A closed system of the heart and blood vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
Functions of the cardiovascular system
Transport oxygen, nutrients, cell wastes, hormones to and from cells
Heart size and location
Size of a human fist, weighing less than a pound
Located in the thoracic cavity, between the lungs in the inferior mediastinum
Orientation
Apex is directed toward left hip and rests on the diaphragm
Base points toward right shoulder
Pericardium
a double-walled sac
Fibrous pericardium
is loose and superficial
Serous membrane
is deep to the fibrous pericardium and composed of two layers
Parietal pericardium:
outside layer that lines the inner surface of the fibrous pericardium
Visceral pericardium:
next to heart; also known as the epicardium
Serous fluid fills
the space between the layers of pericardium, called the pericardial cavity
Epicardium
Outside layer; the visceral pericardium
Myocardium
Middle layer
Mostly cardiac muscle
Endocardium
Inner layer known as endothelium
Atria (right and left)
Receiving chambers
Assist with filling the ventricles
Blood enters under low pressure
Ventricles (right and left)
Discharging chambers
Thick-walled pumps of the heart
During contraction, blood is propelled into circulation
Interatrial septum
Separates the two atria longitudinally
Interventricular septum
Separates the two ventricles longitudinally
Heart functions as a double pump
Arteries carry blood away from the heart
Veins carry blood toward the heart
Double pump
Right side works as the pulmonary circuit pump
Left side works as the systemic circuit pump
Pulmonary circulation
Blood flows from the right side of the heart to the lungs and back to the left side of the heart
Blood is pumpedā¦
out of right side through the pulmonary trunk, which splits into pulmonary arteries and takes oxygen-poor blood to lungs
Oxygen-rich blood returnsā¦
to the heart from the lungs via pulmonary veins
Systemic circulation
Oxygen-rich blood returned to the left side of the heart is pumped out into the aorta
Blood circulates to
systemic arteries and to all body tissues
Left ventricle has thicker walls becauseā¦
it pumps blood to the body through the systemic circuit
Oxygen-poor blood returns toā¦
the right atrium via systemic veins, which empty blood into the superior or inferior vena cava
Heart Valves
Allow blood to flow in only one direction, to prevent backflow
Atrioventricular (AV) valves
ābetween atria and ventricles
Left AV valve:
bicuspid (mitral) valve
Right AV valve:
tricuspid valve
Semilunar valves
ābetween ventricle and artery
Pulmonary semilunar valve
Aortic semilunar valve
AV valves
Anchored the cusps in place by chordae tendineae to the walls of the ventricles
Open during heart relaxation, when blood passively fills the chambers
Closed during ventricular contraction
Semilunar valves
Closed during heart relaxation
Open during ventricular contraction
Valves open and close in responseā¦
to pressure changes in the heart
Blood in the heart chambersā¦
does not nourish the myocardium
The heart has its own nourishing circulatory system consisting of:
coronary arteries
cardiac veins
coronary veins
Coronary arteries
ābranch from the aorta to supply the heart muscle with oxygenated blood
Cardiac veins
drain the myocardium of blood
Coronary sinus
a large vein on the posterior of the heart; receives blood from cardiac veins
Blood empties intoā¦
the right atrium via the coronary sinus
Two systems regulate heart activity
Autonomic nervous system
Intrinsic conduction system, or the nodal system
Atrioventricular (AV) node isā¦
at the junction of the atria and ventricles
Tachycardia
rapid heart rate, over 100 beats per minute
Tunica intima forms a friction-reducing lining
Endothelium
Tunica externa forms protective outermost covering
Mostly fibrous connective tissue
Supports and protects the vessel
Intrinsic conduction system, or the nodal system does
Sets the heart rhythm
Composed of special nervous tissue
Ensures heart muscle depolarization in one direction only (atria to ventricles)
Enforces a heart rate of 75 beats per minute
Sinoatrial( SA) node
Located in the right atrium
Serves as the heartās pacemaker
Atrioventricular (AV) bundle (bundle of His) and bundle branches
are in the interventricular septum
Purkinje fibers spread
within the ventricle wall muscles
The sinoatrial node (SA node)
starts each heartbeat
Impulse spreads
through the atria to the AV node
Atria
contract
At the AV node,
the impulse is delayed briefly
Impulse travels
through the AV bundle, bundle branches, and Purkinje fibers
Ventricles contract
blood is ejected from the heart
Bradycardia
low heart rate, less than 60 beats per minutes
The cardiac cycle refers to
one complete heartbeat, in which both atria and ventricles contract and then relax
Systole = contraction
Diastole = relaxation
Average heart rate
approximately 75 beats per minute
Cardiac cycle length
normally 0.8 second
Blood vessels form
a closed vascular system that transports blood to the tissues and back to the heart
Vessels that carry blood away from the heart
Arteries and arterioles
Vessels that play a role in exchanges between tissues and blood
Capillary beds
Vessels that return blood toward the heart
Venules and veins
Three layers (tunics)
in blood vessels (except the capillaries)
Tunica media
Smooth muscle and elastic tissue
Controlled by sympathetic nervous system
Arteries have
a heavier, stronger, stretchier tunica media than veins to withstand changes in pressure
Veins have
a thinner tunica media than arteries and operate under low pressure
Veins also have valves to prevent backflow of blood
Lumen of veins is larger than that of arteries
Skeletal muscle āmilksā blood in veins toward the heart
Capillaries
Only one cell layer thick (tunica intima)
Allow for exchanges between blood and tissue
Form networks called capillary beds that consist of:
A vascular shunt
True capillaries
Blood flow through a capillary bed is known as
microcirculation