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In This Chapter: Terms and Concepts Worth Knowing 19 Anatomical Position 19 Directional Terms 19 Planes of the Body 19 Joint Movements 20 The Musculoskeletal System 23 Bones of the Human Body 24 Bone Shape 24 Bone Classification 24 Bone Composition 25 Effect of Fitness on Bone 25 The Human Skeleton 25 Joints of the Human Body 32 Classification of Joints 32 Joints of the Pectoral Girdle 36 Joints of the Upper Limb 37 Joints of the Pelvic Girdle 38 Joints of the Lower Limb 39 Muscles of the Human Body 42 Muscles of the Face 42 Muscles of the Neck and Back 43 Muscles Connecting the Humerus and Scapula to the Axial Skeleton 46 Muscles of the Arm 48 Muscles of the Forearm 49 Muscles of the Hand 49 Muscles of the Pelvic Girdle 50 Muscles of the Thigh 51 Muscles of the Leg 52 Muscles of the Foot 54 Muscles of the Abdomen 54 Summary 58 Let’s explore anatomy.... CHAPTER 2 Human Anatomy: The Pieces of the Body Puzzle After completing this chapter you should be able to: demonstrate an understanding of the basis for anatomical description and analysis; use correct anatomical terminology when describing the human body and performance; describe the various parts of the skeletal and muscular systems and the ways in which they relate to human performance; demonstrate an understanding of the organization and complexity of human anatomy. 17 Foundations of Exercise Science The human body has fascinated the human mind for centuries. What enables us to run, jump, and throw? How are we able to move our fingers with such remarkable dexterity? What are the structures that allow us to perform the myriad of tasks we do? The study of the structures that make up the human body, and how those structures relate to each other, is called human anatomy. Questions concerning human anatomy continue to capture the curiosity of human beings world-wide, because it is a subject that binds all humans together. An understanding of how our bodies are structured to perform is important if we are to gain our full potential, especially in the world of sport and physical activity. It is important to realize that structure often determines function; the structures of the human body are well-designed for efficient movement. You have probably marvelled at the strength of the human skeleton that is able to withstand great impact and stress, not to mention its light weight that allows movements to be swift and active. The human body is undoubtedly a strong, flexible, well-oiled machine, able to move and perform with astonishing efficiency (Figure 2.1). But what structures allow some power lifters to lift weights two or three times their own body weight? How does Donovan Bailey run a distance of 100 metres under 10 seconds? In fact, how are we able to stand upright and move against gravity and other forces? The science of anatomy attempts to shed light on these and other questions, as well as to provide answers based on the complex and intricate structure of the human body. Many systems make up the human body. Some of them are the respiratory, urogenital, cardiovascular, nervous, endocrine, digestive, and musculoskeletal. The cardiovascular and nervous systems are essential to the musculoskeletal system and are presented in Chapters 6 and 17, respectively. In this chapter we will deal with the musculoskeletal system. Figure 2.1 The human body is capable of moving gracefully and performing very challenging tasks. Studying Human Movement and Health Terms and Concepts Worth Knowing In order to describe anatomy with clarity, there is a certain language or terminology to be learned. The language of anatomy may be difficult to grasp at first because it is largely unfamiliar to you; but once you gain a general understanding of the word roots, suffixes, and prefixes commonly used in anatomy, the terminology will become increasingly meaningful. For example, if you know that myo refers to muscle and that cardio pertains to the heart, you can reach the conclusion that myocardium refers to the muscle of the heart. The knowledge of some basic terms and concepts is invaluable to improving your unde of anatomy. Anatomical Position Of particular importance to studying anatomy is the basic anatomica position. It is used in all anatomica description, specifying the locations of specific parts of the body relative to other body parts; it can best be learned by you, the student, in the following position: standing erect, facing forward, arms hanging at the sides with palms facing forward, legs straight, and heels and feet together and parallel to each other. The anatomical pos is universally accepted as the sta reference point for describing the h body (Figure 2.2). Directional Terms In the anatomical position, your medial to your eyes, your ears are to your cheeks, your skin lies supe your muscles, your heart is deep t ribcage, your lips are anterior (ve Front to Back The terms “ventral” and “dorsal” were used originally to describe positions in four-legged animals. In bipedal humans (two-legged animals such as ourselves) the terms “anterior” and “posterior” are used. However, the terminology “ventral” and “dorsal” may appear in some texts. to your teeth, your back is posterior (dorsal) to your abdomen, and your lips are superior to your chin. Also, the hands are distal to the arms, and the arms are proximal to the hands. The terms proximal and distal are also used to describe nerves and blood vessels, proximal meaning “toward the origin” and distal meaning “away from the person lying on his back is supine n lying face down is said to be in position (e.g., when preparing to rm a push-up). Each of the terms described here ndicates the location of a body part r position in relation to another art of the body, giving a clear ndication of where body parts may be found. If you want to locate the abdomen, for example, you would say, “The abdomen is inferior to the thorax,” rather than saying, “The abdomen is below the thorax.” It is important to note, however, that directional terms are based on the assumption that the body is in the anatomical on (Figure 2.2). es of the body dition to directional terms, there ain planes (imaginary flat surfaces) ed to be defined and understood, Figure 2.2 The anatomical position. Foundations of Exercise Science Directional Terms Superior – Nearer to the head The head is superior to the thorax. Deep – Farther from the surface of the body The heart lies deep to the ribs. Inferior – Nearer to the feet The stomach is inferior to the heart. Medial – Nearer to the median plane The nose is medial to the eyes. Anterior (Ventral) – Nearer to the front The quadriceps are anterior to the hamstrings. Lateral – Farther from the median plane The eyes are lateral to the nose. Posterior (Dorsal) – Nearer to the back The hamstrings are posterior to the quadriceps. Distal – Farther from the trunk The hands are distal to the arms. Superficial – Nearer to the surface of the body The skin is more superficial than muscle. Proximal – Nearer to the trunk The arms are proximal to the hands. which divide the body for further identification of particular areas. These terms always refer to the body in the anatomical position. For an individual standing in the anatomical position, the point at which the median, frontal, and transverse planes intersect represents the body’s centre of gravity (centre of mass). The median plane or midsagittal plane is a vertical plane that bisects the body into right and left halves; the sagittal plane is any plane parallel to the median plane; the frontal plane or coronal plane is any vertical plane at right angles to the median plane; and the transverse plane or horizontal plane is any plane at right angles to both the median and frontal planes (Figure 2.3). These planes can also be used to describe different movements or actions, being described as sagittal, frontal, or transverse plane movements when they occur in a plane that is parallel to one of these planes. For example, a forward roll would be considered a sagittal plane movement because the forward and backward motion is parallel to the sagittal plane. Other sagittal plane movements include cycling and running. Similarly, movements that are lateral, or side-to-side in nature, can be described as frontal plane movements; some good examples are cartwheels, jumping jacks, and side-stepping. Can you think of any activities that would be considered transverse plane movements? How about a twist performed by a diver, or a pirouette in ballet? Although many movements do not occur in any one plane, large movements and movements that occur at joints can often be described as being sagittal, frontal, or transverse plane movements; therefore, these reference planes still remain useful for describing human movement. Joint Movements Most movements are often found in pairs: for every movement, there is generally a movement that is opposite to it. There are exceptions, but the following descriptions apply to most joints and are illustrated in Figure 2.4. Flexion–Extension This usually occurs in a sagittal plane. In general, flexion reduces the angle between two bones at a joint and extension increases it. Consider the elbow joint when a biceps curl is performed. Lifting the weight requires flexion (reducing the angle at the joint), while lowering the weight involves extension (increasing the angle at the joint). These terms are modified in certain actions, for example, at the ankle joint, where the terms dorsiflexion (motion bringing the top of the foot toward the lower leg or shin) and plantar flexion (“planting” the foot) are used. Studying Human Movement and Health Frontal (Coronal) Plane Proximal Superior Inferior Distal Transverse (Horizontal) Plane al Later Later al l Media l Media Po s ter ior An ter ior Midsagittal Plane Figure 2.3 Anatomical position, directional terms, and planes of the body. Foundations of Exercise Science Flexion Extension Abduction Adduction Circumduction Rotation Pronation Supination Inversion Eversion Dorsiflexion Plantar Flexion Figure 2.4 Major body movements around joints. Studying Human Movement and Health Abduction–Adduction In general, abduction is movement away from the midline of the body and adduction is movement toward the midline of the body in the frontal plane. The motions of the arms and legs during a jumping jack are examples of these two types of movements. Circumduction When flexion–extension movements are combined with abduction–adduction movements, a cone of movement occurs, but does not include any rotation. Tracing an imaginary circle in the air with your index finger while the rest of the hand remains stationary produces circumduction. The tip of your finger represents the base of the cone, while your knuckle forms the apex of this conical motion. This movement can occur at other moving body segments such as the hip and shoulder. Rotation A bone may also rotate along its longitudinal axis. To illustrate this action, flex your right elbow, place your left hand on your right shoulder and now rotate your right arm so that your hand is carried towards your abdomen. This movement toward the median plane is called medial or internal rotation. When you rotate your arm back to the original position or out laterally, this is called lateral or external rotation. Pronation–Supination This movement is used to describe movements relative to the forearm and hand. When the palm is moved to face anteriorly, this is supination (you can hold a bowl of soup); when the palm is moved to face posteriorly, it is pronation. These actions are required when turning a door knob, opening a jar, or performing a topspin shot in tennis. Inversion–Eversion This movement is relative to the sole of the foot. When the sole is turned inward (as when you “go over” on your ankle) it is inverted: this movement is called inversion. Injuries are common at the ankle joint, occurring when the joint is severely inverted beyond its normal range of motion. When the sole is turned outward or away from the median plane of the body, it is everted: this movement is called eversion. Dorsiflexion–Plantar Flexion The movement of the ankle so that the dorsal surface of the foot moves superiorly is called dorsiflexion. It is the opposite of plantar flexion that draws the foot inferiorly in the anatomical position. These actions occur when standing on the toes or using the pedals of a car while driving. The Musculoskeletal System The musculoskeletal system is composed of thr compo and th its own the in that a occur. framew can be produc muscle pull aga the bon that c diverse in all These compo togethe the hu strong, and cap moving grace. Foundations of Exercise Science Bones of the Human Body The bones of the human body provide the supporting framework and protection for the vital organs of the body – living tissue complete with blood supply and nerves. Remember how painful it is to hit your shin on something firm and sharp? Bone Shape Bone can be classified by shape as short (e.g., bones of the wrist and ankle) that serve as good shock absorbers, long (like the femur of the thigh and the humerus of the upper arm) with proximal and distal enlargements, flat (like the bones of the skull and scapula) that largely protect underlying organs and provide areas for muscle attachment, irregular (like the bones of your face and vertebrae) that fulfil special functions, and sesamoid (shaped like a pea and found in tendons). The structures and shapes of the bones of the human body allow them to perform specific functions more effectively (Table 2.1). Bone Classification The amount of mineral content in bone varies with one’s age, but also with the specific bone in the body. Bones that are more porous have a smaller proportion of calcium phosphate and carbonate, and greater non-mineralized tissue. According to the degree of porosity, bone can be classified into two general categories. Bone that has low porosity is called cortical bone (Figure 2.5). It is less flexible and can resist greater stress. In contrast, spongy or cancellous bone has a relatively high porosity with more non-mineralized tissue. Spongy bone Table 2.1 Bone classifications. Shape Examples Long Short Flat Sesamoid Irregular Pelvis Skeleton Studying Human Movement and Health has a characteristic honeycomb structure, and provides more flexibility. Cortical bone is largely found in long bones (such as the bones of the arms and legs) that are required to be stronger to resist greater stress, while spongy bone is found where shock absorption and a better ability to change shape are important (e.g., vertebrae). Typically, long bones have a marrow cavity filled with red marrow in children and yellow marrow in adults. Bone Composition Bone is very strong for its relatively light weight. What gives bone this important characteristic? The major components of bone are calcium carbonate, calcium phosphate, collagen, and water. The two calcium compounds make up approximately 60-70 percent of bone weight, providing much of the bone’s stiffness and resistance to pressing or squeezing forces. The collagen component (a protein) gives bone its characteristic flexibility, and contributes to its ability to resist pulling and stretching forces. The bones of children are significantly more pliable than those of adults. With aging, collagen is lost progressively and bone becomes more brittle. Although the human body as a whole is composed of about 60 percent water, bone only contains approximately 20 percent water (20-25 percent of total bone weight). Consequently, bones are stronger and more durable than many other structures, such as skin. Effect of Fitness on Bone Similar to muscles, bone also responds to the presence or absence of different forces with changes in size, shape, and density. When bones are subjected to regular physical activity and habitual loads, bones tend to become denser and more mineralized than the bones in people who are less active. This is revealed by the right-handed tennis player whose right forearm bones are denser than the left, as a result of using them more frequently. Similar changes can be found in throwers and runners in other sports. But just as forces acting on bone can increase bone density, inactivity works in the opposite direction, leading to a decrease in weight and strength. Loss of bone mass as a result of reduced mechanical stress has been noted in bed-ridden patients, inactive senior citizens, and astronauts. The Human Skeleton Figure 2.5 Transverse sections of the humerus, a long bone of the upper limb. Approximately 206 bones make up the human skeleton. The skeleton (Figures 2.6 and 2.7) may be divided into axial and appendicular sections. The axial skeleton is composed of the skull, vertebrae, ribs, and sternum (the head, spine, and trunk), numbering 80 bones. The appendicular skeleton is made up of the pectoral (shoulder) and pelvic (hip) girdles, and the upper (arms) and lower (legs) limbs that are appended (hung) from the girdles. The appendicular portion of the skeleton consists of about 126 bones. While the axial skeleton serves mainly to support, stabilize, and protect vital organs of the body, the