Urinary System

Functions of the Urinary System

Removes organic waste products generated by the body’s cells

Regulates blood volume and blood pressure

Regulates the concentrations of ions in the blood plasma

Helps stabilizes blood pH

Conserves valuable nutrients.

Kidneys

LocationBetween T 12 and L 3

The right kidney sits slightly lower than the left

Lies between the muscles and the peritoneal lining of the dorsal cavity – retroperitoneal (retro means behind)

Held in place by overlying peritoneum and connective tissues

Covered by a dense tissue called the renal capsule

Cushioned by adipose tissue

Hilum

Renal capsule

Renal cortex

Renal pyramids

Renal pelvis

Nephrons

Muscular tube that drains the urine from the kidneys to the urinary bladder

Do not enter the peritoneal cavity

Have an opening into the urinary bladder that prevents backflow when the urinary bladder contracts

Inner layer – epithelium Middle layer – longitudinal and circular smooth muscle

Outer layer – connective tissue that is continuous with the renal capsule

About every 30 seconds a peristaltic contraction moves the urine along the ureter forcing it toward the urinary bladder.

Ureters

Composed ofCalcium deposits, magnesium salt or crystals

of uric acid

Not only obstruct urine flow in the ureter but can damage kidneys and prevent filtration

Calculi Kidney Stones

Hollow, muscular

Stores urine

Can hold up to 1 liter of urine

Held in place by peritoneal folds (ligaments) that extend to the umbilicus and bands that area connected to the pelvic and pubic bones

In femalesSits inferior to the uterus and anterior to the vagina

In malesThe base of the urinary bladder lies between the rectum and the pubic symphysis

The urethral opening lies at the lowest point in the bladderHas a sphincter called internal urethral sphincter, lined with transitional epithelium

A layer of circular and longitudinal muscles

Urinary Bladder

Urethra

Extends from the neck of the urinary bladder to the exterior

In femalesUrethra is very short about 1 inch

In males7- 8 inches

Passes through the muscular floor of the pelvic cavity with a skeletal muscle that forms external urethral sphincter that is under voluntary control

The urge to urinate happens when the bladder contains about 200 ml of urine.

Sustained contraction elevates the fluid pressure inside the baldder but does not occur unless both sphincters are relaxed

Aging and the Urinary System

The number of functional nephrons declines

Regulation of body pH declines

Absorbing sodium and water is reduced and more potassium ions are lost in the urine

Sphincter muscles lose tone and leads to incontinence, slow leaking of urine

In males urinary retention may develop because of enlargement of the prostate gland allows for restricting or preventing the flow or urine

Lower percent of body water as one ages causes less dilution of waste products and toxins

Mineral content such as calcium can be reduced by exercise and diet

Most disorders of other body systems as one ages will affect the urinary system