The Urinary System Urinary or Excretory System Functions

The Urinary System

Urinary or Excretory System �Functions: �Removes certain wastes and excess water from the body �Maintains the acid-base balance of the body

� Parts include two kidneys, 2 ureters, the bladder, and the urethra

Kidneys �Two bean-shaped organs � Located on either side of the vertebral column behind the upper part of the abdominal cavity and separated from this cavity by the peritoneum � Protected by the ribs and a heavy cushion of fat � Connective tissue helps hold the kidneys in position � Each kidney is enclosed in a mass of fatty tissue called the adipose capsule � Cover externally by a tough, fibrous tissue called the renal fascia or fibrous capsule

Kidney Sections: �Cortex �(1) Outer section of the kidney �(2) Contains most of the nephrons that aid in the production of urine �Medulla � (1) Inner section of the kidney � (2) Contains most of the collecting tubules that carry the urine from the nephrons on through the kidney

Hilum of Kidney: �Notched or indented area on each kidney �Area where ureter, nerves, blood vessels, and lymph vessels enter and leave the kidney

Nephrons �Microscopic filtering units located in the kidney �Over one million per kidney � Each nephron consists of a glomerulus, Bowman’s capsule, a proximal and distal convoluted tubule, and a collecting duct (tubule)

�Renal arteries carry blood to the kidney �Branches of the renal artery pass through the medulla to the cortex where the blood enters the first part of the nephron, the glomerulus

Glomerulus of the Nephron: �(1) Cluster of capillaries �(2) As blood passes through water, mineral salts, sugar, metabolic products and other substances are filtered out of the blood �(3) Red blood cells and proteins are not filtered out

Glomerulus continued: �Filtered blood leaves the glomerulus and eventually is carried to the renal vein, which carries it away from the kidney �Substances filtered out in the glomerulus enter the next section of the nephron, Bowman’s capsule

Bowman’s Capsule: � (1) C-shaped structure that surrounds the glomerulus � (2) It is the start of the convoluted tubule � (3) Picks up the materials filtered from the blood in the glomerulus � (4)Passes the materials into the convoluted tubule

Convoluted Tubules: �As these materials pass through the various sections of the tubule, substances needed by the body are reabsorbed and returned to blood capillaries �At the end, most of the water, sugar, vitamins, and mineral salts have been reabsorbed �Excess sugar and salts, some water, and wastes, including urea, uric acid, and creatinine, remain in the tubules and become known as the concentrated liquid called urine

Collecting Ducts: �Urine now enters collecting ducts or tubules located in the medulla �Collecting tubules empty into a funnel-shaped structure, the renal basin or pelvis, which is the first section of the ureter

Ureters �Two muscular tubes about 10 to 12 inches long �One extends from the renal pelvis of each kidney to bladder �Peristalsis, a rhythmic wavelike motion of the involuntary muscle, moves the urine through the ureter from the kidney to the bladder

Bladder �Hollow muscular sac �Lies behind the symphysis pubis at the midline of the pelvic cavity �Has lining of mucous membrane �Arranged in a series of folds called rugae �Rugae disappear as muscles of the bladder allow it to expand fill with urine �Three layers of visceral (smooth) muscle form the walls

Bladder Functions: �Receives the urine from the ureters �Stores the urine until it is eliminated from the body �Urge to void (urinate or micturate) occurs when the bladder contains about 250 cc (1 cup) of urine, but bladder can hold much more urine

Circular Sphincter Muscles: �Control the bladder opening to prevent emptying �When bladder is full, receptors in the bladder will send out a signal for a reflex that will open the muscle �Reflex action cannot be controlled by infants, but as children get older, they learn to control this reflex

Urethra: �Tube that carries the urine from bladder to the outside �External opening is called the urinary meatus �Different in females than males

Urethra cont. �Females �Tube about 1 ½ inches (3. 75 cm) long �Opens in front of the vagina �Carries only urine to the outside

Urethra cont: �Males �S-shaped tube about 8 inches (20 cm) long �Passes through the prostate gland out through the penis �Carries both urine from the urinary system and semen from the reproductive system

Urine � 1. Liquid waste product produced by the urinary system � 2. About 95 percent water � 3. Waste products dissolved in this water are urea, uric acid, creatinine, mineral salts, and various pigments � 4. Excess useful products, such as sugar, can also be found in urine but their presence usually indicates disease � 5. About 1, 500 to 2, 000 cc (1½ to 2 quarts) of urine are produced daily from the approximately 150 quarts of liquid that is filtered through the kidneys �

�Conditions affecting urination � 1. Polyuria: excessive urination � 2. Oliguria: below normal amounts of urination � 3. Anuria: absence of urination � 4. Hematuria: blood in the urine � 5. Pyuria: pus in the urine � 6. Nocturia: urination at night � 7. Dysuria: painful urination � 8. Retention: inability to empty the bladder � 9. Incontinence: involuntary urination

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