Download Muscles of the Forearm

Quiz II
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Muscles of the Anterior Neck and Throat:
Suprahyoid & Infrahyoid
Neck is divided into 2 triangles (anterior & posterior) by the
sternocleidomastoid muscle
Anterior Triangle:
Suprahyoid muscles (found above hyoid bone)
Infrahyoid muscles (found below hyoid bone)
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Muscles of the Anterior Neck and Throat:
Suprahyoid & Infrahyoid
Events of Swallowing (After tongue and buccinator
squeeze food back toward the pharynx…)
1) Suprahyoid muscles pull the hyoid bone upward
and forward toward the mandible resulting in the
widening of the pharynx and closing the respiratory
passageways
The hyoid bone is attached by the thyrohyoid
membrane to the larynx, the larynx is also pulled
upward & forward which widens the pharynx and
closes the respiratory passageway (feel it…and try
to breathe)
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Muscles of the Anterior Neck and Throat:
Suprahyoid & Infrahyoid
2) The tensor and levator veli palatini muscles close
the nasal passageways to prevent food entrance
3) The pharyngeal constrictor muscles propel food
through the pharynx into the esophogus
4) The infrahyoid muscles return the hyoid bone and
larynx back to their normal inferior position
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Muscles of the Anterior Neck and Throat:
Infrahyoid
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Figure 10.8b
Muscles of the Neck: Head Movements
Head is moved by muscles originating from the axial skeleton
Major head flexor is the sternocleidomastoid muscles
Synergists to head flexion are the suprahyoid and infrahyoid
Lateral head movements are accomplished by the sternocleidomastoid and
scalene muscles
Head extension is accomplished by the deep splenius muscles and aided by
the superficial trapezius
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Sternocleidomastoid: prime mover of active head
flexion (against resistance…e.g. when lying down)
each muscle alone rotates head toward the shoulder on
the opposite side
Scalenes: elevate 1st two ribs (aids inspiration and head
rotation/flexion)
Splenius: acts as a group to extend or hyperextend the
head. Muscle alone on one side rotates & bends head
laterally toward the same side.
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Trunk Movements: Deep Back Muscles
Extension is effected by the deep or intrinsic back
muscles associated with the vertebral column
Think of each muscle as a string that, when
pulled, moves a vertebrae attached below it.
Superficial back muscles are associated with
movements of the shoulder girdle and upper limbs
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Trunk Movements: Deep Back Muscles
The prime mover of back extension is the erector
spinae
Controls bending forward via resistance. Powerful
extensors providing return to erect position.
Erector spinae, or sacrospinalis, muscles consist of
three columns on each side of the vertebrae –
iliocostalis, longissimus, and spinalis
Back muscles can extend and hyperextend the spine
Lateral bending of the back is accomplished by
unilateral contraction of these muscles
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Trunk Movements: Deep Back Muscles
Short muscles of the back:
Rotatores muscle
Multifidus muscle
Interspinales muscle
Intertransversarii muscle
All act as synergists in extension
and rotation of the spine
The trunk muscles maintain the
curvature of the spine
Postural muscles
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Deep Back Muscles
Longissimus: thoracis & cervicis act together to extend
vertebral column. Capitis extends head & turns face
toward the same side.
Spinalis: extends vertebral column
Semispinalis: “ “ & head, and rotates them to the
opposite side. Acts synergistically w/
sternocleidomastoid muscles of the opposite side.
Quadratus lumborum: flexes vertebral column laterally
when acting separately. Together maintains posture.
Assists in forced inspiration
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Trunk Movements: Deep Back Muscles
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Figure 10.9d
Trunk Movements: Deep Back Muscles
The primary function of deep thoracic muscles is to
promote movement for breathing
Try this at home…
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Muscles of Respiration: External Intercostals
External intercostals muscles (inspiratory muscles)– more
superficial layer that lifts the rib cage and increases thoracic
volume to allow inspiration
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Figure 10.10a
Muscles of Respiration: The Diaphragm
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Figure 10.10b
Muscles of Respiration: Internal Intercostals &
Diaphram
Internal intercostals muscles– form deeper layer that aids in forced expiration by
depressing the rib cage
Quiet expiration is accomplished by relaxing the diaphram, external intercostals &
elastic recoil of lungs
Diaphragm – muscular partition between the thoracic and abdominopelvic
cavities.
Upon contraction it moves inferiorly and flattens increasing the volume of the
thoracic cavity.
Can be contracted voluntarily to put pressure on pelvic organ contents (e.g.
urine, feces, baby).
Served by the phrenic nerve.
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Figure 10.10a
Muscles of the Abdominal Wall
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Figure 10.11a
Muscles of the Abdominal Wall: Trunck Movements &
Compression of Abdominal Viscera
Area of no bony reinforcement
Alteration of fasicle directions formed by the external (\) & internal (/)
obliques and the transversus abdominus (-) muscles gives greater
strength
These 3 muscles blend into the broad aponeuroses anteriorly and enclose
the rectus abdominus fusing and forming the linea alba
The “Ab” muscles protect and support the viscera, lateral flexion,
rotation of the trunk, and anterior flexion (e.g. sit-ups)
They relax during inspiration (try it!)
Involved with urination, defecation, childbirth, vomiting, coughing,
screaming, and sneezing (…uh, don’t try these in class)
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Muscles of the Pelvic Floor: Pelvic Diaphragm
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Figure 10.12a
Muscles of the Pelvic Floor (Pelvic
Diaphragm)
The pelvic diaphragm is composed of two paired
muscles – levator ani and coccygeus
These muscles:
Close the inferior outlet of the pelvis
Support the pelvic floor
Elevate the pelvic floor to help release feces
Resist increased intra-abdominal pressure
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Muscles of the Pelvic Floor
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Figure 10.12b
Muscles Inferior to the Pelvic Floor
Two sphincter muscles allow voluntary control of
urination (external urethral sphincter) and
defecation (external anal sphincter)
The ischiocavernosus and bulbospongiosus assist
in erection of the penis and clitoris
Central tendon of the perineum: site of insertion of
the perineal muscles
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Extrinsic Shoulder Muscles
Muscles of the thorax
Most muscles of the thorax run from the ribs and the
vertebral column to the shoulder girdle
They fix the scapula to the wall of the thorax and move the
scapula
Anterior: pectoralis major, pectoralis minor, serratus
anterior, and subclavius
Posterior: latissimus dorsi, trapezius muscles, levator
scapulae, and rhomboids
These muscles are involved with the movements of the
scapula including elevation, depression, rotation, and lateral
and medial movements
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Extrinsic Shoulder Muscles
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Figure 10.13a
Extrinsic Shoulder Muscles
Most scapular movements are promoted by the
serratus anterior muscles (anteriorly) & posterior
muscles (described later).
A simple movement of the scapula involves the
concerted effort of several muscles working in
combination
Prime movers of shoulder elevation are the
trapezius and levator scapulae
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Extrinsic Shoulder Muscles
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Figure 10.13b
Extrinsic Shoulder Muscles
Trapezius, serratus anterior, latissimus dorsi
depress the scapulae against resistance
Serratus anterior is involved mainly in the forward
movements (abduction) of the scapula (pushing,
punching, see next slide)
Trapezius and rhomboids are involved in retraction
(adduction) of the scapula
Thus, the serratus anterior and trapezius &
rhomboids are antagonists in forward/backward
movement of the scapula
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The Boxer’s Muscle
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Muscles Crossing the Shoulder joint: Movements of the Arm
Nine muscles cross the shoulder joint and insert
into the humerus
Prime movers include:
Pectoralis major – arm flexion
Latissimus dorsi and posterior fibers of the deltoid
– arm extension
Middle fibers of the deltoid – arm abduction
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Muscles Crossing the Shoulder
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Figure 10.14a
Rotator Cuff
Supraspinatus, infraspinatus, teres minor,
subscapularis (rotator cuff)
They originate on the scapula and their tendons
blend with the fibrous capsule of the shoulder joint
en route to the humerus.
Function to reinforce the capsule of the shoulder
joint to prevent dislocation of the humerus
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Muscles Crossing the Shoulder
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Figure 10.14d
Muscles Crossing the Shoulder
Coracobrachialis and teres major: Act as synergists for the latissimus
dorsi and pectoralis major. Do not contribute to reinforcement of the
shoulder joint
Pectoralis Major: prime mover for arm flexion (lifting the arm anteriorly)
Latissimus dorsi and deltoid muscles: prime movers for arm extension
Teres major: synergist for latissimus dorsi and deltoid muscles
Deltoid: prime mover of arm abduction
Pectoralis major and latissimus dorsi: prime movers for arm adduction
Thus, the pectoralis major and latissimus dorsi & deltoids are antagonists
in the flex/extension of the arm
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Muscles Crossing the Shoulder
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Figure 10.14a
Muscles Crossing the Elbow: Flex/extension of the forearm
Forearm extension
The triceps brachii is the prime mover of forearm extension
Forearm flexion: chief movers
Brachialis (Strongest flexor of elbow, synergist to b. brachii)
Biceps brachii [Strong flexor of elbow (supinated)]
Brachioradialis (Weakest)
These three are involved with elbow flexion due to their origin and
insertion points
Biceps brachii also supinates the forearm and is ineffective in flexing
the elbow when the forearm is pronated (e.g. palms down)
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Muscles of the Forearm: Movements of the Wrist, Hand, and Fingers
Forearm muscles consist of the anterior flexors and the posterior extensors
Anterior Forearm:
Pronator quadratus: prime mover of forearm pronation
Pronator teres: pronates forearm
Flexor carpi radialis: powerful flexor of wrist, abducts hand
Flexor digitorum superficialis: flexes wrist and middle fingers 2-5
Deep Muscles:
Flexor pollicis longus: flexes distal phalanx of thumb
Flexor digitorum profundus: flexor of all fingers. Flexes distal
interphalangeal joints
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Muscles of the Forearm
Posterior Forearm:
Extensor carpi radialis longus: extends & abducts wrist
Extensor carpi radialis brevis: “ “
Extensor digitorum: prime movers of finger extension
Extensor carpi ulnaris: extends & adducts wrist
Deep Muscles:
Supinator: assists biceps brachii to supinate forearm
Abductor pollicis longus: abducts/extends thumb
Extensor pollicis brevis & longus: extends thumb
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Muscles of the Forearm: Anterior
Compartment
These muscles are
primarily flexors
of the wrist and
fingers
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Figure 10.15a
Muscles of the Forearm: Anterior
Compartment
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Figure 10.15b, c
Muscles of the Forearm: Posterior
Compartment
These muscles are
primarily extensors
of the wrist and
fingers
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Figure 10.16a
Muscles of the Forearm: Posterior
Compartment
These muscles are
primarily extensors of
the wrist and fingers
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Figure 10.16b
Muscle Action of the Arm: Summary
The posterior extensor and anterior flexor muscles
are shown
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Figure 10.17a
Muscle Action of the Forearm: Summary
Posterior extensors of the wrist and fingers, and
anterior flexor muscles are shown
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Figure 10.17b
Intrinsic Muscles of the Hand: Fine Movement of the
Fingers
All muscles are in the palm of the hand (none on
the dorsal side
All muscles move the metacarpals and fingers
All are weak muscles involved in controlling
precise movements (e.g., threading a needle)
They are the main abductors and adductors of the
fingers
Produce opposition – move the thumb toward the
little finger
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Intrinsic Muscles of the Hand
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Figure 10.18a
Intrinsic Muscles of the Hand (Deeper View)
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Figure 10.18b
Intrinsic Muscles of the Hand: Groups
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Figure 10.18c, d
Intrinsic Muscles of the Hand
Thumb:
Abductor pollicis brevis: abducts thumb
Flexor pollicis brevis: flexes thumb
Opponens pollicis: opposition
Adductor pollicis: adducts thumb, aids opposition
Little Finger:
Abductor digiti minimi: abducts little finger
Flexor digiti minimi brevis: flexes little finger
Opponens digiti minimi: aids in opposition
…and the rest
Lumbricalis: flex fingers
Palmar interossei: adductors of fingers toward 3rd digit
Dorsal interossei: abductors of fingers
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