Copyright © 2003 a TBM production. All rights and lefts reserved Respiration: The Exchange of Gases Respiratory System

Copyright © 2003 a TBM production. All rights and lefts reserved

Respiration: The Exchange of Gases

Respiratory System


• In humans, air enters through the nasal cavity

– It passes through the pharynx and larynx into the trachea

– The trachea forks to form two bronchi

– Each bronchus branches into numerous bronchioles

– Alveoli is the terminus of the bronchioles

Humans and land vertebrates have lungs


• The human respiratory system

Figure 22.6A

Nasalcavity

Left lung

Pharynx(Esophagus)

Larynx

Trachea

Bronchus

Bronchiole

Diaphragm

(Heart)

Rightlung


Chest Cavity • A. Larynx

– Voice box

• B. Trachea

– First tube in air passage

– Lined with cilia and mucous cells

– Cartilage rings keep it from collapsing

• C. Bronchi

– Tube branching from trachea

• D. Secondary Bronchioles

– Branches leading to the alveoli

A

C

D

E

FG

HB

Nasal Cavity: warms, cleans and humidifies air

Epiglottis: flap to keep food from entering the trachea


Chest Cavity • E. Terminal Bronchi

and Alveoli

– Smallest division of bronchi

– Where air exchange takes place

• F: Visceral membrane

– Surround the lung

• G. Interstitial or pleural space

– Fluid to prevent friction between visceral and parietal

• H. Parietal membrane

– Lines the chest wall

A

C

D

E

FG

HB


Chest Cavity • I Clavicle

– Supports the ribs

• J. Superior lobe

• K. Mediastinum

– Cavity for the heart

• L. Inferior lobe

• M Pleural space (same as G)

• N Diaphragm

– Contracts down to inhale

– Relax to exhale

I

K

L

MN

J


• The bronchioles end in clusters of tiny sacs called alveoli– Alveoli form the respiratory

surface of the lungs

– Oxygen diffuses through the thin walls of the alveoli into the blood

Figure 22.6C

Figure 22.6B

Oxygen-richblood Oxygen-poor

blood

Alveoli

Blood capillaries

Bronchiole


Alveoli A

B C

D

E

A. Respiratory Bronchiole

B. Alveolar Chamber

C. Alveolar Epithelium

D. Red blood Cells

E. Capillary Epithelium


Alveoli A

B C

D

E

A. Respiratory Bronchiole

Last tube of air passage

B. Alveolar Chamber

inside where O2 diffuses out and CO2 in

C. Alveolar Epithelium

D. Red blood Cells

erythrocytes

E. Capillary Epithelium

the capillary


Order of O2 flow

• Nasal Cavity

• Pharynx

• Larynx

• Trachea

• Bronchi

• Bronchiole

• Alveoli


Diffusion of O2 and CO2

• Gasses must diffuse through 3 membranes

– Alveolar Epithelium

– Capillary Epithelium

– Red blood cell epithelium


• Breathing is the alternation of inhalation and exhalation

22.8 Breathing ventilates the lungs

Figure 22.8A

Rib cageexpands asrib musclescontract

Airinhaled

Lung

Diaphragm

INHALATIONDiaphragm contracts

(moves down)

EXHALATIONDiaphragm relaxes

(moves up)

Rib cagegets smalleras rib musclesrelax

Airexhaled


• Vital capacity is the maximum volume of air we can inhale and exhale

– But our lungs hold more than this amount

– The alveoli do not completely collapse

– A residual volume of “dead” air remains in the lungs after exhalation


• Breathing control centers are located in the pons and medulla of the brain

– These automatic controls keep breathing in tune with body needs

22.9 Breathing is automatically controlled


• During exercise, the CO2 level in the blood rises, lowering the blood pH

– Medulla causes lungs and ribs to breathe

– Low O2

– Pons cause us to breathe

Figure 22.9

Brain

Cerebrospinal fluid

BREATHING CONTROLCENTERS—stimulated by:

CO2 increase / pH decreasein blood

Nerve signalindicating lowO2 level

O2 sensorin artery

Pons

Medulla

Nerve signalstriggercontractionof muscles

Diaphragm

Rib muscles


• The heart pumps oxygen-poor blood to the lungs

– In the lungs it picks up O2 and drops off CO2

– In the tissues, cells pick up O2 and drop off CO2

– Gasses move by diffusion across membranes

• Alveolar membrane

• Capillary membrane

• RBC membrane

Ch 13 Blood transports the respiratory gases, with hemoglobin carrying the oxygen

TRANSPORT OF GASES IN THE BODY


• Gas exchange in the body

• 21% O2 in blood

• 16% O2 in body cells

• O2 diffuses into cell


• Hemoglobin is a protein in red blood cells– It carries most of the oxygen in the blood

– Oxyhemoglobin formed

Hemegroup

Ironatom

Polypeptide chain

O2 loadedin lungs

O2 unloadedin tissues

O2

O2


• Gas exchange in the body

• .04% CO2 in blood

• 3% CO2 in body cells

• CO2 diffuses out of cells into the blood


• Most CO2 in the blood combines with water to form carbonic acid– The carbonic acid

breaks down to form H+ ions and bicarbonate ions

– These help buffer the blood

– Enzymes in RBC cause the change

TISSUE CELL

CO2 produced

INTERSTITIALFLUID

CO2

CO2

CO2

BLOODPLASMAWITHINCAPILLARY

Capillarywall

H2O

H2CO3

Carbonic acid

REDBLOODCELL

HCO3– + H+

Hemoglobinpicks upCO2 and H+

Bicarbonate

HCO3–


• Most CO2 , 70% ,is transported to the lungs in the form of bicarbonate ions

• 23% by binding to amino acids in hemoglobin

• 7% dissolved in plasma

• Enzymes cause shift back to CO2

ALVEOLAR SPACE IN LUNG

CO2

CO2

H2O

H2CO3

HCO3– + H+

HemoglobinreleasesCO2 and H+

HCO3–

CO2

CO2


Cellular Respiration

• Food is Carbon based (ex. C6H12O6)

• When food is burned, CO2 is produced, leaving excess H+

• H combines with inhale O2 to form H2O

• If there is no O2, H+ builds up, body becomes acidic

• Low acidity (= High H +) is fatal


• A human fetus depends on the placenta for gas exchange

• Oxygenated blood enters the umbilical VEIN

• Mom’s blood and babies don’t mix

Connection: The human fetus exchanges gases with the mother’s bloodstream

Placenta, containingmaternal blood vesselsand fetal capillaries

Umbilical cord,containing fetalblood vessels

Amnioticfluid

Uterus


• A network of capillaries exchanges O2 and CO2 with maternal blood that carries gases to and from the mother’s lungs

• At birth, increasing CO2 in the fetal blood stimulates the fetus’s breathing control centers to initiate breathing


Surfactant

• Fatty molecule surrounding alveoli

• Lowers surface tension of water around alveoli

• Prevents the alveoli from collapsing with each exhalation

• Premature babies: before 28 weeks

– Not enough surfactant

– Baby has trouble breathing

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Copyright © 2003 a TBM production. All rights and lefts reserved Respiration: The Exchange of Gases Respiratory System