Head, Eyes, Ears, Nose and Throat System
Anatomy and Physiology Review – Head, Eyes, Ears, Nose and Throat System
Head
The head comprises two specific parts: the face and the cranium (skull). There are 22 bones in the skull, and all structures of the face and skull are connected by immovable joints called sutures and connective tissue. The anterior portion of the skull makes up the face and consists of 14 facial bones. The temporal artery provides blood supply to the head (Betts et al., 2022).
The face houses the sinuses, air-filled cavities that reduce the overall weight of the skull and provide voice resonance (Thompson, 2022). There are four pairs of sinuses in the face: frontal, above the eyes (palpable); ethmoid, between the eyes deep in the skull (non-palpable); sphenoid, behind the nasal cavity (non-palpable); and maxillary, in cheekbones below the eyes (palpable).
Eyes
The internal and external structures of the eye work together to support human sight. Three cranial nerves are involved in vision (CN III, IV, VI). The perception of sight begins as light waves that travel from the cornea to the retina, where they are transformed into nerve impulses that travel to the brain via the optic nerve.
Extraocular structures include the eyebrows, eyelashes, eyelids, and lacrimal glands. The Intraocular structures include extraocular muscles, aqueous humor, choroid, iris, lens, pupil, posterior chamber, cornea, fundus, macula, optic disc, and the retina and its accompanying blood vessel structure (Betts et al., 2018; Thompson, 2018).
Ears
The ear is essentially a three-part structure. The first part is the outer ear and the ear canal. The second is the middle ear, located directly behind the tympanic membrane. Three small bones are in this area: the malleus, the incus, and the stapes. The third part is known as the inner ear. This part of the ear functions to control hearing and balance. The inner ear structures include the cochlea, semi-circular canals (labyrinth), and the vestibule. The third part is the inner ear. Each part of the ear has a specific function: the outer ear collects, and channels sound into the ear canal; the middle ear separates the ear canal from the inner ear and ensures that adequate amounts of sound energy are picked up by the fluid in the cochlea. The inner ear translates sound energy into recognizable information and regulates balance (Betts et al., 2022).
Nose
The nose comprises bone and cartilage and is physiologically part of the upper respiratory system. Internal structures of the nose include the nares, the nasal septum, the turbinates, and the adenoids. The turbinates are mucous membrane-covered bone structures, and the adenoids are clusters of lymphatic tissue (Thompson, 2018).
The oral cavity houses the hard and soft palates, the mandible, Stenson’s ducts (parotid duct), and Wharton’s ducts. Stenson’s ducts allow saliva to flow from the parotid gland into the mouth, whereas Wharton’s ducts transport saliva from the