Circulatory Systems

Exchange of Materials
- Animal cells exchange material across their cell membrane
- Fuels for energy
- Nutrients
- Oxygen
- Waster
- 1-cell organism
- Diffusion
Overcoming the limits of diffusion
- Diffusion is not adequate for moving material across more than 1-cell barrier
In Circulation
- What needs to be transported
- Nutrients and fuels
  - From digestive system
- Respiratory gases
  - O2 and CO2 to and from gas exchange systems
  - Lungs
  - Gills
- Intracellular waste
  - Waste products from cells
  - Water
  - Salts
  - Nitrogenous wastes

Urea

Protective agents
- Immune defenses
- White blood cells
- Antibodies
- Blood clotting agents
- Regulatory molecules
- Hormones
Circulatory Systems
- All animals have:
- Circulatory fluid
  - Blood
- Tubes
  - Blood vessels
- Muscular pump
  - Heart
Open Circulatory System
- Taxonomy
- Invertebrates
  - Insects
  - Arthropods
  - Mollusks
- Structure
- No separation between blood and interstitial fluid
  - Hemolymph
Closed Circulatory System
- Taxonomy
- Invertebrates
  - Earthworms
  - Squid
  - Octopuses
- Vertebrates
- Structure
- Blood confined to vessels and separate from interstitial fluid
  - 1 or more hearts
  - Large vessels to smaller vessels
  - Material diffuses between blood vessels and interstitial fluid
Adaptations in a Closed System
- Number of heart chambers differs
Evolution of a 4-chambered Heart
- Selective forces
- Increased body size
  - Protection from predation
  - Bigger body = bigger stomach for herbivores
- Endothermy
  - Can colonize more habitats
- Flight
  - Decrease population and increase prey capture
- Effect of higher metabolic rate
- Greater need for energy, fuels, oxygen, and waste removal
  - Endothermic animals need 10x more energy
  - Need to deliver 10x fuel and oxygen to cells
Vertebrate Cardiovascular System
- Chambered heart
- Atrium
  - Receive blood
- Ventricle
  - Pump blood out
- Blood vessels
  - Arteries
  - Carry blood away from heart
  - Veins
  - Return blood to heart
  - Cappilarries
  - Thin wall
  - Exchange/diffusion

Capillary beds = networks of capillaries

Arteries
- Built for high pressure pump
- Thicker walls
- Provide strength for high pressure pumping of blood
- Narrow diameter
- Elasticity
- Elastic recoil helps maintain blood pressure even when the heart relaxes
Veins
- Built for low pressure flow
- Thinner-walled
- Wider diameter
- Blood travels back to the heart at a low velocity and pressure
- Lower pressure
  - Distant from heart
  - Blood must flow by skeletal muscle contractions when we move
  - Squeeze blood through veins
- Valves
  - In larger veins, there are one-way valves that allow blood to flow only toward the heart
Capillaries
- Built for exchange
- Very thin walls
- Lack 2 outer wall layers
- Only endothelium
  - Enhances exchange across capillaries
- Diffusion
  - Exchange between blood and cells
Lymphatic System
- Parallel circulatory system
- Transports white blood cells
  - Defending against infection
- Collects interstitial fluid and returns blood
  - Maintains volume and protein concentration of blood
  - Drains into circulatory system near the junction of the vena cava and right atrium
Heart Valves
- 4 valves in the heart
- Flaps of connective tissue
- Prevent backflow
- Atrioventricular valve
- Between atrium and ventricle
- Keeps blood from flowing back into atria when ventricles contract
- Semilunar valves
- Between ventricle and arteries
- Prevent backflow from arteries into ventricles while they are relaxing
Heart Sounds
- Closing of valves
- “Lub”
  - Recoil of blood against close atrioventricular valves
- “Dub”
  - Recoil of blood against the semilunar valves
- Heart murmur
- Defect in valves cause hissing sound when a stream of blood squirts backward through the valve
Cardiac Cycle
- 1 complete sequence of pumping
- Heart contracts and pumps
- Heart relaxes and chamber fill
- Contraction phase
  - Systole
  - Ventricles pump blood out
- Relaxation phase
  - Diastole
  - Atria refill with blood