9
9
9
9
9
9
10
10
10
10
10
10
11
13
18
27
28
29
3
4
5
6
7
8
9
9
9
9
9
9
9
10
10
10
10
10
10
11
13
18
27
28
29
164
Dissection of lower deep intersegmental muscles on left
Posterolateral view
Intersegmental Muscles The intertransversarii muscles are a mixed group that
are technically misnamed. The epaxial intertransverse
muscles (present at cervical, thoracic, and lumbar
levels) are the “true intertransverse” muscles. They attach to the transverse elements of the vertebral arch. The hypaxial
intertransverse muscles should be named intercostal muscles. They are only present in the cervical and lumbar regions and
attach to the costal processes (ribs) of the cervical and lumbar vertebrae, which are unfortunately named transverse processes even though they are not homologous with the thoracic transverse processes. These cervical and lumbar transverse
processes are homologous with the thoracic ribs. There are no thoracic hypaxial intertransverse muscles because they are
already present as the intercostal muscles and in this region they are properly named.
Rotatores and Intersegemental Muscles
1 Rotatores thoracis muscle
2 Rotatores lumborum muscle
3 Levatores costarum muscle
4 Interspinales thoracis muscle
5 Interspinales lumborum muscle
6 Thoracic intertransversarii muscle
7 Medial lumbar intertransversarii muscle
Other Muscles and Structures
8 Intertransversarii laterales
lumborum muscle - dorsal part
9 Intertransversarii laterales
lumborum muscle - ventral part
10 Internal intercostal muscle
11 Quadratus lumborum muscle
12 Iliocostalis muscle (cut)
13 Multifidus muscle (cut)
14 Trapezius muscle
15 Latissimus dorsi muscle
16 Rib 12
17 Iliac crest
18 Thoracolumbar fascia
19 Supraspinous ligament
1
1
1
1
1
1
2
2
2
3
3
3
3
3
4
5
6
7
7
7
8
8
8
9
9
9
10
10
11
12 13
14
15
16
17
18
19
6
1
1
1
1
1
1
2
2
2
3
3
3
3
3
6
7
7
7
8
8
8
9
9
9
10
10
11
12 13
14
15
16
17
6
165
trunk, a repeating segmental pattern emerges. This common muscle pattern is present in the anterior and lateral muscles
of the neck, the thorax, the abdomen, and in a modifi ed form in the wall and fl oor of the pelvis. Each hypomere contributes
six basic muscles, per side, to the trunk wall. The six muscles are a ventral muscle, a series of four superfi cial to deep lateral
muscles, and a subvertebral muscle. This simple, eloquent design runs the entire length of the trunk. Understanding and
recognizing this pattern of design not only clarifi es trunk wall anatomy, but also helps simplify the task of learning the myriad
of hypaxial trunk muscles. These hypaxial trunk muscles are the fl exors and rotators of the vertebral column. They also support
the internal viscera of the abdomen and thorax and play important roles in respiration, vocalization, urination, and defecation.
The ventral (anterior) ramus of each spinal nerve supplies all of the hypaxial muscles. The hypaxial muscle pattern and the
muscles that form the pattern are summarized below. On the next two pages the pattern is clearly demonstrated.
Hypaxial Muscles The hypaxial muscles develop from the hypomere of each somite’s
myotome and form the lateral and ventral muscle wall of the trunk. As
the hypomeres migrate to form the ventrolateral muscle wall of the
Hypaxial Muscle Pattern
Ventral musculature
Four-layered lateral musculature
Supracostal or outermost muscle layer
External muscle layer
Middle muscle layer
Internal muscle layer
Subvertebral musculature
Lumbar Hypaxial Muscles
Ventral musculature
Rectus abdominis muscle
Pyramidalis muscle
Four-layered lateral musculature
Supracostal layer
External oblique muscle - superficial lamina
External layer
External oblique muscle - deep lamina
Middle layer
Internal oblique muscle
Cremaster muscle
Intertransversarii laterales lumborum muscle - dorsal part
Internal layer
Transversus abdominis muscle
Quadratus lumborum muscle
Intertransversarii laterales lumborum muscle - ventral part
Subvertebral musculature
Psoas major muscle (annexed by the limb)
Psoas minor muscle
Pelvis/Perineal Hypaxial Muscles
Ventral musculature
Not present as it terminates on the pubic crest
Four-layered lateral musculature
Supracostal layer
Not present
External layer
Obturator externus muscle (annexed by the limb)
Bulbospongiosus muscle
Ischiocavernosus muscle
Superficial transverse perinei muscle
Superficial external anal sphincter
Middle layer
Obturator internus muscle (annexed by the limb)
Deep transverse perinei - male
Compressor urethrae - female
Sphincter urethrovaginalis -female
External urethral sphincter
Deep external anal sphincter
Internal layer
Levator ani muscle
Ischiococcygeus muscle
Subvertebral musculature
Not present as psoas is annexed by the limb
Cervical Hypaxial Muscles
Ventral musculature
Geniohyoid muscle
Thyrohyoid muscle
Superior omohyoid muscle
Inferior omohyoid muscle
Sternothyroid muscle
Sternohyoid muscle
Four-layered lateral musculature
Supracostal layer
Levator scapulae muscle
External layer
Posterior scalene muscle
Middle layer
Middle scalene muscle
Lateral posterior cervical intertransversarii muscle
Internal layer
Anterior scalene muscle
Anterior cervical intertransversarii muscle
Subvertebral musculature
Longus capitis muscle
Longus colli muscle
Thoracic Hypaxial Muscles
Ventral musculature
Sternalis muscle (present in about 10% of people)
Four-layered lateral musculature
Supracostal layer
Serratus posterior superior muscle
Serratus posterior inferior muscle
Rhomboideus major muscle (annexed by the limb)
Rhomboideus minor muscle (annexed by the limb)
Serratus anterior muscle (annexed by the limb)
External layer
External intercostal muscle
Middle layer
Internal intercostal muscle
Internal layer
Innermost intercostal muscle
Subcostal muscle
Transversus thoracis muscle
Diaphragm
Subvertebral musculature
Longus capitis muscle
166
The dissection photos on this and the facing page
clearly depict the pattern of design that arises from
the hypomere migration in the trunk wall. Note that
Hypaxial Muscle Pattern
both the ventral and subvertebral muscles are reduced in the thorax because the sturdy thoracic cage leads to a lack of
mobility in the thoracic vertebral column. Also, note that the lateral supracostal muscles of the neck and thorax are annexed
by the pectoral girdle to support the unattached upper limb. The clear relationship of the serratus anterior and its abdominal
homologue – the superfi cial lamina of the external oblique muscle – is also evident, as well as the continuity of the deep
lamina of the external oblique and its homologue, the external intercostal muscle. Finally, note how the subvertebral psoas
major is annexed away from the sacrum and onto the lower limb.
Ventral hypaxial muscles
Anterior view
Lateral supracostal hypaxial muscles
Lateral view
Lateral external hypaxial muscles
Lateral view
1
2
3
4
5
6
7
8
9
10
11
12
1
2
3
4
5
6
7
8
9
10
11
12
167
Lateral middle hypaxial muscles
Lateral view
Lateral internal hypaxial muscles
Lateral view
Subvertebral hypaxial muscles
Lateral view
Ventral Musculature
1 Sternohyoid muscle
2 Sternothyroid muscle
3 Thyrohyoid muscle
4 Omohyoid muscle
5 Rectus abdominis muscle
Lateral Supracostal Musculature
6 Levator scapulae muscle
7 Serratus anterior muscle
8 Serratus posterior inferior muscle
9 External oblique muscle (superficial lamina)
Lateral External Musculature
10 Posterior scalene muscle
11 External intercostal muscle
12 External oblique muscle (deep lamina)
Lateral Middle Musculature
13 Middle scalene muscle
14 Internal intercostal muscle
15 Internal oblique muscle
Lateral Internal Musculature
16 Anterior scalene muscle
17 Innermost intercostal muscle
18 Transversus abdominis muscle
Subvertebral Musculature
19 Longus capitis muscle
20 Longus colli muscle
21 Psoas major muscle
22 Psoas minor muscle
13 16
14
15
17
18
19
20
21
22
13 16
14
15
17
18
19
20
21
22
168
The muscular wall of the neck arises from the
hypomeres of the cervical somites and develops in accordance with the anterior and lateral
Cervical Hypaxial Muscles
body wall muscle pattern. A close scrutiny of the cervical hypaxial muscles reveals a ventral muscle, which has split into
numerous subdivisions, a four-layered lateral muscle wall where the muscles have lost their sheet-like structure, and a
subvertebral muscle on the anterior surface of the neck vertebrae. The cervical trunk muscles have a variety of functions.
Some of the muscles function to stabilize and move the cervical vertebral column. Some of the muscles assist in raising the
upper ribs. Some are annexed by the upper limb to support the pectoral girdle. The strap-like ventral muscles, which run
from sternum to larynx to hyoid bone to mandible, are active during mastication, swallowing, respiration, and sound production. These seemingly varied muscles are all innervated by the anterior rami of the cervical spinal nerves.
Dissection of neck muscles
Anterior view
Cervical Hypaxial Muscles
1 Sternohyoid muscle
2 Sternothyroid muscle
3 Thyrohyiod muscle
4 Omohyoid muscle
5 Geniohyoid muscle
6 Anterior scalene muscle
7 Middle scalene muscle
8 Posterior scalene muscle
9 Levator scapulae muscle
10 Longus colli muscle
Other Muscles and Structures
11 Anterior digastricus muscle
12 Mylohyoid muscle
13 Sternocleidomastoid muscle
14 Trapezius muscle
15 Deltoid muscle
16 Pectoralis major muscle
17 Serratus anterior muscle
18 Cricothyroid muscle
19 Stylohyoid muscle
20 Posterior digastricus muscle
21 Subclavian artery
22 Root of brachial plexus
23 Common carotid artery
24 Vagus nerve
25 Thyroid cartilage
26 Thyroid gland
27 Trachea
28 External intercostal muscle
29 Internal intercostal muscle
1
2
3
4
6
7
10
11 12
13
14
16
18
19
20
21
22
23
24
25
26
27
1
2
3
4
6
7
10
11 12
13
14
16
18
19
20
21
22
23
24
25
26
169
Dissection of cervical hypaxial muscles
Anterior view
Dissection of cervical hypaxial muscles
Anterolateral view
1
2
2
2
3
3
4
5
6
6
7
7
8
8
9
10
12 11
13
13
14
14
15
16
15
16
17
18
19
21
22
22
23
26
28
29
1
2
2
2
3
3
4
5
6
6
7
7
8
8
9
10
12 11
13
13
No comments:
Post a Comment
اكتب تعليق حول الموضوع