The male internal genitalia include the testes, epididymis, vas deferens, ejaculatory ducts, prostate, seminal vesicle and urethral bulb glands.
I. Testes
The testes are male reproductive glands, one on each side, oval-shaped, suspended in the scrotum by the spermatic cord, about 4-5 cm long, 3-4 cm thick, and weighing about 15 g each. It is the organ that produces male germ cells (i.e. sperm) and is also the main endocrine gland that produces androgens.
Internal structure of the testes: The testes have a thick dense connective tissue membrane on the surface, called the white membrane. The inner side of the white membrane is loose connective tissue with abundant blood vessels, called the vascular membrane. The white membrane of the testis thickens on its dorsal side and plunges into the testis, forming the longitudinal septum of the testis. The mediastinum extends radially into the testicular parenchyma and divides the testis into several lobules. Each lobe contains 1-3 curved seminiferous tubules, which converge at the tip of the lobe to become a short and straight straight seminiferous tubule that enters the mediastinum, where these tubules anastomose with each other to form a network, forming the testicular network, from which 12-13 curved tubules, called testicular output ducts, are ejected into the epididymal head.
The interstitial cells of the seminiferous tubules secrete androgens, which promote the development and maintenance of the male reproductive organs and male secondary sexual characteristics. The epithelial cells of the seminiferous tubules have the function of producing sperm. The seminiferous tubules combine with each other to form the straight seminiferous tubules, which are the pipeline system for sperm transport, and finally converge and form a single tube into the head of the epididymis and are discharged through the vas deferens.
Epididymis
The epididymis is formed by coiling the epididymal ducts at the posterior edge of the testes, with slender fibrous and honeycomb tissues between the tubules, and is divided into three parts: head, body and tail. The head of the testis is composed of the output duct, and the wall of the duct is composed of pseudo-complex columnar epithelium, containing two kinds of cells, one is ciliated columnar epithelium; the other is low columnar secretory cells, and the cells are arranged in an interactive way, so the lumen of the duct is irregular and jagged. The body tail of epididymis is composed of epididymal duct, which is composed of pseudostratified columnar ciliated epithelium with the same height of epithelium, so the lumen of duct is regular.
The epididymis is elongated and flattened, and resembles a half-moon, one on each side, about 5 cm long, and is attached to the posterior side of the testis. The epididymis has the function of storing and discharging sperm, promoting sperm maturation and secreting fluid to supply sperm nutrition. The above physiological functions are accomplished through the absorption, secretion and concentration functions of the epithelial cells of the epididymis.
3. Spermatic cord, vas deferens and ejaculatory duct
The spermatic cord: It is the garden cord between the upper end of the testis and the ventral ring of the inguinal canal. The spermatic cord starts from the inguinal ring and ends at the posterior edge of the testis, and is a flexible band that ties the testis and epididymis, one on each side, with a total length of about 14 cm. The spermatic cord contains vas deferens, arteries, veins, nerves and fovea. The arteries are testicular artery, vas deferens artery and levator muscle artery. The veins are trapezius plexus. The spermatic cord is the blood and lymphatic fluid circulation pathway of the testes, epididymis and vas deferens, and is also the main way to ensure the spermatogenic function of the testes and the transport of mature sperm.
The vas deferens is one of the major structures within the spermatic cord, starting at the tail of the epididymis and entering the pelvic cavity via the inguinal canal. The vas deferens travels between the ureter and the bladder towards the middle, and its end expands and expands to form the vas deferens potbelly, which finally joins the vas deferens. The end of the vas deferens merges with the excretory duct of the seminal vesicle gland to form the ejaculatory duct, which passes through the prostate and opens into the urethra. The vas deferens is the only way for sperm to be transported from the epididymis to the urethra of the prostate.
The ejaculatory duct is the continuation of the vas deferens and the seminal vesicle duct after their confluence. The ejaculatory duct is very short, only about 2cm long, and the wall is very thin.
Four, the seminal vesicle gland, prostate gland and urethral bulb gland
The seminal vesicle glands are a pair of flat, long, sac-like glands, one on each side, with an uneven, nodular surface, located on the outside of the end of the vas deferens and below the back of the bladder, with a small end for the excretory duct of the seminal vesicle gland, which converges with the end of the vas deferens to form the ejaculatory duct, which opens in the urethra at the prostatic part of the urethra. The seminal vesicles are about 4-5cm long, 2cm wide, and 4ml in volume, and are flexural glandular sacs that secrete mainly seminal fluid, accounting for about 70% of the seminal fluid and playing an important role in the survival of sperm.
The prostate gland is a chestnut-shaped gland with a sunken groove in the middle and a bulge on the left and right sides, with the bottom connected to the bladder and the tip down against the superior urogenital diaphragm. The prostate gland secretes prostatic fluid, mainly seminal fluid, which contains many trace elements and many enzymes. In the proximal part of the seminal frenulum, the smooth muscle is strengthened, called the anterior prostatic sphincter, which has the function of preventing retrograde ejaculation.
Urethral bulbous glands: one on each side, located in the deep perineal sac between the upper and lower fascia of the urogenital diaphragm, opening at the proximal end of the bulbous urethra. It can secrete a small amount of fluid, which is one of the components of seminal plasma.
V. Urethra
The male urethra has both the function of urination and seminal discharge. The urethra is about 12 to 20 cm long and contains the urethral bulb gland, which secretes fluid and participates in the composition of semen and lubricates the head of the penis during sexual intercourse.
The semen consists of sperm and fluid secreted by the seminal vesicle gland and prostate gland and is milky white. One ejaculation is about 2 to 3 ml and contains 300 to 500 million sperm.
The male external genitalia are the penis and scrotum
1.Penis
The penis is made up of three spongy bodies surrounded by fascia and skin. There are two penile corpus cavernosum and one urethral corpus cavernosum. It is divided into root, body and head. The root is fixed in the perineum, the front end of the penis is enlarged to form the head of the penis, the head and the body intersection is thin, the neck, is a ring-shaped groove, also known as the coronal groove. The urethral corpus cavernosum has the urethra passing through it and opening at the external urethral orifice.
The penis is cylindrical when not erect, about 7 to 9 cm long. when erect, it is trigonous and cylindrical, more than doubling in length, and its main function is to complete sexual intercourse. The outer skin of the penis is wrapped around the head of the penis and is called the penile foreskin. The special structure within the penile corpus cavernosum is an important tissue structure for the erectile function of the penis, and the erection of the penis is a prerequisite for the completion of sexual intercourse.
2.Scrotum
The scrotum is a pouch of skin located at the back of the penis. The skin of the scrotum is thin and soft, with a small amount of pubic hair and obvious pigmentation. The scrotal wall consists of skin and meatus. The sarcolemma contains smooth muscle fibers. The smooth muscle is reflexively contracted with the external temperature to regulate the temperature in the scrotum, which is conducive to the development of sperm. If the external temperature is high, the smooth muscle is diastolic, while when the external temperature is low, it is contracted. The sarcolemma sends out the scrotal septum deep in the median line to divide the scrotal cavity into two parts, the left and right, which accommodate the testes and epididymis on both sides respectively.