Circulatory System: Gas Exchange and Respiration Flashcards
What do organisms exchange with the surrounding environment?
Molecules!
Intake of oxygen, proteins, sugars;
Removal of molecules toxic to life
How does exchange occur in organisms?
Diffusion, across a membrane (cell) or exchange surface (tissue)
How do single-celled organisms make exchange?
DIRECTLY, with the surrounding environment (fluid),
A gastrovascular cavity is sufficient for gas exchange, distribution of substances = Enough surface area available!
When does diffusion work well?
It is only efficient over small distances –> Easy, rapid movement in smaller organisms!
Time of diffusion is proportional to (distance)^2
What do simple animals lack?
A circulatory system.
Where does an exchange take place in simple organisms?
In the CAVITY (aka gastrovascular)
What is a complex animal’s circulatory system comprised of?
- A set of interconnecting VESSELS
- A muscular pump –> the HEART
- A circulatory fluid, BLOOD
What is a circulatory system’s function?
To link exchange surfaces with cells throughout the body.
Within a circulatory system, ___________ facilitate gas exchange.
Specialized organs.
For example, lungs, gills, tracheal system
What are lungs?
Infoldings of the body, that create a large surface area for gas exchange = Max contact with the environment
-Our lungs are the site of exchange of oxygen (in), carbon dioxide (out)
What are gills?
Outfoldings of the body, that create a large surface area for gas exchange
What is the tracheal system?
In insects, a network of branching tubes delivers oxygen to cells and tissues = Exchange of gas to the liver.
Air diffuses passively in/out, and the openings can be opened/closed as necessary = Holes that mediate!
*Depends on moisture levels!
What is an open circulatory system?
In which there is no distinction between blood and the interstitial fluid.
It then relies on the process of diffusion to move cells in/out.
What is hemolymph?
A circulatory fluid in insects, other arthropods, and most molluscs, that bathes organs (heart) directly in an open circulatory system.
A mixture of blood and other extracellular fluids
What is a closed circulatory system?
In which blood is confined to vessels, distinct from the interstitial fluid.
It is more efficient in transporting circulatory fluids to tissues and cells. The heart contraction moves blood in a specific direction.
Movement only WITHIN the circuit (blood).
Who possesses a cardiovascular system?
Humans and other vertebrates!
In cardiovascular systems, blood flow is _________ in the vessels, accomplished by a series of _______.
One way; valves
What is the role of skeletal and smooth muscles in the circulatory system?
Their squeezing moves the fluid through the vessels.
Where are valves located?
Throughout the blood vessels, and within organs.
What is single circulation?
In which blood leaving the heart passes through two capillary beds before returning.
The heart has a single pump that forces fluid directionally, passing through two different areas: Gill capillaries, body capillaries.
There is no separation in having dedicated blood vessels for carrying oxygenated and deoxygenated blood.
Arteries carry blood away from the heart, veins carry blood into the heart.
Which species have single circulation?
Bony fishes, rays, sharks, which have a single circulation with a two-chambered (atrium (receives blood) and the ventricle (holds blood and pumps it away)) heart.
What is double circulation?
In which oxygen-poor and oxygen-rich blood are pumped separately
= Two circuits
How is oxygen-rich blood delivered from the heart to the rest of the body, in double circulation?
Systemic circuit: Connecting the rest of the body tissues to the heart
How is oxygen-poor blood delivered from the heart to the rest of the body, in double circulation?
Pulmonary (lungs) circuit
How many chambers are there in mammals and bird circulation?
Four heart chambers! 2 sets of atrium/ventricle (left and right)
Pulmonary and systemic circuits separate oxygen-rich and oxygen-poor blood
How are amphibians particular?
Though they have double circulation, their separation of systemic and pulmonary circuits is INCOMPLETE.
–> There is no separation between left and right ventricles (no wall) = Three-chambered heart, in frogs. 2 atria, 1 ventricle.
In which other way does gas exchange occur in amphibians?
Through their lungs and skin = Pulmocutaneous circuit –> Picks up oxygen
How does circulation work in humans?
- Blood is being deoxygenated as muscles use oxygen. It gets dumped to the right atrium.
- Deoxygenated blood from elsewhere arrives into the heart, which moves to the right ventricle.
- The right ventricle moves this deoxygenated blood to the lung, in which gas exchange occurs.
- This oxygenated blood returns to the heart via the left atrium, then to the left ventricle.
- The left ventricle is the most powerful portion of the cell –> Feeds the rest of the body.
- Feeds oxygenated blood to the aorta, the largest blood vessel.
What is circulation closely tied to?
Respiration - gas exchange, moving gases from tissues in/out of the body.
What is an alveolus?
The functional unit of the vertebrate lung, a spherical structure = Main units
Our lungs are filled with many of these alveoli, air sacs that increase the effective surface area for exchange. They are rich in capillaries.
Where does gas exchange occur at the micro-level?
Capillaries!
How does coordination of circulation and gas exchange work?
Blood arriving in the lungs has a low partial pressure of oxygen and a high partial pressure of carbon dioxide, relative to air.
In alveoli, oxygen diffuses into oxygen-poor blood (high concentration to low concentration). Carbon dioxide diffuses into the air.
Diffusion assisted by many structures, to enlarge the effective surface area!
What is a partial pressure gradient?
The difference on either side of the membrane.
Where do partial pressure gradients occur?
In tissue capillaries, which favour diffusion into the interstitial fluids, and carbon dioxide into the blood.
Capillaries make contact with specialized organs, tissues
What does human breathing rely upon?
Negative pressure generated by muscles.
Expansion of ribcage = Use muscle power (rib muscles contract) = Sucks air in - Inhalation
The diaphragm contracts, causing atmospheric air to rush in.
And vice-versa, with exhalation.
**INEFFICIENT: We don’t make a complete swap of oxygenated and deoxygenated air –> RESIDUAL VOLUME of air remains in the lungs.
How do birds breathe?
- Directional: On an inhalation, the air gets stored in posterior air sacs; on second breath, gets moved to the lungs; then, moves into the anterior air sacs to be dumped.
- They have 8-9 air sacs, that function as bellows that keep air flowing through the lungs
The air coming through is ‘picked clean’ of oxygen before being dumped out = NO RESIDUAL VOLUME
The passage of air through the entire system of lungs and air sacs requires TWO CYCLES of inhalation and exhalation.
How is homeostasis maintained, and how do we control the breathing rate?
The fall in the pH, due to the increase in the concentration of dissolved carbon dioxide = More acidic
The blood vessels detect this and send signals to be picked up by the brain, the medulla.
The medulla signals to the muscles in the chest to increase breathing rate –> Carbon dioxide concentration levels decrease, pH rises back up.
Falling pH = Increase rate of breathing = Bringing oxygenation back up.
What systems is the circulatory system coordinated with?
Nervous, endocrine systems.
