Respiratory System (Chapter 6)

Respiratory System

All the structures of the body that contribute to the process of breathing, consisting of the upper and lower airways and their component parts

Respiratory System Parts

• Nose

• mouth

• Throat

• larynx

• trachea

• bronchi

• bronchioles

• lungs

• diaphragm

• Muscles used for breathing

Upper Airway

• Located anteriorly the the midline

• Nasopharynx

• Oropharynx

• Laryngopharynx

• Larynx (voice box)

Nasopharynx

• Where nostrils lead

• Warms, filters, and humidifies air

• Upper section of the pharynx that connects with the nasal cavity above the soft palate

Oropharynx

• Where air in mouth goes

• Less moist than nose air because it moves more rapidly

• Section of the pharynx at the back of the throat, from the soft palate to the U-shaped hyoid bone near the base of the tongue

Laryngopharynx

Where food and water diverge from air and proceed to esophagus and trachea respectively

Trachea

• wind pipe

• the main trunk for air passing to and from the lungs

• 5 inches long

• Composed of rings of cartilage open in the back which keep trachea from collapsing

Larynx (voice box)

• No solid or liquid material —> spasm of vocal cords/coughing

• Protected by epiglottis

Epiglottis

A thin, leaf-shaped valve that allows air to pass into the trachea but prevents food and liquid from entering the larynx

Lower Airway Structures

• Trachea

• Bronchial Tree

• Alveoli

• Lungs

Thyroid cartilage

A firm prominence of cartilage that forms the upper part of the larynx; the Adam’s apple

How larynx works

Tiny muscles open and close vocal cords and control tension on them. Sound is created as vocal cords vibrate from air being forced past them. Pitch changes as vocal cords open and close.

Cricoid Cartilage

A firm ridge of cartilage that forms the lower part of the larynx

Cricothyroid Membrane

A thin sheet of fascia that connects the thyroid and cricoid cartilages that make up the larynx

How are the lungs held in place?

• Trachea

• arteries

• veins

• pulmonary ligaments

Lung Lobes

• Right lung: upper, middle, lower

• Left Lung: upper and lower

Lungs supplied air by

right and left main stem bronchi

Bronchi

major air passages that diverge from the trachea

Bronchioles

any of the minute branches into which a bronchus divides

Alveoli

The air sacs of the lungs in which the exchange of oxygen and carbon dioxide takes place

• Where bronchioles end

Pleura

The serous membranes covering the lungs and lining the thorax, completely enclosing a potential space known as the pleural space

Visceral pleura

covers the lungs

parietal pleura

lines the chest wall

Pleural space

• The potential space between the parietal pleura and the visceral pleura

• described as “potential” because under normal conditions, the space does not exist.

How lungs work

• Chest wall expands

• lung is pulled with it due to pleural surfaces

Diaphragm

• A muscular dome that forms the undersurface of the horax, separating the chest from the abdominal cavity.

• Acts like skeletal and smooth muscles

• Contraction of this (and the chest wall muscles) brings air into the lungs.

• Relaxation allows air to be expelled from the lungs

Breathing Muscles

• Diaphragm

• neck (cervical) muscles

• intercostal muscles

• abdominal muscles

• pectoral muscles

Inhalation

• Chest Cavity enlarged by

  • Diaphragm & intercostal muscles contract

  • Diaphragm contracting enlarges thoracic cage

  • Intercostal muscles move ribs up and out

As volume of the chest cavity increases during inhalation

air rushes into the lungs

• Active because muscles are used

Exhalation

• Muscles relax

• Thorax dimensions decrease

• ribs and muscles resume resting positions

As volume of chest cavity decreases

air is pushed out through trachea

• passive

Functions of the Respiratory System

• Ventilation

• Respiration

Ventilation

• the movement of air between the lungs and the environment

• Requires chest rise and fall

Respiration

Process of mass exchange

• provides o2 and removes the waste product of co2

• controls blood pH

O2 & CO2 cycle

• O2 goes from red blood cells through capillary wall into tissues

• CO2 leaves tissues into blood stream

Diffusion

a passive process in which molecules move from an area with a higher concentration of molecules (oxygen in the air) to an area of lower concentration (oxygen in the bloodstream).

Brain & Breathing

• brainstem has nerves that act as CO2 sensors in blood and spinal fluid

• Controls breathing if CO2 and O2 are out of balance

Breathing is a result of

a buildup of carbon dioxide, which causes the pH to decrease in the cerebrospinal fluid (CSF)

Cerebrospinal Fluid

• Fluid produced in the ventricles of the brain that flows in the subarachnoid space and bathes the meninges

• Filters out impurities and toxins

Primary Reason to breathe

Lower CO2

CSF & Breathing

• When the level of carbon dioxide becomes too high, a slight change occurs in the pH (the measure of acidity) of the CSF

• The medulla oblongata (a portion of the brainstem), which is sensitive to pH changes, stimulates the phrenic nerve, sending a signal to the diaphragm to increase its rate of contraction

• diaphragm becomes more active, the respiratory rate and tidal volume increase

• As minute volume increases, more carbon dioxide is exhaled

Hypoxic Drive

• A “backup system” to control respiration

• senses drops n the oxygen level in the blood through brain, aorta walls, and carried arteries

• Less sensitive than the brainstem

Children’s Respiratory

• Smaller and less rigid

• Tongue takes up more space

• Smaller nose and mouth

• Easier for larynx to get obstructed

• Depend more on diaphragm

Medulla Oblongata

• Part of brainstem

• Makes breathing automatics without thinking

• control the rhythm of breathing

• initiates inspiration

• sets the base pattern for respirations

• sends signals down the phrenic nerve to the diaphragm, triggering it to contract

Pons

• Part of brainstem

• Augments respiration during emotional/physical stress

• Changes depth of inspiration/experation

Tidal Volume

Amount of air moved in and out of lungs during a single breath

• 500 mL in an adult

Inspiratory Reserve Volume

The amount of air that can be inhaled after a normal inhalation

Expiratory Reserve Volume

The amount of air that can be exhaled allowing a normal exhalation

Residual Volume

The air that remains in the lungs after maximal expiration

Dead Space

Any portion of the airway that does contain air and cannot participate in gas exchange, such as the trachea and bronchi

• ex: mouth, trachea, bronchi

Minute Volume

• amount of air that moves in and out of the lungs in one minute

• Respiratory rate x tidal volume

• helps determine if a patient is breathing adequately

Normal Breathing

• A normal rate and depth (tidal volume)

• A regular rhythm or pattern of inhalation and exhalation

• Clear, audible breath sounds on both sides of the chest

• Regular rise and fall movement on both sides of the chest

• Movement of the abdomen

Labored Breathing

The use of muscles of the chest, back, and abdomen to assist in expanding the chest; occurs when air movement is impaired

Signs of Labored breathing

• Muscle retractions above the clavicles, between the ribs, and below the rib cage, especially in children

• Pale or cyanotic (blue) skin

• Cool, damp (clammy) skin

• Tripod position (FIGURE 6-24), a position in which the patient leans forward onto two arms

Agonal Gasps

Abnormal breathing pattern characterized by slow, gasping breaths, sometimes seen in patients in cardiac arrest