Facial Muscles of Hylobatids

muscles of the face

This study focuses on the facial musculature of hylobatids and compares its presence and absence to that of chimpanzees and rhesus macaques. The results revealed that the presence/absence of various muscles varies little between specimens. In addition, a previous study showed that fascia is sparsely interspersed amongst muscles.

Circular and radial muscles

The facial muscles serve two primary purposes. The first is to move the mandible and the other serves to hold the mandible in place. The muscles of the face originate from the bones of the face. The bones are made up of two-thirds mineral matter and account for about fourteen to twenty percent of the body weight. The largest bones are the mandible and the zygomatic. The radial and circular muscles of the face arise from these bones.

Oral muscles

The oral muscles of the face have different functions. Most of them are located in the mouth. For example, the levator anguli oris is responsible for smiling. Its fibers originate from the oblique line of the mandible and course upward. They are supplied by the mandibular branch of the facial nerve.


The Buccinator muscles of the face are involved in chewing and a variety of other facial expressions. A typical expression involves compressing the cheeks against the teeth. The movement can also be indicative of various moods, including playfulness, love, and affection.

Zygomaticus minor

The zygomaticus minor muscle is one of the muscles of the face and is located between the ears and mouth. This muscle is a key component of smiling facial expressions. It is innervated by the buccal branch of the facial nerve (CN VII) and supplied by the superior labial branch of the facial artery.

Orbicularis oris

The Orbicularis oris muscle is a complex group of muscles in the face. The main supply of blood to the muscle comes from the facial artery. This artery is divided into several branches: superior labial, inferior labial, transverse facial, and maxillary. It contains 8 segments, which open in peripheral areas and close in marginal areas. Its name is derived from its function as a sphincter, which is a circular muscle used as a gate. Its neural supply is derived from the mandibular nerve and buccal nerve.

Risorius muscle

The Risorius is a muscle of the face that is located in the superficial layer of facial muscles. It is bounded by the buccinator muscle, the masseter muscle, and the buccopharyngeal fascia. It is attached to the facial nerve by the masseter tendon.

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