Anatomy & physiological functions of Respiratory system
What is Respiratory system?
The respiratory system comprises the respiratory tract, nose, pharynx , larynx, trachea and bronchi which are the means whereby air is introduced to the lungs.The respiratory element of the system where gaseous exchange occurs comprises the respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli.
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The respiratory tract is divided into the upper respiratory tract which is the nose and the pharynx and the lower respiratory tract which is the larynx, trachea and bronchi.
ANATOMY OF THE FACIAL BONES
Nose
The nose has a bony element formed by the nasal bones which is that part most proximal to the skull and the distal elements which are formed on a base of hyaline cartilage.
The internal nose is formed of the cranio facial bones lying inferior to the nasal bone and superior to the mouth.
The roof of the nose is formed by the ethmoids. The floor is formed by the palatine bones and the palatine process of the maxilla on each side. They form the hard palate. The lateral walls are formed by the ethmoid, the maxillae and the lateral, palatine and inferior conchae bones. The nasal cavity thus formed is divided by a vertical partition, the nasal septum. Anteriorly this is cartilaginous and posteriorly it is formed by the perpendicular plate of the ethmoid and the vomer.
The roof of the ethmoid is perforated through which the olfactory nerve passes from its receptors in the nose through skull to form the olfactory nerve.
The paranasal sinuses are cavities within the cranial and facial bones around the nasal cavity. These sinuses are found in the frontal and sphenoid bones of the cranial cavity and the ethmoid and maxillary bones of the facial skeleton.The ethmoid bone in its vertical portion, forming the lateral wall of the nose is shelved forming the superior and middle turbinates along with the inferior turbinate.
The paranasal sinuses drain into the lateral wall of the nasal cavity as does the nasolacrimal duct.
The function of the nose is threefold. Incidental to its function as part of the respiratory tract, it plays a part in voice modification through the paranasal sinuses which act as a resonance chamber and in the sense of smell where receptor cells and the roof of the ethmoid are the end organs of the olfactory nerve which passes into the brain through fine perforations in the roof of the ethmoid (the cribriform plate).
Hence, frontal injuries can damage this plate and produce a leak of cerebral spinal fluid which then emerges as a nasal CSF leak.
As an organ of respiration, the function of the nose to filter, to warm and to humidity the air. In the cartilaginous part of the nose, hair bearing skin filter out the larger dust particles . On passing into the internal nose, turbulence is produced by the turbinates. The internal part of the nose contains a ciliated mucus membrane possessed of a large capillary bed. The blood in the capillaries warms the air, the mucus secreting cells moisten the air and trap dust. The moistening of the air is aided by drainage from the paranasal and lacrimal ducts.
The trapped particles are wafted by the cilia to where they can be spat out or swallowed
Maxillofacial Anatomy
The bones forming the maxillofacial complex are the nasal bones, the maxillae the zygomatic bone, the lacrimal bones, the palatine bones, the inferior nasal conchae and the vomer. The nasal bone, inferior conchae and the vomer have been considered under the section on the nose. The form respectively part of the lateral wall of the nasal cavity. The inferior nasal conchae are part of the lateral wall of the nasal cavity and the nasal bones form the bony part of the nose and upper part of the septum while the vomer forms the lower part.
The maxillae form the upper jaw. The alveolar part contain sockets for the upper teeth. The horizontal projection of each part of the maxilla meet in the mid-line to form the anterior three-quarters of the hard palate. The posterior element is formed by the palatine bones. The palate divides the nasal from the oral cavities and thus forms part of the lateral walls and the floor of the nasal cavity. The maxilla also forms part of the floor of the orbit as does the lacrimal and ethmoid bones. The rest of the orbit is formed by the frontal bones, the sphenoid and the zygomatic bone.
The orbit therefore contains the roof and parts of the frontal and sphenoid bones.
The lateral wall is formed by parts of the zygomatic and the sphenoid bones, and the floor is formed by parts of the maxilla, the zygomatic and palatine bones. And the medial wall is formed by parts of the maxilla and the lacrimal, ethmoid and sphenoid bone. In the back of the orbit there are two fissures, Superior and honor orbital fissures, which transmit the cranial nerves concomed with ocular movement (3, 4 and 6) and the trigeminal nerve and the infraorbital vessels.
The mandible or lower jaw bone articulates with the skull at the Temporomandibular joint. The cranial element of this joint is formed by the temporal bone. It articulates with a condylar process of the mandible.
The coronoid process is an area for muscular attachment. This vertical and articulatory part of the mandible is known as the ramus. It meets at the angle of the body of the mandible. The body of the mandible contains the sockets for the lower teeth. The mental nerve runs in the mandible and is accessible at the mental foramen laterally and the mandibular foramen medially. The tongue is attached to the mandible anteriorly.
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