A mature ovum is a large cell consisting of large

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A mature ovum is a large cell consisting of large quantities of cytoplasm and organelles. It will actually contribute nearly all of its cytoplasm, organelles, and half of its DNA to the zygote, whereas sperm only contributes half of its DNA - Upon completion of meiosis II, the haploid pronuclei of the sperm and ovum join, creating a diploid zygote - In general oocytes are surrounded by two layers, which are commonly known as: The Zona Pellucida and The Corona Radiata - The Zona Pellucida : Is an acellular mixture of glycoproteins that protect the oocyte and contain the compound necessary for sperm binding - The Corona Radiata: Lies outside the zona pellucida and is a layer of cells that adhere to the oocyte during ovulation
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- Sexual Development: Introduction: - The ability to reproduce is under hormonal control. Prior to puberty, the hypothalamus restricts production of gonadotropin-releasing hormone (GnRH) - At the start of puberty, the restriction is lifted and the hypothalamus releases pulses of GnRH, which then triggers the anterior pituitary gland to synthesize and release follicle stimulating hormone (FSH) and luteinizing hormone (LH) - These hormones trigger the production of the other sex hormones that develop and maintain the reproductive system - Sexual Development: Male Sexual Development: - In order to achieve male sexual development, there is a delicate interplay of FSH and LH on two cell types within the testes - FSH stimulates the Sertoli Cells and triggers sperm maturation, whereas LH stimulates the interstitial cells of Leydig to produce testosterone. - Testosterone not only develops and maintains the male reproductive system, but also results in the development of secondary sexual characteristics such as facial/axillary hair, deeper voice, and increased muscle/bone mass - Testosterone production remains high in adulthood and declines as men age. This hormone exerts a negative feedback on the hypothalamus and anterior pituitary gland so that production is kept within an appropriate range - Sexual Development: Female Sexual Development: - The ovaries are also under the control of FSH and LH, which are secreted by the anterior pituitary gland, and stimulate the ovaries to produce estrogen and progesterone - Estrogens are secreted in response to FSH and result in the development of the female reproductive tract and the female secondary sexual characteristics such as breast growth, widening of hips, and changes in fat distribution - In embryos, estrogens stimulate the development of the reproductive tract; In adults, estrogens lead to the thickening of the lining of the uterus (endometrium) each month in preparation for implantation of the zygote - Progesterone is secreted by the corpus luteum (the remains of the ovarian follicle following ovulation) in response to LH. Progesterone is also responsible for the the development and maintenance of the endometrium (not the thickening!!!) - Therefore this means that both estrogen and progesterone are required for the proper generation, development, and maintenance of the endometrium so
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