Respiratory: Anatomy of the Upper Respiratory Tract L11 Flashcards
Fundamentally, why do we have a respiratory system?
To humidify, warm and clean air, and get it close to the blood so that gas exchange can occur. While gas exchange (supply oxygen, disposing carbon dioxide) is the main function, the respiratory system is involved in other functions including: pH regulation, thermoregulation, our sense of smell and sound production (for communication).
What are the main structures of the upper respiratory tract?
Nose, mouth, nasal cavity, paranasal sinuses and 3 divisions of the pharynx and larynx.
Describe the structures that are a part of the nose, and where does it stop being ‘the nose’?
The external structure of the nose is the part that sticks out, it is comprised partly of bone but mainly of cartilage. It includes the nostrils, root of the nose, bridge of the nose, and apex of the nose.
Internal structures include the anterior nares (nostrils), and the vestibule, which is lined with hairs to catch particles. The vestibule is lined with skin containing sebaceous glands,
The internal nasal cavity begins after the vestibule. This is lined with mucous membranes.
What is the name of the structure that separates the two nasal cavities, what is its structure and function?
The nasal septum separates the nasal cavity into left and right cavities. It is formed of hyaline cartilage anteriorly, and bone posteriorly. This allows for protection and provides shape, but should not block off the airway if broken.
Describe components of the nasal cavity.
The floor of the nasal cavities consists of hard bone anteriorly (forming hard palate) and soft tissue posteriorly (forming the soft palate).
Lateral walls have conchae (turbinates), which are bony projections that provide turbulence as air goes through the nose. These fling air along with inhaled particles onto mucus, cleaning the air. The channels underneath the conchae are called meati.
The roofs of the nasal cavities are lined with olfactory mucosa, nerve endings found in this mucosa enable us to smell and to sneeze. The roof is formed by the sphenoid and ethmoid bones. The nasal cavity is designed to conduct air only, and therefore the rest of it is lined with respiratory mucosa.
Describe structure and function of paranasal sinuses.
There are four pairs of sinuses (each sinus is found on both sides of the skull) named after the bones in which they are located: the frontal sinuses, ethmoidal cells, maxillary sinuses, and sphenoidal sinuses.
They are lined with respiratory mucosa and open into the nasal cavities. Secretions are drained down the throat. The sinuses lighten the weight of the skull and provide resonance for the voice, as well as increasing the amount of available surface area for cleaning, warming and humidifying air.
What are the 3 layers of pharynx and where are they located?
The pharynx extends from behind the nasal and oral cavities to the larynx and oesophagus and has 3 divisions. Nasopharynx, oropharynx, laryngopharynx.
Describe location, structure and function of nasopharynx.
The posterior wall contains the pharyngeal tonsils (or adenoids), superior to the soft palate. These lymphatic tissues are embedded in mucosa. They provide defence against infection from inhaled particles, but can become swollen and block the nasopharynx.
Carries air only, therefore is lined with respiratory mucosa. The auditory tube connects and drain into the nasopharynx.
Connects the nasal cavity with the rear of the mouth: runs from posterior nares to the uvula.
Describe location, structure and function of oropharynx.
Found posterior to the oral cavity. Runs from the soft palate to the level of the hyoid bone and epiglottis (leaf-shaped cartilage of the larynx that prevents food from getting into lungs).
Carries both food and air and therefore needs a tougher epithelial lining: stratified squamous epithelium (food would damage the pseudostratified ciliated columnar epithelium of respiratory mucosa).
The palatine tonsils in the lateral wall and lingual tonsil on the base of tongue help to defend against infection from ingested material. These are sometimes surgically removed (esp. in children) in a ‘tonsillectomy’.
Describe location, structure and function of laryngopharynx.
Runs from the epiglottis to the level of the larynx (where the respiratory and digestive tracts diverge). The hyoid bone provides attachment for the epiglottis. This bone may be broken in cases of strangulation.
Where the laryngopharynx carries both food and air, it needs a tougher epithelial lining so it has stratified squamous epithelium (from the epiglottis bone to the larynx). During swallowing the laryngopharynx is blocked off.
Where only air passes is the respiratory mucosa.
Describe location, structure and function of larynx (voicebox).
A hollow structure with nine cartilages, one of which (the epiglottis) is fibro-elastic cartilage because it moves a lot and the remaining eight are of hyaline cartilage.
The larynx conducts air and protects the airway: there is an extremely sensitive reflex that makes you cough as soon as the slightest bit of food gets down the airway.
Below the level of the oesophagus, cilia in the larynx trap inhaled debris and propel it back up into the pharynx where it then gets swallowed and destroyed in the stomach.
Vocal cords in the larynx are involved in the production of sounds and speech. There are both ‘false’ and ‘true’ vocal cords. The ‘false’ cords are folded layers of mucosa, the ‘true’ cords are dense fibrous connective tissue.
Give the order of flow through the upper respiratory structures.
Nose: Anterior nares, vestibule, nasal cavity, posterior nares.
Pharynx: Nasopharynx, oropharynx, laryngopharynx, larynx.
In the respiratory mucosa, there is the PCCE cell. What might PCCE stand for and describe the components.
Pseudostratified ciliated columnar epithelium.
Pseudostratified = appears to be several layers of cells (i.e to be stratified) but this arrangement has all cells actually attached to the basement membrane, hence pseudo (not real).
Ciliated = cilia, little hair-like projections
Columnar = has column shape - cells are taller than they are wide.
Epithelium = tissue that lines the cavities and surfaces of body structures.
What are goblet cells?
Cells that are interspersed among the PCCE and produce and secrete mucus.
What are the lamina propria?
Below the epithelial layer is a supportive layer of connective tissue called lamina propria. Numerous blood vessels are found in the lamina propria and allow the avascular epithelial cells to function.
Serous glands and mucous glands are also found in the lamina propria. These secrete serous fluid and mucus that (along with the secretions of the goblet cells) help to trap small particles and also to humidify the air that passes over the mucosa.
