A. Respiration: 5 parts:
1. Pulmonary ventilation* = breathing;
2. External respiration* = air into lungs; gas exchange (O2load/ CO2 unload); air out;
3. Transport of respiratory gases = gases in blood transported from lungs to body cells and back to lungs;
4. Internal respiration = exchange of gases at body capillaries (O2 unload/CO2 load).
5. Cellular respiration = use of oxygen by cells to produce energy (production of CO2).
* Only these two portions are included in the respiratory system.
II. ORGANS OF THE RESPIRATORY SYSTEM:
See Fig 19.1, page 733 and Summary Table 19.1, page 744.
A. Upper Respiratory Organs (UROs): See Fig 19.2, page 734.
1. The UROs are lined with mucous membranes:
See Fig 19.3, page 734.
a. ET/CT with many goblet cells (mucus);
b. Specifically, pseudostratified columnar ET in the trachea,
o The mucus functions to trap debris.
o The cilia beats the debris to the pharynx to be swallowed and destroyed by digestive enzymes.
o This tissue also serves to warm and moisten incoming air.
2. Nose(external nares or nostrils)
a. bone & cartilage with internal hairs;
b. traps large particles (i.e. filters air).
3. Nasal cavity (separated by nasal septum)
a. bone & cartilage lined with mucous membranes;
b. warms and moistens incoming air;
c. olfactory reception;
d. resonating chambers for speech.
II. ORGANS OF THE RESPIRATORY SYSTEM
A. Upper Respiratory Organs (UROs): (continued)
4. Nasal conchae(within nasal cavity) See Fig 19.2, page 734.
a. superior, middle & inferior;
b. divide nasal cavity into a series of groove-like passageways;
c. lined by mucous membranes;
d. increase turbulence of incoming air (to better warm, moisten and filter).
5. Paranasal sinuses Fig 9.4, page 736
a. within 4 skull bones (frontal, ethmoid, sphenoid, maxillary);
b. drain into nasal cavity;
c. lined with mucous membranes;
d. reduce weight of skull;
e. resonating chambers for speech.
6. Pharynx (or throat) See Fig 19.2, page 734.
a. wall of skeletal muscle lines with mucous membranes;
b. passageway for air and food;
c. resonant chamber for speech sounds;
d. three parts:
o nasopharynx (uppermost);
o oropharynx (middle);
o laryngopharynx (lowest).
7. Larynx (or voice box) See Fig 19.5 and 19.6, pages 737.
a. Anatomy (9 pieces of cartilage)
o thyroid cartilage (Adam's apple);
o epiglottis closes off the airway during swallowing;
o two pairs of vocal folds (false over true vocal cords);
o glottis = triangular slit; opening between two pairs of vocal cords.
o cricoid cartilage = ring of hyaline cartilage attached to first ring of trachea; site of tracheotomy.
o arytenoid cartilages;
o corniculate cartilages;
o cuneiform cartilages.
II. ORGANS OF THE RESPIRATORY SYSTEM
A. Upper Respiratory Organs (UROs): (continued)
7. Larynx (or voice box) See Fig 19.7, page 738.
b. Voice production
Mucous membranes form 2 pairs of folds:
o upper ventricular folds (false vocal cords);
o lower vocal folds (true vocal cords);
o space between them = glottis.
· Sound originates from vibration of the vocal folds, but other structures (pharynx, mouth, nasal cavity, and paranasal sinuses) convert that sound into recognizable speech.
B. Lower Respiratory Organs:
1. Trachea (windpipe) See Fig 19.8, page 738.
a. Location = mediastinum; anterior to esophagus; extends from larynx to T5;
b. Structure:
o 16-20 incomplete rings of hyaline cartilage = C-rings;
o Rings are completed by trachealis muscle and elastic CT facing esophagus;
See Fig 19.9, page 739.
o lined by mucous membranes (pseudostratified columnar ET);
See Fig 19.10, page 739.
o Carina = point where trachea divides into right & left bronchus;
c. Function = support against collapse; continue to warm, moisten & filter air.
II. ORGANS OF THE RESPIRATORY SYSTEM
B. Lower Respiratory Organs:
2. Bronchial tree within lungs See Fig 19.12, page 740.
a. primary (1o) bronchus leads into each lung and then branches into
b. secondary (2o) bronchi, which branch to each lobe and then branch into
c. tertiary (3o) bronchiwhich each serve one of 10 lobules (bronchopulmonary segment); that divide into
d. bronchioles which branch several times into tubes called
e. terminal bronchioles.
3. Structure of the Respiratory Tubes
a. Each terminal bronchiole subdivides into microscopic branches called… Fig 19.14, page 741.
o respiratory bronchioles (lined by simple squamous epithelium), which subdivide into several (2-11)…
o alveolar ducts, which terminate into numerous…
o alveoli and alveolar sacs (2-3 alveoli that share a common opening).
With this extensive branching:
o Epithelium changes from ciliated pseudostratified columnar epithelium to non-ciliated simple columnar epithelium in terminal bronchioles;
o Cartilage decreases;
o Smooth muscle increases(innervated by ANS and hormones):
· Parasympathetic and histamine constrict bronchioles (i.e. bronchoconstriction);
· Sympathetic and epinephrine dilate bronchioles (i.e. bronchodilation).
II. ORGANS OF THE RESPIRATORY SYSTEM
B. Lower Respiratory Organs:
4. Function of the Respiratory Tubes and Alveoli
a. ALVEOLI (microscopic air sacs)
See Fig 19.15, page 741 & Fig 19.33, page 757.
o wall consists of two types of epithelial cells and macrophages;
· Type I Alveolar cells form a continuous simple squamous lining of the alveolar wall;
· Type II Alveolar cells interrupt above lining and secrete surfactant:
1. complex mixture = detergent;
2. lowers surface tension and prevents alveolar collapse.
· Alveolar Macrophages remove dust particles and other debris from alveolar spaces.
o See scanning electron micrographs of alveoli on page 742.
b. Alveolar-Capillary (Respiratory) Membrane
See Fig 19.33, page 757.
o Composition:
· simple squamous epithelium of alveolus;
· basement membrane of alveolus;
· endothelium of the lung capillary;
· basement membrane of lung cap.
o Structure = thin (0.5 um in thickness).
o Function = allows for rapid diffusion of gases (from [high] to [low]).
· External Respiration.
*The lungs contain more than 300 million alveoli = SA of 70m2 for gas exchange at one time!
o Blood Supply to Lungs (two fold):
· pulmonary circuit (deoxygenated blood);
· Oxygenated blood is delivered through bronchial arteries (off thoracic aorta).
II. ORGANS OF THE RESPIRATORY SYSTEM
B. Lower Respiratory Organs:
5. LUNGS See Fig 19.12, page 740.
a. Location = thoracic cavity;
b. Description:
o paired, cone-shape organs;
o covered by pleural (serous) membranes:
· visceral pleura;
· parietal pleura;
· pleural cavity filled with serous fluid.
* In contrast to the lubrication function we attributed to serous fluid in the past, the pleural fluid has a very high surface tension that allows the two membranes to act as one.
c. Gross Anatomy:
o Each lung is divided into lobes by fissures:
· Right lung has 3 lobes;
· Left lung has 2 lobes.
o Each lobe:
· receives a secondary bronchus;
· is divided into lobules (bronchopulmonary segment)
o Each lobule: See Fig 19.14, page 741.
· is wrapped in elastic CT;
· contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole.
III. PHYSIOLOGY OF RESPIRATION
Recall that the function of the respiratory system is to supply cells with oxygen and remove carbon dioxide. The three basic processes are pulmonary ventilation, external respiration and internal respiration.
A. Breathing Mechanism (Pulmonary Ventilation)
Breathing involves two actions, inspiration & expiration.
1. Inspiration (inhalation) = breathing air in.
a. Force necessary is atmospheric pressure: Fig 19.21, page 746.
o When the diaphragm is at rest (curved upward):
· The air pressure outside the lungs is equal to the air
pressure inside the lungs (1 atm or 760 mm Hg).
· The thoracic cavity has a given size and volume.
o During inspiration: See Fig 19.23, page 747.
· The diaphragm muscle pushes downward;
· The size of thoracic cavity increases;
· The pressure in the thoracic cavity decreases (758 mm Hg) (Boyles' Law);
· The air pressure inside the thoracic cavity (lungs) is less than the atmospheric pressure and therefore air rushes into lungs to equalize the pressure gradient.
o Pleural Membranes aid in inspiration:
See Fig 19.20, page 744.
· Serous fluid between membranes primarily contains water;
· The water in the serous fluid has great surface tension and therefore,
· Membranes move together:
1. thoracic cage expands;
2. parietal pleura expands;
3. visceral pleura expands;
4. lungs expand.
o Contraction of the external intercostal musclesalso aid inspiration.
III. PHYSIOLOGY OF RESPIRATION
A. Breathing Mechanism (Pulmonary Ventilation)
2. Expiration = breathing out depends on two factors:
See Fig 19.25, page 749.
a. the elastic recoil of tissues that were stretched during inspiration (i.e. tissues bouncing back to shape).
b. the inward pull of surface tension due to the alveolar fluid.
* See Summary of inspiration and expiration in Table 19.2, page 747 and Table 19.3, paged 749.
3. Atelectasis (Collapsed Lung)
a. At the end of an expiration, the alveoli tend to recoil inward and collapse on themselves;
b. Surfactant (mixture of phospholipid & proteins) produced by Type II Alveolar cells decreases the surface tension in the lungs;
c. As the alveoli become smaller during expiration, the surfactant overcomes the pressure differential and allows the alveoli to remain inflated.
* Respiratory Distress Syndrome (RDS) in newborns (collapsed lungs) occurs due to the lack of surfactant in the alveoli.
* See purple box on page 747.
III. PHYSIOLOGY OF RESPIRATION
A. Breathing Mechanism (Pulmonary Ventilation)
4. Respiratory Volumes and Capacities See Fig 19.26, page 749.
a. are measured by a spirometer;
b. include the following 4 volumes from which 4 capacities may be calculated:
o Tidal Volume = amount (volume) of air that enters the lungs during normal inspiration and leaves the lungs during normal expiration; approximately 500 ml;
o Inspiratory Reserve Volume (IRV) = the amount of air the can be forcibly inhaled after a normal tidal inspiration; approximately 3000 ml;
o Expiratory Reserve Volume (ERV) = the amount of air that can be forcibly exhaled after a normal tidal expiration; approximately 1100 ml;
o Residual Volume (RV) = amount of air that always remains in lungs; 1200 ml;
o Vital Capacity (VC) = the maximum amount of air that can be exhaled after a maximum inhalation;
· VC = TV + IRV + ERV = 4600 ml.
o Inspiratory Capacity = total amount of air that can be inspired after a tidal expiration.
· IC = TV + IRV
o Functional Residual Capacity = amount of air left in the lungs after a tidal expiration.
· FRC = ERV + RV
o Total Lung Capacity = VC + RV; approximately 6 L.
See Summary Table 19.4, page 750.
5. Alveolar Ventilation
a. Minute Ventilation (MV)= TV X RR (respiratory rate)
o Amount of air that enters and exits respiratory system in one minute
o About 6000mL
b. Anatomic dead space (ADS)– air space in respiratory passageways not involved in gas exchange = 150mL
c. Alveolar ventilation = the actual amount of air involved in gas exchange
o AV = (TV – ADS) X RR
o AV = (500mL – 150mL) X 12 breaths per minute
o AV = 350mL X 12 b/m
o AV = 4200mL
III. PHYSIOLOGY OF RESPIRATION
A. Breathing Mechanism (Pulmonary Ventilation)
6. Non-Respiratory Air Movements Table 19.5, page 751
Modified respiratory movements occur in addition to normal breathing; usually the result of reflexes.
a. Cough = sends blast of air through and clears lower respiratory tract;
b. Sneeze = forcefully expels air through nose & mouth;
c. Laugh = a deep breath released in a series of short convulsive expirations;
d. Hiccup = spasmodic contraction of diaphragm;
e. Yawn = deep inspiration through open mouth; (ventilates alveoli).
IV. CONTROL OF BREATHING
A. Normal breathing = rhythmic; involuntary.
B. Nervous Control = Respiratory Center:
1. located in pons & medulla of brain stem;
a. See Fig 19.28, page 753.
2. Medullary Rhythmicity area
a. composed of dorsal respiratory group which controls the basic rhythm of breathing;
b. ventral respiratory group which controls forceful breathing.
3. Pneumotaxic area = pons:
a. controls rate of breathing.
* See Fig 19.29, page 754 for Summary of Nervous Control of Breathing
IV. CONTROL OF BREATHING
C. Factors Affecting Breathing See Fig 19.30, page 755.
1. Chemoreceptors in carotid & aortic bodies of some arteries are sensitive to:
a. Low levels of oxygen;
b. High levels of CO2;
o affect chemosensitive areas (central chemoreceptors) of respiratory center and breathing rate and depth increases.
c. Effector Sites:
o diaphragm/intercostals
o smooth muscle of terminal bronchioles
d. Hyperventilation
o rapid, shallow breathing increases O2 level;
o breathing into paper bag rich in CO2 normalizes gas concentrations
D. Factors that influence breathing:
See Table 19.6, page 756.
1. Stretch of Tissues; Inflation Reflex – prevent over inflation
2. Low blood oxygen;
3. High Blood carbon dioxide;
4. Low pH;
5. Others: temperature, pain, and irritation of airways.
V. ALVEOLAR GAS EXCHANGES
(External Respiration) See Fig 19.33, page 757, and Fig 19.35, page 758.
A. Definition = the exchange of oxygen and carbon dioxide between the alveoli and lung blood capillaries.
B. The pressure of gas determines the rate at which it will diffuse from region to region (Dalton
C. Air is a mixture of gases:
1. 78% Nitrogen
2. 21% Oxygen
3. .04% Carbon Dioxide
D. In a mixture of gases, the amount of pressure that each gas creates = partial pressure.
In air: O2 = 21%; PO2= 104 mm Hg
CO2= .04%; PCO2 = 40 mm Hg
E. The partial pressure of a gas is directly related to the concentration of that gas in a mixture.(Dalton
F. 
Diffusion of gases through the respiratory membrane proceeds from where a gas is at high pp low pp.
Diffusion of gases through the respiratory membrane proceeds from where a gas is at high pp low pp. Alveolus
PCO2= 40 mm Hg
PO2= 104 mm Hg
__________________________________________________________________
PCO2= 45 mm Hg PO2= 40 mm Hg
Capillary
Therefore, CO2 will flow from lung capillary alveolus & 
O2 will flow from alveolus lung capillary.G. The rate of diffusion of gases also depends on a number of factors, including the following:
1. gas exchange surface area;
2. diffusion distance;
3. breathing rate and depth.
VI. INTERNAL RESPIRATION
A. Definition = the exchange of oxygen and carbon dioxide between tissue capillaries and tissue cells.
B. In tissue cell: pCO2 = 45; pO2 = 40;
In tissue cap: pCO2 = 40; pO2= 95.
See Figure 19.37, page 761.
C. Therefore, oxygen moves from the tissue cap into the tissue cell and carbon dioxide moves from the tissue cell into the tissue cap.
VII. GAS TRANSPORT (in Blood)
A. Oxygen
1. binds with hemoglobin (Hb) in red blood cells to form oxyhemoglobin;
2. A weak bond is formed so oxygen can be delivered (released into) to tissues when needed.
3. The release of oxygen from hemoglobin depends on many factors:
a. high blood [CO2];
b. low blood pH (acidity);
c. high blood temperature.
d. See oxyhemoglobin dissociation curves Figures 19.38, 19.39, page 761
o To remember these conditions, think of what happens in a skeletal muscle during exercise, when oxygen is required.
4. Carbon Monoxide (CO)binds to hemoglobin more efficiently than oxygen.
a. If the hemoglobin (that is suppose to bind with oxygen) is bound to CO, much less Hb is available to bind and transport oxygen to the tissues; Hypoxia results.
VII. GAS TRANSPORT
B. Carbon Dioxide (CO2)
1. CO2is transported in 3 forms:
a. dissolved CO2= 7%
b. carbaminohemoglobin= 23%
c. bicarbonate ions= 70%
2. In tissues, CO2 is produced by cellular respiration.
a. This CO2 combines with H2O to form H2CO3(Carbonic acid) which then
b. dissociates under the influence of carbonic anhydrase to release
c. H+and bicarbonate ion (HCO3-):
CO2+ H2O H2CO3 H+ + HCO3-3. RXN is reversed in lungs & CO2 is expelled during expiration.
VIII. LIFE SPAN CHANGES
A. Exposure to pollutants, smoke, etc., increases the risk of developing respiratory illnesses.
B. Loss of cilia, thickening of mucus, and impaired macrophages increases the risk of infection as one ages.
C. Breathing becomes more difficult as one ages due to:
1. calcified cartilage
2. skeletal changes
3. altered posture
4. replacement of bronchiole smooth muscle by fibrous connective tissue.
D. Vital Capacity decreases with age.
IX. Homeostatic Imbalances: Disorders of the Respiratory System
A. Deviated Septum. See purple box on page 733.
B. Effects of Cigarette Smoking. See Clinical Application 19.1, pages 735.
C. Epiglottitis. See purple box on page 739.
D. Cystic Fibrosis. See purple box on page 743.
E. Lung Irritants. See Clinical Application 19.2, page 745.
F. Respiratory Distress Syndrome. See purple box on page 747.
G. Pneumothorax. See purple box on page 748.
H. Respiratory Disorders that Decrease Ventilation. See Clinical Application 19.3, page 752.
I. Disorders Impairing Gas Exchange. See Clinical Application 19.5, page 759.
X. Other Interesting Topics Concerning the Respiratory System
A. Tracheotomy. See page 739 and Fig 19.11, page 739.
B. Bronchoscopy. See purple box on page 742.
C. Artificial Respiration. See purple box on page 743.
D. Exercise and Breathing. See Clinical Application 19.4, page 756.
XI. Clinical Terms Related to the Respiratory System See pages 764 and 766.
XII. Innerconnections of the Respiratory System See page 765.
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