Early Child Development

Early Child Development

There are many key factors that play up to the role of early child development, starting from before the child is nonexistent, until the child is a full grown baby.

Bodily Processes of Reproduction

There are numerous hormones in the human body that play key factors in allowing a human being to reproduce successfully.

Spermatogenesis

Spermatogenesis is the 65 to 75 day process in which the human male anatomy produces sperm cells. In the male body, follicle-stimulating hormones, or FSH, and leutinizing hormones, or LH, are very important in the process of spermatogenesis. These hormones control sperm reproduction. The production of the hormones testosterone and androgens are stimulated by the leutinizing hormones. During this process, the follicle-stimulating hormones motivate the testes to produce sperm. The development of the sperm takes place in twisted tubules called seminiferous tubules. Mitosis occurs, in which the diploid cells multiply themselves constantly. Then, day by day, at least 3 million of these cells begin to undergo meiosis, where the number of doubled chromosomes is reduced in half by dividing the cell over and over again. In order for the first phase of Meiosis to begin, the cell must become a primary spermatocyte. After this has occurred, the diploid cell, which has 46 chromosomes, split into two haploid secondary spermatocytes, each containing only 23 chromosomes. In the next phase of Meiosis, Meiosis II, the two cells split, again, forming four cells also consisting of 23 chromosomes, and the cell undergoes the change in order to perform its more specialized function for reproduction. This production takes place in the male gonads, also known as the testes.

Oogenesis

Oogenesis, also called ovigenesis, is the process in which the female anatomy produces egg cells. The egg cell is made up of three layers: a jelly coat, the vitelline layer, and the egg cell's plasma membrane. A hormone called gonadotropin releasing hormone, or GnRH, control the production of the follicle-stimulating hormones and the leutinizing hormones that, as stated above, are also found in the male body. The process of oogenesis is similar to spermatogenesis. Although produced by the leutinizing hormones, the androgen hormones control the levels of FSH, GnRH, as well as the LH. Oogenesis begins before birth. Each follicle in the uterus that all females are born with holds an undeveloped primary occyte. Similar to the primary spermatocyte, the primary oocyte is a diploid cell that has to divide into two haploid cells in order to complete Meiosis I. When puberty begins for females, the FSH arouses one of the undeveloped primary oocytes to develop. This causes the follicle to expand, completing Meiosis I. The difference between the Meiosis of the two processes, though, is that when the oocyte divides for Meiosis II, the amount of cytoplasm between the two daughter cells is imbalanced. The cell with the most cytoplasm is called the secondary oocyte. This is the cell that released in ovulation.

Fertilization

Fertilization is the outcome of the joining of a sperm cell and an egg cell to form what is called a diploid cell. A diploid cell is a cell that contains two sets of chromosomes that were inherited from each parent cell. The cell will eventually develop into another human being. It is a process that is a result of a series of events which happens in sexual reproduction. The hormones of the male and female body are what trigger the beginning of this process. Other than FHS, GnRH, and LH, the other hormones that help regulate the female cycle is estrogen and progesterone. The proliferate phase is the first half of a female's cycle in which the mucous membrane of the uterine wall thickens. The FSH causes ovaries to secrete estrogen and the follicle of the uterus to fully develop. Ovulation is caused by the hypothalamus secreting large amounts of GnRH by the increase of FSH. The follicle burst and the egg is released. This happens on about the 14th day of the average 28-day cycle. A corpus luteum, a mass of cells that secrete progesterone, are formed when the LH arouses the remaining follicles. The secretory phase and the luteal phase make up the second half of a female's cycle. In these phases, the endometrium is still thickening, setting up the uterus for a potential pregnancy. If the egg is not fertilized, the corpus luteum weakens and the level of the sex hormones progesterone and estrogen become low. The corpus luteum then begins to collapse and the production of the sex hormones come to a halt.

When a sperm cell is in the process of fertilization, it must first go through the three layers of the egg in order to reach the egg's nucleus. When the sperm comes in contact with the first layer, the acrosome, a sac containing enzymes designed to aid in egg penetration, releases the enzyme. The enzymes eat a hole into the first layer, allowing the sperm head to come in contact with the vitelline layer. Proteins on the sperm cell's surface attach to the receptor proteins of the vitelline layer. The joining of the two surfaces guarantees that no other sperm can fertilize the egg. The sperm's plasma membrane and the egg cell's plasma membrane then merge together. Afterward, the nucleus of the sperm can then enter the egg cell. During this time, the combined sperm and egg cell are still in the fallopian tube, near the ovary and almost instantly begins cell division. When it finally reaches the uterus for implantation into the endometrium, it is then composed of about 100 cells and is a concave ball called a blastocyst. This begins the first trimester of the three trimester pregnancy. The newly formed ball of cells is now known as an embryo.

The First Trimester

The human blastocyst is filled with fluid and surrounded by the outer layer of cells called the trophoblast. The cavity containing the fluid also contains a mass of cells that will eventually develop the baby. The trophoblast also eventually becomes the placenta. When it does, the placenta begins to produce hormones that stop the corpus luteum from collapsing and cause the endometrium to be preserved by the hormones of the corpus luteum until the placenta can produce an efficient amount of hormones itself. The extra embryonic membrane is formed from some of the cells from the cell mass in the blastocyst and some of the trophoblast cell. This is a four part structure tat include the amnion, the yolk sac, the chorion, and the allantois. The