Respiratory System
Chapter 21
Human Anatomy
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One will die without oxygen in a matter of minutes. To avoid death the respiratory
system brings oxygen into the body and the circulatory system delivers it to the
tissues. The function of the respiratory system is to provide the body with oxygen
and get rid of carbon dioxide. This system is also involved with vocalization and
smell.
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I. Functional Anatomy and Respiratory SystemWe will look at the components necessary for the four steps of respiration:
1. Pulmonary ventilation- Applying inhaling mechanisms to bring oxygen into the
lungs
•
2. External respiration- Transferring oxygen from the lungs to the blood and
removing carbon dioxide from the blood so it enters the lungs.
•
3. Transport of respiratory gases- Using the circulatory system to transport the
oxygen to the tissues and to bring carbon dioxide to the lungs.
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4. Internal respiration-exchange of oxygen from blood to tissue cells at the
capillaries and of carbon dioxide from tissue cells to the blood.
Structures of the respiratory system are divided into the respiratory zone
(structures involved in gas exchange) and conducting zone (passage ways for air
to travel to the lungs).
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5. Cellular respiration- the use of oxygen byt he cell’s mitochondria to
metabolize nutrients for energy
• Structures
of the
respiratory
system are
divided into
respiratory
zone
(structures
involved in
gas
exchange)
and
conducting
zones
(passage
ways for air
to travel to
the lungs).
• A. The nose and
Paranasal SinusesThese two structures are
within the conducting
zone
• 1. The nose- has three
major functions: air
treatment, voice
resonance, and smell. It
is divided into the external
nose and nose cavity.
• a. Nose functions: airway
for respiration, warms,
moistens, and filters the
air, serves as a resonating
chamber for speech, and
contains the olfactory
receptors for smell.
• b. External nose: frontal
bone (nose root) and
nasal bone (nose
bridge), sphenoid and
ethmoid (nose roof),
maxillary bones for the
sides and hyaline
cartilage forming the
lateral, septal, and alar
cartilage inferiorly (also
see page 149 & 159).
Dense connective tissue
forms the inferior lateral
side of the nostrils
(external nares). Skin
covers the surface of the
external nose.
•
c. Nasal Cavity: formed by the
inner side of the external nose
and lies posterior to it. It is
divided into left and right by the
nasal septum (formed by:
ethmoid bone, vomer, and
septal cartilage).
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When air first enters it passes
through the external nares and
the vestibule (area superior to
nostrils). Air then enters the
nasal cavity which contains
nasal hairs to filter out small
particles. The cavity continues
into the nasopharynx via the
internal nares (nasal conchae).
The nasal cavity is lined with
epithelial tissue that makes a
mucus membrane called
olfactory mucosa because it
has smell receptors. All other
mucus membranes that line
respiratory structures are called
respiratory mucosa.
).
•
The nose cavity also contains the superior, middle, and inferior nasal
conchae. The conchae are spiral projections of bone and the meatus are
grooves in between the conchae. As air rushes into the nose it moves
through the conchae and this helps to increase its contact with mucus
membranes which helps to trap particles in the air. The conchae also
heat and moisten inhale air and reclaim heat and moisture from exhaled
air. These structures also improve our sense of smell.
•Respiratory mucosa is made up of pseudostratified ciliated
columnar cells that also have goblet cells for mucus production and
serous cells for production of liquid containing lysozyme. This forms
a thin sheet of mucus that lines the respiratory tract trapping
particles and moistening the air. The mucus traps particles and the
cilia beat to gently move the mucus out of the respiratory tract.
• 2. The paranasal
Sinuses- mucosa
lined air filled
cavities that
surround the nasal
cavity and open into
it. They are located
in the maxillary,
sphenoid, ethmoid,
and frontal bone.
They treat the air
like the nasal cavity
does and they drain
into the nasal cavity.
See page 163 and
study disarticulated
skulls in lab.
• B. The pharynx- muscular
passage way that connects
the nasal cavity to the
mouth and runs posterior to
the mouth to connect to the
larynx. It can be divided into
three sections:
• 1. Nasopharynx- cavity
directly posterior to nasal
cavity, it is lined with pseudo
stratified ciliated columnar
epithelium. During
swallowing it is closed off by
the soft palate and the uvula
to prevent food from
entering the nasal cavity.
This area also contains the
pharyngeal tonsils.
• 2. Oropharynxlies posterior to the
oral cavity and
connects to it
through the
fauces, it runs from
the soft palate to
the epiglottis. It is
lined with stratified
squamous
epithelium. When
food is swallowed
it passes through
the oropharynx to
enter the
esophagus. This
area also contains
the palatine tonsils
and the lingual
tonsils.
• 3. Laryngopharynxinferior to the
oropharynx it is
continuous with the
esophagus and the
larynx, thus it allows
both food and air to
pass by. It is lined
with stratified
squamous epithelium.
• C. The larynx- small area also called the voice box that
attaches to the hyoid bone, opens into the
laryngopharynx, and ends at the trachea. It routes the air
and food and produces one’s voice. It is composed of
nine cartilage pieces, the largest is the thyroid cartilage.
The thryroid cartilage has a ridge called the laryngeal
prominence which is seen as the Adam’s apple. The
larynx also contains the cricoid cartilage, and it has three
other cartilages that anchor the vocal cords. The final
cartilage piece is the epiglottis which helps to direct food
and air into the correct passage way.
• 1. Swallowing- when one swallows the larynx is pulled
superiorly and the epiglottis covers the opening to the
larynx thus food is steered into the esophagus. The
position of the larynx is optimal for voice production but
also increases the chances of choking. When food
enters the larynx it stimulates the cough reflex and it can
be released from this area. However, sometimes food
moves in to the respiratory tract far enough to cause the
person to choke to death.
• 1. Voice production- The vocal cords are formed by ligament
bands and are called true vocal cords, the space between is the
rima glottidis and together they make up the glottis. Directly superior
to these lies the false vocal cords which are mucosal folds not
involved in sound production but enhance high frequency sounds.
exhaled air make the cords vibrate and produce sounds, pitch is
varied by tightening (high pitch- faster vibration) or loosening (low
pitch-slower vibration) the vocal cords. Men have longer cords
because of a large pharynx thus they vibrate slower and produce
lower pitch sounds. Loudness depends on how fast air rushes
through. Structures involved in voice resonance are the pharynx
length, sinuses, and nasal cavity. The structures involved in shaping
soud are the pharynx, tongue, soft palate, and lips enhance voice
quality. Hoarseness is caused by inflammation of the vocal cords or
interruption to normal innervation.
• 2. Sphincter function of larynx- vocal cords can prevent passage
of air thus no exhalation occurs. This is mostly activated when one
contracts the abdominal muscle to increase abnominal pressure
such as is needed when lifting and straining to defecate.
• 3. Innervation of the larynx- the vagus nerve reaches the larynx
and damage to it disrupts speech. The path of the nerves that reach
the larynx runs below the apex of the lungs, lung cancer can
compress the nerve and cause hoarseness.
• D. The trachea- This structure is also known as
the windpipe. It runs from the larynx to the
bronchus. It has 16-20 C shaped cartilaged
rings held together by fibroelastic connective
tissue that prevents the trachea from collapsing.
It is adjacent to the esophagus and the open “C”
part faces the esophagus, it is lined with smooth
muscle. The entire trachea is lined with
pseudostratified ciliated columnar epithelium.
The trachea can be divided into three layers:
mucosa (inner epithlium), submucosa( goblet
cells and serous cells), and adventitia (contains
hyaline cartilage). At the carina the trachea
branches into the bronchi.
• E. The bronchi and subdivisions: the bronchial tree- The bronchi
are extensions of the trachea that divide into left and right to enter
the corresponding lung. As they branch they become more and
more narrow.
• 1. Bronchi in the conducting zone- The primary bronchus has the
largest diameter and is the tube that first divides into left and right
bronchus. The right is wider and shorter than the left. They enter
the lungs at the hilus (medial depression). Once in the lungs the
primary bronchi divide into secondary bronchi (lobar bronchi), three
on the right and two of the left. The secondary bronchi divide into the
tertiary bronchi (segmented bronchi) which continue to divide into
more numerous but narrower branches. The bronchioles are the
smallest and most narrow and do not contain cartilage. The terminal
bronchioles are yet smaller, they end at the respiratory bronchioles.
All aspect of the bronchi are lined with smooth muscle which
constricts to reduce air flow or relaxes to increase air flow. As the
branching continues the epithelial tissue also changes, as the
bronchi branch the tissue it becomes thinner and is not ciliated.
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2. The respiratory zone- The conducting zone is made up by all the
components tha carry the air into the lungs, the cite of gas exchange is the
respiratory zone. At the end of the respiratory tree is the alveoli which
makes up the lungs. The terminal bronchioles lead into the respiratory
bronchioles which contain scattered alveoli the respiratory bronchioles end
at the alveolar ducts that connect to the alveolar sacs ( a group of alveoli).
Alveoli provide a large surface area for gas exchange, about 1500 square
feet.
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a. Alveolar structure: each alveolus is made up of a single squamous
epithelial cell layer called Type I cells. They are in close contact with
capillaries. The type I cell walls and the capillary cell walls together form
the respiratory membrane. This thin membranes allows for diffusion of
gasses to happen easily. The type II cells are cuboidal epithelial cells that
are scattered throughout the Type I and release surfactant. This substance
is a detergent-like material that prevents the alveiolar cells from sticking
together.
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b. Alveolar significant features: Alveoli are surrounded by elastic fibers.
Alveolar pores connect adjacent alveoli to equalize pressure throughout the
lung. Particles that managed to get to the lungs are removed by alveolar
macrophages that circulate through air spaces (dust cells).
• F. The lungs and pleurae:
these are membranes that
line the lungs and pleural
cavity.
• 1. The pleura- a serous
membrance sac surrounds
the lungs (pleura) within the
pleural compartment; the
heart, trachea, and primary
bronchi lie within the
medistinum. The parietal
layer is on the outer surface
and covers the entire
surfaces of the thoracic
cavity. The pleural cavity is
a space between the
parietal and visceral layer
that is filled with pleural
fluid, thus reducing friction
and allowing the lungs to
adhere to the thoracic wall.
Close to the lung lies the
visceral layer.
• 2. Gross Anatomy of the lungs- the lungs are light, spongy, elastic
organs that weight about 1.25 lbs. The walls of the lungs are in
contact with the ribs. The lungs have an apex, a base, and a hilus at
which the bronchi and pulmonary veins and arteries enter. The left
lung has the cardiac notch in order to make room for the heart apex,
it also has two lobes (upper and lower) separated by the oblique
fissure. The right lung is larger and has three lobes (upper, middle,
and lower) separated by the horizontal and oblique fissure. The
lobes are further divided into bronchopulmonary segments (see
page 597.)
• 3. Blood supply and innervation- Pulmonary arteries lie posterior
to the bronchi and branch in the same manner as the bronchi, they
end at the pulmonary capillary networks the surround the alveoli.
Oxygenated blood is carried by the pulmonary veins which lie
anterior to the bronchi. Lung tissuehas its own blood supply that
drains into bronchial arteries and veins. The nerves that control lung
activity make up the pulmonary plexus. The sympathetic division
dilates tubes, the parasympathetic division constrict tubes, and
visceral sensory fibers send signals about sensation in the lungs.
Anterior view of lungs
Medial view of lungs
• II. Ventilation
•
This includes the mechanism for breathing and how it is
regulated by the brain.
• A. The mechanism of ventilation- breathing consist of two phases
and involves the intercostals muscles and the diaphragm.
• 1. Inspiration: to inhale the volume of the thoracic cavity is
increased by expanding it causing the pressure within it to drop.
Contraction of the diaphragm (“flattens” the diaphragm/moves
inferior) and external intercostals (raise the ribs) increases the cavity
size. As the pressure decreases air rushes in to fill the lungs.
• 2. Expiration: a normal exhale results from the reverse process of
inspiration and occurs just by allowing the diaphragm and the
intercostals muscles to relax. When the size of the cavity decreases
pressure increases and air rushes out of the lungs. In forceful
exhaling some abdominal and back muscles are contracted to
create more pressure.
• B. Neural control of ventilation- respiration is controlled in the
medulla oblongata, the rhythum can be influenced by emotions or by
chemoreceptors in the medulla or aortic bodies that sense a drop of
oxygen in the blood
• III. Disroders of the respiratory system-read on your own and
ask questions in lecture. Go over the section on lung cancer
(pg 60-605)
Healthy Lung
Emphysema
Lung Cancer