The paranasal sinuses are four sets of cavities situated around and connected to the nose. Lined by ciliated columnar epithelium, they help produce mucous (when stimulated by parasympathetic innervation) for the nasal cavity with which they are connected. They also likely function to lighten the skull and act as resonance chambers for speech. Each sinus is innervated by CN V and named by the bone it … Continue reading Paranasal sinuses
The nasal cavity receives blood from three sources: Sphenopalatine and greater palatine arteries, branches of the maxillary artery Anterior and posterior ethmoidal arteries, branches of the ophthalmic artery Superior labial artery, branch of the facial artery CLINICAL CORNER Little’s area is a site of anastomoses between the nasal arteries. Nosebleed commonly occurs here due to drying out and fingernail trauma. Veins follow the course of … Continue reading Nose blood vessels
The spinal cord begins at the foramen magnum and ends at the lower border of L1, tapering (as nerve roots are given off) from the cervical enlargement to the conus medullaris at the end. The conus medullaris is attached by a stalk of pia mater, the filum terminale, to the end of the dural sac at S2. It also gives rise to the cauda equina, … Continue reading Spinal cord
The eye is a specialised organ which collects and transmits visual information from the environment to the brain. A ~2.5 cm diameter sphere, it comprises of an anterior (cornea to lens) and a posterior segment (lens to optic nerve). Entering light is refracted by the cornea and lens onto the retina where it is detected by photoreceptors. Protected by the bony orbit, eyelids and lacrimal … Continue reading Eye
The upper and lower eyelids are movable folds which protect the eye from foreign material. Superficial to deep, layers of the eyelids generally include skin, loose connective tissue, fibres of the orbicularis oculi, the tarsal plates (Meibomian glands within) and conjunctiva. The corners formed by the upper and lower lids are the medial and lateral canthi while the opening in between is the palpebral fissure. … Continue reading External eye: eyelids, conjunctiva
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