The occipital triangle, the larger division of the posterior triangle, is bounded, in front, by the Sternocleidomastoideus; behind, by the Trapezius; below, by the Omohyoideus.

Its floor is formed from above downward by the Splenius capitis, Levator scapulæ, and the Scaleni medius and posterior.

It is covered by the skin, the superficial and deep fasciæ, and by the Platysma below.

The accessory nerve

Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...

 is directed obliquely across the space from the Sternocleidomastoideus, which it pierces, to the under surface of the Trapezius; below, the supraclavicular nerves

Supraclavicular nerves

The supraclavicular nerves arise from the third and fourth cervical nerves; they emerge beneath the posterior border of the Sternocleidomastoideus, and descend in the posterior triangle of the neck beneath the platysma and deep cervical fascia.-Branches:Near the clavicle they perforate the fascia...

 and the transverse cervical vessels and the upper part of the brachial plexus

Brachial plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

 cross the space.

The roof of this triangle is formed by the cutaneous nerves of cervical plexus and the external jugular vein and platysma muscle

A chain of lymph glands is also found running along the posterior border of the Sternocleidomastoideus, from the mastoid process to the root of the neck

Neck

The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

.