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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 sized
Myocardium- the cardiac muscle
Pericardium- the thick sac around the
heart
Septum- 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 contraction
Diastole- resting period
 Lub dub- sound of heart valves slamming shut
 Murmur- caused by leaky valves
SA node- the heart’s pacemaker- located on the right
atrium, creates the electrical impulse
AV 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 MOMENTARILYwhen 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 veinsusually in the legs/feet)
Hemorrhoids- swelled veins of rectum
Phlebitis- inflammation of veins
