The Circulatory System rev 6-10

The Circulatory System rev 6-10
The circulatory system consists of the heart, blood vessels and the blood itself. The circulatory system is essential to supply all cells with what they need and remove substances they no longer need. This system maintains homeostasis. Circulatory System--BIO 006

Circulatory System--BIO 006
Types of Blood Vessels Arteries—carry blood away from the heart Veins—carry blood toward the heart Capillaries—carry blood from the arterioles to the venules. Exchange of nutrients, wastes and respiratory gases takes place here because capillaries have only one layer. Bigggest Artery, Biggest Vein Aorta: carries blood out of the left ventricle of the heart Inferior and Superior Vena Cava return blood to the right atrium of the heart after the blood has circulated throughout the body. Circulatory System--BIO 006 2

Structure--Arteries inner layer of endothelial cells middle: smooth muscle tissue This layer is thicker in arteries than in veins outermost layer of connective tissue Structure—Veins Inner: layer of endothelial cells Valves prevent backward movement of blood Middle: smooth muscle tissue thinner layer in veins than in arteries can be thicker than in arteries Circulatory System--BIO 006 3

Functions Arteries—take blood away from the heart to the body distribute nutrients and gases; movement of blood is under higher pressure than in veins; assist in maintaining blood pressure Veins---return blood to the heart; lower pressure than in arteries; can act as a blood volume reservoir for blood because they can expand veins have larger diameters (lumen) than arteries Circulatory System--BIO 006 4

blood-cardiovascular
the larger diameter of veins allows them to stretch to accommodate large volumes of blood at low pressures because veins can stretch, it is more difficult for them to return blood to the heart against the force of gravity people who spend a lot of time on their feet may get varicose veins because of this Factors which help veins to return blood to heart Contraction of skeletal muscles—skeletal muscle pump as we move, muscles contract and relax and they press against veins and help push blood to the heart blood-cardiovascular 5

One-way valves—blood can only flow in one direction Open passively to allow blood to move toward the heart and close whenever blood begins to flow backward blood-cardiovascular 6

Pressure changes associated with breathing movements associated with breathing also help pump blood. This is called a respiratory pump and helps to push blood from the abdomen to the chest and to the heart. when we breathe, there are pressure changes in the thoracic and abdominal cavities during inhalation, abdominal pressure increases and squeezes abdominal veins simultaneously, pressure within the thoracic cavity decreases which dilates the thoracic veins and thus propels the blood. blood-cardiovascular 7

Venous return of blood to the heart depends on five mechanisms: a strongly beating heart, adequate arterial blood pressure, valves in the veins, pumping action of skeletal muscles as they contract (skeletal muscle pump), and changing pressures in the chest cavity caused by breathing (respiratory pump) Circulatory System--BIO 006

The Heart Structure: composed of cardiac muscle enclosed by pericardium, a fibrous sac located in mediastinum is approximately the size of a closed fist Pericardium protects the heart, anchors it to surrounding structures, prevents it from overfilling with blood Pericardial cavity separates it from heart muscle itself and contains a tiny amount of fluid to allow heart and pericardium to glide smoothly every time the heart contracts Rate of pumping usually controlled by brain blood-cardiovascular 9

Anatomy Heart chambers The two upper chambers are called the right and left atria and are the chambers which receive blood The two lower chambers are the right and left ventricles; these are the chambers which eject blood The wall of each heart chamber is composed of cardiac muscle tissue called myocardium Circulatory System--BIO 006

In order to keep the blood moving in a forward direction, there are valves in between each area the blood must go. Valves of the heart Atrioventricular or AV valves are located between the atria and the ventricles Left side: bicuspid or mitral valve Right side: tricuspid valve Chordae tendineae are located inferiorly to the AV valves and attach the valves to the heart wall Circulatory System--BIO 006

Semilunar Valves are located between the 2 ventricles and the arteries that carry blood away from the heart when a contraction begins. Pulmonary semilunar valve is located at the beginning of the pulmonary artery Aortic semilunar valve is located at the beginning of the aorta Circulatory System--BIO 006

Blood flow through the heart venous blood enters the right atrium through the superior and inferior venae cavae (biggest vein) passes from the right atrium through the tricuspid valve to the right ventricle; from the right ventricle it passes through the pulmonary semilunar valve to the pulmonary artery to the lungs from the lungs blood flows to the left atrium through the pulmonary vein passes through the bicuspid (mitral) valve to the left ventricle; blood in the left ventricle is pumped through the aortic semilunar valve into the aorta (biggest artery) and is distributed to the entire body Circulatory System--BIO 006

There are actually 2 circulations through the heart: The pulmonary circulation involves movement of blood from the right ventricle to the pulmonary arteries to the lungs and then through the pulmonary veins back to the left atria. The systemic circulation involves movement of the blood from the left ventricle throughout the body. Circulatory System--BIO 006

Part of the systemic circulation includes the coronary circulation: blood supply to the heart muscle itself Blood, which supplies oxygen and nutrients to the myocardium of the heart, flows from the first branch off the aorta through the right and left coronary arteries Blockage of blood flow through the coronary arteries can cause a myocardial infarction (heart attack) Circulatory System--BIO 006

Types of Circulation Systemic circulation Carries blood throughout the body Path goes from left ventricle through aorta, smaller arteries, arterioles, capillaries, venules, inferior and superior venae cavae, to right atrium Pulmonary circulation Carries blood to and from the lungs; arteries deliver deoxygenated blood to the lungs for gas exchange Path goes from right ventricle through pulmonary arteries, lungs, pulmonary veins, to left atrium Circulatory System--BIO 006 16

Hepatic portal circulation (blood route through the liver) Veins from the spleen, stomach, pancreas, gallbladder and intestines detour their blood to the liver via the hepatic portal vein Blood then goes through the capillaries of the liver where excess glucose from our meals is removed and stored as glycogen Blood is also detoxified---poisonous substances, alcohol, drugs are removed Then the blood enters into the systemic circulation via the inferior vena cava Circulatory System--BIO 006 17

Heart pumping The contraction of the heart is called systole; relaxation is diastole When the heart beats, the atria contract first and force blood into the ventricles Once filled, the ventricles contract and force blood out of the heart Circulatory System--BIO 006

Electrical Conduction System of the Heart Intercalated disks are electrical connectors that join all the cardiac muscle fibers in a region together so that they receive their impulse and then contract at about the same time 4 structures are located in the wall of the heart. These are specialized to initiate strong impulses and rapidly conduct them to certain regions in the wall of the heart. This ensures that first the atria contract and then the ventricles contract in an efficient pattern Circulatory System--BIO 006

Cardiac Anatomy Quiz blood-cardiovascular 20

Blood Pressure Blood pressure measures the force of blood in the blood vessels Highest in arteries, lowest in veins Blood pressure causes blood to circulate—liquids can flow only from the area where pressure is higher to where it is lower Top number= systolic reading—force the heart uses to pump the blood Bottom number= diastolic reading—heart at rest or relaxing Normal is approximately 120/70-80 Circulatory System--BIO 006

Blood volume, heartbeat, and viscosity (thickness) are the main factors that produce blood pressure Blood pressure varies within normal range from time to time Pulse Definition—alternate expansion and recoil of the blood vessel wall Places where the pulse is typically taken: carotid artery, brachial artery, radial artery Circulatory System--BIO 006

Cardiovascular Disorders
Angina pectoris: chest pain caused by inadequate oxygen to the heart Pericarditis: layer of the coverings of the heart becomes inflamed. This causes pain each time the heart beats Heart murmur is created by obstructions the blood must flow over or if the valves don’t function properly Coronary bypass surgery: veins from other parts of the body are used to bypass blockages in coronary arteries Aneurysm: the arterial wall has a weakness and blood pushes it out into a balloon shape Circulatory System--BIO 006

Hypertension: high blood pressure Signs: headache, blurred vision Causes: kidney disorders, smoking, overweight, stress Hypotension: blood pressure too low so blood can’t be pushed throughout the body and back to the heart; generally thought of as reducing blood flow to the brain Signs: dizziness, fainting Causes: orthostatic, severe burns, blood loss Circulatory System--BIO 006

Myocardial infarction/heart attack: permanent cardiac damage Congestive heart failure: decrease in pumping efficiency Embolism: blockage of blood vessels Thrombus=clot that doesn’t move Embolus=clot that travels through the circulatory system Stroke or Cerebrovascular Accident or brain attack: impaired blood flow with subsequent damage to the brain Circulatory System--BIO 006

Disorders of Blood Clotting Thrombus: clot forms in the blood vessel Embolus: clot which breaks off and circulates through the blood Medications to dissolve clots: Streptokinase and recombinant tissue plasminogen activator Hemophilia: Inherited condition caused by a deficiency of one or more clotting factors (known as clotting factor VIII) When a blood vessel is damaged, blood either clots very slowly or not at all Circulatory System--BIO 006

Reducing the Risks of Heart Disease
Smoking: don’t Weight: maintain a normal weight (weighing too much will increase the risk of a heart attack or stroke) Monitor cholesterol levels, HDL, LDL, triglycerides Regular exercise Blood pressure: treat hypertension Control of diabetes mellitus Stress: avoid chronic stress Circulatory System--BIO 006

The Circulatory System rev 6-10

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