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Anatomy, Physiology, and Disease An Interactive Journey for Health Professionals

CHAPTER

Second Edition

The Respiratory System: It's a Gas

Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e Bruce J. Colbert • Jeff J. Ankney • Karen Lee

Introduction

• Respiratory system's primary function: to transport oxygen from atmosphere to bloodstream to be utilized by cells, tissues, organs for process of cellular respiration, which is necessary to sustain life

Introduction

• Respiratory system moves 12,000 quarts of air per day in and out of lungs

• Respiratory system removes waste gas—carbon dioxide—so it doesn't build up in toxic levels

Learning Objectives

• List and state the basic functions of the components of the respiratory system

• Differentiate between respiration and ventilation

• Explain how the respiratory system warms and humidifies inhaled air

• State the purpose and function of the mucociliary escalator

Learning Objectives

• Differentiate between the upper and lower airways and their functions

• Discuss the process of gas exchange at the alveolar level

• Describe the various skeletal structures related to the respiratory system

• Explain the actual process of breathing

• Discuss several common respiratory system diseases

System Overview

• Cellular respiration depends on continuous supply of oxygen, found in abundance in air we breathe

• Using oxygen produces carbon dioxide, which would become toxic if allowed to build in bloodstream; must be removed

System Overview

• Respiratory system closely related to heart and circulatory system; they are sometimes grouped together as cardiopulmonary system

System Overview

• Components of respiratory system

–Two lungs that serve as vital organs

–Upper and lower airways that conduct gas in and out of the system

–Terminal air sacs called alveoli surrounded by network of capillaries that provide for gas exchange

System Overview

• Components of respiratory system

–Thoracic cage that houses, protects, facilitates function for the system

–Muscles of breathing that include the main muscle, the diaphragm, and accessory muscles

Figure 13-1 The various components of the respiratory system.

Ventilation versus Respiration

• Air contains many gases, predominantly nitrogen, which is a support gas that keeps lungs open with its constant volume and pressure

• Next highest concentration found in air is oxygen, essential to life; carbon dioxide is found in very small concentrations

• Ventilation: bulk movement of air into and out of lungs where gas exchange will takes place

• Respiration: process of gas exchange, where oxygen added to blood and carbon dioxide removed

• External respiration: gas exchange in lungs occurs between blood and air in the external atmosphere

• Internal respiration: oxygenated blood transported internally via cardiovascular system to cells and tissues; oxygen moves into cells as carbon dioxide removed

Table 13-1 Gases in the Atmosphere

Figure 13-2 Contrast of ventilation and external and internal respiration.

The Airways and Lungs

• We have reserve of oxygen to last 4 to 6 minutes; after that we will die if we don't get more oxygen

• Respiratory system is series of branching tubes called bronchi and bronchioles

• Transport atmospheric gas deep within lungs to small air sacs called alveoli, which represent terminal end of respiratory system

• Each alveolus is surrounded by capillaries; combination called alveolar-capillary membrane; represents connection between respiratory and cardiovascular systems

Upper Airways of Respiratory Tract

• Upper airways consists of nose, mouth, pharynx, and larynx

–Functions include:

Heating or cooling inspired gases to body temperature

Filtering

Humidifying

• Upper airways consists of nose, mouth, pharynx, larynx

–Functions include:

Sense of smell or olfaction

Producing sounds or phonations

Ventilation, or conducting gas to lower airways

Figure 13-3 The upper airway and vocal cords.

• While some people breathe through their mouths, we are meant to breathe through our noses

–Rigid structure made of cartilage and bone

• While some people breathe through their mouths, we are meant to breathe through our noses

–Nasal cavity: behind nose, divided into three main regions

Vestibular

Olfactory

Respiratory

Figure 13-4 The nasal regions.

• Vestibular region: located inside nostrils and contains coarse nasal hairs that act as first line of defense for respiratory system

–These hairs (vibrissae) covered with sebum, greasy substance secreted by sebaceous glands of nose

–Sebum helps trap particles; keeps hairs soft and pliable

• Olfactory region: located on roof of nasal cavity, allowing air to be held there so it can be sampled

• Respiratory region

–Air warmed to body temperature and moistened in this region inside nasal cavity, which is lined with mucous membranes and richly supplied with blood

–There are three scroll-like bones (turbinates) that split incoming air into three channels, providing more surface area

• Respiratory region

–Turbinates serve to make incoming air current more turbulent, bringing more air in contact with mucous membranes for warming and moisture, adding 650 to 1,000mLs of water each day to moisten air to 80% relative humidity

Pathology Connection: The Nose

• Allergic rhinitis

–Occurs when allergens (like pollen) trigger nasal mucosa to secrete excessive mucous

–Treatments: antihistamine medications; allergy injections that desensitize person to allergen

Pathology Connection: The Nose

• Nasal polyps

–Noncancerous growths within nasal cavity

–May be related to chronic inflammation

–Can be surgically removed if they become large enough to block nasal passageway

• Mucociliary escalator

–Cells in epithelial lining of airways of respiratory system are called pseudostratified ciliated columnar cells

–Consists of single layer of tall columnlike cells that have nuclei at different heights, giving appearance of two or more layers when there is only one

–Each columnar cell has 200 to 250 cilia on its surface

–Goblet cells and submucosal glands are interspersed and produce about 100mLs of mucus per day

–Mucus resides as two layers:

Cilia reside in sol layer; contains thin, watery fluid that allows them to beat freely

Top layer is gel layer that is more viscous and sticky, trapping small particles

–Cilia act as tiny "oars" resting in watery sol layer

–Cilia beat 1,000 to 1,500 times per minute and propel gel layer and its trapped debris onward and upward about one inch per minute to be expelled

– In nose, debris-laden secretions pushed toward front of nasal cavity to be expelled through nose

–Pseudostratified ciliated columnar epithelium propels gel layer toward oral cavity to be expectorated with cough or swallowed into stomach

Figure 13-5 The mucociliary escalator.

• Skull contains air-filled cavities called sinuses that connect to nasal cavity via small passageways

– Located around nose and sometimes referred to as paranasal sinuses

–Cavities help prolong and intensify sound produced with our voice and helps to lighten weight of head

• Skull contains air-filled cavities called sinuses that connect to nasal cavity via small passageways

–Sinuses do not exist at birth

–Develop as we grow; facial features changes influenced by sinuses as we mature

–Sinuses also help to warm and moisturize air

Figure 13-6 The paranasal sinuses.

• Pharynx, or throat, is hollow muscular structure beginning behind nasal cavity, lined with epithelial tissue

• Pharynx can be divided into three sections

–Nasopharynx

–Oropharynx

– Laryngopharynx

Figure 13-7 The nasopharynx, oropharynx, and laryngopharynx and related structures.

• Nasopharynx is uppermost section, beginning behind nasal cavity

–Section contains lymphatic tissue called adenoids; passageways into middle ear called Eustachian tubes

–Air from nasal cavity passes through nasopharynx

• Oropharynx is located behind oral, or buccal, cavity

–Conducts not only atmospheric gas but also food and liquid

–Air breathed through both nose and mouth passes through here, as does anything that is swallowed

• Tonsils are part of lymph system

–Palatine tonsils are located in oropharynx, as are lingual tonsils located at back of tongue

–During swallowing, uvula and soft palate move in posterior and superior position to protect nasopharynx and nasal cavity from entry of food or liquid; can be overcome by forceful laughing

• Laryngopharynx is lowermost portion of pharynx

–Air breathed and/or swallowed passes through laryngopharynx

–Swallowed materials pass through esophagus to get to stomach

–Air travels through larynx and trachea on its way to lungs

• Larynx (voice box)

–Semirigid structure composed of cartilage connected by muscles and ligaments that provide movement of vocal cords to control speech

– “Adam's apple” (thyroid cartilage) is largest of cartilages found in larynx

• Larynx (voice box)

–Cricoid cartilage lies beneath it, providing structure and support for airways so they do not collapse

–Glottis is opening that leads into larynx and eventually lungs

• Epiglottis

– Leaf-shaped flaplike fibrocartilage

–Closes over opening to larynx when you swallow; opens up when you breathe, as part of swallowing reflex (glottic or sphincter mechanism)

–Seals so food does not enter lungs

• Vocal cords act as dividing line between upper and lower airways

– Lower airway starts below vocal cords

–Upper airway ends at vocal cords

Pathology Connection: The Upper Airways

• Common cold

–Caused by over 200 different strains of viruses

–Causes acute inflammation of upper respiratory mucous membranes

–Treated by managing symptoms

• Common cold

–Can be prevented with good hand washing

–Should not be confused with colds, allergies or the flu (which are different diagnoses)

Table 13-2 Comparison of Asthma, Cold and Influenza

• Sinusitis

– Infection and inflammation of sinuses by viruses or bacteria

–Causes pressure, pain, headaches

• Tonsillitis

– Inflammation, swelling and pain of tonsils

–May require tonsillectomy if severe

• Pharyngitis

–Sore throat

–Strep throat caused by streptococcus bacteria

• Laryngitis

– Inflammation of voice box

–Characterized by hoarseness and loss of speech

–Caused by infection or excessive use of voice

Figure 13-8 The upper airway and related infections.

• Acute epiglottitis

–Potential airway emergency infection that causes swelling of epiglottis and airway obstruction

–Typically caused by Haemophilus influenzae type B

–Most common in children ages 2 to 6 (incidence decreasing since introduction of Hib vaccine)

• Acute epiglottitis

–Symptoms: acute swelling of epiglottis, fever, sore throat

–Onset rapid; requires rapid treatment

–Treatments: maintain airway, antibiotics

• Laryngotracheobronchitis (LTB)

– Infection of laryngeal area characterized by noisy breathing, especially on inspiration

–Symptoms

Barking cough

Inspiratory stridor (high-pitched sound often heard without using stethoscope)

–Disease was previously called croup

• Sleep apnea

–Breathing stops during sleep

–Caused by soft tissue at back of throat relaxing and blocking airway

–Can cause fatigue during day

– Long-term, undiagnosed sleep apnea can cause other health problems (high blood pressure, weight gain, and headaches)

• Sleep apnea

–Diagnosed during sleep study, where patient monitored while sleeping

–Treatment: special pillows and positioning patient that help to keep airway open; weight loss may reduce severity

–More severe obstructive sleep apnea may be treated with oral appliances, breathing devices, or surgery

The Lower Respiratory Tract

• Resembles upside-down tree, sometimes called tracheobronchial tree

• From vocal cords, air enters trachea, or windpipe, 4½˝ long tube lined with ciliated mucous membrane

• Trachea extends from cricoid cartilage of larynx to sixth thoracic vertebrae

• C-shaped cartilage found in anterior portion of trachea provide rigidity and protection for exposed airway in neck

• Esophagus lies in area where C opens up posteriorly; room for esophagus to expand when you swallow larger chunks of food

Figure 13-9 The tracheobronchial tree.

• Trachea largest pipe; can be thought of as trunk of tree

• Trachea begins branching (bifurcating) at center of chest into left and right mainstem bronchi (bronchus is singular form)

–Mainstem bronchi (primary bronchi)

• Site of bifurcation is called carina

• Next bronchi must branch into five lobular bronchi; correspond to five lobes of lungs

• Each lung lobe further divided into specific segments; next branching of bronchi called segmental bronchi

• At point from trachea down to segmental bronchi, tissue layers of bronchi are all the same, only smaller, as they branch downward

• Epithelial layer contains mucociliary escalator

• Middle is lamina propria layer which contains smooth muscle, lymph, and nerve tracts

• Third layer is protective and supportive cartilaginous layer

Figure 13-10 Tissue layers in the bronchi.

• Branching becomes more numerous with tiny subsegmental bronchi that branch deep within each lung segment

• Cartilaginous rings become more irregular and eventually fade away

• As we move towards gas exchange regions airways simplify to make it easier for gas molecules to pass through

• Bronchioles average 1 mm in diameter

• No cartilage layer; epithelial lining becomes ciliated cuboidal cells (short squat cells as opposed to large columns)

• Cilia, goblet cells, and submucosal glands are almost all gone

• There is no gas exchange yet

• Terminal bronchioles have average diameter of 0.5 mm, no goblet cells, cartilage, cilia, or submucosal glands at this point

• Terminal bronchioles mark border between conducting and respiratory zones

• Next airways beyond terminal bronchioles are respiratory bronchioles, because some gas exchange occurs here

• Epithelial lining is simple cuboidal epithelium interspersed with alveoli-type cells called simple squamous pneumocytes

• Alveolar ducts originate from respiratory bronchioles, wherein walls of alveolar ducts are made up of simple squamous cells arranged in tubular configuration

• These give way to alveoli

Figure 13-11 Conduction and gas exchange structures and functions.

• Alveoli are terminal air sacs, surrounded by numerous pulmonary capillaries

–Together capillaries and alveoli make up functional unit of lung known as alveolar capillary membrane

–Adults have 300–600 million alveoli, with total of 80 square meters (m2) surface area for oxygen molecule to diffuse across into capillaries

• Blood from right heart entering pulmonary capillaries is high in carbon dioxide and low in oxygen

• Conversely, carbon dioxide is high concentration in blood in pulmonary capillaries and very low in lung

• Gas exchange takes place and pulmonary capillary increases in oxygen concentration before traveling to left heart to be pumped around to tissues

Components of Alveolar Capillary Membrane

• Four distinct components of alveolar capillary membrane

–First layer is liquid surfactant layer that lines alveoli; this phospholipid helps lower surface tension in alveoli that would otherwise collapse

• Second component is tissue layer, or alveolar epithelium, comprised of simple squamous cells:

–Majority (95%) of alveolar surface is flat, pancakelike cells called squamous pneumocytes (Type I cells); gas molecules easily pass through in gas exchange

–Type II cells, or plump, granular pneumocytes, produce surfactant and aid in cellular repair

–Type III cells, or wandering macrophages, ingest foreign particles as they wander through alveoli

–Pores of Kohn are small holes between alveoli to allow movement of macrophages between alveoli

• Third component of alveolar capillary membrane is interstitial space

–Area separates basement membrane of alveolar epithelium from basement membrane of capillary endothelium and contains interstitial fluid

• Third component of alveolar capillary membrane is interstitial space

–Space so small that membranes of alveoli and capillary appear fused

– If too much fluid gets into space (interstitial edema), it separates, making it harder for gas exchange to occur

• Fourth component is capillary endothelium (simple squamous epithelium) that contains capillary blood and RBCs

Pulmonary Function Testing

• Measures lung function in terms of volumes and flows

• Measuring lung volumes

–Patient is instructed to

First, breathe normally

Then, take maximum deep breath followed by maximum exhalation

Various volumes recorded

Figure 13-12 Normal lung volumes and capacities.

• Lung volumes

–Tidal volume (VT): amount of air that moves into or out of lungs in normal breath; normal volume is about 500mL (varies by age, sex, height, and general fitness)

• Lung volumes

–Functional residual capacity (FRC): volume of air remaining in lungs at end of a normal expiration

– Inspiratory reserve volume (IRV): amount of air that can be forcefully inhaled after normal inspiration

• Lung volumes

–Expiratory reserve volume (ERV): amount of air that can be forcefully exhaled after normal expiration

–Residual volume (RV): volume of air remaining in lungs after maximum expiration

• Lung volumes

–Vital capacity (VC): maximum amount of air that can be move into and out of respiratory system in single respiratory cycle

• Flow rates

–Measure flow rates coming out of lung at various points during forced (maximum patient effort) vital capacity (FVC)

• Flow rates

–FEV1: forced expiratory volume in 1 second

Normal person can exhale 75–85% of their FVC in 1 second

Someone with obstructive lung disease takes longer to exhale; can exhale less than 70% of their FVC in 1 second

• PEFR: peak expiratory flow rate

–Maximum flow rate or speed of air person can rapidly expel after taking deepest possible breath

–Measured in liters per minute; should fall within predicted range

–Good test to reflect how larger airways functioning; monitor diseases such as asthma

Pathology Connection: The Lower Airways

• Atelectasis

–Condition in which air sacs of lungs either partially or totally collapsed

–Cause may be patient who cannot or will not take deep breaths to fully expand lungs, keep passageways open, stimulate production of surfactant

• Atelectasis

–Surgery, pain, injury of thoracic cage often makes deep breathing painful

–Patients who cannot cough up secretions also at risk for atelectasis

–Buildup of secretions can lead to pneumonia within 72 hours

• Pneumonia

– Lung infection caused by virus, fungus, bacterium, aspiration, or chemical inhalation

–Results in inflammation of infected area with accumulation of cell debris and fluid

• Pneumonia

–Some pneumonias actually destroy lung tissue

–Severe pneumonia can result in death

Figure 13-13 General locations for pneumonias.

• Tuberculosis (TB)

– Infectious disease that thrives in high oxygen areas such as lung

–Tubercles (lesions) form in lungs

–Bacteria can lay dormant for years

• Tuberculosis (TB)

–Unchecked, vast lung damage can occur

–Treated with medication; recent concern about form of tuberculosis very resistant to drugs normally used to treat TB; high mortality rate

• Chronic obstructive pulmonary disease (COPD)

–General term for conditions associated with

Sputum production

Dyspnea

Airflow obstruction

Impaired gas exchange

• Chronic obstructive pulmonary disease (COPD)

–Fourth leading cause of death in the United States

–Group of diseases in which patients have difficulty getting all the air out of lungs; often have large amounts of secretions and lung damage

–Combination of emphysema and chronic bronchitis

• Asthma

–Chronic inflammatory illness of airways; 25 million people in the United States

–Most common chronic disease of childhood and younger adults; 80% of cases developing before age 45

• Asthma

–Potentially life-threatening lung condition

–Airways of lungs constrict (bronchospasm) often in reaction to allergy

• Asthma

–Difficult to get air in; even more difficult to get air out of lungs

–Gas trapping: inability to get air out of lungs

– Lowers amount of oxygen in blood and increases blood levels of carbon dioxide

• Asthma

–Controlled with use of medication

–Symptoms: episodic wheezing, shortness of breath, cough, and chest tightness

• Asthma

–Common triggers: allergens, inhalants, viruses, cold air, and exercise

–Chronic disease

Figure 13-14 Asthma and emphysema.

Table 13-3 Asthma and COPD Diseases

Table 13-4 Triggers for Asthmatic Attacks

• Emphysema

–Anatomically as the permanent, abnormal enlargement of distal airway spaces and destruction of alveolar walls

–Nonreversible lung condition; alveolar air sacs destroyed and lung itself becomes “floppy”

• Emphysema

–Becomes more difficult for gases to diffuse between lungs and blood

– Lung tissue becomes fragile; easily rupture

• Emphysema

–Two million persons in the United States; majority of cases caused by smoking

–60,000 to 100,000 have a genetic deficiency of alpha1-antitrypsin (α1-AT)

Table 13-5 Diagnostic Markers to Differentiate COPD and Asthma

• Chronic bronchitis

–Productive cough, enlargement of mucous glands, hypertrophy of airway smooth muscle

–Acute bronchitis: temporary and common lung condition; can affect people of any age

Differs from chronic bronchitis; reversible and no permanent structural changes

–Nine million persons in the United States; cigarette smoking major causative factor

– Increase in size and number of mucus-secreting glands

–Narrowing and inflammation of small airways

–Obstruction of airways caused by narrowing and mucus hypersecretion

–Bacterial colonization of airways

–Acute episodes brought on by respiratory tract infection

–May undergo repeated episodes of respiratory failure; frequently develop right-sided heart failure

• Smoking major preventable cause of many respiratory diseases

–Primary etiology of COPD

–Smokers have more lung-function abnormalities

–Smokers show more respiratory symptoms

–Smokers experience all forms of COPD at much higher rate than nonsmokers

• Smoking major preventable cause of many respiratory diseases

–Age of starting, total pack-years, puff volume, current smoking status predictive of COPD mortality

–Passive smoking seems to increase risk

–Children of parents who smoke higher prevalence of respiratory symptoms and ear infections than children of nonsmokers

• Smoking major preventable cause of many respiratory diseases (cont'd)

–Air pollution, occupational exposure, asthma, and nonspecific airway hyperresponsiveness play role in development of COPD

Housing of the Lungs and Related Structures

• Lungs reside in thoracic cavity and are separated by region called mediastinum, which contains esophagus, heart, great vessels, and trachea

• Breathing in and out causes lungs to move within thoracic cavity

• To prevent irritation of lungs moving against thorax, each lung wrapped in sac or serous membrane called visceral pleura

Figure 13-15 Structures of the thoracic cavity.

• Thoracic cavity and upper side of diaphragm lined with continuation of membrane called parietal pleura

• Between these two pleural layers is pleural space (intrapleural space), which contains slippery liquid called pleural fluid that reduces friction as individual breathes

Pathology Connection: Pleural Space Problems

• Pneumothorax

–Air inside thoracic cavity but outside lungs

–Air can enter thoracic cavity from two directions

Stab wound or gunshot wound to chest would allow air to rush into thoracic cavity from outside

Lung might develop leak as result of structural deformity or disease process

• Pneumothorax

– If air cannot escape, it fills space meant for lungs and prevents lung expansion required for breathing

–Can be life-threatening situation

• Pleural effusion

–Buildup of fluid in pleural space between parietal and visceral pleura

–Fluid may be pus (empyema), serum from blood (hydrothorax), or blood (hemothorax)

–Fluids affected by gravity; pleural effusions tend to move to lowest point in pleural space

• Pleural effusion

– If effusion large enough, it can have same effect as a large pneumothorax, restricting lung expansion

–Pleural effusions can be treated by inserting chest tube inserted into pleura space to allow drainage of fluid

Figure 13-16 Pneumothorax (sucking chest wound) and technique for performing thoracocentesis.

The Lungs

• Lungs

–Conical-shaped with rounded peaks (apex) extending 1 to 2 inches above clavicle

–Base of lungs rest on right and left hemidiaphragm with right lung base a bit higher to accommodate liver

The Lungs

• Lungs

–Medial surface of lung has deep, concave cavity that holds heart, called cardiac impression, and is deeper on left side

The Lungs

• Lungs

–Hilum is area where root of each lung is attached, containing mainstem bronchus, pulmonary artery and vein, nerve tracts, and lymph vessels

The Lungs

• Lungs

–Right lung has three lobes: upper, middle, lower lobes; divided by horizontal and oblique fissures

– Left lung has one fissure, oblique fissure, and therefore has only two lobes: upper and lower lobes

– Lingula is area of left lung that corresponds with right middle lobe

The Lungs

• Lungs

– Left lung has only two lobes because largest part of heart is located in left lung area

–Right lung is larger, with 60% of gas exchange occurring here

The Protective Bony Thorax

• Bony thorax

–Bony and cartilaginous frame providing freedom of movement

–Protects organs of chest

– Includes rib cage, sternum, and thoracic vertebrae to which each rib attaches

–Sternum, or breastbone, is centrally located; comprised of manubrium, body, and xiphoid process (important landmark for CPR)

• Bony thorax

–12 pairs of ribs (thoracic cage)

True ribs (pairs 1–7): called vertebrosternal; connect to sternum and vertebrae

Pairs 8–10: called false ribs or vertebrocostal; connect to costal cartilage of superior rib and to thoracic vertebrae

• Bony thorax

–12 pairs of ribs

Ribs pairs 11 and 12: floating ribs, with no anterior attachment; only attach to vertebral column

Figure 13-17 The thoracic cage.

How We Breathe

• Respiratory control center is in medulla oblongata

• Inspiration: active process in which diaphragm is sent signal via phrenic nerve, causing it to contract and flatten downward, increasing thoracic cavity space

How We Breathe

• Increase in thoracic cavity volume decreases pressure, creating lower pressure in lungs than outside, allowing air to rush into lungs

Figure 13-18 How we breathe.

How We Breathe

• Ease of ventilation is called compliance

–High compliance: little effort required to expand lungs

– Low compliance: more difficult to expand lungs

–Emphysema can affect lung compliance

Bronchioles become damaged and wider, allowing air into lungs, increasing compliance but making it much more difficult to breathe out

How We Breathe

• Exhalation: passive act; diaphragm relaxes, which decreases amount of space in thoracic cavity; pressure in lungs becomes greater than atmospheric pressure; air is pushed out of lungs

• While we can consciously influence breathing rate, our breathing rate is normally controlled by level of carbon dioxide in blood

How We Breathe

• If carbon dioxide levels rise, it means that not enough CO2 is being ventilated

• When this occurs, chemoreceptors in medulla oblongata send signals to respiratory muscles to increase rate and depth of breathing

How We Breathe

• Other factors can change breathing rate

–Changes as we grow and mature into adults

–When we sleep, breathing rate slows down

–Rate increases with exercise or feel strong emotions

–Yawning

How We Breathe

• Accessory muscles include:

–Scalene muscles in neck

–Sternocleidomastoid

–Pectoralis major

–Pectoralis minor

How We Breathe

• While exhalation is usually passive, there are times when exhalation may need to be assisted, such as during certain diseases

• Accessory muscles of exhalation assist in more forceful and active exhalation by increasing abdominal pressure

How We Breathe

• Main accessory muscles of exhalation are abdominal muscles that push up diaphragm or the back muscles that pull down and compress thoracic cage

Figure 13-19 The accessory muscles of exhalation.

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Common Diseases of the Respiratory System

• Lung cancer

–Etiology: cause not known but linked to smoking and inhalation of carcinogenics

–Signs and symptoms: obstruction of airways interfering with ventilation, weight loss, weakness, cough, or change in cough

• Lung cancer

–Diagnostic tests: bronchoscopy, imaging studies, biopsy, sputum, patient exam and history

–Treatments: radiation, chemotherapy, and surgery

• Asbestosis

–Etiology: prolonged exposure to airborne asbestos particles

–Sign and symptoms: dyspnea, chest pain, productive cough in smokers, and decreased lung inflation

• Asbestosis

–Diagnostic tests: chest x-rays fine irregular linear infiltrates; honeycomb appearance on x-ray; decreased pulmonary function tests and hypoxemia

–Treatments: No cure; goal is to relieve symptoms and treat any complications such as infections

• Acute bronchitis

–Etiology: viral or bacterial

–Signs and symptoms: inflamed mucous membranes of trachea and bronchi; expectorating or dry cough, shortness of breath, fever, rales (raspy sound)

–Diagnostic tests: physical exam

–Treatment: antibiotics if bacterial

• Common cold

–Etiology: viral

–Signs and symptoms: upper airway congestion, cough, and sore throat

–Diagnostic tests: history and physical exam

–Treatments: treat symptoms, pain meds, bed rest, drink fluids, and proper nutrition

• Pharyngitis

–Signs and symptoms: red, sore swollen throat, and pus

–Diagnostic tests: history and physical exam, throat culture

–Treatments: if bacterial use antibiotics, antiseptic gargle

• Laryingitis

–Etiology: viral or bacterial, allergies, and over-use of voice

–Signs and symptoms: dysphonia, sore throat, and trouble swallowing

–Treatments: rest voice

• Tonsillitis

–Signs and symptoms: sore throat, swollen tonsils and dysphagia

–Diagnostic tests: history and physical exam, culture

–Treatments: antibiotics for bacterial, and surgery if needed

• Influenza

–Etiology: viral

–Signs and symptoms: fever, cough, body aches and headaches

–Treatments: rest, fluids, pain meds, and treat symptoms

• Pneumonia

–Etiology: viral, bacteria, or fungal

–Signs and symptoms: productive cough, chest pain, weakness, malaise, and dyspnea

• Pneumonia

–Diagnostic tests: imaging, blood work, and sputum culture

–Treatments: antibiotics if confirmed bacterial infection; antifungal drugs if confirmed fungal infection

• Pulmonary tuberculosis

–Etiology: bacterial

–Signs and symptoms: primary, may be asymptomatic; secondary, cough (may be blood tinged), fever (night sweats), weight loss

–Diagnostic tests: imaging, TB skin test, and sputum test

–Treatments: antibiotic agents

• Seasonal allergic rhinitis (hay fever)

–Etiology: allergic agents

–Signs and symptoms: upper airway congestion, watery nose and eyes, sneezing

–Diagnostic tests: history and physical exam, allergy testing

–Treatments: antihistamines, and preventative allergy shots

Allergic Rhinitis Video

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• Asthma

–Etiology: many triggers such as allergens, food, exercise, cold air, inhaled irritants, smoking

–Signs and symptoms: dyspnea, wheezing, productive cough, and hypoxia

• Asthma

–Diagnostic tests: history and physical exam, lung function tests

–Treatments: bronchodilators, steroids, anti-asthmatic agents; oxygen if needed

• COPD—chronic bronchitis

–Etiology: cigarette smoking and long-term exposure to air pollutants; middle or old age

–Signs and symptoms: dyspnea, wheezing, productive cough, and hypoxia

• COPD—chronic bronchitis

–Treatments: antibiotics if bacterial, bronchodilators, and oxygen if needed

• COPD—emphysema

–Etiology: cause not fully known but associated with smoking and one genetic form from alpha 1-antitrypsin deficiency

–Signs and symptoms: dyspnea, tachypnea, wheezing, productive cough, and hypoxia

• COPD—emphysema

–Treatments: oxygen therapy, bronchodilators, and alpha 1-antitrypsin replacement

• Acute respiratory distress syndrome (ARDS)

–Etiology: form of pulmonary edema; high mortality rate and very noncompliant (stiff) lungs; many causes; most often caused by shock, sepsis, and trauma

–Signs and symptoms: rapid shallow breathing with dyspnea; hypoxemia and fluid accumulation in lungs; rhonchi and crackles

–Diagnostic tests: arterial blood gases showing respiratory acidosis and severe hypoxemia, bilateral infiltrates on x-rays with white outs in lung fields

–Treatment: intubation and mechanical ventilation; sedatives and diuretics and in some cases high doses of corticosteroids

ARDS Animation

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• Cystic fibrosis

–Etiology: hereditary disease transmitted via recessive gene

–Signs and symptoms: excessive thick mucus secretion, repeated infections, large salt losses, and difficult digestion

• Cystic fibrosis

–Diagnostic tests: sweat test, and genetic testing

–Treatments: respiratory hygiene therapy, mucus thinning agents, antibiotics, and pancreatic enzyme supplements

Pharmacology Corner

• Oxygen

–Can be administered as medical treatment for respiratory and cardiovascular diseases

–Benefits of oxygen therapy

Reduces work of breathing

Increases oxygen content of blood

Reduces work of heart

Pharmacology Corner

• Drugs for airway narrowing

–Aerosolized bronchodilators: rapid relief of acute situation of airway narrowing

– Inhaled steroids: long-term treatment of chronic airway inflammation; less systemic effects than oral or injectable steroids

Pharmacology Corner

• Smoking cessation

–Only method known to prevent or slow progression of COPD is stop smoking or eliminate occupational source

–Tobacco dependence is powerful addiction

Most smokers require four to six attempts before successfully quitting

Even after quitting, some patients have lifelong cigarette craving

Pharmacology Corner

• Many patients require require behavioral counseling and encouragement in addition to pharmacological therapy to quit

–Nicotine replacement therapy

Forms of nicotine replacement include gum, skin patches, or inhaled forms

Drugs can be given to decrease desire such as Chantix™ or Wellbutrin™

Pharmacology Corner

• Surfactant

–Administered to premature infants whose lungs are underdeveloped and cannot produce their own surfactant

– Instilled into lungs

–Buys time for infant's lungs to complete development

Pharmacology Corner

• Systemic antibiotics: used for bacterial lung infections

• Inhaled insulin: can be used to treat diabetes

• Antiviral medications: reduce length and severity of viral infection (cold or flu)

Figure 13-20 Classes of drugs used to treat respiratory disorders.

Snapshots from the Journey

• Moving approximately 12,000 quarts of air each day, respiratory system is responsible for oxygenating blood; carries oxygen to tissue and removes carbon dioxide, waste product of cell metabolism

• Ventilation is movement of gas into alveoli, respiration is gas exchange that takes place in alveoli

• Lungs contain ever-branching airways called bronchi and bronchioles

• At end of each bronchiole are alveolar sacs

• Each alveolar sac is surrounded by capillaries where gas exchange occurs

• Purpose of upper airways is to filter, warm, and humidify air

• Olfaction (sense of smell) and phonation (speech) also occurs in upper airways

• Mucociliary escalator captures foreign particles and hairlike cilia constantly move layer of mucus up to upper airway to be swallowed or expelled

• Adenoids and tonsils aid in preventing pathogens from entering body

• Epiglottis protects airway to lungs from accidental aspiration of food and liquids

• Vocal cords are gateway between upper and lower airway

• Tracheobronchial tree is like upside-down tree with ever-branching airways where trunk of tree is trachea and leaves are alveoli

• Alveolar capillary membrane is where external respiration, or gas exchange, occurs

• Bony thorax provides support and protection for the respiratory system

• Main muscle of breathing is diaphragm, while accessory muscles assist in times of need such as exercise or disease

• Medulla oblongata is control center for breathing and sends impulses via the phrenic nerve to the diaphragm

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