Blood and Heart. Student Learning Objectives:

Transcription

1 Blood and Heart Student Learning Objectives: Identify the major components of the blood. Identify the primary structures associated with the heart Follow the blood through the path of the circulation. Structures to be studied: Blood components: Plasma Serum Erythrocytes/Red Blood Cells Leukocytes/White Blood Cells Thrombocytes/Platelets Cardiac Chambers: Left ventricle Right ventricle Left atrium Right atrium Cardiac Valves: Tricuspid Bicuspid (mitral) Aortic Pulmonic Major vessels: Aorta Pulmonary artery (trunk) Superior vena cava Inferior vena cava Pulmonary veins Introduction The cardiovascular system is very complex and extremely important to the functioning of the body. Materials will be transported around the body from organ system to organ system by the circulation. There are multiple components of this system. The blood is the transport medium for the materials that every body organ system needs to survive. The heart serves as the pump which moves this fluid from place to place. The vessels provide the tubing through with the blood will travel. Nutrient materials are brought into the body via the digestive system. Many waste products are eliminated through the urinary system. Gases are exchanged with the external environment in the lungs. Body cells are using nutrients and oxygen and creating waste products and carbon dioxide during their metabolic activities. In addition, part of the control of body organs involves the endocrine system that relies on the cardiovascular system to transport its hormones. The cardiovascular system provides the means to allow all of these different structures to interact with one another. Ultimately, this provides the cells of the body with all of the materials that the cells need to function, while helping to remove materials that the cell does not require or that have been produced as waste products by the cells. In this exercise, we will briefly look at the blood but will focus primarily on the heart. In the next exercise, we will examine the vasculature that forms the pipelines of the system.

2 Blood Blood is the liquid material in which most of the nutrients and waste materials are moved around in the circulation. Blood is composed of two main parts: the fluid component and the cellular components. The first component of the blood is a fluid known as plasma or serum, depending upon how the blood sample was collected. The fluid will be called plasma if the blood is still in a liquid form when the fluid is extracted from it. This would be the fluid found in the blood flowing through the blood vessels. In order to keep blood in a liquid form when it is removed from the body, one must add special chemicals, known as anticoagulants, to the blood. Anticoagulants prevent the blood from clotting. If this blood sample is placed into a centrifuge and spun at very high speeds, the cells will fall to the bottom of the tube, leaving the plasma at the top. If anticoagulants are not added to the blood sample when it is removed from the body, the blood will quickly clot. If this blood sample is placed in the centrifuge and spun, the cells will again fall to the bottom of the tube leaving serum as the fluid at the top of the tube. Serum and plasma are very similar in composition. Both are mostly composed of water (~91%) with a protein component (~7%). The materials that are being transported around in the blood comprise only about 2% of these fluids. The main difference between the composition of plasma and that of serum is that serum lacks a protein (i.e. fibrinogen) that is present in plasma. That protein which is missing from serum was used up during the clotting process. Because plasma comes from an unclotted blood sample, the protein is still present in the liquid. Erythrocytes are the main type of cell in the blood. Erythrocytes are more commonly known as red blood cells or RBC s. These cells are red in color because they contain and iron pigment, called hemoglobin, which is involved in the transport of gases, especially oxygen, around the body. These cells lack a nucleus (i.e. they are anuclear). Leukocytes are the white blood cells or WBC s. These are nucleated cells i.e. they have a nucleus. The shape of the nucleus can help us to identify the type of white blood cell. There are five different types of leukocytes. Some of these cells contain cytoplasmic granules that stain different colors and perform important functions for the body. Neutrophils are the most common WBC and have granules that stain very poorly. This type of granule is difficult to see. Eosinophils have red-staining granules (as seen in the WBC in the picture). Basophils have blue/purple-staining granules. The other two WBC varieties do not have granules. Lymphocytes are the second most common type of WBC, and monocytes are the largest of all blood cells. Thrombocytes are better known as platelets. These are tiny pieces of a very large cell that lives in the bone marrow (called a megakaryocyte). These small fragments of the megakaryocyte are sent into the blood to assist with the process of blood clotting.

3 Heart The word cardiac refers to heart. The inner lining of the heart is called the endocardium and consists of a very thin membrane similar to that which lines the blood vessels. The myocardium is the middle muscular layer, consisting of cardiac muscle. The outer layer, the epicardium, is also a thin membrane. Surrounding the entire heart is a fibrous bag called the pericardial sac which prevents over-filling and secures the heart in the chest. The heart consists of four chambers. Two of these chambers are very thin-walled collecting compartments, the atria. The right and left atria are about 1/8 thick. The right atrium collects the blood that is returning to the heart from the body structures. The left atrium collects blood that is returning to the heart from the lungs. The atria can be seen best from a posterior view of the heart. The other two are thick-walled pumping chambers, the ventricles. The right ventricle is about 1/2 thick and the left ventricle is about 1 thick. The right ventricle pumps blood out to the lungs and the left ventricle pumps blood out to the body organs. (Anterior view) (Posterior view) In order to ensure that the blood is always traveling in the right direction through the heart, s have been placed at strategic places in the cardiac structure. Two of the s separate the atrium from the ventricle on each side of the heart. These are known as atrioventricular or AV s. These s prevent the backflow of blood into the atria during the contraction of the ventricles. The AV s are composed of fibrous flaps that are anchored down by strong bands called chordae tendinae. These bands attach to the wall of the ventricle and prevent the flaps of the from leaking when the ventricles are pumping. The tricuspid is the AV on the right side of the heart. The bicuspid, or mitral, is the AV on the left side of the heart.

4 The second group of s is the semilunar s. These lie at the base (i.e. top) of the ventricles on either side of the interventricular septum, the wall that separates the two ventricles. The semilunar separates a ventricle from its major artery. A semilunar has three pockets that form the structure. When blood is flowing in the proper direction, the flaps flatten against the wall of the vessel. If blood tries to backflow into the ventricle, the pockets fill with blood and obstruct the vessel. The semilunar on the right side is called the pulmonic because it separates the right ventricle from the pulmonary artery. The aortic is the semilunar on the left side, separating the left ventricle and the aorta. There are several very large vessels associated with the heart. The aorta and pulmonary artery are the major arteries associated with the heart. The aorta exits from the left ventricle. The pulmonary artery exits from the right ventricle. The vena cavae and the pulmonary veins are the major veins associated with the heart. The superior vena cava and inferior vena cava are associated with the right atrium. The pulmonary veins enter the left atrium. (Anterior view) (Posterior view)

5 Circulation Pathways PULMONIC CIRCULATION Lung Capillaries Pulmonary arteries Pulmonary veins Right atrium Left atrium Pulmonic Tricuspid Bicuspid Right Ventricle Left Ventricle Aortic Superior (upper body) inferior (lower body) vena cava Aorta Veins Arteries Tissue Capillaries SYSTEMIC CIRCULATION