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 Medulla (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 and 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 (3.75cm) 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 and 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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