Download Chapter 23 - Anatomy Freaks

C hapter 23
Respiratory System
23-1
Respiration
• Ventilation: Movement of air into and out
of lungs
• External respiration: Gas exchange between
air in lungs and blood
• Transport of oxygen and carbon dioxide in
the blood
• Internal respiration: Gas exchange between
the blood and tissues
23-2
Respiratory System Functions
• Gas exchange: Oxygen enters blood and carbon
dioxide leaves
• Regulation of blood pH: Altered by changing
blood carbon dioxide levels (increase C O2 = decrease pH)
• Voice production: Movement of air past vocal
folds makes sound and speech
• Olfaction: Smell occurs when airborne molecules
are drawn into nasal cavity
• P rotection: Against microorganisms by
preventing entry and removing them from
respiratory surfaces.
23-3
Respiratory System Divisions
• Upper tract: nose,
pharynx and
associated structures
• Lo w er tract: larynx,
trachea, bronchi, lungs
and the tubing within
the lungs
23-4
Nose (Nasus) and Nasal C avities
•
•
External nose (visible part – includes
hyaline cartilage plates & nasal bones )
N asal cavity
– From nares (nostrils) to choanae
(openings into the pharynx)
– Vestibule: just inside nares – lined
with stratified squamous epithelium –
continuous with skin
– Hard palate: floor of nasal cavity –
separates nasal cavity from oral cavity
– covered by mucous membrane
– N asal septum: partition dividing
cavity. Anterior cartilage; posterior
vomer and perpendicular plate of
ethmoid (divides nasal cavity into
right & left parts)
– C hoanae: bony ridges on lateral
walls with meatuses (passageways)
between. Openings to paranasal
sinuses and to nasolacrimal duct
23-5
Functions of Nasal C avity:
• Passageway for air
• C leans the air
(open even if mouth full of food)
[vestibule lined with hair & this traps particles /
mucous membrane consists of pseudostratified ciliated columnar epithelium with goblet cells
(mucus)]
• Humidifies
( moisture from mucous membranes & from excess tears that drains
into nasal cavity through nasolacrimal duct)
, warms air
( warm blood flowing
through mucous membranes - this prevents damage to respiratory passages caused by cold air)
• Smell
• Along with paranasal sinuses are
resonating chambers for speech
[superior part of nasal cavity consists of olfactory epithelium (sensory receptors)]
23-6
Pharynx:
• C ommon opening for digestive and
respiratory systems (connected to respiratory at larynx
& to digestive at esophagus)
• Three regions
– N asopharynx:
a. Pseudostratified columnar epithelium
with goblet cells.
b. Mucous and debris from nasal cavity is
swallowed.
c. Openings of Eustachian (auditory) tubes –
air that passes through them to equalize air
pressure between atmosphere & middle ear.
d. Floor is soft palate (separates
nasopharynx from oropharynx), uvula is
posterior extension of the soft palate –
prevents swallowed materials from entering
nasopharynx & nasal cavity
–Oropharynx: shared with digestive system (extends from soft palate to epiglottis). Lined
with moist stratified squamous epithelium – air, food, & drink passes through.
–Laryngopharynx: epiglottis to esophagus. Lined with moist stratified squamous
epithelium – food & drink pass through here to esophagus (very little air passes / 23-7
too much air = gas)
Larynx
23-8
Larynx -
base of tongue to trachea / passageway for air
• U npaired cartilages
– Thyroid: largest, Adam’s apple
– C ricoid: most inferior, base of larynx (other cartilages rest here)
– Epiglottis: attached to thyroid and has a flap near base of
tongue. Elastic rather than hyaline cartilage
• Paired
– Arytenoids: attached to cricoid
– C oniculate: attached to arytenoids
– C uneiform: contained in mucous membrane
• Ligaments extend from arytenoids to thyroid cartilage
– Vestibular folds or false vocal folds
– True vocal cords or vocal folds: sound production. Opening
between is glottis - laryngitis is an inflammation of mucosal epithelium of vocal folds
23-9
Functions of Larynx
• Maintain an open passageway for air movement: thyroid and cricoid
cartilages
• Epiglottis and vestibular folds prevent swallowed material from moving into
larynx – during swallowing, epiglottis covers the opening of larynx so, food & liquid slide over epiglottis
toward esophagus. Also, closure of vestibular folds can also prevent the passage of air----when person holds
breath.
• Vocal folds are primary source of sound production. Greater the amplitude of
vibration, louder the sound (force of air moving past vocal cords determines amplitude).
- Frequency of vibration determines pitch. Also, length of vibrating
segments of vocal folds affect-------ex: when only anterior parts of folds vibrate,
higher pitched tones are produced & when longer sections of vibrate, lower tones result.
- Arytenoid cartilages and skeletal muscles determine length of vocal
folds and also abduct the folds when not speaking (only breathing) to pull
them out of the way making glottis larger (allows greater movement of air).
• The pseudostratified ciliated columnar epithelium (lines larynx) traps debris,
preventing their entry into the lower respiratory tract.
23-10
Vocal Folds
23-11
Trachea - windpipe
• Membranous tube of dense regular connective tissue and smooth muscle;
supported by 15-20 hyaline cartilage C-shaped rings (protects & maintains open
passageway for air) . Posterior surface is devoid of cartilage & contains elastic
ligamentous membrane and bundles of smooth muscle called the trachealis.
C ontracts during coughing-----this causes air to move more rapidly through trachea, which helps
expel mucus & foreign objects.
• Inner lining: pseudostratified ciliated columnar epithelium with goblet cells.
Mucus traps debris, cilia push it superiorly toward larynx and pharynx.
Divides to form
– Left and right primary bronchi (each extends to a lung)
– C arina: cartilage at bifurcation (forms ridge). Membrane of carina especially
sensitive to irritation and inhaled objects initiate the cough reflex
23-12
Tracheobronchial Tree
and C onducting Zone
• Trachea to terminal bronchioles which
is ciliated for removal of debris.
– Trachea divides into two primary
bronchi. (right is larger in diameter & more in
line with trachea than left)
– Primary bronchi divide into
secondary (lobar) bronchi (one/lobe)
which then divide into tertiary
(segmental) bronchi.
– Bronchopulmonary segments:
defined by tertiary bronchi.
–Tertiary bronchi further subdivide into smaller and smaller bronchi then into
bronchioles (less than 1 mm in diameter), then finally into terminal
bronchioles.
• C artilage: holds tube system open; smooth muscle controls tube diameter----ex: during exercise, diameter increases, decreases resistance to airflow, increases volume of air moved
during asthma attack, diameter decreases, increases resistance to airflow, decreases volume of air flow
• As tubes become smaller, amount of cartilage decreases, amount of smooth
muscle increases------ex: terminal bronchioles have no cartilage & only have smooth muscle.
23-13
Respiratory Z one:
Respiratory Bronchioles to Alveoli
• Respiratory z one: site for gas
exchange
– Respiratory bronchioles branch
from terminal bronchioles.
Respiratory bronchioles have
very few alveoli (small, air filled
chambers where gas exchange between air &
blood takes place).
Give rise to
alveolar ducts which have more
alveoli. Alveolar ducts end as
alveolar sacs that have 2 or 3
alveoli at their terminus.
– Tissue surrounding alveoli
contains elastic fibers (alveoli expand
during inspiration & recoil during expiration)
– No cilia, but debris removed by
macrophages. Macrophages then
move into nearby lymphatics or
into terminal bronchioles.
23-14
The Respiratory Membrane
• Three types of cells in membrane.
– Type I pneumocytes. Thin squamous
epithelial cells, form 90% of surface of
alveolus. Gas exchange.
– Type I I pneumocytes. Round to cubeshaped secretory cells. Produce surfactant
(makes it easier for alveoli to expand during inspiration).
– D ust cells (phagocytes)
• Layers of the respiratory membrane
– Thin layer of fluid lining the alveolus
– Alveolar epithelium (simple squamous
epithelium
– Basement membrane of the alveolar
epithelium
– Thin interstitial space
– Basement membrane of the capillary
endothelium
– C apillary endothelium composed of
simple squamous epithelium
• Tissue surrounding alveoli contains elastic
fibers that contribute to recoil.
23-15
•
•
Lungs
Two lungs: Principal organs of respiration
– Base sits on diaphragm, apex at the top, hilus (hilum) on medial surface where
bronchi and blood vessels enter the lung. All the structures in hilus called root of the
lung.
– Right lung: three lobes. Lobes separated by fissures (deep & prominent)
– Left lung: Two lobes
– Right lung is larger & heavier than left
Divisions
– Lobes (supplied by secondary bronchi), each lobe is subdivided into
bronchopulmonary segments (supplied by tertiary bronchi and separated from one
another by connective tissue partitions), bronchopulmonary segments are subdivided
into lobules (supplied by bronchioles and separated by incomplete partitions).
–
–
Note: 9 bronchopulmonary segments present in left lung & 10 present right lung
Note: Individual diseased bronchopulmonary segments can be surgically removed, leaving the rest of lung
intact, because major blood vessels & bronchi do not cross connective tissue partitions.
23-16
Thoracic Wall
and Muscles of Respiration
23-17
Thoracic Wall
• Thoracic vertebrae, ribs, costal cartilages,
sternum and associated muscles
• Thoracic cavity: space enclosed by thoracic
wall and diaphragm
• Diaphragm separates thoracic cavity from
abdominal cavity
23-18
Inspiration and Expiration
• Inspiration: diaphragm, external intercostals, pectoralis minor, scalenes
– D iaphragm: dome-shaped with base of dome attached to inner
circumference of inferior thoracic cage. C entral tendon: top of
dome which is a flat sheet of connective tissue.
• Q uiet inspiration: accounts for 2/3 of increase in size of
thoracic volume. Inferior movement of central tendon and
flattening of dome. Abdominal muscles relax
– Other muscles: elevate ribs and costal cartilages allow lateral rib
movement
• Expiration: muscles that depress the ribs and sternum: such as the
abdominal muscles and internal intercostals.
• Q uiet expiration: relaxation of diaphragm and external
intercostals with contraction of abdominal muscles
• Labored breathing: all inspiratory muscles are active and contract
more forcefully. Expiration is rapid
23-19
Effect of Rib and Sternum
23-20
Pleura
• P leural cavity surrounds
each lung and is formed by
the pleural membranes.
Filled with pleural fluid.
• Visceral pleura: adherent
to lung. Simple squamous
epithelium, serous.
• P arietal pleura: adherent
to internal thoracic wall.
• Pleural fluid: acts as a lubricant and helps hold the two
membranes close together (adhesion).
• M ediastinum: central region, contains contents of thoracic
cavity except for lungs.
23-21
Blood and Lymphatic S upply
• Two sources of blood to lungs: Pulmonary & Bronchial
– Pulmonary artery brings deoxygenated blood to lungs from right side of
heart to be oxygenated in capillary beds that surround the alveoli.
Blood leaves via the pulmonary veins and returns to the left side of the
heart.
– Bronchial arteries provide oxygenated systemic blood to lung tissue.
They arise from the aorta & run along the branching bronchi. Part of
this now deoxygenated blood exits through the bronchial veins to the
azygous (drains chest muscles); part merges with blood of alveolar capillaries
and returns to left side of heart.
– Blood going to left side of heart via pulmonary veins carries primarily
oxygenated blood, but also some deoxygenated blood from the supply
of the walls of the conducting and respiratory zone.
• Two lymphatic supplies: superficial and deep lymphatic
vessels. Exit from hilus
–
–
–
–
Superficial drain superficial lung tissue and visceral pleura
Deep drain bronchi and associated C .T.
No lymphatics drain alveoli
Phagocytic cells within lungs phagocytize carbon particles & other
debris from inspired air & move them to lymphatic vessels
–
–
Older people & smokers lungs appear gray to black because accumulation of these particles
C ancer cells from lungs can spread to other parts of body through lymphatic vessels.
23-22
Ventilation
• Movement of air into and out of lungs
• Air moves from area of higher pressure to area of lower
pressure (requires a pressure gradient)
• If barometric pressure (atmospheric pressure) is greater than alveolar
pressure, then air flows into the alveoli.
• Boyle’s La w : P = k/V, where P = gas pressure,
V = volume, k = constant at a given temperature
• If diaphragm contracts, then size of alveoli increases.
Remember P is inversely proportionate to V; so as V gets
larger (when diaphragm contracts), then P in alveoli gets
smaller.
23-23
Alveolar Pressure C hanges: (Note: Barometric air pressure is
always
assigned a value of zero)
23-24