Transcript 10 Human Biology The Respiratory System:
Human Biology
Concepts and Current Issues Seventh Edition Michael D. Johnson 10
The Respiratory System: Exchange of Gases
Lecture Presentations by Robert J. Sullivan Marist College © 2014 Pearson Education, Inc.
Respiration Takes Place Throughout the Body
Breathing (ventilation)
: moving air in and out of lungs
External respiration
: gas exchange between air and blood in the lungs
Internal respiration
and tissues : gas exchange between blood
Cellular respiration
: oxygen use to produce ATP, carbon dioxide as waste © 2014 Pearson Education, Inc.
Respiratory System Consists of Upper and Lower Respiratory Tract
Upper respiratory tract – Nose, nasal passages, sinuses – Pharynx Lower respiratory tract – Larynx – Trachea – Bronchi and bronchioles – Lungs – Alveoli © 2014 Pearson Education, Inc.
Figure 10.1
Nose Passageway for air Mouth Passageway for food and air Epiglottis Covers larynx during swallowing Pleural membranes Cover the lungs and line the chest cavity Lung Organ of gas exchange Intercostal muscle Moves ribs during respiration Rib Diaphram Skeletal muscle of respiration Right lung
© 2014 Pearson Education, Inc.
Left lung Nasal cavity Filters, warms, and moistens air Tongue Pharynx (Throat) Common passageway for air, food, and liquid Larynx (Voice box) Production of sound Trachea (Windpipe) Main airway Bronchi Branching airways Alveoli Air sacs for gas exchange
Upper Respiratory Tract Filters, Warms, and Humidifies Air
Functions of nose and pharynx – Acts as passageway for respiration – Has receptors for smell – Filters larger foreign material from incoming air, inhaled microorganisms are entrapped in mucus – Moistens and warms incoming air – Has resonating chambers for voice © 2014 Pearson Education, Inc.
Figure 10.2
Sinuses Nasal cavity External nose Opening of the auditory tube Nostril Pharynx Tongue Epiglottis Glottis Larynx Trachea Esophagus
© 2014 Pearson Education, Inc.
Lower Respiratory Tract Exchanges Gases
Larynx
– Epiglottis: flexible flap of cartilage that routes air and food appropriately – – Vocal cords: assist in sound production Maintains an open airway
Trachea
– – Transports air to and from lungs Also known as the “windpipe” – – Kept open by C-shaped rings of cartilage Lined with mucus-secreting ciliated epithelium – Traps foreign particles and moves them up and out of the lungs – Cough reflex © 2014 Pearson Education, Inc.
Figure 10.3
Larynx Right bronchus Clusters of alveoli
© 2014 Pearson Education, Inc.
Trachea Left bronchus Bronchioles
Figure 10.4
Epiglottis Larynx Upper trachea
© 2014 Pearson Education, Inc.
Position of the vocal cords during quiet breathing.
Vocal cords Opening into larynx (glottis open) Closed glottis Position of the vocal cords during sound production.
Figure 10.5
Epithelial tissue Connective tissue Cartilage rings Smooth muscle Relaxed state.
The maximum diameter facilitates air movement in and out.
© 2014 Pearson Education, Inc.
During the cough reflex, the smooth muscle contracts briefly, reducing the diameter of the trachea.
Combined with contraction of the abdominal muscles, this increases the velocity of air movement, forcibly expelling irritants or mucus from the trachea.
Lower Respiratory Tract Exchanges Gases
Bronchi – Trachea branches into two airways —right and left bronchi – Contain ciliated epithelia, smooth muscle, cartilage Bronchioles – Smaller branches, lack cartilage Functions of bronchi and bronchioles – Air transport – Clean, warm, and humidify incoming air – Cleansing activity of cilia damaged by smoking leading to the development of smoker’s cough © 2014 Pearson Education, Inc.
Figure 10.6
Healthy airway.
© 2014 Pearson Education, Inc.
Smoker’s airway.
The Lungs Are Organs of Gas Exchange
Supportive tissue enclosing the bronchi, bronchioles, blood vessels, and alveoli (air pockets where gas exchange occurs) Lungs are located in the thoracic cavity Each lung is enclosed in two layers of pleural membranes Area between pleural membranes (pleural cavity) contains fluid which reduces friction as lungs move Three lobes in right lung, two in left lung Lungs function relatively independently of each other © 2014 Pearson Education, Inc.
Figure 10.7
Trachea The three lobes of the right lung
© 2014 Pearson Education, Inc.
Heart (enclosed in pericardium) Pleural membrane lining thoracic cavity Rib Muscle Pleural cavity Pleural membrane attached to lung The two lobes of the left lung Diaphragm
Gas Exchange Occurs in Alveoli
Alveoli: tiny air-filled sacs clustered at end of terminal bronchioles Walls of each alveolus are composed of only one squamous epithelial cell layer Combined surface area of alveoli: 800 ft 2 Lipoprotein surfactant secreted by alveolar cells reduces surface tension enabling inflation of alveoli – Premature infants may lack adequate surfactant and experience infant respiratory distress syndrome – This may be successfully treated with surfactant therapy © 2014 Pearson Education, Inc.
Pulmonary Capillaries Bring Blood and Air Into Close Contact
Lungs receive deoxygenated blood from right ventricle of heart through pulmonary arteries Pulmonary capillaries allow blood to come into close proximity with air in alveoli Venules and veins collect the oxygenated blood from alveolar capillaries and return it to the left side of the heart for distribution throughout the body © 2014 Pearson Education, Inc.
Figure 10.8
Blood flow Bronchiole Small pulmonary vein Small pulmonary artery Bronchioles end in clusters of alveoli, each surrounded by capillaries . CO 2 and O 2 are exchanged across the capillary and alveolar walls by diffusion.
Photo of the surface of alveoli covered with capillaries .
© 2014 Pearson Education, Inc.
Blood flow Pulmonary arteriole Capillary network on surface of alveolus Air in aveolus CO 2 O 2 Capillary Epithelial cell of alveolus Pulmonary venule Blood flow
Defenses of the Respiratory Tract
Mucus
—entraps microorganisms
Cilia
—push microorganisms and mucus up and out of respiratory tract – Smoking —damages cilia, impairs this defense – Smokers cough
Cough reflex
© 2014 Pearson Education, Inc.
The Process of Breathing Involves a Pressure Gradient
Inspiration/expiration: air in/air out cycle 1.
Relaxed state – Diaphragm and intercostal muscles relaxed 2.
Inspiration (inhale) – Diaphragm contracts, pulling muscle down; intercostal muscles contract, elevating chest wall and expanding volume of chest, lowering pressure in lungs, pulling in air 3.
Expiration (exhale) – Muscles relax; diaphragm resumes dome shape; intercostal muscles allow chest to lower, resulting in increase of pressure in chest and expulsion of air © 2014 Pearson Education, Inc.
Figure 10.9
External intercostals Diaphragm No air movement 1 Relaxed state Air flows in 2 Inspiration Ribs move upward and outward due to muscle contraction Lung volume increases, causing air pressure to fall Diaphragm contracts and flattens, moving downward Air flows out 3 Expiration Ribs return to resting position Lung volume decreases, causing air pressure to rise Diaphragm relaxes
© 2014 Pearson Education, Inc.
Lung Volumes and Vital Capacity Measure Lung Function
Tidal volume
– Volume of air inhaled and exhaled in a single breath
Dead space volume
– Volume of air that remains in the airways and does not participate in gas exchange
Vital capacity
– Maximal volume that can be exhaled after maximal inhalation © 2014 Pearson Education, Inc.
Lung Volumes and Vital Capacity Measure Lung Function
I
nspiratory reserve volume
– Volume of air that can be inhaled beyond the tidal volume
Expiratory reserve volume
– Volume of air that can be forcibly exhaled beyond the tidal volume
Residual volume
– Volume of air remaining in the lungs, even after a forceful maximal expiration Measured by
spirometer
© 2014 Pearson Education, Inc.
Figure 10.10
A recording of lung capacity. After several normal breaths, the person inhales and then exhales maximally. The volumes indicated by the green line are for a normal person. The orange line is typical of a patient with emphysema.
6000 5000 4000 3000 2000 1000 0 Normal person Person with emphysema Inspiratory reserve Tidal volume Expiratory reserve Vital capacity Residual volume Time Patient having his lung capacity determined with a spirometer.
© 2014 Pearson Education, Inc.
Gas Exchange and Transport Occur Passively
Partial pressure
: the pressure exerted by one particular gas in a mixture of gases Partial pressure of a gas is proportional to its percentage of the total gas composition
A gas always diffuses down its partial pressure gradient, from higher to lower partial pressure
© 2014 Pearson Education, Inc.
External Respiration: The Exchange of Gases Between Air and Blood
O 2 diffuses from alveoli (P O2 : 104 mmHg) into blood (P O2 : 40 mmHg), down its partial pressure gradient C O2 diffuses from blood (P CO2 : 46 mmHg) into alveoli (P CO2 : 40 mmHg), down its partial pressure gradient © 2014 Pearson Education, Inc.
Internal Respiration: The Exchange of Gases with Tissue Fluids
O 2 diffuses down its pressure gradient from capillaries to interstitial fluid and then to cells CO 2 diffuses down its pressure gradient from cells to interstitial fluid to capillaries The O 2 and CO 2 each flow down their own pressure gradient, in opposite directions © 2014 Pearson Education, Inc.
Figure 10.11
Breathing Dry inhaled air O 2 160 CO 2 0.3
Moist exhaled air O 2 120 CO 2 27
© 2014 Pearson Education, Inc.
Pulmonary circulation Transport Lung capillaries Systemic veins and pulmonary artery O 2 40 CO 2 46 Systemic circulation Interstitial fluid surrounding cells O 2 <40 CO 2 >46 Capillary networks in head, limbs, torso, and internal organs Alveolar air O 2 104 CO 2 40 Alveolus 40 104 O 2 CO 2 100 46 Capillary External respiration Pulmonary vein and aorta O 2 100 CO 2 40 Internal respiration 46 CO 2 >46 O 2 <40 100 Cells of tissues
Slide 1
Hemoglobin Transports Most Oxygen Molecules
98% of O 2 in blood is carried bound to hemoglobin molecules in red blood cells Hb hemoglobin O 2 oxygen HbO 2 oxyhemoglobin 2% of O 2 is dissolved in plasma © 2014 Pearson Education, Inc.
Most CO
2
Is Transported in Plasma as Bicarbonate
70% of CO 2 is converted to and transported in the plasma as bicarbonate 10% of CO 20% of CO 2 2 is dissolved in plasma binds to hemoglobin for transport © 2014 Pearson Education, Inc.
Figure 10.12
Alveous O 2 Oxygen transport in arterial blood 2% dissolves in plasma Tissue cells Carbon dioxide transport in venous blood CO 2 CO 2 O 2 O 2 Hb Capillary HbO 2 Red blood cell 98% combines with hemoglobin (Hb) Approximately 98% of all the O (Hb) within red blood cells.
2 transported to the tissues by arterial blood is bound to hemoglobin Blood is transported from lungs to tissue CO 2 CO 2 Enzyme H 2 O 10% dissolves in plasma 20% combines with hemoglobin (Hb) CO 2 Hb HbCO 2 H 2 CO 3 70% is converted to HCO 3
. HCO 3
diffuses into plasma H
HCO 3
Most of the CO 2 transported to the lungs by venous blood is converted to bicarbonate (HCO dissolved HCO 3
. 3
) within red blood cells and then is carried in plasma as The rest is either dissolved in plasma as CO 2 or transported within the red blood cells bound to hemoglobin.
© 2014 Pearson Education, Inc.
The Nervous System Regulates Breathing
Respiratory center is located in the medulla oblongata – Establishes basic breathing pattern – Neurons in medulla generate impulses every 4 –5 seconds – Stimulates intercostal muscles and diaphragm © 2014 Pearson Education, Inc.
Chemical Receptors Monitor CO
2
, H
, and O
2
Levels
Monitoring of CO 2 – levels Receptors in medulla oblongata monitor CO 2 indirectly – Receptors monitor H levels ions in cerebrospinal fluid – A rise in P CO2 in arterial blood will cause a rise in H in cerebrospinal fluid, which will signal medulla oblongata to increase respiratory rate – This is the primary regulator of respiration under normal conditions © 2014 Pearson Education, Inc.
Chemical Receptors Monitor CO
2
, H
, and O
2
Levels
Monitoring P O2 – Aortic and carotid bodies monitor P O2 – Become activated if P O2 falls by at least 20% – Will increase rate and depth of breathing in response to sufficiently lowered arterial P O2 The rate and depth of normal breathing is determined by the need to get rid of CO obtain O 2 2 rather than the need to © 2014 Pearson Education, Inc.
We Can Exert Some Conscious Control
Conscious control resides in the cerebral cortex – Able to modify breath to speak and sing – Able to hold breath temporarily, but can’t override automatic controls located in medulla oblongata indefinitely © 2014 Pearson Education, Inc.
Figure 10.13
The respiratory center: establishes a regular pattern of breathing 1 Receptor cells near the respiratory center respond to changes in cerebrospinal fluid H
caused by increases in arterial CO 2 .
2 Receptor cells in the carotid and aortic bodies respond to large decreases in arterial O 2 .
Carotid bodies Aortic bodies 3 Higher centers in the cortex can exert conscious control over respiration.
Medulla oblongata Intercostal muscles Diaphragm
© 2014 Pearson Education, Inc.
Disorders of Respiratory System
Reduced air flow or gas exchange
–
Asthma
: spasmodic contraction of bronchi – Caused by episodic allergic responses – Controlled by bronchodilators and corticosteroids –
Emphysema
: alveoli permanently impaired – Breathlessness due to decreased surface area for gas exchange – Most cases result from smoking © 2014 Pearson Education, Inc.
Disorders of Respiratory System
Reduced air flow or gas exchange (cont’d)
–
Bronchitis
: inflammation of bronchi – May be acute or chronic – Most cases related to smoking or air pollution –
Cystic Fibrosis
: an inherited condition – Abnormally thick mucus in lungs impedes air flow – Frequent pulmonary infections – Other organ systems may be affected © 2014 Pearson Education, Inc.
Microorganisms Can Cause Respiratory Disorders
Upper respiratory infections
–
Colds and flu
– Caused by viruses – Antibiotics not effective –
Pneumonia
: infection of the lungs – May be caused by bacteria or viruses – One of the top 10 causes of death in the United States – Treatment depends on cause © 2014 Pearson Education, Inc.
Microorganisms Can Cause Respiratory Disorders
Respiratory infections and intoxications
–
Tuberculosis
: bacterial infection that scars the lungs – May be active infection with symptoms, or dormant infection that will reactivate later – Diagnosis: tuberculin skin test and chest X-ray – Treatment: antibiotics –
Botulism
: poisoning by bacterial toxin – Toxin consumed in improperly preserved foods – Causes paralysis of skeletal muscles including intercostals and diaphragm © 2014 Pearson Education, Inc.
Lung Cancer Is Caused By Proliferation of Abnormal Cells
Cancer
: uncontrolled growth of abnormal cells Impairs air flow, gas exchange, blood flow 1/3 of all U.S. cancer deaths Causes – 90% of cases associated with smoking – Radon gas – Workplace chemicals such as asbestos © 2014 Pearson Education, Inc.
Figure 10.14
Normal lung.
© 2014 Pearson Education, Inc.
Cancerous lung.
Exposure to Asbestos Can Lead to Mesothelioma
Mesothelioma
– Deadly cancer of lining of lungs, heart, and abdomen – Most cases associated with asbestos exposure – Symptoms appear 20 –50 years after exposure – Often undiagnosed until well-established – Life expectancy after diagnosis: 8 –14 months © 2014 Pearson Education, Inc.
Pneumothorax and Atalectasis: A Failure of Gas Exchange
Pneumothorax
: collapse of one or more lobes of the lungs – Most often due to penetrating wound – Inability to inflate the lung results in poor gas exchange – Treatment: remove air from pleural cavity
Atalectasis
: lack of gas exchange due to alveolar collapse or fluid build-up – Can be a complication of surgery – May result from deficient surfactant © 2014 Pearson Education, Inc.
Congestive Heart Failure Impairs Lung Function
Congestive heart failure
: heart becomes a less efficient pump Failure of left side of heart – Blood pressure increases within pulmonary capillaries – Fluid build-up occurs in pulmonary interstitial spaces and alveoli – Impaired gas exchange Treatment: improve pumping action of heart and remove fluid © 2014 Pearson Education, Inc.