Embryology Midterm

• similar untill 4th week of development 
• testes are directed by Sry gene, testosterone and Mullerian-Inhibiting Factor
• ovaries have no factor involved

• allows for random assortment of maternal and paternal chromosomes between gametes
• relocates segments by crossingover, shuffles genes 

begins at puberty, including all of the events by which spermatogonia are transformed into spermatozoa.  regulated by Luteinizing Hormone (LH) and Follicle stimulating Hormone (FSH)

maturation of oocytes begins befor birth.  the oogonia enter meiosi 1 to form primary oocytes. during puberty the primary oocyte completes mieosis 1 and forms the secondary oocyte and remains in meiosis 2 and is ovulated.  fertilization occurs and meiosis 2 is complete forms mature oocyte

• diploid
• arrested in meiosis 1 untill puberty

• occurs during puberty 
• meiosis 1 completes nd enters meiosis 2 untill ovulations

• occurs at fertilization 
• meiosis 2 completes and forms mature oocyte, become haploid

contain immature oocytes currounded by a single layer of support cells 

the support cells change structure the oocyte genome is activated and genes become transcribed 

fully grown oocyte surrounded by a zone pellucida

FSH stimulates the development of ovarian follicles and the production of estrogen by its follicular cells. it also stimulates the synthesis of LH receptors

• LH causes the oocyte t complete meiosis 1, initiating meiosis 2. 
• also stimulates the production of progesterone by follicular stromal cells and causes follicular rupture and ovulation

before ovulation phase in the follicular phase of ovarian cycle

follicular cells 

the corpus luteum

during ovulatory phase which is around day 14-15 of the sendometrial cycle

corpus luteum dies levels of progesterone drop suddenly.  and shedding of the endometrial lining

before birth

at puberty and occurs during ovulatory phase

at puberty when the oocyte finishes meiosis 1 stays untill fertilization.

endometrial linning undergoes ischemia. the upper region of the endometrial stroma contains numerous decidual cells.  spiral arteries constrict causeing ischemia resulting in shedding of endometrial lining.

lining of uterus undergoes the decidual reaction, endometrial glands proliferate and the endometrial vascularity increases.  the blastocsyt losses the zone pellucida and becomes adherent and embeds into the uterine lining.  corpus luteum enlarges and become corpus luteum of pregnancy.

the ampulla region of the oviduct

zona pellucida undergoes lysis.  become impermeable to other sperm

haploid female reproductive cell or gamete

initial cell formed when 2 gamete cells are joined by means of sexual reproduction.  earliest stage in embryo development

has to pass through the corona radiata. by releasing hyaluronidase from the sperm acrosome, tubal mucosal enzymes and flagella action

the acrosomal enzymes causes lysis of the zona pellucida

• esterases
• acrosin
• neuraminidase

about 5

undergoes lysis and become impermeable to other sperm

a series of miotic divisions that occur in the zygote

the 12-32 stage of division, the blastomeres form a morula which consists of an inner and outer cell mass.  occurs aound 3rd day after fertilization looksl ike a mulberry

occurs day 4 forms when fluid secreted within the morila forms the blastocyte cavity.  this seperates the inner cell mass from the outer cell layer

M2 finishes for the oocyte resulting in the formation of the diploid number of chromosomes (46).  maternal and paternal chromosomes intermingle and sex is decided at this time