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