Biology Reproduction in female

Biology | Reproduction in female
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.


The structure of the human female genital system

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.


The structure of the human female genital system

d) Vagina:
* It is 7 cm muscular tube connect between the carvix and the genital opening.
* Vagina is lined with membranes secrete mucous fluid to be moist.
*It has folds to allow its expansion during birth.

The female sexual maturity
* At the age from 12 : 15 year the female reach the sexual maturity.
* A change takes place in the female reproductive system according to the activities of ovary and uterus.
* The ovary and uterus activities depend on the occurrence of fertilization and pregnancy, or non-pregnancy and the monthly bleeding which is called menstruation.


Study of T.S. in the ovary

* Menopause: At the age of 45- 50 year, when the ovaries become inactive, which decreasing the secretion of hormones and the uterine lining is wrinkled.

Study of T.S. in the ovary.
* The ovary consists of a group of cells in different stages and ovum inside Graafian follicle.
* When the Graafian follicle releases the mature ovum, it transformed into the corpus luteum


The human female genital system

1- Multiplication phase:
In the embryo stages, the primary germ cells (2N) divided by mitotic division to form a number of oogonia (2N).

b- The growth phase:
In the embryo stages the oogonia (2N) store an amount of food, increase in size and are transformed into primary oocyte (2N)


The human female genital system

c- Maturation phase:
* The primary oocyte (2N) is divided first miotic division into secondary oocyte and 1st poiar body, both of them will be haploid (N) and the oocyte is larger than the polar body.
* Then the secondary oocyte is divided second miotic devision giving an ovum and second polar body.
* The polar body is divided by miotic divission producing two polar bodies.
* The resultant is an ovum and three Polar bodies.


The human female genital system

* The ovum contains cytoplasm and nucleus, it is covered with a thin cellular coat its cells are held together by hyaluronic acid,
* The acrosomes of sperms secrete enzymes to dissolve this coat at the penetration position therefore; millions of sperms are required to penetrate the ovum.
Breeding cycle:
* The breeding cycle is the periods in the life of placental mammals, where the ovary becomes regularly active in the adult female.
* These cycles are periodic and coincide with the sexual function of mating and production.


The period cycles differs in various mammals.



* In human beings, it is known as the menstrual cycle.
* Atypical menstrual cycle is 28 days. The two ovaries alternate with each other to produce mature ovum.


The menstrual cycle

1- Phase of proliferation (10 days):
* The pituitary gland secretes the follicle-stimulating hormone (FSH) which stimulates the ovary to produce Graafian follicle.
* The ovum grows and mature inside this follicle within 10 days.
* The Graafian follicle secretes estrogen which stimulates the growth of the endometrium.


The human female genital system

2- Phase of ovulation( 14 days):
* This phase starts when the anterior lobe the pituitary gland secretes the luteinizing hormone (L.H.) which stimulates the ovum to liberate from the Graafian follicle and the Graafian follicle is transformed into the corpus luteum, which produces progesterone and estrogen.
* Progesterone and estrogen hormones act to increase the thickness of the endometrium, and its blood supply.


The human female genital system

3- Phase of menstruation (3-5 days):
* If the ovum is not fertilized the corpus luteum degenerates gradually.
* Therefore, the secretion of progesterone stops , so the endometrium degenerates and the blood vessels tear due to the successive contractions of the uterus, Thus menstrual bleeding takes place
* This lasts 3-5 days’ and a new cycle of the other ovary begins.


If the ovum is fertilized pregnanacy occures.

* The corpus luteum remains to secrete the progesterone and esrtogen.
* This inhibits ovulation, and thus the menstrual cycle stops till after birth.
* The corpus luteum reaches to its maximum growth at the end of the third month of pregnancy.
* The corpus luteum starts to degenerate during the fourth month, when the placenta that grows in the uterus takes over its function in secreting the progesterone.



1- It preserves the endometrium
2- It stimulates the mammary glands to develop gradually.
* Therefore, if the corpus luteum which secrete the progesterone is removed before the forth month, abortion occurs.



Fertilization
* It is the fusion of the male gamete (sperm) with the female gamete (ovum) to form the zygote, which divides forming the embryo.
* After the ovum is released in the 14th day from the menstruation, it will be ready for fertilization through 1-2 days.
* Fertilization takes place in the 1st third part of the fallopian tube.
* The number of sperms from 300 million to 500 million per ejaculation, many of them are lost during their journey to the ovum therefore the man is considered in fertile if the number of sperms is less than 20 millions.





Biology | Reproduction in female

The human female genital system

* The sperms share in secreting the hyaluronic enzyme which dissolves part of the ovum coat through which one sperm only(head & neck only) enters.
* The sperms can stay alive about 2:3 days inside the female genital system.
* After fertilization the ovum surrounds itself with a coat, that prevents the entrance of any other sperm.



* After one day, the zygote divided mitotically into 2 cells (two blastomeres) in the upper part of fallopian tube, & four cells in the next day.
* The rate of cellular division increases to form a small mass called morula.
* The morula is pushed by cilia and muscle contraction along the uterine tube until it reaches the uterus.
* At the end of the first week, the morula implanted in between the folds of endometrium.
* The endometrium rich with blood supply necessary for the development of embryo along the nine months of pregnancy.



The outer embryonic membrane is the chorion, & the inner is the amnion.

1- The amnion:
* It surrounds the embryo with a fluid to protect the embryo against shocks and dryness.

The umbilical cord
* The embryo is connected with the placenta by the umbilical cord, its length is about 70 cm its length increases to give more freedom for the motility of the embryo.
* The umbilical cord is a tissue rich in blood vessels that transfer digested food, vitamins, water, salts and oxygen from the placenta to the embryo’s intestine, and it transfers the excretory wastes and carbon dioxide from the embryo’s intestine to the placenta.

2- The chorion:It surrounds the amnion, to protect the embryo.


The three stages of embryonic development

1- The first stage: (the first three months of pregnancy)
* The nervous system and the heart start their development, the hands and eyes become differentiated, also the two sexes become differentiated and response to stimuli becomes established.
* In the 1st month, nervous system &heart start to develop.
* In the 6th week, the testes are developed.
* In the 12th week, the ovaries are developed.


The three stages of embryonic development

2- The second stage: (the middle three months)
* The development of the heart is completed & its beats can be heard.
* Ossification and support of the skeletal system takes place.
* The sense organs are completed and size growth increases.


The three stages of embryonic development

3- The last stage: (the last three months)
* The development of the brain is completed.
* The growth slows down
* The development of the other internal system is completed.
* In the ninth month, the placenta dissociates gradually, So, progesterone decrease and attachment between the foetus and uterus becomes loosened preparing for birth.


Labor

* Labor begins with series of contractions in the uterine wall until the foetus is expelled outside.
* The foetus get out from the body due to the contractions of the uterine wall
* The baby starts his life with a cry, which stimulates the respiratory system.
* The placenta separates from the uterine wall and moves outside the body then the umbilical cord is cut from the baby side.
* The food supply of the newborn changes into the mother’s milk by the action of pituitary hormone, which stimulates the production of milk in the mother's mammary glands.



* The suitable female age for pregnancy ranges between 18 and 35 years.
* If the age decreases or exceeds that range both the mother and the embryo will be subjected to serious problems, the possibility to produce deformed babies will increase.
* In addition, if the father is too old, similar results will occur to his babies.






The time integral of pregnancy

Means of contraceptive

1- The pills:
* They contain a combination of synthetic estrogen and synthetic progesterone hormones.
* Woman starts using them after the menstrual cycle & continues for 3 weeks
* These pills prevent pregnancy by inhibiting ovulation.

2- The intrauterine device (the coil):
* It is inserted into the uterus cavity to prevents the fertilized ovum to be implanted in the uterus.

3- Condom:
* It prevents the sperms from entering the vagina.

4- Surgical sterilization:
* In the woman by cut or tide the two fallopian tubes, so, fertilization does not occur for the ova produced by the ovary.
* in the man by cut or tide the van deferens ,separated from other structures , So, no sperms will come out.



* Usually, one baby is born in each birth.
* The twins are the most common.
* The international percentage of twins is once in about 86 births.
* Sometimes, multiple births take place reaching six babies in the same time but that is rare.

Types of twins
1- Identical (Monozygotic) twins
2- Fraternal (dizygotic) twins Identical (Monozygotic) twins
1) It results from the fertilization of one ovum by a single sperm.
2) The developing cells separate into two masses of cells, each form embryo.
3) The two embryos are identical genetically
4) They have one embryonic sac and mostly one placenta.
5) They have the same genetic characters as eye's color & blood group.
6) These twins may be born partially attached to each other in some place in the body.
(Siamese twins) which can be surgically separated in most cases.



Fraternal (dizygotic) twins
1) It results from the fertilization of two ova with two sperms ,
2) Each zygote developed into embryo.
3) The two embryos differ genetically from each other.
4) Each has its own embryonic sac and separate placenta .
5) They never exceed brothers of the same age.
6) No Siamese twins



Test tube babies
* A mature ovum is obtained from wife’s ovary and being fertilized externally with the husband’s semen inside test tube in a certain nutritive medium till reaches to the morula.
* Then it is reimplanted in the wife’s uterus to complete its embryonic development till birth.



* Experiments are carried on early embryonic stages of rabbits, mice.
* When the separated cells was cultured in a female uterus, each produce a complete individual.
* The embryo culture can be considered as asexual reproduction.
* In other experiment, two early embryos (8 cells stage) were removed from two different mice. The two embryos were cultured together in a nutritive medium, then they were pushed to fuse into single embryo. Then it was implanted in the uterus of another female mouse. It was developed and born normally; this newborn is produced from two mothers, two fathers besides the foster mother.



* Its new type of embryo culture was developed, in which very fine surgical instruments were used.
* Nuclei from amphibian (toad) embryonic cells at different stages of development were removed and transplanted into unfertilized amphibian (toad) eggs, whose nuclei had been removed or destroyed by radiation, normal development toke place giving individuals identical in characters to the individual from which the cultured nuclei were taken.
* This Experiment proves that, the nucleus of early embryonic cell is capable to direct the embryonic development in a manner similar to the zygote itself.
* Gamete banks are found in some European and American countries.
* These banks are store selected animal gametes especially those of cattle and horses to keep them available for reproduction till the time of need.
* The gametes are stored in a frozen liquid nitrogen condition (-120 °C) for up to 20 years, after that period they can be used in artificial fertilization, even after the death of the producer individuals or if some rare animal species are exposed to extinction.
* It is possible to separate the sperms with (X) chromosome from sperms with (Y) chromosome by laboratory means such as centrifugation or exposure to a limited electric field.
* This aims to apply such techniques first on cattle to produce only males for meat or females for reproduction and milk production as required by breeders.