Nose Anatomy (External & Internal)

Functions of the Nose

The nose assists with numerous body functions, ranging from the vital process of respiration to the augmentation of taste.

Respiration

• Inhaled air enters the nose through the nostrils and exits during exhalation.
• From the nose, the inhaled air travels to the nasopharynx Nasopharynx The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function. Pharynx: Anatomy → oropharynx Oropharynx The middle portion of the pharynx that lies posterior to the mouth, inferior to the soft palate, and superior to the base of the tongue and epiglottis. It has a digestive function as food passes from the mouth into the oropharynx before entering esophagus. Pharynx: Anatomy → larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx: Anatomy → lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy

Olfaction Olfaction The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy

• Inhaled air comes in contact with the olfactory epithelium Olfactory epithelium Olfaction: Anatomy, located on the roof of the nasal cavity.
• Within the epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology, olfactory receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors bind BIND Hyperbilirubinemia of the Newborn odor molecules.
• The receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors are connected to the olfactory nerve, which transmits these signals to the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification.

Purification and moisturizing of inhaled air

• The walls of the nasal cavity are covered with hair, or cilia.
• The cilia trap dust and harmful particles to purify the inhaled air.
• The trapped dust particles are either:
  • Moved to the throat Throat The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy, where they are swallowed  
  • Excreted through the nasal cavity ( sneezing Sneezing The sudden, forceful, involuntary expulsion of air from the nose and mouth caused by irritation to the mucous membranes of the upper respiratory tract. Rhinovirus)
• Nose hair moisturizes and warms the air to the approximate temperature and moisture within the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.
• During exhalation, the heat Heat Inflammation and moisture in the CO₂ are absorbed by the nasal hair and then released into the atmosphere.

Sense of taste

• While chewing, chemicals from food activate olfactory receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors inside the nose.
• These receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors work in coordination Coordination Cerebellar Disorders with the taste buds Taste buds Small sensory organs which contain gustatory receptor cells, basal cells, and supporting cells. Taste buds in humans are found in the epithelia of the tongue, palate, and pharynx. They are innervated by the chorda tympani nerve (a branch of the facial nerve) and the glossopharyngeal nerve. Lips and Tongue: Anatomy to identify food flavor.

Speech

• Nasal airflow can modify speech and produce nasal clicks Clicks A high-pitched sound occurring at the point of maximal opening of the valves Heart Sounds or click consonants.
• Paranasal sinuses Paranasal Sinuses The 4 pair of paranasal sinuses include the maxillary, ethmoid, sphenoid, and frontal sinuses. The sinuses are a group of air-filled cavities located within the facial and cranial skeleton; all are connected to the main nasal cavity and nasopharynx. Paranasal Sinuses: Anatomy also contribute to vocal resonance.

The External Nose (+ Diagram)

Structure ( skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, bony components, nasal cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology)

The external nose is pyramidal in shape. The nose consists of:

• A proximal nasal root  
• The apex at the tip of the nose
• 2 inferior nares Nares Staphylococcal Scalded Skin Syndrome (SSSS)/nostrils (openings to the nasal cavity)
• Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions:
  • The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions over the bony part of the nose is thin.
  • The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions over the cartilaginous part is thicker and has many sebaceous glands.
  • The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions extends into the vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy of the nose via the nares Nares Staphylococcal Scalded Skin Syndrome (SSSS).
  • Vestibular skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions has hairs that function to filter air.
• Bony component is located superiorly and consists of:
  • Superiorly: inferior border of the nasal bones
  • Laterally: frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy processes of the maxilla Maxilla One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the orbit, and contains the maxillary sinus. Skull: Anatomy
  • Inferiorly: alveolar processes of the maxilla Maxilla One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the orbit, and contains the maxillary sinus. Skull: Anatomy 
• Cartilaginous component: located inferiorly and consists of
  • 2 lateral cartilages 
  • 2 alar cartilages 
  • 1 septal cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology

Muscles

The external nose contains muscles that aid with facial expression and in maintaining patency of the nostrils.

• Procerus Procerus Facial Muscles: Anatomy muscle:
  • Originates in the fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis overlying the nasal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types 
  • Inserts into the inferior forehead Forehead The part of the face above the eyes. Melasma
  • Contraction depresses the medial eyebrows and wrinkles the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions of the superior dorsum.
• Nasalis Nasalis Facial Muscles: Anatomy muscle:
  • Sphincter-like muscle
  • Transverse portion: assists the procerus Procerus Facial Muscles: Anatomy muscle
  • Alar portion:
    • Arises from the maxilla Maxilla One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the orbit, and contains the maxillary sinus. Skull: Anatomy
    • Inserts into the major alar cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology
    • Contraction dilates the nares Nares Staphylococcal Scalded Skin Syndrome (SSSS), flaring them.

The Nasal Cavity

• Most superior component of the respiratory tract
• Has 3 divisions:
  1. Vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy:
     • Skin-lined cavity directly behind the nostrils
     • Divided into left and right cavities by the septum
  2. Respiratory region: lined by ciliated pseudostratified epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology with mucus-secreting goblet cells Goblet cells A glandular epithelial cell or a unicellular gland. Goblet cells secrete mucus. They are scattered in the epithelial linings of many organs, especially the small intestine and the respiratory tract. Glandular Epithelium: Histology
  3. Olfactory region:
     • Located at the apex of the nasal cavity 
     • Lined by olfactory cells with olfactory receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors
• Each nasal cavity extends from the mucous ridge (limen nasi) anteriorly to the choanae posteriorly, ultimately extending to the nasopharynx Nasopharynx The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function. Pharynx: Anatomy.
• Walls of each nasal cavity (lined with respiratory epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology):
  • Roof: cribriform plate of the ethmoid, nasal bones, and body of the sphenoid
  • Floor: horizontal plate of the palatines and palatine process of the maxillas
  • Lateral walls:
    • Anterior: nasal bones, lacrimal bones, and frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy process of the maxilla Maxilla One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the orbit, and contains the maxillary sinus. Skull: Anatomy
    • Middle: superior, inferior, and middle conchae with corresponding meatus
    • Posterior: perpendicular plate of the palatine and the sphenoid
  • Medial wall or septum:
    • Septal cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology
    • Vomer Vomer An unpaired thin ploughshare-shaped facial bone. It is situated in the median plane of the skull. The vomer forms the posterior and inferior border of the nasal septum. Skull: Anatomy
    • Perpendicular plate of the ethmoid
    • Maxillary crest ( maxilla Maxilla One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the orbit, and contains the maxillary sinus. Skull: Anatomy and palatine bones)

The Nasal Conchae

The nasal conchae are 3 bony shelves arising from the lateral wall of the nasal cavity, curling inferomedially. They are also called turbinates, as they function similarly to a turbine, regulating air flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure.

Functions of the nasal conchae

The conchae slow the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of air so it can be cleaned, warmed, and humidified in the nasal cavity. They maximize the surface area of nasal mucosa:

• Superior concha: smallest, protect the olfactory bulb Olfactory bulb Ovoid body resting on the cribriform plate of the ethmoid bone where the olfactory nerve terminates. The olfactory bulb contains several types of nerve cells including the mitral cells, on whose dendrites the olfactory nerve synapses, forming the olfactory glomeruli. The accessory olfactory bulb, which receives the projection from the vomeronasal organ via the vomeronasal nerve, is also included here. Olfaction: Anatomy (structure housing smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors)
• Middle concha: protects the openings of the maxillary and ethmoid sinuses from pressurized nasal airflow
• Inferior concha: largest, responsible for the majority of airflow modification

Nasal meatuses

The conchae divide the nasal airway Airway ABCDE Assessment into 4 groove-like air passages called meatuses.

1. Superior meatus:
   • Between the middle and superior conchae
   • The posterior ethmoidal sinuses drain into it.
   • The sphenopalatine foramen opens into it.
2. Middle meatus:
   • Between the inferior and middle conchae
   • Frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy, maxillary, and anterior and middle ethmoidal sinuses drain into it. 
3. Inferior meatus:
   • Between the inferior concha and the floor of the nasal cavity
   • The auditory (Eustachian) tube opens into it.
   • The nasolacrimal gland drains into it.
4. Sphenoethmoidal recess:
   • Located posterior and superior to the superior concha
   • The sphenoid sinus Sphenoid sinus One of the paired air spaces located in the body of the sphenoid bone behind the ethmoid bone in the middle of the skull. Sphenoid sinus communicates with the posterosuperior part of nasal cavity on the same side. Paranasal Sinuses: Anatomy drains into it.

Neurovasculature of the Nose

Arterial supply (blood vessels of the nose)

• Internal carotid:
  • Anterior and posterior ethmoidal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology supply the septum.
  • Lateral nasal branch of the facial artery supplies the nasal ridge/alae.
• External carotid branches:
  • Supply the lateral walls, dorsum, and septum
  • Sphenopalatine artery 
  • Greater palatine artery Greater palatine artery Palate: Anatomy
  • Lateral nasal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • Superior labial artery
  • Angular artery (terminal branch of facial artery)
• Common carotid artery Common carotid artery The two principal arteries supplying the structures of the head and neck. They ascend in the neck, one on each side, and at the level of the upper border of the thyroid cartilage, each divides into two branches, the external and internal carotid arteries. Carotid Arterial System: Anatomy system: Kiesselbach’s plexus at the anterior lower part of the septum (most common source of bleeding in epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis)

Venous drainage

The veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology tend to follow the arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology. The veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology drain into:

• Pterygoid plexus
• Facial vein
• Cavernous sinus

Innervation (nerves in the nose)

• Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation to the superior wall and anterior aspect of the inner nose: ophthalmic nerve 
• Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation to the septum and lateral walls: branches of the maxillary nerve
• Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment of smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy: olfactory nerve

Clinical Relevance

Congenital conditions

• Choanal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS): congenital condition characterized by obstruction of the posterior nasal aperture leading into the nasopharynx Nasopharynx The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function. Pharynx: Anatomy. Choanal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) can manifest unilaterally or bilaterally. In the event of bilateral choanal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS), individuals will present with nasal obstruction and intermittent cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination after birth.

Traumatic conditions

• Epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis: can be loosely defined as a nosebleed, which can be an anterior bleed or a posterior bleed based on the site of origin. Epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis is very common in children (50% within the 1st 10 years of life) and is usually benign Benign Fibroadenoma and underreported, but a few cases can be related to neoplastic disease. Epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis usually occurs because of trauma to the nose from repeated nose picking, direct traumatic injury to the face or nose, or as a side effect of anticoagulant medications. Management consists of squeezing the nostrils together for 5 to 30 minutes along with head elevation while breathing through the mouth.
• Nasal bone fractures Bone fractures Breaks in bones. Bones: Remodeling and Healing: fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures of the bridge of the nose, which usually presents with nasal bleeding, swelling Swelling Inflammation, bruising, and nasal obstruction. Nasal bone fractures Bone fractures Breaks in bones. Bones: Remodeling and Healing may be complicated by other concomitant facial fractures and most commonly occur because of direct trauma Direct Trauma Toddler’s Fractures during athletic activities, falls, and motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vehicle collisions. 
• Cribriform plate fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures: usually the result of trauma and sometimes iatrogenic Iatrogenic Any adverse condition in a patient occurring as the result of treatment by a physician, surgeon, or other health professional, especially infections acquired by a patient during the course of treatment. Anterior Cord Syndrome because of inappropriate insertion of nasogastric tubes or nasal airways. The fractured plate can perforate the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy, causing leakage of CSF, which can lead to meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis, encephalitis Encephalitis Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. Encephalitis, and brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease. The olfactory bulb Olfactory bulb Ovoid body resting on the cribriform plate of the ethmoid bone where the olfactory nerve terminates. The olfactory bulb contains several types of nerve cells including the mitral cells, on whose dendrites the olfactory nerve synapses, forming the olfactory glomeruli. The accessory olfactory bulb, which receives the projection from the vomeronasal organ via the vomeronasal nerve, is also included here. Olfaction: Anatomy lies on top of the cribriform plate, and fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures can lead to its irreversible damage, resulting in anosmia Anosmia Complete or severe loss of the subjective sense of smell. Loss of smell may be caused by many factors such as a cold, allergy, olfactory nerve diseases, viral respiratory tract infections (e.g., COVID-19), aging and various neurological disorders (e.g., Alzheimer disease). Cranial Nerve Palsies.

Neoplastic conditions

• Nasal papilloma Papilloma A circumscribed benign epithelial tumor projecting from the surrounding surface; more precisely, a benign epithelial neoplasm consisting of villous or arborescent outgrowths of fibrovascular stroma covered by neoplastic cells. Cowden Syndrome: benign Benign Fibroadenoma epithelial tumors of the nasal cavity that mainly affect older males (45–60 years) and always require surgical excision. Risk factors include human papillomavirus Human papillomavirus Human papillomavirus (HPV) is a nonenveloped, circular, double-stranded DNA virus belonging to the Papillomaviridae family. Humans are the only reservoir, and transmission occurs through close skin-to-skin or sexual contact. Human papillomaviruses infect basal epithelial cells and can affect cell-regulatory proteins to result in cell proliferation. Papillomavirus (HPV) infection, smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, and chronic sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis. Individuals typically present with unilateral nasal obstruction, anosmia Anosmia Complete or severe loss of the subjective sense of smell. Loss of smell may be caused by many factors such as a cold, allergy, olfactory nerve diseases, viral respiratory tract infections (e.g., COVID-19), aging and various neurological disorders (e.g., Alzheimer disease). Cranial Nerve Palsies, and intermittent epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis. Diagnosis is based on biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma or surgical resection.
• Nasal polyps: noncancerous Noncancerous Benign Bone Tumors outgrowths of nasal mucosa, usually forming around the ostia of the maxillary sinuses. Associated conditions include allergic rhinitis Allergic rhinitis An inflammation of the nasal mucosa triggered by allergens. Rhinitis, aspirin Aspirin The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Nonsteroidal Antiinflammatory Drugs (NSAIDs) allergy Allergy An abnormal adaptive immune response that may or may not involve antigen-specific IgE Type I Hypersensitivity Reaction, asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma, cystic Cystic Fibrocystic Change fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, and sinus infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease. Symptoms may include trouble breathing through the nose (nasal obstruction), loss of smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy, decreased sense of taste, postnasal drip, and rhinorrhea Rhinorrhea Excess nasal drainage. Respiratory Syncytial Virus. Nasal polyps can be treated with topical or systemic glucocorticoids Systemic Glucocorticoids Glucocorticoids or with resection, though recurrence is common.