CHAPTER 13
RESPIRATORY SYSTEM
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Introduction:
a. Our cells require an abundant supply of oxygen to carry out vital functions.
b. We cannot do without oxygen for even a little while, as we can without food or water.
Functions of the Respiratory System:
a. Oversees gas exchanges between the blood and external environment
b. Passageways to the lungs purify, warm, and humidify the incoming air
Organs of the Respiratory System:
a. Nose
b. Pharynx
c. Larynx
d. Trachea
e. Bronchi
f. Lungs – which contain alveoli (terminal air sacs)
The Nose (“pug” or “ski-jump” in shape)
a. The only externally visible part of the respiratory system
b. Air enters the nose through the external nares (NOSTRILS)
c. The inferior of the nose consists of a nasal cavity divided by a NASAL SEPTUM
Anatomy of the Nasal Cavity
a. Olfactory receptors are located in the mucosa on the superior surface
b. The rest of the cavity is lined with respiratory mucosa
i. Moistens air
ii. Traps incoming foreign particles
c. Lateral walls have projections called CONCHAE
i. Increases the surface area exposed to the air
ii. Increases air turbulence within the nasal cavity
d. The nasal cavity is separated from the oral cavity by the palate
i. Anterior hard palate (bone)
ii. Posterior soft palate (muscle)
e. DISORDER: Cleft Palate – A genetic defect due to the failure of the bones forming the palate to
fuse. It results in breathing difficulty as well as chewing and speaking.
Paranasal Sinuses
a. Cavities within bones surrounding the nasal cavity:
i. Frontal Bone
ii. Sphenoid Bone
iii. Ethmoid Bone
iv. Maxillary Bone
b. Functions of the sinuses:
i. Lighten the skull
ii. Act as resonance chambers for speech
iii. Produce mucus that drains into the nasal cavity
Pharynx (THROAT)
a. Muscular passage from nasal cavity to larynx
b. Three regions of the pharynx:
i. Nasopharynx = superior region behind nasal cavity
ii. Oropharynx = middle region behind mouth
iii. Laryngopharynx = inferior region attached to larynx
c. The nasopharynx is where air enters.
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d. The oropharynx and laryngopharynx are common passageways for air and food (food empties
into the esophagus).
e. Structures of the Pharynx:
i. Auditory tubes enter the nasopharynx
ii. Tonsils of the pharynx
1. Pharyngeal tonsil (adenoids) = in the nasopharynx
2. Palatine tonsils = in the oropharynx
3. Lingual tonsil = at the base of the tongue
Larynx (VOICE BOX)
a. Routes air and food into the proper channels
b. Plays a role in speech
c. Made of 8 rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (EPIGLOTTIS)
d. Structures of the Larynx:
i. Thyroid Cartilage
1. Larges hyaline cartilage
2. Protrudes anteriorly (ADAM’S APPLE)
ii. Epiglottis
1. Superior opening of the larynx
2. Routes food to the larynx and air toward the trachea
iii. Vocal Cords – vibrate with expelled air to create sound (speech)
iv. Glottis – opening between vocal cords
e. Place your hand midway on the anterior surface of the neck. Swallow. Can you feel the larynx
rising as you swallow?
Trachea (WINDPIPE)
a. Connects larynx with bronchi
b. Lined with ciliated mucosa
i. Beat continuously in the opposite direction of incoming air
ii. Expel mucus loaded with dust and other debris away from the lungs
c. Walls are reinforced with C-shaped hyaline cartilage - the open parts of the rings allow our
esophagus to expand when we swallow a large piece of food.
d. Smoking destroys the cilia within the trachea. Without these cilia, coughing is the only means of
preventing mucus from accumulating in the lungs.
e. Because the trachea is the only way air can enter the lungs, tracheal obstruction is life
threatening. Many people have suffocated after choking on a piece of food that suddenly closed
off the trachea. The Heimlich Maneuver, a procedure in which the air in a person’s own lungs
is used to “pop out,” or expel an obstructing piece of food, has saved the lives of many people.
Primary Bronchi
a. Right and Left primary bronchi are formed by division of the trachea
b. Right bronchus is wider, shorter, and straighter than the left and more common for an inhaled
foreign object to become lodged.
c. Bronchi subdivide into smaller and smaller branches
Lungs
a. Occupy most of the thoracic cavity
i. Apex – superior portion of each lung – near the clavicle
ii. Base – inferior portion – rests on the diaphragm
b. Each lung is divided into lobes by fissures:
i. Left lung = 2 lobes
ii. Right lung = 3 lobes
c. Coverings of the Lungs:
i. Pulmonary (Visceral) Pleura = covers the lung surface
ii. Parietal Pleura = lines the walls of the thoracic cavity
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iii. Pleural Fluid = fills the area between layers of pleura to allow gliding
d. DISORDER: Pleurisy – Inflammation of the pleura and can be caused by decreased secretion of
pleural fluid. The pleural surfaces become dry and rough, which results in friction and stabbing
pain with each breath.
After the primary bronchi enter the lungs, they subdivide into smaller branches which forms the
Respiratory Tree Divisions:
a. Primary Bronchi
b. Secondary Bronchi
c. Tertiary Bronchi
d. Bronchioles
e. Terminal Bronchioles
Bronchioles
a. Smallest branches of the bronchi
b. Terminal bronchioles end in alveoli
Alveoli
a. Gas exchange takes place within the alveoli in the respiratory membrane
Gas Exchange
a. Gas crosses the respiratory membrane by diffusion
i. Oxygen enters the blood
ii. Carbon dioxide enters the alveoli
b. Macrophages add protection
Respiratory Physiology:
a. The major function of the respiratory system is to supply the body with oxygen and to dispose of
carbon dioxide.
b. To do this, at least four events, collectively called RESPIRATION, must occur.
c. Events of Respiration:
i. Pulmonary ventilation - moving air in and out of the lungs (BREATHING)
ii. External respiration - gas exchange between pulmonary blood and alveoli
iii. Respiratory gas transport - transport of oxygen and carbon dioxide via the bloodstream
iv. Internal respiration - gas exchange between blood and tissue cells in the systemic
capillaries
Mechanics of Breathing - PULMONARY VENTILATION
a. Completely a mechanical process
b. 2 phases
i. Inspiration = flow of air into lungs
ii. Expiration = air leaving lungs
Inspiration:
a. Diaphragm and the muscles in between the ribs contract
b. The size of the thoracic cavity increases
c. External air is pulled into the lungs
Expiration or Exhalation:
a. As muscles relax, air is pushed out of the lungs
b. Forced expiration can occur mostly by contracting the internal rib muscles to depress the rib cage
Nonrespiratory Air Movements
a. Can be caused by reflexes or voluntary actions
b. Examples
i. Cough and Sneeze - clears lungs of debris
ii. Laughing - emotionally induced response
iii. Crying - emotionally induced mechanism
iv. Yawn - triggered by need to increase the amount of oxygen in the blood
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v. Hiccup - spasms of the diaphragm; sounds come from the air hitting the vocal folds of
the glottis
Respiratory Volumes and Capacities
a. Normal breathing moves about 500 ml of air with each breath (TIDAL VOLUME)
b. Many factors affect respiratory capacity:
i. A person’s size
ii. Sex
iii. Age
iv. Physical condition
Respiratory Sounds
a. Sounds are monitored with a stethoscope
b. Bronchial Sounds - produced by air rushing through the trachea and bronchi
c. Vesicular breathing sounds - soft sounds of air filling alveoli
d. Diseased respiratory tissue, mucus, or pus can produce abnormal sounds such as RALES (a
rasping sound) and WHEEZING (a whistling sound).
External Respiration
a. Oxygen movement INTO the blood
b. Carbon dioxide movement OUT of the blood
c. Blood leaving the lungs is OXYGEN RICH and CARBON DIOXIDE POOR
Internal Respiration
a. Exchange of gases between blood and body cells
b. An opposite reaction to what occurs in the lungs
i. Carbon dioxide diffuses OUT of tissue TO blood
ii. Oxygen diffuses FROM blood INTO tissue
Neural Regulation of Respiration
a. Activity of the respiratory muscles is transmitted to the brain by nerves
b. Neural centers that control rate and depth are located in the medulla
c. The pons appears to smooth out respiratory rate
d. Normal respiratory rate is 12 - 15 respirations per minute
Factors Influencing Respiratory Rate and Depth
a. Physical Factors
i. Increased Body Temperature
ii. Exercise
iii. Talking
iv. Coughing
b. Volition - conscious control
i. Holding the breath when swimming
ii. Breathing while singing
c. Emotional Factors
d. Chemical Factors
i. Carbon dioxide levels
1. Level of carbon dioxide in the blood is the main regulatory chemical for
respiration
2. Increased carbon dioxide increases respiration
ii. Oxygen levels
1. Changes in oxygen concentration in the blood are detected by chemoreceptors in
the aorta and carotid artery
Respiratory Disorders
a. Chronic Obstructive Pulmonary Disease (COPD)
i. Exemplified by chronic bronchitis and emphysema
ii. Major causes of death and disability in the United States
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iii. Features of these diseases
1. Patients almost always have a history of smoking
2. Labored breathing becomes progressively more severe
3. Coughing and frequent pulmonary infections are common
4. Most victims retain carbon dioxide
5. Those infected will ultimately develop respiratory failure
b. Emphysema
i. Alveoli enlarge
ii. Chronic inflammation promotes lung fibrosis
iii. Airways collapse during expiration
iv. Patients use a large amount of energy to exhale
v. Overinflation of the lungs leads to a permanently expanded barrel chest
c. Chronic Bronchitis
i. Mucosa of the lower respiratory passages becomes severely inflamed
ii. Mucus production increases
iii. Pooled mucus impairs ventilation and gas exchange
iv. Risk of lung infection increases
v. Pneumonia is common
d. Lung Cancer
i. Accounts for 1/3 of all cancer deaths in the United States
ii. Increased incidence associated with smoking
e. Sudden Infant Death Syndrome (SIDS)
i. Apparently healthy infant stops breathing and dies during sleep
ii. Some cases are thought to be a problem of the neural respiratory control center
iii. 1/3 of cases appear to be due to heart rhythm abnormalities
f. Asthma
i. Chronic inflamed hypersensitive bronchiole passages
ii. Response to irritants with coughing and wheezing
Developmental Aspects of the Respiratory System
a. Lungs are filled with fluid in the fetus
b. Lungs are not fully inflated with air until two weeks after birth
c. Important birth defects:
i. Cystic fibrosis – over-secretion of thick mucus clogs the respiratory system
ii. Cleft palate
d. Aging Effects:
i. Elasticity of lungs decreases
ii. Vital capacity decreases
iii. Blood oxygen levels decrease
iv. Stimulating effects of carbon dioxide decreases
v. More risks of respiratory tract infection
e. Respiratory Rate Changes Throughout Life:
i. Newborns - 40 to 80 respirations per minute
ii. Infants - 30 respirations per minute
iii. Age 5 - 25 respirations per minute
iv. Adults - 12 to 18 respirations per minute
v. Rate often increases somewhat with old age