Overview of the urinary tract

Overview

The urinary system is composed of the kidneys, ureters, bladder, and the urethra. This group of organs functions to maintain the fluid balance of the body and to filter toxic substances from the bloodstream. Urine is generated by the kidneys and carried to the bladder through the ureters. From the bladder, it is released through the urethra.

Overview of urine generation and passage

Ureters

Characteristics

Anatomy

Relationship to neighboring structures

  • Travel posterior to the gonadal arteries
  • Travel anterior to the common iliac arteries external iliac artery (or external iliac arteries) at the level of the bifurcation
  • Travel posterior to the vas deferens (in males), and the uterine artery (in females)

Urinary bladder

  • Overview

  • The bladder is a hollow, triangular-shaped organ.
  • It is located extraperitoneally, behind the pubic symphysis, within the pelvis, and beneath the peritoneum.
  • It can hold∼ 500–1000 mL of urine.
  • Sensation of bladder fullness is felt at ∼ 300–500 mL.
  • It contains smooth muscle (the detrusor muscle of the bladder) that contracts during micturition.

Anatomy

Structure Location Characteristics
Apex
  • Uppermost aspect of the bladder dome
Body
  • Hollow and muscular cavity located between the apex and the fundus
Fundus
  • Located posteriorly
Bladder neck
  • Joins the bladder and the urethra
  • Formed by the fundus and the inferolateral surfaces of the bladder cavity
  • Attached to the posterior surface of the pubis via the pubourethral ligament
Trigone of the bladder
  • Triangular area of mucosa located in the internal surface of the bladder
  • Formed by the two ureteral openings superiorly (base), and the opening of the urethra (apex)

Rupture of the bladder dome (e.g., blunt abdominal trauma), especially when the bladder is full, can cause peritonitis due to extravasation of urine into the peritoneal cavity

Muscles of the bladder

Urethra

A hollow and tubular structure that begins in the neck of the bladder, continues through the urogenital sinus, and ends in the external urethral sphincter. Under control of the urethral sphincter, it transports urine from the urinary bladder to the exterior of the body.

Urethral sphincter

See “Urogenital diaphragm” in the learning card on pelvis and hip joint for more information about the urethral sphincter and compressor urethrae muscle.

Male urethra

The male urethra is divided into three parts and transports urine and semen through the penis to the exterior.

Female urethra

The female urethra consists of only one part and transmits only urine to the exterior.

  • Anatomy
    • Suspended proximally by urethropelvic ligaments bilaterally
    • Attached to the inferior border of the pubic rami
    • Suspended distally by the pubovesical ligament and suspensory ligament of the clitoris
    • The external urethral sphincter in females is composed of three distinct parts. (See external urethral sphincter for more information.)
  • Lymphatic drainage

Differences between male and female urethras

Male Female

Urinary catheterization (e.g., Foley catheter) should be avoided in patients with suspected urethral injury.

Vasculature

Kidneys

  • The kidneys are supplied by the renal veins and arteries. For more information see vasculature in kidneys.

Ureters

  • Abdominal part
    • Arteries: renal arteries, gonadal arteries (testicular and ovarian)
    • Veins: renal veins, gonadal veins.
  • Pelvic part
    • Arteries: branches of the common iliac and internal iliac arteries (e.g., superior and inferior vesical arteries), and ovarian arteries in females.
    • Veins: branches of the common iliac and internal iliac vein (e.g., superior and inferior vesical vein) , and ovarian vein in females.

Bladder

  • Arteries
    • Branches of the internal iliac arteries
      • Superior vesical artery
      • Inferior vesical artery
      • Vaginal artery (in females)
    • Also branches of the obturator artery, and inferior gluteal artery
  • Veins
    • Branches that mirror the arterial supply
    • Drain into the internal iliac veins

Urethra

In males

In females

  • Arteries
    • Internal pudendal arteries
    • Vaginal arteries
  • Veins
    • Internal pudendal veins
    • Vaginal veins

Microscopic anatomy

For more information, see “Microscopic anatomy” in the learning card on kidneys.

Ureter

  • Transitional epithelium
  • Muscular layers: contract and relax in a peristaltic pattern
    • Inner longitudinal layer
    • Outer circular layer
    • Outer longitudinal layer (mainly present in the distal third of the ureter)

Urinary bladder

  • Transitional epithelium
    • Empty bladder
      • Composed of 5–6 layers of cells
      • Cells are rounded and thick
    • Full bladder
      • Composed of 3–4 layers of cells
      • Cells are flatter and thinner
  • Muscular layers
    • Inner longitudinal layer
    • Middle circular layer
    • Outer longitudinal layer

Urethra

Embryology

Germ layer derivatives

Development

Clinical significance

last updated 11/11/2018
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