Transcript Heart and Blood Vessels

Heart and Blood Vessels
Jugular vein
Carotid artery
Superior
vena cava
Inferior
vena cava
Renal vein
Common
iliac vein
Common
iliac artery
Subclavian vein
Subclavian artery
Aorta
Renal artery
Femoral vein
Femoral artery
Great saphenous vein
Figure 8.9
Three Types of Blood Vessels
Transport Blood
• Arteries
– Carry blood away from heart
– Blood under high pressure
• Capillaries
– Metabolic exchange with tissues
• Veins
– Return blood to heart
– Very low pressure
Arteries
• Structure
– Thick-walled, three layers
• Innermost: endothelium
• Middle smooth muscle
• Outer: connective tissue
• Branch into arterioles
– Small arteries
Arterioles and Precapillary Sphincters
– Blood flow
• Heart → Arteries → Arterioles → Capillaries
– Precapillary sphincters: control flow into capillaries
• Vasodilation: increases blood flow to capillaries
• Vasoconstriction: decreases blood flow to capillaries
Capillaries
• Structure
– Smallest blood vessels
– Thin-walled: one cell-layer thick
– Porous
• Function: exchange of substances with interstitial
fluid
Veins
• Structure
– Three layers, thin-walled
– Larger lumen than arteries
• Functions
– Serve as blood reservoirs
– Blood flow
• Capillaries → Venules → Veins
→ Heart
Venous Return to the Heart
• Mechanisms in blood return
– Contraction of skeletal
muscles
– One-way valves
– Pressure changes associated
with breathing
The Heart - Layers
• Surrounded by fibrous sac – pericardium
• Layers of the heart
– Epicardium: thin covering
– Myocardium: cardiac muscle
– Endocardium: thin lining
Heart Chambers
• Four chambers
– Right atrium
– Left atrium
– Right ventricle
– Left ventricle
Heart Vessels
• Superior and inferior vena cava
– Carry low-oxygen blood into RA
from body
• Pulmonary trunk and arteries
– Carry low-oxygen blood from RV to
lungs
• Pulmonary veins
– Carry high-oxygen blood from lungs
to LA
• Aorta
– Carries high-oxygen blood from LV
to body
Aorta
L. Pulmonary Artery
Superior
vena cava
Pulmonary
trunk
R. Pulmonary Artery
Inferior
vena cava
Heart Valves
• Prevent backflow
– Two atrioventricular valves
• Tricuspid valve
– Between RA and RV
• Mitral (bicuspid) valve
– Between LA and LV
– Two semilunar valves
• Pulmonary valve
– Between RV and pulmonary trunk
• Aortic valve
– Between LV and aorta
Two Circuits of Circulation
• Pulmonary circuit
– RV  Pulmonary trunk/arteries
lungs (oxygen)  pulmonary
veins  LA
• Systemic circuit
– LV  aorta  arteries of body 
capillaries  veins  SVC and IVC
 RA
Cardiac Cycle
• Atrial systole
– Both atria contract
– AV valves open, semilunar valves closed
– Ventricles fill
• Ventricular systole
– Both ventricles contract
– AV valves close, semilunar valves open
– Blood flows into arteries
• Diastole
– Both atria and ventricles relax
– Semilunar valves close
Heart Sounds and Heart Valves
• Lub-dub heart sound
– Lub: closing of AV valves during ventricular systole
– Dub: closing of semilunar valves during ventricular
diastole
• Heart murmurs
– Caused when blood flow is disturbed
– May be a sign of a defective valve
Cardiac Conduction System
• SA node
– Cardiac pacemaker
– Initiates heartbeat
– Pace can be modified by nervous system
• AV node
– Relays impulse
• AV bundle and Purkinje fibers
– Carry impulse to ventricles
Electrocardiogram (EKG/ECG)
• Tracks electrical activity of heart
• Characteristic pattern
– P wave: impulse across atria
– QRS complex: spread of impulse thru septum and ventricles
– T wave: end of electrical activity in ventricles
• EKGs can detect
– Arrhythmias
– Ventricular fibrillation
Blood Pressure
• Force blood exerts on walls of blood vessels
– Systolic pressure – highest pressure, during ventricular systole
– Diastolic pressure – lowest pressure, during ventricular diastole
• Measurement
– Use sphygmomanometer
– “Normal” readings
• Systolic pressure <120 mmHg
• Diastolic pressure <80 mmHg
Blood Pressure
• Hypertension: high blood pressure
– The silent killer
– At risk for stroke, heart attack, bleeding, kidney disease
• Hypotension: blood pressure too low
– Inadequate blood supply to organs
– Clinical signs – dizziness, fainting
– Causes – orthostatic, severe burns, blood loss
Regulation of Blood Pressure
• Baroreceptors: pressure receptors in arteries
• Steps in mechanism:
1. Blood pressure rises, vessels stretched
2. Signals sent to cardiovascular center in medulla
oblongata
3. Heart signaled to lower rate and force of contraction
4. Arterioles vasodilate, reducing resistance to blood flow
5. Combined effect lowers blood pressure
Regulation by Nervous and Endocrine
Systems
• Medulla oblongata signals
– Sympathetic nerves – constrict blood vessels, raise blood
pressure
– Parasympathetic nerves – dilate blood vessels, lower
blood pressure
• Hormones: epinephrine (adrenaline) triggers
sympathetic response
• Local requirements dictate local blood flow
• Exercise – increased blood flow and cardiac output
Cardiovascular Disorders
• Angina pectoris: chest pain
– narrowed coronary arteries impair blood flow
• Myocardial infarction/heart attack: permanent
cardiac damage due to blockage in a coronary
artery
• Congestive heart failure: decrease in pumping
efficiency
• Embolism: blockage of blood vessels
• Aneurysm: ballooning of artery
– due to hypertension, hardening of arteries
(atherosclerosis)
• Stroke: impaired blood flow to the brain
Heart Attack
• Also known as myocardial infarction
– Permanent damage to myocardium
• Symptoms
– Intense chest pain, nausea, heaviness in the chest,
difficulty breathing, pain radiating to left arm, jaw, back,
upper abdomen
• Diagnosis
– EKG
– Blood test for cardiac enzymes
• Prevention/Treatment
– Clot-busting medications
– CABG (bypass)
Aorta
Vein
grafts
Plaque
blocking
blood flow
Figure 8.19
Reducing Risk of Cardiovascular
Disease
•
•
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Smoking – don’t
Blood lipids – monitor cholesterol levels
Exercise – regular and moderate
Blood pressure – treat hypertension
Weight – being overweight increases risk of heart
attack and stroke
• Control of diabetes mellitus – early diagnosis and
treatment delays onset of related problems
• Stress – avoid chronic stress