Transcript Chapter 24 The Respiratory System

Chapter 24
The Respiratory System
• Cells continually use O2
& release CO2
• Respiratory system
designed for gas exchange
• Cardiovascular system
transports gases in blood
• Failure of either system
– rapid cell death from O2
starvation
Respiratory System Anatomy
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Nose
Pharynx = throat
Larynx = voicebox
Trachea = windpipe
Bronchi = airways
Lungs
Locations of infections
– upper respiratory tract is above vocal cords
– lower respiratory tract is below vocal cords
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External Nasal Structures
• Skin, nasal bones, & cartilage lined with mucous membrane
• Openings called external nares or nostrils
Nose -- Internal Structures
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Large chamber within the skull
Roof is made up of ethmoid and floor is hard palate
Internal nares (choanae) are openings to pharynx
Nasal septum is composed of bone & cartilage
Bony swelling or conchae on lateral walls
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Functions of the Nasal Structures
• Olfactory epithelium for sense of smell
• Pseudostratified ciliated columnar with goblet
cells lines nasal cavity
– warms air due to high vascularity
– mucous moistens air & traps dust
– cilia move mucous towards pharynx
• Paranasal sinuses open into nasal cavity
– found in ethmoid, sphenoid, frontal & maxillary
– lighten skull & resonate voice
Pharynx
• Muscular tube (5 inch long) hanging from
skull
– skeletal muscle & mucous membrane
• Extends from internal nares to cricoid
cartilage
• Functions
– passageway for food and air
– resonating chamber for speech production
– tonsil (lymphatic tissue) in the walls protects
entryway into body
• Distinct regions -- nasopharynx, oropharynx
Nasopharynx
• From choanae to soft palate
– openings of auditory (Eustachian) tubes from middle ear cavity
– adenoids or pharyngeal tonsil in roof
• Passageway for air only
– pseudostratified ciliated columnar epithelium with goblet
Oropharynx
• From soft palate to epiglottis
– fauces is opening from mouth into oropharynx
– palatine tonsils found in side walls, lingual tonsil in tongue
• Common passageway for food & air
– stratified squamous epithelium
Laryngopharynx
• Extends from epiglottis to cricoid cartilage
• Common passageway for food & air & ends as esophagus
inferiorly
– stratified squamous epithelium
Cartilages of the Larynx
• Thyroid cartilage forms Adam’s apple
• Epiglottis---leaf-shaped piece of elastic cartilage
– during swallowing, larynx moves upward
– epiglottis bends to cover glottis
• Cricoid cartilage---ring of cartilage attached to
top of trachea
• Pair of arytenoid cartilages sit upon cricoid
– many muscles responsible for their movement
– partially buried in vocal folds (true vocal cords)
Larynx
• Cartilage & connective tissue tube
• Anterior to C4 to C6
• Constructed of 3 single & 3 paired cartilages
Vocal Cords
• False vocal cords (ventricular folds) found above
vocal folds (true vocal cords)
• True vocal cords attach to arytenoid cartilages
The Structures of Voice Production
• True vocal cord contains both skeletal muscle
and an elastic ligament (vocal ligament)
• When 10 intrinsic muscles of the larynx
contract, move cartilages & stretch vocal cord
tight
• When air is pushed past tight ligament, sound
is produced (the longer & thicker vocal cord
in male produces a lower pitch of sound)
• The tighter the ligament, the higher the pitch
• To increase volume of sound, push air harder
Movement of Vocal Cords
• Opening and closing of the vocal folds occurs during
breathing and speech
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Trachea
• Size is 5 in long & 1in diameter
• Extends from larynx to T5 anterior to the
esophagus and then splits into bronchi
• Layers
– mucosa = pseudostratified columnar with cilia & goblet
– submucosa = loose connective tissue & seromucous
glands
– hyaline cartilage = 16 to 20 incomplete rings
• open side facing esophagus contains trachealis m. (smooth)
• internal ridge on last ring called carina
– adventitia binds it to other organs
Trachea and Bronchial Tree
• Full extent of airways is visible starting at the
larynx and trachea
Histology of the Trachea
• Ciliated pseudostratified columnar epithelium
• Hyaline cartilage as C-shaped structure closed by
trachealis muscle
Airway Epithelium
• Ciliated pseudostratified columnar epithelium with
goblet cells produce a moving mass of mucus.
Tracheostomy and Intubation
• Reestablishing airflow past an airway obstruction
– crushing injury to larynx or chest
– swelling that closes airway
– vomit or foreign object
• Tracheostomy is incision in trachea below cricoid
cartilage if larynx is obstructed
• Intubation is passing a tube from mouth or nose
through larynx and trachea
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Bronchi and Bronchioles
• Primary bronchi supply
each lung
• Secondary bronchi supply
each lobe of the lungs (3
right + 2 left)
• Tertiary bronchi supply
each bronchopulmonary
segment
• Repeated branchings
called bronchioles form a
bronchial tree
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Histology of Bronchial Tree
• Epithelium changes from pseudostratified ciliated
columnar to nonciliated simple cuboidal as pass
deeper into lungs
• Incomplete rings of cartilage replaced by rings of
smooth muscle & then connective tissue
– sympathetic NS & adrenal gland release epinephrine
that relaxes smooth muscle & dilates airways
– asthma attack or allergic reactions constrict distal
bronchiole smooth muscle
– nebulization therapy = inhale mist with chemicals that
relax muscle & reduce thickness of mucus
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Pleural Membranes & Pleural Cavity
• Visceral pleura covers lungs --- parietal pleura lines
ribcage & covers upper surface of diaphragm
• Pleural cavity is potential space between ribs & lungs
Gross Anatomy of Lungs
• Base, apex (cupula), costal surface, cardiac notch
• Oblique & horizontal fissure in right lung results in 3 lobes
• Oblique fissure only in left lung produces 2 lobes
Mediastinal Surface of Lungs
• Blood vessels & airways enter lungs at hilus
• Forms root of lungs
• Covered with pleura (parietal becomes visceral)
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Structures within a Lobule of Lung
• Branchings of single
arteriole, venule &
bronchiole are
wrapped by elastic CT
• Respiratory bronchiole
– simple squamous
• Alveolar ducts
surrounded by alveolar
sacs & alveoli
– sac is 2 or more alveoli
sharing a common
opening
Histology of Lung Tissue
Photomicrograph of
lung tissue showing
bronchioles, alveoli
and alveolar ducts.
Cells Types of the Alveoli
• Type I alveolar cells
– simple squamous cells where gas exchange occurs
• Type II alveolar cells (septal cells)
– free surface has microvilli
– secrete alveolar fluid containing surfactant
• Alveolar dust cells
– wandering macrophages remove debris
Alveolar-Capillary Membrane
• Respiratory membrane = 1/2 micron thick
• Exchange of gas from alveoli to blood
• 4 Layers of membrane to cross
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alveolar epithelial wall of type I cells
alveolar epithelial basement membrane
capillary basement membrane
endothelial cells of capillary
• Vast surface area = handball court
Details of Respiratory Membrane
• Find the 4 layers that comprise the respiratory
membrane
Double Blood Supply to the Lungs
• Deoxygenated blood arrives through
pulmonary trunk from the right ventricle
• Bronchial arteries branch off of the aorta to
supply oxygenated blood to lung tissue
• Venous drainage returns all blood to heart
• Less pressure in venous system
• Pulmonary blood vessels constrict in response
to low O2 levels so as not to pick up CO2 on
there way through the lungs
Breathing or Pulmonary Ventilation
• Air moves into lungs when pressure inside
lungs is less than atmospheric pressure
– How is this accomplished?
• Air moves out of the lungs when pressure
inside lungs is greater than atmospheric
pressure
– How is this accomplished?
• Atmospheric pressure = 1 atm or 760mm Hg
Boyle’s Law
• As the size of closed container decreases, pressure
inside is increased
• The molecules have less wall area to strike so the
pressure on each inch of area increases.
Dimensions of the Chest Cavity
• Breathing in requires muscular activity & chest size changes
• Contraction of the diaphragm flattens the dome and
increases the vertical dimension of the chest
Quiet Inspiration
• Diaphragm moves 1 cm & ribs lifted by muscles
• Intrathoracic pressure falls and 2-3 liters inhaled
Quiet Expiration
• Passive process with no muscle action
• Elastic recoil & surface tension in alveoli pulls inward
• Alveolar pressure increases & air is pushed out
Labored Breathing
• Forced expiration
– abdominal mm force
diaphragm up
– internal intercostals
depress ribs
• Forced inspiration
– sternocleidomastoid,
scalenes & pectoralis
minor lift chest
upwards as you gasp
for air
Intrathoracic
Pressures
• Always subatmospheric (756 mm Hg)
• As diaphragm contracts intrathoracic pressure decreases even
more (754 mm Hg)
• Helps keep parietal & visceral pleura stick together
Summary of Breathing
• Alveolar pressure decreases & air rushes in
• Alveolar pressure increases & air rushes out
Airway Resistance
• Resistance to airflow depends upon
airway size
– increase size of chest
• airways increase in diameter
– contract smooth muscles in airways
• decreases in diameter
Breathing Patterns
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Eupnea = normal quiet breathing
Apnea = temporary cessation of breathing
Dyspnea =difficult or labored breathing
Tachypnea = rapid breathing
Diaphragmatic breathing = descent of
diaphragm causes stomach to bulge during
inspiration
• Costal breathing = just rib activity involved
External Respiration
• Gases diffuse from areas
of high partial pressure to
areas of low partial
pressure
• Exchange of gas between
air & blood
• Deoxygenated blood
becomes saturated
• Compare gas movements
in pulmonary capillaries
to tissue capillaries
Internal Respiration
• Exchange of gases between
blood & tissues
• Conversion of oxygenated
blood into deoxygenated
• Observe diffusion of O2
inward
– at rest 25% of available O2
enters cells
– during exercise more O2 is
absorbed
• Observe diffusion of CO2
outward
Summary of Gas Exchange & Transport
Role of the Respiratory Center
• Respiratory mm.
controlled by neurons
in pons & medulla
• 3 groups of neurons
– medullary rhythmicity
– pneumotaxic
– apneustic centers
Location of the peripheral chemoreceptors
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Pneumotaxic & Apneustic Areas
• Pneumotaxic Area
– constant inhibitory impulses to inspiratory area
• neurons trying to turn off inspiration before lungs
too expanded
• Apneustic Area
– stimulatory signals to inspiratory area to
prolong inspiration
– if pneumotaxic area is sick
Regulation of Respiratory Center
• Cortical Influences
– voluntarily alter breathing patterns
– limitations are buildup of CO2 & H+ in blood
– inspiratory center is stimulated by increase in
either
– if you hold breathe until you faint----breathing
will resume
Chemical Regulation of Respiration
• Central chemoreceptors in medulla
– respond to changes in H+ or pCO2
– hypercapnia = slight increase in pCO2 is noticed
• Peripheral chemoreceptors
– respond to changes in H+ , pO2 or PCO2
– aortic body---in wall of aorta
• nerves join vagus
– carotid bodies--in walls of common carotid arteries
• nerves join glossopharyngeal nerve