The Circulatory System
DR—Noha Elsayed
2015--2016
The Circulatory System: Anatomy
• Also called cardiovascular system
– Completely closed
• Two circuits:
– Systemic circulation in body
– Pulmonary circulation in lungs
The Heart
• Muscular organ that pumps blood throughout
the body
• Located behind sternum
• About size of closed fist
• Heart muscle is called myocardium
• Pericardium is membrane surrounding heart
The Heart
• Four chambers:
– Two atria
– Two ventricles
– Each side of the heart contains one atrium and
one ventricle.
• Atria receive blood returned to heart.
• Ventricles pump blood out of heart.
Valves of the Heart
• Tricuspid valve separates
right atrium from right
ventricle
• Mitral valve separates left
atrium from left ventricle
• Pulmonary valve
regulates blood flow
from right ventricle to
pulmonary artery
• Aortic valve regulates
blood flow from left
ventricle to aorta
The Cardiac Cycle
• Process that creates the pumping of the heart
• Systole= Contraction
– Pumping of blood into systemic circulation
• Diastole=Relaxation phase of cycle
The Cardiac Cycle
• Pulse pressure =
systolic pressure − diastolic pressure
• Afterload: pressure in aorta against which left
ventricle pumps blood
• Stroke volume: amount of blood ejected per
contraction
• Cardiac output = stroke volume × heart rate
The Vascular System
• Arteries carry blood away from the heart.
• Veins carry blood back to the heart.
• Arteries branch into arterioles
divide
into
capillaries enlarge
venules merge to form
veins.
The Vascular System
• the heart Supplied by right and left coronary
arteries
• Pulmonary circulation
– Carries blood from right side of heart to lungs
– Carries blood back to left side of heart
– Carries blood from systemic circulation
throughout body
Blood Flow Within the Heart
• Deoxygenated blood returns to the right
atrium via superior vena cava and inferior
vena cava.
• Freshly oxygenated blood returns to the left
atrium through pulmonary veins.
Blood Flow Within the Heart
• Blood flows through mitral valve into the left
ventricle.
• Left ventricle pumps oxygenated blood into
aorta, and then to entire body
The Vascular System
• Systemic arterial
circulation
– Oxygenated blood leaves
heart via the aorta.
– Aorta distributes blood
to all parts of body
• Systemic venous
circulation
– Drains deoxygenated
blood and returns it to
the heart.
– Veins accompany major
arteries, and often have
the same names.
The Circulatory System: Anatomy
Heart Sounds
• Created by contraction and
relaxation of heart and flow
of blood
– Heard during auscultation
with stethoscope
• S1 and S2 are normal
sounds.
– S3 and S4 are not
The Electrical Conduction System
• Electrical stimulus controls mechanical
pumping action
• Conduction system components:
– Sinoatrial (SA) node
– Atrioventricular (AV) node
– Bundle of His
– Right and left bundle branches
– Purkinje fibers
The Electrical Conduction System
Regulation of Heart Function
• Autonomic nervous system, endocrine
hormones, and heart tissue, control:
– Rate of contraction (chronotropic state)
– Rate of electrical conduction (dromotropic state)
– Strength of contraction (inotropic state)
Regulation of Heart Function
• Baroreceptors
– Respond to changes in pressure
• Chemoreceptors
– Sense changes in chemical composition of blood
• Stimulation of receptors affects heart rate and
contractility.
The Circulatory System: Physiology
• Pulse is created by blood
pumping out of left ventricle
into major arteries
• Blood pressure is the pressure
blood exerts against artery
walls.
– Sphygmomano-meter
measures high/low points
The Circulatory System: Physiology
• Systemic vascular resistance is how
dilated or constricted the blood
vessels are.
– Average adult has about 5 L of blood
– Infants 300 mL, children 2 to 3 L
Normal Circulation in Adults
• Circulatory system normally adjusts and
readjusts automatically
• Perfusion is the circulation of blood in an
organ or tissue in adequate amounts.
• Loss of blood pressure means cells, tissues,
and whole organs may die.
– Loss of normal blood indicates blood is no longer
circulating effectively to every organ.
• Shock
– Inadequate circulation involving entire body
Inadequate Circulation in Adults
• Heart automatically adjusts to lower blood
volume as patient loses blood
– Heart attempts to maintain adequate pressure by
constricting vessels
– Heart pumps more rapidly to circulate lower
amount of blood
• Pulse increases as pressure falls.
The Distribution of Blood
• Hydrostatic pressure
– Moves plasma and nutrients from capillaries into
interstitial space
• Oncotic pressure
– Moves plasma and wastes from interstitial space into
capillaries
The Vascular System
The Vascular System
Arteries of the head and neck
Arteries of the upper
extremity
The Vascular System
Branches of the abdominal aorta
The Vascular System
Arteries of the pelvis
and thigh
Arteries of the lower extremity
The Vascular System
Veins of the head and neck
The Vascular System
Veins of the upper extremity
Hepatic portal system
The Vascular System
Veins of the lower extremity