Chapter 12 Cardiovascular System

Transcription

1 Chapter 12 Cardiovascular System Cardiovascular System Includes Heart and Blood Vessels Transports, nutrients and wastes to and from the tissues 1 The Blood Vessels Three Types of Blood Vessels Arteries: carry away from the heart Mostly carry oxygen-rich Exception: going from heart to lungs Capillaries: permit exchange of materials with tissues Veins: carry toward the heart Mostly carry oxygen-poor Exception: coming from lungs to heart The Blood Vessels: Anatomy The Arteries Three layers to an arterial wall Endothelium Inner layer - simple squamous epithelium with basement membrane Middle layer Thickest layer, contains smooth muscle Outer layer Fibrous and loose connective tissue 12.1 The Blood Vessels a. Artery arteriole b. Capillary valve inner layer middle layer outer layer c. Vein venule The Capillaries Join arterioles to venules Extremely narrow and only a single layer of endothelium thick Form vast networks in all regions of the body Very important role in homeostasis exchange of substances Oxygen and nutrients Wastes and carbon dioxide Water also leaves capillaries 1

2 Anatomy of a Capillary Bed flow arteriole precapillary sphincters capillaries arteriovenous shunt venule flow 12.1 The Blood Vessels The Veins Walls are structured similarly to the walls of arteries (three layers) Less smooth muscle and connective tissue in s so THINNER WALLS Often have valves to prevent the backflow of Especially important in s of lower body parts Valves malfunction causes back flow and pooling of s in legs (Varicose s) Great capacity to expand (thin walls!) Serve as reservoir Any given time 70% of is in s Cone-shaped about the size of a fist Lies between the lungs directly behind the sternum Tilted so apex pointed to body s HEART is a PUMP 1. Collects oxygen-poor from all body tissues 2. Pumps oxygen-poor to lungs 3. Receives oxygen rich from lungs 4. Pumps oxygen-rich to all body tissue Myocardium Major portion of the heart Consists mainly of cardiac muscle Pericardium Serous membrane that surrounds the heart Endocardium Lines the inner surface of the heart Membrane consisting of connective tissue and endothelium External Heart Anatomy External Heart Anatomy superior superior and arteries Right and s trunk coronary atrium atrium coronary inferior ventricle ventricle inferior apex a. cardiac cardiac 2

3 Internal anatomy Four-chambers Two atria thin-walled Two ventricles thick-walled, pump to lungs and body Septum separates the and sides Internal Anatomy Four valves prevent the backflow of Two atrioventricular valves at the junction of atrium and ventricle AV valve on = tricuspid valve AV valve on = bicuspid or mitral valve Two semilunar (half moon shaped) valves Pulmonary semilunar at the junction of ventricle and Aortic semilunar at the junction of ventricle and Internal View of the Heart (Flow into and out of Right chambers: O 2 poor ) Internal View of the Heart (Flow into and out of Left Chambers: O 2 rich ) Arteries : to rest of the body superior (To lung) (to lung) semilunar valve atrium s s atrium atrio ventricular (bicuspid) valve atrioventricular (tricuspid) valve ventricle septum ventricle inferior venacava septum Path of Blood Through the Heart O 2 -rich to body O 2 -poor to lungs Venae cavae atrium tricuspid valve ventricle semilunar valve trunk arteries lungs s atrium bicuspid valve ventricle aortic semilunar valve body O 2 -poor from body O 2 -rich from lungs b. 3

4 Oxygen-rich does not mix with oxygen-poor Blood must travel through the lungs to go from the side of the heart to the side Heart is described as a double pump Right ventricle sends oxygen-poor into the circuit Left ventricle sends oxygen-rich into the systemic circuit The Heartbeat (Cardiac Cycle) 70 times per minute Each time the heart beats: The two atria contract simultaneously Then the two ventricles contract simultaneously All the chambers then relax Systole: Contraction of the heart muscle Diastole: Relaxation of the heart muscle semilunar valves superior semilunar valvesclose ( dup ) The Heartbeat Heart Sounds Described as a lub-dup sound atrium a. atrium ventricle atrium c. inferior Lub sound - atrioventricular valves closing Dup sound - semilunar valves closing ventricle A heart murmur (swishing sound) may be due to a leaky mitral valve atrioventricular valves close ( lub ) b. head and arms 12.3 The Vascular Pathways The cardiovascular system has two circuits: The Pulmonary Circuit Circulates through the lungs The Systemic Circuit Circulates through the rest of the body The Pulmonary Circuit Blood from the body collects in the atrium Right Atrium Right Ventricle Pulmonary Arteries Arterioles Capillaries Venules Pulmonary Veins Left atrium CO 2 O 2 jugular Carotid (also subclavian (also subclavian from arms) to arms) CO 2 O 2 O 2 CO 2 lungs superior heart inferior arteries digestive liver tract portal renal renal kidneys iliac iliac CO 2 O 2 Trunk and legs 4

5 head and arms The Systemic Circuit Blood leaves the ventricle, travels through the body and is returned to the heart arteries arterioles capillaries venules s jugular (also subclavian from arms) superior inferior portal renal iliac O 2 CO 2 O 2 CO 2 O 2 liver kidneys lungs digestive tract CO 2 heart Carotid (also subclavian to arms) arteries renal iliac common carotid internal jugular superior renal inferior common iliac femoral external jugular subclavian subclavian renal common iliac femoral great saphenous CO 2 O 2 Trunk and legs Coronary arteries Serve the heart muscle itself First branches off Cardiac s empty into atrium Portal system begins and ends in capillaries Hepatic portal system superior trunk coronary coronary inferior cardiac cardiac b. arteries digestive liver tract 12.3 The Vascular Pathways Blood pressure 120/80 normal (Systolic/diastolic) Systolic Pressure results from forced into the arteries during ventricular systole (Contraction) Diastolic Pressure is the pressure in the arteries during ventricular diastole (relaxation) As flows from the into the arteries and arterioles, pressure falls Also, the difference between systolic and diastolic pressure gradually diminishes In the capillaries, flow is slow and fairly even 12.3 The Vascular Pathways 12.3 The Vascular Pathways Blood Pressure Measured with sphygmomanometer Pressure cuff determines the amount of pressure required to stop the flow of through an Normally measured on the brachial Artery in the upper arm Expressed in millimeters of mercury (mmhg) 120/80 Blood pressure In s is low and by itself not enough to move back to heart When skeletal muscles contract they put pressure on s Valves prevent backflow Muscle contraction moves back to the heart to heart a. Contracted skeletal muscle pushes past open valve. to heart b. Closed valve prevents back ward flow of. 5

6 eosinophil platelets Plasma Liquid portion of the Formed Elements Red cells White cells Platelets Formed elements a. Plasma (about 55% of whole ) Leukocytes and platelets (<1% of whole ) Erythrocytes (about 45% of whole ) monocyte neutrophils basophil lymphocyte red cell c. 250 Blood has: Transport functions: Nutrients, gases and wastes Regulatory functions: Heat dispersal, pressure Protective functions: Fights infection, prevents loss by clotting Plasma Contains inorganic and organic substances dissolved or suspended in water Plasma proteins Various functions Transport of substances: albumin transports bilirubin clotting: fibrinogen critical for clotting fighting disease: antibodies fight infections Help maintain volume Red Blood Cells (Erythrocytes) Manufactured in red bone marrow When mature lack a nucleus Shape is biconcave disc Contain hemoglobin Red iron-containing pigment Heme portion binds oxygen Carbon monoxide can also bind at heme sites Combines more readily than oxygen Can be lethal Anemia capillary a. Blood capillary 400 b. Red cells SEM 4,175 helical shape of the polypeptide molecule heme iron group c. Hemoglobin molecule Anemia Too few red cells,or Not enough hemoglobin in red cells Three causes Decreased production of red cells»iron-deficiency anemia Loss of red cells Destruction of red cells 6

7 White Blood Cells (Leukocytes) Usually larger than red cells Nucleated Lack Hemoglobin (therefore white!) Role is to fight infection and provide immunity White Blood Cells: Two major types and various subtypes All critical for fighting infection in various ways 1. Granular leukocytes Have visible granules in cytoplasm a) Neutrophils- most abundant leukocyte, phagocytic b) Basophils-granules stain deep blue and release histamine c) Eosinophils-stain deep red, fight parasitic worms 2. Agranular leukocytes Lack visible granules a) Lymphocytes: T and B cells, roles in immunity b) Monocytes-largest WBC s: phagocytic dendritic cells and macrophages A macrophage engulfing bacteria cytoplasmic extension from macrophage bacteria White Blood Cells (WBCs) The number or cell count of specific types of leukocytes can be used in diagnosing disease. Viral infections may increase no. of WBC AIDS (Acquired immune deficiency syndrome): Reduced no. of T-lymphocytes so compromised immune response Leukemia: Uncontrolled division of WBCs (cancer of WBCs) SEM 1,075 The Platelets (thrombocytes) Are fragments of certain kind of cells in bone marrow Involved in the process of clotting or coagulation Blood Clotting Damage to vessel Platelets clump and form a plug to partially seal a leak Clotting factors in plasma are activated Threads of protein, called fibrin, are made to reinforce platelet plug and form the clot Vitamin K is important for clotting 7

8 Blood-clotting process 1. Blood vessel is punctured. fibrin threads 2. Platelets congregate and form a plug. red cell Prothrombin activator b. Blood clot 4, Platelets and damaged tissue cells initiate a cascade of enzymatic reactions to activate clotting factors Prothrombin Fibrinogen Ca2 + Thrombin Ca2 + Fibrin threads Blood Clot Red cells trapped in the clot make it appear red 4. Fibrin threads form and trap red cells. The Platelets and Blood Clotting Hemophilia Inherited disorder Most common type has faulty gene on X chromosome Deficiency in a clotting factor Internal bleeding can cause serious damage to cells and tissues Hemophilia is treated by transfusions and injections of clotting factors Bone Marrow Stem Cells Cells which are capable of dividing and differentiating into particular cell types Bone marrow cells are multipotent Red and white cells Some may even be able to give rise to liver, bone, fat, cartilage, heart, and nerve cells May provide solutions for diseases such as Alzheimer s and Parkinson s Many researchers prefer to work with embryonic stem cells Totipotent - can become any cell type 8