Nasal+Cavity+and+Palate

=**Objectives**=


 * 1. Explain the external anatomy of the nose. What is responsible for the different shapes and sizes of noses.**

The external nose is considered pyramidal in shape and is composed of bone, cartilage and fibrofatty tissue. The shape and size of the bone, cartilages, and fibrofatty tissue determine the how ridiculous your nose looks.

The nares (singular naris) are the external openings of your nose where you can pick your nose. The dorsum of the nose has a bony component superiorly and a cartilaginous component inferiorly and makes up the bridge of your nose to the tip. The root is where the nose joins the forehead. The apex is the $20 word for the tip of your nose. The ala are the “winged” lateral portions composed of the cartilage and fibrofatty tissue. The nasal septum is a bony and cartilaginous plate that divides the nasal cavity in half.

Four bones make up the nose and include two nasal bones, the maxilla, and the frontal bone. There are five pairs of cartilages associated with the nose that I don’t give a shit about and neither should you.


 * 2. Discuss the parts of the nasal septum. Give the blood supply and innervation to this structure.**

The internal aspect of the nose is separated by the nasal septum and beings at the anterior openings of the nares and ends at the posterior openings of the choana. The nasal cavity opens into the nasopharynx.

__Vestibule__ The vestibule is the entrance into the nasal cavity just inside the nares and is the transition between skin and the nasal mucus membrane. It has course hair and is innervated by the infraorbital nerve, branch of CN V2.

__Mucus Membrane of Nasal Cavity__ The mucus membrane of the nasal cavity covers all of the nasal cavity and hard palate. It is considered a mucoperiostium and is fused with the periostium of the bone. It is highly vascular (nose bleeds bleed a lot) and has lots of mucus glands to humidify the air. The mucus glands are parasympathetically innervated to help dissolve smells for olfaction. The vasculature receives sympathetic innervation. Remember that the mucus membrane basically sandwiches the bone of the nasal septum on both sides.

__Nasal Septum__ The nasal septum is composed of bone and cartilage. The bony portion has an upper portion that is a perpendicular plate of the ethmoid bone. It is bordered superiorly by the cribriform plate where olfactory nerves penetrate to reach the olfactory bulbs. Above that is the crista galli of the ethmoid bone where the falx cerebri attaches in the anterior cranial fossa. The bony lower portion is the vomer bone. The nasal crest of the palatine and maxilla join with the vomer bone during the completion of the palate so that it also completes the nasal septum. Cleft palate also usually means incomplete closure of the nasal septum. The anterior portion of the nasal septum is formed by the nasal septal cartilage.

__Innervation of the Nasal Septum__ The superior 1/3 of the nasal cavity is olfactory epithelium, receiving innervation from CN I olfactory neurons. These specialized neurons have chemoreceptors on their apical surface and have cell processes that penetrate the cribriform plate and synapse on to the mitral cells which form the olfactory bulb and tract.

The anterior portion of the nasal septum is innervated by the anterior ethmoidal nerve, a branch of the ophthalmic nerve (CN V1). The posterior portion of the nasal septum is innervated by the nasopalatine nerve, branch of the maxillary nerve (CN V2). The nasopalatine nerve has the distinction of traveling across the inferior aspect of the nasal septum and passing to the palate through the incisive foramen.

__Blood Supply of the Nasal Septum__ The nasal septum is supply by a dense network of blood vessels. The anterior and posterior ethmoidal arteries supply the anterior and posterior aspect of the nasal septum, respectively. Both are branches of the ophthalmic artery (internal carotid). The inferior aspect of the nasal septum receives blood supply from the sphenopalatine artery, a branch of the maxillary artery (external carotid) coming from the infratemporal fossa.


 * 3. Explain the irregular contour of the lateral nasal wall. The inferior nasal conchae is a part of what bone? Give the blood supply and innervation to the lateral nasal wall.**

The lateral nasal wall contains conchae (turbinates) which increase the surface area of the nasal wall. The area inferior to each nasal concha is called a meatus. The inferior conchae are the largest concha, and overlie the ostium of the nasolacrimal duct. The middle conchae are smallerand overlie the openings of the openings of the antrior ethmoidal sinuses, frontal sinus openings within the Infundibulum, maxillary sinus opening within the Hiatus semilunaris, opening of middle ethmoidal sinuses within the Ethmoidal bulla and has the sphenopalatine foramen at its posterior end. The superior turbinates are smaller structures and overlie the openings of the posterior ethmoidal sinuses. The area superior to the superior nasal concha is called the sphenoethmoidal recess and contains the opening of the sphenoid sinus. The inferior concha is a named bone, while the middle and superior are parts of the ethmoid bone. The blood and comes from anterior and posterior ethmoidal arteries branches of the opthalmic and maxillary arteries respectivly. The nerve supply is from lateral nasal nerves which are branches of CNV, and smell from CNI.


 * 4. Explain the shape of the ethmoid bone. What is the function of the paranasal sinuses? Describe the route of mucus drainage from these sinuses.**

The ethmoid bone is located at the roof of the nose, between the two orbits. The bone consists of 4 parts: horizontal Cribriform plate the vertical Perpendicular plate which is part of the nasal septum, and the two lateral masses containing the sinuses (air cells). The sinuses serve as resinence chambers and lower the weight of the bone. These sinuses drain horizontally(medially) to the nasal cavity.


 * 5. Discuss several common clinical problems associated with the nasal cavity (i.e., nasal fractures, nosebleeds, chronic sinusitis).**

The nasal cavity has a significant blood supply, so bleeding in the area can be significant. The bones of the nasal cavity are very thin and easily fractured. The sinuses associated with the nasal cavity can become blocked off and infected increasing pressure in the sinus.


 * 6. What bones make up the hard palate? What muscles make up the soft palate? What is the function of the uvulae?**

The hard palate consists of the palating processes of the maxilla, and the horizontal process of the palantine bone. The soft palate consists of 4 pairs of muscles levator veli palatini, tensor veli palatini, palatoglossus, palatopharyngeus, and a musculus uvulae. The uvulae functions to complete the closure of the nasal cavity during swallowing.


 * 7. Describe the complete course of the greater palatine nerve, the nasopalatine nerve. What components are in these nerves?**

The greater palatine nerve descends through the greater palatine canal, emerges upon the hard palate through the greater palatine foramen, and passes forward in a groove in the hard palate. It supplies the gums, the mucous membrane and glands of the hard palate, and communicates in front with the terminal filaments of the nasopalatine nerve. The nasopalatine nerve enters the nasal cavity through the sphenopalatine foramen, passes across the roof of the nasal cavity below the orifice of the sphenoidal sinus to reach the septum, and then runs obliquely downward and forward between the periosteum and mucous membrane of the lower part of the septum. These nerves supply the mucouse membranes along their path.


 * 8. Give the source of blood supply to the hard and soft palate.**

The soft palate is supplied by the lesser palatine a. which descends through the palatine canal as the descending palatine a. a branch of the maxillary a. The hard palate is supplied by the Greater palatine a. which branches off the descending palatine a. and ascends up through the Incisive foramen to anastomose with the Nasopalatine a. in the nasal cavity.