Fertilisation

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OVUM FORMATION

FERTILISATION 

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Is union of nuclei of sperm and ovum to produce zygote. Fertilisation occurs inside the fallopian tube Of the millions sperm only few hundreds will survive the journey to reach fallopian tube. From these, only one sperm is succeeds to fertilise the ovum. The woman is said to be pregnant. The secondary Oocyte will complete its meosis II from Metaphase II.

THE EARLY DEVELOPMENT OF A ZYGOTE

STAGES

EXPLANATION

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Fertilisation

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After 36 hours zygote is form . Begins to divide repeatedly by mitosis as it travel along the fallopian tube.

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Development of embryo.

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Blastocyst/ Blastula.

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Implantation.

Mitotic division repeatedly to form embryo with two cell, four, eight and the solid mass of cell call morula. The morula with about 100 cells. Its fluid-filled sphere. 

7 days after fertilisation the blastula attaches itself to endometrium.  The inner cell mass develops into embryo. The trophoblast will develop into the foetal portion of placenta. 

FERTILISATION AND EARLY DEVELOPMENT OF THE EMBRYO

FETAL DEVELOPMENTS PHOTOS

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Eight Week Fetus All the major organs of your baby have formed now though they are not fully developed yet. Eyes and ears are growing now. The heart is beating strongly. When you have an ultrasound during this time, you can see the heart pulsating.

EIGHT WEEK FETUS (FOETUS)

Twelve Week Fetus Your baby is now about 6.5 cm long and weighs about 18 grams. His head is becoming more rounded and the face is completely formed. Toes and fingers are formed and nails are beginning to grow. The baby is moving it's limps but you can not feel this movements yet.

Sixteen Week Fetus Your baby is now about 16 cm long and weighs 35

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grams During a scan, you can see the baby's head and body and you may see the baby moving. It is exercising all his limbs, kicking and moving about. This is the earliest stage at which you may feel the baby moving. It feels like there is a butterfly in your belly.

Twenty Four Week Fetus The baby is about 32 cm long now and weighs 500 grams. You can feel different parts of the baby's body through your abdominal wall. Your uterine muscle is stretching and you may feel a pain sometimes at the side of your tummy. The top of your uterus reaches to just above your navel.

THE UMBILICAL CORD PHOTO Thirty Week Fetus Your baby's head is now in proportion with the rest of his body. You may feel pressure on your diaphragm, stomach and intestines. Your baby's weight is now about 1700 grams or three pounds eleven ounces and measures about 40 cm or 15.8 inches in length.

THIRTY WEEKS

Thirty Six Week Fetus The baby is almost fully mature. Any time now he may descend into your pelvis. Once the baby has engaged you may find that your breathing becomes easier and the pressure on your diaphragm is less. Your baby's skin is smooth now and his body has plumped out. When the baby is awake his eyes are open and he can differentiate between light and dark. Your baby is now about 50 cm long and weighs anywhere from 2500 to 4500 grams.

THE DIFFERENCES BETWEEN IDENTICAL AND FRATERNAL TWINS One ovum is fertilized by one spem to form zygote Zygote is splited into two separate embryos Both have same genetic

FERTILISATION

Two ova are realeased & fertilized by 2 sperm FORMATION OF Two zygote are form which divide ZYGOTE and develop into two separate embryos Genetic constitution Twins do not share the same genetic

Both share one placenta but they have their own umbilical cord

Number of Placentae

Both has its own placenta and umbilical cord

Same sex, either males or females

Sex

Both share the same physical

Physical Characteristic

Both can be same sex or different sexes Both do not share same physical

Siamese Twins Characteristic. 

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Siamese twins are identical twins which did not separate completely during embryonic development. They are attached at certain parts of the body such as head,chest, abdomen or hips. They may also share some common internal organs. They can be separate surgically and have a greater chance of survivalif do not share major organs like heart, brain or lungs.

PLACENTA 

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The placenta fully develops when 3 month after fertilisation. The trophoblast develops into chorion ( finger like projection) Blood vessel of chorion and mother , expand to form placenta. Placenta is connected to the foetus by the umbilical cord. Umbilical cord contain vein (oxygenated blood) & arteries(deoxygenated blood)

The Function of Placenta 

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Site of exchange of nutrients, respiratory gases, and waste between foetus and mother. Acts as endocrine gland secretes oestrogen and progesterone, it will stop secretion of FSH and LH. Umbilical veins carries Oxygen, water, glucose, amino acids, lipid, mineral & salts, vitamins, hormone & antibodies. Umbilical arteries carries Carbon dioide & nitrogenous waste (urea). Its provide partial protection to drugs, alcohol, caffein, nicotine but HIV and rubella virus able to penetrate.

THE ADVANTAGE OF FEOTUS HAVING SEPARATE CIRCULATORY SYSTEM FROM MOTHER. 

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Prevents certain harmful bacteria from entering foetus. Prevent mixing of blood group of mother which can cause agglutination. Prevents the action of chemical in mother’s blood from harming the foetus. Ensure the fine blood vessel not to burst as a result of high pressure caused by the flow of mothers blood.

CONTRIBUTION OF SCIENCE & TECHNOLOGY TO HUMAN REPRODUCTION

FAMILY PLANNING • Allows the spacing & timing of the birth of children • enables a couple to limit the family size • method : •Contraceptive drugs & devices or surgery •Prevent the release of gamete, prevent fertilisation or implantation.

INFERTILITY • This could be due to female or male partner being sterile. •Female : - damage in fallopian tube, uterus or cervix • Male : - low sperm count or impotence

TECHNIC TO OVERCOME INFERTILITY

• Artificial insemination - sperms are collected from the husband and inserted into the uterus of the wife during ovulation. • In vitro fertilisation (IVF)

- it takes place in laboratory glassware rather than inside the body. - some women have blocked or damaged fallopian tube cause sperms cannot reach fallopian tube - Treatment : • FSH is given to stimulate development large number of follicles • able to retrieve many eggs from ovaries in one operation. • eggs are then fertilised in glass dish. • later, embryos are injected in wife uterus to allow implantation • some cases, if embryos injected to other women, known as surrogate mother.

THE SEXUAL TRANSMITTED DISEASES (STDs) Definition

Disesases spread from one person to another through sexual contact. 

Caused

STDs

by bacteria: Chlamydia, Syphillis & Gonorrhea STDs by virus: Hepatitis B, Genital herpes ,AIDs Treatmen Bacteria STDs treated by antibiotics t but Viral STDs cannot. Avoided

Not

engaging in promiscuous sexual behaviour.

MALE & FEMALE STRUCTURE IN FLOWER

CROSS SECTION IN OVARY & ANTHER

FORMATION OF POLLEN GRAINS 

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Pollens (male gamete) are produced in anther. Each anther consists of four pollen sacs. Each pollen sac are hundreds of pollen mother cells. Each pollen mother cell undergoes meiosis to produced four haploid cells or microspores (n) The nucleus of each microspore (n) divides by motosis to form two nuclei, the tube nucleus and generatives nucleus ( later form 2 male gamete)

Formation Of Pollen Grains

TETRAD MICROSPORE (N)