Intro to Embryology

Question 1

embryonic period

Answer 1

fertilization–> 8 weeks

-initial development of all major structures and establishment of all organ systems

Question 2

human development

Answer 2

embryonic period

fetal period

Question 3

fetal period

Answer 3

9th week to term (38 or 40 weeks)

• differentiation and growth of organs and tissues
• specialization takes place here

Question 4

teratology

Answer 4

the study of abnormal development (genetic/ environmental causes)

Question 5

N

Answer 5

haploid number of chromosomes (23 chromosomes)

Question 6

ploidy

Answer 6

number of copies of each unique double stranded molecule

Question 7

origin and maturation of Primordial Germ Cells (PGC)

Answer 7

• Originate as endodermal cells lining the yolk sac (umbilical vesicle) near origin of allanointis
• Diploid (2N)
• Migrate to occupy gonads and mature into gametes (mature sex cells: spermatozoa & oocyte)

Question 8

gametogenesis

Answer 8

when primordial germ cells form and mature into the male and female gametes (spermatozoa and oocytes)

Question 9

spermatogenesis

Answer 9

spermatogonia –> sperm *begins at puberty

Question 10

oogenesis

Answer 10

oogonia –> oocyte *begins before birth, halts, restarts (one cell at a time) beginning at puberty

Question 11

oocyte

Answer 11

Zona pellucida
Corona radiata
Immotile
All are 23X

Question 12

sperm

Answer 12

Motile

23 X or 23Y

Question 13

capacitation

Answer 13

Surface proteins removed from acrosome; allows acrosome to react with corona radiata & ZP, and release of enzymes

Question 14

acrosome reaction

Answer 14

occurs on contact with ZP; results in release of enzymes, allows penetration of ZP and facilitates fertilization

Question 15

hyperactivation

Answer 15

¥ follows capacitation – increasing the activity of the sperm.
¥ About 200 perm in the uterine tube at one time
¥ Sperm viability up to 3 ½ days

Question 16

three steps of fertilization

Answer 16

Fertilization: 3 phases ***

1: Coronal cells
2: Acrosomal reaction
3: Plasma membranes fuse, Meiosis II resumes, metabolism of oocyte increases

Question 17

zona pellucida

Answer 17

thick wall surrounding cytoplasm

Question 18

corona radiata

Answer 18

sperm break through these layers (follicular cells) to access nucleus where chromosomes intermingle

Question 19

blastomeres

Answer 19

early embryonic cells that are a result of the zygote undergoing mitosis (~30 hours after fertilization)

Question 20

compaction

Answer 20

Cell divisions result in successively smaller blastomeres that remain confined within the space available within the zona pellucida

Question 21

blastocyst

Answer 21

after 4-5 days, the morula reorganizes to form an inner and outer cell mass where fluid accumulates to form the blastocystic cavity–> now a blastocoel. Zone pellucid not degenergated

Question 22

embryoblast

Answer 22

inner cell mass: gives rise to the embryo

Question 23

trophoblast

Answer 23

◊ -outer cell mass; becomes extraembryonic structures (embryonic contribution to the placenta)
◊ -is the nutrition (“trophy”)
-differentiates at day 7 into cytotrophoblast and syncytiotrophoblast

Question 24

cytotrophoblast

Answer 24

doesn’t embed in uterus-> becomes extra embryonic structures (surrounds embryonic structure)

Question 25

syncytiotrophoblast

Answer 25

embeds in posterior wall of endometrium

Question 26

ectopic pregnancy

Answer 26

Blastocyst implants outside normal uterine locations

Question 27

hypoblast

Answer 27

small cuboidal cells formed from the embryoblast (inferior to)
Primary Endoderm