Cardiovascular System: The Heart. FUNCTIONS OF THE CARDIOVASCULAR SYSTEM.
Cardiovascular System
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Transcript of Cardiovascular System
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CIRCULATORY SYSTEM
Mr. Jeremy Schriner
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The Heart
4 chambers Located between the
lungs 2/3 of heart left of
midline Apex points downward
& contacts the diaphragm
It lies in the pericardial cavity
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The Heart
It is separated from the other organs by a double-layered membrane = Pericardium
The Pericardium is composed of a Fibrous Pericardium & a Serous Pericardium. The serous pericardium has 2 parts: 1. Parietal layer - attached to the back of the fibrous
pericardium 2. Visceral layer (epicardium) - attached to the heart
muscle These two are separated by a fluid filled space = pericardial
cavity.
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The Heart Wall
A. Epicardium - outermost, = Visceral layer of the serous pericardium
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Heart Wall
B. Myocardium - middle, = Cardiac muscle cells (very thick)
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The Heart Wall
C. Endocardium - innermost, forms valves, & is continuous with the endothelium of the blood vessels that enter & leave the heart
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Chambers
4 chambers 2 upper: Lt. & Rt. Atrium 2 lower: Lt. & Rt.
Ventricle
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Valves
4 valves 2 Atrioventricular (AV)
Valves Rt. AV valve = tricuspid Lt. AV valve = bicuspid,
mitral
2 semilunar valves: found at the base of 2 large vessels leaving the heart = Pulmonary & Aortic valves
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Blood Flow
1. Rt. Atrium: receives deoxygenated (venous) blood from 3 vessels;
A. Superior vena cava - blood from above the heart
B. Inferior vena cava - blood from below the heart
C. Coronary sinus - blood from the heart muscle
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Blood Flow
2. Blood flows through Rt. AV valve into Rt. Ventricle (the flaps of AV valves are held in place by Chordae Tendineae & Papillary Muscles to prevent back flow)
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Blood Flow
3. Rt. Ventricle contracts & blood exits through the Pulmonary Semilunar valve. It enters the Pulmonary trunk which divides into Lt. & Rt. Pulmonary arteries. Blood goes to lungs (carbon dioxide out, oxygen in)
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Blood Flow cont.
4. Oxygenated blood returns from the lungs through the Pulmonary veins to the Lt. Atrium
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Blood Flow
5. Blood flows through the Lt. AV valve (bicuspid, mitral) to the Lt. Ventricle
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Blood Flow
6. Lt. Ventricle contracts & blood exits through the Aortic Semilunar valve & enters Ascending Aorta.
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Coronary circulation (Blood flow to Heart Muscle) First vessels off of the
Ascending Aorta = Lt. & Rt. Coronary Arteries
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Coronary Circulation cont.
The blood returns from the heart muscle via 2 major veins 1. Great Cardiac vein: brings
deoxygenated blood back from the anterior heart wall
2. Middle Cardiac vein: brings deoxygenated blood back from the posterior heart wall.
Both vessels empty into the Coronary Sinus (a large vein on back of heart). It empties into Rt. Atrium
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Conduction system
An electrical system. It determines the rate & rhythm of the heartbeat
1. Sinoatrial node (SA node,
pacemaker) - Neurons fire at 70/80 beats per minute, causes atria to contract
2. Atrioventricular node (AV node) - neurons fire at 40-50 beats per minute; typically the SA node overrides it, but if SA node is not functioning it will ultimately cause ventricles to contract at a slower rate.
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Conduction System
3. Atrioventricular Bundle (Bundle of His) - conducts impulses between ventricles
4. The AV Bundle divides into lt & rt Bundle Branches which go to the ventricles.
5. Purkinje fibers - deliver impulses directly to the
myocardium of the ventricles.
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Blood – connective tissue with fluid matrix A. Fluid = plasma B. Blood cells = formed
elements 1. Red blood cells (RBC's)
= ERYTHROCYTES a. Flattened, biconcave,
anucleated discs b. Life span - 120 days c. Function: transport
oxygen & carbon dioxide bound pigmented protein = hemoglobin
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Blood cont.
2. White blood cells (WBC's) = LEUKOCYTES a.granulocytes
i. eosinophils ii. Basophils iii. Neutrophils
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Blood cont.
2. White blood cells (WBC's) = LEUKOCYTES b. Agranulocytes
i. Monocytes ii. Lymphocytes
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Blood cont.
3. Thrombocytes = PLATELETS; not cells. Cytoplasmic fragments of megakaryocytes. Assists in blood clot formation.
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Hemopoiesis = Blood Cell formation. Occurs in red bone marrow. A. Erythropoiesis =
RBC formation B. Leukopoiesis = WBC
formation C. Thrombopoiesis =
platelet formation
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Blood vessels: blood flow
Blood flows from the heart through progressively narrowing vessels; artery ->arteriole -> capillary
And returns through progressively enlarging vessels;
venules -> vein-> heart
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Blood vessels Structure: arteries and veins
have 3 tunics 1. Tunica Externa (adventitia)
- Outermost, loose connective tissue, this is the thickest layer in veins
2. Tunica Media - middle, smooth muscle layer, this is the thickest layer in arteries
3. Tunica Intima - innermost a. Endothelium - simple
squamous + c.t. b. Subendothelial layer - c.t.
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Arteries (carry blood away from heart) Elastic - large amount
of elastin expandable Muscular - tunica media
is predominantly smooth muscle.
There is an elastic lamina on each face of the tunica media
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Arterioles -
Smallest, tunica media very thin (<10 layers)
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Capillaries
"Functional units" of circulatory system, very thin-walled, allows for exchange of gases, nutrients, & waste products.
Composed of the Tunica Intima only
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Venules
Usually lack a tunica media. They have the other two tunics
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Veins
Carry blood to the heart) All 3 tunics present. Veins have a very
Low pressure, The blood flow through them is dependent on: A. Contraction of
surrounding musculature = Skeletal muscle "pump"
B. One-way valves
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