Ch. 23: Respiratory System Flashcards
1
Q
Pulmonary ventilation.
A
Inhalation and exhalation of air. Involves exchange of air between atmosphere and alveoli caused by alternating pressure differences created by contraction and relaxation of respiratory muscles.
2
Q
External/pulmonary respiration.
A
Exchange of gases between alveoli and blood in pulmonary capillaries across the respiratory membrane. Pulmonary capillary blood gains O2 and loses CO2. Converts deoxygenated blood to oxygenated blood.
3
Q
Internal/tissue respiration.
A
Exchange of gases between blood in systemic capillaries and tissue cells. Blood loses O2 and gains CO2.
4
Q
Cellular respiration.
A
Within cells. The metabolic reactions that consume O2 and give off CO2 during ATP production.
5
Q
Structurally, the respiratory system consists of…
A
The upper respiratory system, and the lower respiratory system.
6
Q
Upper respiratory system.
A
Nose, nasal cavity, pharynx.
7
Q
Lower respiratory system.
A
Larynx, trachea, bronchi, lungs.
8
Q
Functionally, the respiratory system consists of…
A
The conducting zone, and the respiratory zone.
9
Q
Conducting zone.
A
Series of interconnecting cavities and tubes outside and within the lungs. Nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles. Filter, warm and moisten air and conduct it to the lungs.
10
Q
Respiratory zone.
A
Tubes and tissues within the lungs where gas exchange occurs. Respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli.
11
Q
What are the functions of the respiratory system?
A
Gas exchange, regulates blood pH, contains receptors for smell, filters inspired air, produces vocal sounds, excretes water and heat.
12
Q
External nose.
A
Visible. Supporting bony framework and cartilaginous framework covered with muscle and skin. Lined by mucous membrane.
13
Q
Which bones form the bony framework of the nose?
A
Frontal bone, nasal bones, maxillae.
14
Q
Which cartilages form the cartilaginous framework of the nose?
A
Septal nasal cartilage (anterior nasal septum), lateral nasal cartilages (inferior to nasal bones), alar cartilages (walls of nostrils). These are all hyaline cartilage.
15
Q
Internal nose.
A
Nasal cavity. Inferior to nasal bone. Superior to oral cavity. Lined with muscle and mucous membrane. Divided into a large inferior respiration region, and a small superior olfactory region.
16
Q
External nares.
A
Nostrils. Lead into nasal vestibules.
17
Q
What are the functions of the internal structures of the external nose?
A
Warming, moistening and filtering incoming air. Detecting olfactory stimuli. Modifying speech vibrations as they pass through the large hollow resonating chambers.
18
Q
Nasal septum.
A
Divides nasal cavity into right and left sides. Anterior part of the nasal septum consists of hyaline cartilage, vomer and perpendicular plate of ethmoid, maxillae and palatine bones.
19
Q
Anteriorly, the nasal cavity merges with…
A
The external nose.
20
Q
Posteriorly, the nasal cavity communicates with…
A
The pharynx through internal nares.
21
Q
Which ducts open into the nasal cavity and secrete mucus?
A
Paranasal sinus ducts. They also serve as resonating chambers for sound during speaking and singing.
22
Q
Which ducts open into the nasal cavity and secrete tears?
A
Nasolacrimal ducts.
23
Q
Which bones contain paranasal sinuses?
A
Frontal, sphenoid, ethmoid, maxillae.
24
Q
Which bones make up the lateral walls of the internal nose?
A
Ethmoid, maxillae, lacrimal, palatine, inferior nasal conchae bones.
25
Which bones make up the lateral walls of the internal nose?
Ethmoid, maxillae, lacrimal, palatine, inferior nasal conchae bones.
26
Which bones form the roof of the internal nose?
Ethmoid.
27
Which bones form the floor of the internal nose?
Palatine bones, and palatine processes of maxillae.
28
Respiratory region of nasal cavity.
Lined with ciliated pseudo stratified columnar epithelium with numerous goblet cells. Contains olfactory receptor cells, supporting cells and basal cells which make up the olfactory epithelium (cilia, no goblet cells).
29
Vestibule.
Lined by skin containing coarse hairs that filter dust.
30
Projections of ____ extend out of each lateral wall of the nasal cavity.
Superior, middle and inferior nasal conchae.
31
Nasal conchae.
Subdivide each side of the nasal cavity into a series of grovelike air passageways, called superior, middle and inferior nasal meatuses. They increase SA of the internal nose and prevent dehydration by trapping water droplets during exhalation.
32
Pharynx.
Funnel-shaped tube that starts at the internal nares and extends to the cricoid cartilage. Posterior to nasal and oral cavities. Superior to larynx. Anterior to cervical vertebrae. Wall is composed of skeletal muscles lined with mucous membrane.
33
Pharynx functions.
Passageway for air and food. Provides a resonating chamber for speech sounds. Contains the tonsils.
34
Divisions of the pharynx.
Nasopharynx, oropharynx, laryngopharynx.
35
How are pharynx muscles arranged?
Outer circular layer. Inner longitudinal layer.
36
Nasopharynx.
Superior. Posterior to nasal cavity. Extends to soft palate. Through the internal nares, the nasopharynx receives air and packages of dust-laden mucus. Lined with ciliated pseudo stratified columnar epithelium. Exchanges small amounts of air with auditory tubes to equalize air pressure between the middle ear and atmosphere. Contains the pharyngeal tonsil (adenoid).
37
Soft palate.
Forms the posterior part of the roof of the mouth. Arch-shaped muscular partition between the nasopharynx and oropharynx. Lined with mucous membrane.
38
5 openings in soft palate.
2 internal nares, 2 openings that lead to auditory tubes, 1 opening to oropharynx.
39
Oropharynx.
Intermediate. Posterior to oral cavity. Extends from soft palate to the hyoid bone. Contains the fauces which is the opening from the mouth. Passageway for air, food and drink. Subject to abrasion by food particles so it is lined with nonkeratinized stratified squamous epithelium. Contains the paired palatine and lingual tonsils.
40
Laryngopharynx.
Inferior. Hypopharynx. Begins at hyoid bone. Opens into the esophagus posteriorly, and the larynx anteriorly. Passageway for air, food and drink. Subject to abrasion by food particles so it is lined with nonkeratinized stratified squamous epithelium.
41
Larynx.
Short passageway between laryngopharynx and trachea. Extends to cricoid cartilage.
42
Larynx wall is composed of 9 pieces of cartilage.
3 occur singly: thyroid cartilage, epiglottis, cricoid cartilage.
3 occur in pairs: arytenoid, cuneiform, corniculate cartilages.
43
Which of the paired cartilages in the larynx wall are the most important?
Arytenoid cartilages, because they influence changes in position and tension of the vocal folds. Triangular pieces of hyaline cartilage located at posterior and superior border of cricoid cartilage.
44
Describe the extrinsic and intrinsic muscles of the larynx.
Extrinsic: connect the cartilages to other structures in the throat.
Intrinsic: connect the cartilages to each other, and attach to the rigid cartilages and vocal folds.
45
Laryngeal vestibule.
The part of the cavity of the larynx above the vestibular folds.
46
Infraglottic cavity.
The part of the cavity of the larynx below the vestibular folds.
47
Adam's apple.
Thyroid cartilage. Consists of 2 fused plates of hyaline cartilage that form the anterior wall of the larynx and give it a triangular shape.
48
Epiglottis.
Large leaf-shaped elastic cartilage covered with epithelium. Closes the larynx during swallowing to direct food and liquid into the esophagus.
Stem: taper inferior portion that is attached to the anterior rim of the thyroid cartilage.
Leaf: unattached and free to move up and down.
49
What occurs in the larynx and pharynx during swallowing?
Elevation of the pharynx widens it to receive the food and drink.
Elevation of the larynx causes the epiglottis to move down and form a lid over the glottis to close it off.
50
Glottis.
Consists of vestibule/vocal folds covered in mucous membrane. The rima glottidis/vestibuli is the space between the vocal folds.
51
Cricoid cartilage.
Ring of hyaline cartilage that forms the inferior wall of the larynx.
52
Corniculate cartilages.
Horn-shaped pieces of elastic cartilage located at the apex of each arytenoid cartilage.
53
What is the lining of the larynx superior to the vocal folds, and inferior to the vocal folds?
Superior: nonkeratinized stratified squamous epithelium.
Inferior: ciliated pseudo stratified columnar epithelium consisting of ciliated columnar cells, goblet cells and basal cells.
54
Describe cilia in the upper respiratory tract, and the lower respiratory tract.
Upper: cilia move mucus and trapped particles down toward pharynx.
Lower: cilia move mucus and trapped particles up toward pharynx.
55
False vocal cords.
Superior vestibular folds. Do not function in voice production. When they are brought together, they function in holding the breath against pressure in the thoracic cavity.
56
True vocal cords.
Inferior vocal folds. The principal structures of voice production.
57
What happens when intrinsic laryngeal muscles contract?
Moves rigid cartilages --> pulls elastic ligaments tight --> stretches vocal folds into the airways --> rima glottidis is narrowed. Arytenoid cartilages also pivot and slide.
58
How do the vocal folds produce sound?
Air passing through the larynx vibrates the vocal folds and produces sound by setting up sound waves in the column of air in the pharynx, nose and mouth.
59
What causes a variation in pitch?
Tension of vocal folds. If vocal folds are pulled taut by muscles, they vibrate rapidly to create a higher pitch.
60
Contraction of posterior cricoarytenoid muscles moves the...
Vocal folds apart to open the rima glottidis.
61
Contraction of lateral cricoarytenoid muscles moves the...
Vocal folds together to close the rima glottidis.
62
Whispering.
Occurs by closing all but the posterior part of the rima glottidis. Vocal folds do not vibrate. There is no pitch.
63
Trachea.
Anterior to esophagus. Extends from larynx to T5 where it divides into right and left primary bronchi. Tracheal wall consists of mucosa, submucosa, hyaline cartilage and adventitia.
64
Mucosa of trachea consists of...
Epithelial layer of ciliated pseudo stratified columnar epithelium, and an underlying layer of lamina propria that contains elastic and reticular fibres.
65
Submucosa of trachea consists of...
Areolar connective tissue that contains seromucous glands and their ducts.
66
Describe the horizontal rings of hyaline cartilage in the trachea.
16-20 rings are stacked on top of each other connected by dense connective tissue. The open part of each C-shaped ring faces posteriorly toward the esophagus and is spanned by a fibromuscular membrane. Within the fibromuscular membrane are transverse smooth muscle fibres and elastic connective tissue that allow the diameter of the trachea to change during inhalation and exhalation. The solid C-shaped rings provide a semi-rigid support to maintain latency so that the trachea wall does not collapse inward.
67
Adventitia of trachea consists of...
Areolar connective tissue that joins the trachea to surrounding tissues.
68
Trachea divides into...
A right primary bronchus that leads to the right lung.
A left primary bronchus that leads to the left lung.
69
Which bronchus is more likely to have a lodged aspirated object?
Right.
70
Primary bronchi contain...
Incomplete rings of cartilage. Lined by ciliated pseudo stratified columnar epithelium.
71
Carina.
Internal ridge. Formed by a posterior and inferior projection of the last tracheal cartilage. Located where the trachea divides into right and left primary bronchi. The mucous membrane of the carina is the most sensitive area of the larynx and trachea for triggering a cough reflex.
72
What does widening and distortion of the carina usually indicate?
Carcinoma of the lymph nodes around the region where the trachea divides.
73
How many lobes do the right and left lungs have?
Right: 3
Left: 2
74
Where and what do the primary bronchi divide into?
Upon entering the lungs, they divide into lobar/secondary bronchi; one for each lobe.
75
Lobar bronchi.
Continue to branch to form segmental/tertiary bronchi that supply the specific bronchopulmonary segments within the lobes.
76
Segmental bronchi.
Divide into bronchioles which branch again and again into terminal bronchioles.
77
Terminal bronchioles.
Contain club cells which are columnar non-ciliated cells interspersed among epithelial cells. Club cells protect against harmful effects of inhaled toxins and carcinogens, produce surfactant, and function as stem cells which give rise to various cells of the epithelium. Represent the end of the conducting zone of the respiratory system. Beyond the terminal bronchioles, the branches become microscopic and are named respiratory bronchioles or alveolar ducts.
78
Respiratory passages from the trachea to the alveolar ducts contain how many generations of branching?
23
79
What are 3 changes that occur as branching becomes more extensive in the bronchial tree?
1) Mucous membrane in the bronchial tree changes from ciliated pseudostratified columnar epithelium in the primary bronchi, lobar bronchi, and segmental bronchi to ciliated simple columnar epithelium with some goblet cells in larger bronchioles, to mostly ciliated simple cuboidal epithelial with no goblet cells in smaller bronchioles, to mostly non-conciliated simple cuboidal epithelium in terminal bronchioles.
2) Plates of cartilage gradually replace the incomplete rings of cartilage in primary bronchi, and disappear in distal bronchioles.
3) As the amount of cartilage decreases, the amount of smooth muscle increases. Because there is now no supporting cartilage, muscle spasms can close off the airways = asthma attack.
80
How are the lungs separated from each other?
By the heart and other structures of the mediastinum.
81
Parietal pleura of the lung.
Superficial layer. Lines the wall of the thoracic cavity.
82
Visceral layer of the lung.
Deep layer. Covers the lung surface.
83
Pleural cavity.
Between parietal and visceral pleura. Contains small amounts of lubricating pleural fluid secreted by the membranes.
84
The costal surface of the lungs...
Lies against the ribs and matches the rounded curvature of the ribs.
85
The mediastinal surface of the lungs...
Contains the hilum, through which bronchi, pulmonary blood vessels, lymphatic vessels, and nerves enter and exit.
86
The root of the lung.
The bronchi, pulmonary blood vessels, lymphatic vessels and nerves held together by the pleura and connective tissue.
87
Cardiac notch.
The left lung contains a medial concavity in which the apex of the heart lies.
88
Compare the sizes of the lungs.
The left lung is 10% smaller than the right lung.
89
Describe the shape of the right lung.
Thicker, broader, but shorter because the diaphragm is higher on the right side to accommodate the liver.
90
What divide each lung into lobules?
Fissures.
91
Oblique fissure.
In both lungs. Extends inferiorly and anteriorly.
Left lung: separates superior lobe and inferior lobe.
Right lung: superior part separates superior lobe and inferior lobe, inferior part separates inferior lobe and middle lobe.
92
Horizontal fissure.
In right lung only.
93
Each lobe receives its own...
Lobar bronchus.
Right main bronchus gives rise to 3 lobar bronchi: superior, middle and inferior.
Left main bronchus gives rise to 2 lobar bronchi: superior, inferior.
94
Lobar bronchi give rise to...
Segmental bronchi. There are 10 segmental bronchi in each lung.
95
Bronchopulmonary segment.
The portion of lung tissue that each segmental bronchus supplies. Each bronchopulmonary segment has many lobules, and each lobule is wrapped in elastic connective tissue and contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole.
96
Bronchial and pulmonary disorders that are localized in a ____ may be surgically removed without disrupting the surrounding lung tissue.
Bronchopulmonary segment.
97
Respiratory bronchioles.
Begin the respiratory zone since they have alveoli budding from their walls. As respiratory bronchioles penetrate more deeply into the lungs, the epithelial lining changes from simple cuboidal to simple squamous. These bronchioles also subdivide into alveolar ducts (simple squamous epithelium).
98
Alveolar sac.
Terminal duct of an alveolar duct. Composed of alveoli.
99
Type I alveolar cells.
More numerous. Simple squamous epithelial cells. Form a continuous lining of alveolar wall. Thin. Main sites of gas exchange. Underlying this layer of cells is an elastic basement membrane.
100
Type II alveolar cells.
Less numerous. Septal cells. Found between type I. Rounded or cuboidal epithelial cells with free surface containing microvilli. Secrete alveolar fluid.
101
Alveolar fluid.
Keeps the surface between the cells and the air moist.
102
Surfactant.
Included in alveolar fluid. A mixture of phospholipids and lipoproteins. Functions to lower the surface tension of alveolar fluid which reduces the tendency of alveoli to collapse.
103
Alveolar macrophages.
Present in alveolar walls. Phagocytes that remove fine dust particles and debris from the alveolar spaces. Also fibroblasts that produce reticular and elastic fibres.
104
On the outer surface of the alveoli...
The lobule's arteriole and venule disperse into a network of blood capillaries that consists of a single layer of endothelial cells and basement membrane.
105
Respiratory membrane.
Alveolar and capillary walls, blood plasma, and 4 layers.
1) A layer of type I and II alveolar cells and associated alveolar macrophages that constitute the alveolar wall.
2) An epithelial basement membrane underlying the alveolar wall.
3) A capillary basement membrane that is often fused to the epithelial basement membrane.
4) The capillary endothelium.
106
Lungs receive blood from the...
Pulmonary arteries and bronchial arteries.
Deoxygenated blood passes through the pulmonary trunk, which divides into a left pulmonary artery that enters the left lung, and a right pulmonary artery that enters the right lung.
Oxygenated blood passes through the aorta, which branches into the bronchial arteries to deliver oxygenated blood to the muscular walls of bronchi and bronchioles.
107
Return of oxygenated blood to the heart from the lungs occurs via...
Four pulmonary veins, which drain into the LA.
108
What happens to pulmonary blood vessels in response to hypoxia?
They constrict, diverting pulmonary blood from poorly ventilated areas of the lungs to well-ventilated areas of the lungs for more efficient gas exchange.
*In every other area of the body, hypoxia causes vasodilation to increase blood flow.
109
The rate of airflow and the amount of effort needed for breathing are influenced by...
Alveolar surface tension, compliance of lungs, airway resistance, and pressure difference.
110
Air moves into the lungs when...
The air pressure inside the lungs is less than the air pressure in the atmosphere.
111
Air moves out of the lungs when...
The air pressure inside the lungs is greater than the air pressure in the atmosphere.
112
Describe the air pressure just before inhalation?
The air pressure inside the lungs is equal to the air pressure of the atmosphere.
113
How do the lungs lower the air pressure inside the lungs?
They expand.
114
Boyle's Law.
The pressure and volume of a gas have an inverse relationship.
115
How do the lungs expand?
Diaphragm contracts, which flattens this muscle. External intercostals then contract to elevate the ribs.
116
Which nerves innervate the diaphragm?
Phrenic nerves.
117
Contraction of the diaphragm is responsible for ___ of air that enters the lungs.
75%. The remaining 25% is external intercostals.
118
Intrapleural pressure.
The pressure within the pleural cavity. Always a negative pressure lower than the atmospheric pressure. Allows the pleural cavity to function as a vacuum that attaches the visceral pleura to the chest wall.
119
Which muscles are responsible for deep or forced breathing?
Accessory muscles. Sternocleidomastoid (elevates sternum), scalene (elevate first 2 ribs), pectoralis minor (elevate 3-5 ribs).
120
Inhalation is a ____ , and exhalation is a ____ .
Inhalation: active process.
Exhalation: passive process.
121
How does exhalation occur?
It results from elastic recoil of the chest wall and lungs.
122
What are the inwardly directed forces that contribute to elastic recoil?
Recoil of elastic fibres that were stretched during inhalation, and the inward pull of surface tension due to the film of intrapleural fluid between the visceral and parietal pleurae.
123
When does exhalation become an active process?
Forceful breathing. Muscles of exhalation contract to increase pressure in the abdominal region and thorax.
124
What are the muscles of exhalation?
Abdominal and internal intercostals.
Abdominal muscle contraction moves inferior ribs downward and compresses the abdominal viscera.
Internal intercostal contraction pulls ribs inferiorly.
125
When would intrapleural pressure briefly exceed atmospheric pressure?
Forced exhalation. Cough.
126
Describe surface tension of alveolar fluid.
When liquid surrounds a sphere of air, surface tension produces an inwardly directed force, and this causes alveoli to assume the smallest possible diameter. During breathing, this surface tension must be overcome to expand the lungs.
127
Surface tension accounts for ___ of lung elastic recoil, which decreases the size of alveoli during exhalation.
2/3
128
Lung compliance.
Related to elasticity and surface tension.
High compliance: lungs and chest wall will expand easily.
Low compliance: lungs and chest wall will resist expansion.
129
Related to compliance, the lungs normally have...
High compliance because elastic fibres in lung tissue are easily stretched, and surfactant reduces surface tension.
130
Decreased lung compliance is a common feature of...
Pulmonary conditions that scar lung tissue, cause lung tissue to become filled with fluid, produce a deficiency in surfactant, or impede lung expansion.
131
Why would increased lung compliance occur in emphysema?
Disintegration of elastic fibres in alveolar walls. Surface area is smaller and pulmonary gas exchange is slowed.
132
Airflow =
Pressure different between the alveoli and atmosphere divided by the resistance.
133
As the lungs expand during inhalation, the bronchioles...
Enlarge because their walls are pulled outward. Larger-diameter airways have decreased resistance. Airway resistance then increases during exhalation as the diameter of bronchioles decreases.
134
Airway diameter is also regulated by the degree of...
Contraction and relaxation of smooth muscle in the walls of the airways. Signals from sympathetic ANS cause relaxation of bronchiolar smooth muscle, resulting in decreased resistance. Signals from parasympathetic ANS cause contraction of bronchiolar smooth muscle, resulting in increased resistance.
135
Eupnea.
Normal quiet breathing. Can consist of shallow, deep or combined breathing.
136
Costal breathing.
Shallow breathing. Chest breathing. Upward and outward movement of the chest due to contraction of external intercostal muscles.
137
Diaphragmatic breathing.
Deep breathing. Abdominal breathing. Outward movement of abdomen due to contraction and descent of diaphragm.
138
Tidal volume.
Volume of one breath. 500 mL.
70% of the tidal volume reaches the respiratory zone and participates in external respiration.
30% of the tidal volume remains in conducting airways of nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles.
139
Anatomic dead space.
Conducting airways with air that do not undergo respiratory exchange.
140
Inspiratory reserve volume.
Additional inhaled air after tidal volume. 3100 mL male. 1900 mL female. Even more air can be inhaled if inhalation follows forced exhalation.
141
Expiratory reserve volume.
Additional exhaled air after tidal volume. 1200mL male. 700 mL female.
142
Forced expiratory volume in one second.
Volume of air that can be exhaled from the lungs in one second with maximal effort following a maximal inhalation.
143
Residual volume.
After expiratory reserve volume is exhaled, considerable air remains in the lungs because the subatmospheric intrapleural pressure keeps the alveoli inflated and some air remains in the noncollapsible airways. 1200mL male. 1100 mL female.
144
Minimal volume.
Air remaining after intrapleural pressure rises to equal the atmospheric pressure and forces out some residual volume during thoracic cavity opening. Provides a medical and legal tool for determining whether a baby is born dead or died after birth.
145
Inspiratory capacity.
Sum of tidal volume and inspiratory reserve volume.
146
Functional residual capacity.
Sum of residual volume and expiratory reserve volume.
147
Vital capacity.
Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
148
Total lung capacity.
Sum of vital capacity and residual volume.
149
Minute ventilation.
Total volume of air inspired and expired each minute. Tidal volume multiplied by respiratory rate. 6000 mL/min.
150
Alveolar ventilation.
Volume of air per minute that reaches the respiratory zone. 4200 mL/min.
151
Which laws govern the passive diffusion of oxygen and carbon dioxide?
Dalton's Law and Henry's Law.
152
Dalton's Law.
Each gas in a mixture of gases exerts its own pressure as if no other gases were present.
153
Partial pressure.
The pressure of a specific gas in a mixture of gases.
154
Henry's Law.
The amount of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility. The higher the partial pressure of a gas over a liquid, and the higher the solubility, the more gas will stay in solution.
155
The rate of pulmonary and systemic gas exchange depends on...
1) Partial pressure difference of gases.
2) Surface area available for gas exchange.
3) Diffusion distance.
4) Molecular weight and solubility of gases.
156
Partial pressure difference of gases.
Alveolar PO2 must be higher than blood PO2 for O2 to diffuse from alveolar air into blood.
157
How does morphine affect the partial pressure difference of gases?
It slows ventilation, decreasing the amount of O2 and CO2 that can be exchanged between alveolar air and blood.
158
High altitude sickness.
With increasing altitude, the total atmospheric pressure and PO2 decrease. Inhaled air decreases and O2 diffuses into blood more slowly.
159
Any pulmonary disorder that decreases the functional surface area of the respiratory membranes decreases the...
Rate of external respiration.
160
Describe pulmonary edema and diffusion distance.
Buildup of interstitial fluid between alveoli slows the rate of gas exchange because it increases diffusion distance.
161
Molecular weight of O2 and CO2.
O2 has a lower molecular weight than CO2, but the solubility of CO2 in fluid portions of the respiratory membrane is 24x greater than that of O2, so CO2 actually diffuses faster than O2.
162
___ of inhaled O2 is dissolved in blood plasma, and remaining is bound to hemoglobin in RBCs.
1.5%
163
Oxyhemoglobin.
Reversible binding of oxygen and hemoglobin.
164
What determines the affinity of Hg for O2?
1) Acidity. As acidity increases, the affinity of Hg for O2 decreases, and O2 disassociates more readily from Hg. Bohr effect. When H+ ions bind to amino acids in Hg, they alter its structure to decrease its O2 carrying capacity.
2) Partial pressure of CO2. As PCO2 rises, Hg release more O2. Low blood pH results from high PCO2.
3) Temperature. As temperature rises, more O2 is released from Hg.
4) BPG. Substance found in RBCs. Decreases the affinity of Hg for O2.
165
What determines how much O2 binds to Hg?
Partial pressure of O2. The higher the PO2, the more O2 combines with Hg. PO2 is higher in pulmonary capillaries, and low in tissue capillaries.
166
Fetal Hg vs. adult Hg.
Fetal Hg has a higher affinity for O2 because it binds BPG less strongly. When PO2 is low, fetal Hg can carry up to 30% more O2 than adult Hg.
167
How is CO2 transported in blood?
1) Dissolved CO2. 7% of CO2 is dissolved in blood plasma, diffused into alveolar air, and is exhaled upon reaching the lungs.
2) Carbamino compounds. 23% of CO2 combines with amino groups of amino acids and proteins in blood to form carbamino compounds. In tissue capillaries, PCO2 is high which promotes formation of Hg-CO2. In pulmonary capillaries, PCO2 is low which promotes dissociation of Hg and CO2.
3) Bicarbonate ions. 70% of CO2 is transported in blood plasma as HCO3-.
168
At rest, how much O2 is used each minute by body cells?
200 mL
169
Respiratory center.
Clusters of neurons located bilaterally in the brainstem. Breathing muscles contract as a result of nerve impulses transmitted from this center, and they relax as a result of absence of nerve impulses.
Medullary respiratory center (DRG, VRG) and pontine respiratory group.
170
Medullary respiratory center.
Dorsal respiratory group: During normal breathing, neurons of DRG generate impulses to the diaphragm via phrenic nerves and to the external intercostals via intercostal nerves --> muscles contract --> inhalation. When the DRG becomes inactive after 2 seconds, the diaphragm and external intercostals relax for 3 seconds, allowing the passive recoil of the lungs and thoracic wall.
Ventral respiratory group: Pre-Botzinger complex is a cluster of neurons in VRG that is composed of pacemaker cells that set the basic rhythm of breathing. Pre-Botzinger complex provides input to the DRG to drive the rate at which DRG neurons fire APs. The remaining neurons in the VRG do not participate in normal breathing. It becomes activated when forceful breathing is required. During forceful inhalation, nerve impulses from DRG stimulate diaphragm, external intercostal muscles, and VRG neurons to send impulses to accessory muscles of inhalation. During forceful exhalation, DRG is inactive. VRG neurons involved in forced exhalation send nerve impulses to accessory muscles of exhalation.
171
Accessory muscles of exhalation.
Internal intercostals, external oblique, internal oblique, transversus abdominal, rectus abdominis.
172
Pontine respiratory group.
PRG neurons are active during inhalation and exhalation. Transmits nerve impulses to DRG. Modifies basic rhythm of breathing generated by VRG.
173
We can voluntarily alter our pattern of breathing because...
The cerebral cortex has connections with the respiratory center.
174
The ability to hold your breath is limited by...
The buildup of CO2 and H+ in the body. When these increase, the DRG neurons are strongly stimulated.
175
Nerve impulses from ___ and ___ also stimulate the respiratory center, allowing emotional stimuli to alter breathing.
Hypothalamus, limbic system.
176
How do chemoreceptors regulate breathing?
They monitor levels of CO2, H+ and O2.
177
Central chemoreceptors.
In or near the medulla oblongata. Respond to changes in H+ and PCO2 in CSF.
178
Peripheral chemoreceptors.
In aortic bodies and carotid bodies. Respond to changes in PO2, H+ and PCO2 in blood.
179
Hypercapnia.
PCO2 > 40 mmHg. Central chemoreceptors respond vigorously to the resulting increase in H+. Peripheral chemoreceptors respond to high PCO2, high H+, low O2. Central and peripheral chemoreceptors stimulate DRG to increase rate and depth of breathing.
180
Hyperventilation.
Allows inhalation of more O2 and exhalation of more CO2 until PCO2 and H+ levels are lowered to normal.
181
Hypocapnia.
PCO2 < 40 mmHg. Chemoreceptors are not stimulated. DRG neurons set their own moderate pace until CO2 accumulates and PCO2 rises to normal.
182
Even before changes in PO2, PCO2, and H+ occur, your rate and depth in breathing increase due to...
Proprioceptors when you start to exercise. Nerve impulses from proprioceptors stimulate DRG. Axon collaterals of UMNs that originate in primary motor cortex also feed excitatory impulses into DRG.
183
Hering-Breuer reflex.
Inflation reflex. Protective mechanism that prevents excessive inflation of lungs.
When baroreceptors in walls of bronchi and bronchioles become stretched during overinflation of lungs, nerve impulses are sent along vagus nerves to DRG --> inhibit DRG --> diaphragm and external intercostals relax --> further inhalation is stopped --> exhalation begins --> lungs deflate --> stretch receptors are no longer stimulated --> DRG is no longer inhibited --> inhalation begins.
In infants, this reflex functions in normal breathing.
In adults, this reflex is not activated until TD > 1500 mL.
