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Surface and Regional © The McGraw−Hill Anatomy buy cheap betapace 40 mg on line blood pressure tracking chart, Sixth Edition Anatomy Companies cheap 40mg betapace blood pressure in elderly, 2001 338 Unit 4 Support and Movement Trauma to the Shoulder and Upper Extremity langes. Splinting the finger for a period of time may be curative; however, surgery may be required to avoid a permanent crook in The wide variety of injuries to the shoulder and upper extremity the finger. Diseases of the Shoulder and Upper Extremity It is not uncommon to traumatize the shoulder and upper Inflammations in specific locations of the shoulder or upper ex- extremity of a newborn during a difficult delivery. Upper arm tremity are the only common clinical conditions endemic to birth palsy (Erb–Duchenne palsy) is the most common type of these regions. Bursitis, for example, may specifically afflict any birthing injury, caused by a forcible widening of the angle be- of the numerous bursae of the shoulder, elbow, or wrist joints. Using forceps to rotate the fetus in There are several types of arthritis, but generally they involve utero, or pulling on the head during delivery, may cause this in- synovial joints throughout the body rather than just those in the jury. The site of injury is at the junction of vertebrae C5 and C6 hands and fingers. Carpal tunnel syndrome is caused by compression of the The expression of the injury is paralysis of the abductors and lat- median nerve by the carpal flexor retinaculum that forms the eral rotators of the shoulder and the flexors of the elbow. The nerve compression re- arm will permanently hang at the side in medial rotation. The compression is due to an support of the clavicle and acromion of the scapula superiorly inflammation of the transverse carpal ligament, which may be and the tendons forming the rotator cuff anteriorly. Injuries of this sort are the synovial tendon sheath in the wrist or hand. Sudden jerks of infections are quite common following a puncture wound in the arm are also likely to dislocate the shoulder, especially in which pathogens enter the closed synovial sheath. Many fractures result from extending the arm to of hand function can be prevented by draining the synovial break a fall. The clavicle is the most frequently broken bone in sheath and providing antibiotic treatment. Also common are fractures of the humerus, which are often serious because of injury to the nerves and vessels that par- allel the bone. The surgical neck of the humerus is a common Hip and Lower Extremity fracture site. At this point, the axillary nerve is often damaged, thus limiting abduction of the arm. A fracture in the middle Developmental Conditions third of the humerus may damage the radial nerve, causing paral- The embryonic development of the hip and lower extremity fol- ysis of the extensor muscles of the hand (wristdrop). A fracture lows the developmental pattern of the shoulder and upper ex- of the olecranon of the ulna often damages the ulnar nerve, re- tremity: the appearance of the limb bud is followed by the sulting in paralysis of the flexor muscles of the hand and the ad- formation of the mesenchymal primordium of bone and muscle in ductor muscles of the thumb. Development of the lower extremity, frequently fractured (Colles’ fracture) by falling on an out- however,lags behind that of the upper extremity by 3 or 4 days. In this fracture, the hand is displaced backward The likelihood of congenital deformities of the hips and and upward. The few congenital malformations that during the backhand stroke in tennis, may cause lateral epi- occur generally have a genetic basis. Wearing In congenital dislocation of the hip, the acetabulum fails an elbow brace or a compression band may help reduce the to develop adequately,and the head of the femur slides out of the pain, but only if the cause is eliminated will the area be al- acetabulum onto the gluteal surface of the ilium. Athletes frequently jam a finger when a ball forcefully Polydactyly and syndactyly occur in the feet as well as in the strikes a distal phalanx as the fingers are extended, causing a hands. Erb, German neurologist, 1840–1921, tain whether abnormal positioning or restricted movement in and Guillaume G. Duchenne, French neurologist, 1806–75 utero causes talipes, but both genetic and environmental factors Colles’ fracture: from Abraham Colles, Irish surgeon, 1773–1843 are involved in most cases. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 Chapter 10 Surface and Regional Anatomy 339 Trauma to the Hip and Lower Extremity not show up on radiographs. Frequently, the only way to heal stress fractures is to abstain from exercise. As with the shoulder and upper extremity, a variety of traumatic Sprains are common in the joints of the lower extremity. These range from injury to the bones and surrounding muscles, Sprains are usually accompanied by synovitis, an inflammation of tendons, vessels, and nerves to damage of the joints in the form the joint capsule. Dislocation of the hip is a common and severe result of an automobile accident when a seat belt is not worn. When the hip Diseases of the Hip and Lower Extremity is in the flexed position, as in sitting in a seat, a sudden force ap- As in the shoulder and upper extremity, infections in the hip and plied at the distal end of the femur will drive the head of the lower extremity–such as bursitis and tendinitis–can be localized femur out of the acetabular socket, fracturing the posterior ac- in any part of the hip or lower extremity.

Excessive contraction of a muscle can also ATP within the fibers causes stiffness of the joints discount betapace 40 mg on line hypertension gout. This is similar damage the fibers or associated connective tissue discount betapace 40mg visa pulse pressure gap, resulting in a to physiological contracture, in which muscles become incapable of strained muscle. A cramp within a muscle is an involuntary, painful, pro- When skeletal muscles are not contracted, either because longed contraction. Cramps can occur while muscles are in use the motor nerve supply is blocked or because the limb is immobi- or at rest. They may result from general dehydration, deficiencies of is resumed, as after a healed fracture, but tissue death is in- calcium or oxygen, or from excessive stimulation of the motor evitable if the nerves cannot be stimulated. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 287 FIGURE 9. The fibers in healthy muscle tissue increase in size, or hy- column, where there are extensive aponeuroses. There are sev- myofibrils, accompanied by a strengthening of the associated eral kinds of muscular dystrophy, none of whose etiology is com- connective tissue. The most frequent type affects children and is sex-linked to the male child. As muscular dystrophy progresses, the muscle fibers atrophy and are replaced by adipose tissue. Most Diseases of Muscles children who have muscular dystrophy die before the age of 20. Pain and tenderness frequently occur in the extensor muscles of the lumbar region of the spinal lumbago: L. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 288 Unit 4 Support and Movement FIGURE 9. It can arise in any skeletal muscle, and toimmune disease, and it typically affects women between the most often afflicts young children and elderly people. Poliomyelitis (polio) is actually a viral disease of the ner- vous system that causes muscle paralysis. The viruses are usually Aging of Muscles localized in the anterior (ventral) horn of the spinal cord, where Although elderly people experience a general decrease in the they affect the motor nerve impulses to skeletal muscles. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 289 FIGURE 9. Loss of strength is a major contributor to falls and which a person may actively slow degenerative changes. It often results in dependence on others to perform decrease in muscle mass is partly due to changes in connective even the routine tasks of daily living. Atrophy of the muscles of the appendages causes the arms and legs to appear thin and bony. Degenerative changes in the nervous system decrease the effectiveness of motor activity. Muscles are slower to respond to stimulation, Clinical Case Study Answer causing a marked reduction in physical capabilities. The dimin- When cancer of the head or neck involves lymph nodes in the neck, a ished strength of the respiratory muscles may limit the ability of number of structures on the affected side are removed surgically. This muscle, Exercise is important at all stages of life but is especially which originates on the sternum and clavicle, inserts on the mastoid beneficial as one approaches old age (fig. When it contracts, the mastoid process, strengthens bones and muscles, but it also contributes to a which is located posteriorly at the base of the skull, is pulled forward, healthy circulatory system and thus ensures an adequate blood causing the chin to rotate away from the contracting muscle. This ex- plains why the patient who had his left sternocleidomastoid muscle re- supply to all body tissues. If an older person does not maintain moved would have difficulty turning his head to the right. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 290 Unit 4 Support and Movement (a) (b) (c) (d) FIGURE 9. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 291 FIGURE 9.

In addition to the proteins di- often called the “tail” region generic betapace 40 mg overnight delivery hypertension while pregnant, composed of light meromyosin rectly involved in the process of contraction generic 40 mg betapace with amex blood pressure medication ptsd, there are sev- (LMM). The remainder of the molecule, heavy meromyosin eral other important structural proteins. Titin, a large fila- (HMM), consists of a protein chain that terminates in a mentous protein, extends from the Z lines to the bare Tropomyosin Troponin Tn-T Tn-I Tn-C G-actin monomers Regulatory protein complex F-actin filament FIGURE 8. Nebulin, a filamentous protein Head portion that extends along the thin filaments, may play a role in sta- Tail portion S2 bilizing thin filament length during muscle development. The protein -actinin, associated with the Z lines, serves to S1 S1 Head Actin- anchor the thin filaments to the structure of the Z line. External to the cells, the protein laminin site forms a link between integrins and the extracellular matrix. S2 These proteins are disrupted in the group of genetic dis- eases collectively called muscular dystrophy, and their lack or malfunction leads to muscle degeneration and weakness and death (see Clinical Focus Box 8. Polymyositis is an inflammatory disorder that produces Myosin filament damage to several or many muscles (Clinical Focus Box 8. The progressive muscle weakness in polymyositis usu- ally develops more rapidly than in muscular dystrophy. New York: Springer-Verlag, tween the surface membrane and contractile filaments. In several forms of mus- these diseases is Duchenne’s muscular dystrophy cular dystrophy, both laminin and dystrophin are lacking (DMD) (also called pseudohypertrophic MD), which is an or defective. X-linked hereditary disease affecting mostly male children A disease as common and devastating as DMD has long (1 of 3,500 live male births). The recent identifica- gressive muscular weakness during the growing years, be- tion of three animals—dog, cat, and mouse—in which ge- coming apparent by age 4. A characteristic enlargement of netically similar conditions occur promises to offer signifi- the affected muscles, especially the calf muscles, is due to cant new opportunities for study. The manifestation of the a gradual degeneration and necrosis of muscle fibers and defect is different in each of the three animals (and also dif- their replacement by fibrous and fatty tissue. The mdx most sufferers are no longer ambulatory, and death usu- mouse, although it lacks dystrophin, does not suffer the ally occurs by the late teens or early twenties. Re- rious defects are in skeletal muscle, but smooth and car- search is underway to identify dystrophin-related proteins diac muscle are affected as well, and many patients suffer that may help compensate for the major defect. A related (and cause of their rapid growth, are ideal for studying the nor- rarer) disease, Becker’s muscular dystrophy (BMD), mal expression and function of dystrophin. Progress has has similar symptoms but is less severe; BMD patients of- been made in transplanting normal muscle cells into mdx ten survive into adulthood. Some six other rarer forms of mice, where they have expressed the dystrophin protein. A Using the genetic technique of chromosome mapping gene expressing a truncated form of dystrophin, called (using linkage analysis and positional cloning), re- utrophin, has been inserted into mice using transgenic searchers have localized the gene responsible for both methods and has corrected the myopathy. DMD and BMD to the p21 region of the X chromosome, The mdx dog, which suffers a more severe and human- and the gene itself has been cloned. It is a large gene of like form of the disease, offers an opportunity to test new some 2. About shows prominent muscle fiber hypertrophy, a poorly un- one third of DMD cases are due to new mutations and the derstood phenomenon in the human disease. Taking ad- other two thirds to sex-linked transmission of the defective vantage of the differences among these models promises gene. The BMD gene is a less severely damaged allele of to shed light on many missing aspects of our understand- the DMD gene. The product of the DMD gene is dystrophin, a large pro- tein that is absent in the muscles of DMD patients. The function of dy- References strophin in normal muscle appears to be that of a Burkin DJ, Kaufman SJ. The alpha7beta1 integrin in mus- cytoskeletal component associated with the inside surface cle development and disease. The childhood muscular dystrophies: most important of these is laminin 2, a protein associated Making order out of chaos. A skeletal muscle fiber is surrounded on its outer sur- gitudinal elements terminate in a system of terminal cister- face by an electrically excitable cell membrane supported nae (or lateral sacs). These contain a protein, calsequestrin, by an external meshwork of fine fibrous material.

Can Cause Large Changes in Venous Volume Unfortunately order betapace 40 mg online 10, measurements of the peripheral venous pressure generic betapace 40mg on-line heart attack pulse, such as the pressure in an arm or leg vein, are sub- Systemic veins are approximately 20 times more compliant ject to too many influences (e. If 500 mL of blood is infused into the circulation, about 80% (400 mL) locates in the systemic circulation. This in- crease in systemic blood volume raises mean circulatory Cardiac Output Is Sensitive to Changes filling pressure by a few mm Hg. This small rise in filling in Central Blood Volume pressure, distributed throughout the systemic circulation has a much larger effect on the volume of systemic veins Consider what happens if blood is steadily infused into the than systemic arteries. Because of the much higher compli- inferior vena cava of a normal individual. As this occurs, the ance of veins than arteries, 95% of the 400 mL (or 380 mL) volume of blood returning to the chest—venous return—is is found in veins, and only 5% (20 mL) is found in arteries. This difference between the input and output of atmospheric) results in little distention of arteries because blood produces an increase in central blood volume. It will of their low compliance, but results in considerable disten- occur first in the right atrium where the accompanying in- tion of veins because of their high compliance. In fact, ap- crease in pressure enhances right ventricular filling, end-di- proximately 550 mL of blood is needed to fill the stretched astolic fiber length, and stroke volume. Increased flow into veins of the legs and feet when an average person stands up. Left cardiac output will increase according but to a lesser extent, because the increase in transmural to Starling’s law, so that the output of the two ventricles ex- pressure is less. Cardiac output will increase until it equals Blood is redistributed to the legs from the central blood the sum of the previous venous return to the heart plus the volume by the following sequence of events. However, much of the blood reaching the legs remains in the veins as Central Blood Volume Is Influenced by they become passively stretched to their new size by the in- Total Blood Volume and Its Distribution. As cardiac output exceeds venous re- of the ventricles, and therefore, central blood volume is an turn for a few beats, the central blood volume falls (as does important influence on cardiac output. Central blood vol- the end-diastolic fiber length, stroke volume, and cardiac ume is altered by two events: changes in total blood volume output). Once the veins of the legs reach their new steady- and changes in the distribution of total blood volume be- state volume, the venous return again equals cardiac output. The equality between venous return and cardiac output is reestablished even though the central blood volume is re- Changes in Total Blood Volume. However, the new cardiac output and ve- blood volume can occur as a result of an infusion of fluid, nous return are decreased (relative to what they were before the retention of salt and water by the kidneys, or a shift in standing) because of the reduction in central blood volume. A decrease in Without compensation, the resulting decrease in systemic blood volume can occur as a result of hemorrhage, losses arterial pressure would cause a drop in brain blood flow and through sweat or other body fluids, or the transfer of fluid loss of consciousness. Compensatory events, including in- from plasma into the interstitial space. In the absence of creased activity of the sympathetic nervous system, to be compensatory events, changes in blood volume result in discussed in Chapter 18, are required to maintain arterial proportional changes in both central and extrathoracic pressure in the face of decreased cardiac output. For example, a moderate hemorrhage (10% When the smooth muscle of the systemic veins con- of blood volume) with no distribution shift would cause a tracts, the compliance of the systemic veins decreases. The reduced central results in a redistribution of blood volume toward the cen- blood volume would, in the absence of compensatory tral blood volume. Venoconstriction is an important com- events, lead to decreased filling of the ventricles and di- pensatory mechanism following hemorrhage. Central blood volume can be altered by a shift in blood volume to or away from the periphery. Shifts in the distribution of blood volume THE COUPLING OF VENOUS RETURN occur for two reasons: a change in transmural pressure or a AND CARDIAC OUTPUT change in venous compliance. Changes in the transmural pressure of vessels in the Because the blood moves in a closed circuit, venous re- chest or periphery enlarge or diminish their size. Because turn—the flow of blood from the periphery back to the there is a finite volume of blood, it shifts in response to right atrium—must equal cardiac output. The interplay be- changes in transmural pressure in one or the other of these tween venous return and cardiac output can be analyzed regions. Imagine a long balloon filled with water: If it is from the viewpoint of the heart or the systemic circulation.