Respiratory System Overview

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Questions and Answers

What primarily determines airway resistance in the respiratory passages?

Pressure in atmosphere

Volume of air in the lung

Temperature of air entering the lungs

Radius and cross sectional area of the airway (correct)

How does exercise affect airway resistance?

It decreases resistance by promoting dilation of nares. (correct)

It significantly increases resistance due to increased airflow.

It increases mucosal thickness leading to higher resistance.

It has no effect on airway resistance.

Which type of airflow is produced in the upper airways due to low cross sectional area?

Turbulent flow (correct)

Steady flow

Transitional flow

Laminar flow

What initiates bronchoconstriction in the airways?

Contraction of airway smooth muscles via acetylcholine Signup and view all the answers

What is the relationship between body weight and basal metabolism in animals?

Metabolism rate is defined by kg^0.75. Signup and view all the answers

What is the effect of epinephrine on airway smooth muscles?

It relaxes the smooth muscles. Signup and view all the answers

What happens to the velocity of airflow when the cross sectional area of the airways increases?

Velocity decreases. Signup and view all the answers

Which factors contribute to enhanced mucociliary clearance of pathogens?

Healthy ciliary function and airway patency Signup and view all the answers

What is minute ventilation a product of?

Tidal volume and respiratory rate Signup and view all the answers

How does the body respond to increased metabolic demand for oxygen?

By increasing minute ventilation through either or both tidal volume and breathing frequency Signup and view all the answers

What occurs during thermoregulation when animals are heat-stressed?

Animals pant to increase ventilation of dead space Signup and view all the answers

What is a key finding in the diagnosis of pulmonary fibrosis in the presented patient?

Decreased compliance and reduced tidal volume Signup and view all the answers

Which parameter is used to represent the relationship between minute ventilation, alveolar ventilation, and dead space ventilation?

VE = VA + VD Signup and view all the answers

Which of the following best describes the observation of a thin dog with elevated respiratory rate but poor airflow during inhalation?

Indication of respiratory muscle fatigue Signup and view all the answers

During breathing, what happens to the heat and water vapor in cooler inhaled air?

They diffuse from the mucosa surface of the conducting system Signup and view all the answers

What can cause a decrease in breathing frequency in animals under cold stress?

Conservation of body heat Signup and view all the answers

What primarily influences the maximum oxygen consumption (VO2max) in animals?

The total mass of mitochondria in skeletal muscles Signup and view all the answers

What is the tidal volume (TV) in terms of lung function?

The volume of air moved in or out during quiet resting breathing Signup and view all the answers

Which type of dead space refers to the areas of airways not equipped to partake in gas exchange?

Anatomic dead space Signup and view all the answers

How does heat stress affect the respiratory rate in animals such as cattle and pigs?

It increases the respiratory rate and dead space ventilation Signup and view all the answers

What is residual volume (RV) in the context of lung volumes?

The volume of air that remains in the lungs after maximal expiration Signup and view all the answers

Which of the following describes alveolar ventilation (VA)?

The volume of air that reaches perfused alveoli Signup and view all the answers

What mechanism do animals use to retain heat during cold stress?

Increase tidal volume and decrease frequency of breathing Signup and view all the answers

Which of the following is NOT considered part of the dead space in the respiratory system?

Functional residual capacity Signup and view all the answers

Study Notes

Respiratory Function

The respiratory system is responsible for gas exchange
It takes in oxygen and removes carbon dioxide
The system includes the nasal passages, larynx, trachea, bronchial tubes, and lungs
It carries out two main functions:
- External respiration—exchanging air between the body and the environment.
- Internal respiration—bringing oxygen to cells and removing carbon dioxide.

Respiratory Function Structure

Structurally divided into upper and lower airways
Upper airways: Nasal passages, nares, pharynx, larynx, trachea
Lower airways: Bronchi, bronchioles, alveolar sacs, alveoli
Trachea and bronchi contain cartilage to prevent collapse.
Goblet cells and bronchial glands produce mucus to help trap foreign bodies.
Bronchioles do not have cartilage; are lined with Clara cells for secretion.
Alveoli, alveolar ducts, respiratory bronchioles are responsible for gas exchange.

Respiratory Function Functional

Conducting airways (Nares, nasal passage, larynx, trachea, bronchi, bronchioles) conducts air from the environment to respiratory airways, filters, warms, and humidifies air
Conducting airways, from the nares to the bronchioles, are responsible for conditioning air
Respiratory airways (terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli) are responsible for gas exchange
Gas exchange occurs in alveoli, this is where oxygen and carbon dioxide move between air and blood.

The Nose (External Nares)

Also called external nares
Divided into two halves by the nasal septum
Contains the paranasal sinuses where air is warmed
Contains cilia that filter out foreign bodies

Nose and Nasal Cavities

Frontal sinus, Middle nasal concha, Inferior nasal concha, External nares, Internal nares, Nasopharynx, are parts of nose and nasal cavities
Contains structures that help warm, filter and humidify air.

External Respiration

Air enters the nose or mouth during inspiration (inhalation)
The pathway includes the nasal cavity, paranasal sinuses, pharynx, and larynx
These structures are parts of the conducting portion of the respiratory system

Three Sections of the Pharynx

Nasopharynx: contains the pharyngeal tonsils (adenoids). Helps with the body's immune defense.
Oropharynx: back portion of the mouth; contains the palatine tonsils. Helps with the body's immune defense
Laryngopharynx: bottom section of the pharynx where the respiratory tract divides into the esophagus and the larynx

Larynx

Voice box, short and cylindrical airway ending in the trachea
Prevents swallowed materials entering the lower respiratory tract
Conducts air into the lower respiratory tract
Has nine pieces of cartilage that are supported by ligaments and muscles
Includes Hyoid Bone, Epiglottis, Thyroid Cartilage, Cricothyroid Ligament, Cricothyroid Muscles, Cricothyroid Cartilage, Trachea

Trachea

Flexible tube also called the windpipe
Extends through the mediastinum
Located anterior to the esophagus and inferior to the larynx
Cartilage rings provide rigidity to the tracheal wall to keep it open.
- At sternal angle, the trachea bifurcates into two smaller tubes (right and left primary bronchi).
- Each primary bronchus projects laterally toward each lung.

Lungs

Each lung has a conical shape with a wide, concave base resting on the muscular diaphragm.
The superior region is the apex, which projects superiorly and slightly superior and posterior to the clavicle.
Lungs are bordered by the thoracic wall—anteriorly, laterally, and posteriorly.
Supported by the rib cage, and separated by the mediastinum.
The costal surface is the rounded surface in contact with the thoracic wall.

How Lungs Work

Air enters through bronchi to alveoli, where gas exchange happens
Oxygen moves into the blood, and carbon dioxide moves out of the blood
Air is inhaled through trachea and bronchi to alveoli
Oxygen in the air moves into the blood in capillaries lining the alveoli
Carbon dioxide moves from blood in capillaries to the air in alveoli to be exhaled
This process happens during breathing

Breathing

Lungs are sealed in pleural membranes inside the chest cavity
The diaphragm is a large, flat muscle at the bottom of the cavity
During inhalation, the diaphragm contracts, rib cage rises, and chest cavity volume expands
A partial vacuum is created; atmospheric pressure forces air into the breathing passages
During exhaling, the diaphragm relaxes, rib cage lowers, and chest cavity volume decreases
Air pressure inside is higher than atmospheric, so air is pushed out of the lungs.

Inspiration vs. Expiration

Inspiration (inhalation): A product of respiratory muscle contraction, resulting in expansion of the thorax and lungs—creates a negative (sub-atmospheric) pressure that pulls air into the lungs. This is an active process.
Expiration (exhalation): Elastic energy of the stretched lungs and thorax drives exhalation. In resting animals, it's passive. Horses are an exception as they can actively use their muscles for exhalation even at rest. Active exhalation occurs during exercise or illness.

Respiratory Muscles

Diaphragm, external intercostals, neck muscles (SCM), internal intercostals, abdominal muscles are muscles responsible for respiration.

Compliance and Elasticity

Compliance (C): Measures the distensibility of an elastic structure. Healthy lungs have high compliance. A small change in transpulmonary pressure results in a large change in lung volume.
Elasticity (E): Measures how well a stretched structure returns to its original shape.

Pressure-Volume Curve

Graph representing the relationship between lung volume and its distending pressures (Elastance and compliance.)
The slope of the curve is steep in the middle, indicating small changes in transpulmonary pressure result in large changes in lung volume.
At extreme volumes (residual volume and total lung capacity), the slope is less steep, indicating that a larger transpulmonary pressure is required to cause a change in lung volume.

Surfactant

Lipids (mostly dipalmitoyl phosphatidylcholine) and proteins that line the inner surface of alveoli.
Prevents surface tension on the surface of alveoli, which would otherwise cause alveolar collapse.
Produced late in the neonatal period by type II pneumocytes.
Deep inspiration aids in the release of surfactant after birth.
Hydrophobic and hydrophilic properties enable surfactant to bind to fluid lining alveoli and break up cohesive forces keeping the alveoli open and inflated.
Premature newborns may have inadequate surfactant, which leads to respiratory distress syndrome, requiring synthetic surfactant.

Airway Resistance

Force that impedes airflow.
Mathematically, Resistance (R) = Pressure drop/Flow, primarily determined by radius and cross-sectional area (R=1/r^4).
Resistance is mostly in upper airways (e.g., nares, nasal passages, larynx, trachea), lower is less.
Resistance decreases with exercise due to factors such as dilation of nares, vasoconstriction of nasal vascular tissue, and reduced mucosal thickness allowing for breathing through the mouth.

Velocity of Airflow

Distance traveled per unit time by air within the respiratory system
Function of the air volume and cross-sectional area (Velocity= K Volume/Cross Sectional Area)
High velocity and turbulent flow in upper airways (can be heard through stethoscope).
Low velocity and laminar flow in lower airways (cannot be heard through stethoscope).

Bronchoconstriction

Contraction of smooth muscles lining the airways from trachea to alveolar ducts, influenced by parasympathetic nervous system via acetylcholine and muscarinic receptors on the smooth muscle.
Triggered by inhalation of irritant materials (dust) or inflammatory mediators (histamine, leukotrienes).
Also involves relaxation of smooth muscles by the activity of epinephrine and norepinephrine on β2-adrenergic receptors in the smooth muscle.

Respiration and Metabolism

Respiratory system provides oxygen for metabolism and rids the body of carbon dioxide (metabolic by-product)
Rate of O2 consumption/CO2 production depends on the body's metabolism rate, activity, and physical condition.
Relationship between body weight and basal metabolism: kg^0.75
Smaller animals consume more oxygen per kilogram of body weight than larger animals; this is due to their larger surface area for heat loss requiring higher basal metabolism.
Maximum O2 consumption (VO2 max) directly proportional to the mass of mitochondria in skeletal muscles in athletic animals.

Lung Volumes

The ease of lung expansion/contraction is due to high lung compliance.
Lung volumes vary throughout the respiratory cycle.
- Total lung capacity (TLC) is the maximum air the lungs can hold after maximum inspiration, and residual volume (RV) is the air remaining after maximal forced expiration.
- Tidal volume (TV) is the air moved in/out of the lungs during quiet breathing.
- Functional residual capacity (FRC) is the amount of air in the lungs at the end of quiet exhalation, vital capacity (VC) is the maximum volume of air that can be moved.

Dead Space Ventilation

Dead space Ventilation (VD) is the inhaled air that doesn't participate in gas exchange
- Anatomic dead space: airway areas not involved in gas exchange (conducting airways).
- Alveolar dead space: alveoli ventilated but not perfused with blood
- Physiological dead space is the sum of anatomic and alveolar dead spaces.

Alveolar Ventilation

Alveolar ventilation (VA): volume of air reaching the perfused alveoli.
Tightly regulated by the body to match O2 uptake and CO2 elimination.
Minute ventilation (VE): total volume of air breathed per minute.
Calculated as VE = Tidal volume (TV) x breathing frequency (f)
Increases when metabolic demand increases, either via increased tidal volume, or breathing frequency or both.

Role of Dead Space Ventilation in Thermoregulation

Cooler inhaled air diffuses heat and water vapor out of the mucosa of conducting airways
During heat stress, panting (increased breathing frequency) increases ventilation, and loss of heat from the respiratory passages.
During cold stress, breathing frequency decreases to conserve heat.

Control of Respiration

Central neural control (cortex, medulla, pons) control inhalation and exhalation.
Sensory input systems (mechanoreceptors, metaboreceptors, peripheral/central chemoreceptors) influence the rate and depth of respiration
Respiratory muscles (diaphragm, external intercostals, internal intercostals, accessory muscles) carry out respiration mechanics.

Clinical Correlation

Described a clinical case of pulmonary fibrosis in a dog.
Included history, clinical examination, radiographic findings and treatment.
Identified pulmonary fibrosis as a diffuse disease affecting gas exchange and leading to decreased lung compliance and increased work of breathing which reduced lung function.

Multiple Choice Questions (MCQs)

A series of multiple-choice questions covering various aspects of respiratory system anatomy, physiology, and function; including the questions on gas exchange, lung volumes and mechanics and associated regulation.

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Description

Explore the respiratory system's structure and functions in this quiz. Learn about gas exchange, the roles of upper and lower airways, and the significant anatomy involved in respiration. Ideal for students interested in biology and human anatomy.