TBL24 - Triangles of the Neck Flashcards
What does the SCM muscle divide the neck into? What muscles form the anterior and posterior boundaries of the posterior triangle, respectively?
1) The SCM muscle divides the neck into anterior and posterior triangles
2) The SCM and the trapezius muscle form the anterior and posterior boundaries of the posterior triangle, respectively
What is the anterior triangle bounded by posteriorly, superiorly, and anteriorly?
The anterior triangle is bounded posteriorly by the SCM, superiorly by the mandible, and anteriorly by the midline of the neck
Where does the SCM muscle attach to proximally and distally?
The SCM attaches proximally to the manubrium of the sternum and medial portion of the clavicle and distally to the mastoid process of the temporal bone
What is the SCM innervated by? What function does its unilateral contraction serve?
1) The SCM is innervated by the spinal accessory nerve (CN XI)
2) Its unilateral contraction tilts the head to the ipsilateral side and rotates the face superiorly toward the contralateral side
In the superficial fascia, how does the EJV cross the SCM? Where does the EJV drain the scalp in relation to the ear and where does the EJV terminate?
1) In the superficial fascia, the EJV diagonally crosses the SCM
2) After draining the scalp superior and posterior to the ear, the EJV terminates in the subclavian vein
What are common causes and symptoms of congenital torticollis?
1) Torticollis (L. tortus, twisted + L. collum, neck) is a contraction or shortening of the cervical muscles that produces twisting of the neck and slanting of the head
2) The most common type of torticollis (wry neck) results from a fibrous tissue tumor (L. fibromatosis colli) that develops in the SCM before or shortly after birth
3) Occasionally, the SCM is injured when an infant’s head is pulled too much during a difficult birth, tearing its fibers (muscular torticollis)
4) A hematoma (localized mass of extravasated blood) occurs that may develop into a fibrotic mass that entraps a branch of the spinal accessory nerve (CN XI) and thus denervates part of the SCM
What diagnostic signs could be indicated by prominence of the EJV?
1) The EJV may serve as an “internal barometer”
2) When venous pressure is in the normal range, the EJV is usually visible above the clavicle for only a short distance
3) However, when venous pressure rises (e.g., as in heart failure), the vein is prominent throughout its course along the side of the neck
4) Consequently, routine observation of the EJVs during physical examinations may give diagnostic signs of heart failure, SVC obstruction, enlarged supraclavicular lymph nodes, or increased intrathoracic pressure
What nerves form the cervical plexus and what does this plexus provide sensory branches to? What is the ansa cervicalis and what is it formed by?
1) The cervical plexus, which is formed by anterior rami of spinal nerves C1-C5, provides sensory branches (ignore their names) to the skin of the neck and superior shoulder, and the scalp posterior to the ear
2) The ansa cervicalis, the motor portion of the cervical plexus, is formed by loops of deep branches from the anterior rami
Where does the phrenic nerve arise from? What does it provide to the diaphragm? Where do its fibers refer pain from and to?
1) The phrenic nerve arises from anterior rami of C3-C5
2) It provides somatic motor fibers to the diaphragm
3) Its somatic sensory fibers refer pain from the diaphragm via DRG at C3-C5 to the root of the neck and superior shoulder
What are the middle and anterior scalene muscles enclosed by in the posterior triangle of the neck? What is the function of the scalene muscles?
1) The middle and anterior scalene muscles are enclosed by the prevertebral layer of deep cervical fascia in the posterior triangle of the neck
2) The scalene muscles contract during forced inspiration to the fix the 1st and 2nd ribs
What muscle does the phrenic nerve descend along? What vein crosses the anterior surface of this muscle inferiorly near its attachment to the first rib?
1) The phrenic nerve descends along the surface of the anterior scalene muscle
2) The subclavian vein crosses the anterior surface of the muscle inferiorly near its attachment to the 1st rib
Where do the subclavian artery and roots of the brachial plexus pass through in relation to the scalene muscles?
The subclavian artery and roots of the brachial plexus pass through the gap between the anterior and middle scalene muscles i.e., the interscalene triangle
Observe the IJV in the anterior triangle after partial removal of the muscular part of the pretracheal fascia and the carotid sheath. What does the IJV drain?
The IJV drains the brain, face, and cervical viscera
How is backflow into the IJV prevented when intrathoracic pressure is increased or when standing on one’s head?
1) The inferior end of the IJV dilates to form the inferior bulb of the IJV
2) This bulb has a bicuspid valve that permits blood to flow toward the heart while preventing back flow into the vein, as might occur if inverted (e.g., standing on one’s head or when intrathoracic pressure is increased)
What does the common carotid artery bifurcate into? Where does the internal carotid ascend to enter the skull? When the external carotid exits the carotid sheath, what does it supply?
1) The common carotid artery bifurcates into the internal and external carotid arteries
2) The internal carotid ascends in the carotid sheath to enter the skull
3) The external carotid exits the carotid sheath to mostly supply structures external to the skull
