Anatomy and Physiology of Nose Flashcards
Describe the functions of the nose (1)
Nasal airway
Principal physiological function: humidify and warm inspired air
Blocked nose – dry mouth disturbed sleep
Tracheostomy/laryngectomy patients need humidifiers
Remove noxious particles from the air, protects delicate distal lower respiratory tract
Olfaction (Smelling)
Sense organ, housing the olfactory apparatus
Smell substances for pleasure and defence purposes.
Important role in protection from danger, such as fire
Central in forming positive and negative memories
Taste: While chewing, chemicals from food activate olfactory receptors to identify food flavour.
Dysfunction can result poor quality of life
Describe Choanal atresia, its consequences and treatment
Failed recanalization of the nasal fossae during foetal development
Neonates are obligate nasal breathers
This is an emergency, as neonate will be unable to breathe
Requires surgical repair
Functions of the nose (2)
Immune
Mucus consists of compounds that are able to neutralize antigens
Immunoglobulin A (IgA) and immunoglobulin E (IgE)
Good example is nasal flu vaccine
Smoking reduces number of cilia and change in mucous viscosity.
Speech
Nasal airflow modifies speech and produce nasal clicks or click consonants.
Paranasal sinuses also contribute to vocal resonance.
People with blocked nose sound ‘bunged up’
Describe Nasal Aerodynamics
Nasal air flow is laminar as it enters the nasal vestibule - no mixing of the different air layers at low velocity.
Velocity of the air increases through the nasal valve, the narrowest site of the upper respiratory tract.
- At this point turbulent flow is observed in the nasal cavity, with different air layers swirling together.
- Change from laminar to turbulent flow allows the velocity to reduce, allowing prolonged contact with the nasal mucosa
Describe Functions of the paranasal sinuses
Paranasal sinuses - air filled, arise from the nasal cavity
Physiological role is debated, but suggested functions include:
- Reduce skull weight
- Physical buffer / crumple zone
- Vocal resonance
- Humidification
- Heat insulation
- Immune barrier
Describe the physical properties of the external nose
Visible component of face
Pyramidal shape, with base continuous with forehead and apex at the nasal tip.
Dorsum = surface between root of nose and tip.
Opening of nose – nares, separated by the columella
Describe the nasal skeleton (external nose bones)
Bony and cartilaginous components
Nasal bones - paired, symmetrical oblong bones.
Main cartilages – 2 paired lateral cartilages
Upper lateral cartilages
Lower lateral (alar) cartilages
Supported by septal cartilage
Smaller minor cartilages
Describe Nasal bone fracture
Most common facial fracture
Can result in permanent deformity
Possible to correct before bone heals
Most often performed under local anaesthesia
Beware septal haematoma!
Describe the consequences of saddle nose deformity
Clinical Relevance - Saddle nose deformity can occur as a result of nasal trauma
Cartilage has no blood supply of its own
Relies on surrounding perichondrium
Haematoma results in ischaemia and necrosis of the septum
Support to the nose lost
Describe vasculature of the external nose
Skin of external nose receives arterial supply from supratrochlear and dorsal nasal arteries (branches of the ophthalmic artery) and infraorbital artery (branch of maxillary artery).
Septum and alar cartilages receive supply from theangularartery andlateral nasalartery
Bothare branches of thefacial artery
Venous drainage into thefacial vein, then into the internal jugular vein.
Describe innervation of the external nose
Sensory innervation of external nose is derived from thetrigeminal nerve (CN V)
- Infratrochlear and external nasal nerves, branches of the ophthalmic nerve (CN V1), supply the skin of the dorsum of nose, nasal alae and nasal vestibule
- The lateral aspects of the nose are supplied by theinfraorbital nerve, a branch of the maxillary nerve (CN V2)
Motor innervation to the nasal muscles via thefacial nerve (CN VII).
Describe the nasal musculature.
Nasalis: paired muscle, covers the dorsum of the nose.
- Innervation: Buccal branch of facial nerve (CN VII)
- Action: Alar part: Depresses ala laterally, dilates nostrils, Transverse part: Wrinkles skin of dorsum of nose
Procerus: small pyramidal muscle occupying the glabella
- Innervation: temporal, lower zygomatic or buccal branches of facial nerve (CN VII)
- Action: depress the medial ends of the eyebrows, wrinkles skin over the glabella - creates a facial expression of frowning, or when exposed to bright light or other eye irritants.
Describe characteristics of the internal nose/nasal cavity
Superior part of respiratory tract
Midline nasal septum, separates left and right nasal passages
Divided into 3 parts:
- Vestibule – entrance to cavity, lined hair bearing skin
- Respiratory region - lined by a ciliated psudeostratifiedepithelium, with mucus-secreting goblet cells.
- Olfactory region - at the apex of the nasal cavity. It is lined by olfactory cells with olfactory receptors.
Describe the structure of the nasal septum
Vertical wall, divides left and right nasal passages.
Forms medial wall of nasal passage
Consist of bony and cartilaginous parts:
- Quadrangular cartilage
- Perpendicular plate of ethmoid
- Vomer
- Maxillary crest
- Palatine bone
What are Nasal turbinates?
Three paired bony projections from the lateral nasal wall
