Unit 05: Circulation and Gas Exchange Flashcards
In which animals does cell-environment exchange occur by only diffusion?
Simple animals with small/thin bodies.
Cnidaria, Porifera, Platyhelminths
In which animals does cell-environment exchange occur by both diffusion and circulation?
Bigger and thicker animals, all other phyla.
Fluid filled circulatory system.
What are the 3 basic components of the circulatory system?
- Circulatory fluid
- Interconnecting vessels
- Muscular pump (heart)
Describe an open circulatory system and state which animals have it.
Hemolymph pumped from heart through blood vessels into sinuses where gas exchange occurs?
Low energy, less efficient
Arthropods, mollusks
Describe a closed circulatory system and state which animals have it.
Only blood pumped from heart into large vessels, then go into smaller vessels where exchange occurs.
High energy, more efficient, more pressure.
Vertebrates, annelids, cephalopods
What are the four types of blood vessels in vertebrates?
- Arteries -> arterioles
- Capillary -> capillary bed
- Portal vein (connects capillary beds)
- Venules -> veins
Describe the steps of circulatory system.
- Heart pumps blood to arteries, which then goes into arterioles and into organs.
- Blood travels to capillaries attached to capillary bed.
- Portal vein transports blood from capillary bed to capillary bed.
- Blood goes into venules which lead to veins, bringing blood back to heart
What are the 2 minimum muscle chambers of the heart?
Ventricle and atrium
Describe single circulation and name some animals with have this type of circulation.
Blood passes through 2 chambered heart once per cycle, only deoxygenated blood passes through heart, causing lower metabolic rate.
Jawless, bony and cartilaginous fish
Describe double circulation and name some animals with have this type of circulatory system.
Blood passes through >2 chambered heart 2 times.
Heart-> body
Heart -> Respiratory
Advantages: Heart receives oxygenated blood, therefore higher metabolic rate.
Many chambers, therefore, more efficient separation of oxygenated and deoxygenated blood.
Describe a pulmocutaneous circuit. In which animals are these present in?
Three chambered heart comprised of 2 atria and central ventricle that is really just a space between the atria.
Left atria receives oxygenated blood from respiratory surfaces (skin, lungs)
Right atria receives deoxygenated blood from body.
Ventricle allows for partial separation of oxygenated and deoxygenated blood.
Found in amphibians
Describe a pulmonary circuit in reptiles.
Three chambered heart comprised of left and right atria and left and right ventricle, which are partially separated by incomplete septum.
Describe a pulmonary circuit in mammals and birds.
4 chambered heart.
Right atrium receives deoxygenated blood which right ventricle pumps to lungs via pulmonary artery.
Left atrium receives newly oxygenated blood via pulmonary vein which goes into left ventricle which it is then pumped out of, going to the rest of the body via aorta.
Complete separation of oxygenated and deoxygenated blood.
What is gas exchange and how does it happen?
O2 in, CO2 out. Oxygen diffuses from environment through respiratory surface (squamous epithelial cells) to blood vessel where O2 will travel through blood around the body.
What maximizes diffusion efficiency?
- Single cell layer and capillaries
- Large SA
- Moist
What is respiratory media?
The medium (water, air) in which the oxygen diffuses from, and in which the CO2 will diffuse out to.
Approximately how wide are capillaries?
Only slightly wider than red blood cell.
What are the walls of capillaries called? Why are they so thin?
Endothelium (plus its basal lamina)
To facilitate exchange of materials
Where is the velocity of blood flow the slowest?
Capillary beds due to high resistance. Needs to be slow for exchange of materials.
Blood flows from areas of ____ to _____ pressure.
Higher to lower
What feature of the arteries helps maintain blood pressure?
Recoil of elastic arterial walls.
How do capillaries and arterioles help dissipate pressure?
Resist blood flow due to tiny diameter.
What is the fluid lost by capillaries called?
Lymph
How does lymph reenter circulatory system?
Through veinous end of capillary bed, indirectly through lymphatic system.
Lymphatic system then drains lymph into neck.
What organs filter lymph?
Lymph nodes
What happens to lymph nodes when body is fighting an infection?
Become swollen and tender
What is partial pressure and why does it matter for gas exchange?
The pressure exerted by one gas in a mix of gasses./ gas dissolved in liquid.
Gas will always diffuse from higher to lower partial pressure, so we can predict the net movement of gas at the exchange surface.
What are gills? What is their function?
Outfoldings of body with dense capillaries in aquatic animals. Have a large surface area to allow for gas exchange.
What are lungs?
Localized respiratory organ resulting from infoldings of body. As they do not directly contact cells, need circulatory system to transport CO2 and O2
50x the surface area of skin in humans, but generally size and complexity correlate with metabolic rate.
What is the order of the branching tubes that make up mammalian lungs?
Trachea, bronchi, bronchioles, alveoli (where gas exchange with capillaries occurs)
