Chapt20 urinary system by Michael Walls

Chapter 20 Lecture PowerPoint

Hole’s Human Anatomy and Physiology Twelfth Edition

Shier Butler Lewis Chapter 20 Urinary System

20.1: Introduction • A major part of homeostasis is maintaining the composition, pH, and volume of body fluids within normal limits • The urinary system removes metabolic wastes and substances in excess, including foreign substances like drugs and their metabolites that may be toxic • It consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra

Kidney

Renal vein Hilum

Renal artery Inferior vena cava Abdominal aorta

Ureters

Urinary bladder Urethra

20.2: Kidneys • A kidney is a reddish brown, bean-shaped organ with a smooth surface • In the adult it is about 12 centimeters long, 6 centimeters wide, and 3 centimeters thick • It is enclosed in a tough, fibrous capsule

Location of the Kidneys Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Kidney Adipose tissue Parietal peritoneum

Spleen

Inferior vena cava

Aorta Small intestine Large intestine

Pancreas

Stomach (a)

Adrenal gland Twelfth rib

Liver

Kidney

Parietal peritoneum

Renal fascia

Hip bone (cut)

Large intestine

6 (b)

Kidney Structure Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Renal capsule Renal cortex

Renal medulla

Renal corpuscle Nephrons

Renal cortex

Minor calyx Major calyx Renal medulla

Renal sinus Renal column Fat in renal sinus

Collecting duct Papilla

Renal pelvis

Minor calyx

Renal tubule

Renal papilla (b)

(c)

Renal pyramid Ureter

(a)

Inferior vena cava

Abdominal aorta

Suprarenal artery

Suprarenal vein

Adrenal gland

Renal artery Renal column

Renal capsule Renal pelvis Renal papilla

Renal vein

Renal medulla

Hilum Renal pyramid

Renal cortex Ureter Minor calyx

Function of the Kidneys • The main function of the kidneys is to regulate the volume, composition, and pH of body fluids • The kidneys remove metabolic wastes from the blood and excrete them to the outside of the body, including nitrogenous and sulfur-containing products of protein metabolism • The kidneys also help control the rate of red blood cell production, regulate blood pressure, and regulate calcium ion absorption

20.1 Clinical Application Chronic Kidney Failure

Cortical radiate artery and vein

Proximal Cortex convoluted tubule

Arcuate vein and artery

Medulla Efferent

Cortical radiate artery and vein

Afferent arteriole arteriole

Interlobar vein and artery

Distal convoluted tubule

Peritubular capillary

Renal artery Renal vein Renal pelvis

Efferent Afferent arteriole arteriole Glomerulus (a)

Ureter

Peritubular capillary

(a)

Renal tubules

Glomerulus (b)

Glomerular capsule

(a) : Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, by R.G. Kessel and R.H. Kardon. © 1979 W.H. Freeman and Company (b) : Courtesy of R.B. Wilson MD, Eppeley Institute for Research in Cancer, University of Nebraska Medical Center

(b) b: © L.V. Bergman/The Bergman Collection

Afferent arteriole

Efferent arteriole

Slit pore

Pedicel

Primary process of podocyte

Blood flow Blood flow

Glomerular capsule Parietal layer of glomerular capsule

Slit pore

Glomerulus

Proximal convoluted tubule

Visceral layer of glomerular capsule Pedicel

Primary process of podocyte

Glomerular capsule

Cortical radiate artery Cortical radiate vein

Proximal convoluted tubule

Collecting ducts

Glomerulus

Afferent arteriole

Efferent arteriole

Distal convoluted tubule

Epithelial cell

Renal cortex Renal tubules

Glomerular Glomerulus capsule Renal corpuscle

To renal vein

Descending limb Ascending limb

Blood vessel (a)

From renal artery

Peritubular capillary

Nephron loop

(b)

a: © Biophoto Associates/Photo Researchers, Inc., b: © Manfred Kage/Peter Arnold

Renal medulla

Collecting duct

Juxtaglomerular Apparatus Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Afferent Glomerular arteriole capsule Glomerulus Juxtaglomerular apparatus

Distal convoluted tubule Efferent arteriole

Proximal convoluted tubule

Glomerulus Podocyte Afferent arteriole

Nephron loop

(a)

Juxtaglomerular cells Macula densa

Glomerular capsule

Juxtaglomerular apparatus

Ascending limb of nephron loop

Efferent arteriole (b)

Cortical and Juxtamedullary Nephrons Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cortical nephron

Renal cortex

Juxtamedullary nephron

Renal medulla

Collecting duct

Blood Supply of a Nephron Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Glomerular capsule

Renal artery

Cortical radiate artery and vein

Interlobar artery

Proximal convoluted tubule Glomerulus Efferent arteriole

Arcuate artery

Afferent arteriole Distal convoluted tubule

Cortical radiate artery

Afferent arteriole

Peritubular capillaries

Glomerular capillaries

Efferent arteriole

Vasa recta Peritubular capillaries

Cortical radiate vein

Arcuate vein

Collecting duct

Interlobar vein

Nephron loop Renal vein

20.2 Clinical Application Glomerulonephritis

20.3: Urine Formation • The main function of the nephrons and collecting ducts is to control the composition of body fluids and remove wastes from the blood, the product being urine • Urine contains wastes, excess water, and electrolytes • Urine is the final product of the processes of: • Glomerular filtration • Tubular reabsorption • Tubular secretion 18

Urine Formation Copyright ÂŠ The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Arteriole

Venule Net reabsorption

Blood flow

Net filtration Interstitial fluid (a) In most systemic capillaries, filtration predominates at the arteriolar end and osmotic reabsorption predominates at the venular end.

Peritubular capillaries Afferent arteriole

Glomerular capillaries

Efferent arteriole

Venule Blood flow

Glomerular filtration Filtered fluid

Tubular reabsorption

Tubular secretion Tubular fluid

Urine

Renal tubule (b) In the kidneys, the glomerular capillaries are specialized for filtration. The renal tubule is specialized to control movements of substances back into the blood of the peritubular capillaries (tubular reabsorption) or from the blood into the renal tubule (tubular secretion).

Glomerulus

Proximal convoluted tubule

Afferent arteriole

Capillary endothelium Podocyte

Glomerular filtrate

Glomerular capsule

Fenestrae

Blood flow

Podocyte Efferent arteriole

20 (a)

(b)

Plasma, Glomerular Filtrate, and Urine Components

Filtrate Pressure • The main force that moves substances by filtration through the glomerular capillary wall is hydrostatic pressure of the blood inside Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Hydrostatic pressure of blood Glomerular hydrostatic pressure

Capsular hydrostatic pressure

Plasma colloid osmotic pressure

Net Outward Pressure Outward force, glomerular hydrostatic pressure = Inward force of plasma colloid osmotic pressure = Inward force of capsular hydrostatic pressure = Net filtration pressure =

+60 mm –32 mm –18 mm +10 mm

Filtrate Rate • Glomerular filtration rate (GFR) is directly proportional to the net filtration pressure Net filtration pressure = force favoring filtration (glomerular capillary hydrostatic pressure)

–

170 160 150 140 130 120 110 Liters

• Normally the glomerular net filtration pressure is positive causing filtration • The forces responsible include hydrostatic pressure and osmotic pressure of plasma and the hydrostatic pressure of the fluid in the glomerular capsule

180 Liters

180

100 90 80 70 60 50 40 30 20 10

0.6 – 2.5 Liters

Urine

Glomerular filtrate (a)

(b)

Control of Filtrate Rate • GFR remains relatively constant through a process called autoregulation • Certain conditions override autoregulation, including when GFR increases • Primarily three mechanisms are responsible for keeping the GFR constant: • Autoregulation • Increased sympathetic impulses that decrease GFR by causing afferent arterioles to constrict • The hormone-like renin-angiotensin system • There also is the hormone atrial natriuretic peptide (ANP) affects sodium causing an increase in GFR 24

Lung capillaries Kidney Liver

Renin

Angiotensinogen

Angiotensinconverting enzyme Angiotensin I

Angiotensin II

Bloodstream

Release into bloodstream Stimulation

• Vasoconstriction • Increased aldosterone secretion • Increased ADH secretion • Increased thirst

Tubular Reabsorption • Tubular reabsorption • Substances move from the renal tubules into the interstitial fluid where they then diffuse into the peritubular capillaries • The proximal convoluted tubule reabsorbs (70%): • Glucose, water, urea, proteins, and creatine • Amino, lactic, citric, and uric acids • Phosphate, sulfate, calcium, potassium, and sodium ions

Blood flow

Blood flow Afferent arteriole Glomerular capsule

Efferent arteriole

Glomerulus

Afferent arteriole Glomerular capsule

Efferent arteriole

Glomerulus Glomerular filtrate

Glomerular filtrate

Peritubular capillary Tubular reabsorption

Peritubular capillary

Tubular secretion Renal tubule

Renal tubule Blood flow (a)

Blood flow (b)

Blood flow Glomerulus Glomerular capsule

Blood flow

Glomerular filtrate

Proximal convoluted tubule

Na+ Na+

Cl–

– – – –

PO4–3 HCO3– N+ Cl–

Sodium ions are reabsorbed by active transport

Negatively charged ions are attracted to positively charged ions

As concentration of ions (solute) increases in plasma, osmotic pressure increases

Water moves from proximal tubule to capillary by osmosis

+ –+ –+ +– –+

Na+ H2O H2O

Isotonic tubular fluid

–+ –+ ++ – + +– – – ++ – –

Peritubular capillary Blood flow

20.3 Clinical Application The Nephrotic Syndrome

Tubular Secretion • Tubular secretion • Substances move from the plasma of the peritubular capillaries into the fluid of the renal tubules • Active transport mechanisms function here • Secretion of substances such as drugs and ions

Peritubular capillary Blood flow K+ or H+

Tubular reabsorption

Na+

Na+ Na+

Tubular secretion

Na+

K+

Na+ Na+

Na+

H+

K+

Na+

Na+ Tubular fluid

H+

Distal convoluted tubule

Na+

K+

Na+

Na+ Ascending limb of nephron loop

Collecting duct

Regulation of Urine Concentration and Volume • Hormones such as aldosterone and ANP affect the solute concentration of urine, particularly sodium • The ability of the kidneys to maintain the internal environment rests in a large part on their ability to concentrate urine by reabsorbing large volumes of water • The distal convoluted tubule and the collecting duct are impermeable to water, so water may be excreted as dilute urine • If ADH is present, these segments become permeable, and water is reabsorbed by osmosis into the extremely hypertonic medullary interstitial fluid • A countercurrent mechanism in the nephron loops (the descending and the ascending limbs) ensures that the medullary interstitial fluid becomes hypertonic • This mechanism is known as the countercurrent multiplier • The vasa recta also contributes as a countercurrent mechanism 33

Distal convoluted tubule Medullary interstitial fluid

H2O

H2O H2O

Hypertonic interstitial fluid

Collecting duct

Hypertonic interstitial fluid H2O

Dilute urine (a)

low ADH levels

Medullary interstitial fluid

H2O

H2O Collecting duct

Concentrated urine (b)

high ADH levels

H2O

Na+ Cl–

Salty Increasing NaCl concentration 2 Cl– Na+

Isotonic fluid H2O

H2O Descending limb (permeable to water)

(a)

H2O

Cl– Na+ Cl– Na+

H2O

Hypotonic fluid

More salty

Thick ascending limb (impermeable to water) 3 Medullary interstitial fluid

Hypertonic fluid

Na+ Cl–

H2O

Na+ Cl– Even more salty

(b)

Blood flow

Increasing NaCl concentration

NaCl

Medullary interstitial fluid

NaCl

NaCl NaCl

NaCl

Vasa recta

Urea and Uric Acid Excretion • Urea: • A by-product of amino acid catabolism • The plasma concentration reflects the amount or protein in diet • It enters the renal tubules through glomerular filtration • It contributes to the reabsorption of water from the collecting duct • About 80% is recycled • Uric acid: • Is a product of nucleic acid metabolism • It enters the renal tubules through glomerular filtration • Most reabsorption occurs by active transport • About 10% is secreted and excreted 39

Urine Composition • Urine composition reflects the volumes of water and solutes that the kidneys must eliminate from the body or retain in the internal environment to maintain homeostasis • It varies from time to time due to dietary intake and physical activity, but is: • About 95% water • Usually contains urea, uric acid, and creatinine • May contain trace amounts of amino acids and varying amounts of electrolytes • Volume varies with fluid intake and environmental factors

Renal Clearance • This is the rate at which a chemical is removed from the plasma • It indicates kidney efficiency • Tests of renal clearance: • Inulin clearance test • Creatinine clearance test • Para-aminohippuric acid (PAH) test • These tests of renal clearance are used to calculate the GFR (glomerular filtration rate)

20.4: Elimination of Urine • After forming along the nephrons, urine: • Passes the collecting ducts to: • Openings of the renal papillae: • Enters the minor and major calyces: • Passes through the renal pelvis: • Enters into the ureters: • Enters into the urinary bladder: •The urethra carries the urine out of the body

Ureters • The ureters: • Each is about 25 centimeters long • Extends downward posterior to the parietal peritoneum • Runs parallel to vertebral column • Join the urinary bladder in the pelvic cavity • The wall of ureter has three layers: • The inner mucous coat • The middle muscular coat • The outer fibrous coat

Mucous coat Lumen Muscular coat

Urinary Bladder • The urinary bladder is a hollow, distensible, muscular organ located within the pelvic cavity, posterior to the symphysis pubis and inferior to the parietal peritoneum • It contacts the anterior walls of the uterus and vagina in the female, and lies posteriorly against the rectum in the male • The openings for the ureters is the area of trigone • It has four layers: inner mucous coat, a submucous coat, a muscular coat, and an outer serous coat • Smooth muscle fibers comprise the detrusor muscle which is the muscle of the bladder wall 45

Ureter

Abdominal wall Parietal peritoneum Urinary bladder Symphysis pubis Prostate gland Urethra

Rectum Rectum

(a)

(b)

Serous coat

Ureter

Urinary bladder Ureter

Detrusor muscle Submucous coat

Ductus (vas) deferens

Mucous coat Openings of the ureters Seminal vesicle

Trigone Neck

Prostate gland Internal urethral sphincter Prostate gland Urethra Region of external urethral sphincter (a)

Urethra (b)

Muscular coat

Mucous coat

Submucous coat

Lumen

Ureter

Urinary bladder

Trigone

Urethra

External urethral orifice (a)

Ureter

Urinary bladder Trigone

Prostatic urethra Membranous urethra

Penile urethra

External urethral orifice (b)

Prostate gland Bulbourethral gland

Penis

Urethra • The urethra is a tube that conveys urine from the urinary bladder to the outside of the body • Its wall is lined with a mucous membrane and it has a thick layer of longitudinal smooth muscle fibers • In a female: • It is about 4 centimeters long • It runs obliquely • In a male: • It is about 17.5 centimeters long • It has a dual function for both urination and reproduction • It has three sections: • Prostatic urethra • Membranous urethra • Penile urethra 50

Urethral glands Muscle layer Lumen of urethra Mucous membrane

Micturition â&#x20AC;˘ Urine leaves the urinary bladder by micturition or urination reflex

Micturition

20.4 Clinical Application Urinalysis: Clues to Health

20.5: Lifespan Changes • The urinary system is sufficiently redundant, in both structure and function, to mask age-related changes • The kidneys become slower to remove nitrogenous wastes and toxins and to compensate for changes that maintain homeostasis • Changes include: • The kidneys appear scarred and grainy • Kidney cells die • By age 80 the kidneys have lost a third of their mass • Kidney shrinkage is due to loss of glomeruli • Proteinuria may develop • The renal tubules thicken • It is harder for the kidneys to clear certain substances • The bladder, ureters, and urethra lose elasticity • The bladder holds less urine 55

Important Points in Chapter 20: Outcomes to be Assessed 20.1: Introduction Name the organs of the urinary system and list their general functions. 20.2: Kidneys Describe the location of the kidneys. Describe the structure of a kidney. List the functions of the kidneys. Trace the pathway of blood flow through the major vessels within a kidney. Describe a nephron and explain the functions of its major parts. 20.3: Urine Formation 56

Explain how glomerular filtrate is produced and describe its composition.

Important Points in Chapter 20: Outcomes to be Assessed Explain how various factors affect the rate of glomerular filtration and identify ways that this rate is regulated. Define tubular reabsorption and explain its role in urine formation. Identify the changes in the osmotic concentration of the glomerular filtrate as it passes through the renal tubule. Identify the characteristics of the countercurrent mechanism and explain its role in concentrating the urine. Define tubular secretion and explain its role in urine formation. 20.4: Elimination of Urine Describe the structures of the ureters, urinary bladder, and urethra. Define micturition and explain how it occurs and how it is controlled.57

Important Points in Chapter 20: Outcomes to be Assessed 20.5: Lifespan Changes Describe how the components of the urinary system change with age.

Quiz 20 Complete Quiz 20 now! Read Chapter 21. 59