Health Care Knowledge, Social Conditions and It’s Influence to Minimized Risks of Abortion

A STUDY ON FACTORS INDUCING STRESS AMONG STUDENTS IN NURSING COLLEGE

THE EFFECT OF SILYMARINE EXTRACTED FROM SILIBUM MARIANUM SEEDS ON HISTOPATHOLOGICAL CHANGES IN MALE RABBITS LIVER AND KIDNEY INDUCED BY NICKEL CHLORIDE TOXICITY

INFLUENCE OF SILYMARIN EXTRACTED FROM SILYBUM MARIANUM SEEDS COMPARED TO LEGALON AGAINST NICKEL CHLORIDE INDUCED HEMATOLOGICAL AND BIOCHEMICAL CHANGES IN MALE RABBITS

Reproduction

Reproduction

By

Wasfi Dhahir Abid Ali

    Reproduction is  the natural process among organisms by which new individuals are generated and the species perpetuated. The reproduction of organisms by the union of male and female reproductive cells (gametes) is called sexual reproduction. While the reproduction in which offspring are produced by a single parent, without the union of reproductive cells, is called asexual reproduction.

spermatogenesis 

     The development of mature spermatozoa from spermatogonia; it includes spermatocytogenesis and spermiogenesis. Also can be defined as  the entire process by which spermatogonial stem cells divide and differentiate into sperms.

Oogenesis 

The developmental process by which the mature human ovum (the female reproductive cell) is formed. Formation begins during the first 3 months of female embryonic life with the development of ovarian follicles. Each follicle contains one oogonium which, through the process of mitosis, becomes a primary oocyte containing 46 chromosomes. The oocyte then undergoes the first meiotic reduction division, resulting in formation of a secondary oocyte and a polar body, each containing 22 autosomes (half the number of chromosomes that are found in nongerm cells) and one X heterosome. Further division is arrested in prophase until the female reaches puberty. The second meiotic division begins at ovulation and reaches metaphase where, once again, division is arrested until the ovum is fertilized. The second meiotic division is completed at fertilization, ending with formation of the mature haploid ovum and one polar body.

Embryogenesis

Is the process by which the embryo forms and develops. In mammals, the term refers chiefly to early stages of prenatal development, whereas the terms fetus and fetal development describe later stages.

Embryogenesis starts with the fertilization of the egg cell (ovum) by a sperm cell, (spermatozoon). Once fertilized, the ovum is referred to as a zygote, a single diploid cell. The zygote undergoes mitotic divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of a multicellular embryo.

Fertilization and the zygote

The egg cell is generally is covered with protective envelopes, with different layers made of glycoproteins and is known as the vitelline membrane (zona pellucida in mammals). Fertilization (also known as 'conception', 'fecundation' and 'syngamy') is the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. The fertilized egg cell is known as the zygote.

Cleavage and morula

       Cell division with no significant growth, producing a cluster of cells that is the same size as the original zygote, is called cleavage. At least four initial cell divisions occur, resulting in a dense ball of at least sixteen cells called the morula. The end of cleavage is known as midblastula transition .

Formation of the blastula

After the 7th cleavage has produced 128 cells, the embryo is called a blastula. The blastula is usually a spherical layer of cells characterized by an inner cell mass that is distinct from the surrounding blastula.

Gastrulation

During gastrulation cells migrate to the interior of the blastula, subsequently forming three (triploblastic) germ layers. The embryo during this process is called a gastrula. The germ layers are referred to as the ectoderm, mesoderm and endoderm.

Nurolation

Formation of the early nervous system - neural groove, tube and notochord>

Gonad differentiation

Humans, many mammals, insects and other animals have an XY sex-determination system. Humans have forty-six chromosomes, including two sex chromosomes, XX in females and XY in males. It is obvious that the Y chromosome must carry at least one essential gene which determines testicular formation (originally termed TDF). A gene in the sex-determining region of the short arm of the Y, now referred to as SRY, has been found to direct production of a protein, testis determining factor, which binds to DNA, inducing differentiation of cells derived from the genital ridges into testes.

a fetus is sexually undifferentiated, or“noncommittal” as to which sex it will become. Its gonads begin to develop at 5 to 6 weeks .Adjacent to each gonadal ridge are two ducts,

1- The mesonephric (wolfian)

2- The paramesonephric (müllerian) duct.

In males, the mesonephric ducts develop into the reproductive tract

and the paramesonephric ducts degenerate.

The Y chromosome has a gene called SRY(sex-determining region of the Y) that codes for a protein called testis-determining factor (TDF).TDF then interacts with genes on some of the other chromosomes, including a gene on the X chromosome for androgen receptors, and those genes initiate the development of male anatomy.

 By8 to 9 weeks, the male has an identifiable testis that begins to secrete testosterone. Each testis stimulates the mesonephric duct on its own side to develop into the system of male reproductive ducts and  atrophy of the paramesonephric (müllerian) duct on that side.

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