The Heart n The heart is a coneshaped
- Slides: 29
The Heart n The heart is a cone-shaped, muscular organ n The heart muscle forms the myocardium, with tightly interconnected cells of cardiac muscle tissue. n The pericardium is the outer membranous sac with lubricating fluid.
n n The heart has four chambers: two upper, thinwalled atria, and two lower, thick-walled ventricles. The septum is a wall dividing the right and left sides. Atrioventricular valves occur between the atria and ventricles – the tricuspid valve on the right and the bicuspid valve on the left; both valves are reinforced by chordae tendinae attached to muscular projections within the ventricles. Semilunar valves occur between the ventricles and the attached arteries
External heart anatomy
External heart anatomy
Coronary artery circulation
Path of blood through the heart
Conduction system of the heart
Conduction and Contraction n SA node in right atrium is pacemaker n Electrical signals cause contraction of atria n Signal flows to AV node and down septum to ventricles SA node
The Heartbeat heartbeat is called a cardiac cycle. n When the heart beats, the two atria contract together, then the two ventricles contract; then the whole heart relaxes. n Systole is the contraction of heart chambers; diastole is their relaxation. n The heart sounds, lub-dup, are due to the closing of the atrioventricular valves, followed by the closing of the semilunar valves. n Each
Electrocardiogram
The Vascular Pathways The cardiovascular system includes two circuits: 1) Pulmonary circuit which circulates blood through the lungs, and 2) Systemic circuit which circulates blood to the rest of the body. 3) Both circuits are vital to homeostasis. n
Pulmonary Circuit right pulmonary artery This loop oxygenates blood capillary bed of right lung left pulmonary artery capillary bed of left lung pulmonary trunk (to systemic circuit) (from systemic circuit) pulmonary veins heart lungs
Systemic Circuit Longer loop carries blood to and from body tissues capillary beds of head and upper extremities (to pulmonary circuit) aorta (from pulmonary circuit) heart capillary beds of other organs in thoracic cavity capillary bed of liver capillary beds of intestines capillary beds of other abdominal organs and lower extremities
Cardiovascular system diagram
The Blood Vessels n The cardiovascular system has three types of blood vessels: n Arteries (and arterioles) – carry blood away from the heart n Capillaries – where nutrient and gas exchange occur n Veins (and venules) – carry blood toward the heart.
Blood vessels
The Arteries n Arteries and arterioles take blood away from the heart. n The largest artery is the aorta. n The middle layer of an artery wall consists of smooth muscle that can constrict to regulate blood flow and blood pressure. n Arterioles can constrict or dilate, changing blood pressure.
The Capillaries n Capillaries have walls only one cell thick to allow exchange of gases and nutrients with tissue fluid. n Capillary beds are present in all regions of the body but not all capillary beds are open at the same time.
Anatomy of a capillary bed
n The Veins Venules drain blood from capillaries, then join to form veins that take blood to the heart. n Veins have much less smooth muscle and connective tissue than arteries. n Veins often have valves that prevent the backward flow of blood when closed. n Veins carry about 70% of the body’s blood and act as a reservoir during hemorrhage.
The Venous System n Blood flows from capillaries into venules, then on to veins n Veins are large-diameter vessels with some smooth muscle in wall n Valves in some veins prevent blood from flowing backward
n Changes in thoracic and abdominal pressure that occur with breathing also assist in the return of blood. n Varicose veins develop when the valves of veins become weak. n Hemorrhoids (piles) are due to varicose veins in the rectum. n Phlebitis is inflammation of a vein and can lead to a blood clot and possible death if the clot is dislodged and is carried to a pulmonary vessel.
Major Vessels carotid arteries jugular veins superior vena cava pulmonary veins hepatic portal vein renal vein inferior vena cava iliac veins femoral vein ascending aorta pulmonary arteries coronary arteries brachial artery renal artery abdominal aorta iliac arteries femoral artery
Atherosclerosis n Atherosclerosis is due to a build-up of fatty material (plaque), mainly cholesterol, under the inner lining of arteries. n The plaque can cause a thrombus (blood clot) to form. n The thrombus can dislodge as an embolus and lead to thromboembolism.
Coronary bypass operation
Angioplasty
Atherosclerosis n Arteries thicken, lose elasticity, and fill up with cholesterol and lipids n High LDL increases risk
Up in Smoke n The vast majority of smokers picked up the habit before age 18 n Smoking damages the circulatory and respiratory systems n Smokers have increased risk of respiratory infections, cancers, high blood pressure, stroke, and heart attack
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