Ch 23 Lecture Objectives

Chapter 23: Respiratory System Lecture Objectives

What is the difference between conducting and respiratory portions of the respiratory system? What are the anatomical structures associated with each?

• Conducting Portion: Comprises the anatomical structures that transport air from the external environment into the lungs. It includes the nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles. Its primary function is to filter, warm, and humidify the air before it reaches the lungs.

• Respiratory Portion: Composes the structures directly involved in gas exchange, primarily the alveoli, alveolar ducts, and respiratory bronchioles, where oxygen diffuses into the blood, and carbon dioxide diffuses out.

As we move from the nasal cavity all the way down to the alveoli, how does the epithelium change and why?

• The respiratory tract features various epithelial types that adapt to different functions:

  • Ciliated Pseudostratified Columnar Epithelium: Found in the nasal cavity, helps trap and transport debris.

  • Stratified Squamous Epithelium: Located in areas like the oropharynx, provides protection against mechanical stress.

  • Simple Squamous Epithelium: Found in the alveoli, facilitates efficient gas exchange due to a larger surface area.

What is the mucociliary escalator?

• The mucociliary escalator is a defense mechanism that involves mucus secretion that traps inhaled particles and pathogens. Cilia move the mucus upward toward the throat for swallowing or expulsion, keeping airways clear.

How do the nasal sinuses and meatuses help with the function of the respiratory system?

• These structures humidify and filter incoming air, contribute to voice resonance, and reduce skull weight. Sinuses lined with mucosa also help in immune defense by producing mucus.

What are the 3 parts of the pharynx and what epithelium lines each?

• The pharynx consists of three regions:

  • Nasopharynx: Lined with ciliated epithelium, serves as a passageway for air.

  • Oropharynx: Lined with stratified squamous epithelium, serves as a passageway for both air and food.

  • Laryngopharynx: Also lined with stratified squamous epithelium, this is the last section before food enters the esophagus and air enters the larynx.

What are the 3 large cartilages that form the larynx? What are their functions?

• The larynx contains:

  • Thyroid Cartilage: Protects the larynx and supports the vocal cords.

  • Cricoid Cartilage: Maintains an open airway and supports the larynx.

  • Epiglottis: Prevents food and liquid from entering the trachea during swallowing.

How does the coughing reflex protect the glottis/vestibular fold?

• The cough reflex involves the glottis closing momentarily to increase pressure in the lungs, followed by a strong burst of air expelling irritants, foreign particles, or mucus, protecting the glottis/vestibular fold from obstruction.

What are the 2 smaller pieces of cartilage that are important for producing sound? How do they work with the vocal fold? What leads to a high pitch vs. low pitch sound (2 factors)?

• The arytenoid cartilages pivot to adjust the tension on the vocal folds. Higher tension leads to higher pitch sounds, while lower tension results in lower pitch sounds. Additionally, airflow from the lungs influences pitch.

Why does our voice change when we have a sinus infection?

• Swelling of the nasal mucosa can alter sound resonance pathways, resulting in a nasal or muffled voice.

Why are cartilages of the trachea “C-shaped”? What are the primary, secondary, and tertiary bronchi?

• The C-shaped cartilages of the trachea provide structural support while allowing flexibility and expansion during breathing.

• Primary Bronchi enter each lung; Secondary Bronchi correspond to the lobes of the lungs (two on the left and three on the right); Tertiary Bronchi further branch into smaller segments of the lungs.

How does the tissue progressively change as we move from primary to tertiary bronchi to bronchioles/terminal bronchioles to respiratory bronchioles?

• The epithelium begins to shorten and change deeper into the lung, transitioning from pseudostratified ciliated columnar epithelium to simple cuboidal epithelium and eventually to simple squamous epithelium in the respiratory bronchioles. The cartilage transitions from C-shaped rings to irregular plates, and smooth muscle increases in proportion to control airflow.

What does sympathetic activation do to the bronchi? Parasympathetic stimulation?

• Sympathetic Activation induces bronchodilation, enhancing airflow, particularly during increased activity.

• Parasympathetic Stimulation induces bronchoconstriction, reducing airflow, often in response to irritants or allergens.

What 3 types of cells make up the alveoli? What does each of them do?

• The alveoli consist of:

  • Type I Cells: Simple squamous cells facilitating gas exchange.

  • Type II Cells: Produce surfactant to reduce surface tension and prevent alveolar collapse.

  • Macrophages: Immune cells that engulf and digest pathogens and debris.

What makes up the blood-air barrier and why is it efficient for gas exchange?

• The blood-air barrier consists of the alveolar epithelium and underlying capillary endothelial cells, creating a thin barrier that allows efficient gas exchange due to the short diffusion distance.

What is the cardiac notch in the lungs for? Is it on the left or right lung? What pleura lines the lungs vs. thoracic cavity?

• The cardiac notch is a concave structure on the medial surface of the left lung, accommodating the heart. The visceral pleura adheres directly to the lungs, while the parietal pleura lines the thoracic cavity.

What is Boyle’s Law and how does this relate to pulmonary ventilation (inhalation or inspiration/exhalation or expiration)? What does your diaphragm do? Why does an increased volume of thoracic cavity lead to increased lung volume?

• Boyle’s Law states there is an inverse relationship between pressure and volume. As the diaphragm contracts, it increases thoracic volume, lowering pressure and facilitating air intake during inhalation. Increased thoracic cavity volume leads to increased lung volume by creating a pressure gradient that allows air to flow in.

What is the difference between eupnea and hyperpnea? How do diaphragm and intercostal muscles help with quiet breathing? What two other muscles are helpful for forced breathing?

• Eupnea refers to normal, relaxed breathing, while hyperpnea indicates increased breathing rate and depth due to metabolic needs. The diaphragm and intercostal muscles are primarily responsible for quiet breathing, while accessory muscles, such as the sternocleidomastoid and scalene muscles, assist during forced breathing.

What is intrapulmonary pressure? How does the value change between cycles of inhalation and exhalation?

• Intrapulmonary pressure is the pressure within the lungs. It decreases during inhalation and increases during exhalation as air is drawn in and pushed out, respectively.

How does “compliance” affect the ability to breathe (lower value vs. higher value)? What 3 factors can affect compliance?

• Compliance measures lung flexibility. Higher compliance indicates easier inflation, while lower compliance suggests stiffness, making breathing more difficult. Factors affecting compliance include elasticity of lung tissue, surface tension in alveoli, and thoracic wall stiffness.

What is the formula for calculating respiratory minute volume? What about alveolar ventilation? What does this formula account for compared with respiratory minute volume?

• Respiratory Minute Volume (RMV): Total volume of air entering the lungs per minute, calculated as RMV = Tidal Volume x Respiratory Rate.

• Alveolar Ventilation considers only the air reaching the alveoli for gas exchange:Alveolar Ventilation = (Tidal Volume - Dead Space Volume) x Respiratory Rate.

Know the 6 different respiratory “volumes” and what do they represent.

• Tidal Volume (TV): Volume of air inhaled or exhaled during normal breathing.

• Inspiratory Reserve Volume (IRV): Additional volume of air that can be inhaled after a normal inhalation.

• Expiratory Reserve Volume (ERV): Additional volume of air that can be exhaled after a normal exhalation.

• Residual Volume (RV): Volume of air remaining in the lungs after maximal exhalation.

• Vital Capacity (VC): Maximum amount of air exhaled after a maximal inhalation (VC = TV + IRV + ERV).

• Total Lung Capacity (TLC): Total volume of air the lungs can hold (TLC = VC + RV).

What do Dalton’s law and Henry’s law? (Know them according to how I have simplified them in lecture)

• Dalton’s Law: The total pressure of a gas mixture is the sum of the partial pressures of individual gases.

• Henry’s Law: The amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid.

What is the difference between external and internal respiration? (Make sure you know the differences in the numbers of pressures of gases in the alveoli vs. capillaries and capillaries vs. peripheral tissues. This is illustrated later in the chapter.). Understand how do the pressures of these gases drive which direction O2 and CO2 move.

• External Respiration: Gas exchange between alveoli and blood in pulmonary capillaries. Oxygen enters blood as CO2 exits. Alveolar PO2 is higher than capillary PO2.

• Internal Respiration: Gas exchange between blood and tissues. Oxygen moves into tissues while CO2 enters blood. Tissue PO2 is lower than capillary PO2, driving O2 into cells and CO2 into the bloodstream for transport back to the lungs.

How does the pressure of oxygen affect hemoglobin saturation? Is it a linear relationship? Why does this make sense according to what I have discussed in lecture?

• The pressure of oxygen (PO2) has a significant impact on hemoglobin saturation, following a non-linear relationship known as the oxygen-hemoglobin dissociation curve. As PO2 increases, hemoglobin saturation also increases, but the curve is sigmoidal (S-shaped), indicating that initially, a small increase in PO2 leads to a greater increase in saturation at lower pressures, followed by a plateau at higher pressures. This makes sense because it allows hemoglobin to efficiently pick up oxygen in the lungs (where PO2 is high) and release it in tissues (where PO2 is low).

How does pH affect hemoglobin saturation (Bohr effect)? Why does CO2 lead to a lower pH (more acidic)? Know the formula to explain this.

• The Bohr effect describes how a lower pH (more acidic environment) decreases hemoglobin's affinity for oxygen, leading to increased oxygen release in tissues where CO2 is produced. CO2 reacts with water to form carbonic acid, which dissociates into bicarbonate ions and hydrogen ions, lowering the pH:

  CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+

How does temperature affect hemoglobin saturation?

• Increased temperature decreases hemoglobin's affinity for oxygen, promoting oxygen release in metabolically active tissues that generate heat. Conversely, lower temperatures increase hemoglobin's affinity for oxygen, which helps in oxygen uptake in cooler lung environments.

What are the 3 ways of transport for CO2? What proportions of CO2 are transported in each way?

• CO2 is transported in three main forms:

  1. Dissolved in plasma: Approximately 7% of CO2 is dissolved directly in the blood plasma.

  2. Bound to hemoglobin: About 23% of CO2 binds to hemoglobin, forming carbaminohemoglobin.

  3. As bicarbonate ions (HCO3-): Approximately 70% of CO2 is converted to bicarbonate ions in red blood cells and transported in this form.

Explanation of the "Summary of Gas Transport" Diagram

• In understanding the diagram, remember that external respiration occurs in the alveoli where oxygen diffuses from the alveoli (high PO2) into the blood (low PO2), resulting in increased hemoglobin saturation. At the same time, CO2 diffuses from the blood (high PCO2) into the alveoli (low PCO2) for exhalation. Internal respiration refers to gas exchange between blood and tissues, where oxygen diffuses into tissues (low PO2) and CO2 diffuses into the blood (high PCO2), leading to decreased hemoglobin saturation as CO2 binds to hemoglobin and forms bicarbonate ions, contributing to lower blood pH.

In terms of chemoreceptor reflexes, what happens when we have hypercapnia? Hypocapnia?

• Hypercapnia (elevated levels of CO2) stimulates chemoreceptors, prompting an increase in ventilation to expel CO2 and bring levels back to normal. Conversely, hypocapnia (reduced levels of CO2) leads to decreased ventilation as the body seeks to retain CO2 levels.

What happens in terms of baroreceptor reflexes when BP falls?

• When blood pressure falls, baroreceptors in the aorta and carotid arteries detect the change and trigger a reflex response that increases heart rate and induces vasoconstriction to restore blood pressure.

What are the Hering-Breuer reflexes?

• The Hering-Breuer reflexes are protective reflexes that prevent over-inflation of the lungs. Stretch receptors in the lungs send signals to the brain to inhibit further inhalation when the lungs expand to a certain point.

What are the 3 different protective reflexes we have with the respiratory system?

• The three protective reflexes include:

  1. Cough Reflex: Clears irritants from the airway.

  2. Sneezing Reflex: Clears irritants from the nasal passages.

  3. Bronchoconstriction: Reduces airflow in response to irritants or allergens to protect the lungs.

How does the respiratory system differ in newborns vs. elderly individuals?

• Newborns have underdeveloped lungs and lower compliance, making them more vulnerable to respiratory distress. In contrast, elderly individuals often experience a decline in lung elasticity, reduced surface area for gas exchange, and increased risk of respiratory diseases due to age-related changes.

Conditions associated with this chapter (know what these are and causes if applicable):

• Laryngitis: Inflammation of the larynx, often due to infection or overuse.

• Acute Epiglottitis: Inflammation of the epiglottis, which can be life-threatening due to airway obstruction, often caused by bacterial infection.

• Bronchitis: Inflammation of the bronchi, resulting in coughing and mucus production, often triggered by infections or irritants.

• Asthma: A chronic condition characterized by airway inflammation and constriction leading to breathing difficulty.

• Respiratory Distress Syndrome: Often seen in premature infants due to insufficient surfactant in the lungs.

• Pneumonia: Infection of the lungs causing inflammation and buildup of fluid or pus in the alveoli.

• Pleurisy: Inflammation of the pleura, causing chest pain during breathing.

• Pneumothorax: The presence of air in the pleural space, causing lung collapse.

• Atelectasis: Collapse of part of a lung, leading to reduced gas exchange.

• Hypoxia: A deficiency of oxygen in tissues.

• Anoxia: A complete absence of oxygen.

• Emphysema: A condition that involves the destruction of alveoli, reducing the surface area for gas exchange.

• Apnea/Eupnea/Hyperpnea: Terms that describe different breathing patterns. Apnea refers to temporary cessation of breathing, eupnea is normal breath, and hyperpnea is increased depth and rate of breathing usually in response to exercise or oxygen demand.