Chapter 3: Embryology

Question 1

Embryology

Answer 1

study of the origin and development of an individual person or organism

Question 2

Prenatal Period

Answer 2

time between conception and birth

Question 3

embryonic period

Answer 3

first 8 weeks (all major organs in place and the body plan is there)

Question 4

fetal period

Answer 4

remaining 30 weeks (fetus grows larger and gets more complex)

Question 5

Ectoderm

Answer 5

skin and nervous system

Question 6

endoderm

Answer 6

digestive and respiratory system

Question 7

mesoderm

Answer 7

muscle and skeletal system (becomes more later on)

Question 8

Fertilization

Answer 8

fusion of sperm and egg nuclei; occurs in lateral third of uterine tube

Question 9

zygote

Answer 9

fertilized oocyte

Question 10

cleavage

Answer 10

early embryonic stage consisting of rapid cell divisions without intervening growth periods; fertilized ovum–>blastocyst

Question 11

morula

Answer 11

solid cluster of cells; 72 hours (12-16 cells)–> day 3-4 (~60 cells)

Question 12

Blastocyst

Answer 12

hollow ball of cells; product of cleavage (4-5 after fert.)

Question 13

Blastocyst Stage

Answer 13

Inner cell mass (accumulation of cells in blastocyst), trophoblast(external layer of blastocyst cells–> placenta), and implantation (takes a week for blastocyst to implant in uterine lining)

Question 14

Two-Layered Embryo (day 9)

Answer 14

inner cell mass divides into epiblast and hypoblast

Question 15

epiblast

Answer 15

outermost layer of an embryo before it differentiates into the ectoderm and mesoderm

Question 16

hypoblast

Answer 16

innermost layer of an embryo before it gives rise to yolk sac and contributes to endoderm

Question 17

gastrulation

Answer 17

embryo transforms from 1-D layer of cells (epithelial) and reorganizes into multilayers and multidimensional structure referred to as the gastrula

Question 18

bilaminar disc

Answer 18

two-layered structure of the epiblast and hypoblast

Question 19

amniotic sac

Answer 19

fluid filled sac that contains and protects the embryo and eventually the fetus in the womb

Question 20

amnion

Answer 20

outer membrane around the amniotic sac

Question 21

ectoderm

Answer 21

outermost layer of cells or tissue; go on to form epideermis and nerve tissue

Question 22

mesoderm

Answer 22

middle layer of cells or tissue; go on to form skeletal system, muscular system, and notochord

Question 23

endoderm

Answer 23

innermost layer of cells or tissue; go on to form primitive gut, digestive tract, liver, pancreas, and part of the lungs

Question 24

primitive streak

Answer 24

elongated band of cells that forms along the axis of a developing embryo early in gastrulation

Question 25

primitive node

Answer 25

area through which migrating cells are channeled into a rod-like structure of mesenchymal cells

Question 26

notochord

Answer 26

a cartilaginous skeletal rod formed by the gathering of the primitive nodes mesenchymal cells

Question 27

trilaminar disc

Answer 27

gastrulation: ectoderm, mesoderm, and endoderm

Question 28

neurlation

Answer 28

folding process of the embryo

Question 29

neural plate

Answer 29

elongated structure formed as the developing notochord induces the overlying ectoderm at the midline to thicken; giving rise to the CNS, brain, and spinal cord

Question 30

neural groove

Answer 30

formed by infolding neural fold cells from endoderm; closes the neural tube

Question 31

somites

Answer 31

precursor populations of cells that give rise to important structures in the vertebrate body plan

Question 32

intermediate mesoderm

Answer 32

generates urogenital system (kidneys, gonads, and reproductive duct systems)

Question 33

lateral plate mesoderm

Answer 33

generates hear, cardiovascular system, blood, kidneys, smooth muscle, and limb muscles