The distribution of the systematic arteries is like a highly ramified tree, the common trunk of which, formed by the aorta, commences at the left ventricle, while the smallest ramifications extend to the peripheral parts of the body and the contained organs. Arteries are found in all parts of the body, except in the hairs, nails, epidermis, cartilages, and cornea; the larger trunks usually occupy the most protected situations, running, in the limbs, along the flexor surface, where they are less exposed to injury. 1 There is considerable variation in the mode of division of the arteries: occasionally a short trunk subdivides into several branches at the same point, as may be observed in the celiac artery and the thyrocervical trunk: the vessel may give off several branches in succession, and still continue as the main trunk, as is seen in the arteries of the limbs; or the division may be dichotomous, as, for instance, when the aorta divides into the two common iliacs. 2 A branch of an artery is smaller than the trunk from which it arises; but if an artery divides into two branches, the combined sectional area of the two vessels is, in nearly every instance, somewhat greater than that of the trunk; and the combined sectional area of all the arterial branches greatly exceeds that of the aorta; so that the arteries collectively may be regarded as a cone, the apex of which corresponds to the aorta, and the base to the capillary system. 3 The arteries, in their distribution, communicate with one another, forming what are called anastomoses, and these communications are very free between the large as well as between the smaller branches. The anastomosis between trunks of equal size is found where great activity of the circulation is requisite, as in the brain; here the two vertebral arteries unite to form the basilar, and the two anterior cerebral arteries are connected by a short communicating trunk; it is also found in the abdomen, where the intestinal arteries have very ample anastomoses between their larger branches. In the limbs the anastomoses are most numerous and of largest size around the joints, the branches of an artery above uniting with branches from the vessels below. These anastomoses are of considerable interest to the surgeon, as it is by their enlargement that a collateral circulation is established after the application of a ligature to an artery. The smaller branches of arteries anastomose more frequently than the larger; and between the smallest twigs these anastomoses become so numerous as to constitute a close network that pervades nearly every tissue of the body. 4 Throughout the body generally the larger arterial branches pursue a fairly straight course, but in certain situations they are tortuous. Thus the external maxillary artery in its course over the face, and the arteries of the lips, are extremely tortuous to accommodate themselves to the movements of the parts. The uterine arteries are also tortuous, to accommodate themselves to the increase of size which the uterus undergoes during pregnancy.
All the tissues and organs of the body originate from a microscopic structure (the fertilized ovum), which consists of a soft jelly-like material enclosed in a membrane and containing a vesicle or small spherical body inside which are one or more denser spots. This may be regarded as a complete cell. All the solid tissues consist largely of cells essentially similar to it in nature but differing in external form. 4 In the higher organisms a cell may be defined as “a nucleated mass of protoplasm of microscopic size.” Its two essentials, therefore, are: a soft jelly-like material, similar to that found in the ovum, and usually styled cytoplasm, and a small spherical body imbedded in it, and termed a nucleus. Some of the unicellular protozoa contain no nuclei but granular particles which, like true nuclei, stain with basic dyes. The other constituents of the ovum, viz., its limiting membrane and the denser spot contained in the nucleus, called the nucleolus, are not essential to the type cell, and in fact many cells exist without them. 5 Cytoplasm (protoplasm) is a material probably of variable constitution during life, but yielding on its disintegration bodies chiefly of proteid nature. Lecithin and cholesterin are constantly found in it, as well as inorganic salts, chief among which are the phosphates and chlorides of potassium, sodium, and calcium. It is of a semifluid, viscid consistence, and probably colloidal in nature. The living cytoplasm appears to consist of a homogeneous and structureless ground-substance in which are embedded granules of various types. The mitochondria are the most constant type of granule and vary in form from granules to rods and threads. Their function is unknown. Some of the granules are proteid in nature and probably essential constituents; others are fat, glycogen, or pigment granules, and are regarded as adventitious material taken in from without, and hence are styled cell-inclusions or paraplasm. When, however, cells have been “fixed” by reagents a fibrillar or granular appearance can often be made out under a high power of the microscope. The fibrils are usually arranged in a network or reticulum, to which the term spongioplasm is applied, the clear substance in the meshes being termed hyaloplasm. The size and shape of the meshes of the spongioplasm vary in different cells and in different parts of the same cell. The relative amounts of spongioplasm and hyaloplasm also vary in different cells, the latter preponderating in the young cell and the former increasing at the expense of the hyaloplasm as the cell grows. Such appearances in fixed cells are no indication whatsoever of the existence of similar structures in the living, although there must have been something in the living cell to give rise to the fixed structures. The peripheral layer of a cell is in all cases modified, either by the formation of a definite cell membrane as in the ovum, or more frequently in the case of animal cells, by a transformation, probably chemical in nature, which is only recognizable by the fact that the surface of the cell behaves as a semipermeable membrane.
In physiology, respiration is defined as the movement of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction.
The physiological definition of respiration should not be confused with the biochemical definition, which refers to cellular respiration, a metabolic process by which an organism obtains energy (in the form of ATP) by oxidizing nutrients and releasing waste products. Although physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the bulk flow and transport of metabolites between the organism and the external environment.
Gaseous exchange (which in organisms with lungs is called ventilation and includes inhalation and exhalation) is a part of physiologic respiration. Thus, in precise usage, the words breathing and ventilation are hyponyms, not synonyms, of respiration; but this prescription is not consistently followed, even by most health care providers, because the term respiratory rate (RR) is a well-established term in health care, even though it would need to be consistently replaced with ventilation rate if the precise usage were to be followed.
Q.1. Explain the characteristics of living organisms. Ans: Characteristics of living organisms are as follows: i. Growth: All living organisms exhibit growth. In living organisms growth is from inside, whereas in non-living organisms growth occurs due to accumulation of material on the surface. ii. Reproduction: Organisms reproduce asexually or sexually and produce their own kind. iii. Metabolism: Various biochemical reactions occur inside all living organisms. The sum total of all the reactions occuring in the body of an organism is called metabolism. iv. Cellular organization: Cell is the basic unit of life. All living organisms show cellular organization. v. Ability to sense and respond: All living organisms have ability to respond to the stimulus. Consciousness, is thus, one of the characteristics of living organisms.
Q.2. Why growth and reproduction cannot be the defining characteristics of living organisms? Ans: i. Growth is also exhibited by non-living objects. It is by accumulation of material on the surface. Thus, it cannot be taken as the defining property of living organisms. ii. Living organisms like mules, sterile worker bees, infertile human couples, etc. cannot reproduce. Thus, reproduction also cannot be the defining character of living organisms. 1.1 Diversity in living organisms.
Q.3. Explain diversity in living organisms. Ans: i. There are various types of living organisms existing on the earth, ranging from unicellular microscopic organisms to large multicellular plants and animals. ii. Some of them are prokaryotic in nature, while some are eukaryotes. iii. There are about 5 − 30 million species of plants and animals on earth. iv. They exhibit a great deal of variation in shape, size, structure, mode of nutrition, mode of reproduction, etc. v. They live or grow in different climatic conditions.
Q.4. Why are living organisms classified? Ans: Living organisms are classified due to following reasons: i. Study of fossils ii. Study of organisms of different areas iii. For easy identification iv. Grouping based on the similarities and differences v. Evolution of various taxon, etc.
The heart functions as a pump and acts as a double pump in the cardiovascular system to provide a continuous circulation of blood throughout the body. This circulation includes the systemic circulation and the pulmonary circulation. Both circuits transport blood but they can also be seen in terms of the gases they carry. The pulmonary circulation collects oxygen from the lungs and delivers carbon dioxide for exhalation.The systemic circuit transports oxygen to the body and returns relatively deoxygenated blood and carbon dioxide to the pulmonary circuit.
Chest Pain Chest pain is a common symptom and may be a manifestation of cardiovascular or noncardiovascular disease. Full characterization of the pain with regard to quality (squeezing, tightening, pressing, burning), quantity, frequency, location, duration, radiation, aggravating or alleviating factors and associated symptoms can help to distinguish the cause. All patients presenting to a hospital with severe or persistent chest pain should have a full set of vital signs, an ECG, and a CXR. **The life-threatening causes that must be considered and ruled out in all patients with severe, persistent chest pain. Cardiac Causes Angina/Myocardial infarction ** Substernal pressure +/- radiation to neck, jaw, Left arm Duration usually > 1 minute and < 12 hours for angina Associated with dyspnea, diaphoresis, nausea/vomiting Worsened with exertion, relieved with rest or nitroglycerin Infarction is same as angina except increased intensity and duration ECG: look for ST elevations or depressions, T wave inversions Pericarditis/Myocarditis ** Sharp pain radiation to trapezius Aggravated by respiration, relieved by sitting forward Listen for pericardial friction rub ECG: look for diffuse ST elevations and PR depressions Aortic Dissection ** Sudden onset of tearing chest pain, knife-life pain Radiation to back Usually severely hypertensive (can become hypotensive) Asymmetric blood pressure in arms and asymmetric pulses bilaterally Widened mediastinum on CXR, new aortic insufficiency murmur Pulmonary Causes Pneumonia ** A very common cause of chest pain in our settings Pleuritic in nature Associated with dyspnea, cough, fever, sputum production Presents with fever, tachycardia, crackles on physical exam CXR should show an infiltrate Pneumothorax ** Sharp, pleuritic pain +/- shortness of breath Unilateral hyperresonance and decrease
Congestive Cardiac Failure (CCF) A complex syndrome caused by a structural or functional abnormality in the cardiac muscle that impairs its ability to function as a pump and meet the metabolic needs of the body. Characterized by shortness of breath, fatigue and signs of fluid retention. Decreased cardiac output triggers the baroreceptors in the the LV, carotid sinus and the aortic arch . This leads to stimulation of the cardio-respiratory centre in the brains, increased ADH release (causing peripheral vasoconstriction and increases renal salt and water absorption) and increased sympathetic stimulation (activating renin – angiotension system, promoting more water retention and peripheral vasoconstriction). These lead to LV dilatation and hypertrophy (poor ejection fraction), increased peripheral vascular resistance (high afterload) and retention of fluid( high preload). Most patients present with left heart failure which can progresses to right heart failure. The most common cause of right heart failure is left heart failure but it can also be caused by pulmonary hypertension (cor pulmonale) or disease that effect the RV>LF (like EMF). Heart failure can be either compensated (when the patient is stable) or decompensated (when the patient suddenly gets worse) Etiology of CHF Systolic Dysfunction (inability to expel blood) Hypertension* Ischemic heart disease Idiopathic cardiomyopathy (like HIV)* Valvular disease* Alcoholic cardiomyopathy Drug-associated cardiomyopathy Myocarditis * The most common causes in our setting Diastolic Dysfunction (abnormal filling) Hypertension Fibrosis Ischemia Aging process Constrictive pericarditis (like TB)* Restrictive pericarditis (like EMF)* Hypertrophic cardiomyopathy
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