![]() At 16 weeks post conception, the genitalia are formed and distinct. By the 10th-12th week, the genitalia are distinctly male or female being and derived from their homologous structures. At eight weeks, a distinct phallus is present during the indifferent stage. External structures Īt six weeks post conception, the differentiation of the external genitalia in the male and female has not taken place. In the absence of testicular secretions, the female genitalia are formed. The prostate gland derives from the urogenital sinus, and the other embryonic structures differentiate into the external genitalia. The structures are masculinized by secretions of the testes: In the developing embryo if the testes are developed, it will produce and secrete male sex hormones during late embryonic development and cause the secondary sex organs of the male to develop. Genetic sex determines whether the gonads will be testes or ovaries. A sperm cell carrying a Y chromosome results in an XY combination, and a male child will develop. If this sperm cell contains an X chromosome it will coincide with the X chromosome of the ovum and a female child will develop. Sexual identity is determined at fertilization when the genetic sex of the zygote has been initialized by a sperm cell containing either an X or Y chromosome. ![]() (The spermatic cord, formed from spermatic artery, vein and nerve bound together with connective tissue passes into the testis through inguinal canal.) The scrotum remains connected with the abdomen or pelvic cavity by the inguinal canal. During times of lower temperatures, the Cremaster muscle contracts and pulls the scrotum closer to the body, while the Dartos muscle gives it a wrinkled appearance when the temperature increases, the Cremaster and Dartos muscles relax to bring down the scrotum away from the body and remove the wrinkles respectively. It also contains numerous nerves and blood vessels. ![]() The scrotum is a pouch-like structure that hangs behind the penis. The penis is supplied by the pudendal artery. The arteries of the penis are dilated while the veins are compressed so that blood flows into the erectile cartilage under pressure. Erection occurs because sinuses within the erectile tissue of the penis become filled with blood. When the male becomes sexually aroused, the penis becomes erect and ready for sexual activity. It has a long shaft and an enlarged bulbous-shaped tip called the glans penis, which supports and is protected by the foreskin. The penis is the male intromittent organ.
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