Chapter 42 Circulation and Gas Exchange. Material Exchange The exchange of materials from inside to outside is an important function for organisms. It’s

Chapter 42Chapter 42

Circulation and Gas ExchangeCirculation and Gas Exchange

Material ExchangeMaterial Exchange

• The exchange of materials from inside to outside is an important function for organisms.

• It’s easy for unicellular organisms.

• It becomes more difficult for multicellular organisms.

• Complex organ systems have evolved to move materials throughout an organism.

• The exchange of materials from inside to outside is an important function for organisms.

• It’s easy for unicellular organisms.

• It becomes more difficult for multicellular organisms.

• Complex organ systems have evolved to move materials throughout an organism.

DiffusionDiffusion

• Diffusion takes time.• It is difficult to move substances more than a few millimeters with diffusion.

• Circulatory systems evolved to circumvent this problem.

• Bulk movement coupled with diffusion across small distances.

• Diffusion takes time.• It is difficult to move substances more than a few millimeters with diffusion.

• Circulatory systems evolved to circumvent this problem.

• Bulk movement coupled with diffusion across small distances.

InvertebratesInvertebrates

• Many animals have a simple body plan and don’t require a circulatory system.

• These animals have a thin gastrovascular system (2 cells thick).

• Materials enter and exit through a single opening and nutrients/wastes diffuse through the thin cell layer.

• Many animals have a simple body plan and don’t require a circulatory system.

• These animals have a thin gastrovascular system (2 cells thick).

• Materials enter and exit through a single opening and nutrients/wastes diffuse through the thin cell layer.

Other AnimalsOther Animals

• Many animals consist of multiple cell layers and diffusion becomes inefficient.

• 2 circulatory systems have evolved in invertebrates to accommodate this:

• 1. Open• 2. Closed

• Many animals consist of multiple cell layers and diffusion becomes inefficient.

• 2 circulatory systems have evolved in invertebrates to accommodate this:

• 1. Open• 2. Closed

1. Open Circulatory Systems

1. Open Circulatory Systems

• Invertebrates.• There is no distinction between blood and interstitial fluid.

• It is called hemolymph.

• Invertebrates.• There is no distinction between blood and interstitial fluid.

• It is called hemolymph.

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2. Closed Circulatory System

2. Closed Circulatory System

• Invertebrates.• Blood is confined to vessels and is distinct from interstitial fluid.

• Both systems have 3 basic components:

• 1. Circulatory fluid (blood)

• 2. A set of tubes (blood vessels)

• 3. A muscular pump (heart)

• Invertebrates.• Blood is confined to vessels and is distinct from interstitial fluid.

• Both systems have 3 basic components:

• 1. Circulatory fluid (blood)

• 2. A set of tubes (blood vessels)

• 3. A muscular pump (heart)



The Pump of Circulatory Systems


• 1. “Single” chambered hearts• Example: earthworm-peristalsis pumps blood.

• 2. 2 chambered hearts• Example: fish

• 1. “Single” chambered hearts• Example: earthworm-peristalsis pumps blood.

• 2. 2 chambered hearts• Example: fish



• 3. 3 chambered hearts• Example: amphibians and reptiles (not birds), pulmocutaneous circuit picks up O2, and the heart pumps the blood through the system.

• 4. 4 chambered hearts• Example: mammals and birds, a pulmonary circuit picks up O2 and returns it to the heart. The heart distributes the oxygenated blood to the rest of the body.

• 3. 3 chambered hearts• Example: amphibians and reptiles (not birds), pulmocutaneous circuit picks up O2, and the heart pumps the blood through the system.

• 4. 4 chambered hearts• Example: mammals and birds, a pulmonary circuit picks up O2 and returns it to the heart. The heart distributes the oxygenated blood to the rest of the body.

Circulatory SystemsCirculatory Systems

• The heart acts to increase the hydrostatic pressure which flows down a pressure gradient and back to the heart.

• Blood pressure is the motive force that moves the fluid through the circulatory system.

• Both open and closed systems are widespread throughout the animal kingdom.

• The heart acts to increase the hydrostatic pressure which flows down a pressure gradient and back to the heart.

• Blood pressure is the motive force that moves the fluid through the circulatory system.

• Both open and closed systems are widespread throughout the animal kingdom.

Circulatory SystemsCirculatory Systems

• Both open and closed have their advantages and disadvantages.

• Both open and closed have their advantages and disadvantages.

Circulatory Systems--Open

Circulatory Systems--Open

• Open systems have lower hydrostatic pressure.

• They are less costly in terms of metabolic energy expenditure for construction and maintenance.

• Open systems have lower hydrostatic pressure.

• They are less costly in terms of metabolic energy expenditure for construction and maintenance.

Circulatory Systems--Closed

Circulatory Systems--Closed

• They can achieve a higher blood pressure.

• They are more effective at transporting materials.

• They can accommodate larger, more active animals.

• They can achieve a higher blood pressure.

• They are more effective at transporting materials.

• They can accommodate larger, more active animals.

Vertebrate CirculationVertebrate Circulation

• Vertebrates generally have 1 or 2 atria, and 1 or 2 ventricles.

• It is a closed system.• Cardiovascular.• Atria receive blood• Ventricles pump blood

• Vertebrates generally have 1 or 2 atria, and 1 or 2 ventricles.

• It is a closed system.• Cardiovascular.• Atria receive blood• Ventricles pump blood

3 Main Blood Vessel Types

3 Main Blood Vessel Types

• 1. Arteries--carry blood away from the heart.

• 2. Veins--carry blood to the heart.

• 3. Capillaries--the spots where arteries and veins meet and nutrient exchange occurs.

• 1. Arteries--carry blood away from the heart.

• 2. Veins--carry blood to the heart.

• 3. Capillaries--the spots where arteries and veins meet and nutrient exchange occurs.

Blood Vessel TypesBlood Vessel Types

• Networks of capillaries infiltrate each tissue and exchange many nutrients with the tissues.

• Arterioles are the sites where small vessels convey blood to the capillaries.

• At the downstream end, capillaries converge into venules which converge into veins.

• Networks of capillaries infiltrate each tissue and exchange many nutrients with the tissues.

• Arterioles are the sites where small vessels convey blood to the capillaries.

• At the downstream end, capillaries converge into venules which converge into veins.

Different Circulation Systems


• Single circulation-invertebrates. Blood or hemolymph passes through one or more hearts on its way through the organism.

• Pulmocutaneous circulation-amphibians. Blood passes through the lungs and skin picking up O2 and giving off CO2.

• Single circulation-invertebrates. Blood or hemolymph passes through one or more hearts on its way through the organism.

• Pulmocutaneous circulation-amphibians. Blood passes through the lungs and skin picking up O2 and giving off CO2.



• Double circulation-blood passes through a 3 (reptiles) or 4 (mammals & birds) chambered heart twice.

• The first time, as CO2 rich blood.

• The second time as O2 rich blood.

• Double circulation-blood passes through a 3 (reptiles) or 4 (mammals & birds) chambered heart twice.

• The first time, as CO2 rich blood.

• The second time as O2 rich blood.

A Pulmocutaneous Circuit


• A pulmocutaneous circuit leads to capillaries in the gas exchange organs--lungs and skin.

• Most of the O2 rich blood is pumped into the systemic circuit which supplies O2 to the rest of the body.

• A pulmocutaneous circuit leads to capillaries in the gas exchange organs--lungs and skin.

• Most of the O2 rich blood is pumped into the systemic circuit which supplies O2 to the rest of the body.





• There is some mixing of the O2 rich and CO2 rich blood.

• A ridge in the ventricle diverts most of the O2 rich blood to the systemic circuit.

• There is some mixing of the O2 rich and CO2 rich blood.

• A ridge in the ventricle diverts most of the O2 rich blood to the systemic circuit.



Double CirculationDouble Circulation

• The organization called double circulation provides for vigorous blood flow.

• Blood gets pumped a second time after leaving the capillaries.

• Reptiles have double circulation with a pulmonary circuit.

• The organization called double circulation provides for vigorous blood flow.

• Blood gets pumped a second time after leaving the capillaries.

• Reptiles have double circulation with a pulmonary circuit.



Double CirculationDouble Circulation

• Some of these circuits contain a 3 chambered heart--amphibians, reptiles.

• The ventricle is partially divided by a septum to reduce blood mixing.

• Double circulation restores pressure to the systemic circuit after blood has passed through the lung capillaries.

• Some of these circuits contain a 3 chambered heart--amphibians, reptiles.

• The ventricle is partially divided by a septum to reduce blood mixing.

• Double circulation restores pressure to the systemic circuit after blood has passed through the lung capillaries.



Double CirculationDouble Circulation• Double circulation contrasts with single circulation seen in fish.

• In fish, the blood flows from the respiratory organs to the other organs under pressure.

• In double circulation pressure is restored to the systemic circuit after blood has passed through the lung capillaries.

• Double circulation contrasts with single circulation seen in fish.

• In fish, the blood flows from the respiratory organs to the other organs under pressure.

• In double circulation pressure is restored to the systemic circuit after blood has passed through the lung capillaries.







Advantages of a 4 Chambered Heart

Advantages of a 4 Chambered Heart

• The 4 chambered heart was an essential adaptation.• It helps support the endothermy.

• It delivers the high quantity of O2 and fuel necessary for metabolism.

• It removes wastes produced via metabolism.

• This movement of substances is made possible by the separate systemic and pulmonary circuits and the 4 chambered heart.

• The 4 chambered heart was an essential adaptation.• It helps support the endothermy.

• It delivers the high quantity of O2 and fuel necessary for metabolism.

• It removes wastes produced via metabolism.

• This movement of substances is made possible by the separate systemic and pulmonary circuits and the 4 chambered heart.

The 4 Chambered HeartThe 4 Chambered Heart• Consists mostly of cardiac muscle.

• It goes through a series of rhythmic contractions and relaxations to move blood.

• When the chambers relax they fill; when they contract, they empty.

• Systole-contraction• Diastole-relaxation

• Consists mostly of cardiac muscle.

• It goes through a series of rhythmic contractions and relaxations to move blood.

• When the chambers relax they fill; when they contract, they empty.

• Systole-contraction• Diastole-relaxation



The 4 Chambered HeartThe 4 Chambered Heart• Ventricles are usually larger because they move more blood.

• The AV valve is between the atria and ventricles.

• They prevent the backflow of blood during contraction.

• Semilunar valves prevent backflow of blood while it’s in the aorta.

• Ventricles are usually larger because they move more blood.

• The AV valve is between the atria and ventricles.

• They prevent the backflow of blood during contraction.

• Semilunar valves prevent backflow of blood while it’s in the aorta.

Heart RhythmHeart Rhythm• Maintaining rhythm is important because O2 is very important.

• Some cardiac muscles are self-excitable and do not need any input from the nervous system to contract.

• The heart’s pacemaker is the SA node.

• Maintaining rhythm is important because O2 is very important.

• Some cardiac muscles are self-excitable and do not need any input from the nervous system to contract.

• The heart’s pacemaker is the SA node.



The SA NodeThe SA Node• It sets the rate and timing of heart contractions.

• It is located in the wall of the right atrium and is made of specialized cells.• Myogenic hearts have a pacemaking ability that originates in the heart.

• Neurogenic hearts have contractions that originate from motor nerves.

• It sets the rate and timing of heart contractions.

• It is located in the wall of the right atrium and is made of specialized cells.• Myogenic hearts have a pacemaking ability that originates in the heart.

• Neurogenic hearts have contractions that originate from motor nerves.

The SA NodeThe SA Node• The SA node generates electrical impulses similar to those produced by nerve cells.

• The cardiac muscle contains the SA node that sets the tempo for the entire heart.

• The impulse is quickly passed through the muscles and passes a relay point called the AV node.

• The SA node generates electrical impulses similar to those produced by nerve cells.

• The cardiac muscle contains the SA node that sets the tempo for the entire heart.

• The impulse is quickly passed through the muscles and passes a relay point called the AV node.



The AV nodeThe AV node• The AV node is located in the wall between the right atrium and right ventricle.

• The AV node slightly delays the signal impulse.

• The delay ensures that the atria empty before the ventricles contract.

• The AV node is located in the wall between the right atrium and right ventricle.

• The AV node slightly delays the signal impulse.

• The delay ensures that the atria empty before the ventricles contract.



Purkinje FibersPurkinje Fibers

• These are specialized muscle fibers that conduct signals to the apex of the heart and throughout the ventricles.

• These are specialized muscle fibers that conduct signals to the apex of the heart and throughout the ventricles.

The HeartThe Heart

• Although the SA node sets the tempo for the heart, it is innervated by 2 nerves that affect heart rate.

• One speeds it up.• The other slows it down.• Hormones, body temperature, and physical activity also have an effect on heart rate.

• Although the SA node sets the tempo for the heart, it is innervated by 2 nerves that affect heart rate.

• One speeds it up.• The other slows it down.• Hormones, body temperature, and physical activity also have an effect on heart rate.

Blood VesselsBlood Vessels• Arteries and veins.• They are all built from similar tissues:

• 1. The outside layer consists of connective tissue with elastic fibers.

• This allows for functional stretch and recoil.

• Arteries and veins.• They are all built from similar tissues:

• 1. The outside layer consists of connective tissue with elastic fibers.

• This allows for functional stretch and recoil.

Blood VesselsBlood Vessels• 2. The middle layer consists of smooth muscle and more elastic fibers.

• 3. The inner layer is lined with a smooth layer of flattened endothelial cells.

• 2. The middle layer consists of smooth muscle and more elastic fibers.

• 3. The inner layer is lined with a smooth layer of flattened endothelial cells.

ArteriesArteries

• Arteries have thicker walls and are more elastic.

• They are for pumping quickly at high pressure.

• Their elastic walls allow for pressure to remain high even when the heart isn’t contracting.

• Arteries have thicker walls and are more elastic.

• They are for pumping quickly at high pressure.

• Their elastic walls allow for pressure to remain high even when the heart isn’t contracting.

CapillariesCapillaries• These are different from arteries and veins.

• They lack the 2 outer layers (connective tissue and smooth muscle) and consist of only endothelial cells.

• This facilitates the exchange of materials between blood and interstitial fluid.

• These are different from arteries and veins.

• They lack the 2 outer layers (connective tissue and smooth muscle) and consist of only endothelial cells.

• This facilitates the exchange of materials between blood and interstitial fluid.



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CapillariesCapillaries• Generally, the smaller the diameter of the pipe, the faster liquid has to flow.

• Due to the large cross-sectional area of capillaries, blood moves very slowly through them.

• Blood pressure is low at the capillary due to the resistance encountered.

• Generally, the smaller the diameter of the pipe, the faster liquid has to flow.

• Due to the large cross-sectional area of capillaries, blood moves very slowly through them.

• Blood pressure is low at the capillary due to the resistance encountered.

CapillariesCapillaries

• As the blood leaves the capillary, it speeds back up as it enters the vein.

• As the blood leaves the capillary, it speeds back up as it enters the vein.

VeinVein• Veins have thinner walls.

• The blood moves slower through them and is under low pressure.

• The movement is facilitated by muscle contraction.

• Veins have valves that prevent the backflow of blood down the vein due to low pressure.

• Veins have thinner walls.

• The blood moves slower through them and is under low pressure.

• The movement is facilitated by muscle contraction.

• Veins have valves that prevent the backflow of blood down the vein due to low pressure.





VeinsVeins

• Blood returns to the heart via action of smooth muscles in the venules and veins.

• Contraction of skeletal muscle greatly assists movement of the blood.

• Blood returns to the heart via action of smooth muscles in the venules and veins.

• Contraction of skeletal muscle greatly assists movement of the blood.

Blood Flow Through Capillaries


• There are 2 mechanisms that regulate the distribution of blood flow through the capillaries:

• 1. Smooth muscle constricts, decreasing the diameter of the arteriole reducing blood flow through it.

• There are 2 mechanisms that regulate the distribution of blood flow through the capillaries:

• 1. Smooth muscle constricts, decreasing the diameter of the arteriole reducing blood flow through it.



• 2. Precapillary sphincters that control the flow of blood through the arterioles and sphincters.

• 2. Precapillary sphincters that control the flow of blood through the arterioles and sphincters.

In The Capillary BedsIn The Capillary Beds

• Substances move in and out by diffusion, endocytosis, and exocytosis.

• There are many clefts between the endothelial cells--diffusion occurs here.

• Blood pressure is largely responsible for movement of materials through the clefts however.

• Substances move in and out by diffusion, endocytosis, and exocytosis.

• There are many clefts between the endothelial cells--diffusion occurs here.

• Blood pressure is largely responsible for movement of materials through the clefts however.

In The Capillary BedsIn The Capillary Beds• Many substances are too large to cross the endothelium.

• Osmotic pressure between the arteriole and venule remains constant.

• However, blood pressure drops significantly between the arteriole and venule.

• Many substances are too large to cross the endothelium.

• Osmotic pressure between the arteriole and venule remains constant.

• However, blood pressure drops significantly between the arteriole and venule.

In The Capillary BedsIn The Capillary Beds• At the arteriole end, blood pressure is high compared to the osmotic pressure.

• Fluids flow out of the arteriole and into the interstitial fluid.

• At the arteriole end, blood pressure is high compared to the osmotic pressure.

• Fluids flow out of the arteriole and into the interstitial fluid.

In The Capillary BedsIn The Capillary Beds• At the venule end, the blood pressure is low compared to the osmotic pressure.

• Fluid flows into the venule from the interstitial fluid.

• 85% of the fluid lost from the arteriole end is recovered.

• 15% of the fluid is recovered by the lymphatic system.

• At the venule end, the blood pressure is low compared to the osmotic pressure.

• Fluid flows into the venule from the interstitial fluid.

• 85% of the fluid lost from the arteriole end is recovered.

• 15% of the fluid is recovered by the lymphatic system.

Lymphatic SystemLymphatic System• The fluid of the lymphatic system is called lymph.• It has roughly the same composition as interstitial fluid.

• Lymph capillaries are interspersed throughout the cardiovascular capillaries.

• These assist with the reabsorption of fluid.

• The fluid of the lymphatic system is called lymph.• It has roughly the same composition as interstitial fluid.

• Lymph capillaries are interspersed throughout the cardiovascular capillaries.

• These assist with the reabsorption of fluid.





Lymphatic SystemLymphatic System

• The lymph vessels are very similar to veins.

• They have valves that prevent the backflow.

• Rhythmic contractions of smooth muscle assist in lymph flow.

• Skeletal muscle contractions are the main sources of lymph movement.

• The lymph vessels are very similar to veins.

• They have valves that prevent the backflow.

• Rhythmic contractions of smooth muscle assist in lymph flow.

• Skeletal muscle contractions are the main sources of lymph movement.

Lymphatic SystemLymphatic System• Lymph nodes are lymph vessel organs.

• They contain WBC’s (lymphocytes) and cells specialized for defense (macrophages).

• They filter the lymph and attack foreign invaders (antigens).

• They often swell when we are ill.

• Lymph nodes are lymph vessel organs.

• They contain WBC’s (lymphocytes) and cells specialized for defense (macrophages).

• They filter the lymph and attack foreign invaders (antigens).

• They often swell when we are ill.



Blood CellsBlood Cells• Blood cells and cell fragments occupy about 45% of the blood volume.• 55% is plasma.• Plasma is 90% water, it contains electrolytes.

• Plasma proteins help to maintain pH, osmotic balance, and blood viscosity.

• Some of these proteins are immunoglobulins that function in defense.

• Blood cells and cell fragments occupy about 45% of the blood volume.• 55% is plasma.• Plasma is 90% water, it contains electrolytes.

• Plasma proteins help to maintain pH, osmotic balance, and blood viscosity.

• Some of these proteins are immunoglobulins that function in defense.



PlasmaPlasma

• Blood plasma suspends 3 elements:

• 1. RBC’s--oxygen transport, most numerous.

• 2. WBC’s--defense of body.

• 3. Platelets--fragments of cells which help in the clotting process.

• Blood plasma suspends 3 elements:

• 1. RBC’s--oxygen transport, most numerous.

• 2. WBC’s--defense of body.

• 3. Platelets--fragments of cells which help in the clotting process.





This image is copyright Dennis Kunkel

1. Red Blood Cells1. Red Blood Cells• Shape is related to its function.

• Biconcave increases its surface area.

• Small size and number increases surface area--related to function.

• Mammalian lack nuclei--allows for more hemoglobin.

• Shape is related to its function.

• Biconcave increases its surface area.

• Small size and number increases surface area--related to function.

• Mammalian lack nuclei--allows for more hemoglobin.



1. Red Blood Cells1. Red Blood Cells

• RBC production is stimulated by a negative feedback mechanism.

• When the amount of O2 reaching body tissues decreases, this stimulates the kidney to synthesize EPO.

• When more O2 reaches the tissues, EPO levels fall and erythrocyte production slows.

• RBC production is stimulated by a negative feedback mechanism.

• When the amount of O2 reaching body tissues decreases, this stimulates the kidney to synthesize EPO.

• When more O2 reaches the tissues, EPO levels fall and erythrocyte production slows.

Heart DiseaseHeart Disease• LDL’s are bad.• HDL’s are good.• Cholesterol is bad in large quantities.

• It sticks to the inside walls of arteries and results in a narrowing of the arteries, a stiffening of their walls (called atherosclerosis).

• This increases the risk of heart attack and stroke.

• LDL’s are bad.• HDL’s are good.• Cholesterol is bad in large quantities.

• It sticks to the inside walls of arteries and results in a narrowing of the arteries, a stiffening of their walls (called atherosclerosis).

• This increases the risk of heart attack and stroke.

2. Leukocytes (WBC’s)2. Leukocytes (WBC’s)

• These are white blood cells and there are 5 types:• 1. Monocytes• 2. Neutrophils• 3. Basophils• 4. Eosinophils• 5. Lymphocytes

• Collectively, these fight infection.

• These are white blood cells and there are 5 types:• 1. Monocytes• 2. Neutrophils• 3. Basophils• 4. Eosinophils• 5. Lymphocytes

• Collectively, these fight infection.

The Contents of BloodThe Contents of Blood



Erythrocytes

NeutrophilLymphocyte

Monocyte

Eosinophil

Platelets



Basophil

2. Leukocytes (WBC’s)2. Leukocytes (WBC’s)

• These spend most of their time in the interstitial fluid where they fight invaders.

• These spend most of their time in the interstitial fluid where they fight invaders.

Stem CellsStem Cells

• Recall that they are pluripotent.

• They can develop into many different types of things:• 1. Erythrocytes• 2. Leukocytes• 3. Platelets

• They are found in bone marrow.

• Recall that they are pluripotent.

• They can develop into many different types of things:• 1. Erythrocytes• 2. Leukocytes• 3. Platelets

• They are found in bone marrow.

3. Platelets3. Platelets

• These plug wounds and prevent blood loss.

• Wounds release factors that make platelets sticky and enable them to adhere to collagen fibers in connective tissue slowing blood loss.

• These plug wounds and prevent blood loss.

• Wounds release factors that make platelets sticky and enable them to adhere to collagen fibers in connective tissue slowing blood loss.

Respiratory SystemRespiratory System

• Respiratory surfaces allow for the exchange of gases.

• They are always thin and bathed in water.

• In most animals, the respiratory medium is a thin, moist epithelium.

• This separates the respiratory medium from the blood.

• Respiratory surfaces allow for the exchange of gases.

• They are always thin and bathed in water.

• In most animals, the respiratory medium is a thin, moist epithelium.

• This separates the respiratory medium from the blood.

Respiratory SystemRespiratory System

• In animals that don’t respire through their skin, there are three common respiratory surfaces:

• 1. Gills• 2. Trachea• 3. Lungs

• In animals that don’t respire through their skin, there are three common respiratory surfaces:

• 1. Gills• 2. Trachea• 3. Lungs

1. Gills1. Gills

• Are out-foldings of the body surface suspended in water.

• They are loaded with capillaries.

• Animals with gills ventilate them which moves water with a high concentration of O2 over them.

• Are out-foldings of the body surface suspended in water.

• They are loaded with capillaries.

• Animals with gills ventilate them which moves water with a high concentration of O2 over them.

1. Gills1. Gills• Blood moves in an opposite direction to the movement of water past the gills.

• The O2 transfer is highly efficient.• This is called counter-current exchange, and loads the blood with O2.

• It keeps a diffusion gradient over the entire length of the capillary.

• Blood moves in an opposite direction to the movement of water past the gills.

• The O2 transfer is highly efficient.• This is called counter-current exchange, and loads the blood with O2.

• It keeps a diffusion gradient over the entire length of the capillary.

2. Tracheal System2. Tracheal System• Found in insects.• It is made up of tubes that branch through the body which is a variation on a folded, internal respiratory surface.

• The trachea branches smaller and smaller and contacts nearly every cell.

• Found in insects.• It is made up of tubes that branch through the body which is a variation on a folded, internal respiratory surface.

• The trachea branches smaller and smaller and contacts nearly every cell.

3. Lungs3. Lungs

• These are respiratory organs found in one spot of the body.

• They have a dense net of capillaries immediately below the epithelium on the respiratory surface.

• They are connected to a closed system that transports gases to and from other regions of the body.

• These are respiratory organs found in one spot of the body.

• They have a dense net of capillaries immediately below the epithelium on the respiratory surface.

• They are connected to a closed system that transports gases to and from other regions of the body.

Air PathwayAir Pathway

• Nares pharynx, larynx, trachea, bronchi, bronchioles, alveoli

• It is like a tree tipped upside down.

• The epithelial lining of the three major branches of the respiratory system are covered by cilia and a thin film of mucus.

• Nares pharynx, larynx, trachea, bronchi, bronchioles, alveoli

• It is like a tree tipped upside down.

• The epithelial lining of the three major branches of the respiratory system are covered by cilia and a thin film of mucus.

Air PathwayAir Pathway

• The mucus traps particulate matter and the cilia sweeps it out.

• The thinnest bronchioles are dead end sacs called alveoli, have a high SA.

• O2 dissolves in the moist film covering the epithelium and quickly diffuses into the web of capillaries surrounding the alveolus.

• CO2 diffuses in the opposite direction.

• The mucus traps particulate matter and the cilia sweeps it out.

• The thinnest bronchioles are dead end sacs called alveoli, have a high SA.

• O2 dissolves in the moist film covering the epithelium and quickly diffuses into the web of capillaries surrounding the alveolus.

• CO2 diffuses in the opposite direction.

BreathingBreathing

• The diffusion of a gas depends on partial pressures.

• When water is exposed to air, the amount of gas dissolved in the water is proportional to the partial pressure in the air, and its solubility in water.

• Gases always diffuse from regions of high partial pressure to regions of low partial pressure.

• The diffusion of a gas depends on partial pressures.

• When water is exposed to air, the amount of gas dissolved in the water is proportional to the partial pressure in the air, and its solubility in water.

• Gases always diffuse from regions of high partial pressure to regions of low partial pressure.

BreathingBreathing

• Positive pressure breathing-amphibians

• Negative pressure breathing-humans• Tidal volume is the volume of air inhaled with each breath.• Max. during forced breathing is 3-4.8L

• Residual volume is the amount remaining in the lungs after a forced exhale.

• Positive pressure breathing-amphibians

• Negative pressure breathing-humans• Tidal volume is the volume of air inhaled with each breath.• Max. during forced breathing is 3-4.8L

• Residual volume is the amount remaining in the lungs after a forced exhale.

BreathingBreathing

• Human breathing is mostly under autonomic control.

• 2 regions of the brain control this:• The pons and the medulla.

• The pons controls the medulla which sets a basic breathing rhythm.

• Human breathing is mostly under autonomic control.

• 2 regions of the brain control this:• The pons and the medulla.

• The pons controls the medulla which sets a basic breathing rhythm.

BreathingBreathing

• Sensors in the aorta and carotid arteries exert secondary control over breathing.

• These sensors monitor O2, CO2 and blood pH.

• The pH is largely controlled by CO2 levels.

• Sensors in the aorta and carotid arteries exert secondary control over breathing.

• These sensors monitor O2, CO2 and blood pH.

• The pH is largely controlled by CO2 levels.

BreathingBreathing

• When CO2 levels increase, carbonic acid levels increase lowering the blood pH.

• When pH drops, the depth and rate of breathing increases helping to remove excess CO2.

• O2 levels only have an effect on breathing rate at high altitudes.

• When CO2 levels increase, carbonic acid levels increase lowering the blood pH.

• When pH drops, the depth and rate of breathing increases helping to remove excess CO2.

• O2 levels only have an effect on breathing rate at high altitudes.

BreathingBreathing

• In addition to transporting O2, hemoglobin helps transport CO2 and assists in buffering.

• Respiring cells produce CO2. Carbonic anhydrase catalyzes the reaction of CO2 with H2O to form H2CO3.

• H2CO3 dissociates into H+ + HCO3-

• Most of the H+ attaches to hemoglobin and other proteins minimizing the change in blood pH.

• In addition to transporting O2, hemoglobin helps transport CO2 and assists in buffering.

• Respiring cells produce CO2. Carbonic anhydrase catalyzes the reaction of CO2 with H2O to form H2CO3.

• H2CO3 dissociates into H+ + HCO3-

• Most of the H+ attaches to hemoglobin and other proteins minimizing the change in blood pH.

BreathingBreathing

• HCO3- diffuses into the plasma.

• As blood flows through the lungs, the process is reversed.

• Diffusion of CO2 out of the blood shifts the chemical equilibrium in favor of the conversion of HCO3

- to CO2.

• HCO3- diffuses into the plasma.

• As blood flows through the lungs, the process is reversed.

• Diffusion of CO2 out of the blood shifts the chemical equilibrium in favor of the conversion of HCO3

- to CO2.

Documents

Chapter 42 Circulation and Gas Exchange. Material Exchange The exchange of materials from inside to outside is an important function for organisms. It’s