Short hypertension questions buy line terazosin, branching intercalated ducts-the initial part of the excretory duct system- drain acini and are lined by a low simple cuboidal epithelium (A) blood pressure of 1200 discount terazosin online amex. Longer intralobular ducts are lined by simple cuboidal epithelium consisting of more plump cells (B) blood pressure 80 over 50 cheap terazosin 5 mg online. Larger interlobular ducts are lined by simple cuboidal epithelium invested by dense fibrous connective tissue (C). Interlobular ducts, in turn, drain directly into the main pancreatic ducts, which deliver secretions to the duodenum. Secretory cells of acini are intensely eosinophilic, have basal nuclei, and produce digestive enzymes. Pale cells in the richly vascularized islets constitute the endocrine part of the gland. They lead into small intralobular intercalated ducts that are lined by one layer of low cuboidal epithelial cells. Intercalated ducts lead into larger interlobular ducts outside the lobules and lined by simple cuboidal to low columnar epithelium. Interlobular ducts branch extensively, get larger, and empty into two main excretory ducts. The smaller accessory pancreatic duct receives branches from the pancreatic head; it communicates with the main duct and opens about 2 cm above it. Both ducts are lined by simple columnar epithelium, surrounded by a layer of connective tissue. Small mucous glands open into the larger ducts and lubricate and protect the lining epithelium. The endocrine part of the pancreas-islets of Langerhans-secretes primarily insulin and glucagon. The dark acinar cells surround a small central lumen and have apical zymogen granules. Their apical cytoplasm appears granular and intensely eosinophilic; their bases stain darker. Each oval- to flask-shaped acinus consists of one layer of cuboidal to pyramidal cells around a central lumen. Each single, spheroid nucleus sits toward the basal part of the cell in the area with the most intense cytoplasmic basophilia. Apical parts of cells are filled with prominent secretory (zymogen) granules that stain intensely with eosin or acid dyes. Acinar cells synthesize and secrete a host of digestive enzymes or their inactive precursors, including trypsin, chymotrypsin, amylase, lipase, and carboxypeptidase. A unique feature of acini is the presence of initial parts of the excretory duct system, composed of centroacinar cells, which partially protrude 14. Centroacinar cells lead into intercalated ducts lined by simple cuboidal epithelium. Pancreatic acinar cells are normally protected from harmful effects of digestive enzymes that they secrete. However, acinar cell injury or pancreatic duct obstruction may lead to inappropriate extracellular leakage of activated digestive enzymes and autodigestion of pancreatic acini.
The combination of a single motor neuron and all the muscle fibers it innervates is called a motor unit you buy terazosin without a prescription. Although the muscle fibers of a given motor unit tend to be located near one another pulse pressure variation values discount 5 mg terazosin mastercard, motor units have overlapping territories blood pressure medication effects purchase cheap terazosin line. The strength of muscle contraction depends on the number of muscle fibers active at the same time. The degree of control that can be exerted on the strength of contraction depends on the number of muscle fibers in a motor unit. Motor units of large muscles such as the gastrocnemius, which exert a great deal of power, may contain more than 2,000 muscle fibers. Motor units of small muscles such as the extraocular muscles, which exert very fine control but not much power, may contain as few as six muscle fibers. In general, small motor neurons innervate fewer muscle fibers (they have smaller motor units). Small motor neurons are also more easily activated by synaptic inputs than are large motor neurons. Therefore, when signals from the brain initiate a movement, the smallest motor neurons and motor units are usually activated first. If only a small fine movement is required, the smallest motor units alone can be activated. As more power and less fine control is needed, the larger motor units are progressively recruited. The mechanical properties of the muscle fibers are also matched to the size of their motor unit. Because the muscle fibers of the smallest motor units are those most often activated, they must be relatively resistant to fatigue (see Plate 2-15). The terminals, although unmyelinated, are invested by a Schwann cell, which projects finger-like processes between the membranes of the nerve and the muscle. The nerve terminal lies in a trough within the muscle fiber membrane (sarcolemma); it is rich in mitochondria and contains numerous synaptic vesicles about 50 nm in diameter. These vesicles, which contain the neurotransmitter acetylcholine, are clustered around nipple-shaped active zones located at regular intervals along the terminal membrane. Acetylcholine is released by exocytosis of vesicles lying adjacent to both sides of the active zone. The presynaptic and postsynaptic membranes are separated by a space approximately 50 nm wide. Freeze-fracture electron microscopy reveals granular structures embedded in the postsynaptic membrane. These structures, which are concentrated on the banks of the junctional folds opposite the sites of acetylcholine release, are acetylcholine receptors that mediate the action of the transmitter. They are sparse in regions of the sarcolemma not close to the neuromuscular junction. The muscle fiber is surrounded by a connective tissue basement membrane that continues into the synaptic cleft, sending extensions into the junctional folds. It also contains other important molecules that help guide the growth of the nerve terminal during development and regeneration, determine the locations of the presynaptic active zones, and induce the clumping of acetylcholine receptors opposite the synaptic vesicle. The membrane of the nerve terminal has a different assortment of ion channels: fewer sodium channels, several types of potassium channels, and, most important, voltage-dependent calcium channels. When an action potential arrives at the nerve terminal, it opens the calcium channels and calcium ions move from the extracellular fluid, where the concentration is about 2. The sudden increase in intraterminal concentration of calcium ions is linked to the release of acetylcholine by exocytosis at the synaptic vesicle release sites. The acetylcholine binds to receptor molecules on the postsynaptic membrane, opening channels that permit the influx of sodium ions and efflux of potassium ions.
It is estimated that more than 95% o patients who have gout are urate underexcretors (see Section 3 pulse pressure equivalent purchase terazosin 5 mg online. It is also not known why hypertriglyceridemia (see Chapter 28) pulse pressure physiology cheap terazosin 5 mg fast delivery, hypertension blood pressure higher at night buy on line terazosin, and the metabolic syndrome (see Chapter 39) are associated with impaired uric acid excretion. Acute gouty arthritis is due to joint in ammation in response to the presence o sodium urate. Urate-lowering therapy may involve inhibitors o xanthine dehydrogenase, drugs that increase the excretion o urate in the kidneys, and recombinant uric acid oxidase to destroy urate in the blood. Decreased glomerular ltration in patients with advanced chronic renal ailure and in patients who have lead poisoning. Inhibition o the excretion o uric acid into the kidney tubules by organic acids. Perhaps as little as 1% o all patients who have gout are urate overproducers (see Section 3. Ge ne ral Co mme nts Abo ut Go ut The term gout is sometimes used in re erence to uratedependent joint in ammation only, and sometimes in re erence to both joint in ammation and ormation o kidney stones. Joint in ammation stems rom sodium urate crystals in joints that occasionally give rise to a highly pain ul in ammatory reaction, an acute gouty arthritis. Nephrolithiasis (presence o kidney stones) is due to the aggregation o crystals o uric acid or, rarely, sodium urate in the urine. Another orm o nephropathy, although uncommon, results rom crystallization o sodium urate in the hyperosmolar interstitial uid o the renal medulla. Both nephropathy (related to uric acid or sodium urate) and arthritis are usually preceded by months to years o symptom- ree hyperuricemia. During their lives, patients who have symptomatic hyperuricemia may present with acute gouty arthritis, nephrolithiasis, or both. However, during a single, pain ul episode, patients usually present only with arthritis or with nephrolithiasis. Adult men have the highest concentration o urate in their blood or the longest time during their lives. I gout is present in a child or premenopausal woman, it may be due to a metabolic disease. Increased tissue turnover due to one o the ollowing: obesity, psoriasis (see Chapter 37), leukemia, lymphoma, hemolytic anemias, sickle cell disease and thalassemia (see Chapter 17), polycythemia vera, hemorrhage, in ection, trauma, or cytolytic therapy. A P-consuming utile cycles in patients who have a de ciency in the gluconeogenic pathway, such as glucose 6-phosphatase de ciency or ructose bisphosphatase de ciency (see Chapter 25). Ac ute Go uty Arthritis Acute gouty arthritis is the most common presentation o symptomatic, long-term hyperuricemia. The higher Gout and Other Dis eas es Related to the Metabolis m of Purine Nucleotides 435. The s odium urate depos its are likely accompanied by repeated epis odes of acute gouty arthritis and als o by the eros ion of nearby bone that can des troy a joint. Such crystals occasionally give rise to a very pain ul, acute in ammation called acute gouty arthritis. The in ammation typically af ects a single joint, usually o the lower extremity, and most commonly the metatarsophalangeal joint. The diagnosis o an acute gouty attack o en relies on aspirating uid rom the af ected joint and nding negatively bire ringent crystals under a polarizing microscope. I the compensator is oriented parallel to the crystals, the crystals appear yellow; i it is perpendicular to the crystals, they appear blue. The method allows crystals o sodium urate to be distinguished rom crystals o calcium pyrophosphate, which are the cause o pseudogout. The joint in ammation is sel -limiting and, in the absence o treatment, resolves by itsel within hours to weeks.
Cartilage provides structural support for soft tissues and a sliding area for joints and allows for growth in long bone length hypertension nos definition buy terazosin 1 mg low price. Cartilage performs diverse and varied functions hypertension 95th percentile buy cheap terazosin 1mg on line, but it lacks attributes of most other tissues: it is avascular and has no nerve or lymphatic supply blood pressure 8850 buy terazosin 1mg with visa. Bone is the calcified component of the skeleton, which in the human comprises 206 individual bones. The matrix of bone, as a rigid connective tissue, consists of collagen embedded in a ground substance on which is deposited a complex inorganic mineral, hydroxyapatite. As a tissue, compared with cartilage, bone has a higher metabolic rate, is richly vascularized, and receives up to 10% of cardiac output. Bone has good regenerative potential for self-repair throughout life, whereas cartilage has a very limited capacity for regeneration in response to traumatic injury or disease. Articular cartilage has a complex internal structure, as well as sharing features with other types of hyaline cartilage. Of its four poorly demarcated zones, the most superficial, uppermost zone forms the gliding surface and is in contact with the synovial cavity (*) of the joint. Small round chondrocytes (C) are oriented parallel to the surface; chondrocytes in deeper zones are larger, more rounded, and arranged in vertical columns. The term chondron encompasses the chondrocyte and its pericellular and territorial matrix. Lacking a perichondrium, articular cartilage is a variant of hyaline cartilage found elsewhere. Hyaline cartilage, the most common and characteristic type, has a matrix with a translucent, glassy appearance because the refractive index of its collagen is similar to that of the ground substance in which it is embedded. In the fetus, hyaline cartilage forms a provisional skeleton, which is replaced by bone during endochondral bone formation. Soon after birth and up to adolescence, hyaline cartilage is an integral component of epiphyseal growth plates, which control the growth and shape of long bones. In addition, hyaline cartilage lines articular surfaces of synovial joints, where it acts as a self-lubricating shock absorber with low friction properties. Hyaline cartilage also provides semirigid support to walls of some respiratory airways. Damaged hyaline cartilage is unable to be repaired because in the adult its cells-chondrocytes-cannot undergo mitosis. Elastic cartilage contains chondrocytes embedded in a matrix dominated by elastic fibers. Firm but flexible, it contributes structural integ- rity to the auricle of the ear, epiglottis, and eustachian (auditory) tube and allows bending. Fibrocartilage has great tensile strength because of the number of collagen fibers in its matrix. It attaches bone to tendon and, because it has load-distributing properties, it is found in menisci of synovial joints and in intervertebral discs. It is primarily a disease of articular cartilage, its hallmarks being extracellular matrix degradation and altered chondrocyte metabolism. The disorder is associated with decreased glycosaminoglycan content of the matrix accompanied by increased water content. Loss of cartilage leads to bone-on-bone contact in synovial joints with rapid deterioration of movement and function.
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