Anatomy Lecture Notes PDF

Introduction Anatomy is the study of body structure, which includes size, shape, composition, and perhaps even coloration. Anatomy is directly related to physiology. There is relationship between anatomy, physiology, and pathophysiology. Physiology is the study of how the body functions. Pathophysio...

Introduction Anatomy is the study of body structure, which includes size, shape, composition, and perhaps even coloration. Anatomy is directly related to physiology. There is relationship between anatomy, physiology, and pathophysiology. Physiology is the study of how the body functions. Pathophysiology is the study of disorders of functioning. Anatomic Position of Body Parts and Areas When describing relative locations, the body is always assumed to be in anatomic position: standing upright facing forward, arms at the sides with palms forward, and the feet slightly apart. 1  Descriptive Terms for Body Parts and Areas Visualizing the Interior of the Body Today, however, several technologies and the extensive use of computers permit us to see the interior of the body without surgery.  Computed tomography (CT) scanning  Magnetic resonance imaging (MRI)  Positron emission tomography (PET) scanning 2 Imaging techniques. (A) CT scan of eye in lateral view showing a tumor (arrow) below the optic nerve. (B) MRI of midsagittal section of head. (C) PET scan of brain in transverse section (frontal lobes at top) showing glucose metabolism. Planes and Sections When internal anatomy is described, the body or an organ is often cut or sectioned in a specific way so as to make particular structures easily visible. A plane is an imaginary flat surface that separates two portions of the body or an organ. These planes and sections are:  Frontal (coronal) section—a plane from side to side separates the body into front and back portions.  Sagittal section—a plane from front to back separates the body into right and left portions. A midsagittal section creates equal right and left halves.  Transverse section—a horizontal plane separates the body into upper and lower portions.  Cross-section—a plane perpendicular to the long axis of an organ. A cross-section of the small intestine (which is a tube) would look like a circle with the cavity of the intestine in the center.  Longitudinal section—a plane along the long axis of an organ. Anatomy of Circulatory System The function of circulatory system is transport oxygen and nutrients to tissues and removes waste products. The Heart The primary function of the heart is to pump blood through the arteries, capillaries, and veins that keeps blood circulating properly. The heart is located in the thoracic cavity between the lungs. This area is called the mediastinum. The base of the cone-shaped heart is uppermost, behind the sternum, and the great vessels enter or leave here. The apex (tip) of the heart points downward and is just above the diaphragm to the left of the midline. 3 Pericardial Membranes The heart is enclosed in the pericardial membranes, of which there are three layers. The outermost is the fibrous pericardium, a loose fitting sac of strong fibrous connective tissue that extends inferiorly over the diaphragm and superiorly over the bases of the large vessels that enter and leave the heart. The serous pericardium is a folded membrane; the fold gives it two layers, parietal and visceral. Lining the fibrous pericardium is the parietal pericardium. On the surface of the heart muscle is the visceral pericardium, often called the epicardium. Between the parietal and visceral pericardial membranes is serous fluid, which prevents friction as the heart beats. Chambers and Valves of the Heart The walls of the four chambers of the heart are made of cardiac muscle called the myocardium. The chambers are lined with endocardium, simple squamous epithelium that also covers the valves of the heart and continues into the vessels as their lining (endothelium). The important physical characteristic of the endocardium is not its thinness, but rather its smoothness. This very smooth tissue prevents abnormal blood clotting, because clotting would be initiated by contact of blood with a rough surface. The upper chambers of the heart are the right and left atria (singular: atrium), which have relatively thin walls and are separated by a common wall of myocardium called the interatrial septum. The lower chambers are the right and left ventricles, which have thicker walls and are separated by the 4 interventricular septum. The atria receive blood, either from the body or the lungs, and the ventricles pump blood to either the lungs or the body. Right Atrium The two large caval veins return blood from the body to the right atrium. The superior vena cava carries blood from the upper body, and the inferior vena cava carries blood from the lower body. From the right atrium, blood will flow through the right atrioventricular (AV) valve, or tricuspid valve, into the right ventricle. The tricuspid valve is made of three flaps (or cusps) of endocardium reinforced with connective tissue. The general purpose of all valves in the circulatory system is to prevent backflow of blood. The specific purpose of the tricuspid valve is to prevent backflow of blood from the right ventricle to the right atrium when the right ventricle contracts. As the ventricle contracts, blood is forced behind the three valve flaps, forcing them upward and together to close the valve. Left Atrium The left atrium receives blood from the lungs, by way of four pulmonary veins. This blood will then flow into the left ventricle through the left atrioventricular (AV) valve, also called the mitral valve or bicuspid (two flaps) valve. The mitral valve prevents backflow of blood from the left ventricle to the left atrium when the left ventricle contracts. Right Ventricle When the right ventricle contracts, the tricuspid valve closes and the blood is pumped to the lungs through the pulmonary artery (or trunk). At the junction of this large artery and the right ventricle is the pulmonary semilunar valve (or more simply, pulmonary valve). Its three flaps are forced open when the right ventricle contracts and pumps blood into the pulmonary artery. When the right ventricle relaxes, blood tends to come back, but this fills the valve flaps and closes the pulmonary valve to prevent backflow of blood into the right ventricle. Projecting into the lower part of the right ventricle are columns of myocardium called papillary muscles. Strands of fibrous connective tissue, the chordae tendineae, extend from the papillary muscles to the flaps of the tricuspid valve. When the right ventricle contracts, the papillary muscles also contract and pull on the chordae tendineae to prevent inversion of the tricuspid valve. Left Ventricle The walls of the left ventricle are thicker than those of the right ventricle, which enables the left ventricle to contract more forcefully. The left ventricle pumps blood to the body through the aorta, the largest artery of the body. At the junction of the aorta and the left ventricle is the aortic semilunar valve (or 5 aortic valve). This valve is opened by the force of contraction of the left ventricle, which also closes the mitral valve. The aortic valve closes when the left ventricle relaxes, to prevent backflow of blood from the aorta to the left ventricle. When the mitral valve closes, it prevents backflow of blood to the left atrium; the flaps of the mitral valve are also anchored by chordae tendineae and papillary muscles. Also there is fibrous connective tissue called fibrous skeleton of the heart that anchors the outer edges of the valve flaps and keeps the valve openings from stretching. It also separates the myocardium of the atria from the ventricular myocardium and prevents the contraction of the atria from reaching the ventricles except by way of the normal conduction pathway. The fibrous connective tissue acts as electrical insulation between the two sets of chambers. The heart is really a double, or two-sided, pump. The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs to pick up oxygen and release carbon dioxide. The left side of the heart receives oxygenated blood from the lungs and pumps it to the body. Both pumps work simultaneously; that is, both atria contract together, followed by the contraction of both ventricles. 6 ANATOMY OF THE HEART 7