By O. Riordian. Illinois State University.

The larger bursae are the subdeltoid bursa cheap prinivil 5 mg with mastercard prehypertension caffeine, located the lateral side and an ulnar (medial) collateral ligament between the deltoid muscle and the joint capsule 5mg prinivil mastercard heart attack sam, and the sub- strengthens the medial side. A third joint occurs in the elbow region—the proximal ra- The subcoracoid bursa, which lies between the coracoid process dioulnar joint—but it is not part of the hinge. At this joint, the and the joint capsule, is frequently considered an extension of the head of the radius fits into the radial notch of the ulna and is subacromial bursa. A small subscapular bursa is located between held in place by the annular ligament. Because so many muscles originate or insert near the The shoulder joint is vulnerable to dislocations from sudden elbow, it is a common site of localized tenderness, inflam- jerks of the arm, especially in children before strong shoulder mation, and pain. Because of the weakness of this joint in tendinous soreness in this area. The structures most generally children, parents should be careful not to force a child to follow strained are the tendons attached to the lateral epicondyle of the by yanking on the arm. The strain is caused by repeated extension of the wrist painful and may cause permanent damage or perhaps muscle atro- against some force, as occurs during the backhand stroke in phy as a result of disuse. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 218 Unit 4 Support and Movement Joint capsule joint capsule Joint capsule (b) Joint (a) capsule (c) Joint capsule Joint capsule Joint capsule (d) (e) FIGURE 8. Metacarpophalangeal Each joint also has two collateral ligaments, one on the lateral side and one on the medial side, to further reinforce the joint and Interphalangeal Joints capsule. The metacarpophalangeal joints are condyloid joints, and the Athletes frequently jam a finger. It occurs when a ball forcefully interphalangeal joints are hinge joints. The articulating bones of strikes a distal phalanx as the fingers are extended, causing a the former are the metacarpal bones and the proximal phalanges; sharp flexion at the joint between the middle and distal phalanges. Each joint ligaments support the joint on the posterior side, but there is a tendon from the digital extensor muscles of the forearm. Treatment involves splinting each joint on the palmar, or anterior, side of the joint capsule. If splinting is not effective, surgery is generally performed to avoid a permanent crook in the finger. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 8 Articulations 219 Humerus Joint capsule (cut) Coronoid fossa Radial fossa Radial collateral ligament Articular cartilage Articular cartilage of capitulum of trochlea Ulnar collateral ligament Annular ligament Coronoid process Radius Ulna FIGURE 8. A portion of the joint capsule has been removed to show the articular surface of the humerus. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 220 Unit 4 Support and Movement Joint capsule Ligamentum capitis femoris FIGURE 8. The acetabular labrum, a fibrocartilaginous rim and the acetabulum of the os coxae (fig. It bears the weight that rings the head of the femur as it articulates with the acetab- of the body and is therefore much stronger and more stable than ulum, is attached to the margin of the acetabulum. The hip joint is secured by a strong fibrous joint capsule,several ligaments,and a number of powerful muscles. The liga- largest, most complex, and probably the most vulnerable joint mentum capitis femoris is located within the articular capsule in the body. It is a complex hinge joint that permits limited and attaches the head of the femur to the acetabulum. This is a rolling and gliding movements in addition to flexion and ex- relatively slack ligament, and does not play a significant role in tension. On the anterior side, the knee joint is stabilized and holding the femur in its socket. However, it does contain a small protected by the patella and the patellar ligament, forming a artery that supplies blood to the head of the femur. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 8 Articulations 221 Patellar surface FIGURE 8. Because of the complexity of the knee joint, only the prepatellar bursa, the suprapatellar bursa, the cutaneous relative positions of the ligaments, menisci, and bursae will prepatellar bursa, and the deep infrapatellar bursa (see fig.

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Metabolic rate measured under these % of conditions is called basal metabolic rate (BMR) cheap 10mg prinivil amex blood pressure chart 14 year old. The com- Heat Production monly accepted conditions for measuring BMR are that the % of person must have fasted for 12 hours; the measurement Body Mass Rest Exercise must be made in the morning after a good night’s sleep order prinivil 5mg on-line arteria interossea communis, be- Brain 2 16 1 ginning after the person has rested quietly for at least 30 Trunk viscera 34 56 8 minutes; and the air temperature must be comfortable, Muscle and skin 56 18 90 about 25 C (77 F). Basal metabolic rate is “basal” only dur- Other 8 10 1 ing wakefulness, since metabolic rate during sleep is some- what less than BMR. Heat exchange with the environment can be measured directly by using a human calorimeter. In this insulated bly because a higher proportion of the female body is com- chamber, heat can exit only in the air ventilating the cham- posed of fat, a tissue with low metabolism. By measuring the flow of air and water and their that have the greatest effect on metabolic rate. Cate- temperatures as they enter and leave the chamber, one can cholamines cause glycogen to break down into glucose determine the subject’s heat loss by conduction, convec- and stimulate many enzyme systems, increasing cellular tion, and radiation. Hypermetabolism is a clinical feature of of air entering and leaving the chamber, one can determine some cases of pheochromocytoma, a catecholamine-se- heat loss by evaporation. Thyroxine magni- calorimetry, and though conceptually simple, it is cumber- fies the metabolic response to catecholamines, increases some and costly. The metabolic rate is typically 45% above nor- try, which is based on measuring a person’s rate of O2 con- mal in hyperthyroidism (but up to 100% above normal in sumption, since virtually all energy available to the body severe cases) and 25% below normal in hypothyroidism depends ultimately on reactions that consume O2. Con- (but 45% below normal with complete lack of thyroid suming 1 L of O2 is associated with releasing 21. Other hormones have relatively minor effects kcal) if the fuel is carbohydrate, 19. An A resting person’s metabolic rate increases 10 to 20% af- average value often used for the metabolism of a mixed ter a meal. The ratio of CO2 food (formerly known as specific dynamic action), lasts produced to O2 consumed in the tissues is called the res- several hours. In a steady state where CO2 is ex- haled from the lungs at the same rate it is produced in the tissues, RQ is equal to the respiratory exchange ratio, R (see Chapter 19). One can improve the accuracy of indi- 54 rect calorimetry by also determining R and either estimat- 62 52 ing the amount of protein oxidized—which usually is 60 58 50 small compared to fat and carbohydrate—or calculating it 56 48 from urinary nitrogen excretion. Even 44 50 48 42 during mild exercise, the muscles are the principal source of 46 Males 40 metabolic heat, and during intense exercise, they may ac- 44 38 count for up to 90%. Moderately intense exercise by a 42 36 healthy, but sedentary, young man may require a metabolic 40 34 rate of 600 W (in contrast to about 80 W at rest), and in- 38 Females 36 32 tense activity by a trained athlete, 1,400 W or more. Be- 34 30 cause of their high metabolic rate, exercising muscles may 28 be almost 1 C warmer than the core. Blood perfusing these 0 5 1015202530354045 50 55 60 65 70 75 muscles is warmed and, in turn, warms the rest of the body, Age (yr) raising the core temperature. Effects of age and sex on the basal meta- Muscles convert most of the energy in the fuels they FIGURE 29. During here is expressed as the ratio of energy consumption to body sur- phosphorylation of ADP to form ATP, 58% of the energy face area. When a muscle contracts, some of the energy in from the warmer to the cooler body. The efficiency at this stage varies tually all thermal radiation is in a region of the infrared enormously; it is zero in isometric muscle contraction, in range where most surfaces, other than polished metals, have which a muscle’s length does not change while it develops emissivities near 1 and emit with a power output near the tension, so that no work is done even though metabolic en- theoretical maximum. Finally, some of the mechanical work pro- to glow, such as the sun, emit large amounts of radiation in duced is converted by friction into heat within the body. Therefore, colors of skin and clothing affect heat ex- 25% of the metabolic energy released during exercise is change only in sunlight or bright artificial light. Evaporation of water is, thus, an efficient way of losing heat, and it is the body’s only means of los- Convection, Radiation, and Evaporation Are ing heat when the environment is hotter than the skin, as the Main Avenues of Heat Exchange With it usually is when the environment is warmer than 36 C. In thermal physiology, orated in the heat comes from sweat, but even in cold tem- the fluid is usually air or water in the environment or blood, peratures, the skin loses some water by the evaporation of in the case of heat transfer inside the body. To illustrate, insensible perspiration, water that diffuses through the consider an object immersed in a fluid that is cooler than skin rather than being secreted. Heat passes from the object to the immediately always positive, representing heat loss from the body.

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Researchers working on the development of observational databases are beginning to combine retrospective research with prospective research purchase prinivil 2.5mg pulse pressure difference. Trials are translated into software purchase 10mg prinivil overnight delivery hypertension webmd, distributed electronically, and added to an electronic medical record. Based on the data in that record, the system automatically detects patients eligible for a trial. It then informs the clinician that the patient is eligible, and requests permission to include them in the trial. The system subsequently performs the randomisation between treatment arms during patient consultation, and the electronic record supports subsequent data collection. As a result, the boundaries between an electronic record, a decision support system, and systems for clinical trials are beginning to fade. Each patient–doctor encounter, each investigation, each laboratory test, and each treatment in medical practice constitutes, in principle, an experiment. Paper as a medium to record data limits our ability to exploit that potential. Electronic medical records will facilitate research that relies on data recorded in routine medical practice. The potential of ICT, however, lies in its ability to close the loop between clinical practice, research, and education. The Computer-Based Patient Record: An Essential Technology for Health Care (revised edn). Comparison of computer-aided and human review of general practitioners’ management of hypertension. The role of electronic patient records in the development of general practice in the Netherlands. Effects of computer-based decision support systems on clinician performance and patient outcomes: a systematic review. Postmarketing surveillance based on electronic patient records: the IPCI project. In residency training, both practice guidelines and evidence-based medicine are seen as responses to the psychological limitations of unaided clinical judgement. Introduction This chapter reviews the cognitive processes involved in diagnostic reasoning in clinical medicine and sketches our current understanding of these principles. It describes and analyses the psychological processes and mental structures employed in identifying and solving diagnostic problems of varying degrees of complexity, and reviews common errors and pitfalls in diagnostic reasoning. It does not consider a parallel set of issues in selecting a treatment or developing a management plan. For theoretical background we draw upon two approaches that have been particularly influential in research in this field: problem solving1–6 and decision making. Psychological decision research has typically looked at factors affecting diagnosis or treatment choice in well defined, tightly controlled problems. Despite a common theme of limited rationality, the problem-solving paradigm focuses on the wisdom of practice by concentrating on identifying the strategies of experts in a field to help learners acquire them more efficiently. Research in this tradition has aimed at providing students with some guidelines on how to develop their skills in clinical reasoning. Consequently, it has emphasised how experts generally function effectively despite limits on their rational capacities. Behavioural decision research, on the other hand, contrasts human performance with a normative statistical model of reasoning under uncertainty, Bayes’ theorem. This research tradition emphasises positive standards for reasoning about uncertainty, demonstrates that even experts in a domain do not always meet 180 CLINICAL PROBLEM SOLVING AND DIAGNOSTIC DECISION MAKING these standards, and thus raises the case for some type of decision support. Behavioural decision research implies that contrasting intuitive diagnostic conclusions with those that would be reached by the formal application of Bayes’ theorem would give us greater insight into both clinical reasoning and the probable underlying state of the patient. Problem solving: diagnosis as hypothesis selection To solve a clinical diagnostic problem means, first, to recognise a malfunction and then to set about tracing or identifying its causes. The diagnosis is ideally an explanation of disordered function – where possible, a causal explanation. The level of causal explanation changes as fundamental scientific understanding of disease mechanisms evolves. In many instances a diagnosis is a category for which no causal explanation has yet been found. In most cases, not all of the information needed to identify and explain the situation is available early in the clinical encounter, and so the clinician must decide what information to collect, what aspects of the situation need attention, and what can be safely set aside.

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