Muscles, Soft Tissues, and Craniofacial Growth
D. Dixon Andrew, A.N. Hoyte David, Ronning Olli in Fundamentals of Craniofacial Growth, 2017
Similar distinctions can be made in species differences that mark human evolutionary history. A relationship between the size of certain components of the jaws and the use of the muscles of mastication seems tied to the acquisition of upright posture and differences in feeding habits. Two distinct species of australopithecine hominids show dramatic differences in skull form. A fuller description of them is given in Chapter 2. In short, Australopithecus africanus was a relatively delicate, “gracile” (slender) hominid with moderate-sized supraorbital tori, shallow protruding jaws, faint temporal lines with no evidence of a sagittal crest on the skull vault, and a small masseter muscle. The “robust” species, represented by Australopithecus robustus and A. boisei, possessed massive zygomatic arches and infratemporal fossae, bulky supraorbital ridges, and a thick sagittal crest. The body and ramus of the mandible were huge with a large area for the attachment of the masseter muscle, which when coupled with cheek teeth that had enormous occlusal surfaces, suggests specialization for a herbivorous diet.
Facial anatomy
Michael Parker, Charlie James in Fundamentals for Cosmetic Practice, 2022
The masseters are muscles of the cheek and lower jaw and are the primary muscles of mastication. They are important cosmetically as it is possible to make the face appear slimmer by administering botulinum toxin to the masseters. This treatment has, however, fallen out of favour due to the significant risk of localised (and permanent) osteoporosis of the mandible with subsequent fractures. They arise from the zygomatic and maxillary processes of the zygoma and insert on the coronoid process and lateral aspect of the mandibular ramus. Their arterial blood supply comes from the masseteric artery, which itself is a branch of the external carotid artery and passes over the mandibular notch, which is located between the coronoid process of the mandible and the temporomandibular joint. Unlike many other facial muscles, the masseters receive their nervous innervation from the trigeminal nerve or, more precisely, the V3 segment or mandibular nerve. See Figure 3.23.
Assessment – Nutrition-Focused Physical Exam to Detect Macronutrient Deficiencies
Jennifer Doley, Mary J. Marian in Adult Malnutrition, 2023
The temporalis muscle is one of the muscles of mastication and is located along the side of the head occupying the temporal fossa. Clenching and unclenching the jaws or teeth contracts this muscle. Standing directly in front of the patient, the examiner should inspect the temporalis muscle for signs of hollowing, scooping, or concave depression. To palpate the temporalis, ask the patient to clench the teeth for muscle engagement. Using the index and middle fingers, palpate the muscle over the temporal bone in a scooping motion forward, backward, and diagonally. In well-nourished patients, there will be ample temporalis muscle and no apparent hollowing or scooping. In severely malnourished patients, inspection will reveal hollowing temples with concave depression. Palpation of the engaged temporalis muscle will feel firm and rigid on well-nourished patients and will feel flaccid and limp in malnourished patients. See Figures 6.2–6.4.
Radiographic evaluation of the mandible to predict age and sex in subadults
Published in Acta Odontologica Scandinavica, 2022
With regard to the relationship between gonial angle size and age, the current study demonstrated a negative correlation. Despite variations in gonial angle among population groups [17], the majority of studies conducted with young subjects found significant decreases in gonial angle values with increases in age [31,32,37]. The gonial angle is formed by the line tangent to the lower border of the mandible and the line tangent to the distal border of the ascending ramus condyle. The shape of the mandibular base, especially the gonial angle, correlates with the function and shape of the muscles of mastication [38]. An increase in masseter force may play a role in reducing the size of the gonial angle in growing individuals. The smaller angle observed in older children may also be related to the posterior rotation of the mandible resulting from an age-related increase in ramus height.
Vesalius criticism on Galen’s musculoskeletal anatomy
Published in Acta Chirurgica Belgica, 2019
Konstantinos Markatos, Dimitrios Chytas, Georgios Tsakotos, Marianna Karamanou, Maria Piagkou, Elizabeth Johnson
In terms of the structure of muscles, Vesalius also expressed a different opinion from Galen’s. According to the latter, the muscle contained a mixture of ligaments and nerves, which are divided into fibers, creating an extended course with interstices that are covered with flesh [7,8]. In contrast, Vesalius argued that this flesh is the organ of motion and not simply the support of the aforementioned fibers. Moreover, concerning the muscles of mastication, Vesalius described separately temporalis and masseter, which were considered as a single muscle by Galen. Besides, lateral and medial pterygoid muscles were mentioned, as well as the digastric [1,8]. Vesalius also criticized Galen in terms of the description of the lateral flexion of the head, which, according to Galen, could be performed without the participation of the neck muscles [8].
Biomarkers in temporomandibular disorder and trigeminal neuralgia: A conceptual framework for understanding chronic pain
Published in Canadian Journal of Pain, 2020
Tina L. Doshi, Donald R. Nixdorf, Claudia M. Campbell, Srinivasa N. Raja
The simplistic perspective that TMD is a problem of inflammation and sensitization, whereas TN is a problem of nerve dysfunction, would suggest very different areas of biomarker research for the two conditions. However, chronic pain is never that simple, and some evidence suggests that inflammation could contribute to TN pain,58,59 and nerve dysfunction may play a role in TMD.60,61 Moreover, the same nerves can be involved in both conditions. Sensory innervation of the temporomandibular joint is supplied by the V3 branch of the trigeminal nerve, so in cases of TMD involving facial or joint pain, the trigeminal nerve is necessarily involved in pain transmission. The branches of the trigeminal also supply motor innervation to the muscles of mastication (masseter, temporalis, medial, and lateral pterygoids and anterior digastric); therefore, dysfunction of the trigeminal nerve may also lead to dysfunction of musculoskeletal structures involved in TMD. Identifying areas of overlap and dissimilarity in biomarkers for the two conditions has important implications for understanding which molecules may better serve as screening or diagnostic biomarkers and which are better suited as predictive biomarkers.
Related Knowledge Centers
- Hyoid Bone
- Lateral Pterygoid Muscle
- Mandible
- Masseter Muscle
- Medial Pterygoid Muscle
- Mylohyoid Muscle
- Temporal Bone
- Temporalis Muscle
- Chewing
- Sphenomandibularis