Chapter 12

Topics: Blood, Heart, Artery Pages: 8 (1906 words) Published: February 18, 2013
Chapter 12: Cardiovascular System

3 types of blood vessels
* Arteries: carry blood away from the heart to the capillaries * Capillaries: permit exchange of material with the tissues * Veins: return blood from the capillaries to the heart.

Wall has 3 layers
* Endothelium: inner layer, made up of simple squamous epithelium, with a connective tissue basement membrane that has elastic fibers. * Middle layer: thickest later and consists of smooth muscle that can contract to regulate blood flow and blood presser. * Outer layer: fibrous connective tissue near the middle layer, but it becomes loose connective tissue at its periphery. Aorta: largest artery in the human body

* Carries 0 rich blood from the heart to other body parts. * Smaller arteries branch off from the aorta, forming a large number of arterioles. Arterioles: small arteries just visible to the naked eye.

* Inner layer: endothelium
* Middle layer: elastic tissue and fibers that encircle the arteriole. When the muscle fibers are contracted, the vessels diameter becomes smaller. When the muscle fibers are relaxed, the vessels diameter becomes larger.

The Capillaries
* Join arterioles to venules
* Walls are composed of single layers of endothelium with a basement membrane. * Total surface area in the body is about 6,000 square meters. * Cornea of the eye, is capillary free

Homeostasis in capillaries
* Oxygen and nutrients, such as glucose diffuse out of a capillary into the tissue fluid that surrounds cells. * Wastes, such as carbon dioxide, diffuse into the capillaries. * Any excess is picked up by the lymphatic vessels.

The Veins
* Take blood from the capillary beds to the heart
Venules: small veins
* Venules drain blood from the capillaries and then join to form a vein

Have the same 3 layers as arteries do
Valves: allow flood to flow only toward the heart and open and prevent blood from flowing backwards when closed. * Valves are found in veins that carry blood against the force of gravity Blood flow in veins is primarily due to the skeletal muscle contractions * Blood can become pooling in the veins as one ages, causing them to enlarge and be visible as varicose veins. * 70% of blood is in the veins

* Superior vena cava is the biggest vein in the body

Human Heart
Heart: cone shaped, muscular organ about the size of a fist
* Located between the lungs and the sternum
* Myocardium: major portion of the heart, consisting of cardiac muscle tissue * Muscle fibers are tightly attached to the myocardium
* Pericardium: where the heart lays, has a serous membrane that secretes a small quality of lubricating liquid * Inner surface of heart is lined with endocardium, a membrane composed of connective tissue and endothelial tissue * Septum: separated the heart into the left and right side

4 chambers of the heart: two upper, thin walled atria, which are located above the two lower thick walled ventricles. * Ventricles: pump the blood to the lungs and body
4 valves
* Direct the flow of blood and prevents its backwards movement * Atrioventricular valves: two valves that lie between the atria and the ventricles. * Supported by strong fibrous strings called chordae tendineae * Chordae: attached to muscular projections of the ventricular walls and supports the valves and prevents them from inverting when the heart contracts. * Tricuspid: The atrioventricular valve on the body's right side; has three flaps, or cusps. * Bicuspid: The valve on the left side; has two flaps.

* Semilunar valves: two valves between the ventricles
* The pulmonary semilunar valve lies between the right ventricle and the pulmonary trunk. * The aortic semilunar valve lies between the left ventricle and the aorta. Path of Blood Through the Heart

* The superior vena cava and the inferior vena cava, which carry...
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