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 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

Copyright © 2003 a TBM production. All rights and lefts reserved The human respiratory system Figure 22.6A Nasal cavity Left lung Pharynx (Esophagus) Larynx Trachea Bronchus Bronchiole Diaphragm (Heart) Right lung

Copyright © 2003 a TBM production. All rights and lefts reserved 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 F G H B Nasal Cavity: warms, cleans and humidifies air Epiglottis: flap to keep food from entering the trachea

Copyright © 2003 a TBM production. All rights and lefts reserved 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 F G H B

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

Copyright © 2003 a TBM production. All rights and lefts reserved 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-rich blood Oxygen-poor blood Alveoli Blood capillaries Bronchiole

Copyright © 2003 a TBM production. All rights and lefts reserved Alveoli A B C D E A. Respiratory Bronchiole B. Alveolar Chamber C. Alveolar Epithelium D. Red blood Cells E. Capillary Epithelium

Copyright © 2003 a TBM production. All rights and lefts reserved Alveoli A B C D E A. Respiratory Bronchiole Last tube of air passage B. Alveolar Chamber inside where O 2 diffuses out and CO 2 in C. Alveolar Epithelium D. Red blood Cells erythrocytes E. Capillary Epithelium the capillary

Copyright © 2003 a TBM production. All rights and lefts reserved Order of O 2 flow Nasal Cavity Pharynx Larynx Trachea Bronchi Bronchiole Alveoli

Copyright © 2003 a TBM production. All rights and lefts reserved Diffusion of O 2 and CO 2 Gasses must diffuse through 3 membranes –Alveolar Epithelium –Capillary Epithelium –Red blood cell epithelium

Copyright © 2003 a TBM production. All rights and lefts reserved Breathing is the alternation of inhalation and exhalation 22.8 Breathing ventilates the lungs Figure 22.8A Rib cage expands as rib muscles contract Air inhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Rib cage gets smaller as rib muscles relax Air exhaled

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

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

Copyright © 2003 a TBM production. All rights and lefts reserved During exercise, the CO 2 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 CONTROL CENTERS—stimulated by: CO 2 increase / pH decrease in blood Nerve signal indicating low O 2 level O 2 sensor in artery Pons Medulla Nerve signals trigger contraction of muscles Diaphragm Rib muscles

Copyright © 2003 a TBM production. All rights and lefts reserved The heart pumps oxygen-poor blood to the lungs –In the lungs it picks up O 2 and drops off CO 2 –In the tissues, cells pick up O 2 and drop off CO 2 –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

Copyright © 2003 a TBM production. All rights and lefts reserved Gas exchange in the body 21% O2 in blood 16% O2 in body cells O2 diffuses into cell

Copyright © 2003 a TBM production. All rights and lefts reserved Hemoglobin is a protein in red blood cells –It carries most of the oxygen in the blood –Oxyhemoglobin formed Heme group Iron atom Polypeptide chain O 2 loaded in lungs O 2 unloaded in tissues O2O2 O2O2

Copyright © 2003 a TBM production. All rights and lefts reserved Gas exchange in the body.04% CO2 in blood 3% CO2 in body cells CO2 diffuses out of cells into the blood

Copyright © 2003 a TBM production. All rights and lefts reserved 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 –Enzymes in RBC cause the change TISSUE CELL CO 2 produced INTERSTITIAL FLUID CO 2 BLOOD PLASMA WITHIN CAPILLARY Capillary wall H2OH2O H 2 CO 3 Carbonic acid RED BLOOD CELL HCO 3 – +H+H+ Hemoglobin picks up CO 2 and H + Bicarbonate HCO 3 –

Copyright © 2003 a TBM production. All rights and lefts reserved Most CO 2, 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 CO 2 H2OH2O H 2 CO 3 HCO 3 – +H+H+ Hemoglobin releases CO 2 and H + HCO 3 – CO 2

Copyright © 2003 a TBM production. All rights and lefts reserved Cellular Respiration Food is Carbon based (ex. C 6 H 12 O 6 ) When food is burned, CO 2 is produced, leaving excess H + H combines with inhale O 2 to form H 2 O If there is no O 2, H + builds up, body becomes acidic Low acidity (= High H + ) is fatal

Copyright © 2003 a TBM production. All rights and lefts reserved 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, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus

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

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