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Mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movable bone of the skull (discounting the ossicles of the middle ear). It is connected to the temporal bones by the temporomandibular joints. The bone is formed prenatal development, in the fetus from a fusion of the left and right mandibular prominences, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline. Like other symphyses in the body, this is a midline articulation where the bones are joined by fibrocartilage, but this articulation fuses together in early childhood.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, p. 59 The word "mandible" derives from the Latin word ''mandibula'', "jawbone" (literally "one used for chewing"), from ''wikt:mandere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angle Of The Mandible
__NOTOC__ The angle of the mandible (gonial angle) is located at the posterior border at the junction of the lower border of the ramus of the mandible. The angle of the mandible, which may be either inverted or everted, is marked by rough, oblique ridges on each side, for the attachment of the masseter laterally, and the pterygoideus internus (medial pterygoid muscle) medially; the stylomandibular ligament is attached to the angle between these muscles. The forensic term for the midpoint of the mandibular angle is the gonion. The gonion is a cephalometric landmark located at the lowest, posterior, and lateral point on the angle. This site is at the apex of the maximum curvature of the mandible, where the ascending ramus becomes the body of the mandible. The mandibular angle has been named as a forensic tool for gender determination, but some studies have called into question whether there is any significant sex difference in humans in the angle. See also *Ohngren's line Add ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facial Skeleton
The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull. The remainder of the skull is the braincase. In human anatomy and development, the facial skeleton is sometimes called the ''membranous viscerocranium'', which comprises the mandible and dermatocranial elements that are not part of the braincase. Structure In the human skull, the facial skeleton consists of fourteen bones in the face: * Inferior turbinal (2) * Lacrimal bones (2) * Mandible * Maxilla (2) * Nasal bones (2) * Palatine bones (2) * Vomer * Zygomatic bones (2) Variations Elements of the ''cartilaginous viscerocranium'' (i.e., splanchnocranial elements), such as the hyoid bone, are sometimes considered part of the facial skeleton. The ethmoid bone (or a part of it) and also the sphenoid bone are sometimes included, but otherwise considered part of the neurocranium. Because the maxillary bones are fused, they are often collectively listed as only one bone. The mandibl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, these two parts are the neurocranium and the viscerocranium ( facial skeleton) that includes the mandible as its largest bone. The skull forms the anterior-most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton. Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals, such as horned ungulates (mammals with hooves), the skull also has a defensive function by providing the mount (on the front ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tooth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the embryonic germ layer, the ectoderm. The general structure of teeth is similar across the vertebrates, although there is considerable variation in their form and position. The teeth of mammals have deep roots, and this pattern is also found in some fish, and in crocodilians. In most teleost fish, however, the teeth are attached to the outer surface of the bone, while in lizards they are attached to the inner surface of the jaw by one side. In cartilaginous fish, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depressor Anguli Oris
The depressor anguli oris muscle (triangularis muscle) is a facial muscle. It originates from the mandible and inserts into the angle of the mouth. It is associated with frowning, as it depresses the corner of the mouth. Structure The depressor anguli oris arises from the lateral surface of the mandible. Its fibres then converge. It is inserted by a narrow fasciculus into the angle of the mouth. At its origin, it is continuous with the platysma muscle, and at its insertion with the orbicularis oris muscle and risorius muscle. Some of its fibers are directly continuous with those of the levator anguli oris muscle, and others are occasionally found crossing from the muscle of one side to that of the other; these latter fibers constitute the transverse muscle of the chin. The depressor anguli oris muscle receives its blood supply from a branch of the facial artery. Nerve supply The depressor anguli oris muscle is supplied by the marginal mandibular branch of the facial nerve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depressor Labii Inferioris
The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle. It helps to lower the bottom lip. Structure The depressor labii inferioris muscle arises from the lateral surface of the mandible. This is below the mental foramen, and the origin may be around 3 cm wide. It inserts on the skin of the lower lip, blending in with the orbicularis oris muscle around 2 cm wide. At its origin, depressor labii is continuous with the fibers of the platysma muscle. Some yellow fat is intermingled with the fibers. Nerve supply The depressor labii inferioris muscle is supplied by the marginal mandibular branch of the facial nerve. Function The depressor labii inferioris muscle helps to depress and everts the lower lip. It is the most important of the muscles of the lower lip for this function. It is an antagonist of the orbicularis oris muscle. It is needed to expose the mandibular (lower) teeth during smiling. Clinical significance Resection The depressor labii ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Masseter Muscle
In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest. Structure The masseter is a thick, somewhat quadrilateral muscle, consisting of three heads, superficial, deep and coronoid. The fibers of superficial and deep heads are continuous at their insertion. Superficial head The superficial head, the larger, arises by a thick, tendinous aponeurosis from the temporal process of the zygomatic bone, and from the anterior two-thirds of the inferior border of the zygomatic arch. Its fibers pass inferior and posterior, to be inserted into the angle of the mandible and inferior half of the lateral surface of the ramus of the mandible. Deep head The deep head is much smaller, and more muscular in texture. It arises from the posterior third of the lower ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mental Foramen
The mental foramen is one of two foramina (openings) located on the anterior surface of the mandible. It is part of the mandibular canal. It transmits the terminal branches of the inferior alveolar nerve and the mental vessels. Structure The mental foramen is located on the anterior surface of the mandible. It is directly below the commisure of the lips, and the tendon of depressor labii inferioris muscle. It is at the end of the mandibular canal, which begins at the mandibular foramen on the posterior surface of the mandible. It transmits the terminal branches of the inferior alveolar nerve (the mental nerve), the mental artery, and the mental vein. Variation The mental foramen descends slightly in toothless individuals. The mental foramen is in line with the longitudinal axis of the 2nd premolar in 63% of people. It generally lies at the level of the vestibular fornix and about a finger's breadth above the inferior border of the mandible. In the general population, 17% ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mental Protuberance
The symphysis of the external surface of the mandible divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the ''mental tubercle The mandibular symphysis divides below and encloses a triangular eminence, the mental protuberance The symphysis of the external surface of the mandible divides below and encloses a triangular eminence, the mental protuberance, the base of which ...''. The size and shape of the bones making up this structure are responsible for the size and shape of a person's chin. Synonyms of ''mental protuberance'' include ''mental process'' and ''protuberantia mentalis.'' ''Mental'' in this sense derives from Latin ''mentum'' (chin), not ''mens'' (mind), source of the more common meaning of ''mental''. References * External links * Bones of the head and neck {{musculoskeletal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genioglossus
The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue. Structure Genioglossus is the fan-shaped extrinsic tongue muscle that forms the majority of the body of the tongue. It arises from the mental spine of the mandible and its insertions are the hyoid bone and the bottom of the tongue. The genioglossus is innervated by the hypoglossal nerve, as are all muscles of the tongue except for the palatoglossus. Blood is supplied to the sublingual branch of the lingual artery, a branch of the external carotid artery. The canine genioglossus muscle has been divided into horizontal and oblique compartments. Function The left and right genioglossus muscles protrude the tongue and deviate it towards the opposite side. When acting together, the muscles depress the center of the tongue at its back. Clinical significance Contraction of the genioglossus stabilizes and enlarges the porti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platysma
The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the neck, and a "bowstring" effect on either side of the neck. Structure The platysma muscle is a broad sheet of muscle arising from the fascia covering the upper parts of the pectoralis major muscle and deltoid muscle. Its fibers cross the clavicle, and proceed obliquely upward and medially along the side of the neck. This leaves the inferior part of the neck in the midline deficient of significant muscle cover. Fibres at the front of the muscle from the left and right sides intermingle together below and behind the mandibular symphysis, the junction where the two lateral halves of the mandible are fused at an early period of life (although not a true symphysis). Fibres at the back of the muscle cross the mandible, some being inserted into the bone below the oblique li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
