M6: Oogenesis and fertilization

Oogonia

• divides swithout completing cytokinesis

• the PGCs become surrounded by follicular cells, creating a separation from surrounding stromal cells

Atresia

• most oogonia and primary oocytes are lost

• “programmed cell death”

Dictyate resting stage

• the surviving primary oocyts are under developmental arrest at the stage of diplotene stage of prophase under meiosis I

• it can last from 12-40 years

• nucleus is often referred to as the germinal vesicle during this stage

Follicle

• combination of oocytes and follicular cells

Primary oocyte

• it is surrounded by a layer of flattened undifferentiated follicular cells

primary

secondary

terriary

3 follicles that continued development from the primordial pool

Leuteinizing hormone

• permitted the resumption of meiosis

• produced by pituitary gland

Ovulation

the mature egg is released from the ovary

Primary follicle

flat follicular cells priliferate to form cuboidal monolayer around the oocyte

Granulosa cells

also known as follicular cells

Secondary follicle

• it is known as the granulosa cells divide to form several layers around the primary oocyte

• these follicles appear oval due to irregular cell division

Zona pellucida

• forming from the oocyte and the granulosa cells produce glycoproteins and deposit them in between the oocyte and granulosa cells

• forms in the “previtelline space”

Theca interna

• the formation of inner and stromal cells found outside the granulosa cells

• a layer of steroid-producing cells

• theca externa = supportive functions

estradiol

• a ‘two-cell’ system wherein theca interna produces androgen

• transported to the granulosa cells transported into ___

Tertiary follicle

• coalescence of the fluids that appear between the granulosa cells into a single cavity

Basal cells

• found most externally function in metabolite transport

• can produce estradiol from the androgens of theca interna

Intermediate granulosa cells

• in the middle layer are involved in transpoert of materials

• contributes to follicular fluid production

granulosa cells

• the inner layer produce antral fluid

Cumulus oophorus

the ring of granulosa cells around the oocyte

Corona radiata

a layer of columnar follicular cells found directly outside the zona pellucida

Oocyte capacitation

antral follicle will start building up its competence to be fertilized

Nuclear oocyte maturation

• primary oocyte resumes meiosis following arrest at the diplotene stage of meiosis I

• continues to the metaphase of meiosis II when the oocyte is ovulated

First polar body

• a smaller cell upon completion of telophase I

• later develops into secondary oocyte

Meiosis II

• only completed during fertilization

• completion: production of haploid

progesterone

estrogen

oxytocin

Hormones produced by endocrine

corpus luteum cyclicum

if fertilization did not occur

corpus albicans

corpus luteum cyclicum regresses into a fibrous scar tissue

sexual reproduction

two haploid gametes fuse into a genetically unique individual

Fertilization

when spermatozoon and the egg unite in the oviduct for mammals

secondary oocyte

zona pellucida

corona radiata

mammalian egg consists of:

flagellar action

uterine muscle contractions

sperm rheotaxis

(3) involves in translocation of the sperm inside the oviduct

Capacitation

• spermatozoa must reside within the female genital tract for a period of time to acquire fertility

• changes in the cell membrane and flagella to prepare th esperm cell to penetrate the zona pellucidaand fuse with the oocye

Acrosome reaction

• a reaction wherein the sperm will undergo once the spermatozoon adheres and binds to the zona pellucida

• releaase of acrosin and hyarulonidase

Syngamy

a process wherein the sperm will fuse with the cell membrane of the oocyte

Cortical granules

• released to modify the zona pellucida to prevent polyspermy

• secondary oocyte resumes meiosis II

zygote

refers to the first daughter cell

Second polar body

other cells that receives much lesser cytoplasm will turn into _____

Maternal pronucleus

forms around the haploid chromosome of the ovum

Karyogamy

after amphixis

• the unison of male and female haploids in the center of the zygote