HUMAN ANATOMY – VOLUME 1

The splenius capitis muscle (m. splénius cáapitis) is situated in front of the upper parts of the sternocleidomastoid and trapezius muscles. It begins on the spinous processes of the C7 and the upper 3–4 thoracic vertebrae. It stretches laterally upwards and attaches to the mastoid process of the temporal bone.

F u n c t i o n: One-sided contraction turns the head to the corresponding side; contraction on both sides straightens the cervical part of the vertebral column.

I n n e r v a t i o n: posterior branches of the cervical spinal nerves. B l o o d s u p p l y: deep cervical artery, occipital artery.

The splenius cervicis muscle (m. splénius cérvicis) is situated to the front of the trapezius muscle. It begins on the spinous processes of the T3 andT4 vertebrae and attaches to the posterior tubercles of the transverse processes of 2–3 upper cervical vertebrae.

F u n c t i o n: During one-sided contraction the cervical part of the spine turns to the corresponding side; contraction of the muscle on both sides causes the cervical part of the spine to straighten.

I n n e r v a t i o n: posterior branches of the cervical spinal nerves. B l o o d s u p p l y: deep cervical artery, occipital artery.

The erector spinae muscle (m. eréctor spínae) is situated along the entire length of the spine. It is situated to the front of the trapezius, rhomboid, posterior occipital and the latissimus dorsi muscles. It is covered in the back by the superficial sheet of the thoracolumbar fascia. The muscle begins on the dorsal surface of the sacrum, spinous processes of all lumbar and 2 lower thoracic vertebrae, the iliac crest (its dorsal part), the thoracolumbar fascia, and the sacrospinous and sacrotuberal ligaments. The erector spinae muscle is divided into three parts: lateral (the iliocostalis muscle), intermediate (the longissimus muscle), and medial (the spinalis muscle). Each of these muscles is subdivided into three parts.

The iliocostalis muscle (m. iliocostális) is the most lateral part of the erector spinae muscle. It is divided into the iliocostalis lumborum, thoracis and cervicis muscles, depending on what region they are in. The iliocostalis lumborum muscle originates on the iliac crest and the superficial lamina of the thoracolumbar fascia, and is inserted into the angles of lower 6 ribs. The iliocostalis thoracis muscle originates on the 6 lower ribs, medially of the insertion of the iliocostalis lumborum muscle. It attaches to the angles of the upper 6 ribs and the posterior surface of the transverse process of C7 vertebra. The iliocostalis cervicis muscle originates on the angles of ribs 3–4, medially of the insertion of the iliocostal thoracis muscle. It inserts into the posterior tubercles of transverse processes of C3 and C4 vertebrae.

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F u n c t i o n: This muscle straightens the vertebral column by contracting on both sides. During one-sided contraction it bends the vertebral column to the corresponding side. It also lowers the ribs.

The longissimus muscle (m. longíssimus) is situated more medially from the iliocostalis muscle. It is divided into three parts: the longissimus thoracis, longissimus cervicis and longissimus dorsi.

The longissimus thoracis muscle originates on the dorsal surface of the sacrum and the transverse processes of the lumbar and lower thoracic vertebrae. It inserts on the dorsal surface of the lower 9 ribs, between their tubercles and angles. The longissimus cervicis muscle begins on the apexes of transverse processes of 5 upper thoracic vertebrae. It attaches on the posterior tubercles of transverse processes of C2–C6 vertebrae. The longissimus capitis muscle originates on the transverse processes of the T1– T3 and C3–C7 vertebrae. It is inserted into the back of the mastoid process of the temporal bone.

F u n c t i o n: During contraction on both sides the longissimus thoracis and cervicis muscles straighten the vertebral column; during one-sid- ed contraction they promote the inclination of the spine to the corresponding side. The longissimus cervicis muscle bends the head backwards.

The spinalis muscle (m. spinális) is situated medially of the longissimus muscle, adjoining the spinous processes of thoracic and cervical vertebrae. It is divided into the spinalis thoracis, spinalis cervicis and spinalis capitis muscles. The spinalis thoracis muscle originates from the spinous processes of L1–L2 and T11–T12 vertebrae. It inserts into the spinous processes of the T1–T8 vertebrae. The spinalis cervicis muscle stretches between the spinous processes of T1 and T2 vertebrae to the spinous process of the C2 vertebra (sometimes also C3 andC4). The spinalis capitis muscle originates from the spinous processes of the upper thoracic and the lower cervical vertebrae, and attaches to the external occipital protuberance (this muscle is often absent).

F u n c t i o n: The spinal muscles straighten the vertebral column. The function of the entire erector spinae muscle consists of straight-

ening the vertebral column and head. The muscle is antagonist of the anterior muscles of the body. During its one-sided contraction the vertebral column bends to the corresponding side. The muscle plays an important role in performing yielding work during the bending of the body forward, preventing it from falling.

I n n e r v a t i o n: posterior branches of the cervical, thoracic and lumbar spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal arteries, lumbar arteries.

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The transversospinales muscle (m. transversospináles) consists of many muscle fibers of different lengths, obliquely oriented and situated in layers. The muscle consists of different parts, which differ in length of muscle fibers. They are called the semispinal, multifidus and rotator muscles.

The semispinalis muscle (m. semispinális) consists of long muscle fascicles, which originate from the transverse processes of vertebrae, stretch upward and medially, span 4–6 vertebrae and attach to the spinous processes. The semispinalis muscle has a thorax, neck and head sections. The semispinalis thoracis and cervicis muscles originate from the transverse processes of all thoracic vertebrae and are inserted on the spinous processes of T1–T6 and C2–C7 vertebrae.

The semispinalis capitis muscle of the head originates on the transverse processes of T1–T4 and C4–C7 vertebrae, and inserts in the occipital bone (between the superior and inferior nuchal lines).

F u n c t i o n: Contraction of semispinales muscles on both sides causes the thoracic and cervical parts of the spine and the head to straighten. During one-sided contraction they turn the neck and the head toward the opposite side.

I n n e r v a t i o n: posterior branches of cervical and thoracic spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal arteries.

The multifidus muscles (mm. multífídi) originate from the dorsal surface of the sacrum and on transverse processes of all vertebrae up to C2. They stretch upward and medially, span 2–4 vertebrae and insert into spinous processes.

F u n c t i o n: These muscles turn the vertebral column about the vertical axis, toward the opposite side.

I n n e r v a t i o n: posterior branches of the spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal and lumbar arteries.

The rotatores muscles (mm. rotátores) form the deepest layer of muscles of the back. They are best expressed in the thoracic section of the spine. These muscles originate from transverse processes and stretch upward and medially. They insert into the base of the next or second to next vertebra above.

F u n c t i o n: They turn the vertebral column about the vertical axis to the opposite side.

I n n e r v a t i o n: posterior branches of the spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal and lumbar arteries.

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The intertransversarii muscles (mm. inertransversárii) are short muscle fascicles, which stretch between transverse processes of adjacent vertebrae. They are not well expressed in the thoracic part of the spine.

F u n c t i o n: They bend the appropriate parts of the vertebral column to the corresponding side.

I n n e r v a t i o n: posterior branches of spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal and lumbar arteries.

The interspinales muscles (mm. interspináles) stretch between the spinuos processes of neighboring vertebrae. In the thoracic part of the spine these muscles are often absent or poorly expressed.

F u n c t i o n: They participate in straightening the vertebral column. I n n e r v a t i o n: posterior branches of spinal nerves.

B l o o d s u p p l y: deep cervical artery, posterior intercostal and lumbar arteries.

The suboccipital muscles (mm. suboccipitáles). There are four muscles included in this group. They are situated in the occipital region between the skull and the C1 and C2 vertebrae, to the front of the semispinalis and splenius capitis muscles (Fig. 94). These are the paired rectus capitis posterior major, rectus capitis posterior minor muscles, obliquus capitis superior muscle, obliquus capitis inferior muscles.

The rectus capitis posterior major (m. réctus cápitis postérior májor) originates on the spinous process of the C2 vertebra. It stretches upwards and to the laterally and inserts on the occipital bone, beneath the lower nuchal line.

F u n c t i o n: During two-sided contraction the muscle bends the head backwards; and during one-sided contraction it moves the head to its side.

I n n e r v a t i o n: suboccipital nerve.

B l o o d s u p p l y: deep cervical artery.

The rectus capitis posterior minor (m. réctus cápitis postérior minor) originates from the posterior tubercle of the atlas, passes upwards and inserts into the occipital bone below the nuchal line, deeper and more medially than the rectus capitis posterior major muscle.

F u n c t i o n: Straightening the head. I n n e r v a t i o n: suboccipital nerve.

B l o o d s u p p l y: deep cervical artery.

The obliquus capitis superior muscle (m. obliquus cápitis supérior) stretches from the transverse process of the atlas medially and upwards, and inserts into the occipital bone above the inferior nuchal line.

F u n c t i o n: During two-sided contraction the head extends backwards, and during one-sided contraction the head turns to the corresponding side.

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Fig. 94. Suboccipital and deep muscles of posterior aspect of neck.

1 — external occipital protuberance; 2 — rectus posterior capitis minor; 3 — posterior tubercle of atlas; 4 — oblique capitis inferior; 5 — spinous process of axis; 6 — obliquus capitis superior; 7 — rectus capitis posterior major.

I n n e r v a t i o n: suboccipital nerve.

B l o o d s u p p l y: deep cervical artery.

The obliquus capitis inferior muscle (m. oblíquus cápitis inférior) begins on the spinous process of the C2 vertebra and passes laterally and upwards to the transverse process of the atlas.

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F u n c t i o n: The head is turned to the opposite side. I n n e r v a t i o n: suboccipital nerve.

B l o o d s u p p l y: deep cervical artery.

Muscles of the back and suboccipital region are demonstrated in the table 8.

FASCIAE OF THE BACK

The superficial fascia of the back, which covers the trapezius and latissimus dorsi muscles, is not markedly developed. The thoracolumbar fascia (fáscia thoracolumbális), which covers the deep muscles of the back, is developed quite well, especially in the lumbar region, where it is divided into superficial and deep laminae. Its superficial lamina is attached medially to the apexes of spinous processes of all thoracic and lumbar vertebrae, to the middle sacral crest and, laterally, to the angles of ribs. The d e e p l a m i n a of this fascia medially attaches to the transverse processes of lumbar vertebrae, at the top — to the twelfth rib, and at the bottom — to the iliac crest. The two plates fuse together near the lateral edge of the erector muscle of the spine, forming a fascial sheath around this muscle.

On the dorsal region of the neck, between its muscles, are the laminae of the nuchal fascia (fáscia núchae).

TOPOGRAPHICANATOMYANDFATTYTISSUESPACESOFTHEBACK

The external occipital protuberance, the spinal processes of C2, C7 and all thoracic and lumbar vertebrae, and the middle sacral crest can all be palpated in a living person. The cervical and lumbar lordoses and the thoracic and sacral kyphoses are also easily detectable. Normally, on either side of the spine it is possible to palpate the lower and medial angles of the scapula, the scapular spine and the ribs. The erector muscles of spine can be seen along the sides the middle line. They are fused with the superficial fascia by fascicles of connective tissue. The skin of this region contains a lot of sweat and sebaceous glands. The subcutaneous fat is well developed, especially in women. It contains the posterior and lateral branches of intercostal and lumbar blood vessels, as well as nerves and their endings.

To the front of the fascial sheaths of the trapezius and latissimus dorsi muscles, which partially cover the scapula, there is a loose fatty tissue space that separates these muscles from the splenius muscles of the head and neck, the levator scapula, rhomboid and serratus muscles.

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Deep muscles of the back

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The upper border of the lumbar region can be palpated at the twelfth rib and the free ends of ribs 11 and 12. The lower border of the lumbar region passes along the iliac crest. The outer (lateral) border corresponds to the prolongation of the middle axillary line. Above the highest point of the iliac crest there is a palpable fossa, which corresponds to the lu m b a r t r i a n g l e. This is the weakest place of the lumbar region and often becomes an outlet of lumbar hernias. The borders of this triangle are: the iliac crest (at the bottom); the lateral edge of the latissimus dorsi muscle aponeurosis (medial); and the dorsal edge of the external abdominal oblique muscle (lateral). The floor of this triangle is formed by the internal abdominal oblique muscle.

Above the horizontal line that connects the iliac crests it is possible to palpate the spinous process of the L4 vertebra, which serves as orientation for defining the level of the other lumbar vertebrae.

The superficial fascia, which covers the trapezius muscle, is not welldeveloped. In the lumbar region, beneath this fascia, there is a lumbogluteal fatty tissue space, which covers the lower sections of the latissimus dorsi muscle.

The superficial and deep laminae of the thoracolumbar fascia are well developed in the lumbar region. The deep lamina is situated between the quadratus lumborum muscle and the erector muscle of the spine. The thick upper edge of the deep lamina, which is stretched between the transverse process of the L1 vertebra and the twelfth rib, is called the lumbocostal ligament. The tendon origin (aponeurosis) of the latissimus dorsi muscle is accreted with the superficial lamina of the thoracolumbar fascia.

In the occipital region there is the o c c i p i t a l t r i a n g l e, which is bordered by the major posterior rectus and the two oblique muscles. At the floor of this triangle, beneath the fascia and the fatty tissue is the posterior arch of the atlas. Between the arch and the occipital bone there is a thick posterior atlanto-occipital ligament.

Questions for revision and examination

1.What groups are the muscles of the back divided into according to their origin and

depth?

2.What parts is the erector muscle of the spine divided into?

3.Which muscles of the back lift the ribs, and which muscles lower them?

4.What actions does the suboccipital group of muscles perform?

5.Name the fasciae of the back and describe their anatomic and functional character-

istics.

MUSCLES AND FASCIAE OF THE THORAX

Muscles of the thorax are situated within the thorax region in several layers. Muscles of the superficial layer develop in association with the

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