Download HUMAN FUNCTIONAL ANATOMY 213 THE UPPER LIMB EARLY

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HUMAN FUNCTIONAL ANATOMY 213
THE UPPER LIMB
EARLY LIMB DEVELOPMENT
IN THE FISH (or early human embryo)
Slight elevations of ectoderm appear in lateral plate (4th week).
Apical ectodermal ridge induces proliferation of limb mesenchyme.
Dorsal and ventral muscle masses connect the girdle to the limb bud.
Limb girdle in body wall
Proximal, middle and distal segments of the limb
THIS WEEKS LAB:
Proximal parts, plexuses and patterns
READINGS
Stern. Essentials of Gross anatomy – The upper limb
Stern. Core concepts in Anatomy:- 80: Organization of upper limb musculature and the
brachial plexus
Faiz and Moffat. Anatomy at a Glance:- Nerves of the Upper limb 1 & 2 (parts 30 &31)
Grant's Method:- Upper limb and Back (especially pectoral region and axilla)
OR any other regional textbook - similar sections
IN THIS LECTURE I WILL COVER:
Ontogeny and Phylogeny
The Pectoral fin
The primitive tetrapod forelimb
Rotations of the limb in phylogeny
Dorsal and ventral muscle/nerve/girdle bone
Segmental nerve supply and muscle groups
Brachial plexus
The fin, or paddle has:
Preaxial and postaxial borders (front and back edges)
Dorsal and ventral surfaces (top and bottom)
Dorsal muscles elevate the fin.
Attach to dorsal elements of the girdle (“scapula” and vertebrae)
Ventral muscles depress the fin.
Attach to ventral elements of the girdle (coracoid)
Muscle groups of the upper limb
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PRIMITIVE TETRAPOD FORELIMB
The characteristic segments of the limb (shoulder, arm, forearm, & hand)
Were present in the fins of fossil fish
But became fully developed in terrestrial forms (amphibia & reptiles)
The orientation of the limb is still the same:
Dorsal is dorsal and Ventral is ventral
Pre-axial (thumb side) is front edge of
limb
The limbs and mode of locomotion are very similar in fish & reptiles
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MAMMALIAN FORELIMB ROTATIONS
90 degrees LATERAL ROTATION
The preaxial border (thumb side) becomes dorsal
This brings the dorsal muscles to the posterior aspect of the limb
and the ventral muscles to the anterior aspect
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MAMMALIAN FORELIMB ROTATIONS
90 degrees ADDUCTION
DORSAL AND VENTRAL MUSCLES
The limb rotations modify the action of the muscles
Primitive dorsal elevators and ventral depressors of the fin
Become dorsal extensors, and ventral flexors of the limb
Adduction brings the limb under the trunk. (Classic mammalian posture)
Preaxial border (thumb side) becomes lateral
Dorsal muscles remain on the posterior aspect of the limb
Dorsal muscles either:
Attach to the vertebral column or the true scapula
or Lie in dorsal compartments of the limb
Ventral muscles either:
Attach to the coracoid part of the scapula, clavicle, ribs or sternum
or Lie in ventral compartments of the limb
Quadrupedal animals
pronate their forearm
that the digits face forwards
so
In humans the limb stays in the same orientation, but we stand on our hindlimbs
and the upper limb hangs at our side (90 degrees extension)
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Dorsal and Ventral
MUSCLE COMPARTMENTS OF THE UPPER LIMB
And their Dorsal and Ventral nerves
Ventral:
Musculocutaneous nerve (C56)
Anterior compartment of the arm
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BRACHIAL PLEXUS
TRUE LIMB MUSCLES ATTACH TO LONG BONES OF THE LIMB
The brachial plexus supplies all these muscles.
This excludes muscles attaching the axial skeleton to the scapula.
These muscles are derived from cranial or cervical myotomes
Eg. Trapezius and sternomastoid - Accessory nerve CN 11
Serratus anterior, rhomboids, levator scapulae - C3,4,5,6
C5
Dorsal:
Radial nerve (C5678T1)
C6
C7
C8
T1
ROOTS
Posterior compartment of the arm
TRUNKS
Upper
Middle
Lower
Ventral:
Median nerve C5678T1
Anterior compartment of the forearm
DIVISIONS
Anterior and posterior for each trunk
Dorsal:
Radial nerve (C5678T1)
CORDS
Lateral
Posterior
Medial
Posterior compartment of the forearm
Ventral:
NERVES
Musculocutaneous
Median
Ulnar nerve (C8T1)
Hand
Axillary
Radial
Ulnar
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BRACHIAL PLEXUS
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MUSCLE COMPARTMENTS OF THE UPPER LIMB
Basis of the brachial plexus
Compartment
Anterior shoulder
Ventral
Segments
C5 & C6
Nerve
Pectoral nerves
Posterior shoulder
Dorsal
C5 & C6
Axillary
Suprascapular
Subscapular & thoracodorsal
Anterior arm
Ventral
C6 &
Musculocutaneous
Posterior arm
Dorsal
C6 &
Radial nerve
Posterior forearm
Ventral
C7 &
Radial nerve
Anterior forearm
Ventral
C7 &
Median (and ulnar) nerves
Hand
Ventral
C8 & T1
Ulnar (and median) nerve
The brachial plexus is how the nerves of the upper limb are formed.
You can see the need for a plexus, otherwise there would be a mess of tiny nerves.
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“ONTOGENY RECAPITULATES PHYLOGENY”
Ernst Haeckel
Ontogeny = The development of the individual
Phylogeny = Evolution of the species
The development of the individual recapitulates
the evolution of the species
Classic example is the Development of the frog.
Retracing the evolution of vertebrates from fish to reptiles
From the tadpole stage (like a fish)
1.
2.
3.
4.
5.
Water breathing creature with tail and no limbs
Rudimentary limbs
Reduction of tail
Breathes air
Fully developed limbs,, loss of tail, becomes a land animal.
To the fully developed frog
I WANT TO TRACE THE DEVELOPMENT OF THE LIMBS IN
VERTEBRATES AND COMPARE IT TO THE GROWTH OF LIMBS IN
THE INDIVIDUAL