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mandible
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What is the mandible?
The mandible, or lower jaw, is a movable bone that forms the lower part of the skull in humans and other mammals. In humans, it is the only mobile bone of the skull (besides the tiny bones of the middle ear). It works in conjunction with the maxilla (upper jaw) for biting, chewing, and handling food.
The human mandible resembles a horizontal arch that houses teeth, blood vessels, and nerves. At the rear are two vertical portions (rami) that form movable hinge joints, which articulate with the temporal bone of the skull, enabling jaw movements. The center front is thickened, forming the chin, a feature unique to humans. In human fetuses and infants, the mandible is initially separated at the midline, fusing shortly after birth.
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Where is the mandible located in the human body?
The mandible, or lower jaw, is a movable bone in the skull located below the upper jaw (maxilla). In humans, it appears as a horizontal arch that houses teeth, nerves, and blood vessels. The mandible connects to the temporal bone of the skull via two vertical portions (rami) that form temporomandibular joints on each side of the head, enabling chewing and mouth movements. The chin is a unique, thickened part of the mandible. The mandible is the only mobile bone of the skull, excluding the ossicles of the middle ear.
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Why is the mandible important for eating and speaking?
The mandible, or lower jaw, is essential for both eating and speaking. As the skull's only mobile bone (besides the tiny bones of the middle ear), it moves in opposition to the maxilla (upper jaw), enabling biting, chewing, and food handling. The masseter muscle, attached to the mandible, is key in raising the jaw for chewing. The mandible's varied movements, facilitated by joints connecting it to the temporal bone, are also critical for speech.
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What are the main parts of the mandible?
The mandible, or lower jaw, consists of a horizontal body and two vertical rami (branches).
- Body The body is the horizontal, central part of the mandible. The upper portion of the body is the alveolar margin that holds the teeth. The projecting chin is unique to humans. On either side of the chin is the mental foramen, an opening for the mental branch of the mandibular nerve.
- Rami The ascending parts on the sides of the mandible are called rami. The condyle, a rounded knob at the upper back corner of each ramus, connects to the glenoid fossa in the temporal bone, enabling jaw movements. The coronoid process, a sharp projection at the top front of each ramus, does not form a joint but serves as an attachment for the temporalis muscle.
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How does the mandible move and what joint allows this movement?
The mandible, or lower jaw, moves through hinge joints connecting it to the temporal bone of the skull, known as the temporomandibular joints (TMJ). These joints, located on each side of the head, allow the mandible to move in opposition to the maxilla (upper jaw), enabling biting, chewing, and handling food.
The movement is facilitated by muscles attached to the mandible, including the temporalis, masseter, and pterygoid muscles, which work together to elevate the mandible and achieve a bite. The structure of the mandible includes a horizontal arch that holds the teeth, as well as vertical portions (rami) that form the movable hinge joints.
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What are some common injuries or problems that can affect the mandible?
The most common conditions that affect the function of the mandible (lower jaw) are temporomandibular joint disorders (TMDs), of which there are about 30 different types. TMDs may impact the function of the jaw muscles and the temporomandibular joints and may irritate associated nerves.
The cause of TMDs is often unclear; however, factors that may play a role include osteoarthritis and physical trauma. Symptoms vary but may include dizziness, earache, facial pain, headache, jaw tenderness, and reduced jaw mobility. Many TMDs resolve on their own; otherwise, treatment ranges from simple dietary changes (such as eating only soft foods) to physical therapy or medication and the use of intraoral appliances (devices fitted over the teeth) to complex surgical or dental procedures.
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mandible, in anatomy, the movable lower jaw, consisting of a single bone or of completely fused bones in humans and other mammals. In birds, the mandible constitutes either the upper or the lower segment of the bill, and in invertebrates it is any of the various mouthparts that holds or bites food materials, including either of the paired mouth appendages of an arthropod that form the biting jaws.
In humans, the mandible is the only mobile bone of the skull (other than the tiny bones of the middle ear). It is attached to muscles involved in chewing and other mouth movements and functions by moving in opposition to the maxilla (upper jaw); together, the two parts are used for biting, chewing, and handling food. The structure of the human mandible resembles a more or less horizontal arch, which holds the teeth and contains blood vessels and nerves. At the rear of the mandible, two more or less vertical portions (rami) form movable hinge joints, one on each side of the head, articulating with the glenoid cavity of the temporal bone of the skull to form the temporomandibular joints. The rami also provide attachment for muscles important in chewing. The centre front of the arch is thickened and buttressed to form the chin, a development unique to humans and some of their recent ancestors; the great apes and other animals lack chins. In the human fetus and infant, the maxilla and the mandible are each separated at the midline; the halves fuse a few months after birth.
Invertebrate jaw and mouthpart structures vary markedly. For example, in the primitive bloodsucking flies (e.g., the horse fly [Tabanus]), the mandibles and maxillae form serrated blades that cut through the skin and blood vessels of the host animal. In the mosquito (Culicidae), the mandibles and associated structures have become exceedingly slender stylets that form a fine bundle used for piercing skin and entering blood vessels. In the housefly (Musca domestica), the mandibles and maxillae have been lost; the tonguelike labium alone remains and serves for feeding on exposed surfaces. Among crustaceans, processes at the base of the antennae may help the mandibles push food into the mouth. The paired mandibles of a nauplius (the most widespread and typical crustacean larva to emerge from the egg) each have two branches, one with a chewing lobe and the other with a compressing lobe at the base; the mandibles may also be used for swimming. In the adult crustacean, each mandible loses one of the branches, sometimes retaining the other as a palp, and the base may develop into a powerful jaw. An alternative development is found in some of the blood-sucking parasites, in which the mandibles form needlelike stylets for piercing a host.
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In humans, the most common conditions that affect the function of the mandible are temporomandibular joint disorders (TMDs), of which there are about 30 different types. TMDs may have an impact on the function of the jaw muscles and the temporomandibular joints and may irritate associated nerves. The cause of a TMD is often unclear; factors that may play a role include osteoarthritis and physical trauma. Symptoms vary but may include dizziness, earache, facial pain, headache, jaw tenderness, and reduced jaw mobility. Many TMDs resolve on their own; otherwise, treatment ranges from simple dietary changes (e.g., eating only soft foods) to physical therapy or medication to the use of intraoral appliances (devices fitted over the teeth) to complex surgical or dental procedures.