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Cardiovascular System

Cardiovascular System. Mr. N euberger. Cardiac muscle. Constitutes most of the heart Striated like skeletal muscle Cardiocytes are not long multinucleated fibers but short, stumpy, slightly branched cells Contain dark lines called intercalated discs

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Cardiovascular System

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  1. Cardiovascular System Mr. Neuberger

  2. Cardiac muscle • Constitutes most of the heart • Striated like skeletal muscle • Cardiocytes are not long multinucleated fibers but short, stumpy, slightly branched cells • Contain dark lines called intercalated discs • Contain electrical gap junctions that allow cells to communicate with each other and not pull apart during contraction • i.e. the cells are holding hands • Very rich in glycogen and myoglobin, mitochondria so large that it fills 25% of the cell • Very well adapted to aerobic respiration and very resistant to fatigue

  3. Cardiac Muscle • Sarcoplasmic Reticulum is less developed than in skeletal muscle but the T Tubules are larger • Allow electrical signal to disperse faster as well as provide calcium for contraction • Innervated by the Autonomic Nervous System • Operates without our conscious control • Does not generate the heartbeat but rather modulate the heart rate and contraction strength • Cardiocytes pulsate rhythmically even without nervous stimulation- Autorhythmicity

  4. The Heart • Cardiology- a field that embraces the study of the heart • The cardiovascular system has two major divisions: • Pulmonary Circuit- Carries blood to the lungs for gas exchange and returns it to the heart • Systemic Circuit- Supplies blood to every organ of the body (including parts of the lung and the walls of the heart)

  5. Right Side • The right side of the heart serves as the pulmonary circuit • Receives blood that has circulated through the body and pumps it into the large artery called the Pulmonary Trunk • From here the oxygen-poor blood is distributed to the lungs • Unloads carbon dioxide and picks up oxygen • Returns blood to the left side of the heart by way of the pulmonary veins

  6. Left Side • Serves as the Systemic Circuit • Pumps blood into the largest artery in the body, Aorta • Gives of branches that deliver oxygen to every organ of the body and picks up carbon dioxide and other wastes • After the gas exchange, the blood returns to the heart by way of the body’s two largest veins: Superior vena cava (drains the upper body), Inferior vena cava (drains everything below the diaphragm • The pulmonary trunk, pulmonary veins, aorta, and two vena cava- called The Great Vessels

  7. Position, Size, and Shape • Located in the thoracic cavity, between the lungs and deep to the sternum • Superior to inferior midpoints, it is tilted towards the left • 2/3 of the heart lies to the left of the medial plane • Broad superior portion of the heart, Base, is the point of attachment for the great vessels • Inferior end tapers to a blunt point, apex, immediately above the diaphragm • Your heart is the same size as your fist, roughly

  8. The Pericardium • The heart is enclosed in a double-walled sac called the Pericardium • The outer wall, called the Pericardial sac, has a tough, superficial fibrous layer of dense irregular connective tissue and a deep, thin serous layer • The serous layer turns inward at the base of the heart and forms the Epicardium, covering the heart surface • The pericardial sac is anchored by ligaments to the diaphragm below and the sternum anterior to it • More loosely anchored by fibrous connective tissue to mediastinal tissue posterior to the heart

  9. The Pericardium • The space between the parietal and visceral membranes is called the Pericardial cavity • Contains Pericardial fluid, released by the serous pericardium • Lubricates the membranes and allows the heart to beat with minimal friction • The pericardium separates the heart from other thoracic organs and allows it room to expand, yet resist excessive expansion

  10. The Heart Wall • Consists of three layers • Epicardium, Myocardium, Endocardium • Epicardium- serous membrane on the heart surface • Simple squamous epithelium overlying a thin layer of areolar tissue, some areas of the heart will have a layer of adipose tissue as well • Endocardium- lines the interior of the heart chambers, composed of simple squamous epithelium overlying a thin areolar tissue. No adipose tissue

  11. Myocardium • Performs the work of the heart • Thickness is proportionate of the workload of the individual heart chambers • Consists primarily of cardiac muscle, spirals around heart • Heart twists as it contracts • Fibrous Skeleton- meshwork of collagenous and elastic fibers, esp. concentrated in between the heart chambers • Fibrous rings • Purposes- (1) Provides structural support for heart, (2) anchors the myocytes, (3) Electrical insulation, (4) refills heart with blood after each beat

  12. The Chambers • Two at superior pole- Right, Left Atria • Thin-walled receiving chambers for blood returning to the heart by way of the great veins • Auricle- increases the volume • Inferior heart chambers- Right, Left Ventricles • Eject blood into the arteries and keep it flowing • On the surface of the heart, the 4 chambers are marked by three sulci (grooves), largely filled with fat and coronary blood vessels

  13. The Valves • Must have a predominantly one-way flow • One at each valve between each atrium and the corresponding ventricle and another at the exit from each ventricle into its great artery • 2-3 fibrous flaps of tissue called Cusps or leaflets covered with endocardium • Atrioventricular (AV) Valves- regulate the openings between the atria and ventricles • Right AV Valve- three cusps • Left AV Valve (Mitral Valve)- two cusps

  14. The Valves • StringlikeTendinous cords connect the valve cusps to conical papillary muscles on the floor of the ventricle • Semilunar Valves regulate the flow of blood from the ventricles into the great arteries. • Pulmonary Valve controls the opening from the right ventricle into the pulmonary trunk • Aortic Valve controls the opening from the left ventricle into the aorta

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