Chapter 8, Problem 20DYB

Summary Introduction

To determine:

Development of limbs, the germ layers that form the limb bud, and major events during each week of limb development.

Concept introduction:

Limb buds are formed in the appendicular skeleton in the $4^{\text{th}}\text{week}$ of gestation. Upper limb buds appear a few days earlier than the lower limb buds. Thus, the development of lower limbs lags behind about $\text{2}\text{to}\text{4}\text{days}$ than upper limbs. The proximal parts of the limbs differentiate earlier than the distal parts.