copyright © 2005 pearson education, inc. publishing as benjamin cummings ch.37 respiration

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Ch.37 Respiration


Essential knowledge 4.B.2:

• Cooperative interactions within organisms promote efficiency in the use of energy and matter.

– a. Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole.


Essential knowledge 4.A.4:

• Organisms exhibit complex properties due to interactions between their constituent parts.

– a. Interactions and coordination between organs provide essential biological activities.

– b. Interactions and coordination between systems provide essential biological activities.


Essential knowledge 2.D.2:

• Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.

• a. Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions.

• b. Organisms have various mechanisms for obtaining nutrients and eliminating wastes.

• c. Homeostatic control systems in species of microbes, plants and animals support common ancestry.


Essential knowledge 2.A.3:

• Organisms must exchange matter with the environment to grow, reproduce and maintain organization.

– a. Molecules and atoms from the environment are necessary to build new molecules.

– b. Surface area-to-volume ratios affect a biological system’s ability to obtain necessary resources or eliminate waste products.


Ch.37 Gas Exchange

• Respiration involves three events

–

– External respiration - gas exchange occurs between air and blood (O2 from air to blood; CO2 from blood into air) within the lungs and oxygen is carried to other parts of the body by circulatory system

– Internal respiration - gas exchange occurs between blood and tissue fluid (O2 from blood to tissue fluid; CO2 from tissue fluid into blood). Bodies’ cells exchange gases (O2 taken in; CO2 released) with tissue fluid. Blood carries carbon dioxide from cell to lungs


• Gas exchange occurs across specialized respiratory surfaces

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


• Animals require large, thin, moist respiratory surfaces for the adequate diffusion of respiratory gases between their cells and the respiratory medium, either air or water

•

• (1)This means that respiratory surfaces must be kept moist for oxygen and carbon dioxide to diffuse through the cell’s plasma membrane


• (2)Respiratory surfaces must be extensive enough (large surface area) to take up enough oxygen and get rid of carbon dioxide for the entire body

•

• (3)These delicate moist tissues of respiratory surfaces need to be protected


Gas Exchange

• Hydras and planarians

– Small animals with large surface area

– Most of their cells exchange gases directly with the environment

–


Types of respiratory systems

• Skin

• Gills

• Tracheal system

• Lungs


Skin

• Skin - animals such as earthworms have no specialized gas exchange surfaces

• Oxygen diffuses into capillaries beneath the skin

• They must live in damp places or in water to keep respiratory surfaces moist

•


Gills in Aquatic Animals

• Gills are featherlike outfoldings (evaginations) of the outer or inner body surface specialized for gas exchange, and occur in aquatic animals

•

• Gills have finely subdivided surfaces to provide adequate surface area and contain a rich blood supply for transport (vascularization)


• The feathery gills projecting from a salmon

– Are an example of a specialized exchange system found in animals


• In some invertebrates

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


• Many segmented worms have flaplike gills

– That extend from each segment of their body


• The gills of clams, crayfish, and many other animals

– Are restricted to a local body region


• Oxygen makes up 0.45% of seawater, but 21% of air

• This means that aquatic animals have a greater problem obtaining enough oxygen than do terrestrial animals and expend much more energy doing so (25% compared to1-2% of their energy)

• Diffusion is also 1000X slower in water than in air (water is 1000X more dense than air)

•


• The effectiveness of gas exchange in some gills, including those of fishes is increased by ventilation and countercurrent flow of blood and water


Counter-current exchange

•

• This maintains a favorable gradient between blood and the water at every point of exchange, this maximizes the amount of oxygen the blood removes from the water


Respiratory systems

• Land animals have two advantages: air contains more oxygen than an equal volume of water and air is lighter and easier to move.

• Terrestrial animals expend much less energy than an aquatic animal in gas exchange

•


• Most terrestrial animals have respiratory surfaces that are infoldings (invaginations) of the body surface

• This protects the respiratory surface and keeps it moist

•


Land Environments: Tracheae

• Insects and other terrestrial arthropods

– A respiratory system consists of branched tracheae

–

– Tracheae branch until end in tracheoles (surface area) that are in direct contact with body cells so they do not require circulatory system to transport gases


• The tracheal tubes supply O2 directly to body cells and are filled with fluid for gas exchange


Lungs

• Spiders, land snails, and most terrestrial vertebrates have internal lungs

• Lungs are invaginated

• Lungs are restricted to one part of the body, so a circulatory system is needed to transport gases from lungs to the rest of the body

•


Land Environments: Lungs of Vertebrates

• Terrestrial vertebrates have evolved lungs

–Lungs of amphibians

• Possess a short tracheae which divides into two bronchi that open into lungs

• Many also breathe to some extent through skin

–Reptiles

• Inner lining of lungs is more finely divided in reptiles than in amphibians

–Lungs of birds and mammals are elaborately subdivided

• All terrestrial vertebrates, except birds, use a tidal ventilation system

–


How an Amphibian Breathes

• An amphibian such as a frog

– Ventilates its lungs by positive pressure breathing, which forces air down the trachea


How a Mammal Breathes

• Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs


Ventilation in Terrestrial Vertebrates

• Inspiration (inhalation) in mammals

• Create negative pressure in lungs

–The rib cage is elevated (rib muscles contract)

–The diaphragm lowers (contracts)

–Thoracic pressure decreases (volume increases) to less than atmospheric pressure

–


Ventilation in Terrestrial Vertebrates

• Expiration (exhalation) in mammals

• Create positive pressure in lungs

– The rib cage is lowered

– The diaphragm rises

– Thoracic pressure increases,(thoracic cavity volume decreases) to more than atmospheric pressure

–


How a Bird Breathes

• Besides lungs, bird have eight or nine air sacs

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


•

• Every exhalation completely renews the air in the lungs

• Lungs do not have alveoli, but contain tiny parallel tubes called parabronchi

• Air flows one direction and blood flows in the opposite direction acting as counter-current exchange


Human Respiratory System

• As air moves through upper respiratory system

– It is filtered to free it of debris

– Warmed, and

– Humidified

• When air reaches lungs

– It is at body temperature, and

–



• Air passes from pharynx through glottis

• Larynx and trachea

– Permanently held open by cartilage rings

– Facilitates movement of air

• When food is swallowed

– The larynx rises, and

– The glottis is closed by the epiglottis

–



• Trachea divides

– Forms two primary bronchi

– Bronchi enter the right and left lungs

• Bronchi branch until there are a great number of tiny bronchioles

– Each bronchiole terminates in an elongated space enclosed by alveoli which greatly increase the surface area of the respiratory surface

• Alveoli are air sacs lined with a thin layer of epithelial cells which form the respiratory surface

•


Ventilation

• Humans breathe using a tidal mechanism

– Volume of thoracic cavity and lungs is increased by muscle contractions that lower the diaphragm and raise the ribs

•


Control of Breathing in Humans

• The main breathing control centers

– Are located in two regions of the brain, the medulla oblongata and the pons


• The centers in the medulla regulate the rate and depth of breathing in response to pH changes (H+) in the blood and cerebrospinal fluid

• The medulla adjusts breathing rate and depth to match metabolic demands

• CO2 reacts with H2O to form carbonic acid, which lowers the pH of the blood

•


• By monitoring pH, the medulla regulates CO2 levels in the blood


• Sensors in the aorta and carotid arteries

– Monitor O2 and CO2 concentrations in the blood

–


Respiratory Pigments

• Respiratory pigments are proteins that transport oxygen and greatly increase the amount of oxygen that blood can carry

• O2 is not very soluble in water, so blood transports very little dissolved O2

•


• Hemoglobin is composed of four polypeptide chains, each polypeptide chain contains a heme group which contains an iron atom.

•


• Like all respiratory pigments

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


Gas Exchange and Transport

• Oxygen diffuses into pulmonary capillaries

– Most combines with hemoglobin in red blood cells to form oxyhemoglobin

• CO2 diffuses out of pulmonary capillaries

– Most carbon dioxide is transported in the form of bicarbonate ion

–


• Loading and unloading of O2

– Depend on cooperation between the subunits of the hemoglobin molecule

–


Carbon Dioxide Transport

• Hemoglobin also helps transport CO2 and assists in buffering the pH of the blood


• Carbon dioxide from respiring cells

– Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs


CO2 transport

• Some CO2 dissolves in the plasma, but most enters the red blood cells

• Some CO2 binds to hemoglobin, but most reacts with H2O to form carbonic acid (H2CO3)

• Carbonic acid forms more easily in RBC’s with the help of the enzyme carbonic anhydrase

• H2CO3 dissociates to become (H+) hydrogen ion and (HCO3

-) bicarbonate ion

•


•

• Bicarbonate ions buffer the blood pH by combining with H+ ions and removing them from the blood, or by releasing H+ ions when needed


Respiration and Health

• Upper Respiratory Tract Infections

– Strep Throat

• Streptococcus pyogenes

– Sinusitis

• Infection of sinuses

– Tonsillitis

• Infection of tonsils

– Laryngitis

• Infection of larynx


Respiration and Health

• Lower Respiratory Tract Infections

– Acute bronchitis

• Infection of primary and secondary bronchi

– Pneumonia

• Viral or bacterial infection of the lungs where bronchi and alveoli fill with fluid

– Pulmonary tuberculosis

•


Disorders

• Pulmonary fibrosis

– Fibrous connective tissue builds up in the lungs

• Chronic bronchitis

– Airways inflamed and filled with mucus

• Emphysema

–


Disorders

• Asthma

– Airways are unusually sensitive to specific irritants

• When exposed to the irritants, the smooth muscles in the bronchioles undergo spasms

• Lung Cancer

–

copyright © 2005 pearson education, inc. publishing as benjamin cummings ch.37 respiration

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