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CHAPTER 22 Respiration: The Exchange of Gases MECHANISMS OF GAS EXCHANGE Gas exchange is the interchange of O 2 and CO 2 between an organism and its.

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Presentation on theme: "CHAPTER 22 Respiration: The Exchange of Gases MECHANISMS OF GAS EXCHANGE Gas exchange is the interchange of O 2 and CO 2 between an organism and its."— Presentation transcript:

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2 CHAPTER 22 Respiration: The Exchange of Gases

3 MECHANISMS OF GAS EXCHANGE Gas exchange is the interchange of O 2 and CO 2 between an organism and its environment – It is also called respiration

4 Overview: Gas exchange involves breathing, the transport of gases, and the servicing of tissue cells Gas exchange is essential because energy metabolism requires O 2 and produces CO 2 CO 2 O2O2 ATP food

5 Animals exchange O 2 and CO 2 through moist body surfaces O 2 enters an animal and CO 2 leaves by diffusion through a respiratory surface – Respiratory surfaces are made up of living cells

6 Lungs alveoli  trachea  bronchi  bronchioles  alveoli capillaries (circulatory system)

7 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

8 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

9 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

10 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

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

12 Negative pressure breathing Diaphragm moves down & expands chest cavity pulls air into lungs inhaleexhale

13 Automatic Brain Control You don’t have to think to breathe! – medulla & pons – measure blood pH  CO 2 =  pH (acid) – coordinate breathing, heart rate & body’s need for energy – Medulla oblongata will stimulate diaphragm to contract.

14 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 O 2 and drops off CO 2(external respiration) – In the tissues, cells pick up CO 2 and drop off O 2-(Internal respiration) – Gases diffuse down pressure gradients in the lungs and the tissues

15 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 bloodlungs CO 2 O2O2 O2O2 bloodbody CO 2 O2O2 O2O2 capillaries in lungscapillaries in muscle

16 Gas exchange in the body

17 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 unloaded in tissues Polypeptide chain O2

18 Hemoglobin helps transport CO 2 and buffer the blood Hemoglobin helps buffer the pH of blood and carries some CO 2 Most CO 2 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

19 Transport of CO 2 Most CO 2 is transported to the lungs in the form of bicarbonate ions

20 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 O 2 and CO 2 with maternal blood that carries gases to and from the mother’s lungs At birth, increasing CO 2 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 Uterus Amniotic fluid

21 Breathing and Homeostasis Homeostasis – keeping the internal environment of the body balanced – need to balance O 2 in and CO 2 out – need to balance energy (ATP) production Exercise – breathe faster need more ATP bring in more O 2 & remove more CO 2 Disease – poor lung or heart function = breathe faster need to work harder to bring in O 2 & remove CO 2 O2O2 ATP CO 2

22 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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