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Facial muscles are a group of flat skeletal muscles that lie just beneath the skin of the face and scalp. They are responsible for controlling facial expressions and are essential for chewing, smiling, pouting, frowning, and raising eyebrows. These muscles are innervated by the facial nerve and vascularized by the facial artery. On the other hand, hypaxial muscles are a distinct group of muscles found in the trunk of jawed vertebrates, primarily defined by their motor innervation patterns from the spinal cord. They include muscles with specialized functions and morphology, such as those associated with paired limbs, shoulder girdles, and tongue/infrahyoid muscles. Hypaxial muscles are located on the ventral side of the body and play a role in locomotion, prey-capturing, and respiration. So, while both facial muscles and hypaxial muscles are important for different bodily functions, facial muscles are not considered hypaxial muscles.
| Characteristics | Values |
|---|---|
| Location | Hypaxial muscles are located on the ventral side of the body, below the horizontal septum in many species, including fish and amphibians. |
| Innervation | Innervated by the ventral ramus (branch) of the spinal nerves. |
| Function | Responsible for locomotion, prey-capturing, and respiration. They include muscles with highly differentiated morphology and function, such as those associated with paired limbs, shoulder girdles, tongue/infrahyoid (hypobranchial) muscles, and the diaphragm. |
| Development | Controlled by specific regulatory genes, such as Pax3-positive dermomyotome supplying precursor cells and Lbx1 expression in limb buds. |
| Evolution | The differentiation of hypaxial and epaxial muscles is proposed to have evolved as a new trait in vertebrate animals, with a more complex and diverse evolutionary pathway in vertebrates compared to other types of skeletal muscles. |
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What You'll Learn
- Facial muscles are not hypaxial muscles
- Hypaxial muscles are located on the ventral side of the body
- Hypaxial muscles are responsible for locomotion, prey-capturing, and respiration
- Facial muscles are a group of flat skeletal muscles
- Hypaxial muscles include the tongue, shoulder girdles, and infrahyoid muscles
Facial muscles are not hypaxial muscles
Facial muscles are a group of flat, striated skeletal muscles that control facial expressions and movements of the face. They are located just under the skin, surrounding facial openings like the mouth, eyes, nose, and ears. These muscles are also called mimetic muscles and are only found in mammals. They are derived from neural crest cells, which are found in all vertebrates.
Hypaxial muscles, on the other hand, are a distinct group of muscles found in jawed vertebrates, primarily defined by their pattern of motor innervation from the spinal cord. They include muscles with highly differentiated morphology and functions, such as those associated with paired limbs, shoulder girdles, and tongue/infrahyoid (hypobranchial) muscles. Hypaxial muscles are located on the ventral side of the body and are responsible for locomotion, prey-capturing, and respiration.
While both facial muscles and hypaxial muscles are important for the structure and function of the body, they serve different purposes and are located in different regions. Facial muscles are specific to the face and are involved in facial expressions, chewing, and speaking. In contrast, hypaxial muscles are found in the trunk region of vertebrates and contribute to locomotion and other vital functions.
The distinction between epaxial and hypaxial muscles is more evident in cartilaginous and bony fish, where these muscle groups are separated by the horizontal myoseptum, a connective tissue sheet. In amniotes, which include mammals, birds, and reptiles, the hypaxial muscles contribute to the diaphragm, a component of the respiratory system. This distinction between epaxial and hypaxial muscles is essential for understanding the evolutionary development of various species and their adaptations to terrestrial life.
Therefore, it is clear that facial muscles are not hypaxial muscles. Facial muscles have a unique role in controlling facial expressions and movements specific to the face, while hypaxial muscles are involved in a broader range of functions related to the trunk and limbs of vertebrates.
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Hypaxial muscles are located on the ventral side of the body
The human body is an intricate system, with various muscles working together to enable movement and essential functions. Among these muscles, the hypaxial muscles form a distinct group with unique characteristics and roles.
The differentiation between hypaxial and epaxial muscles is more noticeable in cartilaginous and bony fish. In these species, the two muscle groups are separated by the horizontal myoseptum, a connective tissue sheet found on either side of the notochord. This distinction is important for their S-shaped swimming movement, where the coordinated contraction of these muscles enables graceful and efficient locomotion in water.
In the context of evolution, the development of hypaxial muscles is a relatively new trait in vertebrate animals. Their presence is essential for terrestrial life, with epaxial muscles specialized for posture maintenance and hypaxial muscles responsible for locomotion, prey-capturing, and respiration. The diaphragm, a component of the respiratory system, is an example of a hypaxial muscle that contributes to mammalian respiratory functions.
Facial muscles, on the other hand, are a separate group of muscles that are not specifically classified as hypaxial or epaxial. They are striated skeletal muscles supplied by the facial nerve (cranial nerve VII) and are responsible for controlling facial expressions. These muscles are unique to mammals and are derived from neural crest cells. Facial muscles include the buccolabial muscles around the mouth, nasal muscles, epicranial muscles of the forehead, skull, and neck, and the auricular muscles around the ears.
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Hypaxial muscles are responsible for locomotion, prey-capturing, and respiration
The human face contains almost 20 flat skeletal muscles, which are responsible for controlling facial expressions and chewing. These muscles are called craniofacial or mimetic muscles. They are supplied by the facial nerve (cranial nerve VII) and are the only muscles that attach to the dermis.
On the other hand, hypaxial muscles are a group of skeletal muscles that are primarily defined by the pattern of motor innervation from the spinal cord. They are found in jawed vertebrates and are associated with paired limbs, shoulder girdles, and tongue/infrahyoid muscles. The hypaxial group includes muscles with highly differentiated morphology and function.
The distinction between epaxial and hypaxial muscles is more evident in cartilaginous and bony fish, where they are separated by the horizontal myoseptum, a connective tissue sheet located on either side of the notochord. In amniotes, the hypaxial muscles include a variety of body wall muscles, limb muscles, and some members of the shoulder girdle muscles, such as the trapezius (cucullaris) muscles and tongue and infrahyoid muscles. The tongue and infrahyoid muscles are collectively known as hypobranchial muscles (HBMs).
The hypaxial muscles contribute to the mammalian diaphragm, a component of the respiratory system. Thus, the distribution of epaxial and hypaxial muscles in amniotes is well-suited for terrestrial life, with hypaxial muscles supporting a wide variety of locomotive, respiratory, and feeding movements.
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Facial muscles are a group of flat skeletal muscles
There are almost 20 flat skeletal muscles in the human face that attach to different places on the skull. They originate from the surface of the skull bone or fibrous structures of the skull and radiate to insert on the skin. The facial muscles are positioned around facial openings, such as the mouth, eyes, nose, and ears, or stretch across the skull and neck. They can be categorized by general location into groups such as buccolabial muscles, nasal muscles, epicranial muscles, auricular muscles, and orbital muscles.
The buccolabial muscles are in and around the mouth, and they control the shape and movements of the mouth and lips. The nasal muscles are around the nose, and the epicranial muscles are in the forehead, skull, and neck. The auricular muscles are around the ears, and the orbital muscles surround the eyes. These muscles receive signals from the brain via the facial nerve to function properly. However, when the facial muscles cannot receive these signals correctly, it can cause a droopy or sagging appearance in the face, facial palsy, facial paralysis, or trouble chewing, speaking, or making facial expressions.
Facial muscles are distinct from most other skeletal muscles in that they are flat, strap-like muscle sheets with interdigitations to the skin, short or absent tendons, and an absent fascial covering. They are the only muscles that attach to the dermis, and they are just under the skin (subcutaneous) muscles that control facial expressions. When the facial muscles contract, the skin moves, and wrinkles form at right angles to the muscles' action line.
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Hypaxial muscles include the tongue, shoulder girdles, and infrahyoid muscles
Jawed vertebrates, including humans, have two distinct groups of muscles in the trunk: epaxial and hypaxial muscles. These groups are defined by the pattern of motor innervation from the spinal cord. The hypaxial group includes muscles with highly differentiated morphology and function, such as the muscles associated with paired limbs, shoulder girdles, and the tongue and infrahyoid muscles (also known as hypobranchial muscles).
The tongue and infrahyoid muscles are called hypobranchial muscles because they develop from a bilateral pair of muscle primordia that extend rostrally from the anterior somites. These muscles are innervated by the hypoglossal nerve, which is homologous to the 12th cranial nerve in mammals. This innervation pattern, along with the developmental process, indicates that these muscles are indeed derived from the hypaxial portion of the anterior somites.
The hypaxial muscles, including the tongue, shoulder girdles, and infrahyoid muscles, play a crucial role in the respiratory system. They contribute to the mammalian diaphragm, which is essential for respiration. Additionally, these muscles are responsible for locomotion and prey-capturing in terrestrial environments.
Facial muscles, on the other hand, are a group of striated skeletal muscles that control facial expressions. They are derived from neural crest cells and are only found in mammals. Facial muscles include buccolabial muscles around the mouth, nasal muscles around the nose, epicranial muscles of the forehead, skull and neck, auricular muscles around the ears, and orbital muscles surrounding the eyes. These muscles work together to enable chewing, speaking, and forming various facial expressions.
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Frequently asked questions
Facial muscles are a group of about 20 flat skeletal muscles lying underneath the skin of the face and scalp. They are responsible for making facial expressions and controlling parts of the face.
Hypaxial muscles are a group of muscles that lie on the ventral side of the body, often below the horizontal septum. They include some vertebral muscles, the diaphragm, abdominal muscles, and all limb muscles.
No, facial muscles are not hypaxial muscles. Facial muscles are a separate group of muscles that are not associated with the trunk or limbs, which is where hypaxial muscles are located.
Some examples of facial muscles include the buccinator muscle, the orbicularis oris muscle, and the mentalis muscle.
Some examples of hypaxial muscles include the serratus posterior inferior and serratus posterior superior, as well as the tongue/infrahyoid (hypobranchial) muscles.
