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OOGENESIS IN MAMMALS Oogenesis is the process by which female germ cells (oogonia) undergo a series of cell divisions and differentiations to produce mature eggs (ova or oocytes). This complex process takes place in the ovaries of mammals and is crucial for reproductive success. Oogenesis involves several stages, from the development of primordial germ cells to the formation of mature eggs ready for fertilization. Here is an overview of the key stages of oogenesis in mammals: 1. Formation of Primordial Germ Cells (PGCs): Occurs during early embryonic development. PGCs arise from a subset of cells in the embryonic epiblast. Migrate to the genital ridge and undergo mitotic divisions. 2. Differentiation into Oogonia: PGCs differentiate into oogonia. Oogonia undergo mitotic divisions to increase their numbers. 3. Formation of Primordial Follicles: Oogonia develop into primary oocytes. Surrounding somatic cells (pre-granulosa ...

ULTRASTRUCTURE OF OVARY IN MAMMALS The ovary is a crucial reproductive organ in females responsible for the production of eggs (ova or oocytes) and the secretion of hormones, including estrogen and progesterone. The ultrastructure of the ovary reveals its complex organization, including follicles, ova, and various supporting structures. Here are the key components of the ultrastructure of the ovary in mammals: 1. Ovarian Cortex: Ovarian Follicles: Primary Follicles: Contain primary oocytes surrounded by a single layer of granulosa cells. Develop into secondary follicles. Secondary Follicles: Characterized by the formation of an antrum (fluid-filled cavity). Granulosa cells divide into multiple layers. Graafian (Mature) Follicles: Large, fluid-filled antrum. Cumulus oophorus: Mound of granulosa cells that surround the oocyte. Theca cells: Surround the fol...

ULTRASTRUCTURE OF SPERM The ultrastructure of a spermatozoon, or sperm cell, is specialized for its function in fertilization. Here are the main components and structures of the ultrastructure of a sperm: 1. Head: Nucleus: Contains densely packed chromatin. Carries genetic material (DNA) for fertilization. Acrosome: A membrane-bound vesicle derived from the Golgi apparatus. Contains enzymes (acrosin) essential for penetrating the egg during fertilization. Flagellum Attachment: The base of the head connects to the midpiece of the sperm. 2. Midpiece: Mitochondria: Numerous mitochondria arranged in a helical pattern around the axial filament (central pair of microtubules). Provide the energy (ATP) needed for sperm motility. Axial Filament: Central pair of microtubules extending from the basal body to the end of the tail. Forms the core of the flagel...