Gametogenesis Flashcards
Define gametogenesis
Development and production of mature and functioning male and female germ cells.
What are the criteria of germ cells that will form gametes ?
- It should contain half the number of chromosomes (haploid)
- It should have the size and shape that allow germ cells form both parents to join and become one cell called the zygote.
In regards to the origin of germ cells. A sperm will fertilize the ovum in the fallopian tube and form the zygote.
He will move in the fallopian tube and become a ______ then reach the uterus with a group of cells inside of it called the inner cells mass. When this blastocyst is implanted in the endometrium, this inner cell mass will start dividing and form a disc with 2 layers. The upper layer is called _____ and the lower layer is called _____.
Blastocyst
Epiblast
Hypoblast
Spermatogenesis includes all the events by which spermatogonia are transformed into spermatozoa. In contrary to oogenesis, spermatogenesis starts at _______. Thus, shortly before puberty, the sex cords acquire a lumen and become __________. At about the same time, PGCs give rise to spermatogonial stem cells which differentiate to form ___________. Their production marks the initiation of spermatogenesis. These cells produces type B spermatogonia, which them divide to form ______.
Puberty
Seminiferous tubules
Type A spermatogonia
Primary spermatocytes
During the 2nd week of development, some cells of the epiblast will migrate towards the _____ and wait for signal.
yolk sac
During the 5th week, the primordial germ cells will become activated and migrate from the yolk sac to the ______. There, germ cell will divide to increase their number and all of them will now be diploid.
Genital ridge
The somatic cells in the genital ridge and the primordial germ cells from the ____ & _____. The primordial germ cells will reside in the male or female gonads and become the spermatogonia or ova (oogonium) having a total of 46 chromosomes.
Testes & Ovary
Primary spermatocytes enter a prolonged _____ followed by a rapid completion of meiosis 1 and formation of secondary spermatocytes. During this second meiotic division, these cells immediately begin to form _______ (haploid =1n).
prophase
Spermatids
Spermatogenesis is regulated by ____ production by the pituitary gland which binds receptors of _____ and stimulate testosterone production. Testosterone binds to______ to promote spermatogenesis. FSH is also essential in this process.
LH
Leydig cells
Sertoli cells
The series of changes resulting in the transformation of spermatids to spermatozoa is called :
Spermiogenesis
Briefly describe the 4 phases of spermiogenesis
- Golgi phase : The head forms at one end, and the golgi apparatus creates enzymes that will become the acrosome. The acrosome covers half of the nuclear surface and contains enzymes to assist in penetration of the egg
- Condensation of the nucleus
- Formation of neck, middle piece and tail
- Shedding of most of the cytoplasm as residual bodies that are phagocytized by Sertoli cells
Maturation of oocytes begins before birth. Once PGCs hava arrived in the gonad, they differentiate into oogonia. These cells undergo several mitotic divisions and the majority of oogonia continue to divide by mitosis, but some of them arrest their cell division in _______of meiosis 1 to form primary oocytes.
Prophase
During the next few months, oogonia increase rapidly in number followed by cell death. By the ____ month, the majority of oogonia have degenerated except for a few near the surface. All surviving primary oocytes have entered ______ of meiosis 1 and most of them are individually surrounded by a layer of flat follicular epithelial cells.
7th
prophase
A primary oocyte, together with its surrounding flat epithelial cells, is known as a ____ ___.
Primordial follicule
Primary oocyte remain arrested in prophase until puberty is reached. This arrested state is produced by the _______ (OMI), a small peptide secreted by follicular cells.
Oocyte maturation inhibitor
A primary oocyte, together with its surrounding flat epithelial cells is known as a primordial follicle. Follicular cells change from flat to cuboidal and form many layers of granulosa cells, and the unit is called primary follicule. Granulosa cells are surrounded by ovarian connective tissue, the _______. Granulosa cells and oocyte secrete a layer of glycoproteins on the surface of the oocyte forming the _______.
Theca folliculi
Zona pellucida
In the mature vesicular follicle (graafian follicle) granulosa cells surrounding the oocyte remain intact in form the ______. At maturity the mature graafian follicle is surrounded by the theca interna which secretes ______, and the theca externa, which eventually merges with the ovarian connective tissue.
Cumulus oophorus
When the secondary follicle is mature, a surge in _____ hormone induces the preovulatory growth phase. Meiosis 1 is completed, resulting the formation of 2 daughter cells of unequal size, each with 23 double structured chromosomes. One secondary oocyte receives most of the _______ ; and the other (the first polar body), receives practically none. The cell then enters meiosis 2, but arrests in _____ approx 3h before ovulation.
LH
Cytoplasm
Metaphase
