Essentials of Human Anatomy & Physiology (Seventh edition) Elaine N. Marieb

Urinary system

Urinary system

Objectives

Functions of Urinary System.

Anatomy of the Urinary System.

Anatomy of the Kidney.

Funct ions of Kidney.

Describe and function of ureter.

Describe and function of urinary bladder.

Describe and function of urethra.

Identify Disease disorder.

Main Functions of Urinary System

Kidneys filter blood to keep it pure Toxins Metabolic wastes Excess water

Dispose of nitrogenous wastes from blood Urea Uric acid Creatinine Regulate the balance of water &

electrolytes &acids and bases

kidney 1. Primary organs of the urinary system

2. Located between the 12th thoracic and 3rd lumbar

vertebrae. Right is usually lower due to liver.

3. Lie in shallow depressions against the posterior

abdominal wall

4. Held in place by connective tissue [renal fascia] and

surrounded by thick layer of adipose [perirenal fat]

Structure of the Urinary system

Paired kidneys

A ureter for each kidney

Urinary bladder

Urethra

Anatomy of the Kidney

About 1% of total body weight.

Main structures of the kidney:

1. Renal cortex

2. Renal medulla

3. Renal pelvis

4. Nephrons_____ is the

functional unit of the

kidney where urine forms

Functions of the kidneys

1. Excretion of waste products from the body.

2. Elimination of foreign substances.

3. Regulation of the amount of water in the body.

4. Regulate blood pressure.

5. Secrete erythropoietin.

6. Help activate vitamin D.

Ureters The wall of the ureter consists of three layers: The outermost is a fibrous coat, The middle layer is muscular [ circular & longitudinal] The innermost layer is called the mucosa, a transitional

epithelium that is continuous with the lining of the renal pelvis and bladder, also secretes a protective mucus

Function :-

Each ureter is about 25 cm long and carries urine from the renal pelvis to the urinary bladder via peristaltic waves.

Urinary Bladder

Smooth, muscular sac It lies retroperitoneally on the pelvic floor posterior to

the pubic symphysis

The bladder wall has three layers

1. Transitional epithelial mucosa

2. A thick muscular layer

3. A fibrous adventitia

4. Males : prostate gland surrounds the neck inferiorly

5. Females : anterior to the vagina and uterus

Function of Urinary Bladder

1) stores urine

2) The bladder is distensible and collapses when empty

3) As urine accumulates, the bladder expands without

significant rise in internal pressure

Urethra

Muscular tube that:

Drains urine from the bladder to the outside of the

body

Sphincters keep the urethra closed when urine is

not being passed. There are two

Internal urethral sphincter : involuntary control

External urethral sphincter : voluntary control.

Urethra

• The female urethra is tightly

bound to the anterior vaginal

wall

• Its external opening lies

anterior to the vaginal opening

and posterior to the clitoris Females 3-4 cm

Urethra

The male urethra has three regions :

1. prostatic urethra

2. membranous urethra

3. penile urethra.

males20 cm

Physical Characteristics of Urine

1. pH

range 4.5-8 average 6.0

vegetarian diet: urine is

alkaline

protein rich diet: urine is

Acidic

2. Specific gravity

Ranges from 1.001 to 1.035

Urine is about 95% water.

Contains urea and uric acid

• Normally, 1-2 liters of

urine per day

3. Odor

normal is ammonia-like

diabetes mellitus-

smells fruity or acetone

like due to elevated

ketone levels

Chemical Composition of Urine

Urine is consider as toxic material as it contains:

1- Nitrogenous wastes

2-Other normal solutes include: ( Sodium, potassium,

phosphate, etc……)

3-Abnormally urinary constituents may indicate

pathology

DISEASES DISORDER

1. Kidney Stones: Kidney stones are solid masses of mineral salt.

2. Polyuria (or diuresis): output in excess of 2 L/day

Causes– fluid intake, some drugs, diabetes

3. Oliguria: output of less than 500 mL/day

4. Anuria: output of 0-100 mL/day

Causes– kidney disease, dehydration, etc.

5. Dialysis: blood filtration procedure done if there is

failure of the kidney.

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