AP Chapter 21: Respiratory System

Learning Outcomes

list the airway structures in order, from nares to alveoli

Nares, Nasal Cavity, Nasopharynx, Oropharynx, Laryngopharynx, Larynx, Trachea, Primary bronchus, Secondary bronchus, Tertiary bronchus, Bronchioles, terminal bronchioles, respiratory bronchioles, alveolar duct, alveolar sac

differentiate the upper versus lower respiratory tract and the conducting zone versus the respiratory zone

Upper respiratory tract = Nasal cavity to larynx

Lower respiratory tract = trachea to alveoli

Conducting zone = Where air passes through (nasal cavity to bronchioles)

Respiratory zone = where gas is exchanged (Alveoli)

describe the function of each portion of the respiratory tract

Nose/Nasal cavity = warm and filter inhaled air

Pharynx = warms and filters air

Larynx = keeps food and liquids out of the respiratory tract, sound production (vocal cords)

Trachea = delivers air to lower respiratory tract

Bronchi = Control air flow into bronchioles and alveoli to FILTER only oxygen (passages get smaller and smaller)

Bronchioles = Distribute air to alveoli for gas exchange

Alveoli = Gas exchange to diffuse into the blood

describe the structure of the alveolus, and specifically the respiratory membrane

Alveoli grouped in alveolar sacs

Respiratory membrane contains Type I/Type II Alveolar cells and Alveolar macrophages

Type I Alveolar Cells = make up lining of alveolar wall, very thin to allow gas exchange

Type II Alveolar Cells = cuboidal cells that release surfactant, which reduces surface tension

Alveolar Macrophages = Phagocytes that digest any debris not filtered out in bronchial tree

describe how the muscles of respiration cause air movement

Inspiratory muscles: Diaphragm muscle (contracts to lower and allow lungs to increase in volume), external intercostal muscles (contract to open rib cage to allow lungs to increase volume)

Expiratory muscles: Diaphragm and external intercostal muscles relax and lungs decrease in volume

Forced inspiration includes accessory inspiratory muscles (ex. internal intercostal, pectoralis minor, sternocleidomastoid, scalene muscles, serratus anterior muscles) Think when you’re sick and it’s harder to breathe and your muscles feel sore

describe the changes in volume and pressure that occur during inspiration and expiration, and how they contribute to ventilation

PV = nRT shows that Pressure and Volume are inversely related

As PRESSURE increases, VOLUME decreases

As PRESSURE decreases, VOLUME increases

Between breaths Atmospheric pressure = 760 mm Hg Intrapulmonary pressure = 760 intrapleural pressure = 756 (Intrapleural pressure is always lower than intrapulmonary pressure to prevent the lung from collapsing)

Inhale: Intrapulmonary and intrapleural pressure DECREASE (758 and 754) to cause volume to INCREASE

Exhale: Intrapulmonary and intrapleural pressure INCREASE (762 and 758) to cause volume to decrease

describe the difference between breathing at rest versus breathing when a person is in respiratory distress 

At rest, breathing is rhythmic and follows same pattern for pulmonary ventilation

During respiratory distress, hyperventilation or hypoventilation, wheezing, forced inspiration (use of accessory muscles)

name the lung volumes and capacities and describe the meaning of each value

Tidal Volume = Volume or air inhaled/exhaled in normal expiration

Inspiratory Reserve Volume = Volume that air can be forcibly inhaled

Expiratory Reserve Volume = Volume that air can be forcibly exhaled

Inspiratory capacity = Total amount of air that can be inhaled (Tidal volume + reserve)

Residual volume = volume leftover in the lungs after forced expiration

Functional residual capacity = Air left in lungs after normal expiration (ERV and RV)

Vital Capacity = Total amount of exchangeable air

Total Lung Capacity = Total exchangeable and nonexchangeable air in the lungs

explain the physiological significance of surfactant

Surfactant reduces alveolar surface tension which keeps the alveolus inflated to keep the alveolus partially open even during expiration

One end is polar and one is nonpolar, when it interacts with water, the nonpolar side repels water molecules and the polar side interacts with water molecules, disrupting H bonds between water molecules

describe the forces that push outward versus the forces the pull inward on lung tissue during ventilation

Stretch during inhalation (diaphragm/external intercostals push outward) and recoil during expiration (Diaphragm/external intercostals push inward)

explain how oxygen in the air eventually arrives at tissue cells

Pulmonary gas exchange = gas exchanged between alveoli and blood (PO2 in blood much lower than alveoli, and PCO2 slightly higher)

Systemic gas exchange = gas exchanged between blood in systemic capillaries and cells (PO2 in tissue cells much lower than capillaries, PCO2 slightly higher) This is because CO2 is more soluble in water

describe the two ways that oxygen travels in the blood, and how they are related

1. Bound to hemoglobin

2. Dissolved in the plasma

The amount of O2 that can bind to hemoglobin is directly related to how much O2 is dissolved in the plasma

explain how metabolically active tissues can retrieve more oxygen from the blood

In metabolically active tissues, oxygen is not bound as tightly to hemoglobin, allowing more oxygen to be unloaded. The opposite occurs for less metabolically active tissues

describe the three ways that carbon dioxide travels in the blood

1. Dissolved in plasma

2. Bound to hemoglobin (binds to peptide chains)

3. As bicarbonate ions in the blood (Most co2 travels this way) enzyme CA catalyzes reaction between carbon dioxide and water to produce carbonic acid, which dissociates into a bicarbonate ion and H+ ion (maintains pH via buffer system)

describe the physiological significance of the bicarbonate buffer system to maintain blood pH

When H+ increases in the blood, they bind to bicarbonate ions to form carbonic acid

When H+ decreases in the blood, Hydrogen ions are released from carbonic acid along with bicarbonate ions

This is why it is important that most CO2 travels through the blood as a bicarbonate ion to maintain pH

compare respiratory acidosis with respiratory alkalosis

Respiratory acidosis = from hypoventilation, decrease in breathing, increases blood CO2, which causes more H+ to stay in the blood and lowers pH (more acidic)

Respiratory alkalosis = from hyperventilation, increase in breathing, decreases blood CO2, which decreases the H+ in the blood and increases pH (More basic/less acidic) less carbonic acid to release H+ into the blood

describe how central chemoreceptors and peripheral chemoreceptors regulate respiratory rate

Central chemoreceptors = receptors scattered throughout brainstem, medulla, midbrain, hypothalamus, cerebellum, cause hyperventilation or hypoventilation in response to increased CO2 (Hyper) or decreased CO2 (hypo)

Peripheral chemoreceptors = Clusters of cells within the carotid artery and aorta, which are more sensitive to concentration of O2 in the blood, to change rate and depth of ventilation

compare restrictive disorders versus obstructive disorders, and classify a patient example as restrictive or obstructive

Restrictive disorders = Decreased pulmonary compliance that impacts inspiration (decreased elastic fibers of lung tissue/increased surface tension) ex. inflammation of lung tissue, Inhalation of lots of debris causing pneumoconiosis

Obstructive disorders = Increased airway resistance decrease expiration because the elastic recoil of lungs after expiration can cause collapse due to obstruction causing abnormally high resistance ex. COPD, asthma, lung cancer