By L. Cole. Arizona International College.
However discount accutane 10mg without prescription acne 40 year old woman, during exercise-induced hyperpnea vide good control in the presence of considerable varia- (increased depth and rate of breathing) buy generic accutane 10mg on-line acne young living, the cords are sepa- tions of other properties of the system, such as lung stiff- rated during expiration and expiratory resistance is reduced. They can, if sufficiently sensitive, act quickly to reduce discrepancies from refer- ence points to very low levels. Too much sensitivity, how- REFLEXES FROM THE LUNGS AND CHEST WALL ever, may lead to instability and undesirable excursions of the regulated variable. Reflexes arising from the periphery provide feedback for Other mechanisms involve minimization or optimiza- fine-tuning, which adjusts frequency and tidal volume to tion. For example, evidence indicates that rate and depth of minimize the work of breathing. Reflexes from the upper breathing are adjusted to minimize the work expenditure airways and lungs also act as defensive reflexes, protecting for ventilation of a given magnitude. This sec- controller decides whether to use a large breath with its at- tion considers reflexes that arise from the lungs and chest tendant large elastic load or more frequent smaller breaths wall. Among reflexes influencing breathing, the lung and with their associated higher resistive load. This strategy re- chest wall mechanoreceptors and the chemoreflexes re- quires afferent neural information about lung volume, rate sponding to blood pH and gas tension changes are the most of volume change, and transpulmonary pressures, which widely recognized. Although many other less well-ex- can be provided by lung and chest wall mechanoreceptors. Examples are reflexes induced by with, among other things, the feedback control of carbon changes in arterial blood pressure, cardiac stretch, epicar- dioxide described earlier. As a final example, an optimiza- dial irritation, sensations in the airway above the trachea, tion model using two pieces of information is illustrated in skin injury, and visceral pain. Breathing is adjusted to minimize the sum of the muscle effort and the sensory “cost” of tolerating a raised PaCO. Three Classes of Receptors Are 2 Associated With Lung Reflexes Pulmonary receptors can be divided into three groups: Muscles of the Upper Airways Are slowly adapting receptors, rapidly adapting receptors, and C Also Under Phasic Control fiber endings. Afferent fibers of all three types lie predomi- The same rhythm generator that controls the chest wall nantly in the vagus nerves, although some pass with the sym- muscles also controls muscles of the nose, pharynx, and lar- pathetic nerves to the spinal cord. But unlike the inspiratory ramp-like rise of the stimu- thetic afferents is uncertain and is not considered further. The chemore- completed as the new ventilation alters blood gas composition ceptor signal is subtracted from a reference value. The components CO2 tolerance couplers convert neural drive and the output of the inside the dashed box constitute the controller. Ventilatory con- chemical homeostasis and to minimize respiratory effort are re- trol in hypercapnia and exercise: Optimization hypothesis. The slowly adapting recep- that are found in the larger conducting airways. They are tors are sensory terminals of myelinated afferent fibers that frequently called irritant receptors because these nerve lie within the smooth muscle layer of conducting airways. Rapidly adapting receptors are fire in proportion to applied airway transmural pressure, stimulated by histamine, serotonin, and prostaglandins re- and their usual role is to sense lung volume. Stimulation of these but their firing rate rapidly declines when a volume change receptors causes an excitation of the inspiratory off-switch is sustained. Because of this rapid adaptation, bursts of ac- and a prolongation of expiration. Because of these two ef- tivity occur that are in proportion to the change of volume fects, inflating the lungs with a sustained pressure at the and the rate at which that change occurs. Acute congestion mouth terminates an inspiration in progress and prolongs of the pulmonary vascular bed also stimulates these recep- the time before a subsequent inspiration occurs. This se- tors but, unlike the effect of inflation, their activity may be quence is known as the Hering-Breuer reflex or lung infla- sustained when congestion is maintained. Background activity of rapidly adapting receptors is in- The Hering-Breuer reflex probably plays a more impor- versely related to lung compliance, and they are thought to tant role in infants than in adults. These receptors are the awake state, this reflex may be overwhelmed by more probably nearly inactive in normal quiet breathing. Because increasing lung volume on what stimulates them, their role would seem to be to stimulates slowly adapting receptors, which then excite the sense the onset of pathological events. In spite of consider- inspiratory off-switch, it is easy to see how they could be able information about what stimulates them, the effect of responsible for a feedback signal that results in cyclic their stimulation remains controversial.
As we continue to make new discoveries about our struc- most specific taxon is the species buy cheap accutane 40mg on line acne xojane. Humans are species belonging ture and function discount 10mg accutane otc acne yahoo, our close relationship to other living organisms to the animal kingdom. Phylogeny (fi-loj′˘-nee ) is the science that becomes more and more apparent. Often, it is sobering to realize studies relatedness on the basis of taxonomy. As human organisms, we breathe, eat and digest food, excrete bodily Phylum Chordata wastes, locomote, and reproduce our own kind. These chordate characteristics are development is found throughout nature. The fundamental pat- well expressed during the embryonic period of development and, terns of development of many nonhuman animals also characterize to a certain extent, are present in an adult. Recent genetic mapping of flexible rod of tissue that extends the length of the back of an the human genome confirms that there are fewer than 35,000 embryo. A portion of the notochord persists in the adult as genes accounting for all of our physical traits. By far the majority the nucleus pulposus, located within each intervertebral disc of these genes are similar to those found in many other organisms. The dorsal hollow nerve cord is positioned above the In the classification, or taxonomic, system established by notochord and develops into the brain and spinal cord, which biologists to organize the structural and evolutionary relation- are supremely functional as the central nervous system in the ships of living organisms, each category of classification is re- adult. Body Organization and © The McGraw−Hill Anatomy, Sixth Edition Organization, and the Anatomical Nomenclature Companies, 2001 Human Organism 24 Unit 2 Terminology, Organization, and the Human Organism L4 L5 S1 (a) (b) FIGURE 2. In other chordates, such as humans, embryonic pha- Order Primates ryngeal pouches develop, but only one of the pouches persists, becoming the middle-ear cavity. Spinal nerves exit between vertebrae, and the discs maintain the spacing to avoid nerve damage. A “slipped disc,” resulting from straining the back, is Family Hominidae a misnomer. What actually occurs is a herniation, or rupture, because of a weakened wall of the nucleus pulposus. This may cause severe Humans are the sole living members of the family Hominidae. Homo sapiens is included within this family, to which all the vari- eties or ethnic groups of humans belong (fig. Each “racial group” has distinguishing features that have been established in Class Mammalia isolated populations over thousands of years. Our classification Mammals are chordate animals with hair and mammary glands. Hair is a thermoregulatory protective covering for most mam- Fostered by greater ease of travel and communication, more mals, and mammary glands serve for suckling the young frequent contact between diverse cultures has led to a break- (fig. Other characteristics of mammals include a convoluted down of some of the traditional barriers to interracial marriage. This (intricately folded) cerebrum, three auditory ossicles (bones), het- may lead to a mixing of the “gene pool,” so that distinct ethnic erodont dentition (teeth of various shapes), squamosal-dentary groups become less evident. Perhaps multiple ethnic ties in every- one’s pedigree would help reduce cultural hostility and strife. Body Organization and © The McGraw−Hill Anatomy, Sixth Edition Organization, and the Anatomical Nomenclature Companies, 2001 Human Organism Chapter 2 Body Organization and Anatomical Nomenclature 25 Mammary ridge Nipple Accessory nipples Creek (a) (b) FIGURE 2. Convoluted cerebrum Characteristics of Humans Hair As human beings, certain of our anatomical characteristics are so Three auditory specialized that they are diagnostic in separating us from other ossicles animals, and even from other closely related mammals. We also Well-developed have characteristics that are equally well developed in other ani- facial muscles mals, but when these function with the human brain, they pro- Squamosal-dentary vide us with remarkable and unique capabilities. Our anatomical jaw articulation characteristics include the following: Heterodont dentition 1. This Four-chambered heart with left gives us a large brain-to-body-weight ratio. But more im- aortic arch portant is the development of portions of the brain.
In emphysema order accutane 10mg free shipping acne 4 dpo, excess proteolytic activity de- CASE STUDY FOR CHAPTER 19 stroys elastin and collagen order 5mg accutane with amex acne rosacea pictures, the major extracellular matrix Emphysema proteins responsible for maintaining the integrity of the A 65-year-old man went to the university hospital emer- alveolar-capillary membrane and the elasticity of the lung. He also complained of arise through an increase in protease levels, a decrease in a cough productive of green sputum. Chronic obstructive pulmonary disease: An overview smoked two packs of cigarettes a day for the past 30 years, of pathology and pathogenesis. Novartis Found Symp he had recently decreased his habit to one pack a day. Although CASE STUDY FOR CHAPTER 20 he has had dyspnea upon exertion for the last 2 years, he continues to maintain an active lifestyle. He still mows his Chest Pain lawn without much difficulty, and can walk 1 to 2 miles on A 27-year-old accountant recently drove cross-country to a flat surface at a moderate pace. He denied having had any other sig- move, she started to experience chest pains. She drove nificant past medical problems, including heart disease, to the emergency department after experiencing 24 hypertension, edema, childhood asthma, or any allergies. She denied any sputum pro- An initial exam shows that the patient is thin but has duction, hemoptysis, coughing, or wheezing. His tive and walks daily and never has experienced any blood pressure is 130/80 mm Hg; respiratory rate, 28 to swelling in her legs. She has never been treated for any 32 breaths/min; heart rate, 92/minute; and oral tempera- respiratory problems and has never undergone any sur- ture, 37. Oral contraceptives are breath sounds in both lung fields, with expiratory wheez- her only medication. A pulse intravenous drugs and has no other risk factors for HIV oximetry reading reveals his blood hemoglobin oxygen disease. Her family history is negative for asthma and saturation is 91% when breathing room air. Pulmonary function tests reveal severe limitation of Physical examination reveals a mildly obese woman airflow rates, particularly expiratory airflow. Her blood Questions pressure is 140/80 mm Hg, and no jugular vein disten- 1. What are the common spirometry findings associated with sion is observed. What are the mechanisms of airflow limitation in emphy- and her temperature is 38 C. What is the most commonly held theory explaining the de- gases, obtained while she was breathing room air, reveal velopment of emphysema? Her alveolar-arterial (A-a)O2 gradient is Answers to Case Study Questions for Chapter 19 40 mm Hg. The hallmark of emphysema is the limitation of airflow out normal flora. In emphysema, expiratory flow rates (FVC, shadow and clear lung fields, except for a small periph- FEV1, and FEV1/FVC ratio) are significantly decreased. A lung scan reveals ever, some lung volumes (TLC, FRC, and RV) are increased, an embolus in the left lower lobe. What is the cause of a widened alveolar-arterial gradient in include hypersensitivity of airway smooth muscle, mucus patients with pulmonary embolism? What causes the decreased arterial PCO2 and elevated arte- creased dynamic airway compression as a result of in- rial pH? Many of the pathophysiological changes in emphysema are Answers to Case Study Questions for Chapter 20 a result of the loss of lung elastic recoil and destruction of 1. This is thought to be a re- embolus will cause blood flow to be shunted to another re- sult of an imbalance between the proteases and antipro- gion of the lung. Because cardiac output is unchanged, the teases ( 1-antitrypsin) in the lower respiratory tree. Nor- shunting of blood causes overperfusion, which causes an mally, proteolytic enzyme activity is inactivated by abnormally low A/ ratio in another region of the lungs. DLCO decreases with anemia because there is less hemoglo- poxemia (a low arterial PO2). In older ever, ventilation is also stimulated as a compensatory individuals, especially those who live alone, insufficient di- mechanism to hypoxemia, which leads to hyperventilation etary intake of animal protein may be the cause; other with a concomitant increase in alveolar PO2.
The posterior tibiofibular ligament order 5mg accutane amex acne queloide, also visible on icular in the lower layer of the spring ligament complex order accutane 30 mg free shipping skin care laser clinic, axial images at the tip of the fibula, is rarely torn. Early investigations have indicated that the calcane- Each of the three components can be visualized on MR ofibular ligament runs obliquely from the fibular tip pos- images. Therefore, oblique images have been considered to be superior in the Impingement Syndromes assessment of the ligament. In our experience, however, this plane is not clearly superior to coronal images in de- The role of impingement syndromes in producing chron- lineating the calcaneofibular ligament. This may be ex- ic ankle pain has been better appreciated in recent years. This is discussed more fully under the category of Among the four most common impingement syn- osseous injuries. Intra-articular synovial hypertrophy The tibiofibular syndesmosis is an important stabilizer of and fibrosis may occur in the lateral gutter secondary to the distal tibiofibular joint. It consists of the anteroinfe- capsular or ligamentous tears associated with inversion rior tibiofibular ligament, the posteroinferior tibiofibular injuries. This condition is optimally assessed with MR ligament, the transverse tibiofibular ligament, and the in- arthrography, although positive experience with this ap- terosseous tibiofibular ligament. Disruption or irregularities of the ligaments, ankle, excluding Morton’s neuroma, is tarsal tunnel syn- degenerative changes at the distal tibiofibular joint, and drome. The tarsal tunnel is a fibro-osseous space formed proximal extension of fluid into the lateral gutter (greater by the talar surface, the sustentaculum tali, and the cal- than 1 cm) aid in making the diagnosis. It is traversed by the posterior tibial, flexor dig- Medial Collateral Ligament itorum longus, and flexor hallucis longus tendons, the tibial nerve and its branches and accompanying vessels. The medial collateral ligament plays an important role in In about 50% of cases, tarsal tunnel syndrome is idio- medial ankle instability. Marked inter-individual differ- pathic, whereas in the other 50% a specific cause is iden- ences are found for the main components (tibionavicular, tified, such as space occupying lesions including gan- tibiospring, tibiocalcaneal, deep posterior and anterior glion, varicosities, lipoma, accessory muscles, and nerve- tibiotalar and superficial posterior tibiotalar bands). The sheath tumors, as well as pronation or hindfoot valgus de- tibionavicular ligament is a thickened fibrous layer of the formity, and fracture of the medial malleolus and calca- ankle capsule. Patients present with a positive Tinel’s sign and ments are the longest, while the tibiocalcaneal and poste- pain, burning and numbness along the plantar surface of rior deep tibiotalar ligaments are the thickest. Spring Ligament Entrapment neuropathies of branches of the tibial nerve include entrapment of the first branch of the lateral plan- The spring ligament plays an important role in the stabi- tar nerve (Baxter’s nerve), which presents with heel pain lization of the longitudinal arch in the midfoot. Zanetti is often associated with hypertrophy of the abductor hal- decrease in diameter is most likely caused by a change in lucis muscle but is also produced by inflammation asso- the location of the neuroma, which, as it becomes dislo- ciated with plantar fasciitis and heel spur. Another cause of heel pain, often seen in joggers and long-dis- tance runners is jogger’s foot, which is produced by en- Sinus Tarsi Syndrome trapment of the medial plantar nerve secondary to valgus heel deformity. Sinus tarsi syndrome most commonly develops after an Treatment of the entrapment neuropathies is initially inversion injury (70%) and is often associated with tears conservative but may require surgical release of the of the lateral collateral ligaments. US and tients with rheumatologic disorders or abnormal biome- MR imaging are the imaging modalities of choice for di- chanics, such as pes planes deformity and posterior tibial agnosing extrinsic mechanical compression of the tibial tendon dysfunction. MR imaging has the advantage The sinus tarsi is a lateral space located between the of depicting associated denervation muscle edema and talus and the calcaneus. More medially, the sinus tarsi is continuous with the tarsal canal in which the in- Morton’s Neuroma terosseous talocalcaneal ligaments traverse. Although the latter are not truly lateral structures, they are impor- Morton’s neuroma is a benign non-neoplastic abnormali- tant in the overall function of the lateral ankle and hind- ty characterized by neural degeneration and perineural foot complex. The plantar interdigital nerves of the second and Patients with sinus tarsi syndrome present with hind- third intermetatarsal spaces are most commonly involved. Associated MR mani- neuroma and is therefore considered to be useful for nar- festations include edema, sclerosis and cystic changes in rowing the differential diagnosis of forefoot pain. US has the roof of the sinus tarsi, cystic changes at the critical demonstrated comparably good results. Morton’s neuro- angle of Gissane, lateral collateral ligament tears, and, ma is of low signal intensity on T2-weighted MR images occasionally, posterior tibial tendon tear. The use of in- the subtalar joint and subchondral cysts may be present travenous gadolinium contrast is not recommended be- in advanced cases. MR imaging Fluid in the sinus tarsi should be differentiated from permits the exact location of Morton’s neuroma, allowing the normal extension of fluid from posterior subtalar joint for precise pre-surgical planning. An MR Plantar Fasciitis effectiveness study has demonstrated that the clinical diagnosis of Morton’s neuroma is altered in more than Plantar fasciitis is one of the more common overuse in- one fourth of cases following MR imaging, and a change juries in running sports. The plantar fascia is a multilay- in location or number occurs in one-third of the remain- ered fibrous aponeurosis that extends from the postero- ing cases.
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