Week 6 Fertilization/ Early Development- Holy

Question 1

Describe capacitation

Answer 1

glycoprotein and lipid content changes in sperm plasma membrane during passage through female reproductive tract

Question 2

Where does fertilization occur?

Answer 2

ampulla of the oviduct

Question 3

Describe the acrosomal reaction

Answer 3

• swimming action of sperm penetrates follicle layer
• sperm plasma membrane proteins bind ZP-3 (zone pellucida glycoprotein)
• Binding activates sperm Na+/H+ and Ca+ transporters.
• increase sperm cytoplasmic pH
• Ca+ influx triggers exocytosis of acrosomal vesicle
• Hydrolytic enzymes of the acrosome digest the zona and allow sperm to contact the egg plasma membrane

Question 4

Important of Ca+ in sperm-egg binding and fusion?

Answer 4

Sperm phospholipase C produces IP3 from phosphotidylinositols, opening calcium channels in egg ER.
Causes:
-cortical granule exoctosis
-allows meiosis II to be completed by activating APC
-Initiation of developmental program of the egg

Question 5

What are two blocks to polyspermy?

Answer 5

Fast block- fusion of sperm and egg plasma membrane cause a rapid membrane change that is immediately inhibitory to further fusion with sperm

Slow block- release of cortical granules modify zona, destroying the sperm-binding capability of ZP3

Question 6

What are two important stages of the Morula?

Answer 6

• Formation of inner and outer cells (inner cells make body of the embryo, outer/trophoblast makes extraembryonic tissues)
• compaction: change in the was blastomeres interact with each other, from tight/gap junctions and flatten together to form tight ball. Cells become polarized

Question 7

Hatching

Answer 7

6/7 days after fertilization
hydrolytic enzymes from embryo are relased to degrade the zona pullcida that envelopes embryo
-blastocyst “hatches” out of zone
-Zona prior to hatching helps prevent ectopic implantation

Question 8

Ectopic implantation

Answer 8

implantation at a site other than the posterior wall of the uterine cavity, usually ampulla of the oviduct, ovary, or abdominal cavity

Question 9

plactenta previa

Answer 9

implantation close to the mouth of the cervix and placenta partially covers the cervical canal

Question 10

What does the trophoblast form into?

Answer 10

• Some form syncytiotrophoblast which fuse to the hormonally prepared endometrium. Secretes HCG to tell mom to keep secreting estrogen and progesterone
• cells that do not fuse are call cytotrophoblast cells (which replicated via mitosis and then fuse with syncytiotrophoblast to keep it growing)

Question 11

What is delamination?

Answer 11

isolates the inner cell mass a seperate entity from the trophoblast.

inner cell mass flattens to from circular disc composed of two cell layers

closet to amniotic cavity is the epiblast (tall columnar)
closet to the primary yolk sac are the hypoblast (cuboidal)

Question 12

What do the epiblast and hypoblast form?

Answer 12

Epiblast will make the embryo, hypoblast will only make extraembryonic structures

Question 13

Define gastrulation

Answer 13

mass migration of cells which end up forming the three germ layers of they body (all germ layers originate from the epiblast)

Question 14

primitive streak

Answer 14

thickening of epilast in middle due to migration of epiblast cells toward the midline of the embryonic disc. Streak turns into a groove through which other epiblast cells migrate to form the mesoderm and endoderm. (cells remaining in the epiblast become the ectoderm)

Question 15

Notochord formation and functions

Answer 15

Mesoderm cells migrate to form the notochord.

• lends longitudinal mechanical support to the embryo
• serves as POWERFUL inductive force on the subsequent differentiation of many cell types.

Question 16

Neural tube formation

Answer 16

Epiblast (ectoderm) cells directly overlaying the notochord are induced by the notochord to proliferate and to form a thickening called the neural plate. Plate makes folds, folds curve around to make neural tube.

Question 17

Neural Crest

Answer 17

cells that have detached from the fold migrate within the embryo and eventually give rise to ganaglia, schwann cells, meninges, adrenal medulla and melanocytes.

Question 18

Mesoderm dynamics

Answer 18

Embryonic mesoderm forms three series of swelling
Paraxial mesoderm
intermediate mesoderm
lateral mesoderm

Question 19

Paraxial mesoderm gives rise to what structure?

Answer 19

SOMITES! Periodic thickenings that occur along the length of the paraxial mesoderm, form in pairs, one on each side of the notochord –> give rise to most of the axial skeleton, associate musculature and adjacent dermis of skin

Question 20

intermediate mesoderm gives rise to what?

Answer 20

formation of urogenital system

Question 21

lateral mesoderm gives rise to what?

Answer 21

serous membranes of pleura, pericardium, peritoneum, connective tissue, and muscle of viscera, heart, blood cells

Question 22

Somites reorganize to form what?

Answer 22

sclerotomes- axial skeleton
myotomes- axial musculature
dermomytomes- epidermis and assoicated musculature