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Muscular SystemGross Anatomy

Chapter 10

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General Principles• Tendons: attach muscles to bones

– Aponeurosis: a very broad tendon• Muscle terminology

– Origin or head: muscle end attached to more stationary of two bones– Insertion: muscle end attached to bone with greatest movement– Belly: largest portion of the muscle between origin and insertion– Agonist: muscle that, when it contracts, causes an action– Antagonist: a muscle working in opposition to agonist– Synergists: muscles that work together to cause a movement

• Prime mover: plays major role in accomplishing movement• Fixators: stabilize joint/s crossed by the prime mover; prevent movement of

the origin of the prime mover.

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Muscle attachment

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Muscle Types

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Examples of Muscle Shapes

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Nomenclature

• Muscles are named according to:– Location: pectoralis gluteus, brachial– Size: maximus, minimus, longus, brevis– Shape: deltoid, quadratus, teres– Orientation: rectus– Origin and insertion: sternocleidomastoid,

brachioradialis– Number of heads: biceps, triceps– Function: abductor, adductor, masseter

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Muscle Movements

• Muscles and their tendons and bones act together as lever systems to move either parts of the body or the whole body. Muscle contractions are a pullor force by relative positions of

– Lever: rigid shaft or bone– Fulcrum: pivot point or joint– Weight or resistance (force of gravity either in the

form of the weight of the body parts or the weight of an object being lifted, pulled, or pushed)

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Muscle Anatomy: Anterior View

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Muscle Anatomy: Posterior View

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Head and Neck Muscles• Flexion: muscles deep within

the neck along the anterior margins of the vertebral bodies

• Extension: posterior neck muscles attached to occipital bone

• Rotation and abduction: lateral and posterior groups

• Examples: sternocleidomastoid, trapezius, splenius muscles

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Muscles of Facial Expression• Cutaneous; origin and

insertion in the superficial fascia.

• Confined primarily to head and neck.

• Move the skin; some act as sphincters.

• Examples: orbicularis oris, orbicularis oculi, platysma.

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Tongue Movements• Important in speech:

changes shape• Swallowing

– Moves food around in mouth

– Holds food in place during grinding

– Pushes food up to palate and back toward pharynx

• (Intrinsic: entirely within• Extrinsic: change in shape

and movement)

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Muscles of Larynx

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Extrinsic Muscles of the Eye• Rectus muscles: insert on

sclera anterior to center of sphere. Move eyeball and thus pupil laterally, superiorly, inferiorly, and medially

• Oblique muscles: insert onto the posterolateral margin of the eyeball and both laterally deviate the eyeball. The superior oblique passes through a pulley-like trochlea

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Muscles that Move the Vertebral Column

• Muscles that extend, laterally flex, and rotate the vertebral column. Used to produce erect posture

• Divided into deep and superficial groups– (Deep group: from vertebra

to vertebra– Superficial group extend

from vertebrae to ribs)

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Thoracic Muscles• Involved in breathing• Four groups associated with

rib cage– Scalenes: elevate first two ribs

during inspiration– External intercostals: elevate

the ribs– Internal intercostals: depress

ribs during expiration– Transversus thoracis: depresses

ribs during expiration– Diaphragm: major movement

of inspiration. Flattens during contraction and increases the volume of the thoracic cavity

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Abdominal Wall

• Flex and rotate vertebral column, decrease volume of abdominal and thoracic cavities

• Aid in forced expiration, vomiting, defecation, urination, childbirth

• Crossing pattern of muscles adds strength to abdominal wall to support organs

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Abdominal Wall

• Rectus Abdominis– Flexes vertebral column

• External abdominal oblique: flexes and rotates abdomen• Internal abdominal oblique: flexes and rotates abdomen• Transversus abdominis: compresses abdominal wall

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Scapular Movements

• Muscles that attach the upper limb to the body and move or stabilize the scapula and clavicle.

• Originate on the axial skeleton.

• Trapezius, levator scapulae, rhomboideus, serratus anterior, pectoralis minor

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Arm Movements• Muscles that attach arm

to thorax: pectoralis major, latissimus dorsi

• Deltoid and pectoralismajor both act as flexors and extensors of the shoulder

• Deltoid abducts and medially and laterally rotates arm

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Rotator Cuff• Primary muscles holding

humerus in the glenoidcavity

• Form a cuff or cap over the proximal humerus

• Involved in flexion, extension, abduction, adduction, rotation and circumduction

• Infraspinatus, subscapularis, supraspinatus, teres minor

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Forearm Movement

• Movements at the elbow• Extension: triceps brachii

and anconeus• Flexion: biceps brachii,

brachioradialis, and brachialis

• Supination and pronation: – Supination: supinator and

biceps brachii– Pronation: pronator quadratus

and pronator teres

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Wrist, Hand, and Finger

Movements

• Muscles on anterior surface of forearm: flexion as well as abduction and adduction of the wrist.

• Muscles on posterior surface of forearm: extension and abduction.

• Retinacula- bands of deep fascia which hold tendons of muscles of forearm, blood vessels, and nerves close to wrist. – Flexor retinaculum (transverse

carpal ligament): on the flexor surface

– Extensor retinaculum (dorsal carpal ligament): on the extensor surface

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Intrinsic Muscles of the Hand

• Originate and insert in hand.

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Thigh Movement• Originate on coxa; insert

onto femur• Anterior, posterolateral,

deep– Anterior: flex hip. Iliacus

and psoas major often referred to as iliopsoas since they share a tendon of insertion

– Posterolateral: gluteals and tensor fasciae lataeExtension of thigh

– Deep: thigh rotators

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Leg Movements• Quadriceps femoris: anterior surface of thigh

– Extension of the leg at the knee. – Rectus femoris also flexes the hip.– Insert by common tendon (patellar tendon) on and

around the patella– Patellar tendon extends from patella to tibial tuberosity

• Sartorius: flexes hip and knee, laterally rotates thigh

• Medial thigh muscles: adduction• Posterior thigh muscles: hamstrings. Flexion and

rotation of the knee

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Muscles that Move the Leg

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Ankle, Foot, and Toe

Movements

• Extrinsic foot muscles• Three leg compartments

– Anterior compartment: extensors involved in dorsiflexion and eversion/inversion of foot; extension of toes. Dorsiflexfoot, extend toes.

– Lateral compartment: plantar flexion and eversion.

– Posterior compartment-• Superficial muscles

(plantar flexion) have common tendon of insertion called the calcaneal (Achilles) tendon. Gastrocnemius, plantaris

• Deep muscles: plantar flex and invert foot

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Extrinsic Muscles of the Foot

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Extrinsic Muscles of the Foot

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Intrinsic Muscles of the Foot• Analogous to intrinsics

of hand, but serve in support and locomotion

• Flexion, extension, abduction and adduction of toes

• Deep fascia forms plantar aponeurosis.