embryogenesis

Question 1

embryonic period of development

Answer 1

weeks 3-8

Question 2

fetal period of development

Answer 2

• week 9 => term

- mainly growth; also brain and nervous development

Question 3

morula

Answer 3

• after the 8 cell stage

Question 4

blastocyst

Answer 4

• weeks 1-2 of development

- trophoblast + blastocyst cavity + inner cell mass

Question 5

trophoblast

Answer 5

• outer cell layer of the blastocyst

- simple squamous epithelium

Question 6

inner cell mass

Answer 6

• inner part of blastocyst

- will form embryo

Question 7

ectopic pregnancy

Answer 7

• normal implantation = posterior upper uterine wall

- ectopic sites: tubal, abdominal, ovarian, cervical

Question 8

chorionic villi

Answer 8

• fetal contribution to the placenta

- on the side of the blastocyst that implants

Question 9

implantation

Answer 9

1. blastocyst (inner cell mass end) attaches to uterine epithelium
2. trophoblast (syncytiotrophoblast) invades the endometrium

Question 10

decidua basalis, capsularis, and parietalis

Answer 10

• layers of the endometrium that shed
• basalis = maternal component of placenta; engaged with villous chorion
• capsularis = overlies smooth chorion
• parietalis = uninvolved uterine mucosa (front wall of uterus)

Question 11

placenta

Answer 11

• chorionic villi bathed in maternal blood from the decidua basalis
• site of maternal/fetal exchange
• early placental membrane: syntrophoblast, cytotrophoblast, connective tissue, endothelium of blood vessels
• late placental membrane: syntrophoblast, endothelium

Question 12

umbilical cord

Answer 12

• comes from the connecting stalk

Question 13

chorionic villi

Answer 13

• fetal contribution to the placenta
• on the side of the blastocyst that implants
• layers of the placental villi are the layers of the chorion (syntrophoblast, cytotrophoblast, mesenchyme)
• most villi are free (coated with syntrophoblast) and are sites for metabolic exchange, but anchoring villi span the thickness of the placenta to desidua basalis

Question 14

bilaminar embryo

Answer 14

• epiblast => embryo

- hypoblast => outer structures

Question 15

amnion

Answer 15

• amnion cavity forms when inner cell mass becomes hollow around time of implantation
• consists of ectoderm and extra-embryonic mesoderm

Question 16

chorion (smooth and villous)

Answer 16

• outermost membrane of blastocyst
• consists of: syntrophoblast, cytotrophoblast, and extra-embryonic mesoderm
• smooth chorion covers amnion
• villous chorion contains the villi that become the placenta

Question 17

yolk sac

Answer 17

• forms on day 10
• consists of: endoderm and extra-embryonic mesoderm
• provides early nutrition

Question 18

ectoderm

Answer 18

• comes from epiblast

- surrounds amniotic cavity

Question 19

endoderm

Answer 19

• surrounds yolk sac

Question 20

mesoderm

Answer 20

• comes from primitive streak/node and the ectoderm
• forms notochord along the midline then spreads outward to engage extra-embryonic mesoderm
• begins as loss connective tissue (mesenchyme) then condenses to form several columns

Question 21

mesenchyme

Answer 21

= extra-embryonic mesoderm

embryonic loose connective tissue

Question 22

gastrulation

Answer 22

• occurs with appearance of intra-embryonic mesoderm

Question 23

primitive streak

Answer 23

• streak of thickening ectoderm arising behind the primitive knot (mesoderm)
• goes on to form the intra-embryonic mesoderm

Question 24

notochord

Answer 24

• condensed mesoderm (epithelial columns)
• induces neural plate
• remains as nucleus pulpois of intervertebral disks

Question 25

paraxial mesoderm

Answer 25

- condensed mesoderm (epithelial columns) | - will form somites for bone, muscle, connective tissue

Question 26

intermediate mesoderm

Answer 26

- condensed mesoderm (epithelial columns) | - will form UG system

Question 27

lateral plate mesoderm

Answer 27

- condensed mesoderm (epithelial columns) | - future body wall and cavities and gut wall

Question 28

coeloms

Answer 28

- intraembryonic coelem forms as the lateral plate mesoderm and cardiogenic mesoderm form a u shape down the middle of the embryo - will form the pleural, peritoneal, and pericardial cavitieis

Question 29

somatopleure

Answer 29

- ectoderm and mesoderm from lateral plate | - will form lateral and ventral body wall (including parietal pleura and peritoneum)

Question 30

splanchnopleure

Answer 30

- endoderm and mesoderm from lateral plate | - will form visceral structures including the gut

Question 31

week 4

Answer 31

- formation of somites, neural tube, and intra-embryonic coelem - 3 layered disk => cylinder shape

Question 32

amniotic fluid

Answer 32

- allows movement of fetus - initially comes from mother; later is fetal urine which is recycled - too little: renal agenesis - too much: inhibition of absorption or swallowing

Question 33

week 3

Answer 33

- gastrulation occurs with appearance of 3rd germ layer (intra-embryonic mesoderm) - elongation of the embryonic disk - neuralation

Question 34

allantois

Answer 34

vestigial extra-embryonic membrane formed from yolk sack

Question 35

week 1

Answer 35

ovulation, conception, and migration down uterine tube zygote => morula

Question 36

week 2

Answer 36

implantation and extraembryonic membrane formation morula => blastocyst - embryo becomes bilaminar disk - syntrophoblast + cytotrophoblast + extra embryonic mesoderm => amnion, yolk sac, chorion