Session 1 Flashcards
Outline the key functions of the respiratory system
- Gas exchange - Serves to ensure that all tissues receive the oxygen they need and can dispose of CO2 they produce
- Immune functions
- Inhalation & exhalation
- Vocalization
- Metabolic and endocrine functions
Define the term upper respiratory tract
• The part of the respiratory tract above the lower border of the cricoid cartilage (which forms the lower border of the larynx) is termed upper respiratory tract.
Define the term lower respiratory tract
• The parts of the respiratory tract below the lower border of the cricoid cartilage, including the lungs and associated structures.
What are the four main structures found in the URT?
- Nose
- Paranasal sinuses
- Pharynx
- Larynx
Describe the pulmonary circulatory system of the lungs
Low resistance system which is ‘supply driven’ rather than demand led
Low pressure
eceives entire cardiac output
What is the purpose of resistance vessels in the pulmonary circulation?
• Do not influence total flow through pulmonary circulation, only distribution of blood within it
Why is tissue fluid not normally formed in the lungs?
Capillary pressure in the normal pulmonary circulation is always less than the colloid osmotic pressure
Give three main functions of the URT
- Conducting air from atmosphere to the lower respiratory tract
- Conditioning (warming, humidification and trapping of particles) of inspired air
- Protection of the airway during swallowing (larynx)
Give three minor functions of the URT
• Swallowing (oropharynx and laryngopharynx)
• Smell (olfactory epithelium in nose)
Speech (larynx)
What two main parts make up the nose?
- The external nose (bone and cartilage)
* the nasal cavity
Describe the structure of the nasal cavity
- Divided into right and left cavities by the median nasal septum
- Each nasal cavity extends from the nostril (anterior nares) the posterior nare (or posterior chonae) behind.
Outline the structure of the lateral wall of each nasal cavity
Contains three bony projections known as the choncae (superior, middle and inferior)
• The space below each conchae is known as the meatus (superior, middle and inferior)
What structures drain into the meatus of the nasal cavity?
The paranasal sinus
The nasolacrimal duct
What does the floor of the nasal cavity form?
• The roof of the mouth
What are the three main functions of the nose?
• Respiration ○ Filters air ○ Humidifies and warms air • Organ of smell • Receives local secretion ○ Sinuses ○ Nasolacrimal duct
How does the structure of the nose relate to its function?
- Turbinates aid in warming and humidification by increasing SA and slowing airflow
• Lined by coarse hairs which aid in filtering of inhaled air
• Moist epithelium traps particles
• Watery nasal secretions evaporate and humidify air
Aside from humidification of air, what is the function of secreted nasal mucus and associated cilia?
Mucus secreted by goblet cells traps almost all particles. Cilia waft mucus to oropharynx where it is swallowed
Name the four paranasal sinuses
The frontal, ethmoidal, maxillary and sphenoidal sinuses
Give five possible functions of paranasal sinuses
- Extension of nasal cavity (humidification and warming of inspired air)
- Secrete mucus to moisten nasal chambers
- Lighten weight of skull
- Buffer for trauma (crumple zones)
- Insulating sensitive structures from temperature variation (eye, dental roots)
What are the three parts of pharynx?
- Nasopharynx
- Oropharynx
- Laryngopharynx
What is the key function of the pharynx?
• Prevent aspiration of food during swallowing, which can lead to life threatening airway obstruction or infection
How is the nasopharynx connected to the middle ear cavity?
• By the auditory tube (eustachian tube)
What does the connection of the nasopharynx to the middle ear cavity allow?
• Air pressure in middle ear cavity to be equalized to atmospheric pressure
What issue can the connection of the nasopharynx to the middle ear cavity cause?
• URTI can be spread to the middle ear cavity via the auditory tube, resulting in middle ear infection. More likely in children than adults.
Outline the gross structure of the larynx
- Cartaliginous skeleton made up of 3 unpaired cartilages - epiglottis, thyroid cartilage and cricoid cartilages - and 1 set of paired cartilages, called the arytenoid cartilages
- The vocal cords and the gap between vocal cords - together called the glottis
Give 2 main respiratory functions of the larynx
- Open during respiration, closed during swallowing - guards the entrance to the trachea
- Ability to close allows cough reflex to occur
How can diseases of the larynx present as respiratory disease?
- Laryngeal disease presents as airway obstruction & difficulty breathing
- Voice change can be first sign of serious intrathoracic disease, due to involvement of left recurrent laryngeal nerve
What is the path of the right and left pharyngeal nerve?
- Right - curves under subclavian artery
* On left - curves under aortic arch
Outline the movements of the vocal cords
- Adduction (closing) occurs during swallowing
- Abduction (opening) occurs during inspiration/deep inspiration
- Partially open during speech (phonation)
- Adducted during initial part of cough reflex
What are the vocal cords moved by?
• Intrinsic laryngeal muscles
What nerve are the intrinsic laryngeal muscles supplied by and why can this cause problems?
- The recurrent laryngeal nerve
- Intra thoracic disease compressing/infiltrating the nerve can result in a hoarse voice, due to paralysis of left vocal cord
Aside from closure of vocal cords, outline another mechanism by which aspiration is prevented
• Epiglottis folds downwards and covers laryngeal inlet
What lines the pleural sac of the lungs?
• A serous membrane
What lines the conducting portions of the respiratory tract?
• A mucous membrane
What structures make up the conducting portion of the respiratory system?
Nasal cavity Pharynx Larynx Trachea Primary bronchi Secondary bronchi Bronchioles Terminal bronchioles
What structures make up the respiratory portion of the respiratory system?
Respiratory bronchioles
Alveolar ducts
Alveoli
What happens to the walls of the passageways as you move down the respiratory tract?
They become thinner as lumens decrease in diameter
What epithelial cells are present in the conducting portion of the respiratory tract, except for the terminal bronchioles?
Pseudostratified epithelium with cilia and goblet cells
What cells are present in terminal bronchioles?
Simple columnar epithelium with cilia and Clara cells (release surfactant rather than mucus) - no goblet cells
What epithelial cells are found in the upper portion of the respiratory portion of the respiratory tract (not alveoli)
Simple cuboidal epithelium with Clara cells and sparsely scattered cillia
What cells are found in alveoli?
Simple squamous and cuboidal cells (secrete surfactant)
Which parts of the conducting system are extrapulmonary?
Nasal cavity Pharynx Larynx Trachea Primary bronchi
What is the function of venous plexuses in the non-olfactory regions of the nasal cavity?
Swell every at different point every 20-30 minutes and prevent over drying by varying airflow
How does the olfactory region of the nasal cavities differ from the non-olfactory?
No mucus secreting cells
Contain olfactory cells (bipolar neurons)
What are Clara cells?
• Dome shaped cells
• Produce lung surfactant
• Produce Clara cell protein
○ Measurable marker in bronchoalveolar lavage fluid (lowered then lung damage)
○ Measurable marker in serum (if raised, leakage across air-blood barrier)
What are the vocal cords lined with?
• Stratified squamous epithelium
Describe the histology of trachea and primary bronchi
- Contain cartilage rings and spiral muscle
- Lined with pseudo stratified cilliated columnar epithielium and various glands
Why are objects more like to lodge in right bronchus than left?
• More vertical than left
What is the function of the secretions from the epithelial and submucosal glands of the trachea and bronchi?
• Anti-bacterial function, contains lysozymes and anti-proteases
Describe the wall of the trachea
- Epithelial layer
- Lamina propria, rich in immune cells
- Sub mucosa
- Cartilage ring
What are the main components of the LRT (in order)
Trachea • Main bronchi (3 on right, 2 on left) • Lobar bronchi • Segmental bronchi • Sub-segmental bronchi • Bronchioles • Alveoli • Pulmonary and bronchial circulatory system
What is each terminal bronchiole connected to?
- Set of respiratory bronchioles
- Alveolar ducts
- Alveoli
How does a bronchiole differ from a bronchi?
- Bronchiole has less cartilage and no glands
- Bronchioles have more smooth muscle
- Bronchioles kept open by surrounding alveoli
- 1mm or less in diameter
Why is absence of cartilage in bronchioles an issue?
• Allows air passages to constrict and almost close down when smooth muscle contraction excessive
What is a terminal bronchiole?
- Smallest airways of the conducting portion
* Absence of goblet cells is important to stop individuals drowning in their own mucus
What is an alveolar duct?
An opening to alveolar sacs lined with alveoli
What is an alveolus?
• Plural of alveoli
What can an alveoli open into?
A respiratory bronchiole
An alveolar duct
An alveolar sac
Another alveolus
Describe the structure of alveolar walls
- have abundant capillaries
- are supported by a basketwork of elastic and reticular fibres.
- have a covering composed chiefly of type I pneumocytes.
- have a scattering of intervening type II pneumocytes.
How close are alveoli to capillaries?
• 0.2 micrometres
What cell types make up alveoli?
- 90% simple squamous
- 10% cuboidal
- Macrophages
