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Frontal Nerve
The frontal nerve is the largest branch of the ophthalmic nerve (V1), itself a branch of the trigeminal nerve (CN V). It supplies sensation to the skin of the forehead, the mucosa of the frontal sinus, and the skin of the upper eyelid. It may be affected by schwannoma. Structure The frontal nerve is a branch of the ophthalmic nerve (V1), itself a branch of the trigeminal nerve (CN V). The frontal nerve branches immediately before entering the superior orbital fissure. In then travels superolateral to the annulus of Zinn between the lacrimal nerve and inferior ophthalmic vein. After entering the orbit it travels anteriorly between the roof periosteum and the levator palpebrae superioris. Midway between the apex and base of the orbit it divides into two branches, the supratrochlear nerve and supraorbital nerve. Functions The two branches of the frontal nerve provide sensory innervation to the skin of the forehead, mucosa of the frontal sinus (an air sinus), and the skin of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ocular Muscles
The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye. The other muscle, the levator palpebrae superioris, controls eyelid elevation. The actions of the six muscles responsible for eye movement depend on the position of the eye at the time of muscle contraction. The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle sometimes are called intrinsic ocular muscles or intraocular muscles. Structure Since only a small part of the eye called the fovea provides sharp vision, the eye must move to follow a target. Eye movements must be precise and fast. This is seen in scenarios like reading, where the reader must shift gaze constantly. Although under voluntary control, most eye movement is accomplished without conscious effort. Precisely how the integration between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annulus Of Zinn
The common tendinous ring, also known as the annulus of Zinn or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of extraocular muscles. It can be used to divide the regions of the superior orbital fissure. The arteries surrounding the optic nerve form a vascular structure known as the circle of Zinn-Haller, or sometimes as the ''circle of Zinn''. The following structures pass through the tendinous ring (superior to inferior): * Superior division of the oculomotor nerve (CNIII) * Nasociliary nerve (branch of ophthalmic nerve) * Inferior division of the oculomotor nerve (CNIII) * Abducens nerve (CNVI) * Optic nerve Parts The common tendinous ring spans the superior orbital fissure and can be described as having two parts – an inferior tendon which gives origin to the inferior rectus muscle, and to part of the lateral rectus muscle; and a superior ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CT Scan
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists. CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry (medical), gantry to measure X-ray Attenuation#Radiography, attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce Tomography, tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is Contraindication, contraindicated. Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frontal Bone
In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part of the bony orbital cavity holding the eye, and part of the bony part of the nose respectively. The name comes from the Latin word ''frons'' (meaning "forehead"). Structure The frontal bone is made up of two main parts. These are the squamous part, and the orbital part. The squamous part marks the vertical, flat, and also the biggest part, and the main region of the forehead. The orbital part is the horizontal and second biggest region of the frontal bone. It enters into the formation of the roofs of the orbital and nasal cavities. Sometimes a third part is included as the nasal part of the frontal bone, and sometimes this is included with the squamous part. The nasal part is between the brow ridges, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Part Of Frontal Bone
The orbital or horizontal part of the frontal bone (''pars orbitalis'') consists of two thin triangular plates, the orbital plates, which form the vaults of the orbits, and are separated from one another by a median gap, the ethmoidal notch. Surfaces * The inferior surface of each orbital plate is smooth and concave, and presents, laterally, under cover of the zygomatic process, a shallow depression, the lacrimal fossa, for the lacrimal gland; near the nasal part is a depression, the fovea trochlearis, or occasionally a small trochlear spine, for the attachment of the cartilaginous pulley of the obliquus oculi superior. * The superior surface is convex, and marked by depressions for the convolutions of the frontal lobes of the brain, and faint grooves for the meningeal branches of the ethmoidal vessels. ** The ethmoidal notch separates the two orbital plates; it is quadrilateral, and filled, in the articulated skull, by the cribriform plate of the ethmoid. *** The margins o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supraorbital Notch
The supraorbital foramen, is a bony elongated opening located above the orbit (eye socket) and under the forehead. It is part of the frontal bone of the skull. The supraorbital foramen lies directly under the eyebrow. In some people this foramen is incomplete and is then known as the supraorbital notch. Structure The supraorbital foramen is a small groove at superior and medial margin of the orbit in the frontal bone. It is part of the frontal bone of the skull. It arches transversely below the superciliary arches and is the upper part of the brow ridge. It is thin and prominent in its lateral two-thirds, but rounded in its medial third. Between these two parts, the supraorbital nerve, the supraorbital artery, and the supraorbital vein pass. The supraorbital nerve divides into superficial and deep branches after it has left the supraorbital foramen. Additional images File:Gray135.png, Frontal bone. Inner surface. File:Gray1193.svg, Side view of head, showing surface relati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myelin
Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Myelin ensheaths part of an axon known as an internodal segment, in multiple myelin layers of a tightly regulated internodal length. The ensheathed segments are separated at regular short unmyelinated intervals, called nodes of Ranvier. Each node of Ranvier is around one micrometre long. Nodes of Ranvier enable a much faster rate of conduction known as saltatory conduction where the action potential recharges at each node to jump over to the next node, and so on till it reaches the axon terminal. At the terminal the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supratrochlear Nerve
The supratrochlear nerve is a branch of the frontal nerve, itself a branch of the ophthalmic nerve (CN V1) from the trigeminal nerve (CN V). It provides sensory innervation to the skin of the forehead and the upper eyelid. Structure Origin The supratrochlear nerve is the smaller of the two terminal branches of the frontal nerve (the other being the supraorbital nerve). It arises midway between the base and apex of the orbit where the frontal nerve splits into said terminal branches. Course The supratrochlear nerve passes medially above the trochlea of the superior oblique muscle. It then travels anteriorly above the levator palpebrae superioris muscle. It exits the orbit through the supratrochlear notch or foramen. It then ascends onto the forehead beneath the corrugator supercilii muscle and frontalis muscle. It finally divides into sensory branches. The supratrochlear nerve travels with the supratrochlear artery, a branch of the ophthalmic artery. Branches Be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Levator Palpebrae Superioris Muscle
The levator palpebrae superioris () is the muscle in the orbit that elevates the upper eyelid. Structure The levator palpebrae superioris originates from inferior surface of the lesser wing of the sphenoid bone, just above the optic foramen. It broadens and decreases in thickness (becomes thinner) and becomes the levator aponeurosis. This portion inserts on the skin of the upper eyelid, as well as the superior tarsal plate. It is a skeletal muscle. The superior tarsal muscle, a smooth muscle, is attached to the levator palpebrae superioris, and inserts on the superior tarsal plate as well. Blood supply The levator palebrae superioris receives its blood supply from branches of the ophthalmic artery, specifically, muscular branches and the supraorbital artery. Blood is drained into the superior ophthalmic vein. Nerve supply The levator palpebrae superioris receives motor innervation from the superior division of the oculomotor nerve. The smooth muscle that originates from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inferior Ophthalmic Vein
The inferior ophthalmic vein is a vein of the orbit that - together with the superior ophthalmic vein - represents the principal drainage system of the orbit. It begins from a venous network in the front of the orbit, then passes backwards through the lower orbit. It drains several structures of the orbit. It may end by splitting into two branches, one draining into the pterygoid venous plexus and the other ultimately (i.e. directly or indirectly) into the cavernous sinus. Structure The inferior ophthalmic vein - together with the superior ophthalmic vein - represents the principal drainage system of the orbit. It forms/represents a connection between facial veins, and intracranial veins. It is valveless. Origin The inferior ophthalmic vein originates from a venous network at the anterior part of the floor and anterior part of the medial wall of the orbit. Course The inferior ophthalmic vein passes posterior-ward through the inferior orbit upon the inferior rectus muscle. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
