Lecture 3

Question 1

what forms somites along the spinal cord and somitomeres in the head?

Answer 1

paraxial mesoderm

Question 2

3 components of a somite

Answer 2

dermatome (skin)
myotome (muscle)
sclerotome (bone)

Question 3

tissues derived from the mesodermal germ layer

Answer 3

mesoderm

Question 4

any loose connective tissue regardless of origin

Ex: neural crest cells

Answer 4

mesenchyme

Question 5

2 parts of neurocranium

Answer 5

1. membranous: flat bones, intramembranous ossification

2. chondocranium: formed cartilage model first then ossification: bones of the base

Question 6

the prechordal portion of the chondrocranium (part of neurocranium) is derived from the ______

Answer 6

neural crest (cranial to pituitary)

Question 7

everything on the chondrocranium (part of the neurocranium) except the prechordal portion is derived from the _______

Answer 7

paraxial mesoderm

Question 8

narrow seams of connective tissue that separate the flat bones of the skull allowing molding of the skull through the birth canal and growth and expansion as the brain grows
Ex: coronal, sagittal, etc.

Answer 8

suture

Question 9

larger spaces between the bones of the skull

“soft spots” in babies

Answer 9

fontanelles

Question 10

early fusion of the sutures of the skull in babies
abnormal skull
many defects result from mutations in fibroblast growth factor receptors (FGFRs)

Answer 10

craniosynostosis

Question 11

facial part of the skull
mostly from the frontonasal prominence and the 1st and 2nd pharyngeal arches
formed from neural crest cells

Answer 11

viscerocranium

Question 12

first pharyngeal arch portion of viscerocranium

Answer 12

maxilla
mandible
malleus
incus

Question 13

second pharyngeal arch portion of viscerocranium

Answer 13

stapes

part of hyoid bone

Question 14

limb buds form furing 4th and 5th weeks

positions specified by ________

Answer 14

HOX genes

Question 15

gene that specifies forelimb structures

Answer 15

TBX5 gene

Question 16

gene that specifies hindlimb structures

Answer 16

TBX4 gene

Question 17

layer of thickened ectoderm at the distal tip of the limb that controls outgrowth of the limb by maintaining a rapidly proliferating population of adjacent mesoderm cells
FGFs maintain a rapidly proliferating population of cells adjacent to the ridge
“progress zone”

Answer 17

apical ectodermal ridge (AER)

Question 18

occurrence that allows formation of digits

separates each finger

Answer 18

cell death (apoptosis) in the ridge

Question 19

cranial to caudal (anterior-posterior) patterning

thumb to little finger

Answer 19

zone of polarizing activity (ZPA)

Question 20

two morphogens that control the zone of polarizing activity (ZPA)

Answer 20

sonic hedgehog (SHH) and retinoic acid

Question 21

genes that control bone patterning

Answer 21

HOX genes

Question 22

defect that causes no limbs

Answer 22

Amelia

Question 23

defect that causes short limbs

partial absence of a limb

Answer 23

Meromelia

Question 24

anti-nausea drug that causes limb defects in newborns
now an anti-cancer, anti-AIDS drug
seeing limb defects again

Answer 24

Thalidomide

Question 25

defect that causes too many digits

Answer 25

polydactyly

Question 26

defect that causes fused digits

Answer 26

syndactyly

Question 27

defect that causes short digits

Answer 27

barchydactyly

Question 28

from what two things is the vertebral column derived from?

Answer 28

somites (sclerotome)

notochord (nucleus pulposus of intervertebral disc)

Question 29

when forming the vertebral column, what allows for movement between vertebra?

Answer 29

caudal part of one sclerotome fuses with cranial part of another
intersegmental so that muscles bridge the vertebra to act on them

Question 30

intersegmental fusion of sclerotome with cranial part of another
muscles bridge the vertebra to act on them and allow movement

Answer 30

resegmentation

Question 31

epithelial balls of cells formed in segmental pairs along the neural tube from paraxial mesoderm
differentiate into vertebrae, muscles of the back and body wall, and dermis of the skin

Answer 31

somites

Question 32

loosely organized segmented collections of paraxial mesoderm in the cranial region
form muscles and bones of the face and skull

Answer 32

somitomeres

Question 33

secreted protein that acts as a morphogen in several emybryonic sites: limbs, somites, guy formation, and establishment of the id-line in the CNS

Answer 33

sonic hedgehog (SHH)

Question 34

shaft of the long bone

Answer 34

diaphysis

Question 35

end of long bone

Answer 35

epiphysis

Question 36

proliferating population of mesenchyme cells immediately beneath the apical ectodermal ridge (AER)
by signaling through FGFs, the AER maintains this and promotes proximodistal growth of the limb

Answer 36

progress zone