Memmler’s The Human Body in Health and Disease 11th edition Chapter 22 The Urinary System

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

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

Male urinary system, showing blood vessels.  

Kidney Activities Excretion Urea Water balance maintenance Body fluid acid–base regulation Blood pressure regulation Angiotensin Aldosterone Red blood cell production regulation

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

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

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

Longitudinal section through the kidney 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. 

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

A nephron and its blood supply 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.  

Formation of Urine Glomerular filtration Glomerular filtrate Tubular reabsorption Diffusion Osmosis Active transport Tubular secretion Countercurrent mechanism Concentration of urine Antidiuretic hormone (ADH)

Formation of Urine cont… Know: in filtration, blood pressure is high in the glomerulus. Know: in reabsorption,

Summary of urine formation in a nephron.

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

Structure of the juxtaglomerular (JG) apparatus 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.  

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

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

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

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

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

Normal Constituents Dissolved solids normally found in urine Nitrogenous waste products Urea Uric acid Creatinine Electrolytes Sodium chloride Sulfates Phosphates Pigment

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

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

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

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

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

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

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

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

End of Presentation