The nose Prepared by: Kriti banstola B.Sc. Nursing 4 th year

Structures of nose: 1.External nose : The visible portion of nose is situated just above the mouth. It is made up by two nasal bones and hyaline cartilages. The tip or apex of the nose is the lower free end. The root of the nose is the upper narrow part of the nose that is continuous with forehead.

The inferior surface of the nose is pierced by two apertures called anterior nares, which are separated from each other by the nasal septum. Each nares is bounded laterally by the ala or side of the nose. The dorsum is a round border between tip and root where side of the nose meet.

The external part of the nose consists of bony & cartilaginous framework formed above by the: 2 nasal bones Frontal processes of maxillae Nasal part of frontal bone It is formed below by plates of hyaline cartilage, which include upper & lower nasal cartilages and the septal cartilage.

2. Nasal cavity The hollow cavity or part inside the nose is known as nasal cavity. It is large irregular cavity divided into two equal parts by septum i.e. right and left cavity. The septum is formed anteriorly by hyaline cartilages and posteriorly by perpendicular plate of the ethmoid bone and the vomer. The nasal cavity is lined with ciliated columnar epithelial tissue, which contains mucous secreting goblet cells. These are highly supplied with the blood.

The nasal septum has a small area, which is common site of bleeding i.e. epistaxis. This small area is known as little’s area or kiesselbach’s area. It is highly blood supplied by:  Anterior ethmoidal artery  Posterior ethmoidal artery  Superior labial artery  Greater palatine artery  Sphenopalatine artery

The nasal cavity is made up of: I. The roof, It is narrow & formed (from behind forward) by the:  Body of sphenoid  Cribriform plate of ethmoid bone  Nasal spine of Frontal bone  Nasal bone & cartilage

II. The floor is formed by the roof of the mouth which consists of the hard palate in front and soft palate behind. The hard palate is composed of the maxilla and palatine bones and the soft palate consists of involuntary muscle. It separates nasal cavity from the oral cavity.

III. The medial wall (nasal septum). It is an osseocartilaginous partition, only rarely lying in the midline. It is covered by the mucoperiosteum. It is formed: Superiorly by the vertical (perpendicular) plate of ethmoid bone Posteriorly by the vomer bone Anteriorly by the septal cartilage

IV. The lateral wall is formed by the maxilla, the ethmoid bone and the inferior conchae. Bony part is formed by- Frontal process of maxilla Lacrimal bone Labyrinth of ethmoid with superior and middle concha Perpendicular plate of palatine bone Medial pterygoid plate (process of sphenoid bone)

Cartilaginous part is formed by-  Upper nasal cartilage  Lower nasal cartilage  4 small cartilage of ala

In the lateral walls we can observe three horizontal bony projections, covered by mucous membrane, the superior, middle and inferior conchae (turbinate). The superior and middle conchae are parts of the ethmoid bone, whereas the inferior concha is a separate bone The cavity below each concha is called a meatus and are named as superior, middle & inferior corresponding to the conchae.

The small space above the superior conchae is called as sphenoethmoidal recess. The conchae helps to increase the surface area. The recess and meatus receives the opening of, paranasal sinuses and nasolacrimal duct.

V. The posterior wall is formed by the posterior wall of the nasopharynx.

Openings in the nasal cavity: StructuresOpening Anterior naresFrom external nose into nasal cavity Posterior naresFrom nasal cavity into the pharynx Maxillary sinusesMiddle meatus Frontal sinusesMiddle meatus Sphenoid sinusesSphenoethmoidal recess Anterior ethmoidal sinusesMiddle meatus Posterior ethmoidal sinusesSuperior meatus

 Arterial blood supply: a)There is a rich blood supply to the mucus of nasal cavity. The pure blood is supplied by: b)Sphenopalatine artery, branch of maxillary artery. c)Greater palatine artery, branch of maxillary artery. d)Ethmoidal artery, branch of ophthalmic artery. e)Three branches of facial artery.

 Venous Drainage: Veins begin as a rich plexus in the submucosa of the nose and drain into the facial, ophthalmic, and sphenopalatine veins.  Lymphatic Drainage: Vestibule drain into the submandibular lymph nodes Rest of the cavity drains into the upper deep cervical lymph nodes

Physiology of smell. The human sense of smell is less acute than in other animals. Many animals secrets odorous channels called pheromones that play an important part in chemical communication, for example, territorial behavior, mating and bonding of the mothers and their newborn offspring.

The sense of smell is carried through the olfactory nerves to the brain. Their origin is in special cells in nasal epithelium of the superior portion of the nose which contain between 10 and 1000 million receptors for the sense of smell. It extends along the superior conchae and upper part of the middle nasal conchae.

The air entering the nose is warmed, and convection currents carry eddies of inspired air to the roof of the nasal cavity. ‘Sniffing’ concentrates volatile molecules in the roof of the nose. This increases the number of olfactory receptors stimulated and thus the perception of the smell. Olfactory receptors are the bipolar neurons. From the dendrites of these neurons several cilia (olfactory hairs) projects into the thin mucous film on the epithelium surface. The cilia are the sites of olfactory interaction.

The molecules are dissolved first in fluid in order to reach the olfactory receptor. When they reach the olfactory receptor they cause the olfactory receptors to depolarize, very few molecules are required to initiate an action potential axons from the olfactory neurons form the olfactory nerves. There are olfactory nerves which passes through the cribriform plate of the ethmoid bone to join the olfactory bulb. Then forming an tract they pass backward to the lateral olfactory area (primary olfactory area) in the temporal lobe of the cerebral cortex in each hemisphere.

Not only nose can detect the intensity of the smell, the direction from which the odor come often be detected by the difference in arrival time between the two nostrils. The sense of smell affect the appetite. If the odors are pleasant the appetite may improve and vice versa. When accompanied by the sight of the food, an appetizing smell increases salivation and stimulates the digestive system. The sense of smell may create long lasting memories, especially for distinctive odors, e.g. hospital smells, favorite or least liked foods.

 Ten different primary classes of olfactory stimulants have been identified: 1)Fragrant (e.g. florals and perfumes) 2)Fruity (all non-citrus fruits) 3)Citrus (e.g. lemon, orange) 4)Woody and resinous (e.g. pine or fresh cut grass) 5)Chemical ( e.g. ammonia, bleach) 6)Sweet (e.g. chocolate, vanilla, caramel) 7)Minty and peppermint (e.g. camphor) 8)Toasted and nutty (e.g. popcorn, peanut butter, almonds) 9)Pungent (e.g. cigar, smoke ) 10)Decayed (e.g. rotting meat, sour milk )

 Adaptation. When an individual is continuously exposed to an odor, perception of the odor decreases and ceases within a few minutes this loss of perception affects only that specific odor and adaptation probably occurs in both neurons within the central nervous system and the sensory receptors in the nasal cavity.  Olfactory dysfunctions: Hyposmia: impaired sense of smell. Anosmia: complete loss of sense of smell Olfactory hallucination: smelling odors that are not really present

Assignment: State the function of the nose. Date of submission: 2075/12/10