growth and development

Question 1

when do limbs begin to form

Answer 1

day 24 upper limb
day 26 lower

Question 2

features indicating skeletal dysplasia

Answer 2

Short stature.
Large head with a prominent forehead.
Long trunk, shorter arms, and legs.
Brittle teeth and bones.
Hearing loss.
Cleft palate.
Vision problems.
Hydrocephalus.
Shortening in the bones of the legs and/or arms.
Bowed or fractured bones.
A small thorax.
Abnormal ribs.
Absence of a limb.
Asymmetric bone growth (e.g., one leg is longer than the other)
Duplication of fingers or toes.
Irregular, thickened or thin bones.

Question 3

why growth disturbance can occur

Answer 3

failure of production/ release of growth hormone releasing hormone
genetics
poor absorption of food
systemic illness’
vitamin def
growth plate injury/arrest

Question 4

limb development problems

Answer 4

overgrowth/undergrowth/complete/ partial absence

Question 5

how do bones grow

Answer 5

via the replacement of hyaline cartilage with bone. It begins when mesoderm-derived mesenchymal cells differentiate into chondrocytes

Question 6

how do chondrocytes form cartilage model for bone

Answer 6

proliferate rapidly and secrete an extracellular matrix

Question 7

how do limbs form

Answer 7

when mesenchyme cells proliferate from the somatic layer of the limb field lateral plate mesoderm and from the somites

Question 8

what forms bone

Answer 8

lateral mesoderm

Question 9

what forms muscle

Answer 9

lateral mesoderm