Urethra - Anatomy & Physiology

()Map URINARY SYSTEM (Map)

Introduction

This muscular tube is the connection between the bladder and the external environment and plays a vital role in concious urinary continence.

Female

• Empties at the external urethral orifice on the ventral wall of the vagina
• This is often at the vestibulo vaginal junction
• Only urine passes through it
• The urethral submucosa has a network of veins which may contribute to continence by forming a kind of erectile tissue.
• Length and diameter is species specific
  • Short and wide - mare
  • 2 fossa - bitch
  • Suburethral diverticulum - cow and sow

Male

• Empties at tip of penis
• Divided into 3 parts
  • Pre-prostatic - bladder neck to seminal hillock
  • Prostatic portion - openings of deferant, vesicular and prostatic ducts
  • Penile portion - ischial arch to penile tip
  • Note the first 2 combined are called the pelvic portion

Muscles of the Urethra

The urethralis muscle runs the entire length of the urethra and forms the external urethral sphincter.

Unlike the internal sphincter the external sphincter is composed of striated muscle fibres which are under the voluntary control of the somatic nervous system.

Somatic Motor Supply - External Urethral Sphincter

• S1-S2
• Pudendal Nerve
• No synapse
• Innervates the urethral skeletal muscle - external urethral sphincter
• Function is to contract and retain urine

Blood Supply

Blood Supply comes from the Urethral Artery