Human Nose is divided into 3 parts, the External nose, the Vestibule and the Nasal cavity. Today I am going to discuss about the basic science of Nose, Nasal Sinus, Paranasal Sinuses etc. The basic Anatomy of Nose is described in details. Physiology of Nose, Nasal and Paranasal Sinus consists of Blood supply, nerve supply etc. Blood supply is quite important. It will be needed in upcoming post. So I have decided to discuss it first.
External Nose: It is triangular or Pyramidal in shape. It has two nostrils in front known as anterior nares. It is separated by Columella. Its root is attached with the forehead. External Nose composed of bony part and cartilagenous part. Bony part consists of Nasal process of the frontal bones, Nasal bones and Ascending process of the maxillae. Cartilagenous part consists of Upper nasal cartilages, Lower nasal cartilages and Quidrilateral cartilage. It is supplied by the Facial Nerve.
The Nasal Vestibule: It is the entrance of Nasal Cavity which is lined by Stratified Squamous Epithelium.
The Nasal cavity: The right and left nasal fossae or cavity are separated by the nasal septum. Each fossa communicates with The para nasal sinuses through ostia and The nasopharynx through the posterior choanae
- Medial wall.
- Lateral wall
Lateral Wall: It is the most important part of Anatomy of nose and Nasal Sinus. The bony lateral wall is convoluted by the Turbinates called Superior, Middle and Inferior turbinate. Each turbinate over hangs a space called meatus. So lateral wall has got three meatus named by Superior, Middle and Inferior meatus. These meatus are important in clinical terms as all nasal sinus and paranasal sinus are open here.
- Superior Meatus: Posterior ethmoidal air sinus
- Middle Meatus: Maxillary sinus, Anterior and Middle ethmoidal sinus, Frontal sinus.
- Inferior Sinus: Nasolacrimal Duct.
The Sphenoid sinus drains into the Sphenoethmoid recess above the superior turbinate.Frontal sinus drains through the Frontonasal duct. There is also Agar Nasi, Uncinate process. For the Functional Endoscopic Sinus Surgery (FESS) this anatomy is very important.
This is the Nasal Septum. The formation of Nasal Septum is very important both for practise and examination in written and viva. It is formed mainly by
- Quadrilateral cartilage
- Perpendicular plate of Ethmoid bone
Minor Contribution from
- Nasal crest of Maxilla
- Nasal crest of Palatine bone
- Rostrum of Sphenoid bone
Roof: Roof is formed by
- Nasal bone
- Frontal bone
- Cribriform plate of ethmoid
- Body of Sphenoid bone
Floor: It is also known as Hard palate. It is formed by
- Palatine process of maxilla
- Horizontal process of palatine bone.
- Stratified Squamous Epithelium in Vestibule
- Ciliated Columner Epithelium in Nasal Cavity
- Olfactory Neuro epithelium in roof.
Blood Supply of Nasal Sinus:
Blood Supply has got the most clinical importance. Bleeding from nose is called Epistaxis. It is a common problem and 70% of adult males have had experience epistaxis (nose bleeding) over the age of 60 years, it is also common in children. Trauma , fracture, foreign body, nose picking are some of the most important cause of epistaxis.
The Nasal Septum is supplied by the following arteries:
- Anterior Ethmoid
- Posterior Ethmoid
- Greater palatine
- Superior labial branch of facial artery.
The first two are the branch of internal Carotid artery and the last three are External carotid artery. These arteries form a plexus at the anteroinferior part of nasal septum. This is called Little’s area of epistaxis or Kiesselbach’s Plexus.
The branch of Sphenopalatine artery forms a plexus at the posterior part of the nasal septum called Woodruff’s Plexus.
Para nasal air sinus:
These are air filled cavities, arranged in pairs. Paranasal air are sinuses grouped as—
- Maxillary sinuses.
- Frontal sinuses.
- Ant. group of ethmoidal sinuses.
- Posterior group of ethmoidal sinuses.
- Sphenoidal sinuses.
The Maxillary sinus is rudimentary at birth and gradually expands. The frontal sinus varies in size, divided by septum. The Ethmoidal air sinuses are 8-15 in number. They are large at birth.
Frontal: Paired sinuses, lying anteriorly in frontal bone and draining into semilunar hiatus of middle meatus
Ethmoid: Paired anterior and middle draining into middle meatus (hiatus semilunaris and ethmoid bulla, respectively) and posterior draining into superior nasal meatus
Sphenoidal: Paired sinuses, in sphenoid bone, draining into sphenoethmoidal recess
Maxillary: Paired sinuses, in maxilla, draining into middle meatus (semilunar hiatus); largest sinus (20–30 ml)
NERVES OF COMMON SENSATION
- Maxillary division of the trigeminal.
- Opthalmic nerve through its lateral and medial internal nasal branches.
NERVES OF SPECIAL SENSATION
- Olfactory Nerve.
AUTONOMIC NERVE SUPPLY
- Sympathetic- Causes vasoconstriction and diminishes secretion.
- Parasympathetic-Produces vasodilatation and increase secretion.
Function of nose:
- Provides airway for respiration.
- Air conditions the inspired air.
- Kills inspired bacteria and viruses by IgA
- Collects moisture.
- Gives resonance of voice.
- Filters suspended particulate.
- Organ of smell and lastly.
- Part of external beauty.
Function of Paranasal Sinus:
Functions of the sinuses are uncertain. But there are some theories.
- Result of facial development.
- Air conditioning.
- Lightening of skull.
- Resonance of voice.
- Humidification of inspired air.
- Protection of eye from trauma.
After finishing this article you can view these for more information. I Have not copied anything rather some thing may be contradictory. The source of my information is our ENT book by Dr. Matin Sir, FRCS.
Human nose– Wiki
Chapter 52: The nose and paranasal sinuses-Dartmouth.edu
Nasal Anatomy– http://emedicine.medscape.com