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Reproductive Systems. 3-D male reproductive System. 3-D female reproductive System. Testes Tissue. Sperm production occurs in seminiferous tubules. See Fig. 46.12. Testes Tissue. Sperm production occurs in seminiferous tubules At puberty, testosterone production begins
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Reproductive Systems 3-D male reproductive System 3-D female reproductive System
Testes Tissue Sperm production occurs in seminiferous tubules See Fig. 46.12
Testes Tissue Sperm production occurs in seminiferous tubules At puberty, testosterone production begins in interstitial cells See Fig. 46.12
Testes Tissue Sperm production occurs in seminiferous tubules Sertoli cells regulate sperm production & nourish developing sperm See Fig. 46.12
Testes Tissue Sperm production occurs in seminiferous tubules Spermatozoa are produced by spermatogonia See Fig. 46.12
Spermatogenesis • production of sperms occurs in the testes in seminiferous tubules • first stage of spermatogenesis mitotic cell divisions of primordial germ cells to produce spermatogonial cells • spermatogonial cells then undergo a period of growth to form primary spermatocytes • each primary spermatocyte then undergo two meiotic cell divisions: • meiosis I to produce secondary spermatocyte & • meiosis II to produce spermatids • spermatid cells then undergoes differentiation to form sperm cells • Sperm cells are nourished by Sertoli cells • each primary spermatocyte produce 4 sperm cells with haploid number of chromosomes i.e. 23 chromosomes
Oogenesis • oogenesis is process by which female gametes (egg cells) are produced in the ovary • it begins during fetal development when oogonia are formed from primordial germ cells by mitosis • Oogonia undergoes growth to form primary oocytes • primary oocyte begin first meiotic division but stop in Prophase I until on set of puberty • at puberty some follicles develop each month in response to FSH produced by pituitary gland • primary oocyte completes first meiotic division to forms two cells of different sizes due to unequal distribution of cytoplasm • the one with less cytoplasm become the first polar body which eventually degenerates • the larger cell becomes secondary oocyte and proceeds to meiosis II & stops at prophase II • meiosis II is completed if cell is fertilized forming an ovum and second polar body
Comparison Between spermatogenesis & oogenesis spermatogenesis oogenesis • millions sperms produced per day • four sperms of equal division of the cytoplasm & no polar bodies • begins at puberty i.e. at sexual maturity • occurs throughout adult life • sperms are produced continuously & released during ejaculation • occurs in the testes • spermatogenesis involves meiotic cell division • produce haploid cells • one ovum per 28 day menstrual cycle • one ovum, unequal division of the cytoplasm, 2 polar bodies • begins during foetal development • ends at menopause • ovum released during ovulation in the middle of the menstrual cycle • occurs in the ovaries • oogenesis involves meiotic cell division • produce haploid cells
Fertilisation • sperm cell approach the egg in oviduct • Acrosome of sperm cell releases hydrolytic enzymes which digest jelly layer (zona pellucida) of the egg • sperm cell head (acrosomal process) extends through jelly to vitelline membrane (egg’s plasma membrane) • binding proteins on surface of acrosome attach to receptors on vitelline membrane • sperm plasma membrane fuses with egg plasma membrane • fusion of plasma membranes causes depolarization of egg plasma membrane i.e. cortical reaction which bars other sperm cells from fusing with membrane • sperm nucleus enters egg (secondary oocyte) after dissolution of nuclear membranes resulting in combination of genetic material
Revision Questions • Draw a labelled diagram of the adult female reproductive system. [4] • Draw a labelled diagram of an adult male reproductive system. [6 ] • Explain the processes involved in oogenesis in humans. [9] • Draw the structure of a mature human egg. [4] • Explain the role of hormones in the regulation of the menstrual cycle in human females. [8] • Draw a labelled diagram of a mature sperm. [5] • Outline the process of spermatogenesis in humans. [5] • Compare the process of spermatogenesis and oogenesis. [7] • Describe the process of fertilization in humans. [8] • Describe the development of the early human embryo. [5] • Outline the regulation of pregnancy by two named hormones. [4]
