Respiratory System Flashcards
Basic functions of the
respiratory system
Absorbs oxygen from air into blood
• Disposes of carbon dioxide into air from
blood
Respiratory organs
- Nose, nasal cavity, and paranasal sinuses
- Pharynx, larynx, and trachea
- Bronchi and bronchioles (smaller branches)
- Lungs and alveoli
Conduction & respiratory zones
Conducting zone: carries air to sites of gas exchange and filters, humidifies, and warms air as it is conducted through nose, mouth, throat, trachea and bronchi • Respiratory zone: actual site of gas exchange in the lungs in bronchioles, alveolar ducts, and alveolar sacs
The Nose (function)
Provides an airway for respiration • Moistens and warms air • Filters inhaled air • Resonating chamber for speech • Houses olfactory receptors
The Nose (Composition)
• Size variation due to differences in nasal hyaline cartilage
(septal cartilages & alar cartilages)
• Lateral border of nostril composed of dense fibrous
connective tissue
• Skin is thin—contains many sebaceous glands
The Nasal Cavity
• External nares—nostrils • Divided by nasal septum • Continuous with nasopharynx through choanae (posterior tunnel shaped nasal apertures)
Nasal Cavity
Olfactory Mucosa
- Near roof of nasal cavity
* Houses olfactory (smell) receptors
CN 1, Olfactory Nerve
CN I is sensory nerve of smell which runs through
cribiform plate of ethmoid bone
• Olfactory mucosa is near roof of nasal cavity
Nasal Respiratory mucosa
• Lines nasal cavity
• Epithelium is pseudostratified ciliated
columnar which moves mucous
• Goblet cells within epithlium
• Underlying layer of lamina propria (areolar
connective tissue) is richly supplied with
tubuloalveolar glands that contain both
mucous cells which produce sticky mucus
and serous cells that produce watery fluid
which contains digestive enzymes
Nasal Respiratory mucosa
• The sticky mucus covers the mucosal surface and
traps the inhaled bacteria, viruses, pollen, dust, &
other debris
• Each day, the nasal glands and the epithelial goblet
cells secrete about a liter of mucus which contains
a lysozyme enzyme that destroys and digests
bacteria and viruses
• The ciliated cells in the pseudostratified ciliated
columnar epithelial lining create a gentle current
that moves the mucus posteriorly to the pharynx
where it is swallowed and mixed with the digestive
enzymes in the stomach
Nasal Conchae (= turbinates)
• Superior and middle nasal conchae
– Part of the ethmoid bone
• Inferior nasal conchae
– Separate bone
Nasal conchae
• As inhaled air rushes over the curved
conchae, the resulting turbulence greatly
increases the amount of contact between
the nasal mucosa and the inhaled air
• This causes the air’s particulate matter to be
deflected onto the mucus-coated surfaces
• The conchae and nasal mucosa function
during inhalation to filter, heat, and moisten
the air
Paranasal sinuses: cavities in
cranial bones near the nose
Lined with mucosa and are typically filled
with air
• Extensions of the nasal cavity
• Connect to the nasal cavity through the
meatuses inferior to the conchae
• Help to humidify, warm, and filter inhaled air
• Lighten skull
• Sinusitis can develop when they become
infected and full of fluid
Paranasal sinuses: cavities in
cranial bones near the nose
Maxillary sinuses under the eyes in the
maxillary bones
• Frontal sinuses, superior to the eyes, in the
frontal bone
• Ethmoid sinuses in the ethmoid bone
• Sphenoid sinuses in the sphenoid bone at
the center of the skull base
The Pharynx
Funnel-shaped passageway • Connects nasal cavity and mouth • Divided into three sections by location – Nasopharynx – Oropharynx – Laryngopharynx • Type of mucosal lining changes along its length
The Nasopharynx
• Superior to the point where food enters
• Conducts air
• Ciliated pseudostratified columnar epithelium propels
mucus
• During swallowing the soft palate and its uvula reflect
superiorly and closes off nasopharynx
• Contains the opening to the pharyngotympanic tube
(auditory or eustachean tube)
• Tubal tonsil is posterior to pharyngotympanic tube and
provides some protection from infection
• Pharyngeal tonsil (adenoids)
– Located on posterior wall of nasopharynx
– Defends against pathogens entering in air and on foods
The Oropharynx
Arch-like entranceway—fauces
• Extends from soft palate to the epiglottis
• Stratified squamous epithelium
• Both food and air pass through oropharynx
• Two types of tonsils in the oropharynx
– Palatine tonsils—in the lateral walls of
the fauces
– Lingual tonsils—covers the posterior
surface of the tongue
The Laryngopharynx
• Passageway for both food and air
• Stratified squamous epithelium
• Continuous with the esophagus and
larynx
Larynx functions
• Voice production • Provides an open airway • Routes air and food into the proper channels • Epiglottis – closed during swallowing – open during breathing
Larynx
• Positioned at level C4-C6 • Superiorly attached to hyoid bone • Inferiorly attached to trachea • Superior part of larynx has stratified squamous epithelium • Inferior to vocal cord the epithelium is pseudostratified ciliated columnar with upward directed power stroke of cilia which helps clear dust trapping mucus
Nine Cartilages of the Larynx
• Epiglottis: Tips inferiorly to cover entry into
trachea during swallowing
• Thyroid cartilage: shield-shaped, forms
laryngeal prominence (Adam’s apple)
• Three pairs of small cartilages
– Cuneiform cartilages
– Corniculate cartilages
– Arytenoid cartilages
• Cricoid cartilage: the only laryngeal
cartilage that forms a complete ring
The Larynx 2
• Innervation of the larynx by recurrent laryngeal nerves (branch of vagus nerve/ CN X) • Ligaments of the larynx – Vocal folds (true vocal cords) • Act in voice production – Vestibular folds (false vocal cords) • No role in voice production
Larynx size
male versus female
The thyroid cartilage is larger in adult
men than adult women because male
sex hormones stimulate its growth
during puberty
• Adult males have longer vocal folds and
deeper voices than than adult females
Trachea
• Descends into the mediastinum
• C-shaped cartilage rings keep airway open
• Pseudostratified ciliated columnar epithelium
• Carina marks where trachea divides into two
primary bronchi
Supportive connective tissue in
walls trachea and lung tubes
Trachea: hyaline cartilage rings
• As main bronchi enter lungs: cartilage
rings are replaced with irregular plates
of cartilage
• Bronchi: plates of cartilage
• Bronchioles: elastin
Lung landmarks
• Apex: superior tip of lung
• Base: inferior surface of lung which sets on the
diaphram
• Hilum: indentation on medial surface of each lung
through which bronchi, blood vessels, lymph
vessels, and nerves enter and exit the lung
• Left lung: Superior & inferior lobes
• Fissure—oblique
• Right lung: Superior, middle, & inferior lobes
• Fissures—oblique and horizontal
Bronchi & Bronchioles in Conducting Zone
• Primary (main) bronchi: right and left with right main bronchi wider and shorter than the left main bronchi • Secondary (lobar) bronchi – Three on the right – Two on the left • Tertiary (segmental) bronchi – Branch into each lung segment • Bronchioles – Less than 1 mm in diameter • Terminal bronchioles – Less than 0.5 mm in diameter
Bronchopulmonary segments
Right lung • Right superior lobe: 3 segments • Right middle lobe: 2 segments • Right inferior lobe: 5 segments Left lung • Left superior lobe: 4 segments • Left inferior lobe: 5 segments
Epithelial Changes along Pathways in
Lungs
pseudostratified ciliated columnar which
produce mucus (trachea & bronchi)
• simple columnar with cilia which produce
mucus (large bronchioles)
• simple cuboidal (terminal and respiratory
bronchioles; Type II alveolar cells)
• simple squamous epithelium (Type I
alveolar cells)
Smooth muscle composition in
smaller bronchi and bronchioles
Smooth muscle influences diameter of smaller
bronchi and bronchioles
– Airways dilate with sympathetic stimulation
– Airways constrict with parasympathetic
stimulation
Air-exchanging structures of Respiratory Zone:
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs
- Alveoli
Structures of the Respiratory Zone
- Respiratory bronchiole
- Alveolar duct
- Alveolar sac
- Alveoli
- Alveolar pores
Alveoli number and surface area
• 300 million alveoli account for
tremendous surface area of the lungs
• Surface area of alveoli is 140 square
meters
Alveoli structure
The wall of each alveolus consists of a single layer
of simple squamous epithelial cells, called Type I
cells—which are surrounded by a delicate basal
lamina
• Alveolar macrophages move freely along the
inner surfaces of alveoli and engulf microbes
• Alveolar pores interconnect alveoli and equalize
air pressure throughout the lung
• Basal lamina of alveolar epithelium and blood
capillary endothelium are fused to form the
respiratory membrane through which O2 and CO2
are exchanged
Type II cells in alveoli
• Type II cells are scattered among type I
cells
• Type II are cuboidal epithelial cells
• Secrete surfactant which reduces
surface tension within alveoli to keep
them inflated
Blood Supply & Innervation of Lungs
Pulmonary arteries – Deliver oxygen-poor blood to the lungs • Pulmonary veins – Carry oxygenated blood to the heart • Innervation of lungs – Parasympathetic—constrict bronchial airways – Sympathetic—dilate bronchial airways – Visceral sensory
The Pleurae
A double-layered sac surrounding each lung – Parietal pleura – Visceral pleura • Pleural cavity – Potential space between the visceral and parietal pleurae • Pleurae help divide the thoracic cavity – Central mediastinum – Two lateral pleural compartments
Neural Control of Ventilation
• Most important respiratory center, called
the ventral respiratory group (VRG) is in
reticular formation in the medulla
oblongata
• VRG is a pacemaker which generates
respiratory rhythm and rate with input from
the pons respiratory centers and dorsal
respiratory group (DRG) in dorsal
medulla oblongata
Neural Control of Ventilation
Medulla respiratory center is influenced by input
from chemoreceptors that sense the chemistry of
blood
• Chemoreceptors
– Sensitive to rising and falling O2 and CO2 levels
– Central chemoreceptors—located in medulla
oblongata
– Peripheral chemoreceptors transmission of
sensory information
• Aortic bodies via vagus nerve
• Carotid bodies via glossopharyngeal nerve
and possibly also vagus nerve
Two phases of
pulmonary ventilation
- Inspiration—inhalation
* Expiration—exhalation
Inspiration
Volume of thoracic cavity increases
• Diaphragm flattens and moves inferiorly
• Contraction of external intercostal
muscles raises the ribs upward
• During quiet inspiration, the external and
internal intercostal muscles function
together to stiffen the thoracic wall
Quiet Expiration
- Quiet expiration—chiefly a passive process
- Inspiratory muscles relax
- Diaphragm moves superiorly
- Volume of thoracic cavity decreases
Muscles which contribute to
deep inspiration
- Scalenes
- Sternocleidomastoid
- Pectoralis minor
- Erector spinae
Forced Expiration is an active
process produced by contraction of
- Internal and external oblique muscles
- Transverse abdominis muscles
- Latissimus dorsi
- Internal intercostals
Disorders of
Lower Respiratory Structures
Bronchial asthma: constriction of bronchiole smooth muscle which results in difficulty inhaling air • Emphysema: breaking down of alveolar walls and loss of lung elasticity which results in air trapping
