By Z. Randall. Maine Maritime Academy. 2018.
Hayes CW careprost 3 ml low price, Conway WF discount careprost 3 ml otc, Daniel WW (1993) MR imaging of AJR Am J Roentgenol 173:351-353 bone marrow edema pattern: transient osteoporosis, transient 8. Petersilge CA (2001) MR arthrography for evaluation of the bone marrow edema syndrome, or osteonecrosis. Watson RM, Roach NA, Dalinka MK (2004) Avascular necro- labrum: MRI in asymptomatic volunteers. Radiol Clin North Am Tomogr 22:1-7 42:207-219 IDKD 2005 Imaging of the Knee D. Palmer2 1 Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA 2 Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA Introduction ly infected arthroplasty usually requires combining the bone scan with an additional scintigraphic examination, This article addresses the spectrum of imaging modalities such as a sulfur colloid, labeled white blood cell, or in- that are commonly used in the knee, and describes their flammatory agent scan. Sonography is largely limited to an evaluation of the Emphasis is placed on magnetic resonance imaging extraarticular soft tissues of the knee but, with careful (MRI) and its value in knee trauma and on the biome- technique, at least partial visualization of the synovium chanical approach to understanding patterns of injury. Ultrasound is useful in the evaluation of overuse conditions of the patellar ten- don. Also, sonography easily demonstrates popliteal Imaging Modalities (Baker’s) cysts. Computed tomography (CT) is used most frequently to Conventional radiographs are the initial radiologic study evaluate intraarticular fractures about the knee, for plan- in most suspected knee disorders. Radiographs demon- ning complex orthopedic procedures, and for post-opera- strate joint spaces and bones, but are relatively insensitive tive evaluation. Maximal diagnostic information may ne- to soft-tissue conditions (except those composed largely cessitate reformatting the transversely acquired dataset of calcium or fat), destruction of medullary bone, and into orthogonal planes and/or 3D projections. A minimum examination consists cilitate reconstructions, multidetector-row helical acqui- of an AP and lateral projection. In patients with acute sitions with thin collimation (sub-millimeter, if possible) trauma, performing the lateral examination cross-table al- are preferred. Combining helical CT with arthrogra- lows identification of a lipohemarthrosis, an important phy makes it a viable examination for the detection of in- clue to the presence of an intraarticular fracture.
Sensory Organs © The McGraw−Hill Anatomy generic careprost 3ml on-line, Sixth Edition Coordination Companies buy discount careprost 3 ml on line, 2001 Chapter 15 Sensory Organs 493 FIGURE 15. Pain originating from the myocardium of the heart may be perceived as coming from the skin of the left arm because sensory impulses from these two organs are conducted through common nerve pathways to the brain. Proprioceptors are located in and around synovial joints, in Neural Pathways for Somatic Sensation skeletal muscle, between tendons and muscles, and in the inner ear. They are of four types: joint kinesthetic receptors, neuromus- The conduction pathways for the somatic senses are shown in cular spindles, neurotendinous receptors, and sensory hair cells. Sensations of proprioception and of touch and pres- sure are carried by large, myelinated nerve fibers that ascend in • Joint kinesthetic receptors are located in synovial joint the posterior columns of the spinal cord on the ipsilateral (same) capsules, where they are stimulated by changes in body po- side. These fibers do not synapse until they reach the medulla sition as the joints are moved. They consist of the medulla oblongata with second-order sensory neurons, informa- endings of sensory neurons that are spiraled around special- tion in the latter neurons crosses over to the contralateral (oppo- ized individual muscle fibers (fig. Third-order sensory caused by the lengthening or stretching of the individual neurons in the thalamus that receive this input in turn project to fibers, and thus provide information about the length of the postcentral gyrus in the cerebral cortex. Sensations of heat, cold, and pain are carried by thin, un- • Neurotendinous receptors (Golgi tendon organs) are lo- myelinated sensory neurons into the spinal cord. They within the spinal cord with second-order association neurons that are stimulated by the tension produced in a tendon when cross over to the contralateral side and ascend to the brain in the the attached muscle is either stretched or contracted. Fibers that mediate touch and pres- • Sensory hair cells of the inner ear are located in a fluid- sure ascend in the ventral spinothalamic tract. Fibers of both filled, ductule structure called the membranous labyrinth. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 494 Unit 5 Integration and Coordination Extrafusal fibers Intrafusal fibers: Nuclear chain fibers Skeletal muscle Nuclear bag fiber Peripheral nerve (Motor and sensory neurons) Connective tissue sheath Muscle Sensory neurons spindle Sensory neuron Neurotendinous receptors Motor neurons Tendon Bone Motor end plates (a) (b) FIGURE 15. Also, because of decussation (crossing- over), somatic information from each side of the body is projected Knowledge Check to the postcentral gyrus of the contralateral cerebral hemisphere. List the different types of cutaneous receptors and state All somatic information from the same area of the where they are located.
During a sustained contraction generic careprost 3ml free shipping, the pattern of activity is continually changed by the CNS generic careprost 3ml on line, and the bur- den of contraction is shared among the motor units. This results in a smooth contraction, with the force precisely controlled to produce the desired movement (or lack of it). Externally Imposed Conditions Also Affect Contraction Mechanical factors external to the muscle also influence the force and speed of contraction. For example, if a muscle is not allowed to shorten when it is stimulated, it will develop more force than it would if its length were allowed to change. If a muscle is in the process of lifting a load, its force of contraction is determined by the size of the load, Fusion of twitches into a smooth tetanus. The length of the muscle (marked on the graph by the pen attached near its lower end) is adjustable at rest but is held constant during contraction. The force transducer provides a record of the isometric force response to a single stimulus at a fixed length (isometric by definition). This load is called an af- terload, since its magnitude and presence are not apparent FIGURE 9. In the first contraction, there is a simple summation of two twitches; in the second, a brief tetanus of the apparatus used to study isometric contraction (Fig. Here the muscle is allowed to shorten while lifting an afterload, which is provided by the attached weight. This weight is chosen to present somewhat less than the peak Isometric Contraction. When the muscle is stimu- shortening when activated, the muscle will express its con- lated, it will begin to develop force without shortening, tractile activity by pulling against its attachments and de- since it takes some time to build up enough force to begin veloping force. After sufficient force has an isometric contraction can be studied by attaching a dis- been generated, the muscle will begin to shorten and lift sected muscle to an apparatus similar to that shown in Fig- the load (phase 2).
Crossing over and chromatid exchange occur tors and induces the appearance of LH receptors careprost 3ml on line. The re- bined activity of the two gonadotropins greatly amplifies sumption of meiosis careprost 3ml lowest price, ending the first meiotic prophase estrogen production. At low concentrations, andro- breakdown), and alignment of the chromosomes on the gens enhance aromatase activity, promoting estrogen pro- equator of the spindle. At high concentrations, androgens are converted ogous chromosomes move in opposite directions under by 5 -reductase to a more potent androgen, such as dihy- the influence of the retracting meiotic spindle at the cel- drotestosterone (DHT). At meiotic telophase 1, an unequal divi- by androgens, the intrafollicular androgenic environment sion of the cell cytoplasm yields a large secondary oocyte antagonizes granulosa cell proliferation and leads to apop- (2n DNA) and a small, nonfunctional cell, the first polar tosis of the granulosa cells and subsequent follicular atresia. Each cell contains half the original 4n number of chromosomes (only one member of each ho- Follicular Atresia Probably Results From a mologous pair is present, but each chromosome consists Lack of Gonadotropin Support of two unique chromatids). The secondary oocyte is formed several hours after the Follicular atresia, the degeneration of follicles in the ovary, initiation of the LH surge but before ovulation. It rapidly is characterized by the destruction of the oocyte and gran- begins the second meiotic division and proceeds through a ulosa cells. Atresia is a continuous process and can occur at short prophase to become arrested in metaphase. During a woman’s life- stage, the secondary oocyte is expelled from the graafian time approximately 400 to 500 follicles will ovulate; those follicle. In re- are the only follicles that escape atresia, and they represent sponse to penetration by a spermatozoon during fertiliza- a small percentage of the 1 to 2 million follicles present at tion, meiosis 2 resumes and is rapidly completed. The cause of follicular atresia is likely due to lack of unequal cell division soon follows, producing a small sec- gonadotropin support of the growing follicle. For example, ond polar body (1n DNA) and a large fertilized egg, the at the beginning of the menstrual cycle, several follicles are zygote (2n DNA, 1n from the mother and 1n from the fa- selected for growth but only one follicle, the dominant fol- ther). The first and second polar bodies either degenerate licle, will go on to ovulate. Because the dominant follicle or divide, yielding small nonfunctional cells. If fertilization has a preferential blood supply, it gets the most FSH (and does not occur, the secondary oocyte begins to degenerate LH).
