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Male and female urinary bladders in lateral cross-section. In humans, the bladder is a hollow muscular organ situated at the base of the pelvis. In gross anatomy, the bladder can be divided into a broad fundus (base), a body, an apex, and a neck. [5]
The anatomy of the human urinary system differs between males and females at the level of the urinary bladder. In males, the urethra begins at the internal urethral orifice in the trigone of the bladder, continues through the external urethral orifice, and then becomes the prostatic, membranous, bulbar, and penile urethra.
The female or male external sphincter muscle of urethra (sphincter urethrae): located in the deep perineal pouch, at the bladder's distal inferior end in females, and inferior to the prostate (at the level of the membranous urethra) in males. It is a secondary sphincter to control the flow of urine through the urethra.
This means that in the event of a rival male's sperm occupying the reproductive tract of a female, the human penis is able to displace the rival sperm, replacing it with his own. [42] Semen displacement has two main benefits for a male. Firstly, by displacing a rival male's sperm, the risk of the rival sperm fertilising the egg is reduced. [43]
It is formed by the neck of the urinary bladder. It opens at the apex/inferior angle of the trigone of the bladder, some 2-3 cm anteromedial to either ureteral orifice. [1] The mucous membrane immediately posterior to it presents a slight elevation in males - the uvula vesicae - caused by the middle lobe of the prostate. [citation needed]
The urethra (pl.: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, [1] [2] through which placental mammals urinate and ejaculate. [3] In non-mammalian vertebrates, the urethra also transports semen but is separate from the urinary tract.
The male urethra enters the penis at the superior aspect of the anterior part of the bulb (most of the bulb is thus situated inferoposteriorly to the urethra), and the arteries of bulb of penis enter near the urethra. [2] The bulb of penis is homologous to the vestibular bulbs in females. [3]
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system.The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle.