Azigram"Buy azigram canada, antimicrobial towels". By: T. Domenik, M.B.A., M.D. Deputy Director, A.T. Still University School of Osteopathic Medicine in Arizona Muscle spindles constantly monitor muscle stretching and relay this information to the spinal cord for processing papillomavirus effective azigram 250mg. Muscle spindles generate essential reflexes that maintain posture and coordinate the actions of opposing muscle groups during body movement. Keywords: Muscle spindles 18 the answer is B: Muscle fibers are composed of multiple cells. Unlike skeletal muscle, where muscle fibers are multinucleated cells, cardiac muscle fibers are composed of multiple cells that make tight end-to-end connections. Cardiac muscle cells may split and unite, giving cardiac muscle a typical "branching" morphology. Cardiac and skeletal muscles both exhibit cross-striations-their thick and thin contractile filaments exhibit the same organization (choices C, D, E). The nuclei of skeletal muscle cells are located at the periphery of the fiber, whereas the nucleus of a cardiac myocyte is located in the center of the cell (shown in the image). This difference in nuclear location provides a useful means for distinguishing cardiac from skeletal muscle. Cardiac and skeletal muscle fibers are both invested with connective tissue that conveys nerves and capillaries (choice A). Keywords: Cardiac muscle Intercalated disks 19 the answer is C: Intercalated disks. In routine H&E histologic preparations, intercalated disks appear as darker-stained lines that cross the muscle fibers. They are composed of junctional complexes that form strong molecular bridges between cardiac myocytes. When examined by scanning electron microscopy, intercalated disks appear as steplike disks with transverse and lateral regions. In the transverse region, fascia adherens (the equivalent of zonula adherens in epithelial cells) and desmosomes mediate cell adhesion. Gap junctions and desmosomes are found in the lateral region of the intercalated disk. The other structures (lines and bands) are present in cardiac myocytes, but they do not contribute to the morphology of intercalated disks, and they would not be visible at this magnification. As mentioned above, skeletal muscle contraction is initiated by the release of acetylcholine from motor neurons at neuromuscular junctions (motor end plates). By contrast, cardiac muscle contractions are initiated, regulated, and coordinated by a cardiac conducting system. It includes nodal tissue that generates intrinsic cardiac contractile impulses and conducting fibers. Purkinje fibers transmit contractile impulses to heart muscle in a rapid and precise sequence, leading to spontaneous and rhythmic cardiac contractions (heart beats). Gap junctions are molecular pores that permit ions and other small molecules to pass between adjacent cells. Gap junctions are found in the lateral regions of the intercalated disks in cardiac muscle. They permit electrochemical signals to move between cardiac myocytes (ionic coupling). Gap junction communication enables cardiac muscle cells to form an electrochemical syncytium that helps maintain a normal heart rhythm. Smooth muscle is an involuntary and nonstriated muscle that is widely distributed in the body. For example, smooth muscle is found in the gastrointestinal tract, blood vessels, urinary bladder, uterus, male/female reproductive tracts, and iris of the eye. In longitudinal sections, smooth muscle fibers appear as elongated fusiform cells with central nuclei and uniformly eosinophilic cytoplasm (illustrated in the image). Depending on location, the length of smooth muscle fibers varies from 20 m (media of small blood vessel) to 500 m (myometrium of pregnant uterus). None of the other tissues exhibit the distinctive histologic features of smooth muscle. In addition to their contractile properties, smooth muscle cells demonstrate the characteristic features of secretory cells. For example, endomysium, a thin layer of connective tissue, and the basal lamina that surrounds smooth muscle fibers are produced and deposited by smooth muscle cells. Reticular fibers in the endomysium form an intricate network that supports the parenchymal cells and binds them together. Tight (occluding) junctions between the ductal epithelial cells form an impermeable barrier antibiotics for acne and birth control discount azigram amex. As a result of these zonula occludens junctions, the lateral membrane borders between adjacent ductal cells are not visible by light microscopy (shown in the image). It may reflect the need for greater support, or it may represent a transition zone for epithelial tissues that are switching from simple to stratified. None of the other types of epithelium describe histologic features of these sweat ducts in the dermis of the skin. As mentioned above, capillary endothelial cells are characterized by the presence of tight junctions that establish a permeability barrier between blood and extravascular interstitial tissue. These occluding junctions (zonula occludens) bring the lipid bilayers of adjacent cells into close proximity. Zonula occludens are composed principally of three proteins: occludin, claudin, and junctional adhesion molecule. The extracellular portions of these transmembrane proteins form a zipper-like structure that seals the intercellular space and limits paracellular fluid transport. Parenthetically, transcellular transport occurs when biomolecules move across the plasma membrane. These cellular changes lead to the leakage of fluid from the blood into the surrounding extravascular space (referred to as edema fluid). In some organs, capillary endothelial cells exhibit small windows (fenestrae) that facilitate the transport of biomolecules across the endothelium. Keywords: Tight junctions, zonula occludens 12 the answer is B: Stratified columnar. This image shows stratified columnar epithelium lining an excretory duct in the lip. The cells facing the lumen are taller than they are wide, hence the classification of this epithelium as stratified columnar. None of the other types of epithelial tissue describes the histologic features of this large excretory duct. Keywords: Excretory duct 26 Chapter 2 13 the answer is B: Loss of cell contact inhibition of growth and motility. In brief, maturation of the epidermis requires an intact layer of basal stem cells that are in direct contact with one another. If this contact is disrupted, basal cells at the margin of the wound become activated. When epithelial continuity is reestablished, cell migration and cell division cease, and normal epidermal maturation resumes. This mechanism of epithelial growth regulation is referred to as "contact inhibition of growth and motility. The other choices describe responses to deep wounds that involve the formation of granulation tissue. Keywords: Skin abrasion, epithelial regeneration 14 the answer is E: Transitional. The renal calyces, ureters, urinary bladder, and proximal urethra are lined by a transitional epithelium. Urothelium is stratified and appears to consist of five or six cell layers when the bladder is empty (shown in the image). Upon distention, however, the same epithelium would appear to consist of only three layers. The superficial cells are typically described as being cuboidal and dome shaped, because they appear to bulge into the lumen. Hematuria may be a symptom of an ascending urinary tract infection or (less commonly) bladder cancer. None of the other types of epithelium describes histologic features of the bladder mucosa. Keywords: Urinary bladder, urothelium 15 the answer is A: Ciliated pseudostratified columnar with goblet cells. When keratinocytes in the stratum spinosum release filaggrin and trichohyalin antimicrobial doormats purchase azigram 250mg online, their keratin filaments aggregate to form bundles that are referred to as tonofibrils. Thus, filaggrin and trichohyalin initiate the transformation of granular cells to cornified cells. During keratinization, cell nuclei and cytoplasmic organelles are degraded, and plasma membranes are thickened. The stratum lucidum is identified in the image associated with Question 5 (small arrows, shown in the image). The cells in this layer appear pink, because the tonofibrils are eosinophilic when stained with H&E. With the formation of tonofibrils, granular cells are converted into cornified (keratinized) cells that leave the stratum granulosum and enter the stratum corneum. Superficial cells are continuously sloughed off from the surface of the skin (exfoliation). The stratum corneum is constantly renewed by keratinocytes arising from deeper layers of the epidermis. It is the thickest in the palm of the hand and the sole of the foot, where the skin is subject to constant abrasion ("wear and tear"). Keywords: Epidermis, stratum corneum 9 the answer is D: Excessive thickening of the stratum corneum. Ichthyosis vulgaris is a relatively common, autosomal dominant genetic disease (afflicting 1/250). Hyperkeratosis in the stratum corneum and reduced or absent keratohyalin granules are the characteristic pathologic features of this congenital disease. None of the other mechanisms of disease describe the pathogenesis of ichthyosis vulgaris. Keywords: Ichthyosis vulgaris, epidermis, stratum corneum 105 10 the answer is E: Stratum basale and stratum spinosum of epidermis. Pemphigus vulgaris is a chronic blistering skin disorder, secondary to diminished cohesion between keratinocytes. The blisters are suprabasal, meaning that the stratum basale separates from outer layers of the epidermis (shown in the image). The basal layer is intact and remains adherent to the basement membrane that forms the floor of the blister. Distinctive, rounded keratinocytes are also shed into the lumen of the vesicle (acantholytic keratinocytes). None of the other layers of the skin exhibit physical separation in patients with pemphigus vulgaris. This experimental result is consistent with the deposition of immune complexes at points of contact between keratinocytes. None of the other membrane-associated structures serve as primary adhesive junctions between keratinocytes. The lowermost portion of the basal cell cytoplasm separates from the upper portion of the cells. Small pieces of basal cell cytoplasm remain attached to the basement membrane and form the floor of the vesicle. Keratin intermediate filament proteins provide essential mechanical stability to keratinocytes. Bullous pemphigoid (choice A) and pemphigus vulgaris (choice D) are autoimmune blistering skin diseases that are caused by autoantibodies to normal skin proteins. Actinic keratosis is a form of dysplasia in sun-exposed skin (actin meaning rays). Histologically, such lesions are composed of atypical 106 Chapter 8 squamous cells that vary in size and shape. This mucus conditions the inspired air and helps trap particles and pathogens that move through the upper respiratory tree zombie infection android purchase on line azigram. Ciliated columnar cells are the most numerous type of cell in the respiratory epithelium. Hairlike motile cilia arise from the apical surface of the columnar epithelial cells. The cilia move in a coordinated sweeping fashion to move mucus and entrapped particles up the respiratory tree, toward the oropharynx. This coordinated ciliary movement (commonly referred to as the mucociliary ladder) is an important protective mechanism for the respiratory system. None of the other choices are related to the function of ciliated cells in respiratory epithelium. Keywords: Trachea, ciliated epithelial cells, cilia 158 Chapter 11 24 the answer is E: Small granule cells. Small granule cells (also referred to as Kulchitsky cells or enterochromaffin cells) account for about 3% of cells in the respiratory epithelium. These neuroendocrine cells are difficult to distinguish from basal cells in routine histological preparations. Small granule cells are believed to be part of the "diffuse neuroendocrine system. Their secretions include catecholamines, serotonin, calcitonin, and gastrin-releasing peptide. A characteristic feature of the trachea is the presence of a thick basement membrane visible by light microscopy. This membrane becomes thicker in smokers as a response to chronic mucosal irritation. Lamina propria (choice B) is the underlying loose connective tissue layer that contains lymphatic vessels (choice C). The submucosa (choice E) of the trachea is composed of loose connective tissue and is difficult to distinguish from the lamina propria in routine histological preparations. A thin layer of elastic tissue forms a boundary between the mucosa (choice D) and the submucosa. Left and right primary bronchi enter the lung through the hilum and divide into lobar (secondary) bronchi. Thus, there are two lobar bronchi in the left lung and three lobar bronchi in the right lung. Lobar bronchi then bifurcate into segmental (tertiary) bronchi, forming 8 segmental bronchi in the left lung and 10 segmental bronchi in the right lung. Each segmental bronchus and the lung parenchyma that it supplies constitute one bronchopulmonary segment. Keywords: Bronchi, bronchopulmonary segments 27 the answer is A: Bronchopulmonary segment. The lungs can be divided into lobes, and lobes are further divided into bronchopulmonary segments. The segments are pyramidal in shape, with their base at the pleural surface and their apex facing the hilum. Each segment is supplied by a segmental bronchus and a tertiary branch of the pulmonary artery. Each segment is drained by an intersegmental branch of the pulmonary veins that travel within septa that separate adjacent bronchopulmonary segments. Segments are the largest subdivisions of a pulmonary lobe and are, therefore, convenient anatomic structures for surgical resection. Pulmonary lobules (choice D) are subdivisions of bronchopulmonary segments, where each lobule is supplied by a separate bronchiole. A terminal bronchiole and its associated lung parenchyma together constitute a pulmonary acinus (choice B). The smallest functional unit of the lung, the respiratory bronchiolar unit (choice E), consists of a respiratory bronchiole and its associated pulmonary alveoli. Keywords: Bronchopulmonary segment, lung cancer 28 the answer is E: Presence of cartilage plates. The histologic features of extrapulmonary segments of the primary bronchi are similar to those of the trachea. However, once primary bronchi enter the lung and become intrapulmonary, their structure changes. Buy azigram with a mastercard. Testing Antimicrobial Activity and Cytotoxicity of Wound Care and Skin Cleanser.
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