CirculationCirculation

The Presence of a Circulatory System:The Presence of a Circulatory System:

Reduces the distance a substance must Reduces the distance a substance must travel to enter or leave a cell.travel to enter or leave a cell.

Uses “Blood” to carry these molecules to the cells.Uses “Blood” to carry these molecules to the cells.

O2 diffuses from the air in the lungs (or similar structures) across epithelium to the “blood” which carries it to all parts of the body.

Once in the capillaries, O2 diffuses across epithelium again to the tissues.

CO2, of course, moves in the opposite direction.

Circulatory systemsCirculatory systems All animals have:All animals have:

circulatory fluid = circulatory fluid = ““bloodblood”” tubes = tubes = blood vesselsblood vessels muscular pump = muscular pump = heartheart

open closed

hemolymph blood

Open circulatory systemOpen circulatory system

InvertebratesInvertebrates• insects, insects,

arthropods, arthropods, mollusksmollusks

No separation No separation between blood & between blood & interstitialinterstitial fluid fluid ((HemolymphHemolymph))

Closed circulatory systemClosed circulatory system InvertebratesInvertebrates

• earthworms, squid, earthworms, squid, octopusesoctopuses

VertebratesVertebrates Blood confined to Blood confined to vesselsvessels

& separate from & separate from interstitial fluidinterstitial fluid• 1 or more hearts1 or more hearts• large vessels to smaller large vessels to smaller

vesselsvessels• material diffuses material diffuses

between blood vessels between blood vessels & interstitial fluid& interstitial fluid

closed system = higher pressures

Vertebrate circulatory systemVertebrate circulatory system Adaptations in closed systemAdaptations in closed system

number of heart chambers differsnumber of heart chambers differs

4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure

What’s the adaptive value of a 4 chamber heart?

2 3 4

low pressureto body

low O2

to body

high pressure & high O2

to body

Evolution of vertebrate circulatory Evolution of vertebrate circulatory systemsystem

fish amphibian reptiles birds & mammals

A A

VV V VV

A AAAA

V

2 chamber 3 chamber 3 chamber 4 chamber

Evolution of 4-chambered heartEvolution of 4-chambered heart

convergentevolution

Selective forcesSelective forces increase body sizeincrease body size

• protection from predationprotection from predation• bigger body = bigger stomach for bigger body = bigger stomach for

herbivoresherbivores endothermyendothermy

• can colonize more habitats can colonize more habitats flightflight

• decrease predation & increase prey decrease predation & increase prey capturecapture

Effect of higher metabolic rateEffect of higher metabolic rate greater need for energy, fuels, Ogreater need for energy, fuels, O22, waste , waste

removalremoval• endothermic animals need 10x energyendothermic animals need 10x energy• need to deliver 10x fuel & Oneed to deliver 10x fuel & O2 2 to cellsto cells

Vertebrate cardiovascular systemVertebrate cardiovascular system Chambered heartChambered heart

atriumatrium = receive blood = receive blood ventricleventricle = pump blood out = pump blood out

Blood vesselsBlood vessels arteriesarteries = carry blood = carry blood awayaway from heart from heart

• arteriolesarterioles veinsveins = return blood = return blood toto heart heart

• venulesvenules capillariescapillaries = thin wall, exchange / diffusion = thin wall, exchange / diffusion

• capillary beds = networks of capillariescapillary beds = networks of capillaries

Exchange across capillary wallsExchange across capillary walls

Arteriole

Bloodflow

Venule

Lymphaticcapillary

Interstitialfluid

Fluid & solutes flows Fluid & solutes flows out of capillaries to out of capillaries to tissues due to tissues due to blood blood pressurepressure “ “bulk flow”bulk flow”

Interstitial fluid flows Interstitial fluid flows back into capillaries back into capillaries due to due to osmosisosmosis plasma proteins plasma proteins osmotic osmotic pressure in capillary pressure in capillary

BP > OP BP < OP

15% fluid returns via lymph

85% fluid returns to capillaries

Capillary

Pressure is greatest in the arteries, lowest in veins

MammalianMammaliancirculationcirculation

What do blue vs. red areas represent?What do blue vs. red areas represent?

pulmonary

systemic

systemic

Mammalian heartMammalian heartto neck & head

& arms

AV

SL

AV

Heart valvesHeart valves 4 valves in the heart4 valves in the heart

flaps of connective tissueflaps of connective tissue prevent backflowprevent backflow

Atrioventricular (AV) valvesAtrioventricular (AV) valves between atrium & ventriclebetween atrium & ventricle keeps blood from flowing back keeps blood from flowing back

into atria when ventricles contractinto atria when ventricles contract• ““lub”lub”

Semilunar valvesSemilunar valves between ventricle & arteriesbetween ventricle & arteries prevent backflow from arteries into prevent backflow from arteries into

ventricles while they are relaxingventricles while they are relaxing• ““dub”dub”

AV

SL

AV

Lub-dub, lub-dubLub-dub, lub-dub Tempo is controlled by Tempo is controlled by Sinoatrial Sinoatrial

nodenode (SA node) (SA node) located at right atrium by superior located at right atrium by superior

vena cavavena cava Contraction at SA node causes both Contraction at SA node causes both

atria to contract (lub)atria to contract (lub) Wave contraction passes down to Wave contraction passes down to

Atrioventricular nodeAtrioventricular node (AV node) (AV node) Impulse is delayed by 0.1 sec (atria Impulse is delayed by 0.1 sec (atria

need to empty)need to empty) Causes ventricle to contract (dub)Causes ventricle to contract (dub)

Heart murmurHeart murmur defect in valves causes hissing sound when defect in valves causes hissing sound when

stream of blood squirts backward through stream of blood squirts backward through valvevalve

Cardiac cycleCardiac cycle

systolic________diastolic

pump (peak pressure)_________________fill (minimum pressure)

1 complete sequence of pumping1 complete sequence of pumping heart contracts & pumpsheart contracts & pumps heart relaxes & chambers fill heart relaxes & chambers fill contraction phasecontraction phase

• systolesystole• ventricles pumps blood outventricles pumps blood out

relaxation phaserelaxation phase• diastolediastole• atria refill with bloodatria refill with blood

110

____

70

Measurement of blood pressureMeasurement of blood pressure

High Blood Pressure (hypertension)High Blood Pressure (hypertension) if top number (if top number (systolicsystolic pumping) > 150 pumping) > 150 if bottom number (if bottom number (diastolicdiastolic filling) > 90filling) > 90

Blood:Blood: It’s more than just red stuff.It’s more than just red stuff.

Plasma:

55%The fluid portion of blood.Water accounts for over 90%

Contains:Electrolytes- to maintain osmotic balance, buffer

•Nutrients•Respiratory gases

•Hormones

So, if blood is 55% plasma, the rest must be ….._________CELLS!

Blood: Blood: Erythrocytes-Erythrocytes- also called Red Blood Cells (RBCs)also called Red Blood Cells (RBCs)

So, what about those cells?

Leukocytes-Leukocytes-

•Transport oxygen (which binds to Hemoglobin)

• Lack nuclei or mitochondria

also called white blood cells (WBCs)

• Function in defense and immunity• DO have nuclei & mitochondria

Basophils

Lymphocytes

EosinophilsNeutrophils

Include:

Actually spend most of theirtime in interstitial fluid andthe lymphatic system.

Clotting: Clotting: a real fixer-upper…a real fixer-upper…

Platelets:Platelets:1. Clump & stick to the jagged edges of the cut.

Provides immediate but temporary “plug”

2. Release clotting factors which catalyze the reaction:Fibrinogen Fibrin

Fibrin aggregates to form the clot