Embryology

Question 1

describe the early stages of limb development

Answer 1

begins near the end of the 4th week
usually upper limb begins first, day 24 limbic bud appears
it elongates by the proliferation of the mesenchyme in the somatic layer of mesoderm

Question 2

what is the apical ectodermal ridge

Answer 2

at the end of each limb bud multi-layered epithelial structure
consists of undifferentiated rapidly proliferating cells

Question 3

describe the development of hand and foot plates

Answer 3

begin to flatten into paddles and flippers by the end of the 6th week
during the 7th week digital rays are formed on the foot plates
the fingers are then sculpted using apoptosis

Question 4

what is the cell apoptosis mediate dby

Answer 4

bone morphogenetic proteins

Question 5

describe limb rotation

Answer 5

upper and lower limbs rotate
upper limbs rotate 90 degrees laterally
lower limbs rotate medially 90

Question 6

describe polydactyl

Answer 6

presence of more than 5 digits on the hands and feet

can be inherited or teratogen

Question 7

describe syndactyly

Answer 7

limb defect of hand or foot
cutaenous-webbing
osseous-notches between fingers fail to develop

Question 8

describe the effects of thalidomide

Answer 8

used to be used as a sleep tablet

absence or deformity of long ones

Question 9

describe congenital clubfoot

Answer 9

also known as talipes equinovarus
sole of the foot turns medially
cause- multifactorial
restricted movement in the womb