chapter 42 circulation & gas exchange. the basic idea oxygen molecules need to diffuse into the...

Chapter 42Chapter 42

Circulation & Gas ExchangeCirculation & Gas Exchange

The Basic IdeaThe Basic Idea

Oxygen molecules need to diffuse into the Oxygen molecules need to diffuse into the body fluid and carbon dioxide molecules body fluid and carbon dioxide molecules need to diffuse out. need to diffuse out.

In humans, oxygen molecules diffuse out of the In humans, oxygen molecules diffuse out of the lungs & into the blood while carbon dioxide lungs & into the blood while carbon dioxide does the opposite. Fluid movement of the does the opposite. Fluid movement of the circulatory system, powered by the heart, circulatory system, powered by the heart, carries oxygenated blood to all parts of the carries oxygenated blood to all parts of the body. Oxygen diffuses out of the blood, into body. Oxygen diffuses out of the blood, into interstitial fluid & then into the cells.interstitial fluid & then into the cells.

CirculationCirculation

1.) Gastrovascular cavities 1.) Gastrovascular cavities (Cnidarians, flatworms)(Cnidarians, flatworms)

a.) A sac with one opening. Body a.) A sac with one opening. Body wall surrounding cavity is only a wall surrounding cavity is only a couple cells thick – oxygen & couple cells thick – oxygen & nutrients dissolve directly from nutrients dissolve directly from cavity & into cells. cavity & into cells.

CirculationCirculation

2.) Open Circulatory System (most arthropods & 2.) Open Circulatory System (most arthropods & molluscs)molluscs)

a.) No distinction between the blood & a.) No distinction between the blood & interstitial fluid. Call this general body fluid interstitial fluid. Call this general body fluid hemolymph.hemolymph.

b.) 1 or more hearts pump hemolymph into a b.) 1 or more hearts pump hemolymph into a system of spaces (or sinuses) that surround system of spaces (or sinuses) that surround the organs so that chemical exchange can the organs so that chemical exchange can take place between the cells and the take place between the cells and the hemolymphhemolymph

CirculationCirculation

3.) Closed circulatory system (earthworms, 3.) Closed circulatory system (earthworms, squid, octopi, ALL vertebrates)squid, octopi, ALL vertebrates)

a.) Blood is confined to vessels & is a.) Blood is confined to vessels & is distinct from interstitial fluid.distinct from interstitial fluid.

b.) Heart pumps blood into large vessels b.) Heart pumps blood into large vessels that branch into smaller and smaller that branch into smaller and smaller vessels that infiltrate all organs. Chemical vessels that infiltrate all organs. Chemical exchange takes place by diffusion exchange takes place by diffusion between the blood & the interstitial fluid between the blood & the interstitial fluid surrounding the cells.surrounding the cells.

CirculationCirculation

4.) Closed vs. Open Circulation – 4.) Closed vs. Open Circulation – Advantages?Advantages?

a.) Open: requires less energy due to a.) Open: requires less energy due to lower “blood” pressure, requires less lower “blood” pressure, requires less maintenance because the system of maintenance because the system of vessels is not as extensive or complicatedvessels is not as extensive or complicated

b.) Closed: more effective at transporting b.) Closed: more effective at transporting blood to meet higher metabolic demands blood to meet higher metabolic demands of larger & more active animals.of larger & more active animals.

Vertebrate CirculationVertebrate Circulation

1.) Closed circulatory system = 1.) Closed circulatory system = cardiovascular system (“vascular” cardiovascular system (“vascular” refers to blood vessels)refers to blood vessels)

2.) Vertebrate heart has one or more 2.) Vertebrate heart has one or more atria (singular=atrium) which receive atria (singular=atrium) which receive blood AND one of more ventricles blood AND one of more ventricles which pump blood out of heart.which pump blood out of heart.

Vertebrate CirculationVertebrate Circulation3.) Vessels3.) Vessels

a.) Arteries: carry blood AWAY from the a.) Arteries: carry blood AWAY from the heart. They branch into arterioles & then heart. They branch into arterioles & then into capillaries.into capillaries.

b.) Capillaries: microscopic vessels with b.) Capillaries: microscopic vessels with very thin, porous walls. Networks of these very thin, porous walls. Networks of these called capillary beds infiltrate all tissues & called capillary beds infiltrate all tissues & organs. It is across the walls of the organs. It is across the walls of the capillaries that diffusion takes place.capillaries that diffusion takes place.

Vertebrate CirculationVertebrate Circulation

c.) At their “downstream” end, c.) At their “downstream” end, capillaries converge into vessels capillaries converge into vessels called venules which then converge called venules which then converge into veins. Veins carry blood into veins. Veins carry blood TOWARD the heart.TOWARD the heart.

Survey of Vertebrate CV SystemsSurvey of Vertebrate CV Systems1.) Fish1.) Fish

a.) Heart has 1 ventricle & 1 atriuma.) Heart has 1 ventricle & 1 atrium

b.) Blood pumped from ventricle goes to capillary b.) Blood pumped from ventricle goes to capillary beds in gills to pick up oxygen & drop off carbon beds in gills to pick up oxygen & drop off carbon dioxide.dioxide.

c.) Gill capillaries converge into a vessel that carries c.) Gill capillaries converge into a vessel that carries blood to all other capillary beds in the fish body to blood to all other capillary beds in the fish body to drop off oxygen. drop off oxygen.

i.) The single pump of the heart to send blood i.) The single pump of the heart to send blood to gills to gills and to body results in a lower blood and to body results in a lower blood pressure and pressure and slower delivery of oxygen to body slower delivery of oxygen to body cells.cells.

Survey of Vertebrate CV Survey of Vertebrate CV SystemsSystems

2.) Amphibians2.) Amphibians

a.) Heart has 2 atria and 1 ventricle.a.) Heart has 2 atria and 1 ventricle.

b.) Ventricle pumps blood into an artery that splits b.) Ventricle pumps blood into an artery that splits – some blood goes to lungs to pick up oxygen/drop – some blood goes to lungs to pick up oxygen/drop off carbon dioxide and the rest goes to the body off carbon dioxide and the rest goes to the body (systemic circulation).(systemic circulation).

c.) Blood from lungs goes back to left side of heart c.) Blood from lungs goes back to left side of heart to be pumped to body and blood from body to be pumped to body and blood from body returns to right side of heart to be pumped to returns to right side of heart to be pumped to lungs.lungs.

Survey of Vertebrate CV Survey of Vertebrate CV SystemsSystems

d.) Since there is only 1 ventricle, there is d.) Since there is only 1 ventricle, there is mixing of oxygenated & deoxygenated mixing of oxygenated & deoxygenated blood.blood.

e.) However, the amphibian heart does e.) However, the amphibian heart does pump twice (once to pump to lungs & pump twice (once to pump to lungs & again to pump to body) resulting in higher again to pump to body) resulting in higher blood pressure & better blood flow.blood pressure & better blood flow.

i.) This is called double circulation i.) This is called double circulation (for the 2 (for the 2 pumps).pumps).

Survey of Vertebrate CV Survey of Vertebrate CV SystemsSystems

3.) Reptiles3.) Reptiles

a.) Similar to amphibians except a.) Similar to amphibians except there is a partial septum (wall) to there is a partial septum (wall) to further divide the ventricle into right further divide the ventricle into right & left sides. This prevents most of & left sides. This prevents most of the mixing of oxygenated & the mixing of oxygenated & deoxygenated blood. deoxygenated blood.

Survey of Vertebrate CV SystemsSurvey of Vertebrate CV Systems

4.) Mammals & Birds4.) Mammals & Birds

a.) Heart has 4 chambers – right & left atria a.) Heart has 4 chambers – right & left atria and right & left ventricleand right & left ventricle

b.) The left side of the heart receives b.) The left side of the heart receives oxygenated blood from lungs & pumps to oxygenated blood from lungs & pumps to body.body.

c.) The right side of the heart receives c.) The right side of the heart receives deoxygenated blood & pumps to lungs.deoxygenated blood & pumps to lungs.

Survey of Vertebrate CV Survey of Vertebrate CV SystemsSystems

d.) The structure of the 4 chambered d.) The structure of the 4 chambered heart enabled the success of heart enabled the success of endotherms. To maintain body heat they endotherms. To maintain body heat they need to make a lot of ATP which requires need to make a lot of ATP which requires fast & efficient delivery of nutrients & fast & efficient delivery of nutrients & oxygen. oxygen.

i.) Separate pulmonary & systemic i.) Separate pulmonary & systemic circuits (along with double circuits (along with double

circulation) circulation) allows for greater/faster allows for greater/faster blood blood flow.flow.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

1.) Deoxygenated blood returning from 1.) Deoxygenated blood returning from the body (from the systemic circuit) the body (from the systemic circuit) empties into the right atrium.empties into the right atrium.

2.) Right atrium empties into right 2.) Right atrium empties into right ventricleventricle

3.) Right ventricle pumps blood out the 3.) Right ventricle pumps blood out the pulmonary arteries to the lungs.pulmonary arteries to the lungs.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

a.) As blood flows through capillary beds in a.) As blood flows through capillary beds in the lungs, it unloads carbon dioxide and the lungs, it unloads carbon dioxide and picks up oxygen (by diffusion out of/into picks up oxygen (by diffusion out of/into capillaries).capillaries).

4.) Oxygenated blood returns to left atrium 4.) Oxygenated blood returns to left atrium of heart via the pulmonary veins.of heart via the pulmonary veins.

5.) Left atrium empties into left ventricle of 5.) Left atrium empties into left ventricle of heart.heart.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

6.) Left ventricle pumps blood out of 6.) Left ventricle pumps blood out of the heart through a large vessel the heart through a large vessel called the aorta (to enter the called the aorta (to enter the systemic circuit – go to body)systemic circuit – go to body)

7.) The aorta branches into smaller 7.) The aorta branches into smaller arteries, including coronary arteries arteries, including coronary arteries that supply blood to the heart itself.that supply blood to the heart itself.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

9.) The arteries lead to smaller vessels 9.) The arteries lead to smaller vessels (arterioles) and finally branch into capillary (arterioles) and finally branch into capillary beds throughout the body.beds throughout the body.

a.) In capillary beds, oxygen diffuses out a.) In capillary beds, oxygen diffuses out of capillaries & into the interstitial fluid & of capillaries & into the interstitial fluid & then body cells.then body cells.

b.) Carbon dioxide (produced by cellular b.) Carbon dioxide (produced by cellular respiration) diffuses into capillaries.respiration) diffuses into capillaries.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

10.) Capillaries rejoin into small venules 10.) Capillaries rejoin into small venules and then into larger veins.and then into larger veins.

a.) All veins in the head, neck & a.) All veins in the head, neck & arms arms empty into a large vein called empty into a large vein called superior superior vena cava.vena cava.

b.) All veins from the trunk & legs b.) All veins from the trunk & legs empty into the inferior vena cava.empty into the inferior vena cava.

Pathway of Circulation (In Pathway of Circulation (In Humans)Humans)

11.) The inferior & superior vena cava 11.) The inferior & superior vena cava empty into the right atrium of the empty into the right atrium of the heart…& the cycle begins again. heart…& the cycle begins again.

The HeartThe Heart

1.) Made mostly of cardiac muscle tissue.1.) Made mostly of cardiac muscle tissue.

a.) The 2 atria have fairly thin walls & a.) The 2 atria have fairly thin walls & serve as collection chambers for blood.serve as collection chambers for blood.

b.) The walls of the ventricles are thick b.) The walls of the ventricles are thick & muscular for contracting to pump & muscular for contracting to pump blood.blood.

The HeartThe Heart

2.) Cardiac cycle: one complete 2.) Cardiac cycle: one complete sequence of pumping & fillingsequence of pumping & filling

a.) When the heart contracts, it a.) When the heart contracts, it pumps blood. This is called the pumps blood. This is called the systole phase of the cycle.systole phase of the cycle.

b.) When it relaxes, it fills with blood. b.) When it relaxes, it fills with blood. This is the diastole phase of the cycle.This is the diastole phase of the cycle.

The HeartThe Heart

3.) The heart has 4 valves to prevent 3.) The heart has 4 valves to prevent backflow of blood (to keep it moving backflow of blood (to keep it moving in the right direction).in the right direction).

a.) Between each atrium & ventricle a.) Between each atrium & ventricle is an atrioventricular (AV) valve. The is an atrioventricular (AV) valve. The AV valves close when the ventricles AV valves close when the ventricles contract.contract.

The HeartThe Heart

b.) At the 2 exits of the heart (to the b.) At the 2 exits of the heart (to the aorta & to the pulmonary arteries) aorta & to the pulmonary arteries) are semilunar valves.are semilunar valves.

i.) These valves are forced open i.) These valves are forced open by the by the contraction of the ventricles contraction of the ventricles & close as & close as the ventricle relaxes.the ventricle relaxes.

The HeartThe Heart

c.) Heart sounds (“lub-dup”) are caused c.) Heart sounds (“lub-dup”) are caused by the closing of the valves.by the closing of the valves.

i.) The “lub” is caused by the recoil i.) The “lub” is caused by the recoil of of blood against the closed AV valves.blood against the closed AV valves.

ii.) The “dup” is caused by recoil of ii.) The “dup” is caused by recoil of blood against the semilunar valves.blood against the semilunar valves.

The HeartThe Heart

4.) You can measure your heart rate 4.) You can measure your heart rate by measuring your pulse.by measuring your pulse.

a.) Your pulse is the result of the a.) Your pulse is the result of the stretching of arteries caused by the stretching of arteries caused by the pressure of blood driven by the pressure of blood driven by the contraction of the ventricle.contraction of the ventricle.

The HeartThe Heart5.) Maintaining the heart’s beat:5.) Maintaining the heart’s beat:

a.) Many cardiac muscle cells will contract on their a.) Many cardiac muscle cells will contract on their own – without any signal from the nervous system. own – without any signal from the nervous system. Their individual contractions must be coordinated.Their individual contractions must be coordinated.

b.) A region of the heart (located in the wall of the b.) A region of the heart (located in the wall of the right atrium) called the sinoatrial (SA) node, or right atrium) called the sinoatrial (SA) node, or pacemaker, generates electrical impulses that pacemaker, generates electrical impulses that spread from the node to the walls of the atria.spread from the node to the walls of the atria.

i.) This causes the cells of the atria to i.) This causes the cells of the atria to contract in contract in unison.unison.

The HeartThe Heartc.) The impulse passes to the c.) The impulse passes to the atrioventricular (AV) node located in the atrioventricular (AV) node located in the wall between the RA and RV.wall between the RA and RV.

i.) Specialized muscle fibers leading i.) Specialized muscle fibers leading from this from this node then conduct (after a short node then conduct (after a short delay) the delay) the impulses to the bottom impulses to the bottom (apex) of the heart & (apex) of the heart & the ventricle walls the ventricle walls causing them to contract.causing them to contract.

ii.) The short delay allows the atria to ii.) The short delay allows the atria to fully fully empty before the ventricles contract.empty before the ventricles contract.

The HeartThe Heart

d.) The SA node sets the pace, but it is d.) The SA node sets the pace, but it is influenced by many factors.influenced by many factors.

i.) It is infiltrated by nerve cells that i.) It is infiltrated by nerve cells that can can speed up or slow down the pace.speed up or slow down the pace.

ii.) Hormones (such as epinephrine) ii.) Hormones (such as epinephrine) can increase heart rate as can a can increase heart rate as can a

higher higher body temperature and exercise.body temperature and exercise.

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Blood CirculationBlood Circulation

1.) Arteries & veins are composed of 3 layers 1.) Arteries & veins are composed of 3 layers of tissues including elastic connective tissue of tissues including elastic connective tissue to allow for stretch and recoil. The innermost to allow for stretch and recoil. The innermost layer is a smooth single layer of cells – an layer is a smooth single layer of cells – an endothelium.endothelium.

a.) The walls of arteries are typically thicker a.) The walls of arteries are typically thicker because blood is flowing at a greater because blood is flowing at a greater pressure.pressure.

2.) Capillaries only have the single layer of 2.) Capillaries only have the single layer of smooth cells – very thin to allow for diffusion. smooth cells – very thin to allow for diffusion.

Blood CirculationBlood Circulation

3.) Blood flows more slowly through 3.) Blood flows more slowly through the capillary beds – this also the capillary beds – this also facilitates diffusion. facilitates diffusion.

Blood PressureBlood Pressure1.) Blood pressure is greater in arteries than veins & 1.) Blood pressure is greater in arteries than veins &

is highest during contraction of the ventricles – is highest during contraction of the ventricles – during systole. during systole.

a.) This is called the systolic pressure.a.) This is called the systolic pressure.

2.) Even during relaxation (diastole) there is still 2.) Even during relaxation (diastole) there is still substantial pressure in the arteries. This is substantial pressure in the arteries. This is because blood flows into the arteries faster than it because blood flows into the arteries faster than it can leave into the arterioles & the heart contracts can leave into the arterioles & the heart contracts again before the arteries are completely emptied.again before the arteries are completely emptied.

b.) The pressure during the relaxation phase is b.) The pressure during the relaxation phase is the diastolic pressure.the diastolic pressure.

Blood PressureBlood Pressure

3.) By the time blood reaches 3.) By the time blood reaches venules/veins the pressure is very low.venules/veins the pressure is very low.

a.) Blood gets back to the heart a.) Blood gets back to the heart because smooth muscles in the walls because smooth muscles in the walls of venules & veins contract. of venules & veins contract. Additionally, the contraction of your Additionally, the contraction of your skeletal muscles during exercise skeletal muscles during exercise squeezes blood through the veins. squeezes blood through the veins.

Fluid Loss from CV SystemFluid Loss from CV System

1.) In capillary beds, materials are 1.) In capillary beds, materials are constantly diffusing out of capillaries constantly diffusing out of capillaries & into interstitial fluid to deliver & into interstitial fluid to deliver nutrients & oxygen to all cells.nutrients & oxygen to all cells.

2.) However, there is a lot of fluid loss 2.) However, there is a lot of fluid loss from the blood (blood cells stay in from the blood (blood cells stay in capillaries because they are too big to capillaries because they are too big to diffuse out). What happens to all this? diffuse out). What happens to all this?

Fluid Loss from CV SystemFluid Loss from CV System

3.) Intermingling with CV capillaries are 3.) Intermingling with CV capillaries are capillaries of the lymphatic system. capillaries of the lymphatic system.

a.) Lost fluid from the blood diffuses into a.) Lost fluid from the blood diffuses into these vessels – we now call the fluid lymph. these vessels – we now call the fluid lymph.

b.) Lymphatic system vessels drain back b.) Lymphatic system vessels drain back into the CV system near the junction of the into the CV system near the junction of the vena cava with the right atrium. vena cava with the right atrium.

Fluid Loss from CV SystemFluid Loss from CV System

4.) Along the lymph vessels are organs 4.) Along the lymph vessels are organs called lymph nodes.called lymph nodes.

a.) The tissue of lymph nodes is filled a.) The tissue of lymph nodes is filled with white blood cells. with white blood cells.

b.) The tissue filters the lymph and the b.) The tissue filters the lymph and the WBC attack any bacteria or viruses. WBC attack any bacteria or viruses.

Blood CompositionBlood Composition

1.) Blood consists of cells suspended in plasma.1.) Blood consists of cells suspended in plasma.

2.) Plasma: about 90% water. Contains solutes 2.) Plasma: about 90% water. Contains solutes such as inorganic salts in the form of ions. such as inorganic salts in the form of ions.

a.) These solutes help maintain the osmotic a.) These solutes help maintain the osmotic balance of the blood and pH. The normal balance of the blood and pH. The normal functioning nerves/muscles depends on functioning nerves/muscles depends on appropriate concentrations of these ions. appropriate concentrations of these ions.

b.) Plasma also contains blood proteins which b.) Plasma also contains blood proteins which function in nutrient transport, clotting, immune function in nutrient transport, clotting, immune system function (antibodies), etc.system function (antibodies), etc.

Blood CompositionBlood Composition3.) Erythrocytes (red blood cells): most numerous cells 3.) Erythrocytes (red blood cells): most numerous cells

in blood. Function = transport oxygen.in blood. Function = transport oxygen.

a.) Small & thin with concave shape on each side of a.) Small & thin with concave shape on each side of cell. Shape increases surface area for diffusion of cell. Shape increases surface area for diffusion of oxygen. oxygen.

b.) Lack nuclei & mitochondria in order to have more b.) Lack nuclei & mitochondria in order to have more room for hemoglobin – the protein molecule that room for hemoglobin – the protein molecule that actually binds to oxygen. actually binds to oxygen.

i.) Get energy through fermentation.i.) Get energy through fermentation.

c.) Each RBC contains about 250 million hemoglobin c.) Each RBC contains about 250 million hemoglobin molecules each of which can bind to 4 oxygen molecules each of which can bind to 4 oxygen molecules – so, one RBC can transport 1 billion oxygen molecules – so, one RBC can transport 1 billion oxygen molecules.molecules.

Blood CompositionBlood Composition4.) Blood also contains leukocytes (white 4.) Blood also contains leukocytes (white

blood cells). blood cells).

a.) There are 5 major types. Function = a.) There are 5 major types. Function = fight infections.fight infections.

5.) Platelets – fragments of cells that function 5.) Platelets – fragments of cells that function in blood clotting. in blood clotting.

a.) When vessels are damaged, release a.) When vessels are damaged, release clotting factors that trigger proteins to clotting factors that trigger proteins to coagulate around injury.coagulate around injury.

Blood CompositionBlood Composition

6.) Erythrocytes, leukocytes & platelets 6.) Erythrocytes, leukocytes & platelets are replaced continuously throughout are replaced continuously throughout life.life.

a.) They are produced by stem cells in a.) They are produced by stem cells in our bone marrow. our bone marrow.

b.) These stems cells are termed b.) These stems cells are termed pluripotent – means they can become pluripotent – means they can become any type of blood cell. any type of blood cell.

Blood CompositionBlood Composition

c.) Production of blood cells is controlled c.) Production of blood cells is controlled by feedback mechanisms. If oxygen levels by feedback mechanisms. If oxygen levels fall, the kidneys secrete a hormone that fall, the kidneys secrete a hormone that triggers stem cells to produce triggers stem cells to produce erythrocytes. erythrocytes.

i.) Synthetic forms of the hormone i.) Synthetic forms of the hormone are used are used to treat anemia. Athletes have to treat anemia. Athletes have also used it to also used it to increase their increase their concentrations of red blood concentrations of red blood cells!cells!

Cardiovascular DiseaseCardiovascular Disease

1.) Has genetic components but lifestyles put 1.) Has genetic components but lifestyles put people at risk. people at risk.

a.) Risk factors include: smoking, lack of a.) Risk factors include: smoking, lack of exercise, diet high in fat & cholesterol, high exercise, diet high in fat & cholesterol, high blood pressure.blood pressure.

2.) Cholesterol builds up in the walls of 2.) Cholesterol builds up in the walls of arteries, significantly narrowing them over arteries, significantly narrowing them over time.time.

Cardiovascular DiseaseCardiovascular Disease

a.) Narrowing (and eventual hardening) of a.) Narrowing (and eventual hardening) of the arteries is called atherosclerosis. the arteries is called atherosclerosis.

b.) If arteries become completely blocked, b.) If arteries become completely blocked, blood flow stops to tissues down stream.blood flow stops to tissues down stream.

c.) Complete blockage in the coronary c.) Complete blockage in the coronary arteries on the surface of the heart causes arteries on the surface of the heart causes heart attack. Blockage of vessels leading heart attack. Blockage of vessels leading to brain causes stroke. to brain causes stroke.

Chapter 42 – Part 2Chapter 42 – Part 2

Gas ExchangeGas Exchange

Gas ExchangeGas Exchange

1.) Gas exchange = the exchange of 1.) Gas exchange = the exchange of oxygen & carbon dioxideoxygen & carbon dioxide

2.) Respiratory surfaces: thin with a 2.) Respiratory surfaces: thin with a large surface area to maximize the large surface area to maximize the rate of gas exchange (by diffusion). rate of gas exchange (by diffusion). Also are moist since all cells must be Also are moist since all cells must be bathed in water.bathed in water.

Respiratory OrgansRespiratory Organs

1.) Gills: outfoldings of body surface 1.) Gills: outfoldings of body surface suspended in water.suspended in water.

a.) Since the concentration of a.) Since the concentration of oxygen is much lower in water than oxygen is much lower in water than in air, gills must be efficient. in air, gills must be efficient.

b.) Aquatic organs ventilate their b.) Aquatic organs ventilate their gills with a continuous flow of water. gills with a continuous flow of water.

Respiratory OrgansRespiratory Organsc.) Capillaries surrounding gills are arranged c.) Capillaries surrounding gills are arranged so that blood flows in the opposite direction of so that blood flows in the opposite direction of water moving past gills.water moving past gills.

i.) Therefore, as blood moves through a i.) Therefore, as blood moves through a capillary it gains more & more oxygen but it capillary it gains more & more oxygen but it keeps encountering water with a higher keeps encountering water with a higher oxygen concentration so oxygen keeps oxygen concentration so oxygen keeps diffusing into the blood down its concentration diffusing into the blood down its concentration

gradient. gradient.

ii.) This is called countercurrent ii.) This is called countercurrent exchange.exchange.

Respiratory OrgansRespiratory Organs

2.) Tracheal system (insects): air tubes that 2.) Tracheal system (insects): air tubes that branch throughout the body. branch throughout the body.

3.) Lungs (all vertebrates): the respiratory surface 3.) Lungs (all vertebrates): the respiratory surface of the lungs is not in direct contact with the entire of the lungs is not in direct contact with the entire body so the circulatory system must transport body so the circulatory system must transport gases between the lungs & the rest of the body. gases between the lungs & the rest of the body.

a.) Internal respiratory systems are necessary for a.) Internal respiratory systems are necessary for land animals so that water isn’t lost by land animals so that water isn’t lost by evaporation from the moist gas exchange evaporation from the moist gas exchange surface.surface.

The Lungs & Gas ExchangeThe Lungs & Gas Exchange

1.) Air enters through the nose or mouth and 1.) Air enters through the nose or mouth and passes into the trachea.passes into the trachea.

2.) The trachea splits into 2 tubes – the bronchi 2.) The trachea splits into 2 tubes – the bronchi (singular = bronchus), one leading to each lung. (singular = bronchus), one leading to each lung.

3.) Within each lung, the bronchi branch into 3.) Within each lung, the bronchi branch into smaller and smaller tubes called bronchioles. smaller and smaller tubes called bronchioles.

a.) The bronchi/bronchioles are covered by cilia & a.) The bronchi/bronchioles are covered by cilia & mucus to trap particulates in the air. The cilia mucus to trap particulates in the air. The cilia move the mucus up to the throat to be swallowed. move the mucus up to the throat to be swallowed.

The Lungs & Gas ExchangeThe Lungs & Gas Exchange

4.) The bronchioles dead end into clusters of air sacs 4.) The bronchioles dead end into clusters of air sacs called alveoli.called alveoli.

a.) It is across the surface of the alveoli that gas a.) It is across the surface of the alveoli that gas exchange takes place. exchange takes place.

b.) The alveoli are surrounded by webs of b.) The alveoli are surrounded by webs of capillaries.capillaries.

c.) Oxygen diffuses out of alveoli & into capillaries c.) Oxygen diffuses out of alveoli & into capillaries and carbon dioxide does the opposite. and carbon dioxide does the opposite.

d.) The alveoli have a total surface area of 100 md.) The alveoli have a total surface area of 100 m22!!

BreathingBreathing

1.) Mammals breathe by contracting rib 1.) Mammals breathe by contracting rib muscles & the diaphragm which is sheet of muscles & the diaphragm which is sheet of skeletal muscle that forms the bottom of our skeletal muscle that forms the bottom of our chest cavity.chest cavity.

a.) When these muscles contract, lung a.) When these muscles contract, lung volume increases & air pressure within the volume increases & air pressure within the alveoli lowers. Air moves from higher air alveoli lowers. Air moves from higher air pressure (outside the body) to lower (inside pressure (outside the body) to lower (inside the lungs). the lungs).

2.) When these muscles relax, the opposite 2.) When these muscles relax, the opposite happens & we exhale. happens & we exhale.

BreathingBreathing

3.) Breathing is controlled by regions in the brain 3.) Breathing is controlled by regions in the brain called the pons & medulla oblongata. called the pons & medulla oblongata.

a.) The medulla regulates breathing in response a.) The medulla regulates breathing in response to pH changes in the fluid bathing the brain.to pH changes in the fluid bathing the brain.

b.) When carbon dioxide diffuses out of cells, it b.) When carbon dioxide diffuses out of cells, it reacts with water to form carbonic acid. This reacts with water to form carbonic acid. This lowers the pH of the fluid bathing the brain. lowers the pH of the fluid bathing the brain.

c.) The medulla registers this lower pH and c.) The medulla registers this lower pH and speeds up the rate & depth of breathing. This is speeds up the rate & depth of breathing. This is what triggers you to breathe faster during heavy what triggers you to breathe faster during heavy activity. activity.

Oxygen TransportOxygen Transport

1.) Oxygen binds to the protein 1.) Oxygen binds to the protein hemoglobin contained within red blood hemoglobin contained within red blood cells. cells.

a.) The subunits of this protein display a.) The subunits of this protein display cooperativity. When one oxygen cooperativity. When one oxygen molecule binds to a subunit, it causes the molecule binds to a subunit, it causes the others to change shape slightly which others to change shape slightly which increases their oxygen affinity. The same increases their oxygen affinity. The same thing happens when oxygen is unloaded. thing happens when oxygen is unloaded.

Oxygen TransportOxygen Transport

2.) A drop in pH lowers the affinity of 2.) A drop in pH lowers the affinity of hemoglobin for oxygen – this is called hemoglobin for oxygen – this is called the Bohr shift.the Bohr shift.

a.) So when carbon dioxide increase, a.) So when carbon dioxide increase, it lowers pH which makes hemoglobin it lowers pH which makes hemoglobin release oxygen more quickly so that it release oxygen more quickly so that it can be used for cellular respiration.can be used for cellular respiration.

Carbon Dioxide TransportCarbon Dioxide Transport

1.) Carbon dioxide is transported in a variety 1.) Carbon dioxide is transported in a variety of ways: some is dissolved in solution in of ways: some is dissolved in solution in blood plasma, some binds to subunits on blood plasma, some binds to subunits on hemoglobin and most is transported as hemoglobin and most is transported as bicarbonate ions (after reacting to form bicarbonate ions (after reacting to form carbonic acid, it dissociates into hydrogen & carbonic acid, it dissociates into hydrogen & bicarbonate ions). bicarbonate ions).

a.) When it reaches lungs, it is converted a.) When it reaches lungs, it is converted back to carbon dioxide and diffuses into back to carbon dioxide and diffuses into alveoli & out of body through exhalation. alveoli & out of body through exhalation.

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