The supratrochlear nerve is a branch of the frontal nerve

Frontal nerve

The frontal nerve is the largest branch of the ophthalmic nerve, and may be regarded, both from its size and direction, as the continuation of the nerve....

, which itself comes from the ophthalmic division of the trigeminal (or fifth) cranial nerve.
It is smaller than the nearby supraorbital nerve

Supraorbital nerve

The supraorbital nerve is a terminal branch of the frontal nerve.It passes through the supraorbital foramen, and gives off, in this situation, palpebral filaments to the upper eyelid...

. It passes above the pulley of the Superior oblique muscle, and gives off a descending filament that joins the infratrochlear branch of the nasociliary nerve

Nasociliary nerve

The nasociliary nerve is a branch of the ophthalmic nerve. It is intermediate in size between the two other main branches of the ophthalmic nerve, the frontal nerve and the lacrimal nerve, and is more deeply placed.-Path:...

.

The supratrochlear nerve then exits the orbit between the pulley of the superior oblique and the supraorbital foramen

Supraorbital foramen

The supraorbital foramen is a bony elongated path located above the orbit and under the forehead. The supraorbital foramen lies directly under the eyebrow....

, curves up on to the forehead close to the bone, and ascends beneath the Corrugator supercilii and Frontalis

Frontalis

Frontalis may refer to:* Crista frontalis, the frontal crest, a crest on the internal surface of the squama frontalis of the frontal bone* Frontalis muscle, a thin, quadrilateral fascia muscle located on the front of the head...

 muscles. It then divides into branches which pierce these muscles and supplies the following areas:

• skin of the lower part of the forehead
  Forehead
  For the Arsenal striker see GervinhoIn human anatomy, the forehead is the fore part of the head. It is, formally, an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp...
  
  , close to the midline
• conjunctiva
  Conjunctiva
  The conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...
  
  
• skin of the upper eyelid
  Eyelid
  An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...
  
  .

Etymology

Supratrochlear means "above the trochlea". The term trochlea means "pulley" in Latin. Specifically, the trochlea referred to is a loop inside the orbit of the eye, through which the tendon of the superior oblique muscle passes.

External links

• http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-2.HTM