ch.3 embryology week 4

Question 1

week 4: folding of the embryo
-general body form:

Answer 1

established by the folding of the flat trilaminar embryonic disc into a cylindrical embryo.

Question 2

week 4: folding of the embryo
-planes where folding occurs:

Answer 2

the sides of the disc fold in a medial direction, while at the same time, the head and tail regions fold under due to the rapid expansion of the brain and lengthening of the spinal cord.

Question 3

week 4: folding of the embryo
-result by day 24:

Answer 3

the embryo acquires a tadpole shape

Question 4

week 4: folding of the embryo
-primitive gut:

Answer 4

tubular yolk sac, pinched and enclosed due to the cylindrical folding.
-this tube is lined with endoderm and gives rise to the future digestive system and respiratory tube

Question 5

week 4: folding of the embryo
-elements present by the end of week 4

Answer 5

-roughly tadpole shaped embryo
-adult body plan is established: skin, outer and inner body wall
-skin on outside; ectoderm components
-outer body wall composed of ectoderm and somatic lateral mesoderm
-ventral body cavity established: coelom
-pinched off yolk sac: makes digestive and respiratory tube

Question 6

week 4: germ layer derivatives
-ectoderm

Answer 6

-brain and spinal cord
-epidermis, hair, nails , skin glands
-sensory nerve cells and ganglia: neural crest cells
-facial bones

Question 7

week 4: germ layer derivatives
-endoderm

Answer 7

epithelial lining and glands of gastrointestinal and respiratory tract

Question 8

week 4: germ layer derivatives
-mesoderm
-notochord:

Answer 8

persists as nucleus pulposus of intervertebral dics

Question 9

week 4: germ layer derivatives
-mesoderm
-somites

Answer 9

vertebrae and ribs
-dermis of skin of the dorsum of the body
-trunk and limb musculature

Question 10

week 4: germ layer derivatives
-mesoderm
-intermediate mesoderm

Answer 10

kidneys and gonads (internal reproductive organs)

Question 11

week 4: germ layer derivatives
-mesoderm
-lateral plate mesoderm

Answer 11

-wall of digestive and respiratory tubes; splanchnic
-heart and blood vessels: splanchnic
-dermis of the ventral body region; somatic
-connective tissue of the limbs (bones, joints, and ligaments); somatic

Question 12

week 4: somite derivatives
-somites divide into:

Answer 12

-scleratome
-dermatome
-myotome

Question 13

week 4: somite derivatives
-scleratome: (hard piece)

Answer 13

cells migrate medially, gather around the notochord and neural tube, and become the vertebrae and ribs

Question 14

week 4: somite derivatives
-dermatome (skin piece)

Answer 14

cells migrate to more superficial layers= dermis of skin on the dorsum of the body

Question 15

week 4: somite derivatives
-myotome (muscle piece)

Answer 15

remaining cells form the trunk and limb musculature