of filtrate is resorbed by tubules

Blood Vessels Associated with Nephrons Peritubular capillaries Arise from the efferent arterioles Are adapted for absorption Low-pressure, porous capillaries All molecules secreted by nephrons into urine are from peritubular capillaries

Classes of Nephron Figure 24.9 Corticomedullary junction Peritubular capillary bed Efferent arteriole Afferent Glomerulus (b) Ureter Renal pelvis Kidney Cortex Medulla (a) Cortical radiate vein Cortical radiate artery Afferent arteriole Collecting duct Distal convoluted tubule Vasa recta Nephron loop Arcuate artery Arcuate vein capillaries Glomerular capillaries (glomerulus) Glomerular (Bowman’s) capsule corpuscle Ascending or thick limb of the nephron loop Descending or thin limb of Proximal convoluted tubule • Has short nephron loop and glomerulus further from the corticomedullary junction • Efferent arteriole supplies peritubular capillaries Cortical nephron • Has long nephron loop and glomerulus closer to the corticomedullary junction • Efferent arteriole supplies vasa recta Juxtamedullary nephron Figure 24.9

Blood Vessels Associated with Nephrons Vasa recta Continue from efferent arterioles of juxtamedullary nephrons Are thin-walled looping vessels Descend into the medulla Are part of the kidney’s urine concentrating mechanism

Juxtaglomerular Apparatus Functions in regulating blood pressure An area of specialized contact between terminal end of the ascending limb and afferent arteriole Granular cells—modified smooth muscle cells with secretory granules Contain the hormone renin Renin—secreted in response to falling BP in afferent arteriole

Juxtaglomerular Apparatus Glomerulus Glomerular capsule Afferent arteriole Efferent Red blood cell Podocyte cell body (visceral layer) Foot processes of podocytes Parietal layer of glomerular capsule Proximal tubule cell Lumens of glomerular capillaries Endothelial cell capillary Macula densa cells of the ascending limb of nephron loop Granular cells Extraglomerular mesangial cells Afferent arteriole Capsular space Renal corpuscle Juxtaglomerular apparatus Mesangial cells between capillaries Figure 24.10

Juxtaglomerular Apparatus Macula densa—end of nephron loop Adjacent to granular cells Tall, closely packed epithelial cells Monitor solute concentration in the filtrate Signal granular cells to secrete renin Initiates renin-angiotensin mechanism

Juxtaglomerular Apparatus Mesangial cells Located around base of the glomerulus Regulated blood flow within the glomerulus Extraglomerular mesangial cells Interact with macula densa and granular cells Help regulate blood pressure

Juxtaglomerular Apparatus Glomerulus Glomerular capsule Afferent arteriole Efferent Red blood cell Podocyte cell body (visceral layer) Foot processes of podocytes Parietal layer of glomerular capsule Proximal tubule cell Lumens of glomerular capillaries Endothelial cell capillary Macula densa cells of the ascending limb of nephron loop Granular cells Extraglomerular mesangial cells Afferent arteriole Capsular space Renal corpuscle Juxtaglomerular apparatus Mesangial cells between capillaries Figure 24.10

Carry urine from the kidneys to the urinary bladder Ureters Carry urine from the kidneys to the urinary bladder Oblique entry into bladder prevents backflow of urine Histology of ureter Mucosa—transitional epithelium Muscularis—two layers Inner longitudinal layer Outer circular layer Adventitia—typical connective tissue

Structure of the Urinary Bladder and Urethra Ureter Trigone of bladder Prostate Membranous urethra Prostatic urethra Peritoneum Rugae Detrusor muscle Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis Ureteric orifices Adventitia (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Figure 24.14

Ureters Kidney Ureter Renal pelvis Urinary bladder

Microscopic Structure of the Ureter Lumen Adventitia Circular layer Longitudinal Transitional epithelium Lamina propria Mucosa Muscularis Figure 24.11

A collapsible muscular sac Stores and expels urine Urinary Bladder A collapsible muscular sac Stores and expels urine Full bladder—spherical Expands into the abdominal cavity Empty bladder—lies entirely within the pelvis

Urachus—closed remnant of the allantois Prostate gland Urinary Bladder Urachus—closed remnant of the allantois Prostate gland In males Lies directly inferior to the bladder Surrounds the urethra

Urinary Bladder Ureter not illustrated in (b) Uterus Urinary bladder Ductus deferens Pubic symphysis Prostate Vagina Urethra (a) Sagittal section through male pelvis, urinary bladder shown in lateral view (b) Sagittal section through female pelvis Urachus Figure 24.12

Urinary bladder is composed of three layers Mucosa—transitional epithelium Thick muscular layer—detrusor muscle Fibrous adventitia

Figure 24.13 Histology of the bladder. Lumen of the bladder Transitional epithelium Lamina propria Muscular layer (detrusor) Transitional epithelium Basement membrane Lamina propria Micrograph of the bladder wall (25 ) Epithelium lining the lumen of the bladder (285 )

Structure of the Urinary Bladder and Urethra Ureter Trigone of bladder Prostate Membranous urethra Prostatic urethra Peritoneum Rugae Detrusor muscle Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis Ureteric orifices Adventitia (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Figure 24.14

Structure of the Urinary Bladder and Urethra Ureter Trigone Peritoneum Rugae Detrusor muscle Bladder neck Internal urethral sphincter External urethral Urogenital diaphragm Urethra orifice Ureteric orifices (b) Female Figure 24.14

Urethra Epithelium of urethra Transitional epithelium At the proximal end (near the bladder) Stratified and pseudostratified columnar—mid urethra (in males) Stratified squamous epithelium At the distal end (near the urethral opening)

Internal urethral sphincter Involuntary smooth muscle External urethral sphincter Voluntarily inhibits urination Relaxes when one urinates

In males—20 cm in length; three named regions Urethra In females Length of 3–4 cm In males—20 cm in length; three named regions Prostatic urethra Passes through the prostate gland Membranous urethra Through the urogenital diaphragm Spongy (penile) urethra Passes through the length of the penis

Structure of the Urinary Bladder and Urethra Ureter Trigone of bladder Prostate Membranous urethra Prostatic urethra Peritoneum Rugae Detrusor muscle Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis Ureteric orifices Adventitia (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Figure 24.14

Structure of the Urinary Bladder and Urethra Ureter Trigone Peritoneum Rugae Detrusor muscle Bladder neck Internal urethral sphincter External urethral Urogenital diaphragm Urethra orifice Ureteric orifices (b) Female Figure 24.14