Chapter 22

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Pulmonary ventillation

“breathing”

1. inspiration

2. expiration

two phases of pulmonary ventilation

1. involved in production of speech

2. Involved in sense of smell (olfaction)

Additional functions of the respiratory system (besides breathing) [2]

1. provides cells with oxygen

2. Removes CO2

Major functions of the respiratory system: [2]

1. pulmonary ventillation

2. External respiration

3. Transportation of gases

4. internal respiration

4 processes in respiraton:

External respiration

exchange between capillaries and lungs. Oxygen from lungs is going to the blood, and CO2 from blood is going to the lungs. Transfer of gasses from lungs to blood.

Internal respiration

Oxygen is going from blood to tissues, and CO2 is going from tissues to blood. Process in respiration

Respiratory: pulmonary ventilation and external respiration

Cardiovascular: Transport of respiratory gasses and internal respiration

In respiration, what processes are part of the respiratory system and what are part of cardiovascular system?

Cellular respiration

The use of oxygen and the production of carbon dioxide by cells. It is central to all energy-producing chemical reactions in the body, not technically part of respiratory system

Nose to larynx

Upper respiratory system goes from:

Larynx to diaphragm

Lower respiratory system goes from:

Palate. Has hard and soft portions

Separates nasal from oral cavity

Nasal conchae

Indentations that cause air to twist and turn around the surfaces, causes large particles to get trapped in the mucous

Large particles get trapped in mucous in nasal conchae. particles larger than 6 micrometers do not pass through

How does the nasal cavity act as a filter?

Pharynx

Connects the nasal cavity and mouth to the larynx and esophagus. Commonly referred to as throat

1. Nasopharynx

2. Oropharynx

3. Laryngopharynx

Three parts of parynx:

Nasopharynx

pharynx above food entry point. Only thing entering this passage is air.

When swallowing, palate and uvula close off the nasopharynx

When is nasopharynx closed?

Oropharynx

Air enters this passage from the nose and mouth, food also passes through.

Oropharynx

Where are palatine tonsils located?

Increased friction from swallowing foods, and chemical trauma from foods (hot, spicy).

Why is epithelium in oropharynx more protective?

Laryngopharynx

Region of the pharynx posterior to the larynx that marks the divergence between digestive and respiratory pathways.

Anteriorly (food enters esophagus posteriorly)

Which way does air enter the pharynx?

1. larynx

2. trachea

3. bronchi

4. lungs

Lower respiratory system consists of: [4]

Larynx

Anterior throat, superiorly attached to hyoid bone and inferiorly it is continuous with the trachea. “Voice box”

1. To provide a patent/ open airway (constant air supply)

2. Switching mechanism to ensure food and air enter proper channels (food posterior and air anterior)

3. Voice production (houses vocal cords)

4. Sphincter in specific situations (defecation, heavy lifting)

Functions of the larynx: [4]

Valsalva maneuver

Occurs during abdominal straining. Larynx acts as a sphincter to build up abdominal pressure to help support the trunk. Air cannot escape, so pressure continues to build.

“cartilage puzzle”. 9 different cartilage pieces are interconnected with membranes and ligaments

Structure of the larynx is compared to what?

Hyaline (besides epiglottis)

Type of cartilage in larynx

Elastic

Type of cartilage of epiglottis

Thyroid cartilage

Main piece of cartilage in the larynx, is actually two pieces joined together. In the area of the thyroid gland. Where we see adams apple (more common in males).

Cricoid cartilage

other main piece of cartilage in larynx, below thyroid cartilage.

Space between thyroid and cricoid cartilage

Where is a tracheostomy done?

Epiglottis

one of nine pieces of cartilage in larynx. Covered in taste buds. Covers opening to the larynx when swallowing. “Guardian of the airways”

Cough reflex

What happens if anything other than food enters larynx?

Vocal folds or true vocal cords

Structures in the larynx that vibrate to produce sound as air rushes up from the lungs

Glottis

Opening between the vocal folds that changes size and is controlled by muscles.

Trachea

extends from larynx to mediastinum. “Windpipe”.

1. Mucosa

2. Submucosa

3. C shaped rings of hyaline cartilage

4. Adventitia

layers of trachea (inner to outer) [4]

Mucosa

Layer of trachea with cilia that catch smaller particles in mucous and move mucous toward the pharynx (innermost layer)

Submucosa

Layer of trachea with glands that produce mucous.

C shaped rings of hyaline cartilage

Layer of trachea that allows the trachea to keep its shape. Without it, there would be no structure and could collapse on itself. The incomplete tube structure gives it flexibility so it can move during breathing and for esophagus to expand for swallowing food.

Trachealis

Causes the diameter of the trachea to decrease. Air expired with greater force.

Adventitia

Outermost layer of trachea

Bronchi

Air passageways to the lungs that branch over and over again

1. conducting zone

2. Respiratory zone

Two zones of the lungs:

Conducting zone

zone where air from trachea tunnels and lets air go where it needs to go

Respiratory zone

Zone of the lung where gas exchange happens

secondary bronchus

Bronchus that supplies each lobe:

Tertiary/segmental bronchi

Bronchi after secondary bronchi

Bronchioles

Bronchi less than 1mm in diameter

1. Cartilage rings replaced by plates of cartilage. By bronchioles, no cartilage

2. Epithelium changes: few mucous producing cells and cilia. At lower levels of conducting zone, no longer have cilia and mucous. Debris removed by macrophages

3. Smooth muscle increases as passageway diameter decreases.

As bronchi get smaller, what are the three main structural changes?

Smooth muscle gives the bronchioles the ability to constrict. Can produce resistance to air flow.

Functional implications of smooth muscle in the bronchioles:

The presence of thick walled air sacs called alveoli. Begins at terminal bronchioles as they feed in to the respiratory bronchioles.

How is the respiratory zone defined?

Respiratory membrane

Thin walls of the alveoli. On the outside of walls, alveoli are covered with a cobweb of pulmonary capillaries. Where gas exchange is happening

Alveolar pores

Little holes in alveolar walls that connect adjacent alveoli for even air pressure, and provides alternative routes of air flow

1. Type 1 alveolar cells

2. Type II alveolar ells

3. Alveolar macrophages

Three types of alveolar cells

Type I alveolar cells

Alveolar cells that form the walls (majority of cells)

Type II alveolar cells

Less abundant alveolar cells that secrete surfactant. Important in reducing surface tension in alveolar fluid.

Alveolar macrophages

Alveolar cells that get rid of bacteria, dust, and other debris (because there are no cilia)

Apex of the heart. Left is slightly smaller

Why are lungs different shapes?

Cardiac notch

Where the apex of the heart sits against left lung

Oblique fissure

Divides superior and inferior lobes of left lung

1. Superior lobe

2. Inferior lobe

Lobes of the left lung [2]

1. Superior lobe

2. Middle lobe

3. Inferior lobe

Lobes of the right lung [3]

horizonal fissure

Divides superior and middle lobe:

Oblique fissure

Divides middle and inferior lobe:

Bronchopulmonary segments

Each lobe contains a segment supplied by own artery and vein, and receives air from individual tertiary bronchus. Generally, left has 10 total and right has 8-10

Disease is often confined to one segment and does not impact function of other parts of the lung. You can resect or remove a segment without damaging the rest of the tissue.

Clinical implications of bronchopulmonary segments:

Root of the lung

Collection of vascular and bronchial structures that branch off mediastinum and go into the lung

Hilum

Little indentation where root enters

Stoma

All other tissue in the lungs besides alveoli are referred to as

To protect delicate lung vessels

Why are lungs generally low pressure?

Once every minute (pulmonary circulation)

How often does total blood volume flow through the lungs

Bronchial circulation

Arise from aorta. High pressure, low volume supply of blood to all tissues in the lungs. I

Innervated by sympathetic and parasympathetic nervous system, enters via pulmonary plexus

Innervation of the lungs:

Lung pleura (parietal and visceral)

membrane covers thoracic wall and surface of lungs. Functions to provide frictionless movement of lungs relative to thoracic cage.

Pleuracy

Friction in the pleura. Often associated with pneumonia

Pleural fluid

Tiny cavity (potential space in between parietal and visceral pleura contains:

because of a volume change in the lungs. Changes in volume lead to breathing because they lead to pressure changes leading to the flow of gas to equalize pressure

Why is breathing a purely mechanical process?

As volume decreases, pressure increases (vice versa)

Volume relative to pressure:

1. diaphragm contracts, pulls down and gets flatter (increases height of thoracic cavity)

2. Intercostal muscles contract, causing ribs to move out and up (increases anterior and posterior, and lateral dimensions

Two things that happen during quiet inhalation

500mL

How much does volume of thoracic cavity increase on inhalation?

Muscles relax, diaphragm and ribs go back to resting position. Lungs recoil and air is pushed out.

What happens on quiet exhalation?

Passive process driven by contraction of diaphragm and intercostal muscles

Is exhalation a passive or active process?

Forced ventilation

Ventilation where body recruits additional muscles to increase thoracic muscles

(breathing heavy

, exercising,

obstructive lung disease,

acute lung condition)

reasons for forced ventilation: [4]

1. Scalene

2. Sternocleidomastoid

3. Extensor muscles of back

4. Contracting abdominal muscles

Extra muscles involved in forced ventilation:

1. airway resistance

2. Alveolar surface tension

3. Lung compliance

4. Compliance of thoracic wall

Four main factors than influence ventilation

1. Smaller diameter, greater resistence

2. In healthy individual, diameter of airway is not a factor that influences ventilation

3. Is a problem in asthma, airways constrict and ventilation barrier

Influence of airway resistance on ventilation: [3]

Alveoli tend to want to collapse (water and gas don’t mix). Water pulling away from the gas is the surface tension. Surfactant diminishes the surface tension and prevents collapse. If they do collapse, makes breathing harder (takes more energy)

Influence of alveolar surface tension on ventilation:

The higher the compliance, the easier it is for the lungs to expand. Will not effect normal, healthy individual.

Influence of lung compliance on ventilation:

1. lung tissue itself (how stretchy)

2. Alveolar surface tension

Lung compliance is determined by: [2]

Compliance

“stretchiness” of the lungs

Anything that limits thoracic expansion will negatively impact ventilation (paralysis, scoliosis, phrenic nerve injuries, etc.)

Influence of the thoracic wall on ventilation

Pathology that limits distensibility (chronic inflammation leading to scar tissue (fibrosis) or limits production of surfactant will result in lower compliance and increased work of breathing

How do pathologies leading to scar tissue result in lower compliance?

Spirometry

How measure volume of air during ventilation

Pulmonary function test

How to measure rate at which air is flowing

Minute ventilation and alveolar ventilation

How to measure efficiency of the respiratory system:

Different lung conditions will produce different results. Most useful for evaluating losses in function and following the course of disease.

How is spirometry used as a diagnostic tool?