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26The Urinary System

PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska

© 2012 Pearson Education, Inc.

Introduction

The urinary system includes the kidneys, the ureters, the urinary bladder, and the urethra. Performs vital excretory functions:

Regulating plasma concentrations of ions Regulating blood volume and blood pressure by

adjusting the volume of water lost in the urine, releasing erythropoietin, and releasing renin

Contributing to the stabilization of blood pH Conserving valuable nutrients Eliminating organic waste products Synthesizing calcitriol. Assisting the liver in detoxifying poisons

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Introduction

• The urinary system consists of:• Kidneys

• And the associated nephrons

• Ureters• Urinary bladder• Urethra

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Figure 26.1a An Introduction to the Urinary System

Anterior view showing thecomponents of the urinary system

Urethra

Urinary bladder

Ureter

Kidney

Produces urine

Transports urinetoward theurinary bladder

Temporarily storesurine prior to elimination

Conducts urine toexterior; in males,transports semenas well

Suprarenal gland

Inferiorvena cava

Aorta

Renal arteryand vein

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The Kidneys

Urine-producing organ of the urinary system Two kidneys in the retroperitoneal area Left kidney is higher than the right kidneyOn top of each kidney a suprarenal gland is sitting. Contain millions of tiny nephrons

Blood is provided to the nephrones for filtration through afferent arterioles.The filtrate passes through the renal tubules and final product (urine) reaches the collecting duct. The urine leaves the collecting ducts towards minor and major calyces. Urine from major calyces enter into the renal pelvis, before leaves the kidney through ureters to the bladder.

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Figure 26.1c An Introduction to the Urinary System

Diagrammatic cross section, as viewed from above, atthe level indicated in part (b)

Adiposetissue

Renal artery

Renal vein

Aorta

Inferiorvena cava

Spinalcord

Psoasmajor

Quadratuslumborum

Pararenalfat

Perinephricfat

Posteriorrenal fascia

Fibrouscapsule

Leftkidney

Anteriorrenal

fascia

Parietalperitoneum

Externaloblique

Stomach

Spleen

Ureter

Pancreas

Vertebra

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Figure 26.2a The Urinary System in Gross Dissection

Diagrammatic anterior view of the abdominopelvic cavity showingthe kidneys, suprarenal glands, ureters, urinary bladder, and bloodsupply to the kidneys

Urinary bladder

Rectum (cut)

Peritoneum(cut)

Psoas majormuscle

Iliacus muscle

Quadratuslumborum

muscle

Hilum

Right kidney

Right suprarenalgland

Celiac trunk

Inferior vena cava

Diaphragm

Left kidney

Left renal artery

Left renal vein

Left ureter

Superiormesenteric

artery

Abdominalaorta

Left commoniliac artery

Gonadal arteryand vein

Left suprarenal gland

Esophagus (cut)

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Figure 26.3a Structure of the Kidney

Frontal section through the left kidney showingmajor structures. The outlines of a renal lobe and arenal pyramid are indicated by dotted lines.

Renal sinus

Inner layer offibrous capsule

Adipose tissuein renal sinus

Renal pelvis

Hilum

Renal papilla

Ureter

Major calyx

Cortex

Medulla

Renalpyramid

Connection tominor calyx

Minorcalyx

Renal lobe

Renal columns

Outer layer offibrous capsule

Medulla

Hilum

Ureter

Outer layer offibrous capsule

Renalpyramids

Inner layer offibrous capsule

Renal sinus

Renal pelvis

Major calyx

Minor calyx

Renal papilla

Renal lobe

Fibrous capsule

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Figure 26.4a Blood Supply to the Kidneys

Sectional view showing major arteries andveins. Compare with Figures 26.3 and 26.8.

Arcuate veins

Arcuate arteries

Interlobarveins

Renalvein

Renalartery

Suprarenalartery

Segmentalartery

Interlobararteries

Corticalradiate

arteries

Interlobularveins

© 2012 Pearson Education, Inc.

© 2012 Pearson Education, Inc.

The Kidneys

• Structure and Function of the Nephron• Waste (glomerular filtrate) material leaves the

glomerular capillaries and enters:• Glomerular capsule• Proximal convoluted tubule (PCT)• Nephron loop• Distal convoluted tubule (DCT)

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The Kidneys

• Structure and Function of the Nephron• Filtrate enters the DCT of several nephrons and

empties into a common tube called the collecting duct

• Filtrate enters the papillary duct• Minor calyx• Major calyx• Ureter• Urinary bladder• Urethra

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Figure 26.7a Histology of the Nephron

Orientation of cortical and juxtamedullarynephrons

Corticalnephron

Juxtamedullarynephron

Proximal convolutedtubule

Renal corpuscle

Distal convolutedtubule

Connecting tubules

Nephronloop

Thin descendinglimb

Thick ascendinglimb

Collecting duct

Papillary duct

Renal papilla

Minor calyx

Medulla

Cortex

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Figure 26.7ac Histology of the Nephron

Orientation of cortical and juxtamedullarynephrons

Corticalnephron

Juxtamedullarynephron

Proximal convolutedtubule

Renal corpuscle

Distal convolutedtubule

Connecting tubules

Nephronloop

Thin descendinglimb

Thick ascendinglimb

Collecting duct

Papillary duct

Renal papilla

Minor calyx

Medulla

Cortex

The renal corpuscle

LM 140Renal corpuscle

Visceral epithelium

Parietal epithelium

Capsular space

Distal convolutedtubule

Proximal convolutedtubule

Glomerulus

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Figure 26.6 A Typical NephronNEPHRON

PROXIMAL CONVOLUTED TUBULE

DISTAL CONVOLUTED TUBULE

RENAL CORPUSCLE

NEPHRON LOOP

PAPILLARY DUCT

CONNECTING TUBULESAND COLLECTING DUCT

COLLECTING SYSTEM

Nucleus

Microvilli

Mitochondria

Reabsorption of water, ions, andall organic nutrients

Secretion ofions, acids,

drugs, toxins

Variable reabsorption of water,sodium ions, and calcium ions

(under hormonal control)

Renal tubule

Efferent arteriole

Afferent arteriole

Ascendinglimb ofloop ends

Ascendinglimb

Descendinglimb of

loop ends

Descendinglimb

Parietal (capsular)epithelium

Capsular space

Visceral(glomerular)

epithelium

Capillaries ofglomerulus

Production of filtrate

Further reabsorption of water (descending limb) andboth sodium and chloride ions (ascending limb)

Thindescending

limb

Thickascending

limb

Minorcalyx

Delivery ofurine to

minor calyx

Variable reabsorptionof water and

reabsorption orsecretion of

sodium, potassium,hydrogen, and

bicarbonate ions

Collecting duct

Connecting tubules

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Figure 26.8c The Renal Corpuscle

The renal corpuscle.Arrows show thepathway of bloodflow.

Distal convolutedtubule

Efferentarteriole

Juxtaglomerularcomplex

Juxtaglomerularcells

Extraglomerularmesangial cells

Macula densa

Afferentarteriole

Glomerularcapillary

Capsular space

Proximalconvoluted

tubule

Tubularpole

Parietalepithelium

Visceralepithelium(podocyte)

Glomerular capsule

Vascular pole

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© 2012 Pearson Education, Inc.

Structures for Urine Transport, Storage, and Elimination

Ureters Urinary bladder

Contains detrusor muscle, which compresses the urinary bladder to eliminate the urine.Voluntary urination needs compression of detrusor muscle and relaxation of external sphincter.

UrethraThere are significant differences between the male and female urethra.The parts of urethra in male:

Prostatic urethra Membranous urethra Penile urethra

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Figure 26.10 Organs Responsible for the Conduction and Storage of Urine

Anatomy of the urinarybladder in a male

The male urinary bladder and accessory reproductivestructures as seen in posterior view

Position of the ureter, urinarybladder, and urethra in the female

Position of the ureter, urinarybladder, and urethra in the male

Left ureter RectumPeritoneum

Pubicsymphysis

Prostategland

Urogenitaldiaphragm

Urethra[see part c]

Externalurethral

orifice

Spongyurethra

Externalurethral

sphincter

Urinarybladder

Vestibule

Right ureter

Urinarybladder

Internal urethralsphincter

Urethra

External urethralsphincter (in

urogenital diaphragm)

Pubicsymphysis

Vagina

Peritoneum

Uterus

Rectum

Peritoneum

Ductus deferens

Seminalgland

Posterior surfaceof prostate gland

Right ureter

Base ofurinarybladder

Prostaticurethra

Trigone

Center oftrigone

Neck ofurinarybladder

Prostategland

Prostaticurethra

Membranousurethra

External urethralsphincter (in urogenital

diaphragm)

Internal urethralsphincter

Ureteralopenings

Rugae

Ureter

Detrusormuscle

Lateralumbilicalligament

Median umbilicalligament (urachus)

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Aging and the Urinary System

A decline in the number of functional nephrons A reduction in glomerular filtration Reduced sensitivity to ADH Problems with the micturition reflex related to the following factors:

Loss of tone in sphincter muscles leading to incontinence

Strokes, Alzheimer’s disease, or other CNS problems impair ability to control micturition

Urinary retention may develop in men whose prostrate glands are enlarged