The Muscles of the Neck and Trunk
The Muscles of the Neck
Regions of the Neck To facilitate the seemingly complicated
area, the neck is divided into two major areas, or triangles, by the sternocleidomastoid muscle. These are:
1. anterior triangle - the area anterior to the SCM and
below the inferior border of the mandible.
2. posterior triangle - the area posterior to the SCM and
is limited posteriorly by the trapezius muscle.
Sternocleidomastoid Muscle
Muscle Action
Sternocleidomastoid muscle Bilateral:Flex the neck
Single:Flex the head and laterally rotate to the opposite side
Trapezius Muscle
Muscle Action
Trapezius muscle Contract to rotate and elevate the scapula Its cervical portion, acting bilaterally, can extend the head and singly, it can rotate the head and face to the opposite side
I. Infrahyoid Muscles
Muscle Action
Omohyoid Depresses the hyoid bone and larynx
Sternohyoid Depresses the hyoid bone and larynx
Sternothyroid Depresses the larynx
Thyrohyoid Depresses the hyoid bone
II. Suprahyoid MusclesMuscle Action
Stylohyoid Elevates hyoid bone
Digastric(Posterior belly)
Raises the hyoid bone
Digastric(anterior belly)
Elevates the hyoid bone
Suprahyoid MusclesMuscle Action
Mylohyoid Elevates the hyoid bone, base of the tongue, and floor of the mouth
Geniohyoid muscle Elevates hyoid bone, protracts hyoid bone
The lateral muscles of the neck
Muscle Action
Platysma Stretches tight the skin of the neck, depresses the mandible
Splenius capitis Bilateral:Extends the headIndividual:Flexes the head laterally
Muscle ActionLevator scapulae Elevates and rotates the
scapula
Scalenius posterior Flexes the neck
Scalenius Medius Flexes the neck
Scalenius anterior Participates in forced inspiration by elevating the ribs and sternum
The Muscles of the Trunk
1. Deep Muscles of the Back
Collectively these muscles control the vertebral column
Muscle Action
Semispinalis thoracis cervicis capitis
Extend the vertebral column and the head; rotate them to the opposite side.
Mulitifudus Extend the vertebral column; rotates it to the opposite side.
Rotatores Extend the vertebral column; rotates it to the opposite side.
Interspinales Extend the vertebral column
Scalenes Flex and rotate the neck; assist in inspiration
Intertransversaril Abduct the vertebral column
Splenius capitis cervicis Acting together they extend the head and the neck; acting singly, they abduct and rotes the head towards the same side
Muscle Action
Erector spinae
Iliocostalis lumborum thoracis cervicis
Extend the vertebral column and bend it to one side
Longisimus thoracis cervicis capitis
Extend the vertebral column and the head; rotate the head to the same side
Spinalis thoracis cervicis Extend the vertebral column
Deep Muscles of the Thorax
Respiratory Muscles
Muscle Action
Diaphragm Pulls central tendon downwards, increasing the size of the thoracic cavity and therefore causing inspiration.
External intercostals Elevates the ribs, aids in inspiration
Internal intercostals Draws ribs together, aiding in expiration
Subcostals Draws ribs together, aiding in expiration
Transversus thoracis Draws the anterior portion of the rib cage downward, aids in expiration
Muscles of the Abdominal Wall
Muscle Action
External oblique abdominis Compresses the abdominopelvic cavity, assists in flexing and rotating the vertebral column.
Internal oblique abdominis Compresses the abdominopelvic cavity, assists in flexing and rotating the vertebral column.
Transversus abdominis Compresses the abdominopelvic cavity
Rectus abdominis Compresses the abdominopelvic cavity, flexes the vertebral column
Quadratus lumborum Pulls the thoracic cage towards the pelvis; abducts the vertebral column downward towards the side to which it is being contracted
Muscles that Form the Floor of the
Abdominopelvic Cavity
Muscle Action
Pelvic diaphragm
Levator ani Supports the pelvic viscera
Coccygeus Supports the pelvic viscera
Muscles that Act on the Scapula
Muscle Action
Trapezius Elevates, depresses, rotates, adducts, and stabilizes the scapula.
Rhomboideus major Adducts, rotates,and stabilizes the scapula, lowering its lateral angle.
Rhomboideus minor Adducts, rotates,and stabilizes the scapula, lowering its lateral angle.
Levator scapulae Elevates the scapula and bends the neck laterally when the scapula is fixed.
Pectoralis minor Draws the scapula anteriorly and downward,lowering its lateral angle.
Serratus anterior Stabilizes, abducts and rotates the scapula upward.
Subclavius Stabilizes the pectoral girdle and depresses it.
Muscles that Act on the Arm
Flexion Extension
Adduction
Abduction
Medial rotation
Lateral rotation
Deltoid Deltoid Pectoralis major
Deltoid Pectoralis major
Deltoid
Pectoralis major
Latissimus dorsi
Teres major
Supraspinatus
Latissimus dorsi
Supraspinatus
Coracobrachialis
Teres major
Coracobrachialis
Subscapularis
Infraspinatus
Infraspinatus
Deltoid Teres minor
Teres major
LET US IDENTIFY THESE MUSCLES!!
Got to study really hard now!
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