Exam 1 Embryology

Question 1

fertilization

Answer 1

usually occurs in ampulla of Fallopian tube

occurs when sperm penetrates oocyte (zone pellucid, corona radiata)

Question 2

zygote

Answer 2

when the oocyte is fertilized and has all 46 chromosomes

Question 3

blastomeres

Answer 3

replicated cells of zygote

Question 4

cleavage

Answer 4

after fertilization, repeated divisions of zygote

Question 5

morula

Answer 5

around day 3, 12-16 blastomeres

Question 6

blastocyst

Answer 6

when the morula enters the uterine cavity, around day 4, and fluid enters separating inner mass and outer layer

Question 7

embryoblasts

Answer 7

inner layer of cells of blastocyst, embryo

Question 8

trophoblasts

Answer 8

outer layer of cells of blastocyst, placenta

Question 9

implantation

Answer 9

when blastocyst attaches to the epithelial lining of the uterus, around day 6
trophoblasts proliferate into 2 layers

Question 10

cytotrophoblasts

Answer 10

single nuclei of cells with defined membranes, from trophoblasts

Question 11

syncytiotrophoblasts

Answer 11

mass of multi-nucleated cells fused together

Question 12

week 2

Answer 12

bilaminar disc forms (epiblast, hypoblast)
amniotic sac from epiblast
yolk sac from hypoblast

Question 13

day 10

Answer 13

conceptus completely embedded
lacunae develop in syncytiotrophoblast
beginning of uteroplacental circulation

Question 14

gastrulation

Answer 14

day 15, primitive streak forms along midline of epiblasts; bilaminar becomes trilaminar

Question 15

trilaminar disc

Answer 15

epiblasts migrate medially towards primitive streak, replaces hypoblasts to become endoderm. Migrating cells become mesoderm, epiblast become ectoderm

Question 16

neurolation

Answer 16

when neural plate create a groove, and becomes neural tube

Question 17

notocord

Answer 17

invagination of cells from primitive node
caudal to cranial aspect of embryo
axis for embryo, rigidity
development of vertebral bodies

Question 18

neural plate

Answer 18

notochord induces overlying ectoderm to thicken; gives rise to CNS

Question 19

somites

Answer 19

paired blocks of mesoderm formed bilaterally along neural tube; week 4

Question 20

sclerotome

Answer 20

bone tissue of vertebral column from somites

Question 21

myotome

Answer 21

muscle of the trunk from somites

Question 22

dermatome

Answer 22

dermis of the skin from somites

Question 23

pharyngeal pouches

Answer 23

5 pairs of pockets, separated by pharyngeal arches; from in the walls of the future throat

Question 24

intramembranous ossification

Answer 24

1. bone formation from mesenchyme pithing a membranous sheath
2. mesenchyme condenses, vascularizes, osteoblasts form and deposit osteoid
3. produces most of the flat bones of the skull, most of the clavicle
4. role in thickening, developing, remodeling of long bones

Question 25

endochondral ossification

Answer 25

1. bone formation that occurs on pre-existing cartilage
2. primary ossifications centers are in diaphysis of long bones, ossify by birth
3. secondary centers are cartilaginous and ossify in the first few years of life
4. produces vertebrae, ribs, scapulae, pelvic bones, bones of limbs

Question 26

neurocranium base ossification

Answer 26

endochondral

Question 27

calvaria ossification

Answer 27

intramembranous

Question 28

viscerocranisum

Answer 28

intramembranouse from pharyngeal arches 1-2

Question 29

vertebral ossification

Answer 29

1. sclerotome becomes vertebral arches, endochondral
2. primary ossification centers (3): one at the centrum, 2 at each vertebral arch
3. secondary ossification centers (5): spinous process, TPs, superior and inferior annular epiphysis

Question 30

appendicular ossification

Answer 30

1. limb buds from mesenchymal condensations during week 5
2. week 6: mesenchyme to hyaline cartilage by chondrification
3. primary centers ossify during week 8

Question 31

What happens to the notochord?

Answer 31

becomes nucleus pulposus of IVD