Orgins of limbs + scapular movement list

explain the development of limb bones

1. lateral mesoderm condensation

—this is the process of cellular tissues condensing, they congregate and continue to divide/grow

1. cartilage formation

—then a cartilagenous skeleton grows

—hyaline cartilage (firmest of our cartilages) then only the epipheseal growth plates are leftover

1. bone formation

—the cartilage ossifies and becomes bone

—this is the second month of development

the upper and lower limbs were built very similarly, why are they different?

—more stable (lower limb) vs more mobile (upper limb)

—power (lower limb) vs direction and balance (upper limb)

think about in evolution the forelimbs were meant for steering (when a dog is running)(forelimbs steer and hindlimbs propel them forward-power)

explain what’s happening here

this is still a cross-section through the embryo-this time with limb buds

—ventral muscles on top of cartilage/bone (anterior)

—dorsal strap on posterior

so now what is happening here

a little farther along in development the outmost body wall layer is annexed by the upper limb

—the annex means that the outermost body wall helps to stabilize the upper limb

what happens with the mammalian limb that is special here

where are the ventral and dorsal muscles in the upper and lower limbs (visualize image)

what happens to the muscle-nerve relationship

since humans are bipedal, we had to stand up from the reptile (belly to floor) position

—upper and lower limbs are flipped

upper limb: ventral=top, dorsal=bottom

lower limb: ventral=bottom, dorsal=top

muscle-nerve relationship: anterior rami branch into an anterior and posterior devision

anterior devision goes ventral, posterior devision goes dorsal (the patterns stay the same, but the nerves turn in our bodies)

—before limbs rotated, nerves have already been hooked up

what would happen if our limbs didn’t rotate (visualize image)

which way do our limbs rotate

scary spider reptile thing would happen

upper limbs rotate laterally (ventral on top, dorsal on bottom)

lower limbs rotate medially (dorsal on top, ventral on bottom)

anatomy of a muscular compartment (muscles of the same compartment will have similar actions/innervations/vasularizations)

name

limb fascia

name

intermuscular compartment

—the fascia dives deep into the limb

—creates a division between muscles

—blends into periosteum

name

upward rotation

—tilt scapula upwards

name

downward rotation

—sets back to normal position

name

adduction

name

abduction

name

elevation

name

depression