Soundarya VI BDS

2009-2010

The muscles of the neck can be grouped into the following 4 layers :

Trapezius and latissiumus dorsi .

Levator scapulae, rhomboideus, serratus posterior superior, serratus posterior inferior and splenius.

Erector spinae.

The first layer consists of Trapezius and latissiumus dorsi .

The second layer comprises of splenius muscle, Levator scapulae , rhomboideus major and minor, serratus posterior superior and serratus posterior inferior muscle .

Third layer comprises of erector spinae . Fourth layer are Multifidus , rotatores,

interspinales , intertransversii and sub occipital muscles.

The muscles of the back will be divided into 3 main groups :

superficial muscles associated with the shoulder girdle.

the intermediate muscles involved with respiration.

The deep muscles belonging to the vertebral column.

SKIN : SENSORY NERVE SUPPLY the skin of the back is supplied by the

posterior rami of the spinal nerves.BLOOD SUPPLY :In the cervical region

branches from occipital, vertebral, deep cervical and ascending cervical arteries supply. In the thoracic region are the posterior intercostal arteries and in the lumbar region are lumbar and subcostal arteries.

Venous drainage The veins form complicated plexuses

extending along the vertebral column from the skull to the coccyx.

Veins lying external to vertebral column form the EXTERNAL VERTEBRAL VENOUS PLEXUS

Within the vertebral canal form the INTERNAL VERTEBRAL VENOUS PLEXUS.

Tributaries from the vertebrae form BASIVERTEBRAL VEINS drain into the internal V V PLEXUS.

INTERVERTEBRAL VEINS drain the internal plexus

Venous drainage (continued) Veins communicate freely with venous

sinuses above through Foramen magnum and with veins in the neck, thorax, abdomen and pelvis.

Finally tributaries from external plexus join and drain via the vertebral, intercostal, lumbar, and lateral sacral veins.

All these veins are thin walled, valveless or have incompetent valves.

Venous flow is free and direction of flow depends on the pressure difference between regions.

It is a large, flat, triangular muscle that extends over the back of the neck and thorax.

ORIGIN : from the medial third of the superior nuchal line of the occipital bone, the external occipital protuberance, ligamentum nuchae ; from the spine of the seventh cervical vertebra and the spines and the supraspinous ligaments of all the thoracic vertebrae.

INSERTION : The upper fibers are directed downward and laterally into the lateral third of the clavicle ;

Middle fibers are directed horizontally into the acromion and the upper border of the spine of the scapula ;

The lowest fibers are directed upwards and laterally and are inserted on the medial end of the spine of the scapula .

NERVE SUPPLY : Motor fibers from the spinal part of the XI cranial nerve ( accessory nerve) .

Sensory fibers from the cervical nerves.(C3 and C4)

ACTION :Suspends the shoulder from the skull and

the vertebral column .Upper fibers

ACTION :

Suspends the shoulder from the skull and the vertebral column .

Upper fibers elevate the scapula. Middle fibers pull the scapula

medially . Lower fibers pull the medial border of

the scapula downward .

It is a large , flat , triangular muscle that extends over the lumbar region and the lower part of the thorax.

ORIGIN : From the posterior part of the iliac crest , the lumbar fascia and the spines of the lower six thoracic vertebrae, from the lower three or four ribs and sometimes by a few fibers from the inferior angle of the scapula.

INSERTION : Its tendon wraps around the lower border of the Teres major muscle and is inserted into the floor of the bicipital groove of the humerus.

NERVE SUPPLY : The thoracodorsal nerve , a branch of the posterior cord of the brachial plexus .

ACTION : It extends , adducts and medially rotates the arm.

MUSCLE ORIGIN INSERTION NERVE SUPPLY

ACTION

Levator scapulae

Rhomboid minor

Transverse process of upper cervical vertebrae .

Lower part of ligamentum nuchae .

Medial border of the scapulae .

Medial border of scapula opposite to the spine.

Third and fourth cervical nerves.

C5

Raises the scapulae upwards and braces the shoulder backwards.

Pulls the scapula medially

MUSCLES OF THE SECOND LAYER

MUSCLE ORIGIN INSERTION NERVE SUPPLY

ACTION

Rhomboid Major

Second to fifth thoracic spines

Medial border of scapula opposite to the infraspinous fossa

C5 Pulls the scapula medially

Erector spinae is the true muscle of the back.

It is supplied by the posterior rami of the spinal nerves .

ORIGIN : back of the sacrum between the medial and lateral sacral crests from the dorsal segment of the iliac crest.

It splits into 3 columns .

Iliocostalis in the lateral column . Longissimus in the middle column. Spinalis in the medial column.

Multifidus, rotatores, interspinales and sub occipital muscles.

Arise from the mamillary processes of lumbar vertebrae to be inserted into 2-3 spinous processes .

Rotatores are the deepest group .

They are well developed in the thoracic region.