Biology Reproduction in human beings

Biology | Reproduction in human beings
The Male Genital System:

* Man belongs to class mammalia in which the embryo develops inside the uterus till birth.
* The human ova are small and nearly devoid of yolk.
* The number of offspring is few, due to parental care.
* Man shows a high degree of care, because young’s requires several years of raising.
* God provide man mental progress to be superior over other creatures.



The Male Genital System:
The structure of male reproductive system
* It consists of two testes, each testis leads a group of tubules called epididymis which connected to the vasdeferens that lead to urethera, male reproductive system contains accessory glands.



The structure of Male Genital System:
a) The two testes:
* The testis lies outside the body in the scrotal sac.
* The embryo testis descend down into the scrotal sac during the last months of pregnancy such a position prepares a condition cooler than the body temperature to be suitable for spermatogenesis (production of sperms).

* Whenever a testis fails to descend down into the scrotum, spermatogenesis does not occur, causing infertility (sterility).

The importance of the testis:
1. The production of sperms.
2. The secretion of testosterone hormone, which causes the male secondary sexual character.



The structure of Male Genital System:
b) The two epididymis:
Each testis leads to a group of cumulated tubes called epididymis, which fuses with the vas deferens.

c) The two-vas deferenses:
Each vas deferens transports sperms from the epididymis to the seminal vesicle.

d) The two seminal vesicles:
In which the sperms are stored until they leave the body.

e) Prostate gland and Cowper’s glands:
1- They secrete a sugary fluid (which feed sperms)
2- They secrete an alkaline fluid to neutralize the acidity of the urethra just before the sperms, because the neutral medium suits of the sperms.

f) The penis:
* It is an organ consists of a fiber tissue, through which the urethra passes.
* Each of the urine and the sperms pass through the urethra individually.



The Male Genital System:
The function of male reproductive system
1- Production of sperms
2- Secretes male hormones to develop the secondary sex characters.

Male secondary sexual characters
1- The voice becomes deep
2- Muscles grow stronger
3- Growth of facial hair.



The Male Genital System:
Study of a T.S. of testis:
* The testis is built up of seminiferous tubules among them these are interstitial cells which secrete the testosterone hormone.
* Inside each tubule these are sertoli cells which secrete fluid to feed the sperms inside the testis.
* It is supposed that, they gave also immunization function.
* Each tubule is lined internally with primary germ cells (diploid) (2N) they are divided to form sperms.


Biology | Reproduction in human beings



Phases of spermatogenesis
1) Multiplication phase:
* The primary germ cells(2N) are divided by mitosis several times to produce a great number of spermatogonia cells (2N) .

2) Growth phase:

* The spermatogonia cells store an amount of food to change into primary spermatocytes.



Phases of spermatogenesis

3) Maturation phase:
* The primary spermatocytes (2N) are divided by meiosis (1) to produce secondary spermatocytes (N) which are divided by meiosis (2) to produce spermatids (1N)

4) Metamorphosis phase:
* The spermatids are converted into sperms.
Structure of sperm
* It consists of head, neck, midpiece & tail

a) The head:
* It contains nucleus {(1N) = 23 chromosomes} & acrosome
The function of acrosome
* It secretes the hyaluronic enzyme that dissolves a part of the ovum membrane, to facilitate its penetration process.

b) The neck:
* It contains two centrioles, which play an important role in the division of the fertilized ovum.

c) The midpiece:
* It contains mitochondria to energy for movement.

d) The tail
* It consists of an axis, which ends with caudal piece to help the sperm to move.



The Function of the human female genital system
Its Function
1- The production of mature ova
2- The secretion of famale sex hormones.
3- Providing a safe place for fertilization.
4- Providing a safe place for embryo dvelopment till birth .



The number of mature ova
* During childhood, each ovary contains several thousands of ova in different
development stages of.
* After maturity about 400 only will mature
* They consumed during 30 years (active reproductive life =fecundity years)
* The ovaries are alternated the production of one mature ovum each month. * It secretes the maturation hormones for regulating menstrual cycle and embryo development.
* The organs of this system lie behind the urinary bladder and connected the with the pelvic region by elastic ligaments.
* The pelvic region is expansion during pregnancy.



The structure of the human female genital system
Its structure
* It consists of two ovaries, two oviducts, the uterus and the vagina

a) The two ovaries:
* Each ovary has an oval shape equals in size a peeled almond
* They lie on the sides of the pelvic cavity.

b) The two fallopian tubes (oviducts):
* Each Fallopian tube has a funnel shaped opening facing one of the to ovaries to insure the fall of ovum in it.
* Each Fallopian tube is provided with finger like protrusions and cilia to direct the received ovum toward the uterus.



c) Uterus:
* It is an elastic muscular sac-like organ.
* It lies in the pelvic cavity.
* It has a thick muscular strong wall, lined with a glandular membrane.
* The uterus is ended with the cervix which opens to the vagina.
* The embryo is formed inside the uterus for nine months.