Flashcards in Folliculogenesis Deck (37)
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What are the 4 things required for reproduction?

β†’ Differentiation into male or female
β†’ Sexual maturation
β†’ Production, storage and release sufficient supply of eggs and sperm
β†’ correct number of chromosomes in eggs and sperm
β†’ egg and sperm have to meet


What are cells that will become egg or sperm called?

β†’ Primordial germ cells


When are PGCs first identifiable?

β†’ in the yolk sac 3 weeks after conception


What happens to the PGCs?

β†’ the cells undergo many cycles of mitosis
β†’ They migrate to the genital ridge


What does the genital ridge become?

β†’ The gonad


What does further differentiation of the PGCs depend on?

β†’ The development of the gonad


What do germ cells become when in the ovary?

β†’ oogonia


What are oogonia?

β†’ Egg precursors


When oogonia enter meiosis what are they known as?

β†’ Primary oocytes


What phase do primary oocytes remain in and until when?

β†’ They remain in the first phase of meiosis until it ovulates or dies


Describe mitosis briefly?

β†’ Spindle is formed
β†’ The chromatids are lined up one behind the other
β†’ They then separate to opposite poles of the cell
β†’ The cytoplasm divides and there are two identical cells


Describe meiosis

β†’ Duplication of the chromatids
β†’ They line up adjacent to each other
β†’ Chromosome 1 lines up with chromosome 1 from the other parent
β†’ allows crossing over and biological variation
β†’ homologous chromosomes separate into two haploid cells
β†’ separate again to form gametes
β†’oocytes are arrested in meiosis 1 until LH surge


where are primary oocytes packed?

β†’ Outer layer of the ovary : cortex


What do the cells around the oocyte become in the fetal ovary?

β†’ Condense around the oocyte and differentiate into granulosa cells


What do granulosa cells secrete?

β†’ Acellullar layer called the basal lamina


What does a primordial follicle consist of?

β†’ Oocyte with granulosa cells and a basal lamina


What do germ cells become in the ovary?

β†’ oogonia


What type of cell are oogonia and how do they multiply?

β†’ Diploid
β†’ Multiply by mitosis


What happens to the follicles at puberty and at menopause?

β†’ Follicles start growing at puberty
β†’ arrests at menopause


What is folliculogenesis defined as?

β†’ Growth and development of follicles from the earliest resting stages as laid down in the fetus through to ovulation


What happens as the follicles start to grow?

β†’ Granulosa cells multiply
β†’ Granulosa cells secrete basal lamina around it
β†’ oocyte secretes another protective acellular layer called the zona pellucida
β†’ Theca cells differentiate around the basal lamina


What are theca cells and what is their purpose?

β†’ Steroid producing
β†’ they sustain the growth of the follicle and the oocyte


What drives most of folliculogenesis?

β†’ FSH


What happens to follicles when FSH is suppressed?

β†’ The follicles will continue early growth but they die


What happens in the second stage of follicle growth?

β†’ Increases rapidly in diameter
β†’ Granulosa cell divisions increase but gaps form in the cell layers
β†’ gaps form an antrum filled with follicular fluid


What are the two main phases of follicular growth?

β†’ Absence or presence of the antrum


What are follicles with an antrum known as?

β†’ antral or secondary follicles


What kind of cells do primordial follicles have and how do they look and grow?

β†’ flattened granulosa cells
β†’ grow in a slow and controlled manner
β†’ become cuboidal in shape


Describe how primordial follicles physically change to become Graffian follicles

β†’ Granulosa cells
β†’ FSH causes granulosa cells to proliferate and the zona pellucida forms around the oocyte
β†’ theca cells are produced around the granulosa cells
β†’granulosa cell divisions increase and gaps form which are filled with follicular fluid
β†’these join and form the antrum
β†’ the egg is then within follicular fluid


What are the cells directly surrounding the oocyte called?

β†’ Corona radiata