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Combustible Celluloid
 

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By K. Hassan. Concordia College, Bronxville, New York.

Normally the visceral and parietal layers are very close together buy protonix 20 mg with mastercard, but fluid may accumulate in the region between them discount 20 mg protonix mastercard, the pericardial cavity, under certain disease conditions. THE HEART AND HEART DISEASE ✦ 285 Table 14•1 Layers of the Heart Wall LAYER LOCATION DESCRIPTION FUNCTION Endocardium Innermost layer of the Thin, smooth layer of epithelial Lines the interior of the chambers and heart wall cells covers the heart valves Myocardium Middle layer of the heart Thick layer of cardiac muscle Contracts to pump blood into the arteries wall Epicardium Outermost layer of the Thin serous membrane Covers the heart and forms the visceral heart wall layer of the serous pericardium Heart wall Epicardium (visceral pericardium) Myocardium Endocardium 14 Visceral pericardium Pericardial cavity Serous pericardium Parietal pericardium Fibrous pericardium Figure 14-2 Layers of the heart wall and pericardium. Table 14•2 Layers of the Pericardium LAYER LOCATION DESCRIPTION FUNCTION Fibrous pericardium Outermost layer Fibrous sac Encloses and protects the heart; anchors heart to surrounding structures Serous pericardium Between the fibrous Doubled membranous sac with fluid Fluid reduces friction within the pericardium and the between layers pericardium as the heart functions myocardium Parietal layer Lines the fibrous Serous membrane Forms the outer layer of the serous pericardium pericardium Visceral layer Surface of the heart Serous membrane Forms the inner layer of the serous pericardium; also called the epi- cardium 286 ✦ CHAPTER FOURTEEN the human heart is really a double pump (Fig. The superior vena cava brings blood Special Features of the Myocardium Head and arms Cardiac muscle cells are lightly stri- Superior Left ated (striped) based on alternating vena cava pulmonary actin and myosin filaments, as seen in artery skeletal muscle cells (see Chapter 8). These intercalated (in-TER- atrium cah-la-ted) disks are actually modified Left plasma membranes that firmly attach atrium adjacent cells to each other but allow for rapid transfer of electrical impulses Left between them. The right side of the heart pumps blood through the pulmonary circuit to the lungs to be oxygenated; the left side of the heart Healthcare professionals often refer to pumps blood through the systemic circuit to all other parts of the body. THE HEART AND HEART DISEASE ✦ 287 Brachiocephalic artery Left common carotid artery Pulmonary valve Left subclavian artery Superior vena cava Aortic arch Pulmonary trunk Right pulmonary Left pulmonary artery artery (branches) (branches) Ascending Left aorta pulmonary Right veins pulmonary Left atrium veins Aortic valve Left AV Right (mitral) atrium valve Right AV (tricuspid) Left valve ventricle Right ventricle 14 Inferior vena cava Endocardium Apex Blood high in oxygen Myocardium Interventricular Epicardium Blood low in oxygen septum Figure 14-5 The heart and great vessels. A third vessel large pulmonary trunk, which then divides into right that opens into the right atrium brings blood from the and left pulmonary arteries, which branch to the heart muscle itself, as described later in this chapter. Note that the pulmonary arteries Table 14•3 Chambers of the Heart CHAMBER LOCATION FUNCTION Right atrium Upper right chamber Receives blood from the vena cavae and the coronary sinus; pumps blood into the right ventricle Right ventricle Lower right chamber Receives blood from the right atrium and pumps blood into the pulmonary artery, which carries blood to the lungs to be oxygenated Left atrium Upper left chamber Receives oxygenated blood coming back to the heart from the lungs in the pulmonary veins; pumps blood into the left ventricle Left ventricle Lower left chamber Receives blood from the left atrium and pumps blood into the aorta to be carried to tissues in the systemic circuit 288 ✦ CHAPTER FOURTEEN in Figure 14-5 are colored blue because they are car- Four Valves One-way valves that direct blood flow rying deoxygenated blood, unlike other arteries, through the heart are located at the entrance and exit of which carry oxygenated blood. The exit valves are the semilunar (sem-e- red because they are carrying oxygenated blood, un- LU-nar) valves, so named because each flap of these like other veins, which carry deoxygenated blood. This blood goes first into the aorta (a-OR- ◗ The right atrioventricular (AV) valve is also known as tah), the largest artery, and then into the branching the tricuspid (tri-KUS-pid) valve because it has three systemic arteries that take blood to the tissues. The cusps close when the left ventricle begins to POSTERIOR POSTERIOR Chordae Left AV Cusps of Right AV tendineae valve open right AV valve closed valve Left AV valve closed Aortic Cusps of valve left AV Right AV closed valve valve open Coronary artery Cusps of aortic valve Coronary Cusps of Pulmonary Aortic valve Pulmonary artery pulmonary valve valve closed open valve open ANTERIOR ANTERIOR A Relaxation phase (diastole) B Contraction phase (systole) Figure 14-6 Valves of the heart (superior view from anterior, atria removed). THE HEART AND HEART DISEASE ✦ 289 Table 14•4 Valves of the Heart VALVE LOCATION DESCRIPTION FUNCTION Right AV valve Between the right atrium Valve with three cusps; tricuspid valve Prevents blood from flowing back and right ventricle up into the right atrium when the right ventricle contracts (systole) Left AV valve Between the left atrium Valve with two cusps; bicuspid or mi- Prevents blood from flowing back and left ventricle tral valve up into the left atrium when the left ventricle contracts (systole) Pulmonary semi- At the entrance to the Valve with three half-moon shaped Prevents blood from flowing back lunar valve pulmonary artery cusps into the right ventricle when the right ventricle relaxes (diastole) At the entrance to the Valve with three half-moon shaped Prevents blood from flowing back Aortic semilunar aorta cusps into the left ventricle when the valve left ventricle relaxes (diastole) contract; this closure prevents blood from returning to the left atrium and ensures the forward flow of blood into the aorta. The higher pressure in the pulmonary artery, described as Right ventricle Left ventricle back pressure, closes the valve and prevents blood from returning to the Inferior vena cava ventricle. Blood from the systemic circuit pressure closes the aortic valve and enters the right atrium (1) through the superior and inferior venae cavae, flows through the right AV (tricuspid) valve (2), and enters the right ventricle (3). Blood returns from the lungs in the pulmonary veins, enters the left atrium (5), and Figure 14-7 traces a drop of blood flows through the left AV (mitral) valve (6) into the left ventricle (7). This active phase is called systole (SIS-to- Only the endocardium comes into contact with the blood le), and in each case, it is followed by a resting period that flows through the heart chambers. One complete sequence of myocardium must have its own blood vessels to provide heart contraction and relaxation is called the cardiac cycle oxygen and nourishment and to remove waste products. The main arteries that supply The contraction phase of the cardiac cycle begins with blood to the muscle of the heart are the right and left contraction of both atria, which forces blood through the coronary arteries (Fig. They receive blood when the heart relaxes be- Atrial contraction is completed at the time ventricular cause the aortic valve must be closed to expose the en- contraction begins. After passing through gins in the atria at the same time that a contraction (sys- capillaries in the myocardium, blood drains into a system tole) begins in the ventricles. Although both upper and lower chambers Superior Superior Aortic arch vena cava vena cava Left pulmonary Right artery pulmonary Left veins Left atrium pulmonary Right veins atrium Right Great Inferior atrium cardiac vena vein cava Right coronary Left Coronary artery coronary sinus artery Small cardiac Left vein Right ventricle ventricle Right ventricle A Anterior B Posterior Figure 14-8 Blood vessels that supply the myocardium. THE HEART AND HEART DISEASE ✦ 291 When the ventricle relaxes, backflow of Blood flow blood closes valve and causes filling of Right Left coronary arteries coronary coronary artery artery Pulmonary valve To heart muscle (myocardium) Right AV Aortic Left AV A Ventricular contraction B Ventricular relaxation valve valve valve (aortic valve open) (aortic valve closed) Figure 14-9 Opening of coronary arteries in the aortic valve (anterior view). It is the prod- uct of the stroke volume (SV)—the volume of blood A unique property of heart muscle is its ability to adjust the ejected from the ventricle with each beat—and the heart strength of contraction to the amount of blood received. Thus, as CO HR SV Diastole Atrial systole Ventricular systole Atria fill with blood, which begins to Contraction of atria pumps blood into Contraction of ventricles pumps flow into ventricles as soon as their the ventricles.

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Multiple agencies and organiza- account for only a small portion of craniosynostosis generic 20mg protonix amex. The OTHER identification of the FGFR genes that cause Pfeiffer (and Our child was just diagnosed with Craniosynostosis—What do other) craniosynostosis syndromes has promoted we do now? Craniosynostosis and Parents research into the underlying process that causes Pfeiffer Support purchase protonix 40 mg on line, Inc. It will be another enormous challenge to go My child looks different: a guide for parents. In rare situations, the patient may experience Craniosynostosis and Parents Support, Inc. PO Box 11082, after the drug is given, so a person may have a pharma- Chattanooga, TN 37401. PO Box 515838, 7777 Forest otherwise in excellent health and has no family history of Lane, Ste C-621, Dallas, TX 75251-5838. WEBSITES Unexpectedly, there is a significant increase in body tem- Craniofacial Anomalies. Pediatric Surgery, perature, and the patient experiences sustained muscle Columbia University. Once diagnosed with malignant hyperthermia, it variations (poor, intermediate, extensive, and ultra) that is quite easy to avoid future episodes by simply using a result in different clinical phenotypes with respect to different type of anesthetic when surgery is necessary, drug metabolism. For example, a poor metabolizer has but it often takes one negative, and potentially life-threat- difficulty converting the therapeutic drug into a useable ening, experience to know the condition exists. To prevent this An incident that occurred in the 1950s further shows from happening, the prescribed dosage of the drug must the diversity of pharmacogenetic disorders. Korean War, service personnel were deployed in a region of the world where they were at increased risk for An ultra metabolizer, on the other hand, shows malaria. To reduce the likelihood of acquiring that dis- exceedingly rapid breakdown of the drug to the point that ease, the antimalarial drug primaquine was administered the substance may be destroyed so quickly that therapeu- prophylactically. Shortly thereafter, approximately 10% tic levels may not be reached, and the patient may there- of the African-American servicemen were diagnosed fore never show any benefit from treatment. In these with acute anemia and a smaller percentage of soldiers of cases, switching to another type of drug that is not asso- Mediterranean ancestry showed a more severe hemolytic ciated with CYP2D6 metabolism may prove more bene- anemia. Functional G6PD is important in ers, is less extreme than the ultra metabolism category, the maintenance of a balance between oxidized and but nevertheless presents a relatively rapid turnover of reduced molecules in the cells, and, under normal cir- drug that may require a higher than normal dosage to cumstances, a mutation that eliminates the normal maintain a proper level within the cells. And, finally, the enzyme function can be compensated for by other cellu- intermediate phenotype falls between the poor and exten- lar processes. However, mutation carriers are compro- sive categories and gives reasonable metabolism and mised when their cells are stressed, such as when the turnover of the drug. Clearly, both the medics who bolic classes has clearly shown that the usual “one size administered the primaquine and the men who took the fits all” recommended drug dose is not appropriate for all drug were unaware of the potential consequences. Research efforts Drugs are essential to modern medical practice, but, Future applications as in the cases of malignant hyperthermia and G6PD At the present time, pharmacogenetics is still in its deficiency, it has become clear that not all individuals infancy with its full potential yet to be realized. Reactions can vary from current studies, it is possible to envision many different positive improvement in the quality of life to life threat- applications in the future. New tests will be developed to research endeavors are now providing information that is monitor the effects of drugs, and new medications will be allowing a better understanding of the underlying causes found that will specifically target a particular genetic of pharmacogenetic anomalies with the hope that eventu- abnormality.

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Slomski purchase 20 mg protonix amex, PhD Humans have 46 chromosomes—22 pairs of autoso- mal chromosomes and one pair of sex chromosomes purchase protonix 20 mg with amex. These chromosomes may be examined by constructing a karyotype, or organized depiction, of the chromosomes. To construct a karyotype, a technician stops cell division just after the chromosomes have replicated and con- IChromosomal abnormalities densed using a chemical, such as colchicine. The chro- Chromosomal abnormalities describe changes in the mosomes are visible within the nucleus at this point. The normal number of chromosomes or structural problems image of the chromosomes seen through the microscope within the chromosomes themselves. Each chromosome is cut out of the pic- ties occur when an egg or sperm with an incorrect num- ture, and arranged on another sheet in the correct ber of chromosomes, or a structurally faulty sequence and orientation. The chromosome pairs are chromosome, unites with a normal egg or sperm during identified according to size, shape, and characteristic conception. In this case, the zygote, the cell formed during conception that eventually develops into Normal cell division an embryo, divides incorrectly. In most animals, two types of cell division take Chromosomal abnormalities can cause serious men- place: mitosis and meiosis. Compared to with Down syndrome are mentally retarded and may its parent chromosome, each daughter cell has exactly the have a host of physical abnormalities, including heart same number of chromosomes and identical genes. Other individuals, called Down syndrome preservation of chromosome number and structure is mosaics, have a mixture of normal cells and cells with accomplished through the replication of the entire set of three copies of chromosome 21, resulting in a milder chromosomes just before mitosis. Zygotes that Sex cells, such as eggs and sperm, undergo a differ- receive a full extra set of chromosomes, a condition ent type of cell division called meiosis. This reduction in the number of chromosomes within sex cells is accomplished during two rounds of cell division, called meiosis I and meiosis II. During meiosis I, a cell with 46 replicated chromosomes divides to form two cells that each contain 23 replicated chromosomes. Normally, the meiosis I division separates the 23 pairs of chromo- somes evenly, so that each daughter cell contains one chromosome from each chromosome pair. During meiosis II, the two daughter cells containing 23 replicated chro- mosomes divide to form four daughter cells, each con- taining 23 non-replicated chromosomes. Chromosome pairs may fail to separate during meiosis I, or a replicated chromosome may fail to separate during meiosis II. Meiosis produces four daughter cells, each with half the normal number of chromosomes. Non-sex cells in humans are called diploid (meaning “double the number”) since they contain the full number of normal chromosomes. Human diploid cells normally each have 46 chromosomes, and haploid cells normally each have 23 chromosomes. Alterations in chromosome number Two kinds of chromosome number alterations can occur in humans: aneuploidy, an abnormal number of chromosomes, and polyploidy, more than two complete sets of chromosomes. During normal meiosis, chromosomes are distributed evenly among the four daughter cells. Sometimes, however, an uneven number of chromosomes are distributed to the daughter cells.

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