Anatomy of the Respiratory Tract Flashcards
What are the functions of the respiratory system?
- Provide oxygen to all body tissues
- providing a large surface area for gas exchange
ventilation (providing air) - Remove carbon dioxide
- Regulate blood pH
- Defence against pathogens
- protecting respiratory surfaces from dehydration and temperature changes
- Produces sound
- Olfaction (sensation of smell)
How can the respiratory tract be organised?
- upper or lower
- conductive or respiratory
What makes up the upper respiratory tract?
- Nose
- Pharynx
- Paranasal sinuses
- Larynx
What are the functions of the upper respiratory tract?
- Warms and moistens and filters the air
- Olfaction (smell)
- Production and resonation of sound (produces in larynx, resonates as it gets moved up through the passageways)
- (protects lower tract)
What are the functional adaptations of the nose?
- vibrissae
- conchae
- mucosa
- rich capillary network under mucosa
- seromucous glands
- olfactory mucosa
- paranasal sinuses
What are the vibrissae?
hairs at entrance to nose which trap large dust particles
What are the Conchae?
Projections from lateral wall which produce turbulence
Allow more time to warm and moisten the air
Means airborne particles are more likely to come into contact with the mucous
Creates circular air-currents that bring olfactory stimuli to the olfactory receptors
What’s the mucosa and what does it do?
Pseudostratified ciliated columnar epithelium with goblet cells
Goblet cells produce mucous to trap particles
Cilia waft the trapped particles to pharynx where they can be swallowed
What does having a rich capillary network in the nose do?
the blood warms the air
What do the seromucous glands do?
secretions moisten the air
What are the Olfactory mucosa and what do they do?
Located in upper aspect of nose, above the superior conchae
Contains receptors for smell
What are the paranasal sinuses and what do they do??
Air filled spaces in bones around the nose
Lighten the skull and resonate sound
Secretions for the sinuses drain into nasal cavity
What is the pharynx?
A fibromuscular tube that forms a communal passageway for respiratory and gastrointestinal systems
What three regions is the pharynx divided into?
Nasopharynx – posterior (behind) to nose
Oropharynx – posterior to mouth
Laryngopharynx – posterior to larynx
What does the close proximity of gastrointestinal and respiratory systems lead to?
swallowing difficulties and aspiration of food and fluid
What are the main functions of the Larynx?
Maintains an open airway Prevents food and drink entering the lower respiratory tract Sound production Involved in coughing Involved in defaecation
What does the Larynx consist of?
A cartilaginous skeleton (thyroid cartilage is Adam’s apple) (hyoid bone)
A lining made of membranes – joins the cartilage inside
Vocal cords – made of edges of membranes. Important in sounds projection and protecting the airway
Muscles which move the vocal cords
Glottis
What is the glottis and what does it do?
When air comes in it passes down through the glottis
Slit like opening
Space between the vocal cords
Usually open to allow air flow
Closed during swallowing to prevent aspiration
Air vibrates over the vocal cords to produce sound
The wider the cords are open the louder the sound
What is the lower respiratory tract made up of?
- Trachea
- Primary bronchi
- Secondary bronchi
- Tertiary bronchi
- Bronchioles
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs
- Alveoli
What is the trachea?
- Tough, flexible tube, 4.5cm long, 2.5cm in diameter
- Extends from the larynx to the carina
- Lies anterior to the oesophagus (oesophagus is just behind)
- Contains 15-20 horseshoe shaped cartilages which keep airway open
- Posterior ends of cartilage are joined by trachealis muscle which constricts during coughing. Also is soft for when oesophagus expands
- Lined by pseudostratified ciliated columnar epithelium with goblet cells
What do pseudostratified ciliated columnar epithelium with goblet cells do?
- Acts as a mucociliary escalator
- Mucus layer which traps dust particle
- Cilia aft particles up to the larynx where they get swallowed and ingested
What is the bronchial tree made up of?
- Bronchi Primary Secondary Tertiary - Bronchioles Bronchioles Terminal Bronchioles Respiratory bronchioles
What are the histological changes displayed as you go down the bronchial tree?
Amount of cartilage decreases
Amount of smooth muscle increases
Height of epithelial cells decrease (columnar -> cuboidal -> flattened)
What are the primary bronchi and what do they do?
Supply each lung
2-3cm long
Right is wider and more vertical than left
Left is more horizontal – means that foreign bodies are less likely to get through
C-shaped cartilages (similar to trachea) – incomplete behind with muscle at the back
What are the secondary bronchi (lobar) and what do they do?
Supply lobes of the lung (3 on right, 2 on left)
Plates of cartilage (in small pieces) still cover all of the secondary bronchi though
What are the tertiary bronchi and what do they do?
Supply segments of the lung (10 on right, 8 on left)
Plates of cartilage (smaller than secondary bronchus). Between cartilage there is connective tissue and smooth muscle.
What do the bronchi provide?
A passageway for the air to move through
What are features of the bronchioles?
No cartilage
Simple columnar epithelium with cilia
Few goblet cells
Smooth muscle – allows bronchiole to constrict and dilate
Each gives rise to 50-80 terminal bronchioles
What are terminal bronchioles?
Simple columnar epithelium with cilia
No goblet cells or mucous glands
Clara cells – produce surfactant which reduces surface tension
Each gives rise to 2 or more respiratory bronchioles
What are respiratory bronchioles?
Simple cuboidal epithelia
No cilia
Clara cells – produce surfactant
Alveoli extend from the lumen: gas exchange occurs here
Why do goblet cells stop before the cilia in bronchioles?
because the cilia needs to waft all the mucous out
What is the alveoli?
The sit of gas exchange?
How are alveoli distributed?
- respiratory bronchioles lead to alveolar ducts
- alveolar ducts are elongated airways with walls made of alveoli
- alveolar ducts lead to alveoli sacs
- alveoli sacs are spaces surrounded by clusters of alveoli
What are the features of alveoli?
- 150-305 million alveoli per lung
- Surrounded by a network of capillaries
- Provides an extensive surface area for gas exchange
- Rich blood supply
How does the blood supply to the alveoli work?
- Entering: Pulmonary artery -> pulmonary arteriole -> capillary network around alveolus
- Leaving: capillary bed -> pulmonary venule -> pulmonary veins
What is the structure of an alveolus?
- Wall is made up of type 1 alveolar cell: simple squamous epithelium
- Type II alveolar cell: secretes surfactant (reduces surface tension and allows expansion of the lungs)
- Macrophage: phagocytoses small inhaled particles and bacteria
- Air has to pass through respiratory membrane from the alveolus into the capillary
- Respiratory membrane is very thin promoting diffusion of gases
What is the respiratory membrane made up of?
epithelium of type I cell
basement membrane of type I cell
Basement membrane of capillary
Endothelium of capillary
Why is the respiratory membrane so thin?
Because the two basement membranes are often fused together
What happens with the respiratory membrane if you are ill?
fluid can collect between the basement membranes making diffusion harder (pulmonary hypertension)
What is the conductive portion of the respiratory tract concerned with?
filtering, warming and moistening the air and conducting the air into the lungs
What does the conductive portion of the respiratory tract include?
all parts of the tract where gas exchange takes place
What does the conductive portion of the respiratory tract consist of?
Nasal cavity and paranasal sinuses Pharynx Larynx Trachea Primary bronchi Secondary bronchi bronchioles terminal bronchioles
What does the respiratory portion of the respiratory tract consist of?
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
What is a mucosa?
A mucous membrane
What does the respiratory mucosa consist of?
an epithelium and an underlying layer of areolar tissue. The lamina propria is the underlying layer of tissue. In the upper respiratory system the lamina propria contains goblet cells. In the lower system it contains smooth muscle cells
When does the rate of mucous production in the nasal cavity and paranasal sinuses speed up?
when exposed to unpleasant stimuli
Where contains nose hairs?
epithelium of the nasal vestibule
What divides the right and left sides of the nose?
the nasal septum
what supports the dorsum and apex of your nose?
the hyaline cartilaginous plate
How is the nasopharynx separated from the oral cavity?
It has a soft palate that separates it
Where does the oropharynx extend between?
the soft palate and the base of the tongue at the level of the hyroid bone
What are the three large unpaired cartilages that form the larynx?
the thyroid cartilage, the cricoid cartilage and the epiglottis
what do the the thyroid cartilage and the cricoid cartilage do?
protect the glottis and the entrance to the trachea
What does the epiglottis do?
forms a lid over the glottis. It folds back over the glottis during swallowing
Why are vocal cords highly elastic?
because the vocal ligaments consist of elastic tissue
What muscles is the larynx associated with?
muscles of the neck and pharynx which position and stabilize the larynx and smaller intrinsic muscles that control tension in the glottal vocal folds. When you swallow both sets of muscles work together to prevent food or drink from entering the glottis
What is laryngitis?
An infection or inflammation of the larynx
What does the normal diameter of the trachea change due to?
- the sympathetic division
- it increases the diameter of the trachea
What does the carina do?
separates the openings of the right and left main bronchi at their junction with the trachea
What happens in bronchitis?
bronchi and bronchioles become inflamed and constricted, increasing resistance
What does sympathetic and parasympathetic activation of the bronchi lead to?
Sympathetic activation leads to bronchodilation and parasympathetic activation leads to bronchoconstriction
What does tension in smooth muscles commonly cause?
causes the bronchiole mucosa to form a series of folds that limit airflow. This can be particularly severe in asthma
What takes place in the bronchi’s during an allergic reaction?
bronchoconstriction
What are the squamous epithelial cells in alveoli called?
pneumocytes
What does surfactant contain?
phospholipids and proteins