Anatomy and Human Movement

Structure and Function

Nigel Palastanga,Derek Field,Roger W. Soames

• Publisher: Butterworth-Heinemann
• Year: 2013
• ISBN:
  9781483141121
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Human Anatomy & Physiology
• Index: Biological Sciences

Anatomy and Human Movement: Structure and Function, Second Edition, is concerned with the musculoskeletal system and its application to human movement. The design of this new edition builds on the success of the first edition. There has been some reorganization of the text and illustrations for better clarity, as well as new sections on the cardiovascular, respiratory, digestive and urogenital systems, and on the eye and ear. Apart from introductory sections (terminology; components of the musculoskeletal system; embryology; and skin, its appendages and special senses), the book has three sections dealing with the musculoskeletal system: the upper limb, the lower limb, and the head, neck and trunk. In addition there is a fourth section on the nervous system. Each musculoskeletal section is presented in a similar way beginning with a study of the bones, to provide the basic framework of the section. This is followed by a description of the muscles, which are considered in functional groups in an attempt to explain how movement is produced. Finally, the joints are described and discussed, building on the knowledge gained from a consideration of the bones and muscles: this last part of each section also serves to bring together the preceding parts. This book was written for the student of anatomy who wishes to use this knowledge functionally and desires an understanding of the mechanisms enabling movement to take place.

1

Components of the musculoskeletal system

Publisher Summary

This chapter discusses the components of musculoskeletal system. Skeletal tissues are modified connective tissues, whereby the cells and fibres have a particular organization that becomes condensed so that the tissue is rigid. Within the body there are three varieties of muscle: (1) smooth muscle also referred to as involuntary or non-striated muscle; (2) cardiac muscle, and (3) skeletal muscle, also known as voluntary or striated muscle. Smooth muscle forms the muscular layer of the walls of blood vessels and of hollow organs such as the stomach. The chapter also reviews that the bones of the body come together to form joints. It is through these articulations that movement occurs. However, the type and extent of the possible movement depend on the structure and function of the joint. Moreover, the variation that exists in the form and function of the various joints of the body allows the joints to be grouped into well-defined classes: fibrous, cartilaginous, and synovial with the degree of mobility gradually increasing from fibrous to synovial.

As this book is concerned essentially with the musculoskeletal system a brief account of the major tissues of the system, i.e. connective, skeletal and muscular tissue, and of the type of joints which enable varying degrees of movement to occur, is given below in the hope that it will aid in the understanding of the mobility and inherent stability of various segments. The initiation and coordination of movement is the responsibility of the nervous system; an account of the basic components of that system is reserved until the appropriate section.

CONNECTIVE TISSUE

Connective tissue is of mesodermal origin and in the adult has many forms, the character of the tissue depending on the organization of its constituent cells and fibres.

Fat

Fat is a packing and insulating material; however, in some circumstances it can act as a shock absorber, an important function as far as the musculoskeletal system is concerned. Under the heel, the buttock and the palm of the hand, the fat is divided into lobules by fibrous tissue septa thereby stiffening it for the demands made upon it.

Fibrous tissue

Fibrous tissue is of two types. In white fibrous tissue there is an abundance of collagen bundles, whereas in yellow fibrous tissue there is a preponderance of elastic fibres.

White fibrous tissue is dense thereby providing considerable strength without being rigid or elastic. It forms: (1) ligaments, which pass from one bone to another in the region of joints, uniting the bones and limiting joint movement; (2) tendons for attaching muscles to bones; and (3) protective membranes around muscle (perimysium), bone (periosteum) and many other structures.

Yellow fibrous tissue, on the other hand, is highly specialized, being capable of considerable deformation and yet returning to its original shape. It is found in the ligamenta flava associated with the vertebral column as well as in the walls of arteries.

SKELETAL TISSUE

Skeletal tissues are modified connective tissues, whereby the cells and fibres have a particular organization which becomes condensed so that the tissue is rigid.

Cartilage

Cartilage is supplementary to bone, being formed wherever strength, rigidity and some elasticity are required. In fetal development, cartilage is often a temporary tissue being later replaced by bone. However, in many places cartilage persists throughout life. Although a rigid tissue, cartilage is not as hard or strong as bone. It is also relatively non-vascular being nourished by tissue fluids. A vascular invasion of cartilage often results in the death of the cells during the process of ossification of the cartilage and its eventual replacement by bone. Except for the articular cartilage of synovial joints, cartilage possesses a fibrous covering layer, the perichondrium.

There are three main types of cartilage: hyaline cartilage, white fibrocartilage and yellow fibrocartilage.

Hyaline cartilage

This forms the temporary skeleton of the fetus from which many bones develop. Its remnants can be seen as the articular cartilages of synovial joints, the epiphyseal growth plates between parts of an ossifying bone during growth, and the costal cartilages of the ribs. At joint surfaces it provides a certain degree of elasticity to offset and absorb shocks, as well as providing a relatively smooth surface permitting free movement to occur. With increasing age, hyaline cartilage tends to become calcified and sometimes ossified.

White fibrocartilage

White fibrocartilage contains bundles of white fibrous tissue which give it great tensile strength combined with some elasticity so that it is able to resist considerable pressure. It is found at many sites within the musculoskeletal system: (1) within the intervertebral discs between adjacent vertebrae; (2) in the menisci of the knee joint; (3) in the labrum deepening the glenoid fossa of the shoulder joint and the acetabulum of the hip joint; (4) in the articular discs of the wrist, sternoclavicular, acromioclavicular and temporomandibular joints, and (5) as the articular covering of bones which ossify in membrane, e.g. the clavicle and mandible.

White fibrocartilage may calcify and ossify.

Yellow fibrocartilage

Yellow fibrocartilage contains bundles of elastic fibres with little or no white fibrous tissue. It does not calcify or ossify, and is not found within the musculoskeletal system.

Bone

Bone is extremely hard with a certain amount of resilience. It is essentially an organic matrix of fibrous connective tissue impregnated with mineral salts. The connective tissue gives the bone its toughness and elasticity, while the mineral salts provide hardness and rigidity, the two being skilfully blended together. It must be remembered that the mineral component provides a ready store of calcium, which is continuously exchanged with that in body fluids, with the rate of exchange and overall balance of these mineral ions being influenced by several factors including hormones.

Each bone is enclosed in a dense layer of fibrous tissue, the periosteum, with its form and structure adapted to the function of support and the resistance of mechanical stresses. Being a living tissue, bone is continually being remodelled to meet these demands; this is particularly so during growth. The structure of any bone cannot be satisfactorily considered in isolation, for it is dependent upon its relationship to adjacent bones and the type of articulation between them, as well as the attachment of muscles, tendons and ligaments to it.

The internal architecture of bone reveals systems of trabeculae running in many directions (Fig. 1.1), arranged to resist compressive, tensile and shearing stresses. Surrounding these trabecular systems, which tend to be found at the ends of long bones, is a thin layer of condensed or compact bone (Fig. 1.1). The network of the trabeculae, because of its appearance, is known as cancellous or spongy bone. In the region of the shaft of a long bone is an outer, relatively thick ring of compact bone surrounding a cavi...