embryology

Question 1

embryology

Answer 1

developmental events that occur prior to birth

Question 2

prenatal period

Answer 2

first 38 weeks of human development

Question 3

the prenatal period is a sequence of events occurring from

Answer 3

fertilization to birth

Question 4

three developmental stages of the prenatal period

Answer 4

pre-embryonic period, embryonic period, and fetal period

Question 5

how long is the pre-embryonic period

Answer 5

first two weeks after fertilization of the egg

Question 6

what happens during the pre-embryonic period

Answer 6

formation of a blastocyst

Question 7

how does the pre-embryonic period end

Answer 7

with implantation in the lining of the uterus

Question 8

how long is the embryonic period

Answer 8

weeks three through eight

Question 9

what happens during the embryonic period

Answer 9

all major organ systems begin to develop

Question 10

how long is the fetal period

Answer 10

weeks nine through thirty-eight

Question 11

what happens during the fetal period

Answer 11

growth and development continues

Question 12

when does the fetal period end

Answer 12

at birth

Question 13

week 1: assume that

Answer 13

sperm fertilized ovum

Question 14

week 1: what happens after the zygote is formed

Answer 14

it undergoes cleavage (mitotic divisions)

Question 15

week 1: name of structure at the 16-cell stage

Answer 15

morula

Question 16

week 1: what does the morula become

Answer 16

after entering the uterine cavity, it becomes a blastocyst

Question 17

two components of the blastocyst

Answer 17

trophoblast and embryoblast

Question 18

trophoblast

Answer 18

outer ring of cells that will develop into the chorion

Question 19

embryoblast

Answer 19

cluster of tightly packed cells inside one side of the blastocyst that will form the embryo

Question 20

implantation process

Answer 20

• within a week of fertilization, a blastocyst enters the uterus
• invades endometrium (lining of uterus)
• blastocyst has completely burrowed into uterine wall by day 9

Question 21

formation of bilaminar germinal disc

Answer 21

• cells of embryoblast differentiate into two types by day 8
• two types/layers are hypoblast and epiblast
• two layers form a flat disc (bilaminar germinal/embryonic disc)

Question 22

hypoblast

Answer 22

layer of small cuboidal cells facing the blastocyst cavity

Question 23

epiblast

Answer 23

layer of columnar cells deep to the hypoblast

Question 24

bilaminar germinal disc and trophoblast produce what

Answer 24

three extraembryonic membranes

Question 25

three extraembryonic membranes

Answer 25

yolk sac, amnion, and chorion

Question 26

yolk sac

Answer 26

serves as a site for early blood cells and vessel formation

Question 27

amnion

Answer 27

thin layer of cells that forms above and is derived from the epiblast

Question 28

what appears between the amnion and epiblast layer

Answer 28

fluid-filled amniotic cavity

Question 29

chorion

Answer 29

outermost membrane responsible for the formation of the placenta

Question 30

placenta

Answer 30

highly vascularized organ that serves as an interface between embryo or fetus and mother

Question 31

chorion

Answer 31

embryonic portion of the placenta

Question 32

functions of the placenta

Answer 32

- exchange of nutrients, waste products, and respiratory gases between embryo and mother - transmission of maternal antibodies to embryo or fetus - production of estrogen and progesterone to maintain uterine lining

Question 33

gastrulation

Answer 33

process where cells from the epiblast migrate to form the primary germ layers

Question 34

what does gastrulation start with

Answer 34

the formation of the primitive streak

Question 35

primitive node

Answer 35

cephalic end of the primitive streak

Question 36

primitive pit

Answer 36

a depression in the node

Question 37

three primary germ layers

Answer 37

ectoderm, mesoderm, and endoderm

Question 38

embryo

Answer 38

structure when all three primary germ layers are present

Question 39

invagination

Answer 39

inward movement of cells from the epiblast layer through the primitive streak between epiblast and hypoblast layers

Question 40

mesoderm

Answer 40

cells between the epiblast and hypoblast layers

Question 41

endoderm

Answer 41

other migrating cells that displace the hypoblast cells

Question 42

ectoderm

Answer 42

remaining cells in the epiblast

Question 43

epiblast

Answer 43

where all three germ layers are derived from

Question 44

ectoderm

Answer 44

skin, nervous system

Question 45

mesoderm

Answer 45

notochord, skeletal and muscular systems, reproductive system

Question 46

endoderm

Answer 46

lining of digestive tract, liver, pancreas

Question 47

notochord

Answer 47

- derived from the mesoderm | - important signaling structure

Question 48

neurulation

Answer 48

formation of the neural tube from overlying ectoderm cells

Question 49

the neural tube develops into the

Answer 49

central nervous system

Question 50

what must the embryo do in order to keep growing

Answer 50

begin folding

Question 51

cephalocaudal folding

Answer 51

- head and tail fold - fetal position - bringing heart to thoracic

Question 52

transverse folding

Answer 52

- lateral folding - ectoderm is on the outside - left and right sides of embryo curve toward the midline

Question 53

organogenesis

Answer 53

organ development

Question 54

when are most organ systems complete

Answer 54

by the end of the embryonic period (week 8)

Question 55

teratogens

Answer 55

agents that can interfere with normal development or cause congenital malformations

Question 56

example of teratogen

Answer 56

alcohol

Question 57

when does the share of blood flow between the mother and embryo start

Answer 57

week 3

Question 58

how long is the fetal period

Answer 58

begins week 9 and ends at birth

Question 59

how is the fetal period characterized

Answer 59

by maturation and growth of tissues and organs