Transcript The Cardiovascular System

 Provides oxygen and nutrients to
tissues
 Removes wastes
 FYI
 Pumps 7,000 liter per day
 Beats 2.5 Billion times in your lifetime
 Hollow, cone-shaped
 Lies within thoracic cavity
 Rests on diaphragm
 Average Size
 14cm long and 9cm wide
 Enclosed by layered pericardium
 Visceral – inner layer
 Parietal – outer layer
 Pericardial Cavity
 Space between the parietal and visceral
layers of the pericardium
 Pericarditis
 Inflammation of pericardium
 Adhesions cause layers of pericardium
to attach to each other
 Very painful
 Interferes with heart movements
 Epicardium
 Outer layer
 Visceral pericardium
 Protects heart
 reduces friction
 Myocardium
 Middle layer
 Pumps blood out of heart chambers
 Endocardium
 Inner layer
 Two atria
 Upper chambers
 Receive blood returning to heart
 Two ventricles
 Lower chambers
 Receive blood from atria
 Contract to force blood out of heart
 Right atrium
 receives blood from inferior vena cava, superior vena
cava and coronary sinus
 Tricuspid valve
 Separates right atrium from right ventricle
 Prevents back flow when ventricle contracts
 Chordae Tendineae
 Right Ventricle
 Pumps blood to lungs
 Thin walls
 Pulmonary Valve
 Sends blood through pulmonary arteries to lungs
 Left Atrium
 Receives blood from lungs
 Arrives through pulmonary veins
 Mitral Valve
 Biscuspid valve
 Left Ventricle
 Aorta
 Aortic valve
 Fibrous rings enclose base of pulmonary artery
and aorta
 Attachments for heart valves and muscle fibers
 Prevent chambers from dilating during
contraction
 Blood Supply
 Coronary arteries
 First two branches of aorta
 Supply blood to myocardium
 Returns through cardiac veins and coronary
sinus
 Mitral Valve Prolapse
 Blood gets back into atrium during ventricular
contraction
 Chest pain, palpitations, fatigue and anxiety
 Often caused by Streptococcus bacteria
 Angina Pectoris
 Narrowing of coronary arteries
 Deprives heart cells of oxygen
 Heavy pressure, tightening or squeezing of chest
 Myocardial Infarction
 Heart attack
 Blood clot obstructs artery and kills part of heart
 Cardiac Cycle
 Atria contract (systole) while ventricles relax
(diastole)
 Ventricles contract while atria relax
 Both relax for brief interval
 Due to vibrations the valve movements produce
 Lubb-Dubb
 Lubb
 Ventricular contractions
 A-V valves closing
 Dubb
 Ventricular Relaxation
 Pulmonary and Aortic valves closing
 Edges of valves erode away and don’t close
completely
 Blood leaks back through the valve
 Can be caused by endocarditis (inflammation of
endocardium)
 Repaired through open heart surgery
 Functional Syncytium
 Mass of merging cells that function as a unit
 We have atrial syncytium and ventricular syncytium
 If any part of the syncytium is stimulated, the whole
structure contracts as a unit
 Initiates and conducts impulses throughout the
myocardium
 Begins in Sinoatrial Node (S-A Node)
 Located under right atrium
 Fibers continuous with atrial syncytium
 Cells reach threshold on their own
 Membranes contract
 Rhythmic
 70-80 times/minute
 Pacemaker
 Impulse travels from S-A Node to atrial syncytium
 Right and left atria contract
 Impulse goes to Atrioventricular Node (A-V Node) by
way of junctional fibers
 Impulse enters A-V bundle
 This bundle gives way to Purkinje Fibers
 Gives way to twisting contraction of ventricles
 Records electrical changes in myocardium during a
cardiac cycle
 Body fluids conduct electrical currents
 P wave
 Atrial depolarization
 QRS Complex
 Ventricular depolarization
 T wave
 Ventricular repolarization
 Parasympathetic Fibers
 Braking Action
 Nerve impulse reach fiber endings and secrete
acteylcholine
 Decreases S-A and A-V node activity
 Increase in impulses – decreased heartrate
 Decrease in impulses – increased heartrate
 Sympathetic Fibers
 Secrete norepinephrine
 Increases rate and force of myocardial
contractions
 Cardiac Center
 Located in Medulla Oblongata
 Keeps balance between sympathetic and
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parasympathetic impulses
Baroreceptors control blood pressure – rising pressure
lowers heart rate – lowers blood pressure
Fainting – decreases heart rate
Anxiety – increases heart rate
Temperature – increase in temp increases heart rate
Potassium – too much decreases rate and force of
contractions
Calcium – too much increases heart actions
 Closed circuit of tubes that carry blood from heart
to cells and back
 Include arteries, arterioles, capillaries, venules and
veins
 Human body has 62,000 miles
 Can circle globe 2 ½ times
 Arteries
 Strong, elastic vessels
 Adapted to carry blood at high pressure
 Branch and subdivide into arterioles
 Made of 3 layers
 Tunica interna
 Tunica media
 Tunica externa
 Vasoconstriction – arteries contract – get smaller
 Vasodilation – arteries relax – get larger
 These two functions influence blood flow and blood
pressure
 Connect arterioles and venules
 Wall is single layer of cells that forms a semipermeable
membrane
 Gas, nutrient and waste exchange occurs here
 Openings in walls vary from tissue to tissue
 Smaller in muscles
 Larger in endocrine glands, kidneys and small intestines
 Density varies with cellular needs
 Muscle and nerves have high need for nutrients – so
they have many capillaries
 Cartilage, epidermis and cornea – no need – no
capillaries
 Precapillary Sphincters
 Regulate blood flow
 During exercise muscle cells have most need so they get
the most blood- digestive system capillaries close
because they aren’t really working at that time
 Capillary blood and tissue fluid exchange gases, nutrients,
and metabolic by-products
 Diffusion provides the most important means of transport
 Filtration, which is due to hydrostatic pressure of blood,
causes a net outward movement of fluid at the arteriorlar
end of a capillary
 Osmosis due to colloid osmotic pressure causes a net
inward movement of fluid at the venular end
 Venules
 Microscopic vessels that continue
from capillary and merge to form veins
 Veins
 Carry blood back to heart
 Made of three layers but middle layer is weak
 Don’t have to be as strong because blood pressure is lower
 Have valves to keep blood moving in right direction
 Serve as reservoirs
 Up to 25% of blood here
 Blood pressure is the force blood exerts against the
insides of blood vessels
 Rises and falls with phases of cardiac cycle
 Systolic pressure
 Ventricle contracts
 Top number – should be <120
 Diastolic pressure
 Ventricle relaxes
 Bottom number – should be <80
 Heart Action
 Stroke volume – amount discharged with each
contraction – 70ml for average male at rest
 Cardiac Output – volume discharged per minute
 If these number go up – so does blood pressure
 Blood Volume
 Approximately 5 liters (8% of body weight)
 More blood – higher blood pressure
 Peripheral Resistance
 Friction between blood and walls of blood
vessels
 More friction – higher blood pressure
 Plaque build-up in arteries
 Blood Viscosity
 Thicker blood – higher blood pressure
 Controlled by the mechanisms
that regulate cardiac output and
peripheral resistance
 More blood enters heart
stronger contraction
greater stroke volume and
greater cardiac output
 Little pressure left after blood moves through
arteries, arterioles and capillaries
 Depends on
 Skeletal muscle contractions – when muscles
contract blood in veins gets pushed from one
valve reservoir to the next
 Respiratory movements – when rib cage expands
applies pressure on abdominal veins and blood
gets pushed from abdominal veins into thoracic
veins
 Venoconstriction – if blood is lost veins
contract, empty reservoirs and push blood back
to heart.
 Pulmonary Circuit
 Consists of vessels that carry blood from the
right ventricle to the lungs and back to the left
atrium
 Systemic Circuit
 Consists of vessels that lead from the heart to
the body cells (including the heart itself) and
back to the heart
 Includes the aorta and its branches