At the completion of this chapter, the reader will be able to:
Describe the various types of biological tissue of the musculoskeletal system.
Describe the tissue mechanics and structural differences and similarities between muscle, tendons, fascia, and ligaments.
Define the various terminologies used to describe joint position, movements, and relationships.
Give definitions for commonly used biomechanical terms.
Describe the different planes of the body.
Describe the different axes of the body and the motions that occur around them.
Define the terms osteokinematic motion and arthrokinematic motion.
Differentiate between the different types of motion that can occur at the joint surfaces.
Describe the basic biomechanics of joint motion in terms of their concave–convex relationships.
Define the terms closepacked and openpacked.
Throughout the human body, there are four types of fundamental tissues:
- Epithelial. Covers all internal and external body surfaces and includes structures such as the skin and the inner lining of the blood vessels.
- Connective. Connective tissue (CT), which includes bone, cartilage, tendons, ligaments, and blood tissue, provides structural and metabolic support for other tissues and organs of the body.
- Muscle. Muscles are classified functionally as either voluntary or involuntary, and structurally as either smooth, striated (skeletal), or cardiac. There are approximately 430 skeletal muscles in the body, each of which can be considered anatomically as a separate organ. Of these 430 muscles, about 75 pairs provide the majority of body movements and postures.1
- Nervous. Nervous tissue provides a two-way communication system between the central nervous system (brain and spinal cord) and muscles, sensory organs, and various systems (see Chapter 3).
CT is divided into subtypes according to the matrix that binds the cells. CT proper has a loose flexible matrix, called ground substance. The most common cell within CT proper is the fibroblast. Fibroblasts produce collagen, elastin, and reticulin fibers. Collagen is a group of naturally occurring proteins. The collagens are a family of extracellular matrix (ECM) proteins that play a dominant role in maintaining the structural integrity of various tissues and in providing tensile strength to tissues. The ECM contains proteoglycans, lipids, water, and dissolved electrolytes. Proteoglycans, which are a major component of the ECM, are macromolecules that consist of a protein backbone to which are attached many extended polysaccharide units called glycosaminoglycans (GAGs), of which there are two types: chondroitin sulfate and keratin sulfate.2,3 A simple way to visualize the proteoglycan molecule is to consider a test tube brush, with the stem representing the protein core and the GAGs representing the bristles.4,5
The various characteristics of collagen differ depending on whether it is loose or dense collagen. The anatomic and functional characteristics of loose and dense collagen are summarized in Table 1-1. Collagenous and elastic fibers are sparse and irregularly arranged in loose CT but are tightly packed in dense CT.6 Elastic fibers are composed of a protein ...