BIOL 320 Textbook Ch 23

List the 7 components of the respiratory system.

1. External nose. Encloses the chamber for air inspiration.

2. Nasal cavity. A cleaning, warming, and humidifying chamber for inspired air.

3. Pharynx. Serves as a common passageway for food and air.

4. Larynx. A rigid structure that helps keep the airway constantly open, or patent.

5. Trachea. Serves as an air-cleaning tube to funnel inspired air to each lung.

6. Bronchi. Tubes that direct air into the lungs.

7. Lungs. Each lung is a labyrinth of air tubes and a complex network of air sacs, called alveoli, and capillaries. The air sacs are separated by walls of connective tissue containing both collagenous and elastic fibers. Each air sac is the site of gas exchange between the air and the blood.

What are the four steps of gas exchange?

1. Pulmonary ventilation. This is what we more commonly refer to as breathing. Air moves into and out of the respiratory passages.

2. Pulmonary gas exchange. At the terminal portion of the air tubes are tiny air sacs called alveoli. O2 moves out of the alveolar air and into the blood. At the same time, CO2 diffuses out of the blood and joins the air in the alveoli.

3. Gas transport. Carbon dioxide and O2 travel in the blood to and from cells.

4. Tissue gas exchange. Gas exchange with the tissues involves exit of O2 from the blood into cells, while CO2 exits cells to enter the blood.

Explain the 5 functions of the respiratory system.

1. Regulation of blood pH. The respiratory system can alter blood pH by changing blood CO2 levels.

2. Production of chemical mediators. The lungs produce an enzyme called angiotensin-converting enzyme (ACE), which is an important component of blood pressure regulation.

3. Voice production. Air moving past the vocal folds makes sound and speech possible.

4. Olfaction. The sensation of smell occurs when airborne molecules are drawn into the nasal cavity.

5. Protection. The respiratory system provides protection against some microorganisms by preventing them from entering the body and removing them from respiratory surfaces.

Name the parts of the upper and lower respiratory tracts.

Upper Respiratory Tract — Nose and nasal cavity, pharynx, nasopharynx, oropharynx, laryngopharynx, and larynx

Lower Respiratory Tract — Trachea, bronchi, tracheobronchial tree, and alveoli

Explain how the conducting zone differs from the gas exchange zone.

All of the lower respiratory tract structures function only for pulmonary ventilation or within the conduction zone.

Gas exchange occurs only where there is contact between inspired air and the blood.

Describe the structures of the nasal cavity.

The nasal cavity is the open chamber inside the nose where air first enters the respiratory system. It begins at the anterior external openings called the nares, or nostrils.

It extends to posterior openings into the pharynx. These openings are called choanae.

Just inside each naris is a region called the vestibule. It is lined with stratified squamous epithelium.

The floor of the nasal cavity, which separates it from the oral cavity in the mouth, is called the hard palate. It is formed by the palatine process of the maxillae and the palatine bone.

The two halves of the nasal cavity is separated by a wall of tissue called the nasal septum.

On each side of the nasal cavity, there are three lateral bony ridges called conchae. They help to churn the air through the nasal cavity.

What are the five functions of the nasal cavity?

1. Serves as a passageway for air. The nasal cavity remains open even when the mouth is full of food.

2. Cleans the air. The vestibule is lined with hairs, which trap some of the large particles of dust in the air. The large surface area also helps to increase the likelihood that air will come into contact with the mucous membrane lining the cavity. The cilia on the surface of the mucous membrane sweep the mucous to be swallowed and eliminated by the stomach acid.

3. Humidifies and warms the air. Moisture is added to the air as it passes through the nasal cavity. Two major sources of moisture are (1) the mucous epithelium and (2) tears that drain into the nasal cavity through the nasolacrimal duct. The warming prevents damage to the rest of the respiratory passages.

4. Contains the olfactory epithelium. The sensory organ for smell is located in the most superior part of the nasal cavity.

5. Helps determine voice sound. The nasal cavity and paranasal sinuses are resonating chambers for speech.

Name the three regions of the pharynx. With what other structures does each part communicate?

(1) The nasopharynx, (2) the oropharynx, and (3) the laryngopharynx.

It is the common opening of both the digestive and respiratory systems. Inferiorly, the pharynx is connected to the respiratory system at the larynx and to the digestive system at the esophagus.

Name and describe the three single cartilages of the larynx. What are their functions?

1. Thyroid cartilage — the largest of the cartilages; also known as the Adam’s Apple

2. Cricoid cartilage — forms the base of the larynx; a single piece of cartilage in which the other cartilages rest

3. Epiglottis — attached to the thyroid cartilage and projects superiorly; helps divert food away from the trachea opening during swallowing

Distinguish between the vestibular and vocal folds. How are sounds of different loudness and pitch produced by the vocal ligaments?

Vestibular folds are otherwise known as false vocal cords. They contain the superior pair of ligaments that extend from the anterior surface of the arytenoid cartilages to the posterior surface of the thyroid cartilage.

The vocal cords, or true vocal cords, contain the inferior ligaments. At the junction of the vocal folds is an opening which is called the glottis.

How does the position of the arytenoid cartilages change when a person is simply breathing versus making low-pitched and high-pitched sounds?

Lateral rotation of the arytenoid cartilages moves the vocal ligaments laterally for pulmonary ventilation. Medial rotation of the arytenoid cartilages moves the vocal cords medially for speaking.

Anterior/posterior movement of the arytenoid cartilages changes the length and tension of the vocal ligaments, altering the pitch of sounds.

What are the four functions of the larynx?

1. Maintains an open passageway for air movements

2. Prevents swallowed materials from entering the larynx and lower respiratory tract

3. Produces sound for speech

4. Protects the lower respiratory tract from foreign materials

Explain the branching of the tracheobronchial tree.

The tracheobronchial tree consists of the trachea and the network of air tubes in the lungs.

The trachea divides to form a left and right main bronchus, each of which divides to form smaller and smaller bronchi.

The smaller bronchi continue getting smaller until they terminate in microscopic tubes and sacs.

Overall, approximately 16 generations of branching occur from the trachea to the smallest air tubes.

Describe the arrangement of cartilage, smooth muscle, and epithelium in the tracheobronchial tree. Explain why pulmonary ventilation becomes more difficult during an asthma attack.

The walls of each class of air passageway are supported by cartilage and smooth muscle, giving way to all smooth muscle in the smallest air passageways.

In addition, each class of air passageway is lined with a type of ciliated epithelium, which functions as a mucus-cilia escalator, trapping debris from the air and moving it to the larynx.

An asthma attack, causes severe bronchoconstriction which decreases the diameter of the airways, which increases resistance to airflow and greatly reduces air movement.

How is debris removed from the tracheobronchial tree?

Each class of air passageway is lined with a type of ciliated epithelium, which functions as a mucus-cilia escalator, trapping debris from the air and moving it to the larynx.

Name the two types of cells in the alveolar wall, and state their functions.

(1) Type I pneumocytes and (2) type II pneumocytes.

Type I pneumocytes are thin squamous epithelial cells that form 90% of the alveolar surface. Most of the gas exchange between alveolar air and the blood takes place through these cells.

Type II pneumocytes are round or cube-shaped secretory cells that produce surfactant, which makes it easier for the alveoli to expand during inspiration.

List the individual layers of the respiratory membrane.

1. A thin layer of alveolar fluid

2. The alveolar epithelium, which is a single layer of simple squamous epithelium

3. The basement membrane of the alveolar epithelium

4. A thin interstitial space

5. The base membrane of the capillary endothelium

6. The capillary endothelium, which is a single layer of simple squamous cells

Distinguish among a lung, a lung lobe, a bronchopulmonary segment, and a lobule. How are they related to the tracheobronchial tree?

The lungs are the primary organs of gas exchange.

The lung lobes are separated by deep, prominent fissures on the surface of the lung. Each lung lobe is supplied by a lobar bronchus.

The lung lobes are further subdivided into bronchopulmonary segments. Each bronchopulmonary segment is supplied by the segmental bronchi. The segments are separated from each other by connective tissue partitions, which are not visible as surface fissures.

The bronchopulmonary segments are even further subdivided into lobules by partial walls of connective tissue. Bronchioles supply each lobule.

How many lobes are in the right lung and in the left lung? Why is there a difference in the number of lobes?

The right lung has three lobes, while the left lung has two lobes. The left lung has a medial indentation called the cardiac notch. This structural arrangement provides room for the heart to lie between the lungs.

What are the two major routes of blood flow to and from the lungs? What is the function of each route?

(1) Blood flow to the alveoli and (2) blood flow to the tissues of the bronchial tree.

The major route takes deoxygenated blood to the alveoli in the lungs, where it is oxygenated.

The second route takes the oxygenated blood to the tissues of the bronchi down to the respiratory bronchioles.

Describe the lymphatic supply of the lungs.

The lungs have two lymphatic supplies: (1) the superficial lymphatic vessels and (2) the deep lymphatic vessels.

The superficial lymphatic vessels drain lymph from the superficial lung tissue and the visceral pleura.

The deep lymphatic vessels follow the bronchi. These vessels drain lymph from the bronchi and associated connective tissues.

There are no lymphatic vessels located in the walls of the alveoli. Both the superficial and deep lymphatic vessels exit the lung at the hilum.

Name the pleurae of the lungs. What is their function?

The serous membrane that covers the inner thoracic wall, the superior surface of the diaphragm, and the mediastinum is called the parietal pleura. At the hilum, the parietal pleura is continuous with the visceral pleura, which covers the surface of the lung.

They facilitate smooth breathing through the pleural fluid secretion that is housed in between the pleura.

List the muscles of inspiration, and describe their role in quiet inspiration.

There are several muscles of inspiration that act to increase the volume of the thoracic cavity. They include the (1) diaphragm, (2) external intercostals, (3) pectoralis minor, and (4) scalene muscles.

In quiet inspiration, contraction of the diaphragm causes the central tendon to move downward. This downward movement is facilitated by relaxation of the abdominal muscles, which moves the abdominal muscles out of the way.

As the depth of inspiration increases, the abdominal organs prevent the central tendon from moving inferiorly. Continued contraction of the diaphragm causes it to flatten as the lower ribs are elevated.

List the muscles of expiration, and describe their role in quiet expiration.

The muscles of expiration are the muscles that decrease thoracic volume by depressing the ribs and sternum. These are the (1) internal intercostals and (2) transverse thoracis, with the assistance from the abdominal muscles.

During quiet pulmonary ventilation, expiration is a passive process due to significant amounts of elastic tissue in the thorax wall and the lungs.

How do muscles of ventilation change during labored pulmonary ventilation?

During labored inspiration, more air moves into the lungs because all of the inspiratory muscles are active. They contract more forcefully than during quiet pulmonary ventilation, which causes a greater increase in thoracic volume.

During labored expiration, more air moves out of the lungs due to forceful contraction of the internal intercostals and the abdominal muscles. This produces a more rapid and greater decrease in thoracic volume than would be produced by the passive recoil of the thorax and lungs.

What is pulmonary ventilation?

Pulmonary ventilation is simply the movement of air into and out of the lungs.

There are two primary aspects to pulmonary ventilation: (1) actions of the muscles of ventilation and (2) air pressure gradients.

How do pressure differences and resistance affect airflow through a tube?

Air moves through tubes because of a pressure difference: Air moves from areas of higher pressure to areas of lower pressure.

The greater the resistance the lower the airflow.

What happens to the pressure within a container when the volume of the container increases? Whose law describes this relationship?

As the volume of a container increases, the pressure in that container decreases. The pressure of a gas in a container at a constant temperature follows Boyle’s Law.

Describe the process of making intra-alveolar pressure changes that occurs during quiet resting pulmonary ventilation.

The compliance of the lungs and thorax is the volume by which they increase for each unit of change in intra-alveolar pressure.

For every 1mmHg change in intra-alveolar pressure, the volume changes by 0.18 L.

Distinguish among tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume.

1. Tidal volume. The tidal volume is the normal volume of air inspired and expired with each breath. At rest, quiet pulmonary ventilation results in a tidal volume of approximately 500mL.

2. Inspiratory reserve volume. The inspiratory reserve volume is the amount of air that can be inspired forcefully after a normal inspiration (approx. 3000mL at rest).

3. Expiratory reserve volume. The expiratory reserve volume is the amount of air that can be forcefully expired after a normal expiration (approx. 1100mL at rest).

4. Residual volume. The residual volume is the volume of air still remaining in the respiratory passages and lungs after the most forceful expiration (approx. 1200mL).

Differentiate among inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity.

1. Inspiratory capacity is the tidal volume plus the inspiratory reserve volume. It is the amount of air a person can inspire maximally after a normal expiration (approx. 3500mL at rest).

2. Functional residual capacity is the expiratory reserve volume plus the residual volume. It is the amount of air remaining in the lungs at the end of a normal expiration (approx. 2300mL at rest).

3. Vital capacity is the sum of the inspiratory reserve volume, the tidal volume, and the expiratory reserve volume. It is the maximum volume of air a person can expel from the respiratory tract after a maximum inspiration (approx. 4600mL).

4. Total lung capacity is the sum of the inspiratory and expiratory reserve volumes plus the tidal volume and the residual volume (approx. 5800mL).

What is forced expiratory volume in 1 second, and why is it clinically important?

The forced expiratory volume in 1 second is the amount of air expired within the first second of the test.

A lower FEV1 measure indicated that the severity of the disease has worsened.

What is the difference between minute volume and alveolar ventilation?

The minute volume is a measure of the amount of air moved through the respiratory system per minute.

Alveolar ventilation is the measure of the volume of air available for gas exchange per minute.

Although minute volume measure the amount of air moving into and out of the respiratory system per minute, it is not a measure of the amount of air available for gas exchange.

What is compliance? What is the effect on lung expansion when compliance increases or decreases?

Compliance is a measure of the ease with which the lungs and thorax expand.

A lower-than-normal compliance means that it is harder to expand the lungs and thorax.

A higher-than-normal compliance will reduce elastic recoil, therefore making expiration less efficient.

What is dead space? Contract anatomical dead space with physiological dead space.

The remaining areas where no gas exchange occurs is called the dead space.

The anatomical dead space areas include all the structures of the upper respiratory tract, and structures of the lower respiratory tract to the terminal bronchioles. These are all of the conducting zone areas.

The physiological dead space is the combination of the anatomical dead space and the volume of any alveoli with lower than normal gas exchange.

According to Dalton’s law, what is the partial pressure of a mixture of gases? What is water vapor pressure?

The individual pressure of each gas is called the partial pressure.

Water vapor pressure is the partial pressure exerted by water molecules in a gaseous states within a gas mixture, such as air.

Why are the compositions of inspired, alveolar, and expired air different?

Three factors cause differences in the composition among alveolar air, expired air, and atmospheric air:

1. Air entering the respiratory system is humidified

2. O2 diffuses from the alveoli into the blood, while CO2 diffuses from the blood into the alveol

3. The alveolar air is only partially replaced with atmospheric air during each inspiration

According to Henry’s law, how do partial pressure and solubility of a gas affect its concentration in a liquid?

Gas molecules move from the air into a liquid, or vice versa, down their partial pressure gradients. However, the amount of gas is also dependent on how readily a gas dissolves in the liquid, which is called the solubility coefficient.

Concentration of dissolved gas = pressure of gas x solubility coefficient

What are assigned values for atmospheric pressure and for intra-alveolar pressure?

• Atmospheric pressure at sea level is approximately 760 mmHg (or 101.3 kPa).

• Intra-alveolar pressure varies during breathing but is typically around 760 mmHg at rest.

• During inhalation, intra-alveolar pressure decreases to about 758 mmHg.

• During exhalation, intra-alveolar pressure increases to about 762 mmHg.

What is lung recoil, and what two factors cause it?

Lung recoil is the tendency for the lungs to decrease in size after they are stretched.

Lung coil occurs because of (1) elastic recoil and (2) surface tension.

Elastic coil occurs because elastic fibers within the lungs and thoracic wall return to their original shape and size once the tension on them is released, just like a rubber band.

How does surfactant reduce lung recoil? What happens if the alveoli have insufficient surfactant?

Surfactant prevents collapse of the alveoli due to surface tension. Without surfactant, as hydrogen bonds would form, the walls of each alveolus would pull inwards towards each other.

Insufficient surfactant would cause the lungs to collapse.

What is pleural pressure? What happens to alveolar volume when pleural pressure decreases? What causes pleural pressure to be lower than intra-alveolar pressure?

Pleural pressure is the pressure within the pleural cavity between the parietal pleura and the visceral pleura.

As pleural pressure decreases, alveolar volume increases, intra-alveolar pressure decreases below atmospheric pressure, and air flows into the lungs.

When the thoracic wall expands during inspiration, the parietal pleura exerts an outward force on the visceral pleura covering the lungs, and the lungs expand. Pleural pressure pulls the lungs outward and is lower than intra-alveolar pressure.

How does a pneumothorax cause a lung to collapse?

The separation of the visceral and parietal pleurae increases pleural pressure— this increase in pleural pressure is called a pneumothorax.

if the visceral and parietal pleurae become separated, the lungs collapse.

During inspiration, what causes pleural pressure to decrease? What effect does this have on intra-alveolar pressure and air movement?

The decrease in pleural pressure during inspiration occurs for two reasons:

1. Changing volume affects pressure (Boyle’s law), the increased volume of the thoracic cavity causes decreased pleural pressure

2. As the thoracic cavity expands, the lungs expand because they adhere to the inner thoracic wall through the pleurae

Intra-alveolar pressure then decreases below atmospheric pressure, and air flows into the lungs.

During expiration, what causes pleural pressure to increase? What effect does this have on intra-alveolar pressure and air movement?

During expiration, pleural pressure increases because of decreased thoracic volume and decreased lung recoil.

As pleural pressure increases, alveolar volume decreases, intra0alveolar pressure increases above atmospheric pressure, and air flows out of the lungs.

Describe the four factors that affect the diffusion of gases through the respiratory membrane.

1. Partial pressure gradients for O2

2. Partial pressure gradients for CO2

3. The thickness of the respiratory membrane

4. The surface area of the respiratory membrane

Does O2 or CO2 diffuse more easily through the respiratory membrane?

CO2.

What effect do alveolar ventilation and pulmonary capillary perfusion have on gas exchange?

Describe the partial pressure of O2 and CO2 in the alveoli, lung capillaries, tissue capillaries, and tissues.

How do these pressures account for the movement of O2 and CO2 between air and blood and between blood and tissues?

Name the two ways O2 is transported in the blood, and state the percentage of total O2 transport for which each method is responsible.

Once O2 diffuse through the respiratory membrane into the blood, it is transported to all the cells of the body approximately 98.5% of O2 is transported reversibly bound to hemoglobin within red blood cells and the remaining 1.5% is dissolved in the plasma cells use O2 in aerobic cellular respiration to synthesize ATP.

How does the oxygen-hemoglobin dissociation curve explain the uptake of O2 in the lungs and the release of O2 in tissues?

What is the Bohr effect? How is it related to blood CO2?

The Bohr effect is the shift of oxygen-hemoglobin dissociation curve to the right or left because of changes in blood pH.

Why is it advantageous for the oxygen-hemoglobin dissociation curve to shift to the left in the lungs and to the right in tissues?

How does temperature affect O2’s tendency to bind to hemoglobin?

How does BPG affect the release of O2 from hemoglobin?

Why is fetal hemoglobin’s affinity for O2 greater than that of maternal hemoglobin?

How does the lowering of HCO3- concentrations inside red blood cells affect CO2 transport?

What is chloride shift, and what does it accomplish?

Name three effects produced by H+ binding to hemoglobin.

What is Haldane effect?

What effect does blood CO2 level have on blood pH?

Define the anatomical shunt and the physiological shunt of the respiratory system.

What are the effects of gravity and alveolar PO2 on blood flow in the lung?

Name the three respiratory groups, and describe their main functions.

How is rhythmic pulmonary ventilation generated?

Explain how the cerebral cortex and limbic system can exert control over pulmonary ventilation. What is apnea?

Where are central chemoreceptors and peripheral chemoreceptors? Which are most important for regulating blood pH and CO2 level? How does this change during intense exercise?

Define hypercapnia and hypocapnia.

How does a decrease in blood pH affect respiratory rate? How does a decrease in CO2 affect respiratory rate?

What is hypoxia? Why must arterial PO2 change significantly before it affects respiratory rate?

What mechanisms regulate pulmonary ventilation at the onset of exercise and then during exercise? What is the anaerobic threshold?

Describe the Hering-Breuer reflex and its function.