Musculoskeletal System - Structure, Function, and Exercises - PDF

Chapter 24: Musculo-Skeletal System Written by Carolyn Jarvis, PhD, APN, CNP Adapted by Marian Luctkar-Flude, RN, PhD Structure and Function The musculo-skeletal system consists of the body’s bones, joints, and muscles. Humans need this system for support to stand erect and for movement. The musculo...

Chapter 24: Musculo-Skeletal System Written by Carolyn Jarvis, PhD, APN, CNP Adapted by Marian Luctkar-Flude, RN, PhD Structure and Function The musculo-skeletal system consists of the body’s bones, joints, and muscles. Humans need this system for support to stand erect and for movement. The musculo-skeletal system also functions to encase and protect the inner vital organs (e.g., brain, spinal cord, heart), to produce the red blood cells in the bone marrow (hematopoiesis), and as a reservoir for storage of essential minerals such as calcium and phosphorus in the bones. Components of The Musculo-Skeletal System The skeleton has 206 bones that provide the framework of the body (Fig. 24.1). Bone and cartilage are specialized forms of connective tissue. Bone is hard, rigid, and very dense. Its cells are continually turning over and remodelling. The joint (or articulation) is the place of union of two or more bones. Joints are the functional units of the musculo-skeletal system because they enable the mobility needed for activities of daily living (ADLs). Nonsynovial or Synovial Joints In nonsynovial joints, the bones are united by fibrous tissue or cartilage and are immovable (e.g., the sutures in the skull) or only slightly movable (e.g., the vertebrae). Synovial joints are freely movable because the bones are separated from each other and enclosed in a joint cavity (Fig. 24.2). This cavity is filled with a lubricant: synovial fluid that allows sliding of opposing surfaces, which enables movement. In synovial joints, a layer of resilient cartilage covers the surface of opposing bones. Cartilage is avascular, receiving nourishment from synovial fluid that circulates during joint movement. It is a very stable connective tissue with a slow cell turnover. It has a tough, firm consistency, yet is flexible. Cartilage cushions the bones and provides a smooth surface to facilitate movement. Each joint is surrounded by a fibrous capsule and is supported by ligaments. Ligaments are fibrous bands running directly from one bone to another that strengthen the joint and help prevent movement in undesirable directions. A bursa is an enclosed sac filled with viscous synovial fluid, much like a joint. Bursae are located in areas of potential friction (e.g., subacromial bursa of the shoulder, prepatellar bursa of the knee) and help muscles and tendons glide smoothly over bone. Muscles Muscles account for 40 to 50% of the body’s weight. When they contract, they produce movement. Muscles are of three types: (a) skeletal, (b) smooth, and (c) cardiac. This chapter is concerned with skeletal, or voluntary, muscles, which are under conscious control (Fig. 24.3). Each skeletal muscle is composed of bundles of muscle fibres (fasciculi). Skeletal muscle is attached to bone by a tendon, a strong fibrous cord. Skeletal muscles produce the following movements (Fig. 24.4): 1. Flexion: bending a limb at a joint 2. Extension: straightening a limb at a joint 3. Abduction: moving a limb away from the midline of the body 4. Adduction: moving a limb toward the midline of the body 5. Pronation: turning the forearm so that the palm is down 6. Supination: turning the forearm so that the palm is up 7. Circumduction: moving the arm in a circle around the shoulder 8. Inversion: moving the sole of the foot inward at the ankle 9. Eversion: moving the sole of the foot outward at the ankle 10. Rotation: moving the head around a central axis 11. Protraction: moving a body part forward and parallel to the ground 12. Retraction: moving a body part backward and parallel to the ground 13. Elevation: raising a body part 14. Depression: lowering a body part Temporomandibular Joint The temporomandibular joint is the articulation of the mandible and the temporal bone (Fig. 24.5). You can feel it in the depression anterior to the tragus of the ear. The temporomandibular joint enables jaw function for speaking and chewing. The joint allows three motions: (a) hinge action to open and close the jaws, (b) gliding action for protrusion and retraction, and (c) gliding action for side-to-side movement of the lower jaw. 24.1 Components of the musculo-skeletal system. The front view and the rear view of a human skeleton system for the components of the Musculo-skeletal system. A) The Musculo-skeletal system is divided into axial skeleton and appendicular skeleton. Axial skeleton: Frontal bone, nasal bone, Zygomatic bone, maxilla, mandible, manubrium, sternum, xiphoid process, ribs, costal cartilage, and vertebral column. Appendicular skeleton: Clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, phalanges, Ilium, pubis, Ischium, greater trochanter, femur, patella, tibia, fibula, tarsals, Metatarsals, and phalanges. B) Axial skeleton: Parietal bone, occipital bone, cervical vertebrae 7 numbers, thoracic vertebrae 12 numbers, lumbar vertebrae 5 numbers, rib, sacrum, and coccyx. Appendicular skeleton: Clavicle, Acromion process, scapula, humerus, radius, ulna, carpals, Metacarpals, phalanges, Coxa of the hip bone which comprises of Ilium, pubis, and ischium, femur, tibia, fibula, phalanges, Metatarsal bones, tarsals, Calcaneus or a tarsal bone. 24.2 Synovial joints. An illustration of the foot of a human highlights the various synovial joints. The synovial joints include tibia, cartilage, synovial membrane, synovial cavity, capsular ligament. The following other parts are also marked. Tendo calcaneus or Achilles tendon, talus, bursae, flexor muscles, extensor tendon, and flexor tendon. 24.3 Skeletal muscles of the body. The front and the rear views of a human skeleton highlights the various skeletal muscles of the body. A) The skeletal muscles marked are as follows. Sternocleidomastoid, trapezius, pectoralis major, deltoid, biceps brachii, rectus abdominis, Brachioradialis, flexor carpi radialis, Iliopsoas, pectineus, Serratus anterior, internal oblique, external oblique, Transversus abdominis, Tensor of fasciae latae, Sartorius, adductor magnus, Iliotibial tract, Gracilis, Rectus femoris, Vastus lateralis, Tendon of rectus femoris, patella, patellar ligament, Peroneus longus, Tibialis anterior, Gastrocnemius, soleus, and extensor digitorum longus. B) The rear view highlights the following skeletal muscles. Splenius capitis, Levator scapulae, Supraspinatus, Rhomboideus major, Sternocleidomastoid, trapezius, Rhomboideus minor, deltoid, Latissimus dorsi, Infraspinatus, teres minor, teres major, Serratus anterior, External oblique, Anconeus, triceps long and short head, Brachioradialis, Extensor carpi radialis longus, Extensor digitorum communis, Gluteus medius, Gluteus maximus, Flexor carpi ulnaris, Extensor carpi ulnaris, Abductor pollicis longus, Extensor pollicis brevis, Adductor magnus, Iliotibial tract, Gracilis, Semitendinosus, Semimembranosus, Biceps femoris of long head, Semimembranosus, Gastrocnemius, soleus, Biceps femoris of short head, Peroneus longus, and Peroneus brevis. Spine The vertebrae are 33 connecting bones stacked in a vertical column (Fig. 24.6). You can feel their spinous processes in a furrow down the midline of the back. The furrow has paravertebral muscles mounded on either side down to the sacrum, where it flattens. Humans have 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 3 to 4 coccygeal vertebrae. The following surface landmarks will orient you to their levels: The spinous processes of C7 and T1 are prominent at the base of the neck. The inferior angle of the scapula normally is at the level of the interspace between T7 and T8. An imaginary line connecting the highest point on each iliac crest crosses L4. An imaginary line joining the two symmetrical dimples that overlie the posterior superior iliac spines crosses the sacrum. A lateral view (Fig. 24.7) shows that the vertebral column has four curves (a double S-shape). The cervical and lumbar curves are concave (inward or anterior), and the thoracic and sacrococcygeal curves are convex. The balanced or compensatory nature of these curves, together with the resilient intervertebral discs, allows the spine to absorb a great deal of shock. The intervertebral discs are elastic fibrocartilaginous plates that constitute one-fourth of the length of the column (Fig. 24.8). Each disc centre has a nucleus pulposus, made of soft, semifluid, mucoid material that has the consistency of toothpaste in young adults. The discs cushion the spine like a shock absorber and help it move. As the spine moves, the elasticity of the discs allows compression on one side, with compensatory expansion on the other. If compression is too great, a disc can rupture, and the nucleus pulposus can herniate out of the vertebral column, compressing the spinal nerves and causing pain. The unique structure of the spine enables both upright posture and flexibility for motion. The motions of the vertebral column are flexion (bending forward), extension (bending back), abduction (to either side), and rotation. Shoulder The glenohumeral joint is the articulation of the humerus with the glenoid fossa of the scapula (Fig. 24.9). Its ball-and-socket action allows great mobility of the arm in many axes. The joint is enclosed by a group of four powerful muscles and tendons that support and stabilize it. Together, these muscles and tendons are called the rotator cuff of the shoulder. The large subacromial bursa helps during abduction of the arm so that the greater tubercle of the humerus moves easily under the acromion process of the scapula. 24.4 © Pat Thomas, 2006. An illustration highlights the various skeletal muscle movements. 1) Flexion of an arm; 2) Extension of an arm; 3) Abduction of an arm or outward movement; 4) Adduction of an arm or inward movement; 5) Pronation or the palm faces down; 6) Supination or the palm faces up; 7) Circumduction: A shoulder movement such that the hand traces a circle; 8) Rotation: Rotation of the head on either sides; 9) Eversion or movement of the foot away from the median plane; 10) Inversion or movement of the foot towards the median plane; 11) Protraction or movement of the head in a forward direction; 12) Retraction or movement of the head in backward direction; 13) Elevation or raising the shouldered; and 14) Depression or lowering the shoulder. 24.5 An illustration of a jawbone highlights the temporomandibular joint. This connects the jaw bone to the skull. The other parts marked are Zygomatic arch of temporal bone, external auditory meatus, condyle of mandible, and joint capsule. The sagittal section highlights the following parts. Zygomatic arch, upper joint cavity, articular disc, Pterygoid muscle, lower joint cavity, joint capsule, and synovial membrane. 24.6 An illustration of the spinal vertebral column highlights the landmarks of the spine. The scapula is a flat and triangle-shaped bone located in the upper thoracic region of the rib cage. The T 1 - C 7 spinal segment connects the neck with the upper back. The T 7 vertebra is located in the middle of the thoracic spinal column. T 8 is located below the T 7 vertebra. The T 12 vertebra is the twelfth thoracic vertebra and located at the bottom of the spine. The L 1 is located below the T 12 vertebra. L 4 and L 5 are the two lowest vertebrae in the lumbar spine. S 2 is located at the level of the posterior superior iliac spine. The coccyx or the tail bone is a small triangle-shaped bone located at the bottom of the spine. 24.7 The bones of the shoulder have palpable landmarks to guide examination (Fig. 24.10). The scapula and clavicle connect to form the shoulder girdle. You can feel the bump of the scapula’s acromion process at the very top of the shoulder. Move your fingers in a small circle outward, down, and around. The next bump is the greater tubercle of the humerus a few centimetres down and laterally, and from that the coracoid process of the scapula is a few centimetres medially. These surround the deeply situated joint. Elbow The elbow joint contains three bony articulations of the (a) humerus, (b) radius, and (c) ulna of the forearm (Fig. 24.11). Its hinge action moves the forearm (radius and ulna) on one plane, allowing flexion and extension. The olecranon bursa lies between the olecranon process and the skin. Palpable landmarks are the medial and lateral epicondyles of the humerus and the large olecranon process of the ulna in between them. The sensitive ulnar nerve runs between the olecranon process and the medial epicondyle. The radius and ulna articulate with each other at two radioulnar joints, one at the elbow and one at the wrist. These move together, enabling pronation and supination of the hand and forearm. Wrist and Carpal Joints Of the body’s 206 bones, more than half are in the hands and feet. The wrist, or radiocarpal joint, is the articulation of the radius (on the thumb side) and a row of carpal bones (Fig. 24.12). Its condyloid action enables movement in two planes at right angles: (a) flexion and extension and (b) side-to-side deviation. You can feel the groove of this joint on the dorsum of the wrist. The midcarpal joint is the articulation between two parallel rows of carpal bones. It allows flexion, extension, and some rotation. The metacarpophalangeal and the interphalangeal joints enable finger flexion and extension. The flexor tendons of the wrist and hand are enclosed in synovial sheaths. Hip The hip joint is the articulation between the acetabulum and the head of the femur (Fig. 24.13). As in the shoulder, ball-and-socket action enables a wide range of motion (ROM) on many axes. The hip has somewhat less ROM than the shoulder, but it has more stability, which befits its weight-bearing function. Hip stability is enabled by powerful muscles that spread over the joint, a strong fibrous articular capsule, and the very deep insertion of the head of the femur. Three bursae facilitate movement. 24.8 The vertebrae. Three separate illustrations highlights the intervertebral discs. Intervertebral discs are a layer of cartilage separating adjacent vertebrae in the spine. A cross-sectional view highlights the following parts. Intervertebral foramen or the exit of spinal nerves; Ligaments; Spinous process; Intervertebral disc; nucleus pulposus; and body of vertebra. A superior view highlights the following parts. Spinous process; body of lumbar vertebra; and vertebral foramen or the channel of spinal cord. A lateral view highlights the following parts. Articular process, spinous process, costal facet; and intervertebral disc between T 11, T 12, and L 1 discs. 24.9 Two separate illustrations. A cross-sectional view of a shoulder joint highlights the internal shoulder parts. Clavicle, acromion of scapula, subacromial bursa, and greater tubercle of humerus. Another illustration shows the superior view of a shoulder with arm elevated. The supraspinatus muscle, deltoid muscle, and subacromial bursa are highlighted. 24.10 A cross-section for the anterior view of the bony landmarks of the shoulder. Clavicle, supraspinatus muscle, coracoid process of scapula, glenohumeral joint, joint capsule, acromion of scapula, subacromial bursa, greater tubercle of humerus, and biceps brachii muscle. 24.11 A cross-section for the posterior view of the right elbow. The following parts are marked. Right humerus, synovial membrane, lateral epicondyle, annular ligament, radius, ulna, olecranon bursa, olecranon process, medial epicondyle, and ulnar nerve. Palpation of bony landmarks will guide your examination: you can feel the entire iliac crest, from the anterior superior iliac spine to the posterior superior iliac spine. The ischial tuberosity lies under the gluteus maximus muscle and is palpable when the hip is flexed. The greater trochanter of the femur is normally the width of the person’s palm below the iliac crest and halfway between the anterior superior iliac spine and the ischial tuberosity. You can palpate it, when the person is standing, in a flat depression on the upper lateral side of the thigh. Knee The knee joint is the articulation of three bones—(a) the femur, (b) the tibia, and (c) the patella (kneecap)—in one common articular cavity (Fig. 24.14). It is the largest joint in the body and is complex. It is a hinge joint, enabling flexion and extension of the lower leg on a single plane. The knee’s synovial membrane is the largest in the body. At the superior border of the patella, it forms a sac, the suprapatellar pouch, that extends up as much as 6 cm behind the quadriceps muscle. Two wedge-shaped cartilages, the medial and lateral menisci, cushion the tibia and femur. The joint is stabilized by two sets of ligaments. The cruciate ligaments (not shown in Fig. 24.14) criss-cross within the knee, providing anterior and posterior stability and helping control rotation. The collateral ligaments connect the joint at both sides, providing medial and lateral stability and preventing dislocation. Numerous bursae prevent friction. One, the prepatellar bursa, lies between the patella and the skin. The infrapatellar fat pad is a small, triangular fat pad below the patella and behind the patellar ligament. Landmarks of the knee joint start with the large quadriceps muscle, which you can feel on your anterior and lateral thigh (Fig. 24.15). The muscle’s four heads merge into a common tendon that continues down to enclose the round bony patella. Then the tendon inserts down on the tibial tuberosity, which you can palpate as a bony prominence in the midline. Move to the sides and a bit superiorly, and note the lateral and medial condyles of the tibia. Superior to these on either side of the patella are the medial and lateral epicondyles of the femur. 24.12 A cross-section of the palmar view of the hand highlights the various bones of the hand. They are radius, ulna, synovial membrane of the radiocarpal joint, synovial membranes between the carpal bones, metacarpophalangeal joint, and Interphalangeal joint. An inset image shows the joint detail which has the articular cartilage, fibrous capsule, and synovial membrane. 24.13 Two cross-sectional views for the hip joint. Left: The following parts are highlighted. Articular capsule, Iliopectineal bursa, pubis, obturator foramen, ischial tuberosity, anterior superior iliac spine, and greater trochanter of femur. Right: The following parts are highlighted. Acetabulum and the head of femur are highlighted. Ankle and Foot The ankle, or tibiotalar joint, is the articulation of the tibia, fibula, and talus (Fig. 24.16). It is a hinge joint, limited to flexion (dorsiflexion) and extension (plantar flexion) in one plane. Landmarks are two bony prominences on either side: (a) the medial malleolus and (b) the lateral malleolus. Strong, tight medial and lateral ligaments extend from each malleolus onto the foot. They promote lateral stability of the ankle joint, although they may be torn in eversion or inversion sprains of the ankle. Joints distal to the ankle provide additional mobility in the foot. The subtalar joint enables inversion and eversion of the foot. The foot has a longitudinal arch, so that weight bearing is distributed between the parts that touch the ground: the heads of the metatarsals and the calcaneus (heel). 24.14 The medial and the sagittal section of the left knee. Medial view: The following parts are marked. Suprapatellar bursa, prepatellar bursa, patella, infrapatellar fat pad, patellar ligament, tibia, gastrocnemius muscle, medial sulcus, medial collateral ligament, and femur. Sagittal section: Femur, suprapatellar bursa, prepatellar bursa, patella, infrapatellar fat pad, subcutaneous infrapatellar bursa, deep infrapatellar bursa, tibia, meniscus, and joint capsule. 24.15 A cross-sectional view of the right knee highlights the landmarks of the right knee joint. The following parts are highlighted. Quadriceps muscle, patella, patellar ligament, medial condyle of tibia, anterior cruciate ligament (the joint is kept open), tibial tuberosity, fibula, lateral condyle of tibia, lateral meniscus, lateral collateral ligament, and lateral epicondyle of femur. Developmental Considerations Infants and Children By 3 months’ gestation, a “scale model” of the skeleton that is made up of cartilage has formed. During succeeding months in utero, the cartilage ossifies into true bone and starts to grow. Bone growth continues after birth—rapidly during infancy and then steadily during childhood—and during adolescence. Long bones grow in two dimensions. They increase in width or diameter by deposition of new bony tissue around the shafts. Lengthening occurs at the epiphyses (growth plates). These specialized growth centres are transverse discs located at the ends of long bones. Trauma or infection at this location puts the growing child at risk for bone deformity. Longitudinal growth continues until closure of the epiphyses; the last closure occurs at about age 20 years. Skeletal contour changes are apparent at the vertebral column. At birth the spine has a single C-shaped curve. At 3 to 4 months, when the baby can raise the head from the prone position, the anterior curve in the cervical neck region develops. From ages 1 year to 18 months, standing erect causes the development of the anterior curve in the lumbar region. Although the skeleton contributes to linear growth, muscles and fat are significant for weight increase. Individual muscle fibres grow through childhood, but growth is marked during the adolescent growth spurt. At this time, muscles respond to increased secretion of growth hormone, to adrenal androgens, and, in boys, to further stimulation by testosterone. Muscles vary in size and strength in different people. This variation is attributable to genetic programming, nutrition, and exercise. All through life, muscles increase with use and atrophy with disuse. Obesity and osteoporosis have their beginnings in childhood. Children and teenagers with overweight or obesity are more likely to become obese as adults and it is more challenging for these adults to lose their excess weight.1 The following factors help prevent obesity and promote peak bone mass accrual: regular exercise, a diet rich in dark green and deep yellow vegetables and dairy products, and a diet low in fried foods and carbonated beverages.2 Routine growth monitoring is recommended for all children and youth to identify those who are not following a healthy body mass index (BMI) trajectory according to the World Health Organization (WHO) Growth Charts for Canada.3 24.16 A cross-sectional view highlights the following parts of the ankle joint. Tibia, medial malleolus, deltoid ligament, talus, talocalcaneal interosseous ligament, calcaneus, flexor muscle, abductor muscle, subtalar joint, calcaneofibular ligament, lateral malleolus, tibiotalar joint, and fibula. A dorsal view highlights following parts in the top of the foot. They are subtalar joint, talonavicular joint, navicular bone, cuneiform bones, tarsometatarsal joint, distal phalanx, middle phalanx, proximal phalanx, metatarsal, cuboid bone, talus, and calcaneus. The term developmental dysplasia of the hip (DDH) refers to a number of congenital abnormalities of the hip joint, including dislocated hip and subluxation of the hip. Newborns should have a clinical hip examination at birth and regular hip checks should be performed as part of regular well-baby exams. Selective ultrasound screening may be considered in infants before 6 months of age with at least one of the following risk factors: breech presentation, family history, or history of clinical instability.4 Girls are more predisposed than boys to DDH, and Indigenous people in Canada have a high risk for DDH. The most common cause of childhood musculo-skeletal pain is termed “growing pains,” a noninflammatory pain syndrome affecting children mainly between the ages of 3 and 12 years. The pain is usually nonarticular, bilateral, and located in the lower extremities; it occurs late in the day or is nocturnal, often awakening the child, and frequently occurs on days of increased physical activity. The pain can be mild or very severe, lasting minutes to hours; is generally episodic but may occur daily; and usually resolves by late childhood. Other causes should be considered when a child is younger than 3 years of age, is limping, or interrupts play or exercise due to the pain. Pregnant Women Increased levels of circulating hormones (estrogen, relaxin from the corpus luteum, and corticosteroids) cause increased mobility in the joints. Increased mobility in the sacroiliac, sacrococcygeal, and symphysis pubis joints in the pelvis contributes to the noticeable changes in maternal posture. The most characteristic change is progressive lordosis, which compensates for the enlarging fetus; otherwise, the centre of balance would shift forward. Lordosis compensates by shifting the weight farther back on the lower extremities. This shift in balance, in turn, creates strain on the low back muscles, which in some women is felt as low back pain during late pregnancy. Anterior flexion of the neck and slumping of the shoulder girdle are other postural changes that compensate for the lordosis. These upper back changes may put pressure on the ulnar and median nerves during the third trimester. Nerve pressure creates aching, numbness, and weakness in the upper extremities in some women. Older Adults Bone remodelling is a cyclical process of loss of bone matrix (bone resorption) and new bone growth (deposition). Up to 90% of peak bone mass is deposited by age 18 years in girls and age 20 years in boys; thus, maximizing bone mineral density early in life reduces effects of bone loss during aging.3 After age 40, resorption occurs more rapidly than deposition. The net effect is a loss of bone density (osteoporosis). Although some degree of osteoporosis is nearly universal, women are more affected than men because lack of estrogen after menopause causes bone loss to accelerate. Risk factors for fracture associated with osteoporosis are listed in Table 24.1. Postural changes are evident with aging, and decreased height is the most noticeable. Long bones do not shorten with age; decrease in height results from shortening of the vertebral column caused by loss of water content and thinning of the intervertebral discs, which occurs more in middle age. Both men and women can expect a progressive decrease in height beginning in the 40s, although this is not significant until age 60 years. A greater decrease occurs in the 70s and 80s because of osteoporotic collapse of the vertebrae, which results in shortening of the trunk and the appearance of comparatively long extremities. Other postural changes are kyphosis, a backward head tilt to compensate for the kyphosis, and a slight flexion of hips and knees. The distribution of subcutaneous fat changes through life. Usually, men and women gain weight in their 40s and 50s. The body contour is different, even if the weight is the same as when they were younger. They begin to lose fat in the face and deposit it in the abdomen and hips. In the 80s and 90s, fat further decreases in the periphery, noticeably in the forearms and over the abdomen and hips. TABLE 24.1 Indications for Measuring Bone Mineral Density to Assess for Osteoporosis OLDER ADULTS (AGE ≥50 YEARS)​YOUNGER ADULTS (AGE