What is the structure of testis? Information on testis and its functions for reproduction. Size and Growth, Position and Temperature Regulation
Testis; the male gonad, or reproductive organ, which produces both sperm cells and male sex hormones (androgens). Testes are found in all animals that reproduce sexually. Some lower animals, such as earthworms, have both male and female gonads.
In humans, the testes descend from the abdominal cavity into the scrotum before birth. This prenatal descent also occurs in monkeys, goats, pigs, sheep, horses, and bulls. In other mammals, such as rats, the testes descend right after birth, and in elephants, stags, and some rodents they descend at the mating season. In fish, amphibians, reptiles, and birds, the testes are normally located in the abdominal cavity.
The human testis is composed of seminiferous tuhules, whose development during adolescence is stimulated by a hormone from the anterior pituitary gland, and interstitial, or Leydig, cells, which when stimulated by another pituitary hormone produce androgens, the most important of which is probably testosterone. Spermatogenesis, the formation of sperm cells, occurs in the seminiferous tubules. The mature sperm are stored in the epididymis and are discharged along with other substances through the ureter during ejaculation.
Size and Growth
During puberty, the testes grow to initiate spermatogenesis . Its size depends on sperm production (amount of spermatogenesis being done in the testes), interstitial fluid , and fluid production from Sertoli cells .
After puberty , the volume of the testes can be increased by up to 500% compared to the size before puberty.
The function of the testes, similar to the ovaries (in women) is the production of the cells responsible for fertilization , the sperm, in addition to the production of sperm , the testes are also the main responsible for the production of male hormones, from which testosterone stands out . These control the development of some characteristics of the man from which they stand out, the growth of hair, as well as the voice, beard , width of bones or muscle development.
It is more common for one testicle to hang a little lower than the other. The percentage of men with the lowest left testicle and the lowest right testicle is practically the same. This is due to differences in vascular anatomical structure on the left and right sides.
In terrestrial mammals the testes are located outside the body, suspended by the spermatic cord, inside the scrotum . This allows for more efficient spermatogenesis in mammals, due to the fact that the enzymatic activity of spermatogenesis has an optimal temperature, about 1 °C lower than the body temperature, which is 37 °C in humans.
The cremasteric muscle forms part of the spermatic cord . When this muscle contracts, the cord is shortened and the testicle is moved towards the body, which provides a warm-up that is very important for maintaining optimal temperature. When cooling is needed, the cremasteric muscle relaxes and the testicle is lowered and thus moves away from body heat. This phenomenon is called the cremasteric reflex . It also occurs in response to stress (the testes rise towards the body in order to protect the body in a fight), and there are also several reports that its relaxation indicates an approach to orgasm .. There is also a strong tendency for the muscle to contract and thus the testicle to retract during orgasm.
The testes can also be lifted voluntarily using the pubococcygeus muscle , which partially activates related muscles.
Many animals that have a low body temperature, such as elephants and rhinos , do not have external scrotal sacs; his testicles remaining inside the abdomen.
In the dolphin , as a matter of hydrodynamics, the testes are also located inside the abdominal cavity, but to resolve the issue of temperature, there is a slight change in the blood flow in male dolphins, as the blood before going to the testes, goes first to the dorsal fin. where it is slightly cooled and thus the temperature of the testicles is kept lower than that of the rest of the body.
Other non-mammalian animals do not have externalized testes. Birds , for example, have internal testes. It is theorized that these animals use their air sac to cool the testicles, but this theory has not yet been definitively proven.