CH. 14 Respiratory system

I. THE RESPIRATORY SYSTEM-functions by supplying the body with oxygen and
removing
carbon dioxide from the body. Respiration occurs through five Processes:
A. Pulmonary Ventilation-movement of air into and out of the lungs.
B. External Respiration-movement of oxygen from the lungs to the blood and of
carbon
dioxide from the blood to the lungs.
C. Transport of Respiratory Gases-the movement of oxygen and carbon dioxide
between the
lungs and tissues. This is carried out by the cardiovascular system.
D. Internal Respiration-movement of oxygen from blood to the tissue cells and of
carbon
dioxide from tissue cells to blood.
E. Aerobic Respiration-the use of oxygen and production of carbon dioxide during
ATP
production.
II. GENERAL ANATOMY OF THE RESPIRATORY SYSTEM
A. The Major Structures that make up the Respiratory System Include:
1. The Nose, and Nasal Cavity 5. Bronchi and their smaller
branches
2. The Larynx 6. The Lungs with their
alveoli
3. The Pharynx 7. The Paranasal sinuses
4. The Trachea
III. THE NOSE AND PARANASAL SINUSES
A. The nose is the only visible portion of the Respiratory System. The nose provides
an
airway for respiration, moistens and warms air, filters and cleans inspired air,
serves
as a resonating chamber for speech and houses the olfactory receptors.
B. The structures of the nose are divided into the external nose and the internal
nasal
cavity.
C. Major External Features of the Nose Include: the root, bridge, dorsum nasi, apex,
philtrum, and the nostrils or external nares.
1. The external nose is formed by the Nasal Bones and Elastic Cartilage.
D. The Internal Nasal Cavity-in and posterior to the external nose.
1. Air enters this cavity by passing through the nostrils (external nares).
2. This cavity is divided by a midline known as the Nasal Septum, which is
formed
by the vomer bone, the perpendicular plate of the ethmoid and cartilage.
The
ethmoid forms the roof of the nasal cavity and the palate forms the base of
the

cavity. The Nasal Septum divides the internal portion of the nose into two
distinct
cavities.
3. Three nasal conchae extend from the lateral walls of each nasal cavity.
These
increase surface area and they create a vacuum in each nasal cavity.
4. Olfactory mucosa-lines much of the nasal cavity. This contains smell
receptors.
5. Respiratory mucosa-also lines much of the nasal cavity. This mucosa is
made up
of pseudostratified ciliated columnar epithelial tissue.
a. Goblet cells are also abundant in the respiratory mucosa. The mucus
traps
microorganisms that enter the nasal cavities.
b. Capillaries and thin-walled veins are abundant beneath these
mucosa
layers. These vessels act to warm incoming air as it flows over the
mucosa. Epistaxis-nosebleeds.
6. Paranasal Sinuses-surround the nasal cavity. These lighten the skull and
aid in
warming and moistening incoming air. These also produce mucus that
flows into
the nasal cavity. The paranasal cavities are located in the frontal, sphenoid,
ethmoid, and maxillary bones. The sinuses can also serve in speech
modulation.
IV. THE PHARYNX-the throat; a funnel-shaped tube that connects the nasal cavity and
mouth
superiorly to the larynx and esophagus inferiorly.
A. The Pharynx is divided into three major regions:
1. The Nasopharynx-posterior to the nasal cavity, this serves only as an air
passageway.
a. During swallowing, the uvula moves to close off the nasopharynx;
thus
preventing food from moving into the nasal cavity.
b. Pharyngeal tonsil (Adenoid)-located on the posterior wall of the
nasopharynx. These trap and destroy pathogens entering the
nasopharynx
via air. If these become enlarged, they can block the flow of air
through
the nose and into the throat. As a result, the air is not properly
warmed
before it enters the lungs. The person may breathe with their mouth
open.
c. Auditory (Eustachian) Tubes-these drain the middle ear cavity to
equalize
pressure in the ear with atmospheric pressure.

2. The Oropharynx-posterior to the oral cavity, opens into the mouth through
the
fauces. Both swallowed food and inhaled air pass through here.
a. The Palatine Tonsils-in the posterior wall of the oral cavity.
b. The Lingual Tonsil-covers the base of the tongue.
3. The Laryngopharynx-opens into the larynx. Is also a passageway for food and
air.
a. This structure is continuous with the esophagus (tube that carries food
to the stomach.
V. THE LARYNX-the voice box, lies at the upper end of the trachea, just below the pharynx.
A. This structure connects the pharynx and trachea. It is held in place by the hyoid bone.
B. 3 Functions of the Larynx:
1. Serves as an open airway
2. Routes food and air into the proper channels
3. Voice production
C. The larynx is composed of 9 cartilages that form a box-like structure. Most of these
are
hyaline cartilage. The three largest cartilages:
1. The Thyroid Cartilage-large, formed by 2 attached cartilage plates. This
structure is often
referred to as the Adam’s Apple.
2. The Cricoid Cartilage-sits atop and is anchored to the trachea.
3. Epiglottis-flexible, composed of elastic cartilage and is covered by taste buds.
a. This cartilage attaches to the superior edge of the thyroid cartilage and
the epiglottis is free on its other borders
b. When air passes into the larynx, the epiglottis remains open. However,
during
swallowing, the larynx pulls the epiglottis superiorly to cover the glottis
(the
hollow opening between the vocal cords). This action keeps food out of
the larynx.
c. The cough reflex acts to expel any materials that slip pass the epiglottis.
E. The Vocal Cords
1. True Vocal Cords-folds of elastic fibers which are stretched across the opening
of
the larynx. These appear white because they are avascular. These folds
vibrate as air
rushes up from the lungs; thus, producing sound.
2. False Vocal Cords-superior to the true vocal cords. These do not produce
sound.
These are only involving in helping to close the glottis during swallowing.
F. Sound Production
1. As air is forced between the vocal cords, they vibrate and produce sound.
2. In general, the tenser the vocal cords, the higher the pitch. Longer, less tense
cords

produce lower pitch. In young males, the cords begin to thicken and enlarge
during
puberty. It is during this period that the male’s voice “cracks”.
G. Laryngitis-inflammation of the vocal folds. This produces changes in the voice
including
hoarseness.
VI. THE TRACHEA (Windpipe)-cylindrical tube that connects the larynx and the 2 primary
bronchi.
A. It is approximately 4 inches long and 2.5 cm in diameter. The wall of the trachea
consists of
a respiratory mucosa that contains cilia and goblet cells. The beating cilia and
mucus act to
trap microorganisms that enter the trachea.
1. Smoking inhibits the activity of and often destroys cilia in the trachea; thus
coughing
becomes the only means to remove mucus from the trachea
B. Externally, the Trachea is composed of 16-20 C-shaped rings of hyaline cartilage.
This structure
provides the trachea with its great flexibility which allows the esophagus to expand
during
swallowing.
VII. THE BRONCHI AND THE BRONCHIAL TREE-this is the area where respiratory structures
are
first encountered. The bronchial tree refers to the branched airways leading from the
trachea to
microscopic air sacs in the interior of the lungs.
A. The Primary Bronchi (Right and Left) are formed where the Trachea branches (near
C7).
1. One primary bronchus runs into each lung. The right primary bronchus is wider,
shorter and more vertical than the left; thus, it is a more common site for
objects to
become lodged.
B. Once inside the lungs, the primary bronchi branch to form Secondary Bronchi.
1. There are three of these in the right lung and two in the left lung.
2. Secondary Bronchi branch into smaller Tertiary Bronchi which branch
repeatedly
into smaller and smaller bronchi. There are about 23 orders of branching in the
bronchi. This branching is often known as the Bronchial Tree.
C. Passageways smaller than 1 mm are known as Bronchioles. The smallest of these
are known
as Terminal Bronchioles which terminate in tubes known as Alveolar Ducts.
1. Alveoli-air sacs at the ends of alveolar ducts. Alveoli form clusters known as
alveolar sacs. The walls of the alveoli are covered by a thin layer of simple
squamous
epithelial tissue.

a. Surfactant-is a chemical secreted into the alveoli which reduces the
attraction
of water molecules for each other. This allows the alveoli to open and fill
with
air.
b. Externally, the alveoli are covered by pulmonary capillaries. THE
ALVEOLI
ARE THE SITES OF EXCHANGE OF GASES BETWEEN THE AIR AND
BLOOD. There area about 3 million alveoli per lung.
VIII. THE LUNGS AND PLEURA-paired structures occupying much of the thoracic cavity.
A. Each cone-shaped lung occupies its own pleural cavity. The lungs are surrounded by
the rib
cage externally and the diaphragm inferiorly. The right and left lungs are separated
from
each other by the mediastinum.
1. Just deep to the clavicle is the apex (pointed tip) of the lung. The base of the
lung sits
on the diaphragm.
2. Hilum-located on the medial surface of the lung. Pulmonary blood vessels and
primary bronchi enter the lung through this opening.
B. The left lung is slightly smaller than the right lung.
1. The Left Lung-has an upper and lower lobe that are separated by an oblique
fissure.
2. The Right Lung-has 3 lobes-an upper lobe, middle lobe and lower lobe. The
horizontal fissure divides the upper and middle lobes, while the oblique fissure
divides the middle and lower lobes.
C. Blood Supply in the Lungs
1. Pulmonary Arteries-highly branched in the lungs, these carry ______________
blood into the lungs.
2. Capillary Networks-surround the alveoli. Oxygen diffuses into the blood through
these capillaries.
3. Pulmonary Veins-carry ___________ blood out of the lungs, back to the heart.
D. The Pleura-form a thin, protective, double layered serous membrane around each
lung.
1. 2 Layers makeup the Pleural Membrane:
a. The Parietal Pleura-covers the thoracic wall and superior portion of the
diaphragm.
b. The Visceral Pleura-covers the external surfaces of the lungs.
1) The space between these two membranes is referred to as the
pleural
cavity and it is filled with pleural fluid.
IX. BREATHING (PULMONARY VENTILATION)
A. Breathing consists of two phases: inspiration(the period when air flows into the
lungs) and
expiration (the period when gases exit the lungs).

B. Pressures Associated with Breathing
1. Atmospheric Pressure(Patm)-the pressure exerted by the air (gases)
surrounding the
body. At sea level, atmospheric pressure is 760 mm Hg (or 1 atm).
2. Intrapulmonary Pressure (Ppul) is the pressure in the alveoli. It rises and falls
with the phases of breathing, but it always eventually equalizes with
atmospheric pressure.
3. Intrapleural Pressure (Pip)-pressure in the pleural cavity. This is always about 4
mm
Hg less than Ppul; therefore, Pip is always negative relative to Ppul.
C. Pulmonary Ventilation-the process of breathing (inspiration and expiration).
Pulmonary
Ventilation occurs through two processes:
1. Inspiration-period when air flows into the lungs.
a. Quiet Inspiration-normal inspiration. Quiet Inspiration is produced by:
1) The Diaphragm-as this muscle contracts, it moves inferiorly and
flattens out. This increases the height (volume) of the thoracic
cavity.
2) Action of the Intercostal Muscles
a) As the external intercostals contract, they lift the rib cage
and
pull the sternum superiorly, thus increasing the volume of
the
thorax.
b) As volume increases in the thoracic cavity, the lungs are
stretched and intrapulmonary volume increases. As a
result,
Ppul drops. When this occurs, air (with oxygen) rushes into
the
lungs.
2. Expiration-period when air flows out of the lungs.
a. This is a passive process that depends more on lung elasticity than on
muscle
contraction.
b. As the inspiratory muscles relax and resume their resting state, the rib
cage
descends and the lungs recoil. This pushes air out of the lungs to the
atmosphere.
X. RESPIRATORY VOLUMES AND PULMONARY FUNCTION TESTS
A. There are four major respiratory volumes that influence the lungs: tidal volume,
inspiratory reserve volume, expiratory reserve volume and residual volume.
1. Tidal Volume (TV)-refers to the 500 ml. of air that moves into and out of the
lungs
during normal, quiet breathing.
2. Inspiratory Reserve Volume (IRV)-the amount of air that can be inspired forcibly
beyond the tidal volume (2100 ml to 3200 ml).

3. Expiratory Reserve Volume (ERV)-the amount of air that can be evacuated
from the
lungs after a tidal expiration (1000 ml to 1200 ml). Even after a strenuous
expiration,
about 1200 ml of air remains in the lungs-this volume of air is referred to as the
Residual Volume (RV).
B. Respiratory Capacities-are created by two or more lung volumes. The major
respiratory
capacities include:
1. Inspiratory Capacity (IC)-the total amount of air that can be inspired after a tidal
expiration.
2. Functional Residual Capacity (FRC)-this represents the amount of air remaining
in
the lungs after a tidal expiration.
3. Vital Capacity (VC)-the total amount of exchangeable air.
4. Total Lung Capacity (TLC)-sum of all the lung volumes and is normally 6000 ml
in males and slightly less in women.
C. Anatomical Dead Space-refers to air that fills respiratory passageways but never
contributes
to gas exchange in the alveoli (usually about 150 ml).
XI. INTERNAL RESPIRATION (CAPILLARY GAS EXCHANGE)-movement of oxygen from the
blood
to the tissue cells and of carbon dioxide from tissue cells to blood.
A. In this case the partial pressures and diffusion gradients are reversed from the
above
situation.
B. Oxygen pressure is always lower in tissues than in the surrounding systemic
arterial blood;
thus, oxygen moves from the alveoli into the blood. The case is reversed for
carbon
dioxide.
XII. TRANSPORT OF OXYGEN AND CARBON DIOXIDE BY THE BLOOD
A. Oxygen Transport
1. Oxygen is carried in the blood in 2 ways:
a. Attached to the red pigment hemoglobin within erythrocytes.
b. Dissolved in plasma. Only a small fraction of oxygen is carried in
this
manner since oxygen is poorly soluble in water.
2. Oxyhemoglobin (HbO2)-refers to the combination of oxygen and
hemogloobin.
B. Carbon Dioxide Transport
1. Normal body cells produce about 200 ml of CO2 every minute-exactly the
amount
excreted by the lungs. Blood transports CO2 from the tissue cells to the lungs
in
three forms:

a. Dissolved in plasma-about 10% of the CO2 is carried in this fashion.
b. Chemically bound to hemoglobin-about 20% of the CO2 is carried
bound to
hemoglobin (Carbaminohemoglobin).
c. As bicarbonate ion in plasma-about 70% of the CO2 is carried in this
form.
1) In erythrocytes, the enzyme carbonic anhydrase quickly converts
water and carbon dioxide into carbonic acid which quickly
dissociates to
form bicarbonate. Bicarbonate is the primary buffer in the
human body.
XIII. CONTROL OF RESPIRATION
A. The Medulla Oblongata-clusters of neurons in this portion of the brain play a major
role in
regulating respiration.
1. The Inspiratory Center-in the medulla. When neurons here fire, impulses are
sent to
the phrenic and intercostal nerves which force the diaphragm and the
intercostals muscles to contract. As a result, the thorax expands and air
rushes
into the lungs.
B. The Pons-also regulates respiration.
1. The Pneumotaxic Center (Pontine Respiratory Group)-sends impulses that
inhibit
the inspiratory center of the medulla. This portion of the pons acts to regulate
the
rhythm of breathing.
C. Factors influencing Breathing Rate and Depth
1. Breathing rate and depth are modified in response to changing body
demands. The
respiratory centers in the medulla and pons contain excitatory and inhibitory
neurons.
2. Pulmonary Irritant Reflexes
a. The accumulation of mucus, dirt and debris in the respiratory system
leads
to constriction of air passageways. This leads to a cough when the
material
accumulates in the lungs and sneezing when the materials gather in
the
nasal cavity.
3. Inflation Reflex-involves impulses from the brain that inhibit inspiration. This is
initiated by stretch receptors associated with the lungs.
4. Hyperventilation-occurs when the depth and rate of breathing are increased.
This
occurs due to an increase in CO2 levels in the blood.
XIV. DISORDERS OF THE RESPIRATORY SYSTEM

A. Atelectasis-collapsed lung.
B. Chronic Obstructive Pulmonary Disease (COPD)-long term obstruction of air flow.
Two
Types of COPD:
1. Bronchitis-inflammation of the bronchi which leads to excess mucus
production.
2. Emphysema-long term exposure to chemicals (especially nicotine) that leads
to
destruction of the alveoli.
C. Asthma-interruption of air flow that leads to wheezing and dyspnea (labored
breathing).
D. The Common Cold-infection of the upper respiratory system by the Rhino Virus.
E. Rhinitis, Laryngitis, Sinusitis-inflammation of the mucosa of the listed structures.
F. Influenza-viral infection of the respiratory system.
G. Pneumonia-acute inflammation of the alveoli. The alveoli become filled with fluid and
pathogens in this illness. This is a common cause of death among older individuals.
H. Pleurisy-inflammation of the membranes around the lungs. This leads to a decrease
in
pleural fluid which allows the two layers of the membrane to rub against each other.
This
creates a great deal of pain.
I. Tuberculosis-inflammation of the lungs caused by the bacterium Mycobacterium
tuberculosis. In this condition, lung tissue is replaced by dense connective tissue.
J. Pulmonary Edema-fluid accumulation in the lungs.
K. Pulmonary Embolism-blood clot that prevents blood from reaching a portion of
the lungs.
This may result in cardiac arrest.