أحياء لغات -Reproduction in Human2 للصف الثالث الثانوى 2016
كاتب الموضوع
رسالة
هنا جلال المدير
عدد المساهمات : 24470 نقاط : 64474 السٌّمعَة : 8 تاريخ التسجيل : 18/12/2012
موضوع: أحياء لغات -Reproduction in Human2 للصف الثالث الثانوى 2016 الإثنين يناير 11, 2016 4:58 pm
أحياء لغات -Reproduction in Human2 للصف الثالث الثانوى 2016
The plant has different types of supporting cells
The production of mature ova
.The secretion of famale sex hormones
.Providing a safe place for fertilization
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*
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 pelvic region by elastic ligaments. Thepelvic 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 three Stages of oogenesis
:a) 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
: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 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
:(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
:(Phase of ovulation( 14 days
This phase starts when the anterior lobe of 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
:(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
The corpus luteum
.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
The function of Progesterone
.It preserves the endometrium
.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 infertile if the number of sperms is less than 20 millions
Fertilization
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
Pregnancy and embryonic development
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
Embryonic membranes
.The outer embryonic membrane is the chorion, & the inner is the amnion
: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
:The chorion
.It surrounds the amnion, to protect the embryo
The placenta
Finger – like projections grow from the chorion membrane to be inserted in the endometrium, in which the capillaries of both embryo and mother touch
:The importance of placenta
It transfers digested food, water, oxygen and vitamins from mother’s blood to the embryo’s blood by diffusion and gets rid of the embryo’s excretory wastes
It secretes the progesterone hormone at the beginning of 4th month of pregnancy where the corpus luteum degenerates and placenta becomes the source of the p progesterone H
It also transfers the drugs, harmful substances such
as alcohol, nicotine, virures from mother’s blood to
the embryo which causes great harms, deformities
and diseases to the embryo
The three stages of embryonic development
:(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 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 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 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
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
:The pills
They contain a combination of synthetic estrogen and synthetic progesterone hormones. Woman starts using them after the menstrual cycle & continues for 3weeks These pills prevent pregnancy by inhibiting ovulation.
:(The intrauterine device (the coil
.It is inserted into the uterus cavity to prevents the fertilized ovum to be implanted in the uterus
.Condom: It prevents the sperms from entering the vagina
: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 vandeferens ,separated from other structures , So, no sperms will come out
:Multiple Birth
.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
.Identical (Monozygotic) twins
.Fraternal (dizygotic) twins
Identical (Monozygotic) twins
.It results from the fertilization of one ovum by a single sperm
.The developing cells separate into two masses of cells, each form embryo
.The two embryos are identical genetically
.They have one embryonic sac and mostly one placenta
.They have the same genetic characters as eye’s color & blood group
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
,It results from the fertilization of two ova with two sperms
.Each zygote developed into embryo
.The two embryos differ genetically from each other
.Each has its own embryonic sac and separate placenta
.They never exceed brothers of the same age
.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
:The embryo culture
.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
Renucleation
.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
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
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أحياء لغات -Reproduction in Human2 للصف الثالث الثانوى 2016
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موضوع: أحياء لغات -Reproduction in Human2 للصف الثالث الثانوى 2016 
