....................... REPRODUCTION I. HUMAN REPRODUCTIVE ORGANS

Introduction. We need to feed ourselves to keep us alive and we need to connect with the outside to get food. On the other hand, we do not need to reproduce to continue being alive. The reproduction is not for continue being alive but to generate new individuals of our specie who continue living when we're already dead. The human species has sexual reproduction with two types of individuals, of the male sex or men and of the female sex or women. Human's reproduction is possible only between two individuals of different sexes. Moreover, as our species lives out of the water and the male reproductive cells need to swim to get to the female reproductive cell, the man has a special reproductive organ capable of introducing the male cells in the female body and female also presents a special organ to facilitate the copulation and then the pregnancy. On the other hand, the existence of sexual pleasure, as also happens in feeding, is a factor that has developed during the evolution to significantly help with the ensurance that humans will reproduce and thereby endure the species. Those interesting topics are explained in this chapter.

Activities to do. Read the explanations on the male reproductive system and perform the first Multiple Choice Test and the first Relate Pictures with Names. Then read the text on the female reproductive system and perform the second Multiple Choice Test, the second Relate Pictures with Names and the Crossword.

1. The human reproduction. The reproduction is the generation of new individuals. The human reproduction is sexual because it is made from two different types of gametes, called the spermatozoon and the ovum, which unite inside the female body (internal fertilization) after the intercourse (coitus), which is the introduction of the male penis into the vagina of women. The formed cell, called zygote multiplies constantly (embryonic development), causing an embryo that is fed from the mother's body through an organ called placenta. Thanks to this, the new individual comes completely formed (viviparous). The human sexual reproduction is not only a mere physiological act, it also requires a context of affection and commitment between two people to become psychologically satisfactory to both. This is one of the characteristics of human sexuality.

2. The male reproductive system. It consists of two testes and two epididymis contained in a sack (scrotum), two ductus deferens ended in a dilation called "vas deferens blister", five connected glands (two seminal vesicles, two Cowper's glands and a prostate) contributing nutritious substances, and two ejaculatory ducts that lead to the urethra which runs inside the copulatory organ or penis. The scrotum allows that the testicles are at a lower temperature than the rest of the body, which is necessary for forming the spermatozoa (spermatogenesis).

The testicles are organs about 4 cm diameter. Within these organs there are long highly folded ducts called seminal ducts, inside of which the spermatozoa are generated. It also contains the Leydig cells that produce the testosterone hormone, which is responsible for male sexual characteristics (deep voice, beard, broad shoulders, etc). The epididymis are the spaces where spermatozoa are stored. The seminal vesicles secrete a nutrient fluid for the sperm. The prostate secretes the prostatic fluid, which stimulates the spermatozoa. It constitutes the major part of the liquid containing the spermatozoa, called semen or sperm. The Cowper's glands secrete a fluid that lubricates the urethra before departure of semen (ejaculation). The penis is the male copulatory organ. Inside it presents three cylinders of spongy tissue (2 corpus cavernosum above and 1 corpus spongiosum below), which upon excitation are filled with blood. This causes its erection and the increase of the size. The front end is called the glans. It is a very vascularized and sensitive zone that has an orifice called urinary orifice or urinary meatus. The glans is covered with a skin called foreskin which by removing allows the glans to emerge. Its excessive narrowness is called phimosis. The surgical operation to remove it is called circumcision.

3 . The physiology of the male reproductive system. The spermatozoa are made in the seminal ducts of the testes. Then they are being stored in a structure called epididymis. At the time of ejaculation the sperm travel through the vas deferens, the ejaculatory (which is only about 2 cm in length) and the urethra. During the route the adjacent glands secrete substances that constitute the liquid part of the semen. Approximately 3cm3 of semen is ejaculated with a concentration of the spermatozoa (100 millones/cm3).

4. The female reproductive system. It is formed by two ovaries, two fallopian tubes or oviducts which are two tubes with the free and dilated end, and able to collect the eggs produced by the ovaries, an organ of muscular and very expandable walls called womb or matrix, an elastic tube called vagina and two thick skin folds that close their entry and form the external female genitalia or vulva.

The ovaries have a length of about 3cm and are supported by the ligaments. The fallopian tubes are about 15cm in length and have extensions called fimbriae. The uterus is a sack of the reversed pear shape and about 6 to 9 cm long and 3 to 4cm wide. Within it the entry or neck and the rest or uterine corpus can be differentiated. The last one presents a very muscular walls and very vascularized mucous layer, the endometrium that each month seperates into parts (menstruation or period) and then it regenerates. The vagina is an elastic muscular canal about 8 to 12cm, able to take the penis during the intercourse. In the vulva or external female genitalia can be distinguished the following elements: the two labia majora (two thick folds of skin covered with hair), the two labia minora (two thin inner folds of skin), clitoris (little sensitive erectile organ) urethral orifice or meatus (the orifice from the urine exit) and the vaginal orifice (the oferice of the reproductive organ) which is partially closed by a membrane called the hymen, which is torn during the first intercourse.

5 . The physiology of the female reproductive system. Approximately every month, in one or other of the two ovaries, ovarian follicle matures and releases an egg. The remaining follicle becomes the white body or the albicans body and then heal. The egg enters the fallopian tube where it can unite with sperm if there has been a copulation. If the egg is not fertilized, after going through the fallopian tube, it passes the uterus and vagina and goes outside. After two weeks, as there is no embryo to receive, the uterine endometrium is removed (menstruation). Then it regenerates in just five days.

6. Standards of hygiene and prevention of diseases related to the reproductive system's organs. The reproductive organs have orificios that can be used by microbes to enter the body, and also have folds that can be used by little organisms to settle in. On the other hand, our reproductive systems produce secretions that can serve as a culture medium for microbes. Therefore, a daily intimate hygiene with soapy water is recommended. For men, running the foreskin and washing the glans and for women, separating the labia of the vulva. Systematically women, from the age of 40, should be going to the doctor at least once a year to get a gynecological observation, and men, from the age of 45, should be getting the follow-up on the state of the prostate. Furthermore, whenever there is some disturbance, such as a little lump in the breast or little difficulty in urination the medical appointment is recommended.

Crosswords (Spanish activity. Activity in English is under construction)