By Q. Gorn. Lees-McRae College. 2018.
Rupture of the tendon of the biceps brachii muscle at the elbow is rare and constitutes less than 5% of all biceps Triceps Tendon tendon injuries purchase 20 mg adalat otc. Injuries to the musculotendinous junction Rupture of the triceps tendon is quite rare cheap 20 mg adalat with mastercard. The mecha- have been reported purchase adalat 30mg with amex, but the most common injury is com- nism of injury has been reported to result from a direct plete avulsion of the tendon from the radial tuberosity trusted 20 mg adalat. Similar to the pathology encountered in the isting changes in the distal biceps tendon, due to intrinsic distal biceps tendon, most ruptures occur at the insertion tendon degeneration, enthesopathy at the radial tuberosi- site, although musculotendinous junction and muscle bel- ty, or cubital bursal changes. Complete ruptures are injury relates to forceful hyperextension applied to a more common than partial tears. Athletes involved in may include olecranon bursitis, subluxation of the ulnar strength sports, such as competitive weightlifting, foot- nerve, or fracture of the radial head. With more than 2 cm classic presentation of a complete distal biceps rupture is of retraction between the origin and the insertion, a 40% that of a mass in the antecubital fossa due to proximal mi- loss of extension strength can result. Accurate diagnosis is For MRI diagnosis of triceps tendon pathology, it is more difficult in cases of the rare partial tear of the ten- imperative to be aware that the triceps tendon appearance don, or more common complete tear of the tendon with- is largely dependent on arm position. The latter can occur with an intact bicipi- pear lax and redundant when imaged in full extension, tal aponeurosis, which serves to tether the ruptured ten- whereas it is taut in flexion. MRI diagnosis of biceps tendon pathology becomes important in patients who do not present with the classic Entrapment Neuropathy history or mass in the antecubital fossa, or for evaluation of the integrity of the lacertus fibrosus. MRI diagnosis of The ulnar, median and radial nerves may become com- tendon pathology, as previously mentioned, is largely de- pressed at the elbow, leading to symptoms of entrapment pendent on morphology, signal intensity and the identifi- neuropathy. Abnormal nerves may have increased signal cation of areas of tendon discontinuity (Fig. In the intensity on T2-weighted images, focal changes in girth, and deviation that may result from subluxation or dis- placement by an adjacent mass. Nerve compression may be caused by a medial trochlear osteophyte or incongruity between the trochlea and olecranon process. The absence of the triangular reticulum, the anatomic roof of the cubital tunnel, occurs in about 10% of cases, permitting subluxation of the nerve with flexion. It is necessary, therefore, to include axial images of the flexed elbow in patients suspected of this disorder. The presence of the anomalous anconeous epitrochlearis muscle over the cubital tunnel causes sta- tic compression of the nerve. In addition, there are many other causes of ulnar neuritis, including thickening of the overlying ulnar collateral ligament, medial epicondylitis, adhesions, muscle hypertrophy, direct trauma, and callus from a fracture of the medial epicondyle. MRI can be used to identify these abnormalities and to assess the ul- nar nerve itself. If conservative treatment fails, the nerve can be transposed anteriorly, deep to the Fig. Axial-fat-suppressed T2-weighted image shows complete flexor muscle group, or more superficially, in the subcu- disruption of the distal biceps at the radial tuberosity (arrow) taneous tissue. Steinbach postoperatively if they become symptomatic to deter- phy of the elbow and wrist. Semin Musculoskelet Radiol mine whether symptoms are secondary to scarring or in- 2(4):397-414 8. Phillips CS, Segalman KA (2002) Diagnosis and treatment of fection around the area of nerve transposition. Hand Clin 18(1):149-159 osseous or muscular variants and anomalies, soft-tissue 9. Mulligan SA, Schwartz ML, Broussard MF, Andrews JR masses and dynamic forces. In the pronator syndrome, (2000) Heterotopic calcification and tears of the ulnar collat- compression occurs as the median nerve passes between eral ligament: radiographic and MR imaging findings.
However discount adalat 30 mg otc, if stroke work is plotted buy 30mg adalat with amex, a leftward shift of the ventricular function curve is observed (see Fig order 30mg adalat otc. A ventricular function curve with stroke volume on the ordi- Time nate can be used to indicate changes in contractility only when arterial pressure does not change purchase adalat 20 mg on-line. During heart failure, the ventricular function curve is shifted to the right, causing a particular end-diastolic fiber length to be associated with less force of contraction and/or shortening and a smaller stroke volume. As described in Chapter 10, cardiac glycosides, such as digitalis, tend to B normalize contractility; that is, they shift the ventricular curve of the failing heart back to the left (see Fig. A Time The collection of ventricular function curves reflecting changes in contractility in a particular heart is known as a family of ventricular function curves. In the normal heart, the force of contraction is also increased by myocardial hypertrophy. A Regular, intense exercise results in increased synthesis of contractile proteins and enlargement of cardiac myocytes. B The latter is the result of increased numbers of parallel my- ofilaments, increasing the number of actomyosin cross- bridges that can be formed. As each cell enlarges, the ven- Force (load) tricular wall thickens and is capable of greater force development. The ventricular lumen may also increase in size, and this is accompanied by an increase in stroke vol- FIGURE 14. The hearts of appropriately trained athletes are capa- volume, and the force-velocity relationship are shown for (A) ble of producing much greater stroke volumes and cardiac normal and (B) elevated aortic pressure. These changes slows the velocity of shortening, decreasing ventricular empty- are reversed if the athlete stops training. In heart disease, al- though myocardial hypertrophy initially has positive ef- fects, it ultimately has negative effects on myocardial force development. A thorough discussion of pathological hy- Fortunately, the heart can compensate for the de- pertrophy is beyond the scope of this book. The second determinant of stroke terial pressure causes the left ventricle to eject less blood volume is afterload (see Table 14. Left ventricular filling subsequently exceeds its circumstances, afterload can be equated to the aortic pres- output. If arterial pressure is suddenly in- the left ventricle increase, the ventricular force of con- creased, a ventricular contraction (at a given level of con- traction is enhanced. A new steady state is quickly tractility and end-diastolic fiber length) produces a lower reached in which the end-diastolic fiber length is in- stroke volume. This decrease can be predicted from the creased and the previous stroke volume is maintained. The shortening velocity of ventricular muscle de- During the next 30 seconds, the end-diastolic fiber creases with increasing load, which means that for a given length returns toward the control level, and the stroke duration of contraction (reflecting the duration of the ac- volume is maintained despite the increase in aortic pres- tion potential), the lower velocity results in less shortening sure. If arterial pressure times stroke volume (stroke and a decrease in stroke volume (Fig. This leftward shift of the ventricu- lar function curve indicates an increase in contractility. The ventricular radius influences stroke volume because of the relationship be- tween ventricular pressures (Pv) and ventricular wall ten- sion (T). For a hollow structure, such as a ventricle, Laplace’s law states that Pv T (1/r1 1/r2 where r1 and r2 are the radii of curvature for the ventricular FIGURE 14. The pressure inside an inflated balloon is ture, in which curvature occurs in only one dimension (i. The tension is lower in the portion of the balloon with the smaller radius. Pv T (1/r1) or T Pv r1 (4) The internal pressure expands the cylinder until it is ex- actly balanced by the wall tension. In this situation, compensatory events increase central the larger the tension needed to balance a particular pres- blood volume and end-diastolic pressure (see Chapter 18). For example, in a long balloon that has an inflated part higher end-diastolic pressure stretches the stiffer ventricle with a large radius and an uninflated parted with a much and helps restore the stroke volume to normal. The physio- smaller radius, the pressure inside the balloon is the same logical price for this compensation is higher left atrial and everywhere, yet the tension in the wall is much higher in pulmonary pressures. Several pathological consequences, in- the inflated part because the radius is much greater cluding pulmonary congestion and edema, can result.
This lowers the ability of plasma cause of high osmolalities in the villi appears to be greater ab- proteins to counteract capillary filtration discount adalat 20 mg on line, with the net re- sorption than removal of NaCl and nutrient molecules cheap adalat 20mg online. Eventu- is also a possible countercurrent exchange process in which ally generic adalat 30 mg line, this fluid must be removed purchase 30 mg adalat with visa. Not surprisingly, the materials absorbed into the capillary blood diffuse from the highest rates of intestinal lymph formation normally oc- venules into the incoming blood in the arterioles. Food Absorption Requires a High Blood Flow Sympathetic Nerve Activity Can Greatly Decrease to Support the Metabolism of the Mucosal Intestinal Blood Flow and Venous Volume Epithelium The intestinal vasculature is richly innervated by sympa- Lipid absorption causes a greater increase in intestinal thetic nerve fibers. Major reductions in gastrointestinal blood flow, a condition known as absorptive hyperemia, blood flow and venous volume occur whenever sympa- and oxygen consumption than either carbohydrate or thetic nerve activity is increased, such as during strenuous amino acid absorption. During absorption of all three exercise or periods of pathologically low arterial blood classes of nutrients, the mucosa releases adenosine and pressure. Venoconstriction in the intestine during hemor- CO and oxygen is depleted. The hyperosmotic lymph and rhage helps to mobilize blood and compensates for the 2 venous blood that leave the villus to enter the submucosal blood loss. Gastrointestinal blood flow is about 25% of the tissues around the major resistance vessels are also major cardiac output at rest; a reduction in this blood flow, by contributors to absorptive hyperemia. By an unknown heightened sympathetic activity, allows more vital func- mechanism, hyperosmolality resulting from NaCl induces tions to be supported with the available cardiac output. Hyperosmolality result- decreased by a combination of low arterial blood pressure ing from large organic molecules that do not enter en- (hypotension) and sympathetically mediated vasoconstric- dothelial cells does not cause appreciable increases in NO tion that mucosal tissue damage can result. These observations suggest that NaCl entering the en- HEPATIC CIRCULATION dothelial cells is essential to induce NO formation. The hepatic circulation perfuses one of the largest organs in The active absorption of amino acids and carbohydrates the body, the liver. The liver is primarily an organ that and the metabolic processing of lipids into chylomicrons maintains the organic chemical composition of the blood by mucosal epithelial cells place a major burden on the mi- plasma. For example, all plasma proteins are produced by crovasculature of the small intestine. There is an extensive the liver, and the liver adds glucose from stored glycogen network of capillaries just below the villus epithelial cells to the blood. The villus capillaries are unusual in and bacteria and detoxifies many man-made or natural or- that portions of the cytoplasm are missing, so that the two ganic chemicals that have entered the body. These areas of fusion, or closed fenestrae, are thought to facilitate the uptake of absorbed materials by The Hepatic Circulation Is Perfused by capillaries. In addition, intestinal capillaries have a higher Venous Blood From Gastrointestinal Organs filtration coefficient than other major organ systems, which and a Separate Arterial Supply probably enhances the uptake of water absorbed by the villi (see Chapter 16). However, large molecules, such as plasma The human liver has a large blood flow, about 1. It is perfused by both the reflection coefficient for the intestinal vasculature is arterial blood through the hepatic artery and venous greater than 0. CHAPTER 17 Special Circulations 283 The venous blood arrives via the hepatic portal vein and accounts for about 67 to 80% of the total liver blood flow (see Table 17. The remaining 20 to 33% of the total flow is through the hepatic artery. The majority of blood flow to the liver is determined by the flow through the stomach and small intestine. About half of the oxygen used by the liver is derived from venous blood, even though the splanchnic organs have removed one third to one half of the available oxygen. The liver has a high metabolic rate and is a large organ; consequently, it has the largest oxygen consumption of all organs in a resting person. The Liver Acinus Is a Complex Microvascular Unit With Mixed Arteriolar and Venular Blood Flow The liver vasculature is arranged into subunits that allow the arterial and portal blood to mix and provide nutrition for the liver cells. The core of each acinus is supplied by a single ter- minal portal venule; sinusoidal capillaries originate from this venule (Fig. A sin- gle liver acinus, the basic subunit of liver struc- ies have fenestrated regions with discrete openings that fa- ture, is supplied by a terminal portal venule and a terminal hepatic cilitate exchange between the plasma and interstitial spaces. The mixture of portal venous and arterial blood occurs The capillaries do not have a basement membrane, which in the sinusoidal capillaries formed from the terminal portal partially contributes to their high permeability.
During tinuously compensate for changes from the circular ciliary light to dark and from near to far buy adalat 30 mg with visa. The meridional aperture and lens system must continu- muscle fibers pull the origins of the long ously adapt to the prevailing conditions buy adalat 20mg amex. This relaxes both the requires a change in the curva- zonular fibers () generic adalat 20mg line, and the lens capsule generic adalat 30 mg without a prescription, ture of the lens (), a change thus causing the lens to round off (). During The fiber tracts of the (adjustment for long dis- are less well known. As fixation of an object tances), the surface of the lens is only is the prerequisite of accommodation, the slightly curved, the lines of sight run paral- optic nerve is the. During arch runs propably via the visual cortex (adjustment for short (striate area) to the pretectal nuclei, distances), the surface of the lens is dis- possibly also via the superior colliculi (). At the same time, it introduces, on the same set of pages, the im- vous system; 2) to emphasize points of clinical relevance through use portant concept that CNS anatomy, both external and internal, is ori- of appropriate terminology and examples; and 3) to integrate neuro- ented differently in MRI or CT. It is the clinical orientation issue that anatomical and clinical information in a format that will meet the edu- will confront the student/clinician in the clinical setting. The goal of the sixth edition is to continue appropriate to introduce, and even stress, this view of the brain and this philosophy and to present structural information and concepts in spinal cord in the basic science years. These include, in the basic science setting should ﬂow as seamlessly as possible into the but are not limited to, new examples of general vessel arrangement in clinical setting. MRA, examples of speciﬁc vessels in MRI, and some additional exam- I have received many constructive suggestions and comments from ples of hemorrhage. This is especially the case for the modiﬁ- Fourth, additional examples of cranial nerves traversing the sub- cations made in Chapters 2, 5, 7, 8, and 9 in this new edition. In fact, the number of MRI showing cra- names of the individuals who have provided suggestions or comments nial nerves has been doubled. In addition, each new plate starts with a are given in the Acknowledgments. This thoughtful and helpful input gross anatomical view of the nerve (or nerves) shown in the succeed- is greatly appreciated and has inﬂuenced the preparation of this new ing MRI in that ﬁgure. Fifth, additional clinical information and correlations have been in- The major changes made in the sixth edition of Neuroanatomy are as cluded. These are in the form of new images, new and/or modiﬁed ﬁg- follows: ure descriptions, and changes in other portions of the textual elements. First, recognizing that brain anatomy is seen in clear and elegant de- Sixth, in some instances, existing ﬁgures have been relocated to im- tail in MRI and CT, and that this is the primary way the brain is viewed prove their correlation with other images. In other instances, existing in the health care setting, additional new images have been incorporated ﬁgures have been repeated and correlated with newly added MRI or into this new edition. Every effort has been made to correlate the MRI CT so as to more clearly illustrate an anatomical-clinical correlation. New MRI or CT have been introduced study and review questions and answers in the USMLE style, has been into chapter 2 (spinal cord, meningeal hemorrhages correlated with the added. All of these questions have explained answers keyed to speciﬁc meninges, cisterns, hemorrhage into the brain, hemorrhage into the pages in the Atlas. Although not designed to be an exhaustive set, this ventricles correlated with the structure of the ventricles), chapter 5 new chapter should give the user of this atlas a unique opportunity for (spinal cord and brainstem), and chapter 8 (vascular). Second, the structure of the central nervous system should be avail- Two further issues ﬁgured prominently in the development of this able to the student (or the medical professional for that matter) in a for- new edition. First, the question of whether to use eponyms in their mat that makes this information immediately accessible, and applica- possessive form. To paraphrase one of my clinical colleagues “Parkin- ble, to the requirements of the clinical experience. It is commonplace son did not die of his disease (Parkinson disease), he died of a stroke; to present brain structure in an anatomical orientation (e. McKusick However, when the midbrain is viewed in an axial MRI or CT, the re- (1998a,b) has also made compelling arguments in support of using the verse is true: the colliculi are “down” in the image and the interpedun- non-possessive form of eponyms.