Carotid Sinus vs Carotid body

 # Select the incorrect statement about the carotid sinus:

A. It is a dilatation near the beginning of the internal carotid artery

B. It is innervated by the glossopharyngeal nerve

C. It acts as a chemoreceptor

D. Its wall has thick tunica adventitia

The correct answer is C. It acts as a chemoreceptor; which is incorrect because carotid sinus is a baroreceptor. 

Carotid Sinus : The termination of the common carotid artery, or the beginning of the internal carotid artery shows a slight dilatation, known as the carotid sinus which receives a rich innervation from the glossopharyngeal and sympathetic nerves. The carotid sinus acts as a baroreceptor or pressure receptor and regulates blood pressure.

Carotid Body: Carotid body is a small, oval reddish-brown structure situated behind the bifurcation of the common carotid artery. It receives a rich nerve supply mainly from the glossopharyngeal nerve, but also from the vagus and sympathetic nerves. It acts as a chemoreceptor and responds to changes in the oxygen and carbon dioxide and pH content of the blood.

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The base of the submental triangle is formed by:

# The base of the submental triangle is formed by:

A. Chin

B. Anterior belly of digastric

C. Posterior belly of digastric

D. Hyoid bone

The correct answer is D. Hyoid bone.

Submental triangle is a median triangle. On each side, there is the anterior belly of the corresponding digastric muscles. Its base is formed by the body of the hyoid bone. Its apex lies at the chin. The floor of the triangle is formed by the right and left mylohyoid muscles and the median raphe uniting them.

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All of the infrahyoid muscles are supplied by ansa cervicalis EXCEPT:

 # All of the infrahyoid muscles are supplied by ansa cervicalis EXCEPT:

A. Thyrohyoid

B. Sternohyoid

C. Sternothyroid

D. Inferior belly of omohyoid

The correcct answer is A. Thyrohyoid.

Infrahyoid muscles are sternohyoid, sternothyroid, thyrohyoid and omohyoid present in the superficial plane of the anterior triangle of neck. Sternohyoid, sternothyroid, omohyoid are supplied by ansa cervicalis EXCEPT thyrohyoid which is supplied by the first cervical nerve through hypoglossal nerve.

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Suprahyoid Muscles and Infrahyoid Muscles

 # All of the following belongs to suprahyoid group of muscles EXCEPT:

A. Omohyoid

B. Mylohyoid

C. Stylohyoid

D. Geniohyoid

The correct answer is A. Omohyoid. 

Suprahyoid Muscles are: Digastric, Stylohyoid, Mylohyoid, Geniohyoid   @ Super Stylish Getho and Mylo Di. 

Infrahyoid muscles: Sternohyoid, Sternothyroid, Thyrohyoid, Omohyoid  (SH, ST, TH, OH)

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Torticollis or Wry Neck is the result of:

 # Torticollis or Wry Neck is the result of spasm of which of the following muscles?

A. Omohyoid and sternohyoid

B. Trapezius and Sternocleidomastoid

C. Platysma and mentalis

D. Scaleneus anterior and scaleneus posterior

The correct answer is B. Trapezius and Sternocleidomastoid

Torticollis or Wry neck is a deformity in which the head is bent to one side and the chin points to the other side. This is a result of spasm or contracture of the muscles supplied by the spinal accessory nerve, these being the sternocleidomastoid and the trapezius.

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Which of the following are called as ‘Signal nodes’?

 # Which of the following are called as ‘Signal nodes’?

A. Supraclavicular nodes

B. Jugulo-omohyoid

C. Jugulodigastric

D. Submandibular

The correct answer is A. Supraclavicular nodes

The left supraclavicular nodes or Virchow's or scalene nodes are also involved in malignant growths of distant organs, e.g. the stomach, the testis and other abdominal organs. Therefore, they are known as signal nodes. Scalene node biopsy is very helpful in the early diagnosis of such malignancies. 

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The origin of clavicular head of sternocleidomastoid muscle:

 # The origin of clavicular head of sternocleidomastoid muscle is from the:

A. Medial one third of the inferior surface of the clavicle

B. Lateral one third of the inferior surface of the clavicle

C. Medial one third of the superior surface of the clavicle

D. Lateral one third of the superior surface of the clavicle

The correct answer is C. Medial one third of the superior surface of the clavicle.

Origin of Sternocleidomastoid Muscle

1. The sternal head is tendinous and arises from the superolateral part of the front of the manubrium sterni.

2. The clavicular head is musculotendinous and arises from the medial one third of the superior surface of the clavicle.

Insertion of Sternocleidomastoid Muscle

It is inserted 

a) by a thick tendon into the lateral  surface of the mastoid process from its tip to its superior border, and 

b) by a thin aponeurosis into the lateral half of the superior nuchal line of the occipital bone.

Nerve Supply of Sternocleidomastoid

The spinal accessory nerve provides the motor supply. It passes through the muscle.

Blood supply of the sternocleidomastoid

One branch each from superior thyroid artery and suprascapular artery and two branches from the occipital artery.

Action of  Sternocleidomastoid muscle

# When one muscle contracts:

a) It turns the chin to the opposite side.

b) It can also tilt the head towards the shoulder. 

# When both muscles contract together:

a) They draw the head forwards as in eating and in lifting the head from a pillow. 

b) With the longus colli, they flex the neck against resistance. 

c) The reverse action helps in forced inspiration.

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