Sterility (physiology)

Sterility is the physiological inability to effect sexual reproduction in a living thing, members of whose kind have been produced sexually. Sterility has a wide range of causes. It may be an inherited trait, as in the mule; or it may be acquired from the environment, for example through physical injury or disease, or by exposure to radiation.

Mechanisms of sterility

Sterility can be caused by different closely related species breeding and producing offspring, these animals are usually sterile due to different numbers of chromosomes from the two parents, causing an imbalance in the resulting offspring making it viable but not fertile, this is the case with the Mule. Sterility can also be caused by chromosomal differences within the patient, these individuals tend to be known as a genetic mosaics. Loss of part of a chromosome can also cause sterility due to nondisjunction. Sterility can also be caused by selective breeding, where the trait you are selecting for is closely linked to genes involved in sex determination or fertility, for example goats breed to be polled (hornless), this results in a high number of intersex individuals among the offspring, which are typically sterile.XX male syndrome is another cause of sterility, this is where the sexual determining factor on the Y chromosome (SRY) is transferred to the X chromosome due to an unequal crossing over, this gene indicated what gender the individual should be and causes the development of testes, causing the individual to be phenotypically male but genotypically female, the resulting individual is (information needed).

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Male reproductive system

The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction . These organs are located on the outside of the body and within the pelvis.

The main male sex organs are the penis and the testicles which produce semen and sperm, which, as part of sexual intercourse, fertilize an ovum in the female's body; the fertilized ovum (zygote) develops into a fetus, which is later born as an infant.

The corresponding system in females is the female reproductive system.

External genital organs

Penis

The penis is the male intromittent organ. It has a long shaft and an enlarged bulbous-shaped tip called the glans penis, which supports and is protected by the foreskin. When the male becomes sexually aroused, the penis becomes erect and ready for sexual activity. Erection occurs because sinuses within the erectile tissue of the penis become filled with blood. The arteries of the penis are dilated while the veins are compressed so that blood flows into the erectile cartilage under pressure.

Reproductive system

The reproductive system or genital system is a system of sex organs within an organism which work together for the purpose of sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.

Animals

In mammals, the major organs of the reproductive system include the external genitalia (penis and vulva) as well as a number of internal organs including the gamete producing gonads (testicles and ovaries). Diseases of the human reproductive system are very common and widespread, particularly communicable sexually transmitted diseases.

Most other vertebrate animals have generally similar reproductive systems consisting of gonads, ducts, and openings. However, there is a great diversity of physical adaptations as well as reproductive strategies in every group of vertebrates.