Respiration

Chapter 39

Impacts, Issues

Up in Smoke

Smoking immobilizes ciliated cells and kills white

blood cells that defend the respiratory system;

highly addictive nicotine discourages quitting

39.1 The Nature of Respiration

All animals must supply their cells with oxygen

and rid their body of carbon dioxide

Respiration

• The physiological process by which an animal

exchanges oxygen and carbon dioxide with its

environment

Interactions with Other Organ Systems

Partial Pressure

Partial pressure

• Of the total atmospheric pressure measured by a

mercury barometer (760 mm Hg), O2 contributes

21% (160 mm Hg)

The Basis of Gas Exchange

Respiration depends on diffusion of gaseous

oxygen (O2) and carbon dioxide (CO2) down

their concentration gradients

Gases enter and leave the internal environment

across a thin, moist layer (respiratory surface)

that dissolves the gases

Factors Affecting Diffusion Rates

Factors that increase diffusion of gases across a

respiratory surface:

• High partial pressure gradient of a gas across the

respiratory surface

• High surface-to-volume ratio

• High ventilation rate (movement of air or water

across the respiratory surface)

Respiratory Proteins

Respiratory proteins contain one or more

metal ions that reversibly bind to oxygen atoms

• Hemoglobin: An iron-containing respiratory

protein found in vertebrate red blood cells

• Myoglobin: A respiratory protein found in

muscles of vertebrates and some invertebrates

39.2 Gasping for Oxygen

Rising water temperatures, slowing streams, and

organic pollutants reduce the dissolved oxygen

(DO) available for aquatic species

39.1-39.2 Key Concepts

Principles of Gas Exchange

Respiration is the sum of processes that move

oxygen from air or water in the environment to

all metabolically active tissues and move carbon

dioxide from those tissues to the outside

Oxygen levels are more stable in air than in

water

39.3 Invertebrate Respiration

Integumentary exchange

• Some invertebrates that live in aquatic or damp

environments have no respiratory organs; gases

diffuse across the skin

Gills

• Filamentous respiratory organs that increase

surface area for gas exchange in water

Invertebrate Respiration

Lungs

• Saclike respiratory organs with branching tubes

that deliver air to a respiratory surface

Snails and slugs that spend some time on land

have a lung instead of, or in addition to, gills

Snails with Lungs

Invertebrate Respiration

Tracheal system

• Insects and spiders with a hard integument have

branching tracheal tubes that open to the surface

through spiracles (no respiratory protein required)

Book lungs

• Some spiders also have thin sheets of respiratory

tissue that exchange oxygen with a respiratory

pigment (hemocyanin) in blood

Insect Tracheal System

A Spider’s Book Lung

39.3 Key Concepts

Gas Exchange in Invertebrates

Gas exchange occurs across the body surface

or gills of aquatic invertebrates

In large invertebrates on land, it occurs across a

moist, internal respiratory surface or at fluid-filled

tips of branching tubes that extend from the

surface to internal tissues

39.4 Vertebrate Respiration

Fishes use gills to extract oxygen from water

• Countercurrent flow aids exchange (blood flows

through gills in opposite direction of water flow)

Amphibians exchange gases across their skin,

and at respiratory surfaces of paired lungs

• Larvae have external gills

Fish Gills

Countercurrent Flow

Frog Respiration

Vertebrate Respiration

Reptiles, birds and mammals exchange gases

through paired lungs, ventilated by chest muscles

Birds have the most efficient vertebrate lungs

• Air sacs allow oxygen-rich air to pass respiratory

surfaces on both inhalation and exhalation

Bird Respiratory System

Fig. 39-12 (inset), p. 687

39.5 Human Respiratory System

The human respiratory system functions in gas

exchange, sense of smell, voice production,

body defenses, acid-base balance, and

temperature regulation

Airways

Air enters through nose or mouth, flows through

the pharynx (throat) and the larynx (voice box)

• Vocal cords change the size of the glottis

The epiglottis protects the trachea, which

branches into two bronchi, one to each lung

• Cilia and mucus-secreting cells clean airways

Larynx: Vocal Cords and Glottis

From Airways to Alveoli

Inside each lung, bronchi branch into

bronchioles that deliver air to alveoli

Alveoli are small sacs, one cell thick, where

gases are exchanged with pulmonary capillaries

Muscles and Respiration

Muscle movements change the volume of the

thoracic cavity during breathing

Diaphragm

• A broad sheet of smooth muscle below the lungs

• Separates the thoracic and abdominal cavities

Intercostal muscles

• Skeletal muscles between the ribs

Functions of the Respiratory System

39.6 Cyclic Reversals

in Air Pressure Gradients

Respiratory cycle

• One inhalation and one exhalation

Inhalation is always active

• Contraction of diaphragm and external intercostal

muscles increases volume of thoracic cavity

• Air pressure in alveoli drops below atmospheric

pressure; air moves inward

Cyclic Reversals

in Air Pressure Gradients

Exhalation is usually passive

• As muscles relax, the thoracic cavity shrinks

• Air pressure in the alveoli rises above

atmospheric pressure, air moves out

Exhalation may be active

• Contraction of abdominal muscles forces air out

The Thoracic Cavity and

the Respiratory Cycle

First Aid for Choking

Heimlich maneuver

• Upward-directed force on the diaphragm forces

air out of lungs to dislodge an obstruction

Respiratory Volumes

Air in lungs is partially replaced with each breath

• Lungs are never emptied of air (residual volume)

Vital capacity

• Maximum volume of air the lungs can exchange

Tidal volume

• Volume of air that moves in and out during a

normal respiratory cycle

Respiratory Volumes

Control of Breathing

Neurons in the medulla oblongata of the brain

stem are the control center for respiration

• Rhythmic signals from the brain cause muscle

contractions that cause air to flow into the lungs

Chemoreceptors in the medulla, carotid arteries,

and aorta wall detect chemical changes in blood,

and adjust breathing patterns

Respiratory Responses

39.7 Gas Exchange and Transport

Gases diffuse between a pulmonary capillary

and an alveolus at the respiratory membrane

• Alveolar epithelium

• Capillary endothelium

• Fused basement membranes

O2 and CO2 each follow their partial pressure

gradient across the membrane

The Respiratory Membrane

Oxygen Transport

In alveoli, partial pressure of O2 is high; oxygen

binds with hemoglobin in red blood cells to form

oxyhemoglobin (HbO2)

In metabolically active tissues, partial pressure

of O2 is low; HbO2 releases oxygen

Myoglobin, found in some muscle tissues, is

similar to hemoglobin but holds O2 more tightly

Hemoglobin and Myoglobin

Carbon Dioxide Transport

Carbon dioxide is transported from metabolically

active tissues to the lungs in three forms

• 10% dissolved in plasma

• 30% carbaminohemoglobin (HbCO2)

• 60% bicarbonate (HCO3-)

Carbonic anhydrase in red blood cells

catalyzes the formation of bicarbonate

CO2 + H2O → H2CO3 → HCO3

- + H+

Partial Pressures for

Oxygen and Carbon Dioxide

The Carbon Monoxide Threat

Carbon monoxide (CO)

• A colorless, odorless gas that can fill up O2

binding sites on hemoglobin, block O2 transport,

and cause carbon monoxide poisoning

Carbon monoxide poisoning often results when

fuel-burning appliance are poorly ventilated

• Symptoms include nausea, headache, confusion,

dizziness, and weakness

39.4-39.7 Key Concepts

Gas Exchange in Vertebrates

Gills or paired lungs are gas exchange organs in

most vertebrates

The efficiency of gas exchange is improved by

mechanisms that cause blood and water to flow

in opposite directions at gills, and by muscle

contractions that move air into and out of lungs

39.8 Respiratory Diseases and Disorders

Interrupted breathing

• Brain-stem damage, sleep apnea, SIDS

Potentially deadly infections

• Tuberculosis, pneumonia

Chronic bronchitis and emphysema

• Damage to ciliated lining of bronchioles and walls

of alveoli; tobacco smoke is the main risk factor

Cigarette Smoke and Ciliated Epithelium

Risks Associated With Smoking

and Emphysema

39.8 Key Concepts

Respiratory Problems

Respiration can be disrupted by damage to

respiratory centers in the brain, physical

obstructions, infectious disease, and inhalation

of pollutants, including cigarette smoke

39.9 High Climbers and Deep Divers

Altitude sickness

• Hypoxia can result when people who live at low

altitudes move suddenly to high altitudes

• People who grow up at high altitudes have more

alveoli and blood vessels in their lungs

Acclimatization to altitude includes adjustments

in cardiac output, rate and volume of breathing

• Hypoxia stimulates erythropoietin secretion

Adaptation to High Altitude

Llamas that live at high altitudes have special

hemoglobin that binds oxygen more efficiently

Deep-Sea Divers

Water pressure increases with depth; human

divers using compressed air risk nitrogen

narcosis (disrupts neuron signaling)

Returning too quickly to the surface from a deep

dive can release dangerous nitrogen bubbles

into the blood stream (‘the bends”)

Without tanks, trained humans can dive to 210

meters; sperm whales can dive 2,200 meters

Adaptations for Deep Diving

Leatherback turtles dive up to one hour

• Move air to cartilage-reinforced airways

• Flexible shell for compression

Four ways diving animals conserve oxygen

• Deep breathing before diving

• High red-cell count, large amounts of myoglobin

• Slowed heart rate and metabolism

• Conservation of energy

Deep Divers

39.9 Key Concepts

Gas Exchange in Extreme Environments

At high altitudes, the human body makes short-

term and long-term adjustments to thinner air

Built-in respiratory mechanisms and specialized

behaviors allow sea turtles and diving marine

mammals to stay under water, at great depths,

for long periods