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Chapter 42: Gas Exchange and Circulatory System. Presented by: McQuade and Verpooten. Circulatory Systems Reflect Phylogeny. In unicellular organisms Exchanges occur directly with the environment For most of the cells making up multicellular organisms

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Chapter 42 gas exchange and circulatory system

Chapter 42: Gas Exchange and Circulatory System

Presented by: McQuade and Verpooten


Circulatory systems reflect phylogeny
Circulatory Systems Reflect Phylogeny

  • In unicellular organisms

    • Exchanges occur directly with the environment

  • For most of the cells making up multicellular organisms

    • Direct exchange with the environment is not possible


Gastrovascular cavities
Gastrovascular Cavities

  • Wide diversity of animals is paralleled by the diversity in circulatory systems.

  • Simple animals, such as cnidarians

    • Have a body wall only two cells thick that encloses a gastrovascular cavity

  • The gastrovascular cavity

    • Functions in both digestion and distribution of substances throughout the body

    • http://bcs.whfreeman.com/thelifewire/content/chp32/32020.html


Open and closed circulatory systems overcome limitations of diffusion
Open and Closed Circulatory Systems Overcome limitations of Diffusion

  • More complex animals

    • Have one of two types of circulatory systems: open or closed

  • Both of these types of systems have three basic components

    • A circulatory fluid (blood)

    • A set of tubes (blood vessels)

    • A muscular pump (the heart)


Heart Diffusion

Hemolymph in sinusessurrounding ograns

Ostia

Anterior vessel

Lateral vessels

Tubular heart

Figure 42.3a

(a) An open circulatory system

  • In insects, other arthropods, and most molluscs

    • Blood bathes the organs directly in an open circulatory system

https://www.youtube.com/watch?v=vGriV82EyeA


Heart Diffusion

Interstitialfluid

Small branch vessels in each organ

Dorsal vessel(main heart)

Ventral vessels

Auxiliary hearts

(b) A closed circulatory system

Figure 42.3b

  • In a closed circulatory system

    • Blood is confined to vessels and is distinct from the interstitial fluid


Survey of vertebrate circulation
Survey of Vertebrate Circulation Diffusion

  • Humans and other vertebrates have a closed circulatory system

    • Often called the cardiovascular system

    • Clearly the most advanced/efficient system

  • Blood flows in a closed cardiovascular system

    • Consisting of blood vessels and a two- to four-chambered heart


3 main types of blood vessels arteries veins capillaries
3 Main Types of Blood Vessels: Arteries, Veins, & Capillaries

  • Arteries carry blood to capillaries

    • The sites of chemical exchange between the blood and interstitial fluid

  • Veins

    • Return blood from capillaries to the heart


Fishes
Fishes Capillaries

  • A fish heart has two main chambers

    • One ventricle and one atrium

  • Blood pumped from the ventricle

    • Travels to the gills, where it picks up O2 and disposes of CO2


Amphibians
Amphibians Capillaries

  • Frogs and other amphibians

    • Have a three-chambered heart, with two atria and one ventricle

  • The ventricle pumps blood into a forked artery

    • That splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit


Reptiles except birds
Reptiles (Except Birds) Capillaries

  • Reptiles have double circulation

    • With a pulmonary circuit (lungs) and a systemic circuit

  • Turtles, snakes, and lizards

    • Have a three-chambered heart


Mammals and birds
Mammals and Birds Capillaries

  • In all mammals and birds

    • The ventricle is completely divided into separate right and left chambers

  • The left side of the heart pumps and receives only oxygen-rich blood

    • While the right side receives and pumps only oxygen-poor blood

  • A powerful four-chambered heart

    • Was an essential adaptation of the endothermic way of life characteristic of mammals and birds


Gill capillaries Capillaries

Lung and skin capillaries

Lung capillaries

Lung capillaries

AMPHIBIANS

REPTILES (EXCEPT BIRDS)

MAMMALS AND BIRDS

FISHES

Right systemicaorta

Pulmonarycircuit

Artery

Pulmocutaneouscircuit

Pulmonarycircuit

Gillcirculation

Heart:ventricle (V)

Left

Systemicaorta

A

A

A

A

A

A

Atrium (A)

V

V

V

V

V

Left

Right

Left

Left

Right

Right

Systemiccirculation

Systemic circuit

Systemic circuit

Vein

Systemic capillaries

Systemic capillaries

Systemic capillaries

Systemic capillaries

Figure 42.4

  • Vertebrate circulatory systems


  • Heart valves

    • Dictate a one-way flow of blood through the heart


  • Blood begins its flow pumping cycle of the heart

    • With the right ventricle pumping blood to the lungs

  • In the lungs

    • The blood loads O2 and unloads CO2


  • Oxygen-rich blood from the lungs pumping cycle of the heart

    • Enters the heart at the left atrium and is pumped to the body tissues by the left ventricle

  • Blood returns to the heart

    • Through the right atrium


Capillaries of pumping cycle of the heart

head and

forelimbs

Anterior

vena cava

Aorta

Pulmonary

artery

Pulmonary

artery

9

6

3

3

8

7

Capillaries

of right lung

Capillaries

of left lung

2

4

11

Pulmonary

vein

Pulmonary

vein

Left atrium

5

1

Right atrium

10

Left ventricle

Right ventricle

Aorta

Posterior

vena cava

Capillaries of

abdominal organs

and hind limbs

Figure 42.5

  • The mammalian cardiovascular system

http://www.sumanasinc.com/webcontent/animations/content/human_heart.html


The mammalian heart a closer look

Pulmonary artery pumping cycle of the heart

Aorta

Pulmonaryveins

Pulmonaryartery

Anterior vena cava

Leftatrium

Right atrium

Pulmonaryveins

Atrioventricularvalve

Semilunarvalve

Semilunarvalve

Atrioventricularvalve

Posterior vena cava

Right ventricle

Figure 42.6

Left ventricle

The Mammalian Heart: A Closer Look

  • A closer look at the mammalian heart

    • Provides a better understanding of how double circulation works

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_1_.html


  • The heart contracts and relaxes pumping cycle of the heart

    • In a rhythmic cycle called the cardiac cycle

  • The contraction, or pumping, phase of the cycle

    • Is called systole

  • The relaxation, or filling, phase of the cycle

    • Is called diastole


  • The heart rate, also called the pulse pumping cycle of the heart

    • Is the number of beats per minute

  • The cardiac output

    • Is the volume of blood pumped into the systemic circulation per minute

  • Some cardiac muscle cells are self-excitable

    • Meaning they contract without any signal from the nervous system


  • A region of the heart called the pumping cycle of the heartsinoatrial (SA) node, or pacemaker

    • Sets the rate and timing at which all cardiac muscle cells contract

  • Impulses from the SA node

    • Travel to the atrioventricular (AV) node

  • At the AV node, the impulses are delayed

    • And then travel to the Purkinje fibers that make the ventricles contract

      http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html


Signals pass pumping cycle of the heart

to heart apex.

Signals spread

Throughoutventricles.

Pacemaker generates wave of signals to contract.

Signals are delayed

at AV node.

Bundlebranches

AV node

SA node(pacemaker)

Purkinjefibers

Heartapex

ECG

2

1

3

4

Figure 42.8

  • The control of heart rhythm



Direction of blood flow pumping cycle of the heartin vein (toward heart)

Valve (open)

Skeletal muscle

Valve (closed)

Figure 42.10

  • In the thinner-walled veins

    • Blood flows back to the heart mainly as a result of muscle action


Blood pressure
Blood Pressure pumping cycle of the heart

  • Systolic pressure

    • Is the pressure in the arteries during ventricular systole

    • Is the highest pressure in the arteries

  • Diastolic pressure

    • Is the pressure in the arteries during diastole

    • Is lower than systolic pressure


  • The lymphatic system

    • Returns fluid to the body from the capillary beds

    • Aids in body defense



Blood composition and function
Blood Composition and Function interstitial fluid

  • Blood plasma is about 90% water

  • Among its many solutes are

    • Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes

  • Blood consists of several kinds of cells

    • Suspended in a liquid matrix called plasma

  • The cellular elements

    • Occupy about 45% of the volume of blood


Plasma 55% interstitial fluid

Constituent

Major functions

Solvent for

carrying other

substances

Water

Icons (blood electrolytes

Sodium

Potassium

CalciumMagnesium

Chloride

Bicarbonate

Osmotic balance

pH buffering, and

regulation of

membrane

permeability

Separatedbloodelements

Plasma proteins

Albumin

Fibringen

Immunoglobulins

(antibodies)

Osmotic balance,

pH buffering

Clotting

Defense

Substances transported by blood

Nutrients (such as glucose, fatty acids, vitamins)

Waste products of metabolism

Respiratory gases (O2 and CO2)

Hormones

Figure 42.15

  • The composition of mammalian plasma


Cellular elements
Cellular Elements interstitial fluid

  • Suspended in blood plasma are two classes of cells

    • Red blood cells, which transport oxygen

    • White blood cells, which function in defense

  • A third cellular element, platelets

    • Are fragments of cells that are involved in clotting


Separated interstitial fluidbloodelements

Cellular elements 45%

Functions

Cell type

Numberper L (mm3) of blood

  • The cellular elements of mammalian blood

Erythrocytes(red blood cells)

Transport oxygenand help transportcarbon dioxide

5–6 million

Defense andimmunity

Leukocytes(white blood cells)

5,000–10,000

Lymphocyte

Basophil

Eosinophil

Neutrophil

Monocyte

Platelets

250,000400,000

Blood clotting

Figure 42.15


Erythrocytes
Erythrocytes interstitial fluid

  • Red blood cells, or erythrocytes

    • Are by far the most numerous blood cells

    • Transport oxygen throughout the body

  • The blood contains five major types of white blood cells, or leukocytes

    • Monocytes, neutrophils, basophils, eosinophils, and lymphocytes, which function in defense by phagocytizing bacteria and debris or by producing antibodies


Pluripotent stem cells interstitial fluid(in bone marrow)

Lymphoidstem cells

Myeloidstem cells

Basophils

B cells

T cells

Lymphocytes

Eosinophils

Neutrophils

Erythrocytes

Monocytes

Platelets

Figure 42.16

  • Erythrocytes, leukocytes, and platelets all develop from a common source

    • A single population of cells called pluripotent stem cells in the red marrow of bones


Cardiovascular disease
Cardiovascular Disease interstitial fluid

  • Cardiovascular diseases

    • Are disorders of the heart and the blood vessels

    • Account for more than half the deaths in the United States


Smooth muscle interstitial fluid

Connective tissue

Plaque

Endothelium

(a) Normal artery

(b) Partly clogged artery

50 µm

250 µm

Figure 42.18a, b

  • One type of cardiovascular disease, atherosclerosis

    • Is caused by the buildup of cholesterol within arteries


  • Hypertension, or high blood pressure interstitial fluid

    • Promotes atherosclerosis and increases the risk of heart attack and stroke

  • A heart attack

    • Is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries

  • A stroke

    • Is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head


Respiratory interstitial fluidmedium(air of water)

O2

CO2

Respiratorysurface

Organismal level

Circulatory system

Cellular level

Energy-richmoleculesfrom food

ATP

Cellular respiration

Figure 42.19

Gas Exchange Occurs Across Specialized Respiratory Surfaces

  • Generally referred to as Respiration

    • Do not confuse with cellular respiration which refers energy transformations

  • Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide


Remember key biological concept….lots of body structure have numerous folds to increase surface area for chemical reaction

  • The part of an animals body where gas exchange occurs is called a respiratory surface

  • Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases

    • Between their cells and the respiratory medium, either air or water

    • Rate of diffusion is proportional to surface area across which diffusion occurs and inversely proportional to the square of the distance molecules must move

  • As a result respiratory surfaces tend to be thin and have large surface areas


Critical Thinking: Who will have more surface area in their respiratory surfaces, ectotherms or endotherms? Explain.

Endotherms. While respiratory area depends mainly on the size of the organism and whether it lives in a terrestrial or aquatic environment, endotherms utilize more energy (ATP) and so must do more cellular respiration than a similarly sized ectotherm


Skin as a respiratory organ
Skin as a Respiratory Organ respiratory surfaces, ectotherms or endotherms? Explain.

  • Some animals use entire outer skin as a respiratory organ

    • Earthworms and amphibians

  • Moist skin exchanges gasses by diffusion across entire body

    • Respiratory surface must remain moist requiring these organisms to live in water or damp places

    • Organisms usually small (thin or flat)with high surface area to volume ratios


3 most common respiratory organs
3 Most Common Respiratory Organs respiratory surfaces, ectotherms or endotherms? Explain.

  • Gills: out-foldings of body surface suspended in water

    • Respiratory medium= water

    • The warmer and saltier the water, the less dissolved O2

  • Trachea: made up of air tubes that branch throughout the body

    • Most common respiratory system of terrestrial animals (insects)

  • Lungs: most familiar respiratory system


(a) Sea star. respiratory surfaces, ectotherms or endotherms? Explain. The gills of a sea star are simple tubular projections of the skin. The hollow core of each gillis an extension of the coelom(body cavity). Gas exchangeoccurs by diffusion across thegill surfaces, and fluid in thecoelom circulates in and out ofthe gills, aiding gas transport. The surfaces of a sea star’s tube feet also function in gas exchange.

Gills

Coelom

Figure 42.20a

Tube foot

  • In some invertebrates

    • The gills have a simple shape and are distributed over much of the body


Oxygen-poor respiratory surfaces, ectotherms or endotherms? Explain.blood

Gill arch

Oxygen-richblood

Lamella

Blood vessel

Gill arch

15%

40%

70%

5%

Water flow

30%

Operculum

100%

60%

90%

O2

Blood flowthrough capillariesin lamellaeshowing % O2

Water flowover lamellaeshowing % O2

Gillfilaments

Figure 42.21

Countercurrent exchange

  • The effectiveness of gas exchange in some gills, including those of fishes

    • Is increased by ventilation and countercurrent flow of blood and water

      • Ram ventilation

      • Appendages that “paddle” water past the gills


Advantages disadvantages to air as the respiratory medium
Advantages & Disadvantages to Air as the Respiratory Medium respiratory surfaces, ectotherms or endotherms? Explain.

Advantages of air

Disadvantages of air

Respiratory surfaces must be large and MOIST

Air dries things out

  • Higher concentration of dissolved oxygen

  • Oxygen and carbon dioxide diffuse much faster in air than water, so respiratory surfaces have to be ventilated much less vigorously in air than water

    • When ventilation does occur in terrestrial animals it requires less energy because air is lighter than water and easier to pump


Tracheal systems in insects

Air sacs respiratory surfaces, ectotherms or endotherms? Explain.

Tracheae

Spiracle

(a) The respiratory system of an insect consists of branched internal tubes that deliver air directly to body cells. Rings of chitin reinforce the largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid (blue-gray). When the animal is active and is using more O2, most of the fluid is withdrawn into the body. This increases the surface area of air in contact with cells.

Figure 42.22a

Tracheal Systems in Insects

  • The tracheal system of insects

    • Consists of tiny branching tubes that penetrate the body


Body respiratory surfaces, ectotherms or endotherms? Explain.cell

Airsac

Tracheole

Body wall

Myofibrils

Trachea

Air

Tracheoles

Mitochondria

(b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole.

Figure 42.22b

2.5 µm

  • The tracheal tubes

    • Supply O2 directly to body cells


With virtually all body cells within a very short distance of respiratory medium, the open circulatory system of insects is not involved in transporting O2 and CO2

For small insects, diffusion through the trachea brings in enough oxygen and removes enough carbon dioxide to support cellular respiration

Larger insects with higher energy demands ventilate their tracheal systems with rhythmic body movements that compress and expand the air tubes like bellows


Lungs
Lungs of respiratory medium, the open circulatory system of insects is not involved in transporting O

Unlike the branching tracheal system of insects, lungs are confined to 1 location

Because the respiratory surface of a lung is not in direct contact with all other body cells, the gap must be bridged by the circulatory system


Evolution of lungs
Evolution of Lungs of respiratory medium, the open circulatory system of insects is not involved in transporting O

  • Lungs have evolved in spiders, terrestrial snails, and most vertebrates

  • Amphibians have small poorly developed lungs due to the gas exchange in their skin

    • Some have no lungs at all

  • All mammals rely entirely on lungs

  • Exceptions

    • Turtles supplement lung breathing with gas exchange in the mouth and anus pew

    • lungfish, fish with lungs to live for short periods of time outside of water or in oxygen poor water


Mammalian respiratory systems a closer look

Branch of respiratory medium, the open circulatory system of insects is not involved in transporting Ofrom thepulmonaryartery(oxygen-poor blood)

Branch from the pulmonary vein (oxygen-rich blood)

Terminal bronchiole

Nasalcavity

Alveoli

Pharynx

Left lung

Esophagus

Larynx

50 µm

Trachea

50 µm

Right lung

Bronchus

Bronchiole

Colorized SEM

SEM

Diaphragm

Heart

Figure 42.23

Mammalian Respiratory Systems: A Closer Look

  • A system of branching ducts

    • Conveys air to the lungs

http://bio-animations.blogspot.com/2008/04/human-body-circulatory-system.html


Mammalian respiratory systems a closer look1
Mammalian Respiratory Systems: A Closer Look of respiratory medium, the open circulatory system of insects is not involved in transporting O

  • Air enters the nostrils, is filtered by hairs, warmed, humidified, and sampled for odors

  • The nasal cavity leads to the pharynx, this is where paths for air and food cross

    • When food is swallowed, the larynx (the upper part of the respiratory tract) moves upward and tips the epiglottis over the glottis (the opening to the wind pipe) allowing food to enter the esophagus into the stomach


Larynx
Larynx of respiratory medium, the open circulatory system of insects is not involved in transporting O

The larynx wall is reinforced with cartilage and in most mammals is adapted as a voice box

Inhaled air rushes past vocal chords in the larynx

Sounds are produced when voluntary muscles in the voice box are tensed stretching the chords so they vibrate


  • In mammals, air inhaled through the nostrils of respiratory medium, the open circulatory system of insects is not involved in transporting O

    • Passes through the pharynx into

      • the trachea: windpipe  trachea forks into 

      • 2 bronchi: one leading to each lung

      • Bronchioles: within the lung, the bronchi branches repeatedly into bronchioles 

      • and dead-end alveoli, where gas exchange occurs


How an amphibian breathes
How an Amphibian Breathes of respiratory medium, the open circulatory system of insects is not involved in transporting O

  • An amphibian such as a frog

    • Ventilates its lungs by positive pressure breathing

    • During a breathing cycle muscles lower the floor of the oral cavity drawing in air through the nostrils

    • With nostrils and mouth closed the floor of the oral cavity rises which forces air down the trachea


How a mammal breathes

Rib cage of respiratory medium, the open circulatory system of insects is not involved in transporting Oexpands asrib muscles contract

Rib cage gets smaller asrib muscles relax

Air inhaled

Air exhaled

Lung

Diaphragm

INHALATIONDiaphragm contracts(moves down)

EXHALATIONDiaphragm relaxes(moves up)

Figure 42.24

How a Mammal Breathes

  • Mammals ventilate their lungs

    • By negative pressure breathing, which pulls air into the lungs

    • Pulls air in instead of pushing it in

    • http://bcs.whfreeman.com/thelifewire/content/chp48/4802s.swf


How a mammal breathes1
How a Mammal Breathes of respiratory medium, the open circulatory system of insects is not involved in transporting O

  • Muscles in the ribcage and diaphragm contract changing the volume of the chest cavity, and the lungs match these volume changes

  • Lungs are surrounded by a double walled sac with each wall separated by a thin layer of fluid

    • The inner layer adheres to the lungs

    • The outer layer adheres to the wall of the chest cavity

    • The layers can slide past each other but cant easily be pulled apart


Mammalian breathing
Mammalian Breathing of respiratory medium, the open circulatory system of insects is not involved in transporting O

  • Tidal Volume: the volume of air a mammal inhales and exhales with each breath

    • Averages about 500mL with each breath

  • Vital capacity: maximum tidal volume during forced ventilation

    • About 3.4 & 4.8L for college females and males respectively

  • Residual volume: the volume of air that remains in the lungs even after a forced exhale (our system doesn’t completely renew the air with every exhalation)


How a bird breathes

Air of respiratory medium, the open circulatory system of insects is not involved in transporting O

Air

Anteriorair sacs

Trachea

Lungs

Posteriorair sacs

Lungs

Air tubes(parabronchi)in lung

1 mm

EXHALATIONAir sacs empty; lungs fill

INHALATIONAir sacs fill

Figure 42.25

How a Bird Breathes

  • Besides lungs, bird have eight or nine air sacs

    • That function as bellows that keep air flowing through the lungs

    • http://bcs.whfreeman.com/thelifewire/content/chp48/4802001.html


The entire system of lungs and air sacs is ventilated when a bird breathes
The entire system of lungs and air sacs is ventilated when a bird breathes

  • Air passes through the lungs in one direction only regardless of whether they’re inhaling or exhaling

  • Instead of alveoli (dead-ends) the site of gas exchange in bird lungs are tiny channels called parabronchi through which air flows in only 1 direction

  • Every exhalation

    • Completely renews the air in the lungs


Control of breathing in humans
Control of Breathing in Humans bird breathes

  • Most of the time breathing is regulated via automatic mechanisms

  • The main breathing control centers are located in two regions of the brain,

    • Medulla oblongata: sets basic breathing rhythm

    • Pons: control center

    • Secondary control is exerted via sensors in the aortic and carotid arteries which monitor O2 and CO2 concentrations, as well as pH


Medulla oblongata
Medulla Oblongata bird breathes

  • Sets breathing rhythm in response to changes of pH in tissue fluid(cerebrospinal fluid) bathing the brain

  • pH of cerebrospinal fluid is determined mainly by concentartion of CO2

  • CO2 diffuses from blood  CF where it reacts with water to form carbonic acid which lowers pH

  • This triggers the medulla oblingata to increase the rate and depth of breathing to eliminate excess CO2 which in turn brings the pH back up restoring homeostasis


Control of breathing in humans1

Cerebrospinal bird breathesfluid

The medulla’s control center

also helps regulate blood CO2 level.

Sensorsin the medulla detect changes

in the pH (reflecting CO2 concentration)

of the blood and cerebrospinal fluid

bathing the surface of the brain.

1

The control center in the

medulla sets the basicrhythm, and a control centerin the pons moderates it,smoothing out thetransitions between

inhalations and exhalations.

5

Nerve impulses relay changes in CO2 and O2 concentrations. Other sensors in the walls of the aortaand carotid arteries in the neck detect changes in blood pH andsend nerve impulses to the medulla. In response, the medulla’s breathingcontrol center alters the rate anddepth of breathing, increasing bothto dispose of excess CO2 or decreasingboth if CO2 levels are depressed.

Pons

Breathing control centers

Nerve impulses trigger muscle contraction. Nervesfrom a breathing control centerin the medulla oblongata of the brain send impulses to thediaphragm and rib muscles, stimulating them to contractand causing inhalation.

2

Medullaoblongata

Carotidarteries

Aorta

In a person at rest, these nerve impulses result in about 10 to 14 inhalationsper minute. Between inhalations, the musclesrelax and the person exhales.

3

The sensors in the aorta andcarotid arteries also detect changesin O2 levels in the blood and signal the medulla to increase the breathing rate when levels become very low.

6

Figure 42.26

Diaphragm

Rib muscles

Control of Breathing in humans

4


  • The centers in the medulla bird breathes

    • Regulate the rate and depth of breathing in response to pH changes in the cerebrospinal fluid

  • The medulla adjusts breathing rate and depth

    • To match metabolic demands


The role of partial pressure gradients
The Role of Partial Pressure Gradients bird breathes

  • Gases diffuse down pressure gradients

    • In the lungs and other organs

  • Diffusion of a gas

    • Depends on differences in a quantity called partial pressure


Partial pressure of
Partial Pressure of bird breathes

  • at sea level, the atmosphere exerts a total pressure of 760mmHg

  • This is a downward force equal to that exerted by a column of mercury 760mmHg high

  • Since the atmosphere is 21% oxygen by volume, the partial pressure of oxygen is

    PO2 = 0.21X 760 = 160mmHg

    PCO2 = 0.23mmHg


Partial pressure
Partial Pressure bird breathes

  • A gas always diffuses from a region of higher partial pressure to a region of lower partial pressure

    • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter25/animation__gas_exchange_during_respiration.html

    • http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter23/animation__changes_in_the_partial_pressures_of_oxygen_and_carbon_dioxide.html


Respiratory pigments
Respiratory Pigments bird breathes

  • Respiratory pigments

    • Are proteins that transport oxygen

    • Greatly increase the amount of oxygen that blood can carry

  • The respiratory pigment of almost all vertebrates is the protein hemoglobin, contained in the erythrocytes

    • Hemocyanin is a respiratory protein used in arthropods


Heme group bird breathes

Iron atom

O2 loaded

in lungs

O2

O2 unloaded

In tissues

O2

Polypeptide chain

  • Like all respiratory pigments

    • Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body

Figure 42.28


Hemoglobin
Hemoglobin bird breathes

Consists of 4 subunits each with a cofactor called a heme group that has an iron atom at its center

The iron binds the oxygen, thus each molecule of hemoglobin can carry four molecules of oxygen

A typical RBC has 250 million molecules of hemoglobin


Hemoglobin1
Hemoglobin bird breathes

The process of loading and unloading oxygen depends on cooperativity of the 4 subunits that make up hemoglobin

Binding of oxygen to 1 subunit induces the others to change shape slightly resulting in higher affinity for oxygen

When 1 subunit unloads oxygen the others quickly revert back to original shape lowering their affinity for oxygen


Review what factors affect protein structure function
Review: What factors affect protein structure/function? bird breathes

As with all proteins hemoglobins conformation is sensitive to a variety of factors including pH

Bohr Shift: when a drop in pH lowers the affinity of hemoglobin for oxygen

Because CO2 reacts with H2O to form carbonic acid (H2CO3) an active tissue lowers the pH of its surroundings and induces hemoglobin to release more O2


Carbon dioxide transport
Carbon Dioxide Transport bird breathes

  • In addition to transporting oxygen, hemoglobin also transports CO2 and assists in buffering

    • Preventing harmful changes in blood pH

      • Only 7% of CO2 released by respiring cells in transported dissolved in solution

      • 23% binds amino groups of hemoglobin

      • 70% is transported in the form of the bicarbonate ion HCO3-


Co 2 diffuses into the blood plasma and then into erythrocytes
CO bird breathes2 Diffuses into the blood plasma and then into erythrocytes

  • It 1st reacts with water assisted by the enzyme carbonic anhydrase

  • To form H2CO3 which then dissociates a H+ ion and HCO3-

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

  • The HCO3- diffuses into the plasma

  • As blood flows through the lungs the process is rapidly reversed as diffusion of CO2 out of the blood shifts the chemical equilibrium in favor of HCO3- CO2 which is ultimately released


Diving mammals
Diving Mammals bird breathes

  • Diving mammals have many adaptations for their way of life.

  • Deep-diving air breathers

    • Stockpile O2 and deplete it slowly

    • Lower heartrate and breathing during dives

    • Store O2 not only with hemoglobin, but also myoglobin in the blood and muscle


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