mechanisms of disease during embryogenesis

Question 1

what are the two main periods in human development

Answer 1

1. embryonic period = up to end of week 8 and most of organogenesis occurs in these first 8 weeks
2. fetal period = remaining time in utero. involves growth and modelling

Question 2

what are the mechanisms of development

Answer 2

from egg:

• fertilisation
• cleavage
• gastrulation
• neurulation and somitogenesis
• organogenesis

to adult

Question 3

describe gastrulation

Answer 3

from 2 layers to 3

hypoblast is displaced by involuting cells that become definitive endoderm and mesoderm

Question 4

describe organogenesis

Answer 4

differentiation of somatic derivatives = bones, muscles, tendons

development of sensory organs = ears, eyes, olfactory pits

limb formation = forelimbs first, hindlimb next
establishment of pattern in limbs, proximodistal, anterior-posterior, dorsal ventral

formation of face structures = jaws, nose, tongue, palate

• formation of genital structures