The ansa cervicalis is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle, its name means "handle of the neck" in Latin. Branches from the ansa cervicalis innervate most of the infrahyoid muscles, including the sternothyroid muscle, sternohyoid muscle, the omohyoid muscle. Note that the thyrohyoid muscle, an infrahyoid muscle, is innervated by cervical spinal nerve 1 via the hypoglossal nerve. Two roots make up the ansa cervicalis, a superior root, an inferior root; the superior root of the ansa cervicalis is formed from cervical spinal nerve 1 of the cervical plexus. These nerve fibers travel in the hypoglossal nerve before separating in the carotid triangle to form the superior root; the superior root goes around the occipital artery and descends on the carotid sheath. It sends off branches to the superior belly of the omohyoid muscle, the upper parts of the sternothyroid and sternohyoid muscles and is joined by the inferior root.
The inferior root of the ansa cervicalis known as descendens cervicalis, is formed by fibers from spinal nerves C2 and C3. The inferior root gives off branches to the inferior belly of the omohyoid muscle, the lower parts of the sternothyroid and sternohyoid muscles. "Ansa cervicalis." Stedman's Medical Dictionary, 27th ed.. ISBN 0-683-40007-X Gray's Anatomy: The Anatomical Basis of Clinical Practice.. ISBN 0-443-07168-3 Anatomy figure: 25:03-08 at Human Anatomy Online, SUNY Downstate Medical Center Photo and description at Tufts University MedicalMnemonics.com: 1042 http://www.med.mun.ca/anatomyts/nerve/cerplex.htm
The hypoglossal nerve is the twelfth cranial nerve, innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus, innervated by the vagus nerve. It is a nerve with a motor function; the nerve arises from the hypoglossal nucleus in the brain stem as a number of small rootlets, passes through the hypoglossal canal and down through the neck, passes up again over the tongue muscles it supplies into the tongue. There are two hypoglossal nerves in the body: one on the left, one on the right; the nerve is involved in controlling tongue movements required for speech and swallowing, including sticking out the tongue and moving it from side to side. Damage to the nerve or the neural pathways which control it can affect the ability of the tongue to move and its appearance, with the most common sources of damage being injury from trauma or surgery, motor neuron disease; the first recorded description of the nerve is by Herophilos in the third century BC. The name hypoglossus springs from the fact that its passage is below the tongue, from hypo and glossa.
The hypoglossal nerve arises as a number of small rootlets from the front of the medulla, the bottom part of the brainstem, in the preolivary sulcus, which separates the olive and the pyramid. The nerve passes through the subarachnoid space and pierces the dura mater near the hypoglossal canal, an opening in the occipital bone of the skull. After emerging from the hypoglossal canal, the hypoglossal nerve gives off a meningeal branch and picks up a branch from the anterior ramus of C1, it travels close to the vagus nerve and spinal division of the accessory nerve, spirals downwards behind the vagus nerve and passes between the internal carotid artery and internal jugular vein lying on the carotid sheath. At a point at the level of the angle of the mandible, the hypoglossal nerve emerges from behind the posterior belly of the digastric muscle, it loops around a branch of the occipital artery and travels forward into the region beneath the mandible. The hypoglossal nerve moves forward lateral to the hyoglossus and medial to the stylohyoid muscles and lingual nerve.
It continues forward to the tip of the tongue. It distributes branches to the intrinsic and extrinsic muscle of the tongue innervates as it passes in this direction, supplies several muscles that it passes; the rootlets of the hypoglossal nerve arise from the hypoglossal nucleus near the bottom of the brain stem. The hypoglossal nucleus receives input from both the motor cortices but the contralateral input is dominant. Signals from muscle spindles on the tongue travel through the hypoglossal nerve, moving onto the lingual nerve which synapses on the trigeminal mesencephalic nucleus; the hypoglossal nerve is derived from the first pair of occipital somites, collections of mesoderm that form next to the main axis of an embryo during development. The musculature it supplies develop as the hypoglossal cord from the myotomes of the first four pairs of occipital somites; the nerve is first visible as a series of roots in the fourth week of development, which have formed a single nerve and link to the tongue by the fifth week.
The hypoglossal nucleus is derived from the basal plate of the embryonic medulla oblongata. The hypoglossal nerve provides motor control of the extrinsic muscles of the tongue: genioglossus, hyoglossus and the intrinsic muscles of the tongue; these represent all muscles of the tongue except the palatoglossus muscle. The hypoglossal nerve is of a general somatic efferent type; these muscles are involved in manipulating the tongue. The left and right genioglossus muscles in particular are responsible for protruding the tongue; the muscles, attached to the underside of the top and back parts of the tongue, cause the tongue to protrude and deviate towards the opposite side. The hypoglossal nerve supplies movements including clearing the mouth of saliva and other involuntary activities; the hypoglossal nucleus interacts with the reticular formation, involved in the control of several reflexive or automatic motions, several corticonuclear originating fibers supply innervation aiding in unconscious movements relating to speech and articulation.
Reports of damage to the hypoglossal nerve are rare. The most common causes of injury in one case series were compression by tumours and gunshot wounds. A wide variety of other causes can lead to damage of the nerve; these include surgical damage, medullary stroke, multiple sclerosis, Guillain-Barre syndrome, infection and presence of an ectatic vessel in the hypoglossal canal. Damage can be on both sides, which will affect symptoms that the damage causes; because of the close proximity of the nerve to other structures including nerves and veins, it is rare for the nerve to be damaged in isolation. For example, damage to the left and right hypoglossal nerves may occur with damage to the facial and trigeminal nerves as a result of damage from a clot following arteriosclerosis of the vertebrobasilar artery; such a stroke may result in tight oral musculature, difficulty speaking and chewing. Progressive bulbar palsy, a form of motor neuron disease, is associated with combined lesions of the hypoglossal nucleus and nucleus ambiguus with wasting of the motor nerves of the pons and medulla.
This may cause difficulty with tongue movements, speech and swallowing caused by dysfunction of several cranial nerve nuclei. Motor neuron disease is the most common disease affecting the hypoglossal nerve; the hypoglossal nerve is tested by examining its movements. At rest, if the
The occipital artery arises from the external carotid artery opposite the facial artery. Its path is below the posterior belly of digastric to the occipital region; this artery supplies blood to the back of the scalp and sterno-mastoid muscles, deep muscles in the back and neck. At its origin, it is covered by the posterior belly of the digastricus and the stylohyoideus, the hypoglossal nerve winds around it from behind forward, it next ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone, passes horizontally backward, grooving the surface of the latter bone, being covered by the sternocleidomastoideus, splenius capitis, longissimus capitis, digastricus, resting upon the rectus capitis lateralis, the obliquus superior, semispinalis capitis. It changes its course and runs vertically upward, pierces the fascia connecting the cranial attachment of the trapezius with the sternocleidomastoideus, ascends in a tortuous course in the superficial fascia of the scalp, where it divides into numerous branches, which reach as high as the vertex of the skull and anastomose with the posterior auricular and superficial temporal arteries.
Muscular branches: supply the digastric, stylohyoid and longus capitis muscles. Sternocleidomastoid branch: This branch divides into upper and lower branches in the carotid triangle; the upper branch accompanies the accessory nerve to the sternocleidomastoid, the lower branch arises near the origin of the occipital artery before entering the sternocleidomastoid muscle. This branch arises directly from the external carotid artery. Auricular branch: supplies the back of the ear. In many specimens, this branch gives rise to the mastoid branch, which supplies the dura mater and mastoid air cells. In other specimens, the mastoid artery is a branch of the occipital artery, rather than the auricular branch. Meningeal branch: supplies the dura mater in the posterior cranial fossa Descending branches: This is the largest branch, it descends on the posterior aspect of the neck, divides into a superficial and deep portion. The superficial portion supplies the trapezius muscle and anastomoses with the ascending branch of the transverse cervical.
The deep portion anastomoses with the vertebral artery and with the a. profunda cervicalis, a branch of the costocervical trunk. Thus, branches of the occipital artery participate in anastamosis between the external carotid and the subclavian artery, thereby providing collateral circulation, its terminal portion is accompanied by the greater occipital nerve. This article incorporates text in the public domain from page 556 of the 20th edition of Gray's Anatomy lesson4 at The Anatomy Lesson by Wesley Norman Diagram at stchas.edu Description at okstate.edu http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-2. HTM
Tufts University is a private research university in Medford and Somerville, Massachusetts. A charter member of the New England Small College Athletic Conference, Tufts College was founded in 1852 by Christian universalists who worked for years to open a nonsectarian institution of higher learning, it was a small New England liberal arts college until its transformation into a larger research university in the 1970s. The university emphasizes active citizenship and public service in all its disciplines, is known for its internationalism and study abroad programs. Tufts is organized into ten schools, including two undergraduate degree programs and eight graduate divisions, on four campuses in the Boston metropolitan area and the French Alps. Among its schools is the United States' oldest graduate school of international relations, the Fletcher School of Law and Diplomacy. Tufts' largest school is the School of Arts and Sciences, which offers undergraduate and graduate degrees and includes both the Graduate School of Arts and Sciences and the School of the Museum of Fine Arts at Tufts University, affiliated with the Museum of Fine Arts, Boston.
The School of Engineering has an entrepreneurial focus with the Gordon Institute and maintains close connections with the original college. The university has a campus in Downtown Boston that houses the medical and nutrition schools, affiliated with several medical centers in the area; the university offers joint undergraduate degree programs with the New England Conservatory, the Sciences Po Paris with additional programs with the University of Paris, University of Oxford and constituents of the University of London. Several of its programs have affiliations with the nearby institutions of Harvard University and the Massachusetts Institute of Technology. Alumni and affiliates include Nobel laureates, heads of state, senators, representatives and Academy Award winners, National Academy members. Tufts has graduated several Rhodes, Fulbright, Goldwater scholars. Other notable alumni include numerous CEOs and founders of Fortune 500 companies, high ranking U. S. diplomats, Pulitzer Prize winners.
In the 1840s, the Universalist Church wanted to open a college in New England, Charles Tufts donated 20 acres to the church in 1852 to help them achieve this goal. Charles Tufts had inherited the land, a barren hill, one of the highest points in the Boston area, called Walnut Hill, when asked by a family member what he intended to do with the land, he said "I will put a light on it", his 20-acre donation is still at the heart of Tufts' now-150 acre campus, straddling Somerville and Medford. It was in 1852 that the Commonwealth of Massachusetts chartered Tufts College, noting the college should promote "virtue and piety and learning in such of the languages and liberal and useful arts as shall be recommended". During his tenure, Ballou spent a year studying in the United Kingdom; the methods of instruction which he initiated were based on the tutorials that were conducted in the University of Oxford and the University of Edinburgh. Now more than 160 years old, Tufts is the third-oldest college in the Boston area.
Having been one of the biggest influences in the establishment of the College, Hosea Ballou II became the first president in 1853, College Hall, the first building on campus, was completed the following year. That building now bears Ballou's name; the campus opened in August 1854. President Ballou was succeeded by Alonzo Ames Miner. Though not a college graduate, his presidency was marked by several advances; these include the establishment of preparatory schools for Tufts which include Goddard Seminary, Westbrook Seminary, Dean Academy. During the Civil War the college supported the Union cause; the mansion of Major George L. Stearns which stood on part of the campus was a station on the Underground Railroad. In addition to having the largest classes spring up, 63 graduates served in the Union army; the first course of a three-year program leading to a degree in civil engineering was established in 1865, the same year MIT was founded. By 1869, the Crane Theological School was organized. Miner's successor, Elmer Capen was the first president to be a Tufts alumnus.
During his time, one of the earliest innovators was Amos Dolbear. In 1875, as chair of the physics department, he installed a working telephone which connected his lab in Ballou Hall to his home on Professors Row. Two years Alexander Graham Bell would receive the patent. Dolbear's work in Tufts was continued by Marconi and Tesla. Other famous scholars include William Leslie Hooper who in addition to serving as acting president, designed the first slotted armature for dynamos, his student at the college, Frederick Stark Pearson, would become one of America's pioneers of the electrical power industry. He became responsible for the development of the electric power and electric street car systems which many cities in South America and Europe used. Another notable figure is Stephen M. Babcock who developed the first practical test to determine the amount of butterfat in milk. Since its development in the college, the Babcock Test has hardly been modified. Expansion of the chemistry and biology departments were led by scholars Arthur Michael, one of the first organic chemists in the U.
S. and John Sterling Kingsley, one of the first scholars of comparative anatomy. P. T. Barnum was one of the earliest benefactors of Tufts College, the Barnum Museum of Natural History was constructed in 1884 with funds donated by him to house his collection of animal specimens and the stuffed hide of Jumbo the elephant, who would become the university'
The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipose tissue beneath the skin; the deep cervical fascia of the neck includes four parts: The investing layer The carotid sheath The pretracheal fascia The prevertebral fascia The carotid sheath is located at the lateral boundary of the retropharyngeal space at the level of the oropharynx on each side of the neck and deep to the sternocleidomastoid muscle, extending from the base of the skull to the first rib and sternum. The four major structures contained in the carotid sheath are: the common carotid artery as well as the internal carotid artery internal jugular vein the vagus nerve the deep cervical lymph nodesThe carotid artery lies medial to the internal jugular vein, the vagus nerve is situated posteriorly between the two vessels. In the upper part, the carotid sheath contains the glossopharyngeal nerve, the accessory nerve, the hypoglossal nerve, which pierce the fascia of the carotid sheath.
The ansa cervicalis is embedded in the anterior wall of sheath. It is formed by "descendens hypoglossi" and "descendens cervicalis"; the three major fascial layers in the neck contribute to the carotid sheath: the investing fascia, the pretracheal fascia, the prevertebral fascia. The cervical part of the sympathetic trunk is embedded in prevertebral fascia posterior to the sheath. Axillary fascia MedEd at Loyola grossanatomy/dissector/labs/h_n/pharynx/ph2_1a.html lesson8 at The Anatomy Lesson by Wesley Norman MedicalMnemonics.com: 669 Cross section at tufts.edu
Cervical spinal nerve 1
The cervical spinal nerve 1 is a spinal nerve of the cervical segment. C1 carries predominantly motor fibres, but a small meningeal branch that supplies sensation to parts of the dura around the foramen magnum, it originates from the spinal column from above the cervical vertebra 1. Muscles innervated by this nerve are: Geniohyoid muscle- through Hypoglossal nerve Rectus capitis anterior muscle Longus capitis muscle Rectus capitis lateralis muscle Splenius cervicis muscle Rectus capitis posterior major muscle levator scapulae muscle Thyrohyoid muscle – through hypoglossal nerve Omohyoid – through Ansa cervicalis Sternohyoid – through Ansa cervicalis
The infrahyoid muscles are a group of four pairs of muscles in the anterior part of the neck. The four infrahyoid muscles are: the sternohyoid, sternothyroid and omohyoid muscles; the infrahyoid muscles either insert on to the hyoid bone. The term infrahyoid refers to the region below the hyoid bone, while the term strap muscles refers to the long and flat muscle shapes which resembles a strap; the stylopharyngeus muscle is considered by many to be one of the strap muscles, but is not an infrahyoid muscle. The origin and innervation of the individual muscles: All of the infrahyoid muscles are innervated by the ansa cervicalis from the cervical plexus except the thyrohyoid muscle, innervated by fibers only from the first cervical spinal nerve travelling with the hypoglossal nerve; the infrahyoid muscles function to depress the hyoid larynx during swallowing and speech. Muscular triangle Suprahyoid muscles