The posterior triangle (or lateral cervical region) is a region of the
neck
The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...
.
Boundaries
The posterior triangle has the following boundaries:
Apex: Union of the
sternocleidomastoid
The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the acces ...
and the
trapezius
The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...
muscles at the
superior nuchal line
The nuchal lines are four curved lines on the external surface of the occipital bone:
* The upper, often faintly marked, is named the highest nuchal line, but is sometimes referred to as the Mempin line or linea suprema, and it attaches to the e ...
of the
occipital bone
The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...
Anteriorly: Posterior border of the
sternocleidomastoideus
Posteriorly: Anterior border of the
trapezius
The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...
Inferiorly: Middle one third of the
clavicle
The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately long that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body. The clavic ...
Roof: Investing layer of the
deep cervical fascia
The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its ...
Floor: (From superior to inferior)
1) M. semispinalis capitis
2) M. splenius capitis
3) M. levator scapulae
4) M. scalenus posterior
5) M. scalenus medius
Divisions
The posterior triangle is crossed, about 2.5 cm above the clavicle, by the inferior belly of the
omohyoid muscle, which divides the space into two triangles:
* an upper or
occipital triangle
* a lower or
subclavian triangle (or supraclavicular triangle)
Contents
A) Nerves and plexuses:
*
Spinal accessory nerve (Cranial Nerve XI)
* Branches of
cervical plexus
The cervical plexus is a nerve plexus of the anterior rami of the first (i.e. upper-most) four cervical spinal nerves C1-C4. The cervical plexus provides motor innervation to some muscles of the neck, and the diaphragm; it provides sensory inne ...
* Roots and trunks of
brachial plexus
The brachial plexus is a network of nerves (nerve plexus) formed by the anterior rami of the lower four Spinal nerve#Cervical nerves, cervical nerves and first Spinal nerve#Thoracic nerves, thoracic nerve (cervical spinal nerve 5, C5, Cervical spi ...
* Phrenic nerve (C3,4,5)
B) Vessels:
*
Subclavian artery (Third part)
*
Transverse cervical artery
*
Suprascapular artery
The suprascapular artery is a branch of the thyrocervical trunk on the neck.
Structure
At first, it passes downward and laterally across the scalenus anterior and phrenic nerve, being covered by the sternocleidomastoid muscle; it then crosses t ...
* Terminal part of
external jugular vein
C) Lymph nodes:
* Occipital
* Supraclavicular
D) Muscles:
* Inferior belly of
omohyoid muscle
*
Anterior Scalene
*
Middle Scalene
*
Posterior Scalene
*
Levator Scapulae Muscle
The levator scapulae is a slender skeletal muscle
Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous s ...
*
Splenius
Clinical significance
The accessory nerve (CN XI) is particularly vulnerable to damage during lymph node biopsy. Damage results in an inability to shrug the shoulders or raise the arm above the head, particularly due to compromised
trapezius muscle
The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...
innervation.
The
external jugular vein's superficial location within the posterior triangle also makes it vulnerable to injury.
See also
*
Anterior triangle of the neck
The anterior triangle is a region of the neck.
Structure
The triangle is inverted with its apex inferior to its base which is under the chin.
Investing fascia covers the roof of the triangle while visceral fascia covers the floor.
Anatomy
M ...
References
External links
* ()
*
* - "Identification of the muscles associated with the posterolateral triangle."
{{Authority control
Human head and neck
Triangles of the neck