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Brief file of muscles of Head and Trunk
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1MUSCLES OF THE HEAD AND THE TRUNK
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Two headed-muscle, the key muscular landmark in neck Superior attachment: mastoid process of temporal bone and
superior nuchal line of occipital bone Inferior attachment:
sternal head: anterior surface of manubrium of sternum Clavicular head: superior surface of medial third of clavicle
Sternocleidomastoid (SCM)
Main action: Acting unilaterally, laterally flexes and
rotates the head and neck so the ear approaches the shoulder of the same side
Acting bilaterally, flex the neck
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DEEP OR INTRINSIC BACK MUSCLES
extend from the pelvis to the skull specifically act on the vertebral
column, maintain posture and produce movements of vertebral column
enclosed by fascia Innervated by posterior rami of
spinal nerves
Common points
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thoracolumbar fascia is an extensive fascial sheet that splits into anterior and posterior layers, enclosing the deep back muscles.
5Superficial layer - Splenius Muscles
Cover and hold the deep vertical muscles in position Origin: arises from nuchal ligament and
spinous processes of C7 T3 or T4 vertebrae Insertion:
Splenius capitis: mastoid process of temporal bone and lateral third of superior nuchal line of occipital bone
Splenius cervicis: transverse process of C1 C3 or C4 vertebrae
Main action: acting alone, laterally flex and rotate head
to the side of active muscles acting together, extend head and neck
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Intermediate layer - Erector Spinae(Sacrospinalis)
the chief extensor of vertebral column, divides into three columns Iliocostalis: Lateral column Longissimus: Intermediate column Spinalis: Medial column Each column is divided regionally into
cervicis, thoracis, lumborum according to its superior attachment
Common origin: arises by a broad tendon from posterior part of iliac crest, posterior surface of sacrum, sacral and inferior lumbar spinous processes, and supro-iliac ligament Iliac crest
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Insertion: Iliocostalis: fibers run superiorly to ribs and cervical
transverse processes
Intermediate layer - Erector Spinae(Sacrospinalis)
Spinalis: to spinous processes in the upper thoracic region and to skull
Longissimus: to ribs between tubercles and angles, to transverse processes in thoracic and cervical regions, and to mastoid process of temporal bone
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Main action: powerful trunk extensor acting bilaterally, they extend vertebral column
and head, as back is flexed they control movement by gradually lengthening their fibers
Acting unilaterally, they laterally flex vertebral column
Intermediate layer - Erector Spinae(Sacrospinalis)
9 Three muscles Semispinalis superficial Multifidus deeper Rotatores deepest
Common feature: they originate from transverse
processes of vertebrae to spinous processes of more superior vertebrae.
They occupy the space between transverse and spinous processes
Deep Layer Transversospinal Muscle Group
Transverse section of back10
Semispinalis
Origin: arises from transverse processes of C4 T12 vertebrae
Insertion:fibers run superomedially to occipital bone and spinous processes in thoracic and cervical regions, spanning 4 6 segments
Main action:extend head and thoracic and cervical regions of vertebral column and rotate them contralaterally
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Origin: arises from posterior aspects of sacrum and ilium, transverse processes of thoracic and lumbar vertebrae, and articular processes of the C4 - C7
Insertion:fibers pass superomedially to entire length of spinous processes of vertebrae above, spanning 2 - 4 segments
Main action: stabilizes vertebrae during local
movements of vertebral column Unilateral contraction rotates to
contralateral side
Multifidus
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Origin: transverse processes of vertebrae
Insertion: pass superomedially to attach to the root of the spinous processes of the next one or two vertebrae superiorly, spanning 1 - 2 segments
Main action: as proprieception organs stabilize vertebrae and assists with
local extension and rotary movements of vertebral column
Rotatores
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Minor Deep Layer
interspinal muscles connect spinous processes. They aid in extension and rotation
intertransverse muscles connect transverse processes. They aid in lateral flexion, and stabilize vertebral column when acting bilaterally
Levatores costarum elevate ribs, assisting inspiration and lateral flexion of vertebral column
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occupy the intercostal spaces Superior layer: external intercostal Middle layer: internal intercostal Deepest layer: innermost intercostal
Superior attachment: inferior border of ribs Inferior attachment: superior border of ribs below
MUSCLES IN THORACIC WALL: Intercostal Muscles
Main action Elevate ribs: external intercostal
and probably innermost intercostal
depress ribs: internal intercostal
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The muscle fibers run from inferior border of ribs to superior border of ribs below
External intercostal are continuous inferiorly with the external oblique muscles in the anterolateral abdominal wall
Internal intercostal run deep to and at right angles to the external intercostal and continuous with the internal oblique muscles in the anterolateral abdominal wall
External and Internal Intercostal Muscles
Action: External intercostal
inspiration, elevate ribs Internal intercostal
expiration, depress ribs
Internal intercostal
external intercostal
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Similar to the internal intercostal in fibers running direction and are deep parts of them
The innermost intercostal muscles are separated from the internal intercostal by the intercostal nerves and vessels
Innermost Intercostal Muscles
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MUSCLES OF ABODOMINAL WALL ANTERIOLATERAL WALL
Three flat muscles, external oblique, internal oblique, and transverse abdominal
Linea alba
All three flat muscles end anteriorly in strong aponeurosis. The aponeuroses of these muscles interlace at the linea alba
Linea alba (white line) is the fibrous band running vertically from the pubic symphysis to the xiphoid process and is the central attachment for all the abdominal muscles
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External & Internal Oblique Muscle
Internal Oblique The intermediate muscle Origin: thoracolumbar
fascia, anterior two-thirds of iliac crest and lateral half of inquinal ligament
Insertion: The fibbers fan out anteromedially and insert to inferior borders of 10th 12th ribs, lineaalba, and pubis via conjoint tendon
Eternal Oblique The largest and most
superficial muscle Origin: external
surfaces of 5th-12th ribs Insertion: linea alba,
pubic tubercle, and anterior half of iliac crest
Common actions: compress and support abdominal viscera, flex and rotates trunk
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Transverse Abdominal Muscle
The innermost of the three flat abdominal muscles
Origin: internal surfaces of 7th 12thcostal cartilages, thoracolumbar fascia, iliac crest, and lateral third of inquinal ligament
Insertion: linea alba with aponeurosis of internal oblique, superior ramus of pubis
Main action: Compress and support abdominal viscera
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Two vertical muscles, rectus abdominisand pyramidalis
All two vertical muscles are within the rectus sheath that is the strong, incomplete fibrous compartment of the two vertical muscle. It is formed by the decussation and interweaving of the aponeuroses of the flat abdominal muscles
The rectus muscle is anchored by attachment to rectus sheath at tendinous intersections
MUSCLES OF ABODOMINAL WALL ANTERIOLATERAL WALL
Tendinous intersection
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Rectus Abdominis Muscle
Origin: pubic symphysis and pubic crest
Insertion: Xiphoid process and 5th 7th costal cartilages
Most of the rectus abdominis is enclosed in the rectus sheath. Tendinous intersections (3 or more) anchor the rectus abdominis transversely
Main action: flexes trunk (lumbar vertebrae), compresses abdominal viscera, and stabilizes and controls tilt of pelvis
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Functions and actions of the anterolateral abdominal muscles
Form a strong expendable support for the anterolateral abdominal wall
Protect the abdominal viscera from injury Compress the abdominal contents Help to maintain or increase the intra-abdominal
pressure, assisting expiration and producing the force required for defecation, micturition (urination), and parturition
Move the trunk. Flex vertebral column, bend vertebral column laterally, rotate vertebral column, and help to maintain posture
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MUSCLES OF ABODOMINAL WALL POSTERIOR WALL -Quadratus lumborum,)
Pubic crest
Origin: medial half of inferior border of 12th rib and tips of lumbar transverse processes
Insertion: Iliolumbar ligament and iliac crest
Main action: extends and laterally flexes vertebral column; fixes 12th rib during respiration
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Diaphragm
A dome-shaped musculotendinous partition separates the thoracic and abdominal cavities the chief muscle of inspiration It is divided into three parts based on peripheral
attachment, a sternal part, a costal part, and a lumbar part.
Principle Muscles Producing Movement of Cervical Intervertebral joints
Neck flexion Sternocleidomastoid
Neck extension Splenius Semispinalis capitis
and cervicis Multifidus Longissimus capitis trapezius
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Lateral bending Iliocostalis cervicis Longiddimud csapitisand cervicis Splenius Intertraseversarii
Rotation Rotatores Multifidus Semispinalis capitis and cervicis Erector spinae Splenius cervicis sternocleidomastoid
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Reading materials
Moore, KL, Essential Clinical Anatomy (5th ed.)
Neck muscles: p. 585-586 Back muscles: p. 295-303 Muscles of thoracic wall,
p.56-57 Muscles of abdomen: p.113-
115, p, 179, p, 184-185
Moore, KL, Essential Clinical Anatomy (4th ed.)
Neck muscles: p. 596-599 Back muscles: p. 301-310 Muscles of thoracic wall,
p.60-61 Muscles of abdomen: p.118-
122
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Questions
1. Use the following terms to describe the actions and locations of back and abdominal muscles: origin, insertion, agonist and antagonist.
2. Use the following terms to describe the action of head, back and abdominal muscles: flexor, extensor, lateral flexor, and rotator.
3. Describe the locations and actions of the thoracic muscles.
4. Describe the locations and actions of neck muscles.5. Describe linea alba and rectus sheath.