Embryonic period

Question 1

what will the ectoderm, mesoderm and endoderm form?

Answer 1

ectoderm - organs, strucutres that maintain contact with outside e.g. nerverous system and epidermis

mesoderm - supporting tissue e.g. muscle, cartilage and bone and vascular system

Endoderm - internal surfaces e.g. lining of GI and respiratory tract

Question 2

how is left and right defined?

Answer 2

action of ciliated cells at the node result in left ward flow of signalling molecules

side specific signalling cascades are initiated

Question 3

what occurs from immotile cilia at the primative node?

Answer 3

situs inversus

complete mirror image viscera

Question 4

Give two examples of twinning

Answer 4

embryo splits after first cleavage

inner cell mass duplicates

duplication of primative streak

Question 5

what is teratogenesis

Answer 5

the process of normal embryonic development is disrupted

each organs system has a sensitive window within the embryonic period

some chemcial and infectious agesnt can cause developmental defects e..g thalidomide, rubella and alcohol

Question 6

Give the different fates of mesoderm

Answer 6

notochord
paraxial = axial skeleton
somatic = connective tissue, bone of limbs and dermis of skin of body wall
splanchnic = smooth musculature, connective tissue and vasculature of gut
intermediate = urogential system

Question 7

Describe gastrulation

Answer 7

process establishing the three germ layers and hence the origin of all tissues of the body

Question 8

Give the key things that have occured by the end of week 4

Answer 8

nervous system has started to form in neurulation
segments have appears assigning specific tasks to specific cells in the organisation of the mesoderm
the embryo has folded putting everything in the right place pulling the amniotic membrane around the disc and the embryo suspended in the amniotic sac.