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Mandibular
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] |
Temporomandibular Joint
In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral synovial articulation between the temporal bone of the skull above and the mandible below; it is from these bones that its name is derived. This joint is unique in that it is a bilateral joint that functions as one unit. Since the TMJ is connected to the mandible, the right and left joints must function together and therefore are not independent of each other. Structure The main components are the joint capsule, articular disc, mandibular condyles, articular surface of the temporal bone, temporomandibular ligament, stylomandibular ligament, sphenomandibular ligament, and lateral pterygoid muscle. Capsule The articular capsule (capsular ligament) is a thin, loose envelope, attached above to the circumference of the mandibular fossa and the articular tubercle immediately in front; below, to the neck of the condyle of the mandible. Its loose attachment to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pharyngeal Arch
The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arches. In the human embryo, the arches are first seen during the fourth week of development. They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx. The vasculature of the pharyngeal arches is known as the aortic arches. In fish, the branchial arches support the gills. Structure In vertebrates, the pharyngeal arches are derived from all three germ layers (the primary layers of cells that form during embryogenesis). Neural crest cells enter these arches where they contribute to features of the skull and facial skeleton such as bone and cartilage. However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyn ... [...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 l ... [...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 facia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandibular Symphysis
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves of the mandible typically fuse at an early period of life (1-2 years). It is not a true symphysis as there is no cartilage between the two sides of the mandible. This ridge 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 lowest (most inferior) end of the mandibular symphysis — the point of the chin — is called the "menton". It serves as the origin for the geniohyoid and the 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 t ... [...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 low ... [...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 populatio ... [...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] |
Mandibular Prominence
The mandibular prominence is an embryological structure which gives rise to the lower portion of the face. The mandible and lower lip derive from it. The mesenchymal cells within the mandibular prominence condense to form Meckel's cartilage. It is innervated by the mandibular nerve In neuroanatomy, the mandibular nerve (V) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve ( ophthalmic nerve, maxillary nerve) which contain only .... References External links * Embryology {{musculoskeletal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chin
The chin is the forward pointed part of the anterior mandible ( mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a well-developed chin is considered to be one of the morphological characteristics of '' Homo sapiens'' that differentiates them from other human ancestors such as the closely related Neanderthals. Early human ancestors have varied symphysial morphology, but none of them have a well-developed chin. The origin of the chin is traditionally associated with the anterior–posterior breadth shortening of the dental arch or tooth row; however, its general mechanical or functional advantage during feeding, developmental origin, and link with human speech, physiology, and social influence are highly debated. Functional perspectives Robinson (1913) suggests that the demand to resist masticatory stresses triggered bone thickening in the mental region of the mandible and ultimately formed a ... [...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] |
Temporal Bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. The lower seven cranial nerves and the major vessels to and from the brain traverse the temporal bone. Structure The temporal bone consists of four parts— the squamous, mastoid, petrous and tympanic parts. The squamous part is the largest and most superiorly positioned relative to the rest of the bone. The zygomatic process is a long, arched process projecting from the lower region of the squamous part and it articulates with the zygomatic bone. Posteroinferior to the squamous is the mastoid part. Fused with the squamous and mastoid parts and between the sphenoid and occipital bones lies the petrous part, which is shaped like a pyramid. The tympanic part is relatively small and lies inferior to the squamous part, anterior to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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