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Transcript of Cardiovascular System
A. Blood pressure is the force of blood against the inner walls of blood vessels anywhere in the cardiovascular system, although the term "blood pressure" usually refers to arterial pressure.
B. Arterial Blood Pressure
1. Arterial blood pressure rises and falls following a pattern established by the cardiac cycle.
C. Factors that Influence Arterial Blood Pressure
1. Heart Action
A. The cardiovascular system consists of the heart, and vessels, arteries, capillaries and veins.
B. A functional cardiovascular system is vital for supplying oxygen and nutrients to tissues and removing wastes from them.
A. The body's blood vessels can be divided into a pulmonary circuit, including vessels carrying blood to the lungs and back, and a systemic circuit made up of vessels carrying blood from the heart to the rest of the body and back.
is made up of vessels that carry blood from the right ventricle to the pulmonary arteries to the lungs, alveolar capillaries, and pulmonary veins leading from the lungs to the left atrium.
C. Systemic Circuit
The systemic circuit includes the aorta and its branches leading to all body tissues as well as the system of veins returning blood to the right atrium.
The heart has four internal chambers, two atria and two ventricles.
a. Atria receive blood returning to the heart and have thin walls and ear-like auricles projecting from their exterior.
b. The thick-muscled ventricles pump blood to the body.
2. A septum divides the atrium and ventricle on each side. Each also has an atrioventricular (A-V) valve to ensure one way flow of blood.
a. The right A-V valve (tricuspid) and left A-V valve (bicuspid or mitral valve) have cusps to which chordae tendinae attach
b. Chordae tendinae are, in turn, attached to papillary muscles in the inner heart wall that contract during ventricular contraction to prevent the backflow of blood through the A-V valves.
3. The superior and inferior vena cavae bring blood from the body to the right atrium.
4. The right ventricle has a thinner wall than the left ventricle because it must pump blood only as far as the lungs, compared to the left ventricle pumping to the entire body.
5. At the base of the pulmonary trunk leading to the lungs is the pulmonary valve, which prevents a return flow of blood to the ventricle.
6. The left atrium receives blood from four pulmonary veins.
7. The left ventricle pumps blood into the entire body through the aorta, guarded by the aortic valve that prevents backflow of blood into the ventricle.
E. Path of Blood through the Heart
1. Blood low in oxygen returns to the right atrium via the venae cavae and coronary sinus.
2. The right atrium contracts, forcing blood through the tricuspid valve into the right ventricle.
3. The right ventricle contracts, closing the tricuspid valve, and forcing blood through the pulmonary valve into the pulmonary trunk and arteries.
4. The pulmonary arteries carry blood to the lungs where it can rid itself of excess carbon dioxide and pick up a new supply of oxygen.
5. Freshly oxygenated blood is returned to the left atrium of the heart through the pulmonary veins.
6. The left atrium contracts, forcing blood through the left bicuspid valve into the left ventricle.
7. The left ventricle contracts, closing the bicuspid valve and forcing open the aortic valve as blood enters the aorta for distribution to the body.
A. The cardiac cycle consists of the atria beating in unison (atrial systole) followed by the contraction of both ventricles, (ventricular systole) then the entire heart relaxes for a brief moment (diastole).
C. Heart Sounds
1. Heart sounds can be described as a "lubb-dupp" sound.
2. The first sound (lubb) occurs as ventricles contract and A-V valves are closing.
3. The second sound (dupp) occurs as ventricles relax and aortic and pulmonary valves are closing.
A. The blood vessels (arteries, arterioles, capillaries, venules, and veins) form a closed tube that carries blood away from the heart, to the cells, and back again.
B. Arteries and Arterioles
1. Arteries are strong, elastic vessels adapted for carrying high-pressure blood.
2. Arteries become smaller as they divide and give rise to arterioles.
1. Capillaries are the smallest vessels, consisting only of a layer of endothelium through which substances are exchanged with tissue cells.
2. The pattern of capillary density also varies from one body part to the next.
a. Areas with a great deal of metabolic activity (leg muscles, for example) have higher densities of capillaries.
D. Exchanges in the Capillaries
1. Blood entering capillaries contains high concentrations of oxygen and nutrients that diffuse out of the capillary wall and into the tissues.
E. Venules and Veins
1. Venules leading from capillaries merge to form veins that return blood to the heart.
Veins are thinner and do not carry high-pressure blood.
a. Systolic Pressure -during ventricular contraction, arterial pressure is at its highest
b. Diastolic Pressure -when ventricles are relaxing, arterial pressure is at its lowest
2. The surge of blood that occurs with ventricular contraction can be felt at certain points in the body as a
a. Heart action is dependent upon stroke volume and heart rate (together called cardiac output); if cardiac output increases, so does blood pressure.
2. Blood Volume
a. Blood pressure is normally directly proportional to the volume of blood within the cardiovascular system.
b. Blood volume varies with age, body size, and gender.
3. Peripheral Resistance
a. Friction between blood and the walls of blood vessels is a force called peripheral resistance.
b. As peripheral resistance increases, such as during sympathetic constriction of blood vessels, blood pressure increases.
4. Blood Viscosity
a. The greater the viscosity (ease of flow) of blood, the greater its resistance to flowing, and the greater the blood pressure.
The Arterial System!
A. The aorta is the body's largest artery.
1. Principal branches of the aortic arch include the brachiocephalic, left common carotid, and left subclavian arteries.
2. The abdominal aorta gives off the following branches: celiac, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric
and common iliac arteries.
C. Arteries to the Head, Neck, and Brain
1. include branches of the subclavian and common carotid arteries.
2. In the cranial cavity, the vertebral arteries unite to form a basilar artery, which ends as two posterior cerebral arteries.
The posterior cerebral arteries help form the circle of Willis, which provides alternate pathways through which blood can reach the brain.
4. The right and left common carotid arteries diverge into the external carotid and internal carotid arteries.
D. Arteries to the Shoulder and Upper Limb
1. The subclavian artery continues into the arm where it becomes the axillary artery.
2. In the shoulder region, the axial artery becomes the brachial artery that, in turn, gives rise to the ulnar and radial arteries.
1. The abdominal aorta bifurcates into the common iliac arteries
2. The common iliac arteries divide into internal and external iliac arteries.
a. Internal iliac arteries supply blood to pelvic muscles and visceral structures.
b. External iliac arteries lead into the legs, where they become femoral, popliteal, anterior tibial and posterior tibial arteries.
The Venous System
A. Veins return blood to the heart after the exchange of substances has occurred in the tissues.
B. Characteristics of Venous Pathways
1. Larger veins parallel the courses of arteries and are named accordingly; smaller veins take irregular pathways and are unnamed.
2. Veins from the head and upper torso drain into the superior vena cava.
3. Veins from the lower body drain into the inferior vena cava.
4. The vena cavae merge to join the right atrium.
C. Veins from the Upper Limb and Shoulder
1. The upper limb is drained by superficial and deep veins.
2. The basilic and cephalic veins are major superficial veins.
3. The major deep veins include the radial, ulnar, brachial, and axillary veins.
Veins from the Lower Limb and Pelvis
1. Deep and superficial veins drain the leg and pelvis.
2. The deep veins include the anterior and posterior tibial veins, which unite into the popliteal vein and femoral vein; superficial veins include the small and great saphenous veins.
3. These veins all merge to empty into the common iliac veins.
1. Stroke volume: The amount of blood pumped by the left ventricle of the heart in one contraction.