responsible for pumping blood through circulatory system

-primary pump = atrium, power pump = ventricle

-atria pumps blood into ventricle during relaxation

-ventricles pump blood out of heart during contraction

-5-6 L/min pumped out

-70 bpm

blood moves based on pressure gradients > contraction of the heart produces pressure!

RA > tricuspid > RV > pulmonary semilunar > pulmonary circulation > LA > bicuspid/mitral > LV > aortic semilunar > systemic circulation

tricuspid and bicuspid/mitral = atrioventricular valves

pulmonary and aortic = semilunar valves

prevent blood from flowing back!

1. regulate blood pressure to allow blood flow to meet metabolic needs of tissue

2. carry blood

3. exchange nutrients, waste products and gases

4. transport (hormones, components of immune system, enzymes)

5. direct blood pressure

1. elastic

2. muscular

3. arterioles

1. venules

2. small veins

3. medium veins

4. large veins

veins have thinner walls than arteries > less elastic tissue and smooth muscle

blood from arterioles go to capillaries then goes to the venous system

-area of exchange between blood and interstitial space

applies to all EXCEPT VENULES AND CAPILLARIES

1. tunica intima

A. endothelium

B. basement membrane

C. lamina propia: smooth muscle and connective tissue

D. internal elastic membrane

2. tunica media

A. smooth muscle: responsible for regulating blood flow

B. external elastic membrane

3. tunica adventitia: mainly connective tissue

largest diameter

closest to the heart so the pressure is high and fluctuates

tunica intima is thick

tunica media has greatest amt of elastic tissue and a small amt of smooth muscle 

tunica media contains 25-40 layers of smooth muscle > allows for regulation of BP

smaller arteries range from 40-300 micrometers in diameter

-40 micrometer arteries have 3-4 layers of smooth muscle

arteries: tunica media

veins: tunica adventitia

9-40 micrometers diameter

tunica intima has no internal elastic membrane

tunica media has 1-2 layers of circular smooth muscle cells

tube of endothelium on basement membrane

venules = 40-50 micrometers in diameter

small veins = 0.2 to 0.3 mm in diameter

venule structure is similar to capillaries except for diameter > can have some nutrient exchange

tunica intima thin

tunica media thin > but still can constrict/dilate to regulate BP

tunica adventitia is prominent

-veins which are 2mm in diameter or greater have valves

-venous system has low blood pressure > need a mechanism to ensure that blood flows only one way > number is greater in veins of the lower limb

-venous compression caused by contraction of skeletal muscle assists in maintaining blood flow

valves = folds in endothelium

varicose veins caused by stretching in vein walls in lower limbs which causes valves to become incompetent > backflow is not prevented > edema and stagnant blood flow

results in 

1. phlebitis: inflammation of veins

2. gangrene: tissue death caused by reduction or loss of blood supply

in arteries or veins greater than 1 mm diameter

small blood vessels = vasa vasorum supplies with nutrients and helps with temperature regulation

mostly innervation by sympathetic system

some parasympathetic

classified by diameter and permeability

1. continuous

2. fenestrated

3. sinusoidal

capillary = endothelial cell + basement membrane

-can have pericapillary cells between

1. macrophages

2. fibroblasts

3. undifferentiated smooth muscle cells

7-9 micrometer diameter

do not have gaps between endothelial cells

found in

1. muscle

2. nervous

3. connective tissue

70-100 micrometer diameter

pores or fenestrae covered by thin diaphragm > permeable

found in

1. intestinal villi

2. glomerulus of kidney

3. glomerulus of eyes

large diameter

large fenestrae without diaphragms > very permeable

NO BASEMENT MEMBRANE

found in

1. liver

2. spleen

3. bone marrow

arterioles > metarterioles > arteriole capillary system > venous capillary system > venule

precapillary sphincters: smooth muscle that can regulate blood flow

capillary networks found more in highly metabolic tissues: lungs, liver, skeletal muscle, cardiac muscle, kidney

functions

1. in the skin > thermoregulation and heat loss

2. in muscles > nutrient and waste exchange

blood flow from arterioles to small veins WITHOUT PASSING THROUGH CAPILLARY BED

found in

1. sole of foot

2. palm of hands

3. nail beds

4. pathologic conditions (trauma, injury): can lead to increased venous return and cardiac failure

begin in a capillary network and end in a capillary network without pumping mechanisms

1. hepatic portal vein: carries blood from capillaries in GI and spleen to dilated capillaries (sinusoids) in the liver

2. hypothalamohypophyseal portal vein: blood from hypothalamus of the brain to the anterior pituitary 

arteriosclerosis: general term for degeneration in arteries that make them harder or less compliant

-most significant in aorta, coronary and cerebral arteries

-changes occur most rapidly in aorta

deposition of fat like materials on walls of the arteries

risk factors

1. obesity

2. high cholesterol

3. smoking

4. diabetes

5. HTN

streamlined fashion

center moving faster compared to the outer layers > outer layers move slower because friction/resistance against the vessel wall

laminar flow becomes turbulent when rate of flow exceeds a critical velocity

interrupted flow > flowing against a constriction, sharp turn, rough surface

vibration of vessel walls due to turbulent flow > heart sounds

measure of force exerted by blood against a wall

refers to arterial pressure

needs to be high enough to maintain adequate blood flow to meet metabolic needs of tissues in the capillary networks

directly proportional to BP

regulated by NEURAL and HORMONAL mechanisms

mercury manometer: measures BP in mmHg > blood pressure of 100 mmHg can move a column of mercury 100 mm

blood moves because of a pressure gradient set up by blood pressure

korotkoff sounds: produced by turbulent flow in arteries as pressure is released from blood pressure cuff connected to a sphygmomanometer (ausculatory method)

start pumping > high pressure closes the brachial artery > release pressure and first sound at beginning of systole (artery starting to open) > listen to korotkoff sounds from the turbulent flow > keep releasing pressure and turbulent flow turns into laminar flow as the artery opens more > last sound heard when artery is completely open during diastole

flow = deltaP/R

poiseuille's law: flow decreases when resistance increases

venous system has very low resistance so peripheral resistance = resistance of arterial system

as viscosity increases, pressure required to flow increases

-viscosity of whole blood = 3-4.5 > compared to water = 1

-whole blood needs 3 times more pressure to flow compared to water

based on hematocrit: ratio of volume of packed RBC to volume of blood

-viscosity not really related to plasma proteins, only to Hct > exponential relationship between Hct and viscosity

pressure at which a blood vessel collapses and blood flow stops

-when pt is in shock > BP drops below critical closing pressure and the vessel collapses > leads to necrosis

laplace's law: F = D*P

-force acting on a blood vessel wall is proportional to diameter of the vessel and blood pressure

-in aneurysm: bulge is created which has a high diameter > higher force applied to it > eventually can burst

compliance = change in volume/change in pressure

high compliance: small change in pressure leads to large stretch/distensability

venous system has a LARGE COMPLIANCE > acts as a blood resevoir

inversely related to compliance

elasticity = change in pressure/change in volume

capability of returning to the original form after pressure is removed

as diameter decreases > total cross sectional area increases and blood flow velocity decreases

larger cross sectional area = large gorge > water moves slowly through it compared to a small narrow river

capillaries have high cross sectional area > blood flow its longer to allow for more exchange

aortic BP fluctuates between 120 and 80

-BP avg in aorta is 100 and drops to 0 in the RA

greatest drop in BP is in the arterioles > REGULATES BF because arterioles have highest resistance to flow

in capillaries and veins > less resistance > less BP fluctuations

pulse pressure = systolic - diastolic

can be used to determine heart rate or rhythmiticity

strong pulse: high stroke volume

weak pulse: low stroke volume and increased constriction of arteries and decreased vascular compliance (stiffer)

superficial temporal

facial

common carotid

axillary

brachial 

radial

femoral

popliteal

dorsalis pedis

posterior tibial

movement in and out of capillaries by:

1. diffusion

2. filtration

3. reabsorption

4. diapedesis: passage of blood cells through capillary walls into tissues > mainly for larger cells that cannot travel by diffusion or filtration

1. traveling distance

2. concentration gradient

3. size of ions or molecules 

4. chemical nature: hydrophobic/philic

water

gases

nutrients

hormones

wastes

electrolytes

leukocytes

WATER SOLUBLES: glucose, AA > diffuse through pores of EC

IONS: diffuse through channels

LIPID SOLUBLE GASES: O2 and CO2 and STEROID HORMONES: diffuse through plasma membrane

LARGE WATER SOLUBLES: unable to leave blood except for areas of large fenestrae (kidney, intestine)

PLASMA PROTEINS: cannot cross

process of straining the fluid (plasma) out 

occurs in capillaries because they are porous/permeable

occurs more at the arterial capillary bed where hydrostatic pressure is highest (CHP starts at 35 then drops to 15 on venous end)

constant throughout the entire capillary bed

water leaves hypotonic soln pushing its way into hypertonic soln > OSMOSIS

BLOOD IS HYPERTONIC TO INTERSTITIAL FLUID > blood colloid osmotic pressure

net filtration pressure: NFP = CHP - BCOP 

-positive NFP = outward movement

CHP starts at 35 and goes down to 10 on venous end

BCOP remains constant at 25

as fluids are pushed out of capillary > some go into the lymphatic vessel to the venous circulation

CO = SV * HR

CO at rest is 5.6 L/min

SV = volume of blood pumped out of the LV in one beat

CO = volume of blood pumped out of LV in one minute

depends on 

1. preload

2. afterload

VR increases because:

1. increased blood volume

2. increased venous tone by SNS

frank starling relationship: preloads less than 15 mmHg > high stretch > high intrinsic recoil > higher SV

PRELOAD ABOVE 15 MMHG DOES NOT INCREASE SV

resistance to LV ejection presented by aortic and systemic vascular resistance SVR/TPR

increased arteriole constriction > increased TPR > increased afterload > decreased SV > decreased pulse pressure > weak pulse

BP is 0 at the RA

BP avg 100 in the aorta

in standing position: hydrostatic pressure is affected by gravity and decreases ABOVE THE HEART and increases BELOW THE HEART

1. increased permeability of capillaries: inflammation

2. decrease of plasma protein: starvation or liver disease > decreased BCOP

3. blockage of veins

4. blockage or removal of lymphatic vessels: responsible for draining some of the excess blood out