General Discription Of Muscles

Chapter 3

Myology

Over 600 muscles in the body; Muscles are grouped by location: muscles of head; muscles of neck; muscles of thorax; muscles of Abdomen; muscles of upper limb; muscles of lower limb; ( muscles of pelvis and perineum ) Naming the skeletal muscles by sereral criteria: 1. location (brachialis); 2. shape (trapezius); 3. relative size of the muscle; 4. direction of the muscle fibers (rectus,oblique); 5. location of attachments(brachioradialis); 6. number of origins (biceps); 7. action (flexor,extensor)

Skeletal muscle: to move the skeleton Cardiac muscle: to form the heart Smooth muscle: to constitute viscera

Morphology of skeletal muscle Belly: the fleshy part of a muscle Tendon: the bundles consisting of connective tissue blending with strong collagen Different patterns of arrangement of the fascicles in muscles 1. Parallel arrangement: the long axes of the fascicles run parallel to the long axes of the muscle itself

Biceps

unipennate

bipennate

multipennate

2. Pennate pattern: feather-like muscle including unipennate, bipennate and multipennate arrangemengs 3. Convergent pattern: with a broad origin the fascicles converge toward a tendon 4. Circular pattern: arranged in concentric rings rectus

flate

orbicular

digastric

Origin, insertion and action of the muscles Origin: a fixed (less movable) attachment of a muscle Insertion: a movable attachment of a muscle The origin lies proximal to the insertion in the muscles of limbs Agonists ( prime movers ): the main muscles which contract to produce desired movement Antagonist: the muscles which act to oppose the action of agonist Synergists: the muscles which cooperate in performing an action Fixators: the muscles which steady the proximal parts of a limb while movements occur in distal parts

triceps

Fascia and tendinous sheath

Superficial fascia

Fascia 1) Superficial fascia: lies under skin and covers the entire body containing a lot of fat / increase mobility of skin; thermal insulation; a store of energy / contain cutaneous nerve, blood vessels and skin muscles 2) Deep fascia: dense and inelastic membrane of collagenous fibers Deep fascia Intermuscular septa Visceral layer

Parietal layer Fibrous sheath mesotendon

Tendinous sheath Consist of synovial sheath and fibrous sheath; exist only in hand and foot Synovial sheath 1. visceral layer 2. parietal layer / mesotendon: conjunctive structure between visceral and parietal layer Fibrous sheath outmost layer consisting of fibrous tissue

periosteum

Section 3

Muscles of Head and Neck

Muscles of the head 1. Craniofacial muscles: epicranius ( occipitofrontalis ) frontal belly + epicranial aponeurosis + occipital belly, orbicularis oculi, orbicularis oris 2. Masticatory muscles: masseter, temporalis, medial pterygoid, lateral pterygoid

ORBICULARIS ORIS

Origin Near midline on ant surface of maxilla and mandible and modiolus at angle of mouth

Insertion Mucous membrane of margin of lips and raphe with buccinator at modiolus

 

Action Narrows orifice of mouth, purses lips and puckers lip edges

                            Nerve Accessory parts are incisivus labii superioris and inferioris

ORBICULARIS OCULI Origin Med orbital margin and lacrimal sac(orbital, palpebral and lacrimal parts)

Insertion Lat palpebral raphe

 

Action Closes eyelids , aids passage and drainage of tears

                           

Nerve Temporal and zygomatic brs of facial N (VII)

MASSETER Origin Ant two thirds of zygomatic arch and zygomatic proces of maxilla

Insertion Lat surface of angle and lower ramus of mandible

 

Action Elevates mandible (enables forced closure of mouth)

                                 

Nerve Ant div of mandibular N (Vc)

TEMPORALIS Origin Temporal fossa between inf temporal line and infratemporal crest

Insertion Med and ant aspect of coronoid process of mandible

 

Action Elevates mandible and post fibres retract

                                  Nerve Deep temporal brs from ant div of mandibular N (Vc)

MEDIAL PTERYGOID

Origin Deep head. Med side of lat pterygoid plate and fossa between med and lat plates Superficial head : Tuberosity of maxilla and pyramidal process of palatine bone Insertion Med aspect of angle of mandible

 

Action Elevates, protracts and lat displaces mandible to opposite side for chewing

                                  Nerve N to medial pterygoid (main trunk of mandibular N (Vc))

LATERAL PTERYGOID

Origin Upper head: infratemporal surface of sphenoid bone. Lower head: lat surface of lat pterygoid plate Insertion Pterygoid fovea below condyloid process of mandible and intraarticular cartilage of temporomandibular jnt

 

                                 

Action Depresses and protracts mandible to open mouth. Pulls forward cartilage of jnt during opening of mouth Nerve Ns to lat pterygoid (ant div of mandibular N (Vc))

Muscles of the neck 1. Superficial group: platysma, sternocleidomastoid 2. Superhyoid muscles: digastric, mylohyoid, 3. Infrahyoid muscles: sternohyoid, omohyoid, sternothyroid, thyrohyoid 4. Deep cervical muscles: scalenus anterior, scalenus medius, scalenus posterior

PLATYSMA

Origin Skin over lower neck and upper lat chest

Insertion Inf border of mandible and skin over lower face and angle of mouth

 

Action Depresses and wrinkles skin of lower face and mouth. Aids forced depression of mandible                           Nerve Cervical br of facial N (VII)

STERNOCLEIDOMASTOID

Origin Ant and sup manubrium and sup med third of clavicle Insertion Lat aspect of mastoid process and ant half of sup nuchal line

 

Action Flexes and lat rotates cervical spine. Protracts head when acting together . Extends neck when neck already partially extended

                                  

Nerve Spinal accessory N (lat roots C1-5)

DIGASTRIC (ANTERIOR VIEW) DIGASTRIC Origin Ant belly: digastric fossa on post surface of symphysis menti. Post belly : base of med aspect of mastoid process

Insertion Firbrous loop to lesser cornu of hyoid bone

 

Action Elevates hyoid bone: Aids swallowing and depresses mandible

                                  

Nerve Ant belly: mylohyoid N (Vc). Post belly: facial N (VII)

MYLOHYOID

Origin Mylohyoid line on int aspect of mandible

Insertion Ant three quarters : midline raphe. Post quarter: sup border of body of hyoid bone

 

Action Elevates hyoid bone, supports and raises floor of mouth . Aids in mastication and swallowing

                                  

Nerve Mylohyoid N (Vc)

STYLOHYOID (ANTERIOR VIEW)

Origin Base of styloid process

Insertion Base of greater cornu of hyoid bone

 

Action Elevates and retracts hyoid bone. Aids swallowing and elevates larynx

                                  

Nerve Mandibular br of facial N (VII)

GENIOHYOID

Origin Inf mental spine on post surface of symphysis menti

Insertion Sup border of body of hyoid bone

 

Action Elevates and protracts hyoid bone. Depresses mandible                                    

Nerve C1 fibres carried by hypoglossal N (XII)

STERNOHYOID

Origin Sup lat post aspect of manubrium

Insertion Inf border of body of hyoid bone

 

Action Depresses hyoid bone and hence larynx

                                  

Nerve Ansa cervicalis N (C1, 2, 3)

OMOHYOID Origin Suprascapular lig and adjacent scapula

Insertion Inf border of body of hyoid bone

 

Action Depresses hyoid bone and hence larynx

                                   Nerve Ansa cervicalis N (C1,2,3)

STERNOTHYROID

Origin Med post aspect of manubrium

Insertion Oblique line of lamina of thyroid cartilage

 

Action Depresses larynx

                                   Nerve Ansa cervicalis N (C1, 2, 3)

THYROHYOID

Origin Oblique line of lamina of thyroid cartilage

Insertion Inf border of body of hyoid bone

 

Action Elevates larynx or depresses hyoid bone

                                   Nerve C1 fibres carried by hypoglossal N (XII)

SCALENUS ANTERIOR Origin Ant tubercles of transverse processes of C3-6

Insertion Scalene tubercle on sup aspect of 1st rib

 

Action Accessory to inspiration. Lat flexion of neck when 1st rib fixed                              Nerve Ant primary rami of C5, 6

SCALENUS MEDIUS

Origin Post tubercles of transverse processes of C2-7

Insertion Sup aspect of neck of 1st rib

 

Action Accessory to inspiration

                             Nerve Ant primary rami of C3-8

SCALENUS POSTERIOR Origin Post tubercles of transverse processes C4-6

Insertion Post/lat surface of 2nd rib

 

Action Accessory to inspiration

                             Nerve Ant primary rami of C6-8