Memmler`s The Human Body in Health and Disease

Memmler’s The Human Body in Health and Disease 11th edition

Chapter 22 The Urinary System

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Excretion Body systems work interdependently to maintain homeostasis by excretion • Urinary • Digestive • Respiratory • Integumentary

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Organs of the Urinary System • Two kidneys • Two ureters • Single urinary bladder • Single urethra

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Male urinary system, showing blood vessels.

Zooming In: What vessel supplies blood to the kidney? What vessel drains the kidney?

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Kidney Activities • Excretion – Urea • Water balance maintenance • Body fluid acid–base regulation • Blood pressure regulation – Angiotensin

– Aldosterone • Red blood cell production regulation

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Kidney Structure • Membranous renal capsule of fibrous connective tissue • Adipose capsule of fat • Fascia anchors kidney to peritoneum and abdominal wall • Retroperitoneal space • Right kidney lower than left to accommodate liver

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Blood Supply to the Kidney • Renal artery supplies blood • Nephrons are functional units • Renal vein drains blood

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Kidney Organization • Hilum • Renal cortex (outer portion) • Renal medulla (inner portion) – Renal pyramids • Renal pelvis – Calyces

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Longitudinal section through the kidney. Its internal structure is shown (left), along with an enlarged diagram of nephrons (right). Each kidney contains more than 1 million nephrons. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

The Nephron Functional kidney unit • Glomerular (Bowman) capsule – Glomerulus

– Afferent arteriole • Peritubular capillaries • Proximal convoluted tubule (PCT) • Nephron loop (Loop of Henle)

– Descending limb – Ascending limb • Distal convoluted tube (DCT) • Collecting duct Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

A nephron and its blood supply. The nephron regulates the proportions of water, waste, and other materials according to the body’s constantly changing needs. Materials that enter the nephron can be returned to the blood through the surrounding capillaries. Zooming In: Which of the two convoluted tubules is closer to the glomerular capsule? Which convoluted tubule is farther away?

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Formation of Urine • Glomerular filtration –

Glomerular filtrate

• Tubular reabsorption –

Diffusion

–

Osmosis

–

Active transport

• Tubular secretion • Countercurrent mechanism

–

Concentration of urine

–

Antidiuretic hormone (ADH)

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Summary of urine formation in a nephron. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

Control of Blood Pressure • Juxtaglomerular apparatus: Specialized cells that regulate kidney function • Triggered by low blood pressure – Secretes renin enzyme

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Structure of the juxtaglomerular (JG) apparatus. Note how the distal convoluted tubule contacts the afferent arteriole (right). Cells in these two structures make up the JG apparatus. Zooming In: The JG apparatus is made up of cells from which two structures? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

The Ureters • Long, slender, muscular tubes – Epithelial cell lining – Involuntary muscle layer – Fibrous connective tissue coat • Entirely extraperitoneal • Extend from kidney to urinary bladder • Move urine by gravity and peristalsis

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The Urinary Bladder Temporary reservoir for urine • Multiple layers • Mucous membrane

– Transitional epithelium – Rugae – Connective tissue – Three-layered coat of involuntary muscle tissue

– Incomplete coat of peritoneum • Trigone

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The Urethra Tube that extends from the bladder to the outside • Male – Part of both reproductive and urinary systems • Female – Entirely separate from reproductive system

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Urination Process of expelling urine from bladder (micturition) • Involuntary control – Internal urethral sphincter • Voluntary control – External urethral sphincter

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The Urine • 95% water, 5% dissolved solids and gases • pH averages 6.0 • Specific gravity measures amount of dissolved substances – Normal range 1.002 to 1.040

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Normal Constituents Dissolved solids normally found in urine • Nitrogenous waste products –

Urea

–

Uric acid

–

Creatinine

• Electrolytes –

Sodium chloride

–

Sulfates

–

Phosphates

• Pigment

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Abnormal Constituents Urinalysis is evaluation of urine • Glucose –

Glycosuria

• Albumin

–

Albuminuria

• Blood –

Hematuria

• Ketones –

Diabetes mellitus and starvation

• White blood cells –

Pyuria

• Casts –

Nephron disease Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

Disorders of the Urinary System Portion of urinary system most prone to disorders is kidney

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Kidney Disorders Kidney disorders may be acute or chronic • Acute glomerulonephritis –

Most common kidney disease

• Pyelonephritis • Hydronephrosis • Polycystic kidney • Tumors • Kidney stones (calculi)

• Renal failure –

Leads to uremia, high levels of nitrogenous waste in the blood

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Renal Dialysis and Kidney Transplantation • Dialysis – Hemodialysis – Peritoneal dialysis • Kidney transplantation – Final option for treatment of kidney failure

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Disorders of the Ureters • Subdivision at renal pelvis • Constricted or abnormally narrow parts (strictures) • Renal ptosis • Ureterocele • Ureteral stones

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Bladder Disorders • Rupture • Cystitis –

Interstitial cystitis

• Tumors –

90% arise from epithelial lining

–

If bladder removed (cystectomy), ureters diverted to part of ileum in an ilial conduit

• Urinary incontinence –

Stress incontinence

–

Urge incontinence

–

Overflow incontinence

–

Enuresis

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Disorders of the Urethra • Congenital anomalies – Narrowing of opening or urethra itself – Presence of valve-like structure at junction of urethra and bladder – Hypospadias • Urethritis

• Straddle injuries

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The Effects of Aging • Loss of ability to concentrate urine • Decrease in number and size of nephrons • Increase in blood urea nitrogen (BUN) • Urinary infections • Prostate enlargement • Decreased bladder capacity • Incontinence

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End of Presentation

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