Misplaced Pages

#103896

35-407: Cheeks are fleshy in humans, the skin being suspended by the chin and the jaws , and forming the lateral wall of the human mouth, visibly touching the cheekbone below the eye. The inside of the cheek is lined with a mucous membrane ( buccal mucosa, part of the oral mucosa ). During mastication (chewing), the cheeks and tongue between them serve to keep the food between the teeth. The cheek

70-464: A bony deficiency, commonly seen in people of normal weight. When the jaw bones ( mandible and by extension the maxilla ) do not project forward enough, the chin in turn will not project forward enough to give the impression of a defined jawline and chin. Despite low amounts of fat in the area, it can appear as if the chin is melting into the neck. The extent of this deficiency can vary drastically and usually has to be treated surgically. In some patients,

105-449: A degree, on both accounts… This should serve as motivation, not discouragement, for researchers to continue investigating this modern human peculiarity… perhaps understanding the chin will reveal some unexpected insight into what it means to be human." The terms cleft chin, chin cleft, dimple chin, or chin dimple refer to a dimple on the chin. It is a Y-shaped fissure on the chin with an underlying bony peculiarity. Specifically,

140-422: A mechanical advantage to resist lateral transverse bending and vertical bending in the coronal plane. On the contrary, others have suggested that the presence of the chin is not related to mastication. The presence of thick bone in the relatively small mandible may indicate better force resistance capacity. However, the question stands of whether the chin is an adaptive or nonadaptive structure. Recent works on

175-406: Is an inherited trait in humans and can be influenced by many factors. The cleft chin is also a classic example of variable penetrance with environmental factors or a modifier gene possibly affecting the phenotypical expression of the actual genotype . Cleft chins can be presented in a child when neither parent presents a cleft chin. Cleft chins are common among people originating from Europe,

210-458: Is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent. On the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen. The movement of nodding the head takes place predominantly through flexion and extension at

245-424: Is palpable from the skin surface. Sometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib , which develops from the anterior root of the transverse process. These ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein ) or nerves in the brachial plexus , causing pain, numbness, tingling, and weakness in

280-431: Is supplied with secretions from the buccal glands, which are arranged in superior and inferior groups. In carnivores, the superior buccal gland is large and discrete: the zygomatic gland. During mastication , the cheeks and tongue between them serve to keep the food between the teeth. Some animals such as squirrels and hamsters use the buccal pouch to carry food or other items. In some vertebrates , markings on

315-468: Is the most common location from which a DNA sample can be taken. (Some saliva is collected from inside the mouth, e.g. using a cotton-tipped rod called a swab or " Q-Tip ". The procedure of collecting a sample in that way is typically called a "cheek swab"). The cheeks are covered externally by hairy skin, and internally by stratified squamous epithelium . This is mostly smooth, but may have caudally directed papillae (e.g., in ruminants ). The mucosa

350-434: The atlanto-occipital joint between the atlas and the occipital bone . However, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself. This movement between the atlas and occipital bone is often referred to as the "yes joint", owing to its nature of being able to move the head in an up-and-down fashion. The movement of shaking or rotating

385-438: The hangman's fracture , both of which are often treated with immobilization in a cervical collar or halo brace . A common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital. This practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients. In clearing the cervical spine , Canadian studies have developed

SECTION 10

#1732779543104

420-444: The morphological changes of the mandible during development have shown that the human chin, or at least the inverted-T shaped mental region, develops during the prenatal period , but the chin does not become prominent until the early postnatal period . This later modification happens by bone remodeling processes ( bone resorption and bone deposition ). Coquerelle et al. show that the anteriorly positioned cervical column of

455-464: The vertebrae of the neck , immediately below the skull . Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals ) lie caudal (toward the tail) of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs . In lizards and saurischian dinosaurs, the cervical ribs are large; in birds , they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to

490-535: The vertebral artery , vertebral veins , and inferior cervical ganglion pass. The remainder of this article focuses upon human anatomy. By convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine. The general characteristics of the third through sixth cervical vertebrae are described here. The first, second, and seventh vertebrae are extraordinary, and are detailed later. The anterior tubercle of

525-464: The Middle East and South Asia. There is a possible genetic cause for cleft chins, a genetic marker called rs11684042, which is located in chromosome 2 . In Persian literature , the chin dimple is considered a factor of beauty and is metaphorically referred to as "the chin pit" or "the chin well": a well in which the poor lover is fallen and trapped. A double chin is a loss of definition of

560-432: The aesthetic deficit can be overcome with genioplasty alone; in others, the lack of forward growth might warrant orthognathic surgery to move one or two jaws forward. If the patient suffers from sleep apnea , early maxillomandibular advancement is usually the only causal treatment and necessary to preserve normal life expectancy. Cervical vertebrae In tetrapods , cervical vertebrae ( sg. : vertebra ) are

595-459: The cervical ribs of other amniotes . Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine. In humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which

630-420: The cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. C4 and C5 are the areas that see the highest amount of cervical spine trauma. If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm , which leads to respiratory failure . Common patterns of injury include the odontoid fracture and

665-471: The cervical vertebrae. For example, the cervical spinal nerve 3 (C3) passes above C3. The atlas (C1) and axis (C2) are the two topmost vertebrae. The atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine . It lacks a vertebral body, spinous process, and discs either superior or inferior to it. It is ring-like and consists of an anterior arch, posterior arch, and two lateral masses. The axis (C2) forms

700-449: The cheek area, particularly immediately beneath the eye, often serve as important distinguishing features between species or individuals . 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. The presence of a well-developed chin is considered to be one of

735-467: The chin fissure follows the fissure in the lower jaw bone that resulted from the incomplete fusion of the left and right halves of the jaw bone, or muscle, during the embryonal and fetal development. It can also develop during the later mandibular symphysis , due to growth of the mental protuberance during puberty, or as a result of acromegaly . In some cases, one mental tubercle may grow more than another, which can cause facial asymmetry. A cleft chin

SECTION 20

#1732779543104

770-442: The chin was formed as a consequence of the change in lifestyle humans underwent approximately 80,000 years ago. As humans' hunter-gatherer societies grew into larger social networks, territorial disputes decreased because the new social structure promoted building alliances in order to exchange goods and belief systems. Franciscus believes that this change in the human environment reduced hormone levels, especially in men, resulting in

805-441: The demand to resist masticatory stresses triggered bone thickening in the mental region of the mandible and ultimately formed a prominent chin. Moreover, Daegling (1993) explains the chin as a functional adaptation to resist masticatory stress that causes vertical bending stresses in the coronal plane . Others have argued that the prominent chin is adapted to resisting wishboning forces, dorso-ventral shear forces, and generally

840-427: The development of the chin suggests that the evolution of this unique characteristic was formed not by mechanical forces such as chewing but by evolutionary adaptations involving reduction in size and change in shape of the face. Holton et al. claim that this adaptation occurred as the face became smaller compared to that of other ancient humans. Robert Franciscus takes a more anthropological viewpoint: he believes that

875-448: The formation of osteophytes . The changes are seen on radiographs , which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4). Injuries to

910-491: The head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint . A small amount of rotation of the vertebral column itself contributes to the movement. This movement between the atlas and axis is often referred to as the "no joint", owing to its nature of being able to rotate the head in a side-to-side fashion. Cervical degenerative changes arise from conditions such as spondylosis , stenosis of intervertebral discs , and

945-409: The inverted-T shaped mental relief during early ages and the prominent chin later. The alveolar region (upper or superior part of the symphysis) is sculpted by bone resorption, but the chin (lower or inferior part) is depository in its nature. These coordinated bone growth and modeling processes mold the vertical symphysis present at birth into the prominent shape of the chin.   Recent research on

980-426: The jawbone or soft tissue under the chin. There are two possible causes for a double chin, which have to be differentiated. In overweight people, commonly the layer of subcutaneous fat around the neck sags down and creates a wrinkle , creating the appearance of a second chin. This fat pad is occasionally surgically removed and the corresponding muscles under the jaw shortened (hyoid lift). Another cause can be

1015-598: 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. Robinson (1913) suggests that

1050-409: The most prominent. The transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked. The upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation. The transverse foramen may be as large as that in the other cervical vertebrae, but it

1085-520: The natural evolution of the chin. Overall, human beings are unique in the sense that they are the only species among primates who have chins. In the paper The Enduring Puzzle of the Human Chin , evolutionary anthropologists James Pampush and David Daegling discuss various theories that have been raised to solve the puzzle of the chin. They conclude that "each of the proposals we have discussed falter either empirically or theoretically; some fail, to

Cheek - Misplaced Pages Continue

1120-450: The pivot on which the atlas rotates. The most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1. The body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra. The vertebra prominens , or C7, has a distinctive long and prominent spinous process, which

1155-462: The sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac ). This separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia . The carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus . The cervical spinal nerves emerge from above

1190-424: The spine and forward displacement of the hyoid bone limit the anterior–posterior breadth in the oral cavity for the tongue, laryngeal , and suprahyoid musculatures. Accordingly, this leads the upper parts of the mandible ( alveolar process ) to retract posteriorly, following the posterior movement of the upper tooth row, while the lower part of the symphysis remained protruded to create more space, thereby creating

1225-409: The upper limb, a condition known as thoracic outlet syndrome . Very rarely, this rib occurs in a pair. The long spinous process of C7 is thick and nearly horizontal in direction. It is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to. This process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be

#103896