BIOL 2304
Respiratory System
The Respiratory System
Functions:
Respiration (gas exchange) – To supply the body with oxygen and dispose of carbon dioxide
1. Pulmonary ventilation – moving air into and out of the lungs
2. External respiration – gas exchange between the lungs and the blood
3. Transportation – transport of oxygen and carbon dioxide between the lungs and tissues
4. Internal respiration – gas exchange between systemic blood vessels and tissues
Conditioning of inhaled air – air that is inhaled through the nasal cavity and paranasal sinuses is
warmed, humidified, and cleaned of particulate matter
Functional Anatomy of the Respiratory System
Respiratory organs
Nose, nasal cavity, and paranasal sinuses
Pharynx, larynx, and trachea
Bronchi and bronchioles
Lungs and alveoli
Respiratory Anatomy
Respiratory System
Consists of:
Respiratory muscles –
Diaphragm contracts for inspiration, relaxes for
expiration
External intercostal muscles contract for inspiration
Internal intercostal muscles contract for forced
expiration
Smooth muscle surrounding bronchioles and pulmonary
capillaries
Conducting zones
Nose, nasal cavity, pharynx, trachea, bronchi, terminal
bronchioles
Provides rigid conduits for air to reach the sites of gas
exchange
Air passages undergo 23 orders of branching in the lungs
Respiratory zone – site of external respiration
Respiratory bronchioles, alveolar ducts, alveolar sacs,
alveoli
The Nose
Provides an airway for respiration
Moistens and warms air
Filters inhaled air
Resonating chamber for speech
Houses olfactory receptors
Skin is thin – contains many sebaceous glands
The Nasal Cavity
External nares – nostrils
Divided by nasal septum
Vestibule - anterior opening of nares
Continuous with nasopharynx
Two mucous membranes:
Olfactory mucosa - near roof of nasal cavity,
houses olfactory (smell) receptors
Respiratory mucosa - lines nasal cavity
Pseudostratified ciliated columnar
epithelium
Goblet cells within epithelium
Cilia move contaminated mucus
posteriorly to be swallowed
Nasal Cavity
Nasal Conchae
3 paired bony projections along the lateral walls of the nasal cavity
Superior and middle nasal conchae – part of the ethmoid bone
Inferior nasal conchae –individual bone
Function:
Deflect particulate matter onto mucus-coated surfaces
The Paranasal Sinuses
The Pharynx
Funnel-shaped passageway
Extends from base of skull to esophagus
Connects nasal cavity with oral cavity
Type of mucosal lining changes along its length
Divided into three sections:
Nasopharynx – between base of skull and soft palate
Oropharynx – posterior to oral cavity
Laryngopharynx – between the hyoid bone and the esophagus
The Nasopharynx
Superior portion of pharynx
Air passageway only (closed off during swallowing)
Epithelium consists of pseudostratified ciliated columnar epithelium that moves mucus
Pharyngeal tonsil (adenoids)
Located on posterior wall, destroys entering pathogens
Contains the opening to the auditory tube
Tubal tonsil - located posterior to the opening of the Eustachian tube; provides some protection from
infection
The Nasopharynx
The Oropharynx
Fauces - the arch-like entranceway from the oral cavity into the oropharynx
Oropharynx extends from soft palate to the epiglottis
Epithelium: stratified squamous epithelium
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
Epithelium: stratified squamous epithelium
Continuous with the esophagus and larynx
The Larynx
Passageway for air only
Prevents food and drink from entering the trachea
Produces vocal sounds
Connects the pharynx to the trachea
Epithelium of the larynx
Superior portion: Stratified squamous
Inferior portion: Pseudostratified ciliated columnar
Nine Cartilages of the Larynx
Three unpaired cartilages:
Thyroid cartilage - shield-shaped, forms laryngeal prominence (Adam’s apple)
Epiglottis - tips inferiorly during swallowing
Cricoid cartilage - a ring of hyaline cartilage that forms the inferior wall of the larynx
Three smaller, paired cartilages:
Arytenoid cartilages
Corniculate cartilages
Cuneiform cartilages
The Larynx
Vocal ligaments of the larynx
Vocal folds (true vocal cords) - act in sound production
Vestibular folds (false vocal cords) - no role in sound production
Voice production
Length of the vocal folds changes with pitch
Loudness depends on the force of air across the vocal folds
The Larynx
The Trachea
Descends into the mediastinum
C-shaped cartilage rings keep airway open
Carina - marks where trachea divides into two primary bronchi
Epithelium: pseudostratified ciliated columnar
Bronchi in the Conducting Zone
Bronchial tree - extensively branching respiratory passageways
Primary bronchi (main bronchi)
Largest bronchi
Right main bronchi - wider and shorter than the left
Secondary (lobar) bronchi
Three on the right
Two on the left
Tertiary (segmental) bronchi - branch into each lung segment
Bronchioles - little bronchi, less than 1 mm in diameter
Terminal bronchioles - less than 0.5 mm in diameter
Tissue Composition of Conducting Zone
Changes along pathway
Supportive connective tissues change
C-shaped rings – trachea, primary bronchi
Replaced by cartilage plates (secondary, tertiary, and smaller bronchi)
Epithelium changes
Trachea pseudostratified ciliated columnar
Bronchi: simple columnar epithelium
Bronchioles and terminal bronchioles: simple cuboidal epithelium
Smooth muscle in bronchioles becomes important
Airways widen with sympathetic stimulation
Airways constrict under parasympathetic direction
Lobes, Fissures, & Markings of the lungs
Left lung:
Two lobes – Superior and inferior lobes
Fissure – oblique
Right lung:
Three lobes: Superior, middle, and
inferior
Fissures – oblique and horizontal
Major landmarks:
Apex, base, hilum, and root
Bronchi and vasculature enter the lungs at the
hilum
Cardiac notch – concavity on medial surface
The Pleurae
A double-layered sac surrounding each lung
Parietal pleura – lines pleural cavity wall
Visceral pleura – covers lungs
Pleural cavity - potential space between the visceral and parietal pleurae
Pleurae help divide the thoracic cavity
Central mediastinum
Two lateral pleural compartments
Structures of the Respiratory Zone
Consists of air-exchanging structures
Respiratory bronchioles – branch from terminal bronchioles
Lead to alveolar ducts
Lead to alveolar sacs
Alveolar Sacs
Features Of Alveoli
Structure of Alveoli
Respiratory membrane - alveolar and capillary walls plus their basal lamina
Type I cells
Single layer of simple squamous epithelial cells
Surrounded by basal lamina
Type II cells – scattered among type I cells
Are cuboidal epithelial cells
Secrete surfactant – reduces surface tension within alveoli
Alveolar macrophages
Features Of Alveoli
Surrounded by elastic fibers
Interconnect by way of alveolar pores
Internal surfaces
A site for free movement of alveolar macrophages
Transverse section
Pulmonary Ventilation
During inspiration/inhalation
Diaphragm contracts and flattens
Intercostal muscle contract and raise ribs
Volume of thoracic cavity increases
During expiration/exhalation
Inspiratory muscles relax
Volume of thoracic cavity decreases
Muscles of Pulmonary Ventilation
Neural Anatomy of Breathing System
Most important respiratory center
Ventral Respiratory Group (VRG)
Located in reticular formation in the medulla oblongata
Neurons generate respiratory rhythm