In primates, and specifically in humans, the labia majora, also known as the outer lips or outer labia, are two prominent longitudinal skin folds that extend downward and backward from the mons pubis to the perineum. Together with the labia minora, they form the labia of the vulva.
The vas deferens, with the more modern name ductus deferens, is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube which exits the abdominal cavity through the inguinal canal.
The spermatic cord is the cord-like structure in males formed by the vas deferens and surrounding tissue that runs from the deep inguinal ring down to each testicle. Its serosal covering, the tunica vaginalis, is an extension of the peritoneum that passes through the transversalis fascia. Each testicle develops in the lower thoracic and upper lumbar region and migrates into the scrotum. During its descent it carries along with it the vas deferens, its vessels, nerves etc. There is one on each side.
The cremaster muscle is a paired structure made of thin layers of striated and smooth muscle that covers the testicles and the spermatic cord in human males. It consists of the lateral and medial parts. Cremaster is an involuntary muscle, responsible for the cremasteric reflex; a protective and physiologic superficial reflex of the testicles. The reflex raises and lowers the testicles in order to keep them protected. Along with the dartos muscle of the scrotum, it regulates testicular temperature, thus aiding the process of spermatogenesis.
The inguinal canal is a passage in the anterior abdominal wall on each side of the body which in males convey the spermatic cords and in females the round ligament of the uterus. The inguinal canals are larger and more prominent in males.
The cremasteric reflex is a superficial reflex observed in human males.
The genitofemoral nerve is a mixed branch of the lumbar plexus derived from anterior rami of L1-L2. It splits a genital branch and a femoral branch. It provides sensory innervation to the upper anterior thigh, as well as the skin of the anterior scrotum in males and mons pubis in females. It also provides motor innervation to the cremaster muscle.
The dartos fascia, dartos tunic or simply dartos is a layer of connective tissue found in the penile shaft, foreskin and scrotum. The penile portion is referred to as the superficial fascia of penis or the subcutaneous tissue of penis, while the scrotal part is the dartos proper. In addition to being continuous with itself between the scrotum and the penis, it is also continuous with Colles' fascia of the perineum and Scarpa's fascia of the abdomen.
The labia are the major externally visible portions of the vulva. In humans and other primates, there are two pairs of labia: the labia majora are large and thick folds of skin that cover the vulva's other parts while the labia minora are the inner folds of skin between the outer labia that surround and protect the opening. Inside the vestibule are the openings of the vagina and the urethra. Upward from the labia minora is the clitoral hood that protects the clitoral glans.
The lumbar plexus is a web of nerves in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve. Additionally, the ventral rami of the fourth lumbar nerve pass communicating branches, the lumbosacral trunk, to the sacral plexus. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.
The ilioinguinal nerve is a branch of the first lumbar nerve (L1). It separates from the first lumbar nerve along with the larger iliohypogastric nerve. It emerges from the lateral border of the psoas major just inferior to the iliohypogastric, and passes obliquely across the quadratus lumborum and iliacus. The ilioinguinal nerve then perforates the transversus abdominis near the anterior part of the iliac crest, and communicates with the iliohypogastric nerve between the transversus and the internal oblique muscle.
The perineal nerve is a nerve of the pelvis. It arises from the pudendal nerve in the pudendal canal. It gives superficial branches to the skin, and a deep branch to muscles. It supplies the skin and muscles of the perineum. Its latency is tested with electrodes.
The transversalis fascia is the fascial lining of the anterolateral abdominal wall situated between the inner surface of the transverse abdominal muscle, and the preperitoneal fascia. It is directly continuous with the iliac fascia, the internal spermatic fascia, and pelvic fascia.
The labioscrotal swellings are paired structures in the human embryo that represent the final stage of development of the caudal end of the external genitals before sexual differentiation. In both males and females, the two swellings merge:
The fascia of Scarpa is the deep membranous layer (stratum membranosum) of the superficial fascia of the abdomen. It is a layer of the anterior abdominal wall. It is found deep to the fascia of Camper and superficial to the external oblique muscle.
The testicular artery is a branch of the abdominal aorta that supplies blood to the testis. It is a paired artery, with one for each of the testes.
The cremasteric artery is a branch of the inferior epigastric artery which accompanies the spermatic cord to supply the cremaster muscle as well as other coverings of the spermatic cord in the male.
The cremasteric fascia is a fascia in the scrotum. As the cremaster descends, it forms a series of loops which differ in thickness and length in different subjects. At the upper part of the cord the loops are short, but they become in succession longer and longer, the longest reaching down as low as the testis, where a few are inserted into the tunica vaginalis. These loops are united together by areolar tissue, and form a thin covering over the cord and testis, the cremasteric fascia.
In most terrestrial mammals, the scrotum or scrotal sac is a part of the external male genitalia located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. The scrotum contains the external spermatic fascia, testicles, epididymis, and ductus deferens. It is a distention of the perineum and carries some abdominal tissues into its cavity including the testicular artery, testicular vein, and pampiniform plexus. The perineal raphe is a small, vertical, slightly raised ridge of scrotal skin under which is found the scrotal septum. It appears as a thin longitudinal line that runs front to back over the entire scrotum. In humans, the scrotum becomes covered with pubic hair at puberty. The scrotum will usually tighten during penile erection and when exposed to cold temperatures. One testis is typically lower than the other to avoid compression in the event of an impact.
In mammals, the vulva consists of the external female genitalia. The human vulva includes the mons pubis, labia majora, labia minora, clitoris, vestibular bulbs, vulval vestibule, urinary meatus, the vaginal opening, hymen, and Bartholin's and Skene's vestibular glands. The urinary meatus is also included as it opens into the vulval vestibule. Other features of the vulva include the pudendal cleft, sebaceous glands, the urogenital triangle, and pubic hair. The vulva includes the entrance to the vagina, which leads to the uterus, and provides a double layer of protection for this by the folds of the outer and inner labia. Pelvic floor muscles support the structures of the vulva. Other muscles of the urogenital triangle also give support.
