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Chapter 17: Respiratory System Theory Lecture Outline

Objectives

1. Describe the functions of the respiratory system

2. Describe the structures and functions of the organs of respiration

3. Explain the breathing and respiratory process

4. Discuss how breathing is controlled by neural and chemical factors

5. Discuss respiratory disorders

6. Define the key words that relate to this chapter

Introduction

When the respiratory system is mentioned, people generally think of breathing, but this is only one of the activities of the respiratory system. The body cells need a continuous supply of oxygen for the metabolic processes that are necessary to maintain life. The respiratory system works with the circulatory system to provide this oxygen and to remove the waste products of metabolism. The respiratory system also helps to regulate the pH of the blood.

Respiratory System Functions

• Exchange of oxygen and carbon dioxide

o Respiration is the sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells; every 3 to 5 seconds, nerve impulses stimulate the breathing process which moves air through a series of passages into and out of the lungs exchanging gases between the lungs and the blood

• Production of sound

o Air expelled from the lungs passes over the vocal cords and produces sound

• Respiration

Respiration is the physical and chemical processes by which the body supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in the energy-producing reactions

a. External respiration

1. Also known as breathing, or ventilation

2. Exchange of oxygen and carbon dioxide between the lungs and the blood in the surrounding capillaries

3. Breathing process consists of inspiration (inhalation) and expiration (exhalation)

b. Internal respiration

o Exchange of carbon dioxide and oxygen between the cells and the lymph surrounding them, plus the oxidative process of energy in the cells

c. Cellular respiration or oxidation

1. Chemical reactions within the cells which involves the use of oxygen to release energy stored in nutrient molecules such as glucose

2. Much of the energy released is in the form of heat to maintain body temperature

Respiratory Organs and Structures

The organs of the respiratory system are:

• Nasal cavity

• Pharynx

• Larynx

• Trachea

• Bronchi

• Bronchioles

• Alveoli

• Lungs

• Pleura

• Mediastinum

The Nasal Cavity

Lined with mucous membranes that filter dust and dirty particles; the air is also moistened by the mucus and warmed by blood vessels which supply the nasal cavity

• Anterior nares or nostrils

o Two oval openings in the nose where air enters the respiratory system

• Nasal septum

o Divides the right and left chamber of the nasal cavity

• Turbinates or nasal conchae bone

a. Three nasal conchae bones that divide the nasal cavity into three narrow passageways

b. Increases the surface area of the nasal cavity causing turbulence in the flowing air

• Cilia

o Small hairs located at the front of the nares which entrap and prevent the entry of larger dirt particles

• Olfactory nerve

o Nerve endings that provide the sense of smell are located in the mucous membrane

• Sinuses

o Cavities of the skull filled with air in and around the nasal region

o Helps to warm and moisten air passing through them

o Give resonance to the voice

The Pharynx

Air leaves the nasal cavity and enters the pharynx

• Also called the throat

• Common passageway for food and air

• Subdivided

a. Nasopharynx – lies above and behind the soft palate

b. Oropharynx - extends from the soft palate, behind the mouth, to just above the hyoid bone

c. Laryngopharynx – located below the oropharynx and superior to the larynx

• Epiglottis

a. Flap of cartilage lying behind the tongue and in front of the entrance to the larynx (voice box)

b. During swallowing, the epiglottis folds back to cover the entrance to the larynx, preventing food and drink from entering the trachea

The Larynx

Located below the pharynx

• Also called voice box

o When air is expelled from the lungs it passes the vocal cords within the larynx; this sets off a vibration, creating sound

• Nine fibrocartilaginous plates form the laryngeal walls

• Mucous membrane lines the larynx continuous from the pharyngeal lining above to the tracheal lining below

• Glottis is the space between the vocal cords

The Trachea

• Also called windpipe

o A tubelike passage that extends from the larynx, passes in front of the esophagus, and continues to form the two bronchi

• Hyaline cartilage

o 15-20 C-shaped rings that are virtually non-collapsible, keeping the trachea open for the passage of oxygen into the lungs

• Mucous membrane and ciliated epithelium

a. Mucus entraps inhaled dust particles

b. Cilia sweeps dust-laden mucus upward to the pharynx to be dislodged by coughing

The Bronchi and the Bronchioles

• Right and left bronchus branch from the lower end of the trachea

• Bronchi subdivide into bronchioles

a. The divisions are Y-shaped in form

b. Similar in structure to the trachea with ciliated epithelium and ringed with hyaline cartilage

• Alveolar sacs (alveoli)

o Microscopic clusters of tiny air sacs formed at the end of each bronchiole

The Alveoli

• Sacs of single layer epithelial tissue

o There are about 500 million alveoli in the adult lung

• Surrounded by bed of capillaries

• Surfactant

a. Lines the inner surface of the alveoli

b. Helps to stabilize the alveoli and prevents their collapse

• Exchange of oxygen and carbon dioxide

o It is through the moist walls of both the alveoli and the capillaries that rapid exchange of carbon dioxide and oxygen occurs

The Lungs

Each lung is roughly cone shaped, rests on the diaphragm and extends upward just above the midpoint of the clavicle

• Separated by the mediastinum (a median septum or partition) and the heart

• Apex is top of each lung; broad lower part is base

o Base rests over the diaphragm

• Right lung has three lobes; left lung has two lobes

a. Right lung is larger and broader due to the hearts incline into the left side

b. The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue

The Pleura

• A thin, moist, slippery membrane of tough endothelial cells that covers lungs

• Each lung encased in double-walled sac

o Two pleura membranes

1. Visceral or pulmonary pleura lines the lungs

2. Parietal pleura lines the wall of the thorax

• Pleural fluid

a. Produced by the pleura

b. Fluid is necessary to prevent friction between the two pleural membranes as they rub against each other during each breath

• Pleurisy is an inflammation of the pleura lining

• Pneumothorax

a. Another disorder that can affect the pleural cavity

b. Occurs if there is a buildup of air within the pleural cavity on one side of the chest causing it to collapse

• Thoracentesis

a. Procedure performed to drain excess fluid from the pleural cavity

b. Inflammation of the pleura can lead to an enormous quantity of serous fluid to build up

o Increased pleural fluid compresses and sometimes even causes parts of the lung to collapse

o Makes breathing extremely difficult

The Mediastinum

• Also called the interpleural space

• Located between the lungs and extends from the sternum to the vertebrae

• Contains the thoracic viscera

Mechanics of Breathing

• Pulmonary ventilation is called breathing

• Due to changes in pressure which occur within the chest cavity

o Variation in pressure caused by cellular respiration and mechanical breathing movements

The Breathing Process

• Inhalation/inspiration

a. During inhalation, or inspiration, the external intercostals lift the ribs upward and outward

b. As the diaphragm moves downward, pressure is exerted on the abdominal viscera which increases the space within the chest cavity in a vertical direction; as a result, there is a decrease in pressure allowing air to rush in all the way down to the alveoli

• Exhalation/expiration

a. Passive process where all the contracted intercostals muscles and diaphragm relax; the ribs move down and the diaphragm moves up

b. Increased internal pressure forces air form the lungs

c. Compliance is the ability of the lungs to change capacity as the size of the thoracic cavity is altered

• Respiratory movements and frequency of respiration

a. Inspiration and expiration combined is counted as one respiratory movement

o Normal rate in adults is about 14-20 breaths per minute

b. Situations that affect respiratory rate

1. Muscular activity

2. Increased body temperature

3. Pathological disorders such as hyperthyroidism

4. Emotions

5. Coughing

6. Hiccoughs (hiccups)

7. Sneezing

8. Yawning

Control of Breathing

Rate of breathing is controlled by:

• Neural (nervous) factors

a. Respiratory center is located in the medulla oblongata in the brain

b. During inflation, the nerve endings in the walls are stimulated sending a message to the medulla by way of the vagus nerve, inhibiting inspiration and stimulating expiration

o Prevents over-inflation of the lungs

• Chemical factors

a. Dependent upon the level of carbon dioxide in the blood

b. Respiratory center senses the increased carbon dioxide in the blood and increases the respiratory rate

Effects of Aging

• Lung tissue loses elasticity

• Rib cage becomes less flexible

• Muscle strength decreases

• Functioning alveoli decrease

Lung Capacity and Volume

To measure lung capacity use a device called a spirometer

o A spirometer measures the volume and flow of air during inspiration and expiration

• Tidal volume

o Amount of air that moves in and out of the lungs with each breath

(normal amount is about 500ml)

• Residual volume

o Amount of air that cannot be voluntarily expelled from the lungs

1. Allows for continuous exchange of gases between breaths

2. Normal residual volume is 1,500 ml

Types of Respiration

The following conditions describe various kinds and conditions of respiration

• Apnea

o Temporary stoppage of breathing movements

• Dyspnea

o Difficult, labored, or painful breathing, usually accompanied by discomfort and breathlessness

• Eupnea

o Normal or easy breathing with the usual quiet inhalations and exhalations

• Hyperpnea

o An increase in the depth and rate of breathing accompanied by abnormal exaggeration of respiratory movements

• Orthopnea

o Difficult or labored breathing when the body is in a horizontal position corrected by sitting or standing

• Tachypnea

o Abnormally rapid and shallow rate of breathing

• Hyperventilation

o Rapid breathing occurs which causes the body to lose CO2 too quickly leading to dizziness and possible fainting

Disorders of the respiratory system

• The respiratory system is subject to various infections and inflammations caused by bacteria, viruses and irritants

a. Respiratory illnesses account for approximately 50% of all acute illnesses

b. Respiratory infections account for over 80% of all infection

• Disorders Infectious Causes

a. Common cold

1. Caused by a virus that is highly contagious

2. Handwashing is the best preventive measure against the common cold

3. Colds generally run their course in seven days

b. Pharyngitis

o Red, inflamed throat which may be caused by one of several bacteria or viruses

c. Laryngitis

o Inflammation of the larynx, or voice box

d. Sinusitis

o Infection of the mucous membrane which lines the sinus cavities

e. Bronchitis and chronic bronchitis

1. Inflammation of the mucous membrane of the trachea and the bronchial tubes which produces excessive mucus

2. Chronic bronchitis (COPD) most commonly caused by cigarette smoking

f. Influenza (flu)

1. Viral infection characterized by inflammation of the mucous membrane of the respiratory system

2. Yearly vaccine is available

g. Pneumonia

1. Infection of the lung caused by a bacteria or virus

2. The alveoli become filled with a thick fluid called exudates which contains both pus and RBCs

h. Tuberculosis (TB)

o Infectious contagious disease of the lungs caused by Mycobacterium tuberculosis

i. Diphtheria

o Very infectious disease caused by the bacillus Corynebacterium diphtheriae

j. Pertussis (whooping cough)

o Characterized by severe coughing attacks that end in a “whooping” sound and dyspnea

k. Anthrax

o Disease-causing organism that can create a potential health hazard that can be fatal to humans and animals

l. Severe acute respiratory syndrome (SARS)

o Contagious disease that spreads quickly through direct contact with infected people, contact with fomites and airborne droplets

• Disorders Noninfectious Causes

Ailments unrelated to infectious causes

a. Rhinitis

o Inflammation of the nasal mucous membrane causing swelling and increased secretions

b. Asthma

o Disease in which the airway becomes obstructed due to an inflammatory response to a stimuli

c. Athelectasis

o Condition in which the lungs fail to expand normally due to bronchial occlusion

d. Chronic obstructive pulmonary disease (COPD)

1. Term that refers to lung disease such as chronic bronchitis, emphysema and asthmatic bronchitis

2. Emphysema characterized by the over-dilation of the alveoli causing a loss of elasticity that cannot rebound and eventually rupture

e. Caner of the lungs or larynx

f. Pulmonary embolism

1. Condition when a blood clot travels to the lung

2. Can occurs after surgery or if a person has been on bed rest

g. Sudden infant death syndrome (SIDS)

o Also known as crib death

o Cause is unknown; however, evidence suggests that there is a disturbance of the respiratory control center in the brain

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