Tag: Infrahyoid muscles

Infrahyoid muscles

INFRAHYOID MUSCLES


INTRODUCTION:

  • The infrahyoid muscles (strap muscles) are a group of four pairs of muscles in the anterior (frontal) part of the neck.
  • The four infrahyoid muscles are; the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles.
  • The infrahyoid muscles either originate from or insert on to the hyoid bone.
  • Omohyoid is a digastric muscle.
  • Omohyoid is an important landmark for anterior & posterior triangle of neck .
  • 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.
Muscle Origin Insertion Innervation
Sternohyoid Posterior surface of manubrium sterni, adjoining parts of clavicle and the posterior sternoclavicular ligament Medial part of lower border of hyoid bone Ansa cervicalis
Sternothyroid Posterior surface of manubrium sterni and adjoining part of first costal cartilage Oblique line of thyroid cartilage Ansa cervicalis
Thyrohyoid Oblique line of thyroid cartilage Lower border of the body and the greater cornu of the hyoid bone Cervical spinal nerve 1 via the hypoglossal nerve
Omohyoid (superior belly) Intermediate tendon Hyoid bone Superior root of ansa cervicalis (C1)
Omohyoid (inferior belly) Superior border of scapula Intermediate tendon Ansa cervicalis (C1-C3)

INNERVATION:

  • All of the infrahyoid muscles are innervated by the ansa cervicalis from the cervical plexus (C1-C3) except the thyrohyoid muscle, which is innervated by fibers only from the first cervical spinal nerve travelling with the hypoglossal nerve.

ACTION:

  • The infrahyoid muscles function to depress the hyoid bone and larynx during swallowing and speech.
Exam Question
 
  • Sternothyroid & thyrohyoid are Attached to oblique line of thyroid cartilage.
  • Omohyoid is a digastric muscle.
  • Omohyoid is an important landmark for Anterior & posterior triangle.
  • Sternthyroid, sternohyoid & omohyoid are the muscles innervated my ansa cervicalis.
  • All infrahyoid muscles depresses larynx.
Don’t Forget to Solve all the previous Year Question asked on INFRAHYOID MUSCLES

Infrahyoid muscles

INFRAHYOID MUSCLES

Q. 1  All  of  the  following  muscles are  attached to oblique line of thyroid cartilage except
 A Superior constrictor
 B Inferior constrictor
 C Thyrohyoid
 D Stern thyroid
Q. 1  All  of  the  following  muscles are  attached to oblique line of thyroid cartilage except
 A Superior constrictor
 B . Inferior constrictor
 C Thyrohyoid
 D Stern thyroid
Ans. A

Explanation:

Superior constrictor

MUSCLE

Superior constrictor (Constrictor

of pharynx)

ORIGIN

i. Pterygoid hamulus

ii. Pterygomandibular raphe

iii. Medial surface of mandible (near lower      attachment of pterygomandibular raphe

INSERTION

Median raphe on posterior wall of

pharynx

Inferior constrictor (Constrictor of

Two parts: pharynx)

i. Thyropharyngeus – from thyroid

cartilage (oblique line of thyroid cartilage)

ii. Cricopharyngeus  –  from  cricoid

cartilage

Median raphe on posterior wall of

pharynx

Sternothyroid (Infrahyoid muscle)

i. Posterior surface of manubrium

sterni

ii. Adjoining  part  of  first  costal cartilage

Oblique line of thyroid cartilage

Thyrohyoid (Infrahyoid muscle)

Oblique line of thyroid cartilage

Lower border of body and greater

cornua of hyoid bone


Q. 2

All of the following are Digastric muscles, except?

 A

Muscle fibers in the ligament of Treitz

 B

Omohyoid

 C

Occipitofrontalis

 D

Sternocleidomastoid

Q. 2

All of the following are Digastric muscles, except?

 A

Muscle fibers in the ligament of Treitz

 B

Omohyoid

 C

Occipitofrontalis

 D

Sternocleidomastoid

Ans. D

Explanation:

Digastric muscles refers to muscles with two bellies. Sternocleidomastoid has two heads but it does not have two bellies and hence this muscle cannot be termed as a digastric muscle.


Q. 3

Which of the following hyoid muscles is an important landmark in both the anterior and posterior triangles of the neck?

 A

Geniohyoid

 B

Mylohyoid

 C

Omohyoid

 D

Sternohyoid

Q. 3

Which of the following hyoid muscles is an important landmark in both the anterior and posterior triangles of the neck?

 A

Geniohyoid

 B

Mylohyoid

 C

Omohyoid

 D

Sternohyoid

Ans. C

Explanation:

The omohyoid muscle is an important landmark in both the anterior and posterior triangles of the neck. In the anterior triangle, the superior belly of the omohyoid muscle serves as the superolateral border of the muscular triangle and the anterior border of the carotid triangle. In the posterior triangle, the inferior belly of the omohyoid muscle divides the omoclavicular triangle from the occipital triangle. So, in both the anterior and posterior triangles, the omohyoid is an important muscle that subdivides the triangles.
 
All of the other listed muscles are associated with the anterior triangle only. Geniohyoid runs from the hyoid bone to the genu of the mandible.it is a deep muscle on the floor of the mouth. It is found deep to the submental triangle. Mylohyoid is another muscle associated with the floor of the mouth.It is in the submandibular triangle and the submental triangle. Sternohyoid is a strap muscle;it is in the muscular triangle. 

Q. 4

Which muscle is innervated by a branch of the ansa cervicalis?

 A

Sternocleidomastoid

 B

Platysma

 C

Sternohyoid

 D

Trapezius

Q. 4

Which muscle is innervated by a branch of the ansa cervicalis?

 A

Sternocleidomastoid

 B

Platysma

 C

Sternohyoid

 D

Trapezius

Ans. C

Explanation:

The sternohyoid muscle is one of the strap muscles which runs from the manubrium and the sternal end of the clavicle to the hyoid bone. It is innervated by the ansa cervicalis, and it depresses and stabilizes the hyoid bone. Platysma is a muscle of facial expression; it is innervated by the cervical branch of CN VII, the facial nerve. Sternocleidomastoid and trapezius are both innervated by the accessory nerve (CN XI). Sternocleidomastoid receives fibers from C2 and C3 for proprioception, while trapezius receives proprioceptive fibers from C3 and C4.

Q. 5

All are elevators of larynx except:

 A

Thyrohyoid

 B

Digastric

 C

Stylohyoid

 D

mylohyoid

Q. 5

All are elevators of larynx except:

 A

Thyrohyoid

 B

Digastric

 C

Stylohyoid

 D

mylohyoid

Ans. A

Explanation:

 

 The main laryngeal elevators are: Digastric anterior and posterior, the stylohyoid, mylohyoid, geniohyoid, genioglossus, hyoglossus, and thyropharyngeus muscles



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