Logan Steele
Axial muscles are skeletal muscles that originate from the axial skeleton, which includes the 80 bones within the central core of the body, such as the skull, neck, back, and chest. These muscles are categorized as those of the trunk and head, blurring boundaries by crossing over to the appendicular skeleton, which includes the limbs. The axial muscles are further grouped based on location, function, or both. They play a crucial role in various functions, including facial expressions, swallowing, and speech, and are essential for protecting and cushioning vital organs, such as the brain and spinal cord.
| Characteristics | Values |
|---|---|
| Definition | Axial muscles are skeletal muscles of the trunk, head, neck, back, and eyeballs. |
| Grouping | Axial muscles are grouped based on location, function, or both. |
| Examples | Axial muscles include the orbicularis oris, depressor labii inferioris, depressor anguli oris, levator labii superioris, zygomaticus major and minor, and nasalis muscle. |
| Origin | Axial muscles originate on the axial skeleton, which consists of the bones in the head, neck, back, and chest. |
| Function | Axial muscles are involved in facial expressions, swallowing, breathing, speech, and protecting vital organs. |
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What You'll Learn
Axial muscles are skeletal muscles of the trunk and head
Axial muscles are skeletal muscles that are categorised based on their location and function. They are one of the two categories of skeletal muscles, the other being appendicular muscles. Axial muscles are those that are attached to the axial skeleton, which consists of 80 bones within the central core of the body, including the skull, ears, neck, back, and ribcage. These muscles are involved in protecting and cushioning vital organs such as the brain and spinal cord.
The axial muscles include the muscles of the trunk, head, neck, and back. They also include the muscles of the eyeballs and a group of muscles called hypobranchial muscles, which separate and migrate during development. Some axial muscles, such as those involved in facial expressions, originate on the surface of the skull and insert into the skin and connective tissue.
The muscles of the head and neck facilitate important functions such as eye movements, swallowing, breathing, and speech. For example, the muscles of the anterior neck work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down, aiding in swallowing and speech. The facial muscles are unique in that they create facial expressions by pulling on the skin rather than moving bones.
The axial muscles of the vertebral column, or spine, include 24 vertebrae, the sacrum, and the coccyx. The cervical vertebrae form the neck and support the head, the thoracic vertebrae form the rear anchor of the ribcage, and the lumbar vertebrae bear the body's weight and attach to the back muscles.
The axial muscles of the trunk, or torso, include the oblique and rectus muscles. These muscles provide stability and support to the body and are involved in movements such as bending and twisting. The axial muscles of the trunk work in coordination with the appendicular muscles of the arms and legs to enable a wide range of movements and postures.
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They are grouped based on location, function, or both
Axial muscles are skeletal muscles that originate on the axial skeleton, which includes the bones in the head, neck, and core of the body. The skeletal muscles are divided into axial and appendicular categories. The axial muscles include the muscles of the trunk, head, tail, eyeballs, and a group of muscles called hypobranchial muscles.
The axial muscles are grouped based on location, function, or both. The first grouping of the axial muscles includes the muscles of the head and neck, including those involved in eye movements and swallowing. These muscles work together to facilitate swallowing and speech. For example, the muscles of the anterior neck include the suprahyoid muscles, which pull up, and the infrahyoid muscles, which pull down on the hyoid bone.
The second grouping of the axial muscles includes the muscles of the vertebral column or spine, which is made up of 24 vertebrae, the sacrum, and the tailbone (coccyx). These muscles support the weight of the body and attach to the back muscles. Additionally, the origins of the muscles involved in facial expressions are on the surface of the skull, and their insertions have fibers intertwined with connective tissue and the dermis of the skin.
Some axial muscles may seem to blur the boundaries between location and function as they cross over to the appendicular skeleton, which includes the muscles of the arms and legs. For example, the orbicularis oris encircles the lips and can keep them tightly closed, while the depressor labii inferioris pulls the lip down, creating a frowning expression.
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They include muscles of the tail, trunk, and eyeballs
Axial muscles are skeletal muscles that originate on the axial skeleton, which includes the bones in the head, neck, and core of the body. They are grouped based on location, function, or both. These muscles include those of the trunk, tail, and eyeballs.
The muscles of the trunk are responsible for moving the vertebral column and include the muscles that form the thoracic and abdominal walls, as well as those covering the pelvic outlet. The erector spinae muscles, for example, are a large muscle mass on each side of the vertebral column that extends from the sacrum to the skull. They are crucial for maintaining erect posture. The intercostal muscles, located between the ribs, play a role in breathing, contracting during forced expiration and elevating the ribs during inspiration. The diaphragm, a dome-shaped muscle, separates the thorax from the abdomen.
The tail, a distinct, flexible appendage, is present in many vertebrate and some invertebrate animals. It serves various functions, including balance, communication, and protection. While humans do not have an external tail, they possess a tailbone (coccyx) attached to the pelvis, consisting of fused vertebrae.
The eyeballs are controlled by several muscles that enable a wide range of eye movements. These muscles include the extrinsic tongue muscles and the muscles of facial expression, which originate on the surface of the skull and insert into the skin, creating facial expressions and eye movements.
Overall, the axial muscles of the trunk, tail, and eyeballs play crucial roles in maintaining posture, facilitating movement, and enabling various functions specific to different species and anatomical structures.
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The first grouping includes muscles of the head and neck
Axial muscles are skeletal muscles that originate on the axial skeleton, including the bones in the head, neck, and core of the body. They are grouped based on location, function, or both. The first grouping of axial muscles includes those of the head and neck.
The human face possesses around 30 muscles on each side, which link the facial skin to the skull bone to enable important daily functions such as mastication (chewing) and emotional expression. Facial muscles are unique in that they create facial movements and expressions by pulling on the skin, without involving bone movements. These muscles of facial expression are often categorized as mimetic muscles, which are considered extensions of the face's superficial musculoaponeurotic system (SMAS). The SMAS runs from the neck platysma up to the galea aponeurotica and temporoparietal fascia under the scalp.
The frontalis muscle, for example, is connected to the occipitalis via the galea aponeurotica and is responsible for raising the eyebrows. In contrast, the corrugator supercilii depresses the eyebrows and causes vertical glabellar rhytides, commonly known as "frown lines." The orbicularis oculi sphincter muscles close the eyes, depress the brows, and produce "crow's feet" wrinkles at the corners of the eyes.
In addition to the facial muscles, the anterior neck muscles are also part of the first grouping of axial muscles. These muscles are arranged to facilitate swallowing and speech. They work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down. The neck also contains superficial neck muscles such as the sternocleidomastoid and trapezius.
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The axial skeleton is made up of 80 bones in the central core of the body
The axial skeleton is the part of the body's bony structure that consists of the bones in the skull, vertebral column, and rib cage. The word "axial" comes from "axis" and refers to the bones being located close to or along the central "axis" of the body. The axial skeleton includes 80 bones in the central core of the body, such as the skull, ears, neck, back, and rib cage.
The skull, which forms part of the axial skeleton, is made up of 22 bones. These include eight cranial bones that make up the top and back of the skull and 14 facial bones that form the lower front part of the skull. The cranial bones include the parietal, temporal, frontal, occipital, ethmoid, and sphenoid bones. The facial bones include the maxilla, zygomatic, nasal, palatine, nasal concha, lacrimals, and vomer bones, as well as the mandible or jaw bone.
The rib cage, another component of the axial skeleton, consists of 12 pairs of ribs, or 24 bones in total, plus the sternum or breastbone, bringing the total to 25 bones. The rib cage serves as a protective barrier for vital organs such as the heart and lungs. The ribs attach to the thoracic vertebrae at the back and connect to the sternum in the front via costal cartilage.
The vertebral column, which is also part of the axial skeleton, typically consists of 24 vertebrae in most adults. However, if we count the sacrum and coccyx as single vertebrae, the total number can range from 26 to 28 vertebrae. The vertebral column consists of cervical, thoracic, lumbar, sacral, and coccygeal vertebrae.
The axial skeleton serves to protect and support the brain, spinal cord, heart, lungs, and other vital organs. It also provides attachment sites for muscles that move the head, neck, and back, as well as muscles that act across the shoulder and hip joints to move the limbs.
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Frequently asked questions
Axial muscles are skeletal muscles that originate in the axial skeleton, which includes the bones in the head, neck, and core of the body.
Examples of axial muscles include the muscles of the trunk, head, neck, vertebral column, tail, eyeballs, and hypobranchial muscles.
Axial muscles are grouped based on their location, function, or both.
Axial muscles originate in the axial skeleton, while appendicular muscles originate in the bones that make up the limbs, such as the arms and legs.
Axial muscles involved in facial expressions originate on the surface of the skull and insert into the skin, allowing for movements like smiling, frowning, and puckering the lips.
