Anatomy and Human Movement (eBook)

Structure and Function

Derek Field, Nigel Palastanga, Roger W. Soames (Autoren)

eBook Download: EPUB

2013 | 2. Auflage
904 Seiten
Elsevier Science (Verlag)
978-1-4831-4112-1 (ISBN)

Infos

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.

Textauszug

Terminology

Publisher Summary

The chapter lists some commonly used terms that describe the position of anatomical structures, such as anterior, posterior, superior, inferior, lateral, distal, proximal, superficial, and deep. Rarely do movements of one body segment with respect to another take place in a single plane. They almost invariably occur in two or three planes simultaneously producing a complex pattern of movement. However, it is convenient to consider movements about each of the three defined axes separately. Movement about a transverse axis occurring in the paramedian plane is referred to as flexion and extension; that about an antero-posterior axis in a coronal plane is termed abduction and adduction; and finally, that about a vertical axis in a transverse plane are medial and lateral rotation. All movements are described, unless otherwise stated, with respect to the anatomical position as the position of reference. In this position, joints are often referred to as being in a neutral position.

It is essential for the student beginning their study of anatomy to become familiar with an internationally accepted vocabulary, allowing communication and understanding between all members of the medical and paramedical professions throughout the world. Perhaps the single, most important descriptive feature of this vocabulary is the adoption of an unequivocal position of the human body. This is known as the anatomical position. It is described as follows: the body is standing erect and facing forwards; the legs are together with the feet parallel so that the toes point forwards; the arms hang loosely by the sides with the palm of the hand facing forward so that the thumb is lateral (Fig. A.1). All positional terminology is used with reference to this position, irrespective of the actual position of the body when performing an activity.

Fig. A.1 The anatomical position showing the cardinal planes and directional terminology.

The following is a list of more commonly used terms which describe the position of anatomical structures:

Anterior (ventral) To the front or in front, e.g. the patella lies anterior to the knee joint.

Posterior (dorsal) To the rear or behind, e.g. gluteus maximus lies posterior to the hip joint. (Ventral and dorsal are used more commonly in four-legged animals.)

Superior (cephalic) Above, e.g. the head is superior to the trunk.

Inferior (caudal) Below, e.g. the knee is inferior to the hip.

Cephalic (the head) Caudal (the tail) May be used in relation to the trunk.

Lateral Away from the median plane or midline, e.g. the little toe lies lateral to the big toe.

Medial Towards the median plane or midline, e.g. the little finger lies medial to the thumb.

Distal Away from the trunk or root of the limb, e.g. the foot is distal to the knee.

Proximal Close to the trunk or root of the limb, e.g. the wrist is proximal to the hand.

Superficial Close to the surface of the body or skin, e.g. the ulnar nerve passes superficial to the flexor retinaculum of the wrist.

Deep Away from the body surface or skin, e.g. the tendon of tibialis posterior passes deep to the flexor retinaculum at the ankle.

To facilitate the understanding of the relation of structures one to another and the movement of one segment with respect to another, imaginary reference planes pass through the body in such a way that they are mutually perpendicular to each other (Fig. A.1). Passing through the body from front to back and dividing it into two symmetrical right and left halves is the sagittal (median) plane. Any plane parallel to this is also known as a sagittal (paramedian) plane.

A plane passing through the body from top to bottom and lying at right angles to the sagittal plane is the coronal (frontal) plane. This divides the body into anterior and posterior parts. All planes that divide the body in this way are known as coronal planes. Finally, a plane passing through the body at right angles dividing it into upper and lower parts is known as a transverse (horizontal) plane. A whole family of parallel transverse planes exist; it is therefore usual when presenting a particular transverse section to specify the level at which it is taken. This may be done by specifying the vertebral level or the position within the limb, e.g. C6 or midshaft of humerus respectively.

Within each plane a single axis can be identified, usually in association with a particular joint, about which movement takes place. An anteroposteriorly directed axis in the sagittal (or a paramedian) plane allows movement in a coronal plane. Similarly, a vertical axis in a coronal plane allows movement in a transverse plane. Lastly a transverse (right to left) axis in a coronal plane provides movement in a paramedian plane.

By arranging that these various axes intersect at the centre of joints, the movements possible at the joint can be broken down into simple components. It also becomes easier to understand how specific muscle groups produce particular movements, as well as determining the resultant movement of combined muscle actions.

LEVERS

An understanding of the action and principle of levers is of considerable use when considering the application of the forces applied to bones. The following is a simplified description of the mechanics of levers and how they are applied in the human body.

A lever may be considered to be a simple, rigid bar, with no account taken of its shape or structure. Most long bones appear as rigid bars but although many bones, such as those of the skull, are far from the usual concept of a lever they can, nevertheless, still act in this way.

The fulcrum is the point around which the lever rotates. That part of the lever between the fulcrum and point of force application is known as the force arm, and that between the fulcrum and the point of load application is known as the load arm. This concept is easy to understand when applied to a child’s seesaw (Fig. A.2a). Different arrangements of the fulcrum, load and force arms produce different classes of lever. There are three possible arrangements: a first class lever has the fulcrum between the load and force arms; a second class lever has the fulcrum at one end and the applied force at the other, with the load situated between them; a third class lever again has the fulcrum at one end but the load at the other with the applied force between (Fig. A.2b).

Fig. A.2 Levers: a) child’s see-saw; b) classes of lever.

All three classes of lever are found within the human body; the fulcra are usually situated at the joints; the load may be body weight or some external resistance, with the force usually being produced by muscular effort. It is the complex arrangement of all three classes of lever within the human body that produces movement.

A first class lever is used in balancing weight and/or changing the direction of pull. There is usually no gain in mechanical advantage, e.g. when standing on the right lower limb the fulcrum is the right hip joint, the load being body weight to the left of the hip, while the force is provided by the contraction of the right gluteus medius and minimus muscles.

A second class lever (the principle on which weight is lifted in a wheelbarrow), gains mechanical advantage thereby allowing large loads to be moved, but with a loss of speed. Raising up onto the toes is a good example of such a system; the metatarsal heads act as the fulcrum, the weight of the body acting down through the tibia is the load while the calf muscles contract to produce the required force. The load arm is thus the distance from the tibia to the metatarsal heads, while the force arm is the distance between the attachment of the calf muscles to the calcaneus and the metatarsal heads.

A third class lever is the most commonly found within the body. It works at a mechanical disadvantage moving less weight but often at great speed. The biceps brachii acting across the elbow is a good example of this class of lever. The elbow is the fulcrum, the weight is the forearm and hand being supported, with the force being provided by biceps. In this example the load arm is the distance between the elbow and centre of mass of the forearm and hand, whereas the force arm is the distance between the elbow joint and the attachment of biceps.

All movements of the human body are dependent on the interaction of these three classes of lever. It is well to remember when studying the structure of the human body the relationship between the joints, the attachment of relevant muscles and the load to be moved. This will lead to an understanding of functional anatomy and with it human movement.

TERMS USED IN DESCRIBING MOVEMENT

Rarely do movements of one body segment with respect to another take place in a single plane. They almost invariably occur in two or three planes simultaneously producing a complex pattern of movement. However, it is...

Produkt-Details

• Erscheint lt. Verlag: 22.10.2013
• Sprache: englisch
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Anatomie / Neuroanatomie
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Physiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Humanbiologie
• ISBN-10: 1-4831-4112-8 / 1483141128
• ISBN-13: 978-1-4831-4112-1 / 9781483141121