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 Location Between 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 of Calcium 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 females Sits inferior to the uterus and anterior to the vagina In males The base of the urinary bladder lies between the rectum and the pubic symphysis The urethral opening lies at the lowest point in the bladder Has 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 females Urethra is very short about 1 inch In males 7- 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