Anatomy & Physiology

Anatomy & Physiology Study Guide

The Testes Each testis is shaped like a flattened egg. The testes hang within the scrotum suspended posterior to the base of the penis. In cryptorchidism , one or both of the testes have not descended into the scrotum by the time of birth. In majority of these cases, descent of the testes occurs within a few weeks, but, if no descent occurs, the condition can be surgically corrected with an orchiectomy . As each testis moves through the body wall, it is accompanied by structures of the spermatic cord: the ductus deferens and the testicular blood vessels, nerves, and lymphatic vessels. The testis are subdivided by septa into a series of lobules . Distributed among the lobules are roughly 800 slender, tightly coiled seminiferous tubules . Each tubule averages about 80 cm (32 in.) in length, and a typical testis contains nearly one-half mile of seminiferous tubules. These tubules house sperm production. Delicate connective tissue encapsulates each tubule, and areolar tissue fills the spaces between the tubules. Within those spaces are numerous blood vessels and large interstitial cells ( cells of Leydig ). Interstitial cells are responsible for the production of androgens, the dominant sex hormones in males. Testosterone is the most important androgen. The Spermatic Cords Extending between the abdominopelvic cavity and the testes is a set of paired structures called the spermatic cords. Each spermatic cord consists of layers of fascia and muscle enclosing the ductus deferens and the blood vessels, nerves, and lymphatic vessels that supply the testes. The blood vessels include the testicular artery, deferential artery, and the pampini plexus of a testicular vein. Each spermatic cord starts at the entrance to the inguinal canal (a passageway through the abdominal musculature). In normal adult males, the inguinal canals are closed, but the presence of the spermatic cords creates weak points in the abdominal wall that remain throughout life. The Scrotum The scrotum is divided internally into two chambers. The raphe , a raised thickened area, marks the division between the two chambers. Each testis lies in a separate chamber, or scrotal cavity. Infection or inflammation of one testis rarely spreads to the other, due to the raphe and separate chambers. A narrow space separates the inner surface of the scrotum from the outer surface of the testis. The tunica vaginalis , a serous membrane, lines the scrotal cavity and reduces friction between the opposing surfaces. The scrotum consists of a thin layer of skin. The dermis contains a layer of smooth muscle named the dartos muscle . Resting muscle tone in the dartos muscle elevates the testes and causes the characteristic wrinkling of the scrotal surface. A layer of skeletal muscle, the cremaster muscle, lies deep to the dermis. Contraction of the cremaster muscle during sexual arousal or in response to decreased testicular temperature tenses the scrotum and pulls the testes closer to the body. To maintain acceptable testicular temperatures, the dartos and cremaster muscles relax or contract to move the testes away from or toward the body as needed. These two muscles relax and the testes move away from the body when body temperature rises. Sudden cooling of the scrotum, as occurs during entry into a cold swimming pool, results in contractions that pull the testes closer to the body and keep testicular temperatures from falling. , a fleshy pouch

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