Essential Knowledge: 2.A.3 Organisms must exchange matter with the environment to grow, reproduce, and maintain organization2.D.2 Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.4.A.4 Organisms exhibit complex Properties due to interactions between constituent parts4.B.2 Cooperative interactions within organisms promote efficiency in the use of energy and matter

What is the point of the respiring?◦ Gas exchange provides oxygen for cellular

respiration and gets rid of carbon dioxide. How do gases move from one area to the

next?◦ Gases move down pressure gradients – moving

from regions of high pressure to regions of low pressure

◦ In lungs and tissues, O2 and CO2 move from areas where the pressure is higher to areas where pressure is lower

Obtaining Oxygen

Where can animals get oxygen?◦ From air and water. In a given volume there is

less oxygen in water than in air. So animals who use water as their source of oxygen must be very efficient

What kind of surfaces in animals can be used to obtain oxygen?◦ All surfaces must be moist◦ Surfaces include skin, tracheae, gills or lungs

Obtaining Oxygen

Gill are outfoldings that increase surface area for effiencient gas exchange

Parapodium (functions as gill)

(a) Marine worm

Gills

(b) Crayfish (c) Sea star

Tube foot

Coelom

Gills

What does ventilation mean to you?◦ When talking about the respiratory system,

ventilation means movement of the respiratory medium over the respiratory surface.

How do fish get oxygen?◦ They move through water – to move water over

their gills◦ Oxygen moves from the water to the gills to the

blood

Obtaining Oxygen

What is the name of the system used by fish to get oxygen from gills to the blood?◦ Counter Current Exchange - where blood flows in

the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets

What other systems did we learn about that have a counter current exchange system?◦ Thermoregulation – warm blood from core heating

up cold blood returning from the extremities◦ Excretion – reabsorption of water from nephron to

blood

Obtaining Oxygen

Fig. 42-22

Anatomy of gills

Gillarch

Waterflow Operculum

Gillarch

Gill filamentorganization

Bloodvessels

Oxygen-poor blood

Oxygen-rich blood

Fluid flowthrough

gill filament

Lamella

Blood flow throughcapillaries in lamella

Water flowbetweenlamellae

Countercurrent exchange

PO2 (mm Hg) in water

PO2 (mm Hg) in blood

Net diffu-sion of O2

from waterto blood

150120 90 60 30

11080 20Gill filaments

50140

What is unique about the respiratory system of insects?◦ It consists of a tracheal systems made of tubes

that branch out supply oxygen to the body cells◦ It is separate / independent from the circulatory

system

Obtaining Oxygen

Fig. 42-23

Air sacs

Tracheae

Externalopening

Bodycell

AirsacTracheole

Tracheoles Mitochondria Muscle fiber

2.5 µmBody wall

Trachea

Air

What is unique about the respiratory system of mammals?◦ Mammals have lungs which are infoldings of the

body surface◦ The circulatory systems transports oxygen from

the lungs to the rest of the body◦ A system of branching ducts conveys air to the

lungs◦ Air inhaled through the nostrils passes through

the pharynx via the larynx, trachea, bronchi, bronchioles, and alveoli, where gas exchange occurs

Obtaining Oxygen

Fig. 42-24

Pharynx

Larynx

(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

DiaphragmHeart SEM

Leftlung

Nasalcavity

Terminalbronchiole

Branch ofpulmonaryvein(oxygen-richblood)

Branch ofpulmonaryartery(oxygen-poorblood)

Alveoli

ColorizedSEM50 µm 50 µm

How does oxygen get into the lungs?◦ Mammals ventilate their lungs by negative

pressure breathing, which pulls air into the lungs

◦ Lung volume increases as the rib muscles and diaphragm contract

Obtaining Oxygen

Fig. 42-25

Lung

Diaphragm

Airinhaled

Rib cageexpands asrib musclescontract

Rib cage getssmaller asrib musclesrelax

Airexhaled

EXHALATIONDiaphragm relaxes

(moves up)

INHALATIONDiaphragm contracts

(moves down)

How is breathing controlled in humans?◦ In humans, the main breathing control centers

are in two regions of the brain, the medulla oblongata and the pons.

◦ The medulla regulates 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 pons regulates the tempo◦ Sensors in the aorta and carotid arteries monitor O2

and CO2 concentrations in the blood. These sensors exert secondary control over breathing

Obtaining Oxygen

Fig. 42-27

Breathingcontrolcenters

Cerebrospinalfluid

Pons

Medullaoblongata

Carotidarteries

Aorta

DiaphragmRib muscles

Why does oxygen move from the lungs to the circulatory system?◦ Blood arriving in the lungs has a low partial

pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli

◦ In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air

◦ In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood

Obtaining Oxygen

Fig. 42-28

Alveolus

PO2 = 100 mm Hg

PO2 = 40 PO2

= 100

PO2 = 100PO2

= 40

Circulatorysystem

Body tissue

PO2 ≤ 40 mm Hg PCO2

≥ 46 mm Hg

Body tissue

PCO2 = 46 PCO2

= 40

PCO2 = 40PCO2

= 46

Circulatorysystem

PCO2 = 40 mm Hg

Alveolus

(b) Carbon dioxide(a) Oxygen

How does hemoglobin carry oxygen?◦ A single hemoglobin molecule can carry four

molecules of O2

◦ The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2

◦ CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2; this is called the Bohr shift

Obtaining Oxygen

Fig. 42-UN1

Chains

IronHeme

Chains

Hemoglobin

Fig. 42-29

O2 unloadedto tissuesat rest

O2 unloadedto tissues

during exercise

100

40

0

20

60

80

0 40 80 100

O2 s

atu

rati

on

of

hem

og

lob

in (

%)

20 60

Tissues duringexercise

Tissuesat rest

Lungs

PO2 (mm Hg)

(a) PO2 and hemoglobin dissociation at pH 7.4

O2 s

atu

rati

on

of

hem

og

lob

in (

%)

40

0

20

60

80

0 40 80 10020 60

100

PO2 (mm Hg)

(b) pH and hemoglobin dissociation

pH 7.4

pH 7.2

Hemoglobinretains lessO2 at lower pH

(higher CO2

concentration)

How does the carbon dioxide produced from cellular respiration exit the body?◦ Hemoglobin also helps transport CO2 and assists

in buffering◦ CO2 from respiring cells diffuses into the blood

and is transported either in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO3

–)

◦ CO2 diffuses from the blood in the pulmonary artery (high CO2) to the lung (low CO2) where the partial pressure is less

Getting Rid of Carbon Dioxide

Fig. 42-30Body tissue

CO2 produced

CO2 transportfrom tissues

Capillarywall

Interstitialfluid

Plasmawithin capillary

CO2

CO2

CO2

Redbloodcell

H2O

H2CO3 HbCarbonic acid

Hemoglobinpicks up

CO2 and H+

CO2 transportto lungs

HCO3–

BicarbonateH++

Hemoglobinreleases

CO2 and H+

To lungsHCO3

–

HCO3–

Hb

H++HCO3–

H2CO3

H2O

CO2

CO2

CO2

CO2

Alveolar space in lung

Fig. 42-UN2Inhaled air Exhaled air

Alveolarepithelial cells

Alveolar spaces

CO2 O2

CO 2 O2

Alveolarcapillaries of

lung

Pulmonary veinsPulmonary arteries

Systemic veins Systemic arteries

Heart

SystemiccapillariesCO2 O 2

CO2 O2

Body tissue