Reproduction in Humans, Structure of Male & Female reproductive (genital) system
Humans reproduce sexually when two different persons mate, the male (♂) and the female (♀) using a special system called the reproductive (genital) system, Man can’t reproduce asexually but he only reproduces sexually because the individuals (offspring) coming from asexual reproduction are identical to the parent, while in humans each individual differs from others.
Reproduction in Humans
Male reproductive (genital) system
The male reproductive system consists of 4 main parts which are:
- Two testes.
- Two vas deferens.
- Associated glands.
They are two glands of oval (elliptical) shape. They locate outside the body in a sac-like structure called scrotal sac (scrotum) which is hanged between male’s thighs.
Function of two testes
- Production of sperms (male gametes).
- Production of male sex hormone known as “testosterone” which is responsible for the appearance of secondary male sex characters (signs of puberty in male).
Function of the scrotal sac
Signs of puberty in male
- Growth of hair in certain body areas (like beard and mustache).
- Harshness of voice.
- Growth of bones.
- Growth and development of genital organs.
- Enlargement of muscles.
The testes of the elephant are present inside the body cavity. That’s why it is surrounded by a cooling system that preserves the optimum temperature for the testes to function efficiently and produce healthy sperms.
The vas deferens
Each testis is connected to a group of fine convoluted (highly looped) tubes known as “Epididymis” which extends in the form of a single tube known as “Vas deferens”.
Function of epididymis
Function of vas deferens
It transfers the sperms from the testes to the urinary genital duct (urethra). If the two vas deferens were cut, The sperms can’t transfer from the testes to the urinary genital duct and the individual becomes infertile.
Genital associated glands
There are three kinds of genital glands connected to the male reproductive system, which are:
- Two seminal vesicles.
- Prostate gland.
- Two Cowper’s glands.
Function of genital associated glands
They pour secretions on the sperms to form an alkaline fluid known as seminal fluid.
Function of seminal fluid
- Nourishes (feeds) the sperms (as it contains nutrients).
- Facilitates the flow of sperms.
- Neutralizes the acidity of the urethra (so sperms don’t die during passing through the urethra).
When the sex glands can’t secrete the semen. The sperms die, so the individual becomes infertile (sterile). The sperms don’t die during their passage through the urethra because the seminal fluid neutralizes the acidity of the urethra.
The prostate is a muscular gland surrounding the urethra at the site of connection with the urinary bladder and it might be enlarged in some men above forty years. This leads to increase pressure on the urethra which eventually causes difficulty in urination, and needs to be removed surgically.
It is a sponge-like tissue, the urethra passes through it and ends in a urinary genital (urinogenital) opening.
Through which the semen and urine go out of the body through the urinogenital opening but never at the same time.
The reasons that lead to the occurrence of sterility (infertility) in the male hu being are:
- The testes don’t come out of the body cavity during the development of the embryo.
- Occurrence of a cut in the two vas deferens.
- Inability of sex glands to secrete the seminal fluid.
Female reproductive (genital) system
The genital system in a female differs from that in a male in several aspects, mostly in being adapted to carry the embryo during the period of pregnancy. The female reproductive system consists of 4 main parts, which are:
They are two glands having the size and shape of a peeled almond. They locate inside the body in the lower part of the abdominal cavity from the back.
- Production of ova (female gametes), in a process known as ovulation.
- Production of female sex hormones, which are:
- Progesterone, which is responsible for the continuity of pregnancy.
- Estrogen, which is responsible for the appearance of secondary female sex characters (signs of puberty in females).
Signs of puberty in female
- Growth of hair in armpit and pubic.
- Softness of voice.
- Growth and development of breasts.
- Accumulation of fats in some body regions.
- Occurrence of the menstrual cycle.
It is one of the signs of puberty in females. It repeats every 28 days, as long as no pregnancy happens, It starts at the age of female puberty (11 to 14 years) and stops at the age of menopause (45 to 55 years). Female menopause is the age at which the two ovaries completely stop releasing ova.
Two fallopian tubes
They are two tubes of funnel-shaped opening provided with finger-like projections, The inner wall of fallopian tubes is lined with cilia. The two fallopian tubes are located near the ovaries and end at the upper corners of the uterus.
They receive (trap) the ripe ovum and direct it towards the uterus with the aid of:
- The contraction and relaxation of the muscles in the tube wall.
- The movement of the lining cilia.
Fallopian tube starts with a funnel-shaped opening provided with finger-like projections to receive the ripe ovum from the ovary by the finger-like projections and push it towards the uterus through the movement of cilia. The inner wall of the fallopian tubes is ciliated to direct the ripe ovum towards the uterus.
The uterus (womb)
It is a hollow pear-shaped organ. It has a muscular wall that can expand as the fetus grows during pregnancy. It is lined with a mucus membrane rich in blood capillaries to form the placenta during the pregnancy. It locates in the pelvic cavity between the urinary bladder and the rectum.
- It protects the fetus until birth.
- It nourishes the fetus during the pregnancy by the placenta through the umbilical cord.
It is a muscular tube that expands during labour. It extends from the uterus and ends in the external genital opening.
It expands during labour to deliver (coming out) the baby.