1
Q
Respiration
A
The process of supplying the body with O2 and removing CO2.
2
Q
What are the three basic steps of respiration? Describe them:
A
- Pulmonary ventilation AKA breathing: the inhalation (inflow) and exhalation (outflow) of air and involves the exchange of air between the atmosphere and the alveoli of the lungs. Inhalation permits O2 to enter the lungs and exhalation permits CO2 to leave the lungs.
- External (pulmonary) respiration: the exchange of gases between the alveoli of the lungs and the blood in pulmonary capillaries across the respiratory membrane. In this process, pulmonary capillary blood gains O2 and loses CO2.
- Internal (tissue) respiration: the exchange of gases between blood in systemic capillaries and tissue cells. In this step the blood loses O2 and gains CO2.
3
Q
Cellular respiration
A
Metabolic reactions within cells that consume O2 and give off CO2 during the production of ATP.
4
Q
Respiratory system
A
Consists of the nose, pharynx (throat), larynx (voice box), trachea (windpipe), bronchi, and lungs.
5
Q
What two ways can the parts of the respiratory system be classified?
A
- Structure
- Function
6
Q
Structurally, the respiratory system consists of two parts. What are they? Describe them:
A
- Upper respiratory system: includes the nose, nasal cavity, pharynx, and associated structures.
- Lower respiratory system: includes the larynx, trachea, bronchi, and lungs.
7
Q
Functionally, the respiratory system consists of two parts. What are they? Describe them:
A
- Conducting zone: consists of a series of interconnecting cavities and tubes both outside and within the lungs. These include the nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles; their function is to filter, warm, and moisten air and conduct it into the lungs.
- Respiratory zone: consists of tubes and tissues within the lungs where gas exchange occurs. These include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli and are the main sites of gas exchange between air and blood.
8
Q
What are the three functions of the respiratory system?
A
- Provides for gas exchange: intake of O2 for delivery to body cells and removal of CO2 produced by body cells.
- Helps regulate blood pH.
- Contains receptors for sense of smell, filters inspired air, produces vocal sounds (phonation), and excretes small amounts of water and heat.
9
Q
Nose
A
Is a specialized organ at the entrance of the respiratory system.
10
Q
What two portions does the nose consist of?
A
- External nose
- Internal nose
11
Q
Bony framework
A
Formed by the frontal bone, nasal bones, and maxillae.
12
Q
Cartilaginous framework
A
Formed by the septal nasal cartilage, lateral nasal cartilages, and alar cartilages.
13
Q
Septal nasal cartilage
A
Forms the anterior portion of the nasal septum.
14
Q
Lateral nasal cartilages
A
Inferior to the nasal bones.
15
Q
Alar cartilages
A
Form a portion of the walls of the nostrils.
16
Q
External nares (nostrils)
A
Two openings on the undersurface of the external nose.
17
Q
What are the three functions of the inferior 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
Resonance
A
Prolonging, amplifying, or modifying a sound by vibration.
19
Q
Nasal cavity (internal nose)
A
A large space in the anterior aspect of the skull that lies inferior to the nasal bone and superior to the oral cavity; is lined with muscle and mucous membrane.
20
Q
Nasal septum
A
Divides the nasal cavity into right and left sides. The anterior portion of the nasal septum consists primarily of hyaline cartilage; the remainder is formed by the vomer and the perpendicular plate of the ethmoid, maxillae, and palatine bones.
21
Q
Internal nares (choanae)
A
Two openings which the nasal cavity communicates with the pharynx through.
22
Q
Paranasal sinuses
A
Drain mucus. Also serve as resonating chambers for sound as we speak or sing.
23
Q
Nasolacrimal ducts
A
Drain tears.
24
Q
What two regions can the nasal cavity be divided into? Describe the epithelium, cilia, goblet cells, and special features for these regions:
A
- Respiratory region:
Epithelim: ciliated pseudostratified columnar
Cilia: yes.
Goblet cells: yes.
Special features: contains conchae and meatuses - Olfactory region:
Epithelim: olfactory epithelium (olfactory receptors).
Cilia: yes.
Goblet cells: no.
Special features: functions in olfaction.
25
Respiratory epithelium
Found within the respiratory region. Lined with ciliated pseudostratified columnar epithelium with numerous goblet cells.
26
Describe the epithelium, cilia, goblet cells, and special features for the nasal vestibules:
Epithelium: nonkeratinized stratified squamous.
Cilia: no.
Goblet cells: no.
Special features: contains numerous hairs.
27
The superior, middle, and inferior ______ subdivide each side of the nasal cavity into a series of groove-like air passageways called the superior, middle, and inferior ______.
Nasal conchae; meatuses
28
What does the arrangement of nasal conchae and meatuses do?
Increases surface area in the internal nose and prevents dehydration by trapping water droplets during exhalation.
29
Olfactory epithelium
Found within the olfactory region. Made up of the olfactory receptor cells, supporting cells, and basal cells. Contain cilia but no goblet cells.
30
Pharynx
AKA throat; functions as a passageway for air and food, provides a resonating chamber for speech sounds, and houses the tonsils, which participate in immunological reactions against foreign invaders.
31
What three anatomical regions can the pharynx be divided into?
1. Nasopharynx
2. Oropharynx
3. Laryngopharynx
32
Describe the epithelium, cilia, goblet cells, and special features for the nasopharynx:
Epithelium: ciliated pseudostratified columnar.
Cilia: yes.
Goblet cells: yes.
Special features: passageway for air; contains internal nares, openings for auditory (pharyngotympanic) tubes (eustachian tubes), and pharyngeal tonsil.
33
Soft palate
Forms the posterior portion of the roof of the mouth. Is an arch-shaped muscular partition between the nasopharynx and oropharynx that is lined by mucous membrane.
34
Describe the epithelium, cilia, goblet cells, and special features for the oropharynx:
Epithelium: nonkeratinized stratified squamous.
Cilia: no.
Goblet cells: no.
Special features: passageway for both air and food and drink; contains opening from mouth (fauces). Contain the palatine and lingual tonsils.
35
Describe the epithelium, cilia, goblet cells, and special features for the laryngopharynx (hypopharynx):
Epithelium: nonkeratinized stratified squamous.
Cilia: no.
Goblet cells: no.
Special features: passageway for both air and food and drink.
36
Describe the epithelium, cilia, goblet cells, and special features for the larynx (voice box):
Epithelium: nonkeratinized stratified squamous above the vocal folds; ciliated pseudostratified columnar below the vocal folds.
Cilia: no above folds; yes below folds.
Goblet cells: no above folds; yes below folds.
Special features: passageway for air; contains vocal folds for voice production.
37
How many pieces of cartilage is the wall of the larynx composed of? What are they?
9; thyroid cartilage (single), epiglottis (single), cricoid cartilage (single), arytenoid cartilages (pairs), cuneiform
cartilages (pairs), and corniculate cartilages (pairs).
38
Which of the paired cartilages is most important? Why?
The arytenoid cartilages because they influence changes in position and tension of the vocal folds (true vocal cords for speech).
39
Cavity of the larynx
The space that extends from the entrance into the larynx down to the inferior border of the cricoid cartilage.
40
Laryngeal vestibule
The portion of the cavity of the larynx above the vestibular folds (false vocal cords).
41
Infraglottic cavity
The portion of the cavity of the larynx below the vocal folds.
42
Thyroid cartilage (Adam's apple)
Consists of two fused plates of hyaline cartilage that form the anterior wall of the larynx and give it a triangular shape. Is present in both males and females but is usually larger in males due to the influence of male sex hormones on its growth during puberty.
43
Epiglottis
A large, leaf-shaped piece of elastic cartilage that is covered with epithelium. The “stem” of the epiglottis is the tapered inferior portion that is attached to the anterior rim of the thyroid cartilage. The broad superior “leaf” portion of the epiglottis is unattached and is free to move up and down like a trap door.
44
Glottis
Consists of a pair of folds of mucous membrane, the vocal folds (true vocal cords) in the larynx, and the rima glottidis (space between them).
45
During swallowing, the ______ and ______ rise. Elevation of the ______ widens it to receive food or drink; elevation of the ______ causes the ______ to move down and form a lid over the ______, closing it off.
The closing of the ______ in this way during swallowing routes liquids and foods into the esophagus and keeps them out of the ______ and airways. When small particles of dust, smoke, food, or liquids pass into the ______, a cough reflex occurs, usually expelling the material.
Pharynx; larynx; pharynx; larynx; epiglottis; glottis
Larynx; larynx; larynx
46
Cricoid cartilage
A ring of hyaline cartilage that forms the inferior wall of the larynx.
47
Arytenoid cartilages
Triangular pieces of mostly hyaline cartilage that are located at the posterior, superior border of the cricoid cartilage.
48
Corniculate cartilages
Horn-shaped pieces of elastic cartilage that are located at the apex of each arytenoid cartilage.
49
What do the cilia in the upper respiratory tract do?
Move mucus and trapped particles down toward the pharynx (While the cilia in the lower respiratory tract move them up toward the pharynx).
50
The mucous membrane of the larynx forms two pairs of folds. What are they? What are there functions?
1. Vestibular folds (false vocal cords): superior pair. Function in holding the breath against pressure in the thoracic cavity.
2. Vocal folds (true vocal cords): inferior pair. Principal structures of voice production.
51
Rima vestibuli
The space between the vestibular folds.
52
Laryngeal ventricle
A lateral expansion of the middle portion of the laryngeal cavity inferior to the vestibular folds and superior to the vocal folds.
53
Pitch
Controlled by the tension on the vocal folds. If they are pulled taut by the muscles, they vibrate more rapidly, and a higher pitch results. If muscle tension is decreased, they vibrate more slowly, and a lower pitch results. Due to the influence of androgens, vocal folds are usually thicker and longer in males than in females, and therefore they vibrate more slowly. This is why a man’s voice generally has a lower range of pitch than that of a woman.
54
Sound
Originates from the vibration of the vocal folds, but other structures are necessary for converting the sound into recognizable speech. The pharynx, mouth, nasal cavity, and paranasal sinuses all act as resonating chambers that give the voice its human and individual quality. We produce the vowel sounds by constricting and relaxing the muscles in the wall of the pharynx. Muscles of the face, tongue, and lips help us enunciate words.
55
Describe the epithelium, cilia, goblet cells, and special features for the trachea (windpipe):
Epithelium: ciliated pseudostratified columnar.
Cilia: yes.
Goblet cells: yes.
Special features: passageway for air; contains C-shaped rings of cartilage to keep trachea open.
56
What are the four layers of the tracheal wall, from deep to superficial?
1. Mucosa
2. Submucosa
3. Hyaline cartilage
4. Adventitia
57
Fibromuscular membrane
Spans the open part of each C-shaped cartilage ring that faces posteriorly towards the esophagus. Contains trachealis muscle and elastic connective tissue.
58
Trachealis muscle
Transverse smooth muscle fibers that, with the help of elastic connective tissue, allow that diameter of the trachea to change subtly during inhalation and exhalation, which is important in maintaining efficient airflow.
59
At the superior border of the fifth thoracic vertebra, the trachea divides into two bronchus. What are they? Describe them:
1. Right main (primary) bronchus: goes into the right lung; more vertical, shorter, and wider than the left, so an aspirated object is more likely to enter and lodge in the right main bronchus than the left.
2. Left main (primary) bronchus: goes into the left lung.
60
Describe the epithelium, cilia, goblet cells, and special features for the main bronchi:
Epithelium: ciliated pseudostratified columnar.
Cilia: yes.
Goblet cells: yes.
Special features: passageway for air; contain C-shaped rings of cartilage to maintain patency.
61
Carina
Internal ridge where the trachea divides into right and left main bronchi.
62
Describe the epithelium, cilia, goblet cells, and special features for the lobar bronchi:
Epithelium: ciliated pseudostratified columnar.
Cilia: yes.
Goblet cells: yes.
Special features: passageway for air; contain plates of cartilage to maintain patency.
63
Describe the epithelium, cilia, goblet cells, and special features for the larger bronchioles:
Epithelium: ciliated simple columnar.
Cilia: yes.
Goblet cells: yes.
Special features: passageway for air; contain more smooth muscle than in the bronchi.
64
Describe the epithelium, cilia, goblet cells, and special features for the smaller bronchioles:
Epithelium: ciliated simple columnar.
Cilia: yes.
Goblet cells: no.
Special features: passageway for air; contain more smooth muscle than in the larger bronchioles.
65
Describe the epithelium, cilia, goblet cells, and special features for the terminal bronchioles:
Epithelium: nonciliated simple columnar.
Cilia: no.
Goblet cells: no.
Special features: passageway for air; contain more smooth muscle than in the smaller bronchioles. Contain club (Clara) cells
66
Club (Clara) cells
Found in terminal bronchioles. May protect against harmful effects of inhaled toxins and carcinogens, produce surfactant, and function as stem cells (reserve cells), which give rise to various cells of the epithelium.
67
Describe the branching of airways from the trachea (bronchial tree)
Trachea -> main bronchi -> lobar bronchi -> segmental bronchi -> bronchioles -> terminal bronchioles
68
As the branching becomes more extensive in the bronchial tree,
several structural changes may be noted. What are the main three?
1. Mucous membrane in the bronchial tree
2. Plates of cartilage
3. Amount of smooth muscle
69
Lungs
Paired cone-shaped organs in the thoracic cavity. They are separated from each other by the heart and other structures of the mediastinum.
70
Pleural membrane (pleura)
Double-layered serous membrane that encloses and protects each lung.
71
Parietal pleura
Superficial layer; lines the wall of the thoracic cavity.
72
Visceral layer
Deep layer; covers the lungs themselves.
73
Pleural cavity
Small space between the visceral and parietal pleurae, which contains a small amount of lubricating fluid secreted by the membranes. Separate pleural cavities surround the left and right lungs.
74
Pleural fluid
Reduces friction between the membranes and allows them to slide easily over one another during breathing. Also causes the membranes to adhere to one another.
75
Base (of the lungs)
The broad inferior portion of the lung. Is concave and fits over the convex area of the diaphragm.
76
Apex (of the lungs)
The narrow superior portion of the lung.
77
Costal surface
The surface of the lung lying against the ribs. Matches the rounded curvature of the ribs.
78
Mediastinal (medial) surface
Contains the hilum.
79
Hilum
A region in each lung through which bronchi, pulmonary blood vessels, lymphatic vessels (can drain pleural cavity), and nerves enter and exit.
80
Root
The hilum and its contents.
81
Cardiac notch
A concavity within the left lung where the apex of the heart lies.
82
Fissures
Divide each lung into sections called lobes.
83
Identify where the oblique fissure, horizontal fissure, superior lobe, inferior lobe, and middle lobe are:
84
Each lobe receives its own lobar bronchus. Thus, the right main bronchus gives rise to three lobar bronchi called the ______, ______, and ______ lobar bronchi, and the left main bronchus gives rise to ______ and ______ lobar bronchi.
Within the lung, the lobar bronchi give rise to the segmental bronchi, which are constant in both origin and distribution - there are __ segmental bronchi in each lung.
Superior; middle; inferior; superior; inferior; 10
85
Bronchopulmonary segment
The portion of lung tissue that each segmental bronchus supplies
86
Lobules
Small compartments within each bronchopulmonary segment of the lungs. Wrapped in elastic connective tissue and contains a lymphatic vessel (can drain pleural cavity), an arteriole, a venule, and a branch from a terminal bronchiole
87
Respirator bronchioles
Microscopic branches that terminal bronchioles and lobules subdivide into.
88
Alveolar sac
The terminal dilation of an alveolar duct. Is analogous to a cluster of grapes. Each alveolar sac is composed of outpouchings called alveoli, analogous to individual grapes.
89
What two types of alveolar epithelial cells does the wall of each alveolus consist of? Describe them:
1. Type I alveolar cells (squamous pulmonary epithelial cells): are more numerous and are simple squamous epithelial cells that form a nearly continuous lining of the alveolar wall. Main sites of gas exchange.
2. Type II alveolar cells (septal cells): are fewer in number and are found between type I alveolar cells. Are rounded or cuboidal epithelial cells with free surfaces containing microvilli. Secrete alveolar fluid.
90
Alveolar fluid
Keeps the surface between the cells and the air moist. Made of surfacant.
91
Surfactant
A complex mixture of phospholipids and lipoproteins. Decreases surface tension.
92
Alveolar macrophages (dust cells)
Present in the alveolar wall; phagocytes that remove fine dust particles and other debris from the alveolar spaces.
93
What four layers does the respiratory membrane consists of?
1. A layer of type I and type II alveolar cells and associated alveolar macrophages that constitutes 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
94
What branches are apart of the conducting zone (beginning to end)
Trachea -> main bronchi -> lobar and segmental bronchi -> bronchioles and terminal bronchioles
95
What branches are apart of the respiratory zone (beginning to end)
Respiratory bronchioles -> alveolar ducts -> alveolar sacs
96
Describe the epithelium, cilia, goblet cells, and special features for the respiratory bronchioles:
Epithelium: simple cuboidal to simple squamous.
Cilia: no.
Goblet cells: no.
Special features: passageway for air; gas exchange.
97
Describe the epithelium, cilia, goblet cells, and special features for the alveolar ducts:
Epithelium: simple squamous.
Cilia: no.
Goblet cells: no.
Special features: passageway for air; gas exchange; produce surfactant.
98
Describe the epithelium, cilia, goblet cells, and special features for the alveoli:
Epithelium: simple squamous.
Cilia: no.
Goblet cells: no.
Special features: passageway for air; gas exchange; produce surfactant to maintain patency.
99
List the microscopic airway order (beginning to end)
Respirator bronchioles -> alveolar ducts -> alveolar sacs -> alveoli
100
Ventilation-perfusion coupling
Phenomenon in which vasoconstriction of pulmonary blood vessels in response to hypoxia (low O2 levels) diverts pulmonary blood from poorly ventilated areas of the lungs to well ventilated regions for more efficient gas exchange.
101
Pulmonary ventilation (breathing)
The flow of air into and out of the lungs. Air flows between the atmosphere and the alveoli of the lungs because of alternating pressure differences created by contraction and relaxation of respiratory muscles. The rate of airflow and the amount of effort needed for breathing are also influenced by alveolar surface tension, compliance of the lungs, and airway resistance.
102
Inhalation (inspiration)
Breathing in. During inhalation, the diaphragm contracts, the chest expands, the lungs are pulled outward, and alveolar pressure decreases.
103
Boyle's law
Law sates that whenever there is an increase in the pressure, there will be a direct decrease in the volume; whenever there is an increase in volume, there will be a decrease in pressure.
104
What is the most important muscle of inhalation?
Diaphragm
105
What are the next most important muscles of inhalation?
External intercostals
106
Intrapleural pressure
The pressure within the pleural cavity. Always a negative pressure (lower than atmospheric pressure), so essentially functions as a vacuum. ~756mmHg at rest.
107
Alveolar (intrapulmonic) pressure
The pressure of air within the alveoli of the lungs. ~760mmHg at rest.
108
Atmospheric pressure
~760mmHg.
109
Exhalation (expiration)
Breathing out. During exhalation, the diaphragm relaxes, the lungs recoil inward, and alveolar pressure increases, forcing air out of the lungs. Results from elastic recoil of the chest wall and lungs.
110
What two inwardly directed forces contribute to elastic recoil:
1. The recoil of elastic fibers that were stretched during inhalation.
2. The inward pull of surface tension due to the film of intrapleural fluid between the visceral and parietal pleurae.
111
In addition to air pressure differences, there are three other factors that affect the rate of airflow and the ease of pulmonary ventilation. What are they?
1. Surface tension of the alveolar fluid
2. Compliance of the lungs
3. Airway resistance
112
Surface tension
A force exerted by the thin layer of alveolar fluid that coats the luminal surface of alveoli. Produces an inwardly directed force.
113
Compliance
Refers to how much effort is required to stretch the lungs and chest wall. High compliance means that the lungs and chest wall expand easily; low compliance means that they resist expansion.
114
In the lungs, compliance is related to two principal factors. What are they?
Elasticity (amount of resistance) and surface tension
115
Eupnea
The normal pattern of quiet breathing.
116
Costal breathing
A pattern of shallow (chest) breathing that consists of an upward and outward movement of the chest due to contraction of the external intercostal muscles.
117
Diaphragmatic breathing
A pattern of deep (abdominal) breathing that consists of the outward movement of the abdomen due to the contraction and descent of the diaphragm.
118
Coughing
A long-drawn and deep inhalation followed by a complete closure of the rima glottidis, which results in a strong
exhalation that suddenly pushes the rima glottidis open and sends a blast of air through the upper respiratory
passages. Stimulus for this reflex act may be a foreign body lodged in the larynx, trachea, or epiglottis.
119
Sneezing
Spasmodic contraction of muscles of exhalation that forcefully expels air through the nose and mouth. Stimulus may be an irritation of the nasal mucosa.
120
Sighing
A long-drawn and deep inhalation immediately followed by a shorter but forceful exhalation.
121
Yawning
A deep inhalation through the widely opened mouth producing an exaggerated depression of the mandible. It may be stimulated by drowsiness, or someone else’s yawning, but the precise cause is unknown.
122
Sobbing
A series of convulsive inhalations followed by a single prolonged exhalation. The rima glottidis closes earlier than normal after each inhalation so only a little air enters the lungs with each inhalation.
123
Crying
An inhalation followed by many short convulsive exhalations, during which the rima glottidis remains open and the
vocal folds vibrate; accompanied by characteristic facial expressions and tears.
124
Laughing
The same basic movements as crying, but the rhythm of the movements and the facial expressions usually differ from those of crying. Laughing and crying are sometimes indistinguishable.
125
Hiccupping
Spasmodic contraction of the diaphragm followed by a spasmodic closure of the rima glottidis, which produces a sharp sound on inhalation. Stimulus is usually irritation of the sensory nerve endings of the gastrointestinal tract.
126
Valsalva maneuver
Forced exhalation against a closed rima glottidis as may occur during periods of straining while defecating.
127
Pressurizing the middle ear
The nose and mouth are held closed and air from the lungs is forced through the auditory tube into the middle ear. Employed by those snorkeling or scuba diving during descent to equalize the pressure of the middle ear with that of the external environment.
128
The amount of air moving into and out of the lungs can be classified into two types. What are they? Describe them:
1. Lung volumes: can be measured directly using a spirometer (respirometer) (apparatus used to measure volumes and capacities; the record is called a spirogram).
2. Lungs capacities: combinations of different lung volumes.
129
Tidal volume
The volume of one breath. Varies considerably from one person to another and in the same person at different times. The average is 500 mL. In a typical adult, about 70% of the tidal volume (350mL) actually reaches the respiratory zone of the respiratory system and participates in external respiration. The other 30% (150mL) remains in the conducting airways.
130
Anatomic (respiratory) dead space
The conducting airways with air that does not undergo respiratory exchange.
131
Inspiratory reserve volume (IRV)
Additional inhaled air. The average is 3100mL in males and 1900mL in females.
132
Expiratory reserve volume (ERV)
Additional exhaled air. The average is 1200 mL in males and 700 mL in females.
133
Forced expiratory volume in 1 second (FEV1)
The volume of air that can be exhaled from the lungs in 1 second with maximal effort following a maximal inhalation.
134
Residual volume (RV)
The volume of air remaining in the lungs after the expiratory reserve volume is exhaled. Is due to the subatmospheric intrapleural pressure keeping the alveoli slightly inflated, and some air remaining in the noncollapsible airways. The average is 1200mL in males and 1100mL in females.
135
Minimal volume
The air remaining when the thoracic cavity is opened, and the intrapleural pressure rises to equal the atmospheric pressure and forces out some of the residual volume.
136
Inspiratory capacity (IC)
The sum of tidal volume and inspiratory reserve volume (500 mL + 3100 mL = 3600 mL in males and 500 mL + 1900 mL = 2400 mL in females).
137
Functional residual capacity (FRC)
The sum of residual volume and expiratory reserve volume (1200 mL + 1200 mL = 2400 mL in males and 1100 mL + 700 mL = 1800 mL in females).
138
Vital capacity (VC)
The sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume (4800 mL in males and 3100 mL in females).
139
Total lung capacity (TLC)
The sum of vital capacity and residual volume (4800 mL + 1200 mL = 6000 mL in males and 3100 mL + 1100 mL = 4200 mL in females).
140
Minute ventilation (V)
The total volume of air inspired and expired each minute. Equals tidal volume multiplied by respiratory rate. In a typical adult at rest, minute ventilation is about 6000 mL/min (V = 12 breaths per minute × 500 mL = 6000 mL/min).
141
Alveolar ventilation (VA)
The volume of air per minute that actually reaches the respiratory zone (350 mL). Alveolar ventilation is typically about 4200 mL/min (VA = 12 breaths per minute × 350 mL = 4200 mL/min).
142
Dalton’s law
According to this law, each gas in a mixture of gases exerts its own pressure as if no other gases were present.
143
Partial pressure (Px)
The pressure of a specific gas in a mixture.
144
Henry’s law
According to this law, the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its
solubility.
145
Decompression sickness (the bends)
If a diver comes to the surface slowly, the dissolved nitrogen can be eliminated by exhaling it. However, if the ascent is too rapid, nitrogen comes out of solution too quickly and forms gas bubbles in the tissues. The effects of decompression sickness typically result from bubbles in nervous tissue and can be mild or severe, depending on the number of bubbles formed. Symptoms include joint pain, especially in the arms and legs, dizziness, shortness of breath, extreme fatigue, paralysis, and unconsciousness.
146
What four factors does the rate of pulmonary and systemic gas exchange depend on?
1. Partial pressure difference of the gases.
2. Surface area available for gas exchange.
3. Diffusion distance.
4. Molecular weight and solubility of the gases.
147
High altitude sickness
Caused by a lower level of oxygen in the blood. Common signs and symptoms include shortness of breath, headache, fatigue, insomnia, nausea, and dizziness.
148
Oxygen does not dissolve easily in water, so only about 1.5% of inhaled O2 is dissolved in blood plasma, which is mostly water. What happens to the other 98.5% of blood O2?
It is bound to hemoglobin in red blood cells (RBCs). Gets trapped inside the RBCs, so only the dissolved O2 (1.5%) can diffuse out of tissue capillaries into tissue cells.
149
Oxyhemoglobin
Formed by the binding of oxygen and hemoglobin. Reaction is easily reversible.
150
The most important factor that determines how much O2 binds to hemoglobin is the PO2; the higher the PO2, the more O2 combines with Hb. When reduced hemoglobin (Hb) is completely converted to oxyhemoglobin (Hb–O2), the hemoglobin is said to be ______; when hemoglobin consists of a mixture of Hb and Hb–O2, it is ______. The ______ expresses the average saturation of hemoglobin with oxygen. For instance, if each hemoglobin molecule has bound two O2 molecules, then the hemoglobin is 50% saturated because each Hb can bind a maximum of four O2.
Fully saturated; partially saturated; percent saturation of hemoglobin
151
Affinity
Tightness with which hemoglobin binds O2.
152
What four factors affect the affinity of hemoglobin for O2?
1. Acidity (pH)
2. Partial pressure of carbon dioxide
3. Temerature
4. BPG
153
Bohr effect (BOR)
When pH decreases, the entire oxygen–hemoglobin dissociation curve shifts to the right; at any given PO2, Hb is less saturated with O2. The Bohr effect works both ways: An increase in H+ in blood causes O2 to unload from hemoglobin, and the binding of O2 to hemoglobin causes unloading of H+ from hemoglobin. The explanation for the Bohr effect is that hemoglobin can act as a buffer for hydrogen ions (H+). But when H+ ions bind to amino acids in hemoglobin, they alter its structure slightly, decreasing its oxygen-carrying capacity. Thus, lowered pH drives O2 off hemoglobin, making more O2 available for tissue cells. By contrast, elevated pH increases the affinity of hemoglobin for O2 and shifts the oxygen–hemoglobin dissociation curve to the left.
A shift right from normal curve. Involves an increase in acidity (decrease in pH), increase in CO2, increase in BPG, increase in temperature, and decrease in affinity for O2 (for Hb).
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Carbonic anhydrase (CA)
An enzyme in red blood cells (RBCs) that catalyzes the reaction of CO2 temporarily converting into carbonic acid (H2CO3).
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2,3-bisphosphoglycerate (BPG)
A substance found in red blood cells (RBCs) that decreases affinity of hemoglobin for O2, and thus helps unload O2 from hemoglobin.
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How does Fetal hemoglobin (Hb-F) differ from adult hemoglobin (Hb-A)?
Differs in structure and in its affinity for O2. Hb-F has a higher affinity for O2 because it binds BPG less strongly. Thus, when PO2 is low, Hb-F can carry up to 30% more O2 than maternal Hb-A. As the maternal blood enters the placenta, O2 is readily transferred to fetal blood. This is very important because the O2 saturation in maternal blood in the placenta is quite low, and the fetus might suffer hypoxia were it not for the greater affinity of fetal hemoglobin for O2.
157
What three main forms does CO2 get transported in the blood?
1. Dissolved CO2 (smallest percentage transported this way)
2. Carbamino compounds
3. Bicarbonate ions (greatest percentage transported this way)
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Carbaminohemoglobin (Hb–CO2)
Hemoglobin that has bound CO2.
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Chloride shift
The exchange of negative ions, which maintains the electrical balance between blood plasma and RBC cytosol.
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Haldane effect
The lower the amount of oxyhemoglobin (Hb–O2), the higher the CO2-carrying capacity of the blood.
A shift left from normal curve. Involves an decrease in acidity (increase in pH), decrease in CO2, decrease in BPG, decrease in temperature, and increase in affinity for O2 (for Hb).
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Respiratory center
Widely dispersed group of neurons located bilaterally in the brain stem that send nerve impulses to alter the size of the thorax.
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What two principal areas can the respiratory center be divided into? Where are they located?
1. Medullary respiratory center in the medulla oblongata
2. Pontine respiratory group in the pons
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What two collections of neurons is the medullary respiratory center made up of?
1. Dorsal respiratory group (DRG): triggers inspiration.
2. Ventral respiratory group (VRG): triggers inspiration and expiration.
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During normal quiet breathing, the ______ is inactive; during forceful breathing, the ______ activates the ______.
Ventral respiratory group; dorsal respiratory group; ventral respiratory group
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Pre Bötzinger complex
Believed to be important in the generation of the rhythm of breathing.
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Chemoreceptors
Sensory neurons that are responsive to chemicals. Monitor levels of CO2, H+, and O2 and provide input to the respiratory center.
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Chemoreceptors can be found in two different locations of the respiratory system. What are they? Describe them:
1. Central chemoreceptors: located in or near the medulla oblongata in the central nervous system. They respond to changes in H+ concentration or PCO2, or both, in cerebrospinal fluid.
2. Peripheral chemoreceptors: located in the aortic bodies and in the carotid bodies. These chemoreceptors are part of the peripheral nervous system and are sensitive to changes in PO2, H+, and PCO2 in the blood.
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Aortic bodies
Clusters of chemoreceptors located in the wall of the arch of the aorta.
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Carotid bodies
Oval nodules in the wall of the left and right common carotid arteries where they divide into the internal and external carotid arteries. Clusters of chemoreceptors located here.
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Hypercapnia (hypercarbia)
Increase in PCO2 above 40mmHg.
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Hyperventilation
Rapid and deep breathing. Allows the inhalation of more O2 and exhalation of more CO2 until PCO2 and H+ are lowered to normal.
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Hypocapnia (hypocarbia)
Decrease in PCO2 below 40mmHg.
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Baroreceptors (stretch receptors)
Located in the walls of bronchi and bronchioles.
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Inflation reflex (Hering-Breuer reflex)
When baroreceptors become stretched during overinflation of the lungs, nerve impulses are sent along the vagus (X) nerves to the dorsal respiratory group (DRG) in the medullary respiratory center. In response, the DRG is inhibited and the diaphragm and external intercostals relax. As a result, further inhalation is stopped and exhalation begins. As air leaves the lungs during exhalation, the lungs deflate and the baroreceptors are no longer stimulated. Thus, the DRG is no longer inhibited, and a new inhalation begins. In adults, this reflex is a protective mechanism that prevents excessive inflation of the lungs.
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What six other factors contribute to the regulation of breathing?
1. Limbic system stimulation
2. Temperature
3. Pain
4. Stretching the anal sphincter muscle
5. Irritation of airways
6. Blood pressure
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Apnea
Absence of breathing.
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What are eight stimuli that increase breathing rate and depth, and eight stimuli that decrease breathing rate and depth?
BIOL 235 Midterm 3
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