Physiology of urethra

Urethra has two functions

1. For urination

2. Ejaculation in sexual intercourse and this function also includes emissions of semen.


The bladder neck interconnects the bladder with the posterior urethra below. It contains the internal sphincter. The internal sphincter. keeps urine out of the bladder neck and also out of the posterior urethra which leads off from the bladder neck immediately. But its main function is to prevent retrograde ejaculation at sexual intercourse. The urogenital diaphragm contains the sphincter urethrae  which is the external sphincter that is under the control of will. It is this sphincter that is opened when there is the need to micturate.


Urethra is an important organ in the male. It is used for both reproductive and urinary functions. It passes semen from its prostatic part into the spongy part. The spongy part is the one that transverses the penis. It is also called penile urethra. When ejaculation is to take place in the male, semen is released from the seminal vesicle or from the tail of epididymis into the prostatic urethra in the first phase of ejaculation. The second phase is controlled by the bulbospongiosus muscle which assists the penile urethra to release forcibly its contained semen to the outside, and in reproductive capacity, into the vagina.

Cross section through urinary bladder; low power

The detrusor muscle is innervated by the parasympathetic outflow of the pelvic splanchnic nerve and they cause the detrusor to contract.

Internal urethral sphincter exists only in the male and it prevents retrograde ejaculation  and it contracts when its contained α1 adrenoceptors are stimulated. Urine is stored in the bladder when the detrussor relaxes and the sphincters close.



Gross Anatomy
Lymphatic drainage
Organ integration
Clinical anatomy






Chemical Pathology

Anatomical Pathology




 Roll over mouse to label

Interior of urinary bladder  





Main Subject Course Links

Anatomy Anesthesia Biochemistry Chemical pathology Community Health
Dermatology ENT Gynecology Hematology Imaging
Medicine Medical microbiology Obstetrics Ophthalmology Pathology
Pediatrics Pharmacology Physiology Psychiatry    Surgery/Orthopedics
eLab eOSCE eProcedures eInvestigations eSchool
eOrgans eLocator Anatomy Museum eDissector eFractures
All diseases eClerking eTreatment eDoctor ePatient


Electronic School of Medicine
Creator: Oluwole Ogunranti