Nerves ensure that muscles are given instructions. Nerves are also needed to inform the brain about the (tension) state of the muscles. Passing on commands or signals is called innervation.
Nerve fibers can be divided into two types:
- Motion nerve fibers or motor nerve fibers. The motor nerve fibers send signals to muscles or organs that something must be done: a muscle must start working or a gland must produce saliva.
- Sensory nerve fibers or sensitive nerve fibers. These are the nerve fibers that send signals to the central nervous system. These signals make us aware of all sorts of things. For example, we can feel, see, smell and hear.
A mixed nerve contains both sensitive and motor nerve fibers. Traffic in two directions is therefore possible in a mixed nerve.
The motor innervation of the muscles and muscle groups in the head and neck area is done by brain nerves and / or spinal nerves.
Brain nerves are nerves that come directly from the brain. These brain nerves can be both motor and sensitive. The nerve bundles of the brain nerves leave the brain through holes in the skull base. The brain nerves are numbered from I to XII with Roman numerals: so twelve pairs of nerves come straight from the brain. Two pairs of these nerves are important in connection with the innervation of the nerves in the head and neck:
- The n. V or fifth cranial nerve, the trigeminal nerve, which branches into three branches, one of which is partially motorized. This branch is the mandibular nerve, or the n. V3.
- The n. VII or seventh cranial nerve, the facial nerve. The name of this nerve actually indicates what this nerve is for: think of the English “face”. This motor nerve therefore serves for the innervation of all mimic muscles.
All other specifically named muscles are also innervated by brain nerves.
The muscle (group) that are not specifically mentioned can be innervated by both brain and spinal nerves.
The table below indicates which muscle (group) and which nerve are injected (see figure below).
Overview of the motor innervation of the muscles in the head and neck area.
|M. Masseter||Motor branch of the n. V3 (mandibular nerve)|
|M. Temporalis||Motor branch of the n. V3 (mandibular nerve)|
|M. Pterygoideus lateralis||Motor branch of the n. V3 (mandibular nerve)|
|M. Pterygoideus medialis||Motor branch of the n. V3 (mandibular nerve)|
|Suprahyoidal muscles, tongue muscles||Cranial nerves|
|Intrinsic tongue muscles||Cranial nerves|
|Extrinsic tongue muscles||Cranial nerves|
|M. Buccinator||Nervus facialis|
|M. Orbicularis oris||Nervus facialis|
|Infrahyoidal muscles, neck and neck muscles||Brain nerves or spinal nerves|
|Muscles of the trunk||Spinal cord nerves|
|Muscles of the limbs||Spinal cord nerves|
The emotional nerve supply of the head is for the most part provided by branches of the fifth cranial nerve, denervus trigeminal. This nerve has three main branches, each of which provides a part of the sensory innervation:
- Nervus ophthalmicus (n. V1);
- Nervus maxillaris (n. V2);
- Nervus mandibularis (n. V3).
The maxillary nerve and mandibular nerve branch among other things into the teeth of the upper and lower jaw.
The sensory innervation of the back of the head is provided by spinal nerves from the cervical spine (see images below).