Chapter 13



Chapter 13

Respiratory System

1. 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.

2. 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

3. Organs of the Respiratory System:

a. Nose

b. Pharynx

c. Larynx

d. Trachea

e. Bronchi

f. Lungs – which contain alveoli (terminal air sacs)

4. 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

5. 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.

6. 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

7. 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.

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

8. 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?

9. 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.

10. 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

11. 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

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.

12. 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

13. Bronchioles

a. Smallest branches of the bronchi

b. Terminal bronchioles end in alveoli

14. Alveoli

a. Gas exchange takes place within the alveoli in the respiratory membrane

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

v. Hiccup - spasms of the diaphragm; sounds come from the air hitting the vocal folds of the glottis

21. 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

22. 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).

23. 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

24. 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

25. 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

26. 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

27. 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

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

28. 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

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