Testis, the plural is testes and it is the organ in the animal which produces the sperm, the male reproductive cell, and androgen is the male hormone. In humans, testes are oval-shaped organs that occur in the pair. Testes are present within the scrotal sac, and it is located directly behind the penis and in front of the anus. Testicles means the same as testes.
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Anatomy of the Testes
The physical property of each normal testis weighs about 25 grams which is equal to 0.875 ounces, four to five centimetre long (that is 1.6 - 2.0 inches), and two to three centimetre in diameter. Each of the testis is covered by a fibrous capsule called the tunica albuginea and it is further divided by partition of fibrous tissue from the tunica albuginea into 200 - 400 wedge-shaped lobes or sections. In each lobe there are 3 -10 coiled tubules known as seminiferous tubules, its function is to produce the sperm cells. The partition between both lobes and the seminiferous tubules converges in one area, near the anal side of each testis to form mediastinum testis.
Testes have the germ cells, which is differentiated into mature spermatozoa, Sertoli cells (they are the supporting cell), and Leydig (intestinal) cells (they are also known as testosterone-producing cells). The germ cell migrates to the fetal testes from the embryonic yolk sac, Sertoli cell is interspersed between the germinal epithelial cells within the seminiferous tubule, they are analogous to the granulosa cells in the ovary. The Leydig cell is located beneath the tunica albuginea, in the septal walls and between the tubules are analogous to the hormone-secreting interstitial cells of the ovary. The shape of Leydig cells are irregular and they commonly have more than one nucleus. These Leydig cells frequently contain fat droplets, pigment granules and the crystalline structure. These cells vary greatly in numbers and appearance among the various animal species and they are surrounded by blood, lymphatic vessels, and as well as by nerve fibres.
In primitive times the embryonic differentiation of indifferent gonads into either testes or the ovaries would be determined by the presence or absence of genes carried on the y chromosome.
The seminiferous tubule is one, where the sperms are produced and it constitutes about 90 percent of the testicular mass. In young male humans, the tubules are simple and composed of undeveloped sperm-producing cells called spermatogonia and the Sertoli cells. Once the young males grow the tubules become branched and spermatogonia are changed into fertile sperm cells and after a series of transformation, it is called spermatogenesis. Sertoli cells are present in both the young and matured males to support mechanically and protect the spermatogonia.
The spermatogonia in the tubules get matured into spermatocytes, further, it matures into spermatids and that matures into spermatozoa as they move into the central lumen of the seminiferous tubule. Spermatozoa are stored in the seminal vesicle moving through the epididymis and the spermatic duct for eventual ejaculation with the seminal fluid.
It is the condition of the testicular torsion, in which twisting of the spermatic cord takes place and it brings blood down to the scrotum. Due to the condition of twisted testicles, the reduced blood flow causes sudden often pain and swelling. This is most common in males of age 12 - 18, but it can occur at any stage of life.
In this condition, it requires emergency surgery, if treated on time testicles can be saved. For any reason, if blood flow is cut for too long, the testicle might become so badly damaged that it might have to be removed.
Interesting Facts About Testicles
Human testicles means testes produce nearly around 200 million sperms a day.
In real testis of human are not the same, one of the testis is always smaller when compared with the other one.
The human testicle is the organ in the human body, which contains more diverse protein than any other organ in the body.