Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between male and female development of urethra

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Difference between male and female development of urethra

The development of  urethra in males & females originates from  urogenital sinus, which is derived from the hindgut endoderm during embryonic development. The process differs significantly between male and female sexes due to the influence of sex hormones.

1. Development of Male Urethra

  • Origin: The male urethra develops from  urogenital sinus and extends into the phallus.
  • Stages of Development:
    • Prostatic and membranous urethra: Derived from the pelvic part of the urogenital sinus.
    • Penile (spongy) urethra: Derived from the phallic part of the urogenital sinus.
    • Glans urethra: Formed by canalization of the ectodermal cord from the tip of the glans penis.
  • Hormonal Influence: Testosterone, via dihydrotestosterone (DHT), plays a crucial role in urethral elongation and closure.
  • Clinical Correlation:
    • Hypospadias: Incomplete fusion of urethral folds results in an abnormally placed urethral opening.

2. Development of Female Urethra

  • Origin: Like males,  female urethra develops from the urogenital sinus.
  • Stages of Development:
    • The entire female urethra is derived from the pelvic part of  urogenital sinus.
    • It remains short and opens into  vestibule.
  • Hormonal Influence: The absence of DHT results in minimal elongation.
  • Clinical Correlation:
    • Urethral diverticulum: Congenital anomaly leading to outpouching of  urethral wall.

Parts of primitive urogenital sinus

Male  urethra

Female urethra

1.     Lower part of vesico-urethral canal

Prostatic part of urethra up to the level of opening of ejaculatory duct

Most of the part of female urethra (upper part)

2.     Pelvic part of definitive urogenital sinus

Prostatic part of urethra below the opening of ejaculatory duct and membranous part of urethra

Small part of female urethra (lower part)

3.     Phallic part of definitive urogenital sinus

Penile part of urethra

Vestibule of female external genitalia into which the urethra is opened  (external opening )

4.     Surface ectoderm

Terminal part (which occupies the glans penis )

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