Lectures on fertilization, implantation and development of eggs

2021-03-21 12:00 AM

The sex of the fetus is determined immediately upon fertilization. If the sperm carries the Y chromosome, it develops into a male fetus. Conversely, if the sperm carries the sex chromosome X

Define

Fertilization is the combination of a male spermatogenic and a female gametocyte to form a new cell called an egg.

Conception is the fertilization and implantation of an egg.

Fertilization

Sperm

Structure: Each sperm consists of 3 parts, head, body and tail.

Biological features: The number of spermatozoa is 60 - 120 million / ml of semen, sperm length is 65 m m, the rate of ejaculation activity is over 80%, movement speed is 1.5-2. , 5mm / min, time to live in the vagina about 2 hours, in the cervix and fallopian tubes is 2-3 days, the rate of malformations is <10%.

The development of the sperm line.

The place where sperm is produced is testicles.

Mitochondria have 46 chromosomes. Mitosis of the first time (mitosis) into cytoplasm 1 (46 XY).

Mitosis of the second (mitotic mitosis) from cytoplasm 1 to cytoplasm 2 has 23 chromosomes, including two types 23, X and 23, Y.

Cell 2 further divides into pro-sperm and sperm type 23, X or 23, Y.

Oocyte

The place where the oocyte is produced in the ovary.

Biological features: The number of primitive oocysts in each baby girl's ovary at birth ranges from 1.2 million to 1.5 million. From puberty to menopause there are only 400-450 mature follicles and most atrophy.

Development of the oocyte line:

Oocyte divides the first time (mitotic mitosis) into oocyte 1. oocyte 1 divides the second time (mitotic mitosis) into oocyte 2 and poles 1 has 23, X). Oocyte 2 and poles 1 further divide into mature oocytes and poles 2.

Movement of sperm and ovule

Sperm moves from the vagina to the oviduct through self-movement. It takes 90 minutes to 2 hours to travel from the vagina up to 1/3 outside the tubes. Other factors of the female genital tract such as the posture of the uterus, cervical opening, cervical mucus, and the difference in pH of the vagina and cervix ... affect the ability to move. transfer of spermatozoa. The sperm count decreases during movement.

The ovule cannot move on its own. The oocyte moves by the contractile movement of the oviduct muscle and peristalsis of the villi on the surface of the oviduct mucosa. The movements of the ovarian muscle and the lining of the ovary tend to move from the speaker toward the uterus. There is also a fluid chamber in the abdomen that is always moving towards the speaker of the ovary, so it draws the ovule towards that.

Fertilization

Time of fertilization: 14th day of a 28-day menstrual cycle

Fertility position: the outer 1/3 of the oviduct

Fertilization process: The sperm and ovule meet. The tip of the sperm secretes the yeast that destroys the granulosa cell layer and passes through the inner membrane of the oocyte. When the tip of the sperm passes through the inner membrane, the inner membrane changes so that other sperm can no longer enter. Upon reaching the cytoplasm of the oocyte, the sperm tip is lost, the nucleus of the sperm is located in the cytoplasm of the oocyte. The nucleus of the sperm becomes the male protonin and the nucleus of the ovule becomes the female protonuclear. The male and female protagonists continue to grow separately, then move closer together and merge into one nucleus. A new cell is formed to develop into the fetus and its appendages, complete with a set of chromosomes (46) called an egg. Eggs develop and divide immediately.

The sex of the fetus is determined immediately upon fertilization. If the sperm carries the Y chromosome, it develops into a male fetus (46XY). Conversely, if the sperm carries the X sex chromosome, it will develop into a female fetus (46 XX).

Movement of eggs

Eggs move from the outer 1/3 of the ovary into the uterus to nest.

Movement time of eggs: 3-4 days. After being able to enter the uterus, the egg is free to live for 2-3 days before it can be implanted.

Mechanism of movement: Due to the peristalsis of the ovary, the activity of the ovary mucosa and the flow of fluid moving in the abdomen is directed from the ovary speaker to the uterus.

Factors influencing oviduct migration.

Estrogen increases the peristalsis of the oviduct so that the egg movement is faster. In contrast, progesterone reduces muscle tone, decreases ovarian motility, so the egg will move slowly.

The oviduct is too long or has a fracture due to sticking or extrinsic compression, and chronic inflammation causes the oviduct to become uneven, narrow - all of these causes obstructed egg movement. When the egg does not enter the uterus, it will implant outside the uterus leading to an ectopic pregnancy.

On the way to move from the third third of the ovary to the uterus, the egg divides immediately. From one cell, the egg first divides into two germ cells, then into four equal stem cells. At the third division, the egg formed 8 unequal germ cells, consisting of 4 small germ cells and 4 large germ cells. Small stem cells will develop into leaves, and large stem cells will develop into fetal leaves and later become a fetus.

Small germ cells grow rapidly, surrounded by large stem cells, forming mulberry embryos, with 16 to 32 cells. In the embryo gradually appears a small chamber containing fluid and push the cells aside to form a blastocyst.

During migration, the egg continues to divide but its size does not change. When entering the uterus of the uterus at the blastocyst stage and remaining free 2-3 days before implantation.

The nesting of the eggs

Eggs start to nest from 6-8 after fertilization, the nesting time lasts 7-10 days, ending the nesting process on 13-14 after fertilization.

The nesting site of the egg is usually there in the uterus. If the eggs are implanted in low positions, especially close to the waist of the uterus, they will become the striker vegetables.

The lining of the uterus as an egg moves into the uterus is at its most fully developed stage in preparation for implantation (the stage of conception).

The implantation process: the blastocyst sticks to the lining of the uterus, the artificial legs of the leaves stick to the mucosa, called the rooting phenomenon. The cells of the cultured leaf destroy the epithelium of the uterus and blastocysts that penetrates deep through the epithelium. Days 9-10, blastocysts penetrate the cylindrical epithelium but not deep in the buffer layer, the surface is not covered. Days 11 - 12 blastocysts are completely in the buffer layer. Day 13-14 developed an epithelial layer covering the nesting egg site.

Development of the egg and its appendages

Phase division

Two phases or two periods:

The staging period starts from the time of fertilization until the end of the second month (the first 8 weeks).

Organization completion period: From the 3rd month to the full month.

Organizational period

Fetus formation:

When entering the uterus of the uterus at the blastocyst stage. The large stem cells divide and develop into a fetus with two layers of the outer and inner fetal leaves. There is a gap between the two fetuses, which later develops into the middle fetus.

All parts of the fetal body are made up of these three fetuses. The external leaves form the skin and nervous system, the middle leaves form the muscular, skeletal system, the connective organization, the circulatory system, the urinary system ..., the inner leaves from the digestive and respiratory system.

The fetus develops quickly and curves to form the poles of the head and tail. The Head pole grows rapidly and large due to the formation and development of cerebral sacs, so the head is bent toward the abdomen. The newly developed fetus is a flat, three-layer plate that curls back to form a cylindrical tube, called embryo closure.

Development of the appendage:

Endometrium: Some cells of the outer fetal leaf in the back of the fetus dissolve to form a fluid chamber, the amniotic fluid. The wall of the amniotic chamber is the amniotic fluid. The amniotic fluid chamber is growing and gradually the fetus will lie completely in the amniotic chamber.

Mesenchymal: Small germ cells develop into the mesothelioma. The mesenchymal membrane has two layers, the synaptic layer and the Langhans cell layer. This period was the period of dense middle production or the comprehensive vegetable period.

Epidural: The lining of the uterus changes into the epithelium. There are 3 parts to epidermal hyperplasia: ovarian dysplasia, uterine hyperplasia and uterine hyperplasia - vegetables.

Complete period organized

The development of the fetus: The fetus is fully formed and continues to grow, develop and complete the fetal organization.

Development of the fetal appendage.

The endothelium is increasingly developing. The amniotic fluid chamber expands and surrounds the fetus.

Mesenchymal: The Mesothelioma develops only in the part of the egg that implants and combines with the extraplasia of the uterus - vegetables to form vegetable cakes. Vegetable spikes destroy the extracellular matrix and form blood vessels. In the blood vessels, there are two types of vegetable thorns, nutritious vegetable thorns and vegetable thorns. Other parts of the mesenchyma shrink into a thin film.

The ovarian and ectopic hyperplasia gradually shrinks and forms a membrane. Hyperplasia of the uterus - vegetables and a part of the mesothelioma develop into vegetable cakes to nourish the fetus.

The fetus performs its metabolism through the placenta circulatory system.