Thoracic Nerves

AND Motor Cranial Nerve

student :: Zaeid .Alhamashi

The Thoracic Nerves :The anterior divisions of the thoracic nerves are twelve in number on either side. Eleven of them are situated between the ribs, and are therefore

termed intercostal; the 12th lies below the last rib

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•Each nerve is connected with the adjoining ganglion of the sympathetic trunk by a gray and a white ramus communicans

• The First Thoracic Nerve -the anterior division of the first thoracic nerve divides into two branches: one,the larger, leaves the thorax in front of the neck of the first rib, and enters the brachial plexus; the other and smaller branch, the first intercostal nerve, runs along the first intercostal space, and ends on the front of the chest as the first anterior cutaneous branch of the thorax.

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•The first two nerves supply fibers to the upper limb in addition to their thoracic branches;•The next four are limited in their distribution to the parietes of the thorax;

•The lower five supply the parietes of the thorax and abdomen.

•The twelfth thoracic is distributed to the abdominal wall and the skin of the buttock.

.•The Upper Thoracic Nerves ( intercostales)-The anterior divisions

of the 2nd , 3rd , 4th , 5th, and 6th thoracic

nerves, and the small branch from the

first thoracic, are confined to the parietes of the thorax, and are named thoracic intercostal nerves.

cont

•They pass forward in the intercostal spaces below the intercostal vessels.

•At the back of the chest they lie

between the pleura and the posterior

intercostal membranes,

.•Branches.—Numerous slender muscular filaments supply the Intercostales, the Subcostales, the Levatores costarum, the Serratus posterior superior, and the Transversus thoracis. At the front of the thorax some of these branches cross the costal cartilages from one intercostal space to another

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•Lateral cutaneous branches are derived from the

intercostal nerves, about midway

between the vertebræ and sternum; and divide into

anterior and posterior branches……

cont

The anterior branches run forward to the

side and the forepart of the chest,

supplying the skin,

The posterior branches run backward,

and supply the skin over the scapula

and Latissimus dorsi.

.•The Lower Thoracic Nerves.The anterior divisions of the 7th , 8th , 9th,

10th, and 11th thoracic nerves are continued anteriorly from the intercostal

spaces into the abdominal wall; hence they are named thoracicoabdominal intercostal nerves.

.• twelfth thoracic nerve is larger than the others; it runs along the lower border of the twelfth rib, often gives a communicating branch to the first lumbar nerve, It communicates with the iliohypogastric nerve of the lumbar plexus, and gives a branch to the Pyramidalis. The lateral cutaneous branch of the last thoracic nerve is large, and does not divide into an anterior and a posterior branch.

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Motor Cranial Nerve

.•The Oculomotory Nerve(III) supplies somatic motor fibers to all the ocular muscles, except the Obliquus superior and Rectus lateralis

.The fibers of the oculomotor nerve arise

from a nucleus which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the 3rd ventricle.

,

The nucleus of the oculomotor n, does not

consist of a continuous column of cells,

but is broken up into a number of smaller

nuclei, which are arranged in two groups,

anterior and posterior. the nerve is invested with

a sheath of pia mater, and enclosed in a prolongation from the arachnoid.

Oculomotory n. Enter to the orbital cavity through Superior orbital fissure

.It then divides into two branches, which

enter the orbit through the superior orbital fissure

The superior ramus, the smaller, passes

medialward over the optic nerve, and

supplies the Rectus superior and Levator

palpebræ superioris.

• The inferior ramus, thelarger, divides into three branches. One passes beneath the optic nerve to the Rectus medialis; another, to the Rectus inferior; the third and longest runs forward between the Recti inferior and lateralis to the Obliquus inferior.

.The Trochlear Nerve(IV) - the smallest of the

cranial nerves, It arises from a nucleus situated in the floor of the cerebral aqueduct, opposite the upper part of the inferior colliculus

It crosses the oculomotor nerve,

enters the orbit through the sup.

orbital fissure ,to supplies the Obliquus superior oculi

.The Abducent Nerve(VI) arise from a small nucleus situated in the upper part of the rhomboid fossa, close to the middle line

and beneath the

colliculus

facialis

.It Enters the orbit cavity through

the sup.

orbital fissure and it has only one branch to supply Rectus lateralis m.

.The Accessory Nerve (XI) consists of two parts: a

cranial and a spinal.

The Cranial Part;; is the smaller of the two. Its fibers arise from the cells of the nucleus ambiguus and emerge as four or five delicate rootlets from the side of the medulla oblongata,below the roots of the vagus. It runs lateralward to the jugular foramen, where it interchanges fibers with the spinal portion or becomes united to it for a short distance;

.•where it is also connected by one or two

filaments with the jugular ganglion of the vagus. It then passes through the jugular foramen, separates from the spinal portion and is continued over the surface of the ganglion nodosum of the vagus.Through the pharyngeal branch it probably supplies the Musculus uvulæ and Levator veli palatini.

.•The Spinal Part ;;its fibers arise from the

motor cells of the anterior column of the gray substance of the medulla spinalis as low as the 5th cervical nerve. Passing through the lateral funiculus of the medulla spinalis, they emerge on its surface and unite to form a single trunk,

.Enters the skull through the foramen magnum, and is then directed to the jugular foramen, through which it passes, lying in the same sheath of dura mater as the vagus, but separated from it by a fold of the arachnoid.

it unites with the 2nd and 3rd cervical nerves, while beneath the Trapezius it forms a plexus with the 3rd and 4th cervical nerves, and from this plexus fibers are distributed to the muscle.

.The Hypoglossal Nerve (XII)

• is the motor nerve of the tongue (All tongue muscles

•except palatoglossus) across through Foramen: Hypoglossal canal . Its fibers arise from the cells of the hypoglossal nucleus (anterior gray substance of the medulla spinalis) which is about 2 cm. in length, and its upper part corresponds with the trigonum hypoglossi, or lower portion of the medial eminence of the rhomboid

.• In the posterior triangle it unites with the

second and third cervical nerves, while beneath the Trapezius it forms a plexus with the third

and fourth cervical nerves, and from this plexus fibers are distributed to the muscle

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Summry cranial nerves

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