4. THE MECHANISM OF THE REPRODUCTIVE SYSTEM
Reproductive System
Reproduction is the process that helps human species to survive. In humans the significant components are male and female. Both sexes have different reproductive organs.
1. MALE REPRODUCTIVE SYSTEM.
The male reproductive organs are outside the body and consist of the following significant parts:
1.1 Penis is the male copulatory organ. It is shaped like a cylinder around the pelvis region. It is composed of tight but soft and elastic tissue. Normally, the length of the penis is about 5– 6 cm and its radius are 2.5 cm. At the tip are many nerves and blood tubes nourishing it, so it is sensitive to touch. When a man becomes sexually aroused, the penis becomes erect and can double its normal size. It becomes erect because its erectile tissue is filled with blood. When the penis is erect, small glands in the urethra produce mucilage to help in lubrication and transport for the sperms.
1.2 Testis consists of the scrotum which holds and protects the testes. It is like dark rinkled thin skin. The scrotum hangs on a muscle and can be shrunk or flaccid depending on changes of the outside temperature. The reason for this is to regulate the temperature in the scrotum to be good for sperm production. A human male has two testicles producing sperms and androgens (testosterone). A testicle looks like a small egg and is 2 - 4 cm long. It weighs about 15 – 30 grams. Often, the left testicle is a slightly larger than the right one. Both testicles are hold in the scrotum.
The many small tubes winding in stacks in the testes are called seminiferous tubules. These tubules produce sperms and the male hormone. At the back of each testicle are many small winding tubes to temporarily keep the sperms until they mature. We call these small tubes ‚epididymis.
1.3 Vas deferens the two ducts are each about 30 cm long tubes and are connected to the epididymis. These tubes transport the sperms from the epididymis to the ejaculatory ducts.
1.4 Epididymis connects its testicle to its vas deferens. This tube looks like a half moon hanging from the rear of the testicle inside the scrotum. The upper part is bigger which is called Head or Caput then the Body or Corpus finally the Tail or CaudaIt is a single, narrow, tightly coiled tube. After the sperms have been produced, they will be stored and mature in this place before ejected through the urethra.
1.5 Prostate Gland looks similar to the betel nut covering the first part of the urethra under the bladder. The function of this gland is to secrete a slightly alkaline liquid, milky or white in appearance. This liquid will be mixed with the sperms and move to the urethra. The alkalinity of this liquid is able to neutralize the acidity of the vaginal tract to protect the sperms from being damaged by vaginal acidity and increasing the change of fertilization.
The male reproductive cells or sperms will be produced in the seminiferous tubules of the testes. Sperms look similar to tadpoles with a head, a midpiece, and a tail which is much smaller than the head. The long tail is used for moving. The sperm itself is about 0.05 mm long and many thousand times smaller than the ovum. After the sperms are produced in the seminiferous tubules, they will be kept in the epididymis until they are fully mature. In the meantime, the prostate gland and the other glands will produce certain liquids to feed the sperms and accumulate them to a certain quantity. Whenever men have an ejaculation, the sperms will move through the urethra and leave the body. This step is a natural decrease of the sperms in our body.
The head of the sperm is the place for the nucleus with the genetic material in it. On top of the head, there are enzymes used to penetrate the ovum wall for fertilization. The tail or flagellum is the part that propels the sperm forward.
2. FEMALE REPRODUCTIVE SYSTEM
Most female sexual organs are inside the body and consist of the following parts:
2.1 Vagina is at the bottom of the abdomen. It is a muscular tubular tract of 5 – 7 cm in length. The front wall of the vagina is connected to the bladder. The back wall is connected to the end of the large intestine, near the anus. There are a lot of nerves within the vagina especially at the open end of it. The open end of the urethra a little above the vagina.
2.2 Clitoris is a small button at the open end of the vagina. It resembles a penis except that the urethra does not pass through the clitoris like it does in a penis. There are a lot of blood tubes and nerves feeding the clitoris which is flexible and sensitive for sexual stimulus comparable to the penis.
2.3 Uterus is a muscular organ building a cavity with thick wall. It is located inside the pelvis between the urinary bladder and at the end of the rectum. The ovum moves down along the ovarian duct into the uterus cavity and if the ovum has been fertilized, the embryo will settle in the thick uterus wall. There is a lot of blood feeding the embryo here.
2.4 Ovary. The ovaries are 2 glands in the cavity of the pelvic. They are of a rather small round shape and weigh about 2 - 3 grams. During embryonic development, each of the ovaries will grow in the abdominal cavity and after birth will move down to the pelvis. The ovaries produce the female hormones estrogen and progesterone.
2.5 Fallopian Tube. After the ovum matured in the follicle, it will move into the fallopian tube. Each fallopian tube is about 6 -7 cm long. The end closes the ovary is shaped like a cone. The other end of the tube is linked to the uterus. These tubes transport the ovum to the uterus. The egg is caught by the fimbriated end of the tube and travels down the fallopian tube towards the urerus aided by the activity of the tubal muscle.
Female Reproductive Cells or ova are produced by the ovary. An ovum begins to mature by stimulation with the pituitary gland hormone to become ready for reproduction. Each ovary will take turns producing only one ovum every 28 -30 days. After the ovum has matured in the ovary, it will move into the fallopian tube. During this time, more blood is circulated in the endometrium of the uterus wall readying to receive the fertilized ovum which will be immersed in the endometrium and grow into an embryo and into a fetus until childbirth. If the ovum has not been fertilized, it will be disposed together with the endometrium and blood. This process is called menstruation.