Logo

    Related Topics

    From Urinary System

    Prostatic Urethra
    Passes through prostate gland.
    Bladder Neck
    Region surrounding internal urethral orifice.
    Median Umbilical Ligament
    Remnant of embryonic urachus.
    Renal Fascia
    Connective tissue anchoring kidney.
    Arcuate Arteries
    Arch over the base of pyramids.
    External Urethral Meatus
    External urethral opening.
    Ureteral Openings
    Where ureters drain into bladder.
    Urachus
    Fetal remnant connecting bladder to umbilicus.
    Glomerulus
    Capillary tuft where filtration starts.
    Renal Columns
    Tissue between pyramids extending into medulla.
    Internal Urethral Sphincter
    Involuntary control of urine release.
    External Urethral Sphincter
    Voluntary control of urination.
    Pelvic Floor Muscles
    Support bladder and urethra.
    Papillary Duct
    Drains urine into minor calyx.
    Efferent Arteriole
    Drains from glomerulus.
    Proximal Convoluted Tubule
    Reabsorbs water, ions, and nutrients.
    Minor Calyces
    Receive urine from renal papillae.
    Detrusor Muscle
    Smooth muscle for bladder contraction.
    Pelvic Ureter
    Segment within the pelvic cavity.
    Bladder Peritoneum
    Covers superior bladder surface.
    Kidneys
    Primary organs for filtration, fluid balance, and excretion.
    Hilum of Kidney
    Entry/exit site for vessels, nerves, and ureter.
    Renal Vein
    Drains blood from the kidney.
    Renal Pyramids
    Cone-shaped tissues in the medulla.
    Spongy Penile Urethra
    Longest male urethra segment.

    Urethra

    Reviewed by our medical team

    Carries urine out of the body.

    1. Overview

    The urethra is a tubular structure that serves as the final passageway for urine excretion from the bladder to the external environment. It also plays a reproductive role in males by transporting semen. The urethra differs in length, anatomy, and function between males and females. In both sexes, it is lined by specialized epithelium and surrounded by muscular layers that regulate urinary flow.

    2. Location

    The urethra begins at the internal urethral orifice at the base of the bladder and terminates at the external urethral meatus. Its course varies by sex:

    • Male urethra: Approximately 18–22 cm long, it passes through the prostate, perineal membrane, and penis. It serves both urinary and reproductive functions.

    • Female urethra: Shorter, about 3–5 cm, it extends from the bladder neck to the external meatus located anterior to the vaginal opening.

    3. Structure

    The urethra is composed of three main layers:

    • Mucosa: Lined by varying epithelium:

      • Transitional epithelium near the bladder

      • Pseudostratified columnar epithelium in mid-portions

      • Stratified squamous epithelium near the external opening

    • Submucosa: Contains glands (e.g., urethral glands of Littre) and a vascular plexus that supports mucosal integrity.

    • Muscular layer:

      • Inner longitudinal and outer circular smooth muscle layers (involuntary)

      • Striated muscle in the external urethral sphincter (voluntary)

    Male Urethral Segments:

    1. Prostatic urethra: Passes through the prostate gland.

    2. Membranous urethra: Shortest and narrowest, passing through the urogenital diaphragm.

    3. Spongy (penile) urethra: Longest segment, within the corpus spongiosum.

    Female Urethral Features:

    • Lacks distinct segmentation but is closely associated with the anterior vaginal wall.

    • Surrounded by the external urethral sphincter and pelvic floor muscles.

    4. Function

    The urethra's primary functions include:

    • Urine excretion: Final conduit for voiding urine from the bladder to the exterior.

    • Semen transport (males): During ejaculation, it carries semen through the penile urethra.

    • Flow control: Coordinated action of internal and external urethral sphincters regulates continence and voiding.

    5. Physiological Role(s)

    The urethra supports urinary physiology through several mechanisms:

    • Maintaining continence: The sphincters and pelvic floor muscles ensure voluntary control over urination.

    • Responsive to stretch and pressure: Mechanoreceptors in the urethral wall trigger the micturition reflex.

    • Protection against infection: Urethral glands secrete mucus that helps flush pathogens and maintain pH.

    • Neural integration: The urethra is involved in the autonomic and somatic control of voiding via spinal and supraspinal centers.

    6. Clinical Significance

    Urinary Tract Infections (UTIs)

    Commonly affect the female urethra due to its short length and proximity to the anus. Symptoms include dysuria, frequency, urgency, and suprapubic discomfort. Diagnosed via urinalysis and treated with antibiotics.

    Urethral Stricture

    More common in males, often caused by trauma, infection (e.g., gonorrhea), or instrumentation. Results in narrowed urethral lumen, leading to poor urinary stream, straining, and incomplete emptying. Managed via dilation, urethrotomy, or urethroplasty.

    Urethritis

    Inflammation of the urethra, often due to sexually transmitted infections like chlamydia or gonorrhea. Presents with pain, burning, and urethral discharge.

    Urinary Incontinence

    Involves involuntary leakage of urine due to urethral sphincter weakness or pelvic floor dysfunction. Common in postpartum women and elderly populations. Treated with pelvic floor exercises, medications, or surgery.

    Urethral Cancer

    Rare malignancy that may arise in either sex. Presents with hematuria, mass, or urethral discharge. Diagnosed by urethroscopy and biopsy. Treatment involves surgery, chemotherapy, or radiation depending on stage and location.

    Catheterization and Instrumentation

    The urethra is the standard route for urinary catheter insertion. Anatomical knowledge is essential to avoid complications like urethral trauma, false passage, or infection.

    Did you know? The kidneys contain more than 1 million nephrons that help filter your blood and make urine?