The Nasal Cavity & Paranasal Sinuses GN PDF

The Nasal Cavity & Paranasal Sinuses Biomedical Science Rhona Mann Intended Learning Outcomes By the end of the session students should be able to: To explore the structure of the nasal cavity and gain an understanding of its significance. To identify the position and clinical significanc...

The Nasal Cavity & Paranasal Sinuses Biomedical Science Rhona Mann Intended Learning Outcomes By the end of the session students should be able to: To explore the structure of the nasal cavity and gain an understanding of its significance. To identify the position and clinical significance of the various paranasal sinuses. To be able to demonstrate an understanding of the anatomy of these structures. To recognise the clinical significance of these structures in relation to health and disease. The Nasal Cavity The Nose is the primary sensory organ responsible for smell. It also plays a part in respiration and speech production. The NASAL CAVITY lies just behind the 2 nostrils and these form the interior of the nose. The nasal cavity makes up the respiratory system along with : 1. Paranasal Sinuses 2. Oral Cavity 3. Pharynx 4. Larynx. Vestibule Area lying just posterior to the nostrils. Part of the nasal cavity most exposed to the environment! Because of this exposure area is lined with multiple layers of “skin”: stratified squamous epithelium and this forms a protective barrier. This area has stiff hairs :VIBRISSAE. These are embedded in the cell lining and covered with thick mucus. Respiratory Region This begins at the end of the vestibular region and includes the entire nasal cavity, apart from the olfactory region. This region has a cilliated pseudo- stratified epithelium lining which contains goblet cells that secrete mucus forming the mucous membrane Olfactory Region This is located at the top part of the nasal cavity near the septum. It is lined with olfactory cells and olfactory mucosa. This mucosa houses millions of cilia containing olfactory receptor proteins that are responsible for the sense of smell. Walls and Boundaries of the Nasal Cavity Medial wall This refers to the septum dividing the nasal cavity into 2 equal sections. Bony upper & lower parts of the septum are formed by the perpendicular plate of the ethmoid bone and the Vomer. The lower front part is formed by a quadrangular Hyaline cartilaginous structure known as the SEPTUM CARTILAGE. The lower part of the smooth medial wall can be seen from the outside and is divided by the 2 nostrils  Superior border (roof) Anterior border (lateral wall) The 2 nasal bones, the lower part The lower parts of the nasal of the frontal bone, the cribiform bones, the cartilage attached to plate (of the ethmoid bone) and them, the outer nose and the the sphenoid bone, make up the nostrils are there in the front part roof. of the nasal cavity Posterior border (back wall) The upper back and sides are bordered with a number of cranial bones including the Maxilla, Ethmoid bone, Palatine bone, Sphenoid bone, Lacrimal bone as well as the: Inferior concha Floor: Apart from keeping the nasal cavity separated from the oral cavity, the hard palate, formed by the palatine process of the maxilla and the palatine bones ( horizontal plates) also make up its smooth floor  The nasal and oral cavities are connected with each other through the Nasopharynx (at the back of the throat) The soft palate and uvula (the fleshy projection at the back of the throat) together move up to close off this connection during eating to prevent food from entering the nasal cavity. Time for a break! During this break and after the Lecture investigate What is meant by the term pseudo –stratified in relation to Epithelium? What is the function of the Olfactory bulb? The Paranasal Sinuses These sinuses are air filled extensions of the nasal cavity. There are 4 of these sinuses, named according to the bone in which they are located: Maxillary, frontal, sphenoid & ethmoid Each sinus is lined with ciliated pseudostratified epithelium interspersed with mucus secreting goblet cells. 1. Frontal 2. Ethmoid 3. Sphenoid 4. Maxillary Paranasal Sinuses The function of these sinuses has been much debated but the following are considered the most logical: Lightening the weight of the head. Supporting the immune defence of the nasal cavity. Humidifying the inspired air. Increasing resonance of the voice. Paranasal sinuses continued…. The paranasal sinuses are formed during development by the nasal cavity eroding the surrounding bones. All the sinuses therefore drain back into the nasal cavity. Openings to the Paranasal sinuses can be found on the roof and lateral nasal walls. Frontal Sinuses There are 2 frontal sinuses located within the frontal bone of the skull. They are the most superior of the sinuses. Roughly triangular in shape. Drainage via the Frontonasal duct. Opens out at the Hiatus Semilunaris within the Middle meatus of the nasal cavity. Innervation: Supraorbital nerve( branch of the Ophthalmic) Blood supply : Anterior Ethmoid artery( branch of Internal Carotid) Sphenoid Sinuses These are situated within the Sphenoid bone. They open into the nasal cavity in an area superior/posterior to the Superior Concha known as the Spheno-ethmoidal recess. Innervation: Posterior Ethmoidal nerve ( branch of the Ophthalmic) and branches of the maxillary nerve. Blood supply: via the Pharyngeal branches of the maxillary arteries. Ethmoid Sinuses: There are 3 of these within the Ethmoid bone. Anterior: opens onto the Hiatus Semilunaris (Middle Meatus) Middle: Opens onto the lateral wall of the Middle Meatus. Posterior: Opens onto the lateral wall of the Superior Meatus. Innervation: Anterior & Posterior Ethmoid branches of the Nasociliary nerve and the maxillary nerve. Blood supply: Anterior Posterior Ethmoid arteries. Maxillary Sinuses Largest of the sinuses: located laterally and slightly inferior to the nasal cavity. Drain into the nasal cavity via the Hiatus Semilunaris underneath the Frontal Sinus opening. This is potentially a pathway for spread of infection: fluid drainage from the Frontal Sinus can enter the maxillary sinus. Innervation: Branches of the Alveolar Nerve plus the Infraorbital Nerve. Blood Supply: Branches of Alveolar Arteries plus Infraorbital and Greater Palatine Arteries. Clinical Relevance of the Paranasal Sinuses As the sinuses are continuous with the nasal cavity, an upper RESPIRATORY TRACT INFECTION can spread to the sinuses causing inflammation and pain : Sinusitis. Consider positioning of patient and use of aerosols if breathing is challenging The maxillary nerve supplies both the maxillary sinus and the maxillary teeth and inflammation of the maxillary sinus can present as TOOTHACHE.  Thank you for you attention. If there is anything you wish to discuss or have any questions at all please feel free to contact me: [email protected]