Urinary System Structures and Functions

Urinary System Structures

• The urinary system functions:
  • Excretion of harmful waste products.
  • Regulation of homeostasis.

Kidneys (nephr/o, ren/o)

• Filter the blood to remove wastes, excess water, and salts.
• There are two kidneys, located on either side of the spine, outside the peritoneum (retroperitoneal) in the lumbar region.
• Secrete substances:
  • Renin: Raises blood pressure to maintain circulation through the kidney.
  • Erythropoietin: Stimulates red blood cell production.
  • Calciferol: A form of vitamin D.

Urine Formation

• Nephron: The functional unit of the kidney.
  • Each kidney contains approximately one million nephrons.
  • Nephrons filter the blood and concentrate the waste into urine.
• Parts of a nephron:
  1. Glomerulus
  2. Glomerular (Bowman) capsule
  3. Renal tubule
• Processes in urine formation:
  1. Glomerular filtration
  • Albuminuria
  1. Tubular reabsorption
  2. Tubular secretion
• Glomerulus is responsible for filtering blood and water so that it can pass out of the capillaries and into the Bowman capsule.
• Proteins and blood cells should not appear in the urine because the walls of the glomeruli prevent those large substances from filtering through.
• Reabsorption ensures that the body retains essential substances such as sugar or salt.
• Secretion: The final process of some substances being secreted from the bloodstream and into the renal tubule.
• Urine composition: Is 95% water and 5% waste (urea, creatinine) salts, acids, and drugs.
• Urea can become toxic if it accumulates instead of being properly excreted.

Ureters (ureter/o)

• Carry urine from the renal pelvis of each kidney to the urinary bladder.
• Approximately 25–30 cm long.
• Peristalsis is used to move urine downward.

Urinary Bladder (cyst/o, vesic/o)

• A hollow, muscular organ that acts as a reservoir for urine.
• Located in the anterior portion of the pelvic cavity.
• As the bladder fills with urine from the ureters, the walls stretch and receptors send a message to the brain which creates the urge to micturate.

Urethra (urethr/o)

• Carries urine from the bladder to the urinary meatus.
• In females:
  • Conveys only urine.
  • Approximately 3–4 cm long.
• In males:
  • Carries both urine and semen.
  • Approximately 17–20 cm long.
  • The beginning of the male urethra is surrounded by the prostate gland.
• The shortened length of the urethra in females makes it more difficult for women to flush out bacteria.
• Females are statistically more prone to contracting urinary tract infections (UTI).

Career Spotlight

• Nephrologist: Specializes in diagnosing and treating disorders of the kidneys.
• Urologist: Specializes in diagnosing and treating disorders of the female urinary system and the male genitourinary system.

Word Parts

• Combining Forms:
  • Nephr/o; Ren/o: Kidney
  • Pyel/o: Renal pelvis
  • Ureter/o: Ureter
  • Cyst/o; Vesic/o: Bladder
  • Urethr/o: Urethra
  • Ur/o; urin/o: Urine
  • Meat/o: Meatus; opening
  • Peritone/o: Peritoneum
  • Glomerul/o: Glomerulus
  • Cortic/o: Cortex
  • Medull/o: Medulla
  • Albumin/o: Albumin
• Prefixes/Suffixes:
  • A-; An-: Not; without
  • Retro-: Behind
  • -uria: Urination, urine condition
  • -logist: One who studies
  • -al; -ar; -ic; -ary: Pertaining to

Fill in the Blanks

• cardi/o: Heart
• appendic/o: Appendix
• cheil/o: Lips
• dent/i: Teeth
• col/o; colon/o: Large intestine
• Word parts that mean kidney: nephr/o and ren/o