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Circulatory system and the blood
Chapters 5 and 6
Circulatory system
PREVENTS CELLS FROM SUFFOCATING
BRINGS CELLS OXYGEN AND NUTRIENTS
Also called the cardiovascular system
PATHWAYS
HEART- PUMPS BLOOD
ARTERIES- CARRY BLOOD AWAY FROM THE HEART
VEINS- CARRY BLOOD TOWARD THE HEART
CAPILLARIES- TINY VESSELS THAT REACH SINGLE CELLS- THE SITE WHERE EXCHANGE OCCURS
ARTERIES
WALL- have 3 LAYERS INNER- simple squamous epithelium +
connective tissue= endothelium Middle- smooth muscle Outer- loose and fibrous connective
tissue
Arterioles- tiny arteries
Capillaries
Nourish individual cells can be closed when muscles in
precapillary sphincter are contracted an arteriovenous shunt is a vessel
allows the blood to bypass the capillaries and move on to a venule while the precapillary sphincter is closed
Veins
Venules- tiny veins that drain capillary beds
3 layers, but less muscle and connective tissue
Have one way valves to prevent blood from staying in the legs
Vein walls can expand- 70% of all the blood is in the veins
Heart
Cone shaped, fist sizedMyocardium- the cardiac musclePericardium- the thick sac around the
heartSeptum- the internal wall that separates
the right and left halves Upper 2 chambers- atria Lower 2- ventricles
Valves
Chordae tendineae- strings that prevent one way valves from opening backwards
Atrioventricular valves- separate upper and lower chambers
Right- tricuspid
Left- bicuspid or mitral Semilumar valves- downstream of ventricles
pulmonary- right aortic- left
Major vessels
Right half source of blood- from superior and inferior vena cavae
Right blood output- to Pulmonary arteries
Left blood input- from pulmonary veins Left output- to Aorta
HEART
RIGHT SIDE- PUMPS OXYGEN POOR BLOOD FROM BODY (VENA CAVA) TO LUNGS (PULMONARY ARTERY)
LEFT SIDE- PUMPS OXYGEN RICH BLOOD FROM LUNGS (PULMONARY VEIN) TO THE REST OF THE BODY (AORTA)
The Left side works harder
Cardiac cycle
Systole- period of muscle contractionDiastole- resting period Lub dub- sound of heart valves slamming shut Murmur- caused by leaky valvesSA node- the heart’s pacemaker- located on the right
atrium, creates the electrical impulseAV node- below right atrium- electrical impulse passes
through on its way to Perkinje fibers- conducts the impulses to the muscle
cells that cause contraction of ventricles
Control of heart rate
1 Medulla oblongata- nerve impulses from brain stem
2. Endocrine hormones from adrenal glands- epinephrine and nor epinephrine
Defibrillation- an electrical shock to reestablish ventricular rhythm given to persons with heart problems
HEART ATTACK
BLOCKAGE OF A CORONARY ARTERY which supplies the heart muscle with oxygen and nutrients
PART TO HEART MUSCLE SUFFOCATES
IF ENOUGH MUSCLE TISSUE STOPS WORKING THEN THE HEART CAN’T PUMP BLOOD (massive heart attack)
Other Problems/Treatments
Aneurysm- ballooning of weakened artery, can burst and cause massive internal bleeding
Treatments for clogged vessels Nitroglycerine- dilates blood vessels Clot dissolving drugs- to treat heart attack Angioplasty- balloon inflated inside a partially
clogged artery to expand it
BLOOD PRESSURE
THE FORCE THAT BLOOD EXERTS AGAINST THE WALLS OF OUR BLOOD VESSELS
CONTRACTION OF VENTRICLES= HIGH PRESSURE- SYSTOLE
PRESSURE DROPS MOMENTARILY- when the heart relaxes- DIASTOLE
BLOOD PRESSURE
SYSTOLE/DIASTOLE MEASURED WITH A STETHOSCOPE
AND PRESSURIZED CUFF CUFF CUTS OFF BLOOD AT A HIGH
ENOUGH PRESSURE SYSTOLIC- 110-140 = NORMAL BELOW 100- LOW
HYPERTENSION- 140/90 or greater
Other Problems
Hypertension= High blood pressure
Atheriosclerosis- cholesterol under endothelium of arteries
Blood clots may form on the irregular artery walls
Thrombus- attached clot- embolus- free clot which is moving through the vessels
Stroke- burst or blockage of brain arteriole
Veins
Weak one way valves- causes swelled veins (spider veins and varicose veins- usually in the legs/feet)
Hemorrhoids- swelled veins of rectum
Phlebitis- inflammation of veins