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My name is Carol Hartmann and I'm from
the University of the Witwatersrand in South Africa.
I'd like to discuss some basic principles and
concepts in musculoskeletal anatomy that are useful for
understanding how the skeletal system functions, and
clinical applications of musculoskeletal anatomy.
The structure of the peripheral nervous system is
another important concept related to the musculoskeletal system, and
I encourage you to also review the introductory lecture on the nervous system.
In this lecture, we will begin by discussing bones and how the microstructure and
classification of a bone relates to its function
in the musculoskeletal system, and its blood supply.
We will also discuss how these concepts relate to fractures and fracture healing.
Next, we will discuss the compartmental arrangement of
the limb muscles and functional classification in muscles,
relating these concepts to muscle dysfunction.
Finally, we will discuss the classification of joints,
relating the structure of joints to their function and stability,
an important concept when discussing dislocations.
Let's start by discussing the bones.
Knowledge of bone microstructure allows us to
understand how forces can be distributed through bones.
The commonest histological type of bone within
the adult skeleton is lamellar or mature bone,
in which the bone matrix is laid down in layers.
Lamellar bone can either be classified as cortical bone
(also known as compact bone) or trabecular bone
(also called cancellous/spongy bone).
Cortical bone is found on the cortex or outer surface of bones,
although in some instances,
the entire thickness of the bone will be composed of cortical bone.
In cortical bone, the layers of the bone matrix, minerals
and cells are arranged circumferentially around
a central canal that contains blood vessels and nerves.
Each central canal and the surrounding circumferential layers are called an 'osteon'.
Osteons resist force that acts parallel to the long axis or length of the osteon.
As the long axes of osteons are parallel,
cortical bone is best able to resist force from a single direction,
such as the forces that occur during muscle contraction or weight bearing.
In trabecular bone, the cells and bone matrix are arranged in spicules
or trabeculae, pointing in different directions like poles in scaffolding.
Each trabeculum is able to withstand
compressive force acting parallel to its long axis or length.
As the trabeculae are arranged in multiple directions,
trabecular bone withstands force from multiple directions, and is
therefore found in areas of bones which experience forces from multiple directions.
Trabecular bone is found deep to
cortical bone, and the arrangement of the bone into trabeculae
allows the amount of bone in an area to be
increased while keeping the weight of the bone to a minimum.
Bones either lie within the axial skeleton