The Urinary System

1. The Urinary System

2. Urinary System Functions • Regulation of the volume of blood by excretion or conservation of water • Regulation of the electrolyte content of the blood by the excretion or conservation of minerals • Regulation of the acid-base balance of the blood by the excretion or conservation of ions such as hydrogen (H+) and bicarbonate (HCO3) • Regulation of all of the above in tissue fluid

3. Urinary System Functions • In summary, the process of urine formation helps maintain the normal composition, volume and pH of both blood and tissue fluid by removing those substances that would upset the normal constancy and balance of these extracellular fluids

4. Urinary System Structure • Consists of: • Kidneys • Ureters • Urinary Bladder • Urethra • Works in conjunction with the circulatory system

5. Kidneys • Embedded in adipose tissue that acts as a cushion and is in turn covered by a fibrous connective tissue membrane called the renal fascia, which helps hold the kidneys in place. • Each kidney has an indentation called the hiluson its medial side. At the hilus, the renal artery enters the kidney, and the renal vein and ureter emerge. • Function of the kidney is the formation of urine.

6. Structure of the Kidney • Outer tissue layer is called the renal cortex. • Inner tissue layer is called the renal medulla. • The third area is called the renal pelvis, this is not a layer of tissue, but rather a cavity formed by the expansion of the ureter within the kidney at the hilus

7. The Kidney

8. The Nephron • Is the structural and functional unit of the kidney • Each kidney contains approx 1 million nephrons. • It is in the nephrons, with their associated blood vessels, that urine is formed.

9. The Nephron

10. Elimination of Urine • Is performed by the rest of the structures within the Urinary System: • Ureters • Urinary Bladder • Urethra

11. Ureters • Each ureter extends from the hilus of the kidney to the lower, posterior end of the urinary bladder. • Smooth muscle in the wall of the ureter contracts in peristaltic waves to propel urine toward the urinary bladder • As the bladder fills, it expands and compresses the lower ends of the ureters to prevent backflow of urine

12. Ureters

13. Urinary Bladder • Is a muscular sac that acts as a reservoir for accumulating urine, and it contracts to eliminate urine. • The mucosa of the bladder is transitional epithelium, which permits expansion without tearing the lining. • The smooth muscle layer in the wall of the bladder is called the detrusor muscle. It is a muscle in the form or a sphere; when it contracts it becomes a smaller sphere and the volume diminishes. • The opening of the urethra is the internal urethral sphincter (muscle), which is involuntary

14. Urinary Bladder

15. Urethra • Carries urine from the bladder to the exterior • External urethral sphincter is made of the surrounding skeletal muscle of the pelvic floor, and is under voluntary control. • In females, the urethra is anterior to the vagina • In males, the first part just outside the bladder is called the prostatic urethra because it is surrounded by the prostate gland. The rest of the urethra passes through penile tissue. • In males, the urethra carries sperm as well as urine.

16. Urethra

17. Urination Reflex • Urination is also called micturition or voiding • This reflex is a spinal cord reflex over which voluntary control may be exerted. • The stimulus for the reflex is stretching of the detrusor muscle of the bladder.