Introduction Of Myology-muscles Of The Head And Neck Ruan-2015.ppt

03-23-2015

Myology is the study of the muscular system. Three types muscles: 1. Skeletal muscles - striated muscle tissue attached to bones. 2. Cardiac muscle - a type of involuntary striated muscle found in the heart, specifically the myocardium. 3. Smooth muscle - an involuntary non-striated muscle.

Features of structures 1) Striated fibers

2) Multinucleated 3) Voluntary control

Features of structures

1) 2) 3) 4)

striations intercalated disks（闰盘） contain three nuclei autonomic control

Intercalated discs （闰盘） •Intercalated discs are part of the cardiac muscle sarcolemma. •Individual heart muscle cells (cardiomyocytes) are connected by intercalated discs to work as a single functional organ (syncytium ，合胞体). •Support synchronised contraction of cardiac tissue. •They occur at the Z line of the sarcomere (肌节） and can be easily visualized in longitudinal section of the tissue.

• Three types of adhering junctions make up an intercalated disc — 1) Fascia adherens are anchoring sites for actin, and connect to the closest sarcomere(肌节）. 2) Macula adherens （ desmosomes， 桥粒）stop separation during contraction . 3) Gap junctions allow action potentials to spread between cardiac cells.

Features of structures

1) 2) 3) 4)

No striations spindle-shaped single nuclei autonomic control

1) Myofibrils 2) Sarcolemma 3) Endomysium

4) Perimysium（cover the fasciculus) 5) Epimysium

Many muscles consist of muscle belly and tendon • A muscle belly -the fleshy central part of a muscle

• A tendon is a tough band of fibrous connective tissue that

usually connects muscle to bones and is capable of withstanding tension.

1) 2) 3) 4)

Parallel Convergent Circular muscle Pennate   

Unipennate Bipennate Multipennate

• Origin – the proximal and least movable attachment • Insertion – the distal and movable attachment

Supplementary structures of muscles 1. Fascia a layer of fibrous tissue that interpenetrates and surrounds muscles, bones, organs, nerves, blood vessels and other structures. (1) Superficial fascia  found in the subcutis in most regions of the body.  is comprised mainly of loose areolar connective tissue and adipose. 

(2) Deep fascia • the dense fibrous connective tissue . • provides connection and communication in the form of aponeuroses, ligaments, retinacula, joint capsules, and septa.

2 . synovial bursa 

a small fluid-filled sac lined by synovial membrane with an inner

capillary layer of slimy fluid. 

provides a cushion between bones and tendons and/or muscles around a joint.

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helps to reduce friction between the bones and allows free movement.

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are found around most major joints of the body.

synovial bursa

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Synovial folds

3 . Tendon sheath • Two layers of membranse around a tendon. • synovial sheath(inner) • fibrous tendon sheath(outer) • permits the tendon to move.

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4. Sesamoid bones • a bone embedded within a tendon. • found in locations where a tendon passes over a joint, such as the hand, knee(patella), and foot. • protect the tendon and to increase its mechanical effect. • maintain a more consistent moment arm through a variety of possible tendon loads.

Sesamoid bones

Skeletal Muscular System • Is controlled by the nervous system. • Is allowed to move • Shapes our body

Skeletal Muscular System

There are approximately 639 skeletal muscles in the human body. Their functions are as follows 1. Produce movement Muscle pulls tendons to move the skeleton 2. Maintain posture and body position Continuous muscle contraction 3. Support soft tissue Support weight of visceral organs 4. Guard entrances and exits Encircle openings to digestive and urinary tracts. Control swallowing, defecation and urination 5. Maintain body temperature Energy from contraction is converted to heat

1. Axial musculature Any of the skeletal muscles of the trunk or head.

2. Appendicular musculature Any of the skeletal muscles of the limbs.

1. Muscles of facial expression (innervated by cnVII) (1) Epicranius (occipitofrontalis) 

a muscle which covers parts of the skull.

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consists of three parts : 

Frontalis

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Epicranial aponeurosis

( galea aponeurotica) 

Occipitalis

Action: • Draws the scalp back which raises the eyebrows and wrinkles the forehead. 

(2) Orbicularis oculi 

the sphincter muscle of the eyelids, which surrounds

the circumference of the orbit. Action: 

closes the eyelids.

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compresses the lacrimal

sac to help tears drained into the nasal cavity.

(3) Muscles around the mouth 1) Orbicularis oris

2) levator labii superioris 3) Zygomaticus 4) Depressor labii inferioris

5) Buccinator 6) Depressor anguli oris 7) Platysma

Action:  Movement of mouth  Facial expression

2. Muscles of mastication (innervated by cnV) (1 )The masseter 

a thick and quadrilateral muscle.

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Origin: the inferior border of the zygomatic arch

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Insertion: the lateral surface of the ramus and angle of the mandible.

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Action : elevates mandible (close mouth)

(2 )The temporalis 

Origion: the temporal fossa

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Insertion: the coronoid process of the mandible.

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Action : elevates mandible and retract the lower jaw

(3) The medial pterygoid 

Origin: the lateral pterygoid plate of the sphenoid bone, the maxillary tuberosity and the pyramidal process of the palatine bone

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Insertion: the medial surface of the ramus and angle of the mandible.

• Action : 

It closes the jaw and helps in mastication.

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It elevates the jaw, and pulls it forward.

The medial pterygoid

maxillary tuberosity

(4 )The lateral pterygoid 

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Superior head  Origin: the greater wing of the sphenoid bone  Insertion: the articular disc and fibrous capsule of the TMJ. Inferior head  Origin: the lateral pterygoid plate  Insertion: the neck of the mandible. Action:  pull the coronoid process anteriorly, protrude the mandible.  Help to lower the mandible and open the jaw

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Muscles of mastication

I. Superficial muscles of the neck (1) Platysma 

a superficial muscle in the superficial fascia of the neck.

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ORIGIN - Skin over lower neck and upper lateral chest.

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INSERTION- Inferior border of mandible and skin over lower face and angle of mouth

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ACTION - Depresses and wrinkles skin of lower face and mouth. Aids forced depression of mandible

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NERVE - Cervical branch of facial nerve (VII)

(2)Sternocleidomastoid muscle(SCM) Innervation by cn XI 

Origin - The medial (sternal) head arises from manubrium, and the lateral (clavicular) head from the clavicle.

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Insertion - the mastoid process.

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Action: 

Flexes neck sideways, bringing ear to shoulder.

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Stabilizes head when tilting chin upward, or during talking and chewing.

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Assists in swallowing.

2.muscles associated with the hyoid bone (1) Suprahyoid muscles :

①Digastric muscle 

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Two bellies united by a central tendon connected to the body of the hyoid bone. Anterior belly origins from digastric fossa of the lower border of the mandible. Posterior belly origins from the mastoid process.

①Digastric muscle Action : • elevates the hyoid when the mandible is fixed. • depresses the mandible when the hyoid is fixed. Innervations: the posterior belly by the facial nerve, the anterior belly by the mylohyoid nerve(cnV).

② Mylohyoid-forms the floor of the oral cavity    

Origins :the mylohyoid line of the mandible Inserts: the hyoid bone Nerve supply from the mylohyoid nerve(cn V) Action:  

elevates the floor of the mouth and tongue. depresses the jaw when the hyoid is fixed.

Mylohyoid muscles

③Stylohyoid •Origins: the styloid process of the temporal bone •Inserts: the hyoid bone • Nerve supply from the facial nerve • Action: elevates the hyoid bone.

④Geniohyoid 

Origins : from the mental spine of the mandible

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Inserts : to the hyoid bone

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Nerve supply : the first and second cervical nerve(C1-2)

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Action: draws the hyoid forward or depresses the jaw when the hyoid is fixed.

(1) Suprahyoid muscles :

(2)Infrahyoid muscles (innervated by cervical ansa C1-C4) ①Sternohyoid • Origins : from the posterior border of the medial end of the clavicle, the posterior sternoclavicular ligament, and the upper and posterior part of the manubrium. • Inserts : the lower border of the body of the hyoid bone. • Action: depress the hyoid bone.

②Omohyoid • Origins : the inferior belly origins from the upper border of the scapula, • Inserts : the superior belly attaches into the hyoid bone

• Two bellies connected by an intermediate tendon • Action: depresses the hyoid.

③ Sternothyroid • Origins : from the episternum and the first or second costal cartilage • Inserts: into the thyroid cartilage • Action: depresses the larynx.

④Thyrohyoid • Origin: from the oblique line of the thyroid cartilage • Inserts: into the body of the hyoid bone

• Action: moves the hyoid bone closer to the larynx.

3. Deep cervical muscles (1) lateral vertebral muscles ( Scalene muscles) 

Scalene muscles are a group of three pairs of muscles in the lateral neck, namely the scalenus anterior, scalenus medius, and scalenus posterior.

(1) lateral vertebral muscles ( Scalene muscles)    

Originate: from the transverse processes of C2 to C7 vertebrae Insert : the first (ant. and med.) and second ribs(post.). innervated by the spinal nerves C4-C8. Action : the elevate the first rib and the second rib.

(2 )Medial group ①longus capitis 

Origins: from the transverse processes of C3-C6 vertebræ

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Insertes: into the inferior surface of the basilar part of the occipital bone.

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innervated by a branch of cervical plexus.

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Action: helps twist the neck and bend the neck forward.

②longus colli 

situated on the anterior

surface of the vertebral column between the atlas and the third thoracic vertebra. 

Innervated by anterior primary rami of C2-6

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Action ： flexes the neck anteriorly and laterally.

longus capitis & longus colli