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CHAPTER 22 Respiration: The Exchange of Gases

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1 CHAPTER 22 Respiration: The Exchange of Gases

2 MECHANISMS OF GAS EXCHANGE
Gas exchange is the interchange of O2 and CO2 between an organism and its environment It is also called respiration

3 Overview: Gas exchange involves breathing, the transport of gases, and the servicing of tissue cells
Gas exchange is essential because energy metabolism requires O2 and produces CO2 food ATP CO2 O2

4 Animals exchange O2 and CO2 through moist body surfaces
O2 enters an animal and CO2 leaves by diffusion through a respiratory surface Respiratory surfaces are made up of living cells

5 Lungs capillaries (circulatory system) trachea bronchi bronchioles
alveoli alveoli

6 The human respiratory system
In humans and other mammals, 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

7 The human respiratory system
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

8 Connection: Smoking is one of the deadliest assaults on our respiratory system
Mucus and cilia in the respiratory passages protect the lungs Pollutants, including tobacco smoke, can destroy these protections Smoking kills about 430,000 Americans each year

9 Connection: Smoking is one of the deadliest assaults on our respiratory system
Smoking causes lung cancer and contributes to heart disease Smoking also causes emphysema Cigarette smoke makes alveoli brittle, causing them to rupture This reduces the lungs’ capacity for gas exchange

10 Breathing ventilates the lungs
Breathing is the alternation of inhalation (active) and exhalation (passive)

11 Negative pressure breathing
Diaphragm moves down & expands chest cavity pulls air into lungs inhale exhale

12 Automatic Brain Control
You don’t have to think to breathe! medulla & pons measure blood pH CO2 = pH (acid) coordinate breathing, heart rate & body’s need for energy Medulla oblongata will stimulate diaphragm to contract.

13 TRANSPORT OF GASES IN THE BODY
Blood transports the respiratory gases, with hemoglobin carrying the oxygen The heart pumps oxygen-poor blood to the lungs In the lungs it picks up O2 and drops off CO2(external respiration) In the tissues, cells pick up CO2 and drop off O2-(Internal respiration) Gases diffuse down pressure gradients in the lungs and the tissues

14 Gas exchange: Diffusion of gases
Gases move by diffusion from high to low concentration capillaries are thin-walled tubes of circulatory system alveoli are thin-walled sacs of respiratory system capillaries in lungs capillaries in muscle O2 O2 O2 O2 CO2 CO2 CO2 CO2 blood lungs blood body

15 Gas exchange in the body

16 Hemoglobin is a protein in red blood cells
It carries most of the oxygen in the blood Heme group Iron atom O2 loaded in lungs O2 O2 unloaded in tissues O2 Polypeptide chain

17 Hemoglobin helps transport CO2 and buffer the blood
Hemoglobin helps buffer the pH of blood and carries some CO2 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

18 Transport of CO2 Most CO2 is transported to the lungs in the form of bicarbonate ions

19 Connection: The human fetus exchanges gases with the mother’s bloodstream
A human fetus depends on the placenta for gas exchange 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 Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus

20 Breathing and Homeostasis
ATP Homeostasis keeping the internal environment of the body balanced need to balance O2 in and CO2 out need to balance energy (ATP) production Exercise breathe faster need more ATP bring in more O2 & remove more CO2 Disease poor lung or heart function = breathe faster need to work harder to bring in O2 & remove CO2 CO2 O2

21 Disorders of the Respiratory system
Asthma: a severe allergic reaction in which contraction of the bronchioles makes breathing difficult Bronchitis: an inflammation of the lining of the bronchial tubes. The passageways to the alveoli become swollen and clogged with mucus Emphysema: lungs lose their elasticity, deterioration of the lung structure Pneumonia: alveoli become filled with fluid. Caused by bacterial or viral infection Lung Cancer: a disease in which tumors form in the lungs as a result of irregular and uncontrolled cell growth


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