Circulation

Components need for circulatory system

1. Fluid — Transports materials (blood for humans)

2. Vessels — Carry fluid

3. Heart — pumps fluid

Open Circulatory System

• fluid = hemolymph

• hemolymph mixes with interstitial fluid

• heart pumps hemolymph into vessels -→ sinuses

• low pressure

• lower efficiency

• requires less E

• ex: arthropods, mollusks

Closed Circulatory System

• fluid = blood

• blood confined in vessels

• heart pumps blood throughout branches vessels

• high pressure

• higher efficiency

• requires more E

• cephalopods, annelids, vertebrates

SEQ open circulatory system

1. Heart contracts

2. hemolymph pumped into vessels

3. hemolymph enters interconnected sinuses

4. heart relaxes

5. hemolymph drawn back to the heart

Cardiovascular System Components

1. heart pumps blood

2. blood vessels carry the blood

3. capillaries are the site of O2 exchange

Fish Circulation

1. type — single circulation

2. chambers: 2

3. Atria: 1

4. Ventricle: 1

Blood pressure drops after capillary beds

blood moves slowly

less efficient

Amphibians Circulation

• double circulation

• 3 Chambers

• 2 Atria

• 1 Ventricle

• blood flow: 2 circuits

• Pulmocutaneous Circuit: lung and gas exchange

• Systemic Circuit: rest of body

• some mixing of blood occurs

Mammals and Birds

• double circulation

• 4 chambers

• 2 atria

• 2 ventricles

• pulmonary circuit: lungs only

• systemic circuit: rest of body

• completely separated circulation

• most efficient

Human Heart Structure

1. atria — receive blood from veins

2. ventricles — pump blood to arteries

3. pericardium — connective tissue sac surrounding the heart

Veins vs. Arteries

Veins — carry blood TO the heart

arteries — carry blood AWAY from the heart

Heart Valves

• flaps of connective tissue

• prevent backflow

SEQ Blood flow through AV heart valves

1. Blood enters atria through tissues

2. pressure in atria increases

3. AV valves open

4. Blood enters ventricles

5. ventricles contract

6. AV valves close

Blood Flow in Pulmonary Valve

RV → pulmonary artery

Blood flow in aortic valve

LV → aorta

Sound of heartbeat

valves closing

SEQ Human Heart Function

1. SA node generates an AP

2. impulse travels through the atria

3. atria contract simultaneously

4. AP reaches AV node

5. delay ~ 0.1 sec and AV node

6. Atria finishes contracting

7. signal travels through bundle branches

8. signal reaches apex

9. purkinje fibers spread signal through ventricles

10. ventricles contract

SA node

pacemaker of the heart

AV node

delays impulse

bundle branches

carry AP towards Apex

Purkinje fibers

spread AP though ventricles

If AV node delay did not occur

• ventricles would contract too early

• atria cannot fully empty

• reduced ventricular filling

• reduced cardiac efficiency

if valves failed?

• blood backflow

• reduced circulation efficiency

• pressure buildup

Baroreceptors

• sensory receptor

• in blood vessels and heart walls

• detect blood pressure changes

SEQ Nervous regulation of heart rate

• baroreceptors detect change in BP

• signals sent to medulla cardiac centers

• autonomic nerves signal SA node

• heart rate adjusted

Sympathetic

• increases heart rate

• increases contraction strength

Parasympathetic

• decreases heart rate

• slows heart

Epinephrine

• endocrine regulation

• increases heart rate

• higher temp = faster heart rate

Blood Vessel Structure

• 3 layers: endothelium, smooth muscle, connective tissue

• arteries

• capillaries

• veins

3 layers of blood vessel

1. endothelium — smooth lining

2. smooth muscle — controls diameter of vessels (thicker in arteries and thin in veins)

3. connective tissue — support and elasticity

4. thick walls prevent diffusion

arteries

• carry blood away from heart

• thick walls

• arteries → arterioles → capillaries

• usually no valves

• high pressure

Capillaries

• microscopic

• thin

• made of endothelium and basal lamina

• site of exchange

• exchange between blood and interstitial fluid

• one near every cell

Veins

• carry blood to heart

• thin walls

• pathway: capillaries → venules → veins

• valves: prevent backflow

• skeletal muscle helps move blood

• lower pressure than arteries

SEQ Blood Flow

1. heart pumps blood into arteries

2. arteries branch into arterioles

3. arterioles lead to capillaries

4. exchanges occurs at capillaries

5. blood enters venules

6. venuels merge in veins

7. veins carry blood back to the heart

what diffuses across capillaries

• nutrients

• ions

• gases

• waste products

Interstitial fluid

• surrounds tissues, DOESN’T contain RBCs

• 25% protein

• hypotonic to blood

Capillary fluid exchange

antagonistic force:

• blood pressure pushes fluid out

• osmotic pressure pulls fluid in

SEQ Capillary Exchange

Arterial end:

1. Blood pressure is greater than osmotic pressure

2. net movement of the fluid is out

Venus End:

1. Osmotic pressure greater

2. fluid moves IN

Functions of Lymphatic System

1. returns fluid back to blood — prevents fluid buildup

2. absorb lipid from SI

3. fights against disease

Lymph

fluid from interstitial fluid

Lymph vessels

carry lymph

Lymph nodes

filter lymph

lymph ducts

return lymph to blood

SEQ Lymphatic system

1. fluid leaves capillaries

2. extra fluid becomes interstitial fluid

3. interstitial fluid enters lymph vessels

4. becomes lymph

5. travels through lymph vessels

6. travels through lymph nodes

7. enters lymph ducts

8. returns to bloodstream

If Lymphatic system failed:

• fluid build up in tissue

• swelling (edema)

• poor fluid return to blood

• reduced lipid absorption

• increased disease risk

CC blood vs. lymphatic system

Blood:

• closed system

• pumped by heart

• contains RBCs

• higher pressure

• continuous circulation

• transports gases/ nutrients

Lymphatic:

• one way return

• no central pump

• usually no RBCs

• lower pressure

• returns fluid to bloodstream

• return excess fluid