L38 Fertilization Clevage & Implantation

Question 1

Whats the definition of fertilization?

Answer 1

Process by which mature sperm and mature ovum meet and fuse forming the zygote

Question 2

Site of fertilization?

Answer 2

At the ampullary part of the uterine tube

Question 3

Stages of fertilization?

Answer 3

Spermatozoa are not able to fertilize the oocyte immediately upon arrival in the female genital but must undergo capacitation and the acrosome reaction to acquire this capability

Question 4

Parts of the spermatozoa?

Answer 4

• Composed of a head housing the nucleus
• and tail divided into 4 regions
  a) neck
  b) middle piece
  c) principle piece
  d) end piece

Question 5

Components of head of spermatozoa?

Answer 5

• *Condensed nucleus containing only 23 chromosomes 22 autosomes+ X or Y
• • acrosome which partially surrounds the anterior aspect of the nucleus contains hydrolytic enzyme

Question 6

Components of the middle piece?

Answer 6

Contains mitochondria sheath that provides energy for sperm motility. Mitochondria is inherited from the mother only

Question 7

Components of the flagellum?

Answer 7

Houses the axoneme that has a structure similar to the cilia and responsible for sperm motility

Question 8

Whats the role of the head in fertilization?

Answer 8

The acrosome comes into contact with the cell membrane of the spermatozoon anteriorly it houses various enzymes including neuraminidase, hyaluronidase, acid phosphate aryl sulfatase and trypsin like protease known as acrosin.q212q

Question 9

Capacitation of fertilization

Answer 9

Capacitation: a period of conditioning in the female reproductive tract in humans it lasts about 7 hours during this period a glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that overlies the acrosomal region of the spermatozoa

Question 10

Acrosome reaction of fertilization?

Answer 10

Which occurs after binding of the head to the zona pellucida is induced by zina proteins enzymes needed penetrate to the zona pellucida are released including across and trypsin like substances

Question 11

Phases of fertilization.

Answer 11

Phase 1 penetration of the corona radiate
Phase 2 penetration of zona pellucida
Phase 3
Fusion of the oocyte and sperm head cell membranes

Question 12

Results of fertilization

Answer 12

Restoration of the diploid number of chromosomes
Determination of the sex of then new born
Initiation of cleavage without fertilization the oocyte usually degenerates 24 hours after ovulation.

Question 13

Cleavage definition?

Answer 13

A series of a series of mitotic divisions that result in an increase in cells

Question 14

Site of cleavage?

Answer 14

The uterine tube, medial of the ampulla

Question 15

First stage of cleavage?

Answer 15

Morula stage:
After 30 hours of fertilization the zygote divides into 2 cells (blastomeres) then into 4 blastomeres at 40 hours.
The 12 cell stage is reached after 3 days if fertilization and the 16 cell stage is reached on the 4th day.12-16 blastomeres is called morula and they get their nutrients from its cytoplasm

Question 16

Stage 2 of cleavage?

Answer 16

Blastocyst formation:
As the morula enters the uterus, fluid from the uterine cavity penetrates the zona pellucida and coalesces to form a single cavity (blastocele) and the embryo is called blastocyst.
The blastocele divides the blastomere into inner cell mass which will form the embryo properly. The surrounding cells from the outer cell mass which will form the trophoblast that will form the fetal part of the placenta.
The cells of the inner cell mass are now called embroblast and are located at one pole of the blastocyst and the zona pellucida disappears immediately before implantation.