The Circulatory System The Heart, Blood Vessels, Blood Types

The Closed Circulatory System Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid. The heart pumps blood into large vessels that branch into smaller ones leading into the organs. Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.

The Cardiovascular System Three Major Elements – Heart, Blood Vessels, & Blood 1. The Heart- cardiac muscle tissue highly interconnected cells four chambers Right atrium Right ventricle Left atrium Left ventricle

Pathway of the blood Superior Vena Cava Right Atrium Tricuspid Valve Right Ventricle Pulmonary Semilunar Valve Lungs Pulmonary Vein Left atrium Bicuspid Valve Left ventricle Aortic Semilunar Valve Aorta To the bodies organs & cells

Circuits Pulmonary circuit Systemic circuit The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart. Systemic circuit The pathway between the left and right sides of the heart.

The Cardiovascular System 2. Blood Vessels -A network of tubes Arteriesarterioles move away from the heart Elastic Fibers Circular Smooth Muscle Capillaries – where gas exchange takes place. One cell thick Serves the Respiratory System VeinsVenules moves towards the heart Skeletal Muscles contract to force blood back from legs One way values When they break - varicose veins form

The Cardiovascular System 3. The Blood Plasma Liquid portion of the blood. Contains clotting factors, hormones, antibodies, dissolved gases, nutrients and waste

The Cardiovascular System The Blood B. Erythrocytes - Red Blood Cells Carry hemoglobin and oxygen. Do not have a nucleus and live only about 120 days. Can not repair themselves.

The Cardiovascular System The Blood C. Leukocytes – White Blood cells Fight infection and are formed in the bone marrow Five types – neutrophils, lymphocytes, eosinophils, basophils, and monocytes.

The Cardiovascular System The Blood D. Thrombocytes – Platelets. These are cell fragment that are formed in the bone marrow from magakaryocytes. Clot Blood by sticking together – via protein fibers called fibrin.

Disorders of the Circulatory System Anemia - lack of iron in the blood, low RBC count Leukemia - white blood cells proliferate wildly, causing anemia Hemophilia - bleeder’s disease, due to lack of fibrinogen in thrombocytes Heart Murmur - abnormal heart beat, caused by valve problems Heart attack - blood vessels around the heart become blocked with plaque, also called myocardial infarction

Cardiovascular System Unit 9 – The Heart Cardiovascular System The Heart

Functions of the Heart Generating blood pressure Routing blood Heart separates pulmonary and systemic circulations Ensuring one-way blood flow Heart valves ensure one-way flow Regulating blood supply Changes in contraction rate and force match blood delivery to changing metabolic needs

Size, Shape, Location of the Heart Size of a closed fist Shape Apex: Blunt rounded point of cone Base: Flat part at opposite of end of cone Located in thoracic cavity in mediastinum

Heart Cross Section

Pericardium

Heart Wall Three layers of tissue Epicardium: This serous membrane of smooth outer surface of heart Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting Endocardium: Smooth inner surface of heart chambers

Heart Wall

External Anatomy Four chambers Auricles Major veins Major arteries 2 atria 2 ventricles Auricles Major veins Superior vena cava Pulmonary veins Major arteries Aorta Pulmonary trunk

External Anatomy

Coronary Circulation

Heart Valves Atrioventricular Semilunar Tricuspid Bicuspid or mitral Semilunar Aortic Pulmonary Prevent blood from flowing back

Heart Valves

Function of the Heart Valves

Blood Flow Through Heart

Systemic and Pulmonary Circulation

Heart Skeleton Consists of plate of fibrous connective tissue between atria and ventricles Fibrous rings around valves to support Serves as electrical insulation between atria and ventricles Provides site for muscle attachment

Cardiac Muscle Elongated, branching cells containing 1-2 centrally located nuclei Contains actin and myosin myofilaments Intercalated disks: Specialized cell-cell contacts Desmosomes hold cells together and gap junctions allow action potentials Electrically, cardiac muscle behaves as single unit

Conducting System of Heart

Tissue engineering https://www.ted.com/talks/nina_tandon_could_tissue_engineering_mean_personalized_medicine Heart schaffolding video http://www.nature.com/news/tissue-engineering-how-to-build-a-heart-1.13327

Conduction system of the Heart…PPT2

Depolarization of muscle fibers = contraction of muscles Cardiac Conduction Electrical impulses generate action potentials. Depolarization of muscle fibers = contraction of muscles Polarization of muscle fibers = relaxation of muscles The SA node receives electrical impulses. This SA node is located on the upper right atrium. This node serves as the hearts pacemaker, regulating the pace and initiating the beat sequence. Electrical impulses from the SA node spread throughout both atria and the muscle fibers depolarize , causing them to contract (pushing blood into the ventricles) (Atrial Systole)

Cardiac Conduction https://www.youtube.com/watch?v=RYZ4daFwMa8 The AV node is located on other side of right atrium . The AV node Serves as the gateway to the ventricles. It delays the passage of electrical impulses to the ventricles. So that the atria have ejected all the blood into the ventricles before ventricles contract. AV node receives signals from the SA node and passes them onto the atrioventricular bundle, the bundle of HIS. This bundle is divided into right and left branches and conducts the impulses towards the apex of the heart. The signals are then passed onto Purjinje fibers, turning upward, spreading throughout the ventricular myocardium. As the signal spreads through the ventricles, muscle fibers depolarize and contract, pushing blood to lungs and aorta.

https://www.youtube.com/watch?v=v3b-YhZmQu8 Another good video

Electrical stimuluses’ of the heart can be recorded in the form of an ECG, electrocardiogram or EKG. Action potentials through myocardium during cardiac cycle produces electric currents than can be measured Pattern P wave Atria depolarization QRS complex Ventricle depolarization Atria repolarization T wave: Ventricle repolarization

What does the ECC show about the Heart? When the atria are full of blood the SA node fires, electrical signals spread throughout the atria and cause them to depolarize. This is represented by the P wave on the ECG. Atrial contraction (systole ) starts about 100ms after the P wave begins.

Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm Bradycardia: Heart rate less than 60 bpm Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

The PQ segment represents the time the signals travel from the SA node to the AV node. The QRS complex marks the firing of the AV node and represents ventiricular depolarization (contraction) ( systole) Q corresponds to the depolarization of the interventricuoar septum.

. R wave is produced by depolarization of the main mass of the ventricles. S wave represents the last phase of ventricular depolarization at the base of the heart. During the QRS wave the Atrial repolarization occurs but can’t be seen due to the big QRS wave.

ST complex represents the myocardial action potential ST complex represents the myocardial action potential. This is when the ventricles contract and pump blood. The T wave represents ventricular repolarization immediately before ventricular relaxation (diastole)   The cycle repeats itself with every heartbeat.

Alterations in Electrocardiogram

Cardiac Cycle Heart is two pumps that work together, right and left half Repetitive contraction (systole) and relaxation (diastole) of heart chambers Blood moves through circulatory system from areas of higher to lower pressure. Contraction of heart produces the pressure

Cardiac Cycle

Heart Sounds First heart sound or “lubb” Second heart sound or “dupp” Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole Second heart sound or “dupp” Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer Third heart sound (occasional) Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

Location of Heart Valves

Mean Arterial Pressure (MAP) Average blood pressure in aorta MAP=CO x PR CO is amount of blood pumped by heart per minute CO=SV x HR SV: Stroke volume of blood pumped during each heart beat HR: Heart rate or number of times heart beats per minute Cardiac reserve: Difference between CO at rest and maximum CO PR is total resistance against which blood must be pumped

Factors Affecting MAP

Regulation of the Heart Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation Starling’s law of the heart Extrinsic regulation: Involves neural and hormonal control Parasympathetic stimulation Supplied by vagus nerve, decreases heart rate, acetylcholine secreted Sympathetic stimulation Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released

Heart Homeostasis Effect of blood pressure Baroreceptors monitor blood pressure Effect of pH, carbon dioxide, oxygen Chemoreceptors monitor Effect of extracellular ion concentration Increase or decrease in extracellular K+ decreases heart rate Effect of body temperature Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

Baroreceptor and Chemoreceptor Reflexes

Baroreceptor Reflex

Chemoreceptor Reflex-pH

Effects of Aging on the Heart Gradual changes in heart function, minor under resting condition, more significant during exercise Hypertrophy of left ventricle Maximum heart rate decreases Increased tendency for valves to function abnormally and arrhythmias to occur Increased oxygen consumption required to pump same amount of blood