Circulatory System PDF

Histology of Circulatory System  Cardiovascular System The circulatory system or the cardiovascular system consists of the heart, blood vessels, and the about five litters of blood, that the blood vessels are transport. Blood is responsible for transporting O2, n...

Histology of Circulatory System  Cardiovascular System The circulatory system or the cardiovascular system consists of the heart, blood vessels, and the about five litters of blood, that the blood vessels are transport. Blood is responsible for transporting O2, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the heart.  The Heart It is a muscular organ, that is located in the thoracic region. The bottom tip of the heart, known as its apex, is turned to the left side of the body. The top of the heart, known as the heart’s base, it connects to the great blood vessels of the body: the aorta, vena cava, pulmonary trunk, and pulmonary veins.  Circulatory Loops 1- Pulmonary circulation 2- Systemic circulation In the human body, there are two circulation loops: Pulmonary circulation: It transports deoxygenated blood from the right side of the heart to the lungs, the right atrium and right ventricle are the parts of heart that support the pulmonary circulation loop. Through this circulation, the blood will be oxygenated, and then returns back to the left side of the heart.  Systemic circulation carries oxygenated blood from the left side of the heart (with the exception of the heart and lungs). Systemic circulation removes wastes from body tissues and returns deoxygenated blood to the right side of the heart. The left atrium and left ventricle of the heart are the pumping chambers for the systemic circulation loop.  Coronary Circulation A set of blood vessels that provide the myocardium with the oxygen and nutrients. The left and right coronary arteries branch off from the aorta and provide blood to the left and right sides of the heart. The coronary sinus is a vein on the posterior side of the heart that returns deoxygenated blood from the myocardium to the vena cava  Hepatic Portal Circulation The veins of the stomach and intestines perform a unique function: instead of carrying blood directly back to the heart, they carry blood to the liver through the hepatic portal vein. The liver removes toxins, stores sugars, and processes the products of digestion before they reach the other body tissues. Blood from the liver then returns to the heart through the inferior vena cava  Blood Vessels Blood vessels allow blood to flow quickly and efficiently from the heart to every region of the body and back again. The size of blood vessels corresponds with the amount of blood that passes through the vessel. All blood vessels contain a hollow area called the lumen through which blood is able to flow. Around the lumen is the wall of the vessel, which may be thin in the case of capillaries or very thick in the case of arteries.  Types of blood vessels There are three major types of blood vessels: Arteries, Veins, and capillaries. Blood vessels are often named after the region of the body through which they carry blood or for nearby structures. For example, the brachiocephalic artery carries blood into the brachial (arm) and cephalic (head) regions  How the blood flows in veins and venules? some veins contain many one-way valves that prevent blood from flowing away from the heart. As skeletal muscles in the body contract, they squeeze nearby veins and push blood through valves closer to the heart. When the muscle relaxes, the valve traps the blood until another contraction pushes the blood closer to the heart. Structural differences among blood vessels  Structure of blood vessels The tunica intima (also called the tunica interna) is composed of epithelial and connective tissue layers. Lining the tunica intima is the specialized simple squamous epithelium called the endothelium, the basement membrane, or basal lamina, that effectively binds the endothelium to the connective tissue. The tunica media is the substantial middle layer of the vessel wall. It is generally the thickest layer in arteries, and it is much thicker in arteries than it is in veins. The outer tunic, the tunica externa (also called the tunica adventitia), is a substantial sheath of connective tissue composed primarily of collagenous fibers. Some bands of elastic fibers are found here as well. Structural differences among blood vessels  Comparison of Arteries and Veins Characteristics Arteries Veins Direction of Conducts blood away from Conducts blood toward the heart blood flow the heart General Rounded Irregular, often collapsed appearance Pressure High Low Wall thickness Thick Thin Relative oxygen Higher in systemic arteries Lower in systemic veins concentration Lower in pulmonary arteries Higher in pulmonary veins Valves Not present Present most commonly in limbs and in veins inferior to the heart