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10-1
Muscular SystemGross Anatomy
Chapter 10
10-2
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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10-3
Muscle attachment
10-4
Muscle Types
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10-5
Examples of Muscle Shapes
10-6
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)
10-8
Muscle Anatomy: Anterior View
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Muscle Anatomy: Posterior View
10-10
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.
10-12
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
10-14
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)
10-16
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
10-20
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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10-21
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
10-22
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
10-24
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
10-26
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
10-28
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
10-30
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.
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