heart. closed circulation blood never leaves vessels blood never leaves vessels
Post on 01-Jan-2016
226 Views
Preview:
TRANSCRIPT
Heart
Closed Circulation
Blood never leaves vessels
Double Circulatory System
- In mammals, birds and reptiles, the blood is pumped twice before returning to its origin
- Fish, and other lower organisms pump the blood only once
Four Chambered Heart
oxygenated and deoxygenated blood do not mix in the heart
septum separates the right and left sides
Heart Chambers
The top chambers are called atria (sing. Atrium)
These collect blood from major veins and pump it into the bottom chambers
Ventricles
Much larger and more muscular than atria
Pump blood into arteries for distribution to body (and lungs)
Vessels Arteries – carry blood away from
heart
Veins – carry blood toward heart
Systemic circulation – blood flow to and from body organs (not lungs)
Pulmonary circulation – blood flow to and from lungs
Heart
How the Heart Works
Atrioventricular Valves Separate the atria and ventricles
Atrioventricular valves have:– Chordae tendinae
prevent flaps from everting (opening backward)
– Papillary muscles to attach chordae tendinae to ventricle wall
The Bicuspid Valve (AV)
Also called the mitral valve
On the left side of the heart
Has two flaps
Tricuspid Valve (AV)
On the right side Has three flaps
Semilunar Valves
At the entrance to the major arteries are smaller valves with no muscular attachments
These have three flaps each and prevent backflow into the ventricles
Valve movie
http://www.wellesley.edu/Biology/Courses/111/HeartValves.MOV
Video
How a Normal Heart Pumps Blood
Pericardium
Membrane around heart which prevents friction between heart and lungs
Also helps isolate infection
Coronary Arteries
The aorta branches and one of the branches comes back to serve the heart muscle (myocardium)
Coronary Circulation
These arteries can become blocked with plaque (cholesterol and calcium deposits) and clots can occur causing:
– pain: angina pectoris– Heart muscle death: myocardial
infarction (heart attack)
Coronary Circulation
Risks for Heart Disease
Genetics Male Smoking Obesity Diet (saturated
fat and cholesterol)
Lack of exercise
Heart Beats
Cardiac Muscle: striated, branched
Is myogenic muscle: can contract without nerve impulse
Heart Beats
Chemoreceptors in aorta and carotid (neck) arteries detect high carbon dioxide levels in blood (lesser extent – oxygen is also monitored)
nerves carry this information to the heart
Heart Beats
The heart beat is controlled by the sympathetic (stimulating) and parasympathetic (relaxing) branches of the nervous system.
Heart Beats
Tempo is set by the sinoatrial node (SA node) : the pacemaker
Heart Beats
Electrochemical impulses from the S.A. node cause contraction of atria muscle
Heart Beats
the impulse travels to another cluster of nervous tissue – the Atrioventricular node (A.V. node)
Heart Beats
The A.V. node sends impulses through Purkinje fibers to all parts of the ventricles
Ventricles contract simultaneously
Heart Beats Heart muscle then ‘rests’ before the
cycle begins again
‘systole’ – phase of heart contraction
‘diastole’ – phase of heart relaxation
‘lub – dub’ – heart sounds caused by valves slamming shut
Heart Beats
Normal Heart Rate – 80 beats/minute
Bradycardia - < 50 beats/min
Tachycardia - > 100 beats/min
Monitoring Heart Beat
EKG (or ECG) – electrocardiogram Uses electrical activity in heart
muscle to diagnose problems
EKG
P wave – depolarization preceding atrial contraction
QRS complex – precedes ventricular T wave – repolarization of
myocardium
Ventricular Fibrillation
Defibrillator
Used to shock hearts into proper rhythm
Other Abnormal Rhythms
tachycardia
Bradycardia
Heart Technology
stethescope
Heart Technology
Artificial pacemakers – use batteries to produce a coordinated signal when ‘real’ pacemaker malfunctions
Heart Technology
Valve Replacement : routinely done to fix valves scarred by infections, etc.
Cardiac Catheterization a thin catheter is inserted into a
blood vessel, usually an artery in the leg or arm, and passed through the blood vessel to the heart.
Dye is injected to make the coronary arteries and other structures visible on X-rays.
Heart Technology
Angioplasty: using a catheter and ‘balloon’ to open up blocked arteries
Heart Technology
Coronary bypass: heart operation to use a vein from leg to bypass blockage
Heart Transplant
Often miraculous results
Shortage of organs
Person must take immunosupressants for life
Xenotransplants
Dismal failures when whole heart is transplanted
Pig arteries and valves have been used for years
New genetic research hopes to produce pigs with human proteins
Artificial Heart
Some success as a bridge to transplant
top related