Male reproductive system Flashcards
The HPG axis and testosterone
The HPG axis stands for the Hypothalamic-Pituitary-Gonadal axis, which is a complex system that regulates the production and release of sex hormones in both men and women.
In males, the HPG axis plays a crucial role in the production of testosterone, the primary male sex hormone. The hypothalamus, which is located in the brain, releases gonadotropin-releasing hormone (GnRH) into the bloodstream, which stimulates the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
LH then travels to the testes, where it stimulates the production of testosterone by the Leydig cells. Testosterone is responsible for a wide range of male characteristics, including the development of the male reproductive system, the growth of body and facial hair, and the deepening of the voice.
The levels of testosterone in the body are tightly regulated by a feedback loop involving the hypothalamus and the pituitary gland. When testosterone levels rise, they send a signal to the hypothalamus to reduce the production of GnRH, which in turn reduces the production of LH and FSH, ultimately leading to a decrease in testosterone production.
Abnormalities in the HPG axis can lead to hormonal imbalances, such as low testosterone levels, which can cause a variety of symptoms, including decreased libido, erectile dysfunction, fatigue, muscle weakness, and decreased bone density. Hormone replacement therapy or other medical treatments may be used to correct these imbalances.
explain Spermatogenesis and its control
Spermatogenesis is the process by which male germ cells, called spermatogonia, divide and differentiate into mature sperm cells. It occurs in the testes and involves several stages of cell division and maturation.
The process of spermatogenesis is regulated by a complex interplay of hormones and growth factors. The hypothalamus in the brain releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones travel to the testes, where they regulate the production of testosterone and other growth factors that are necessary for spermatogenesis.
The process of spermatogenesis can be divided into three main stages:
The proliferative stage: This is the initial phase of spermatogenesis, in which spermatogonia divide repeatedly to produce more cells.
The meiotic stage: During this stage, the cells undergo two rounds of meiotic division, resulting in four haploid cells (spermatids) from each original spermatogonium.
The maturation stage: The spermatids undergo a process called spermiogenesis, during which they differentiate into mature sperm cells. This involves the development of a tail for motility, the formation of a head containing the genetic material, and the formation of an acrosome, which helps the sperm penetrate the egg during fertilization.
The entire process of spermatogenesis takes about 64-72 days to complete. Sperm cells are then released from the testes and stored in the epididymis until they are ejaculated during sexual intercourse.
Sperm journey: production to fertilisation
Spermatogenesis: This is the process of sperm cell production that occurs in the testes. As mentioned in the previous answer, spermatogonia divide and differentiate into mature sperm cells through a process of meiosis.
Maturation: The sperm cells that are produced in the testes are immature and must undergo a process of maturation. This occurs in the epididymis, a coiled tube that is located on the outside of each testis. During maturation, the sperm gain the ability to move and become more resilient to the stresses of the female reproductive tract.
Ejaculation: The mature sperm cells are stored in the epididymis until they are ejaculated from the penis during sexual intercourse. Ejaculation is triggered by the stimulation of the penis during sexual arousal.
Transportation: Once the sperm are ejaculated, they enter the female reproductive tract. They must then navigate their way through the cervix and into the uterus, where they can encounter the egg.
Fertilization: If a sperm cell successfully penetrates the egg, fertilization occurs. This typically takes place in the fallopian tubes, which are narrow tubes that connect the ovaries to the uterus. Once the egg is fertilized, it begins to divide and travel down the fallopian tube towards the uterus.
Abnormalities of spermatogenesis
Azoospermia: A condition in which there are no sperm in the semen. This can be caused by problems with sperm production or blockages in the reproductive tract.
Oligospermia: A condition in which there are too few sperm in the semen. This can be caused by a variety of factors, including hormonal imbalances, genetic defects, or exposure to toxins.
Teratospermia: A condition in which the sperm have abnormal morphology or shape. This can be caused by genetic defects or environmental factors.
Asthenospermia: A condition in which the sperm have reduced motility or movement. This can be caused by genetic defects, hormonal imbalances, or exposure to toxins.
Spermatocytic arrest: A condition in which the sperm cells stop developing at a certain stage, leading to a lack of mature sperm in the semen. This can be caused by genetic defects or exposure to toxins.
Aneuploidy: A condition in which there are abnormal numbers of chromosomes in the sperm cells. This can lead to genetic disorders in offspring.
