Introductory concepts in limb anatomy

Published on May 31, 2021   23 min

Other Talks in the Series: Introduction to Gross Anatomy for Medicine

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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