Download Ch11.Muscles.LectureI

MUSCLES OF THE BODY
Ch 11
Leonardo Da Vinci
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
Muscles of the Body
• Skeletal muscles
– Produce movements
• General principles of leverage
• Muscles act with or against each other
• Criteria used in naming muscles
Naming the Skeletal Muscles
• Location
– Example  the brachialis is located on the
arm (brachium)
• Shape
– Example  the deltoid is triangular
• Relative size
– Maximus, minimus, & longus indicate size
– Example  gluteus maximus is the large one
& gluteus minimus is the small one
Naming the Skeletal Muscles
• Direction of fascicles & muscle fibers
– Name tells direction in which fibers run
– Example  rectus abdominis & transversus
abdominis (rectus = straight up; transverse 
across or at right angle to midline)
• Location of attachments  name
reveals point of origin & insertion
– Example  brachioradialis
Naming the Skeletal Muscles
• Number of origins
– 2, 3, or 4 origins
– Indicated by the words biceps (2), triceps (3),
& quadriceps (4)
• Action
– Action can be part of the muscle’s name
– Indicates type of muscle movement
• Flexor, extensor, adductor, or abductor
(ie. extensor digitorum)
Arrangement of Fascicles in
Muscles
• Skeletal muscles  consist of fascicles
– Fascicles  arranged in different patterns
– Fascicle arrangement  tells about action of
a muscle
Arrangement of Fascicles in
Muscles
• Types of fascicle arrangement
– Parallel  fascicles run parallel to the long
axis of the muscle
• Strap-like  sternocleidomastoid
• Fusiform  biceps brachii
Arrangement of Fascicles in
Muscles
• Types of fascicle arrangement
– Convergent
• Origin of the muscle is broad
• Fascicles converge toward the tendon of insertion
• Example  Pectoralis major
Arrangement of Fascicles in
Muscles
• Types of fascicle arrangement
– Pennate
• Unipennate  fascicles insert into one side of the
tendon
• Bipennate  fascicles insert into the tendon from
both sides
• Multipennate  fascicles insert into one large
tendon from all sides
Arrangement of Fascicles in
Muscles
• Circular
– Fascicles are arranged in concentric rings
• Surround external body openings
• Sphincter  general name for a circular muscle
• Examples
– Orbicularis oris & orbicularis oculi
Arrangement of Fascicles in Muscles
(a)
(b)
(a) Circular
(orbicularis oris)
(e)
(c)
(b) Convergent
(pectoralis major)
(d)
(f)
(g)
(c) Fusiform
(biceps brachii)
(d) Parallel
(sartorius)
(e) Multipennate
(deltoid)
(f) Bipennate
(rectus femoris)
(g) Unipennate (extensor
digitorum longus)
Lever Systems: Bone-Muscle
Relationships
• Movement of skeletal muscles involves
leverage
– Lever  a rigid bar that moves
– Fulcrum  a fixed point
– Effort  applied force
– Load  resistance
Lever Systems
Effort x length of effort arm = load x length of load arm
(force x distance) = (resistance x distance)
Effort
10
kg
0.25 cm
Effort
25 cm
Fulcrum
Load
10 x 25 = 1000 x 0.25
250 = 250
1000 kg
Load
(a) Mechanical advantage with a power lever
Fulcrum
Lever Systems: Bone-Muscle
Relationships
• Bones  act as levers
• Joints  act as fulcrums
• Muscle contraction  provides effort
– Applies force where muscle attaches to bone
• Load  bone, overlying tissue, & anything
being lifted
Lever Systems: Bone-Muscle
Relationships
• Levers allow a given effort to
– Move a heavier load
– Move a load farther
Lever Systems: Bone-Muscle
Relationships
• First-class lever
– Effort applied at one end
– Load is at the opposite end
– Fulcrum is located between load & effort
(a) First-class lever
(a) First-class lever
Arrangement of the elements is Arrangement of the elements is
load-fulcrum-effort.
load-fulcrum-effort.
Load
Effort
L
Fulcrum
Fulcrum
Load
L
Load
Fulcrum
Example: scissors
Effort
Effort
In the body: A first-class lever system
raises your head off your chest. The
posterior neck muscles provide the effort;
the atlanto-occipital joint is the fulcrum;
and the weight to be lifted is the facial
skeleton.
Lever Systems: Bone-Muscle
Relationships
• Third-class lever
– Effort is applied between the load & fulcrum
– Work speedily
– Always at a mechanical disadvantage
(c) Third-class lever
(c) Third-class lever
Arrangement of the elements is
load-effort-fulcrum.
Load
Arrangement of the elements is
load-effort-fulcrum.
Effort
Effort
L
Fulcrum
Load
Load
L
Fulcrum
Fulcrum
Effort
Example: tweezers or forceps
In the body: Flexing the forearm by the
biceps brachii muscle exemplifies
third-class leverage. The effort is exerted
on the proximal radius of the forearm; the
fulcrum is the elbow joint; and the load is
the hand and distal end of the forearm.
Embryonic Development of
the Muscles
• Muscles organized into 4 groups
– Musculature of the visceral organs
– Pharyngeal arch muscles
– Axial muscles
– Limb muscles
Embryonic Development of
the Muscles
• Musculature of the visceral organs
– Includes smooth & cardiac muscle
– Develops from splanchnic mesoderm
• Pharyngeal arch muscles
– Includes
• Skeletal muscles of the pharynx
• Muscles of the head & neck
– Develop from the 4th to 7th somitomeres
Development of the Muscles
First (occipital)
myotomes
Somitomeres
Eye
Pharynx
Limb bud
Myotomes
Limb bud
(a) 6-week embryo
Pharyngeal Arch Muscles
Pharynx
Muscles of facial expression
e.g., orbicularis oculi
Chewing muscles
e.g., temporalis, masseter
Suprahyoid muscles (most)
Pharyngeal constrictors
(key swallowing muscles)
Trapezius
(c) Pharyngeal arch (branchiomeric) muscles:
4th–7th somitomeres
Axial Muscles
• Lie anterior & posterior to the body axis
• Muscles of the:
– Thorax, abdomen, & pelvis
• And many muscles of the:
– Neck & some of the head
• Function to move the trunk & maintain
posture
Axial Muscles
Extrinsic muscles
of the eye
Deep muscles of the back
e.g., erector spinae
Tongue
Muscles of the anterior
& lateral trunk
e.g., 1. infrahyoid muscles
Tongue
(neck)
muscles
2. intercostal muscles
(thorax)
3. external & internal
obliques (abdomen)
4. muscles of the
pelvic floor
(d) Axial muscles: 1st–3rd somitomeres and myotomes
Limb Muscles
• Limb muscles arise from lateral parts of
nearby myotomes
• Extensors
– Muscle mass dorsal to limb bones
• Flexors
– Muscle mass ventral to limb bones
Limb Muscles
Extensors
e.g., triceps brachii,
extensor digitorum
Extensors
Flexors
(e) Limb muscles: From myotomes
Flexors
e.g., biceps brachii,
flexor carpi radialis
Extensors
e.g., quadriceps
femoris, tibialis
anterior
Flexors
e.g., hamstrings,
gastrocnemius
Muscle Actions & Interactions
• A muscle cannot reverse the movement it
produces
• Another muscle must undo the action
• Muscles with opposite actions lie on
opposite sides of a joint
Muscle Actions & Interactions
• Prime mover (= agonist)
– Has major responsibility for a certain movement
• Antagonist
– Opposes or reverses a movement
• Synergist  helps the prime mover
– By adding extra force
– By reducing undesirable movements
Muscle Actions & Interactions
(a) A muscle that crosses on the anterior side of
a joint produces flexion*
Example:
Pectoralis major
(anterior view)
*These generalities do not apply to the knee and ankle because the lower limb
is rotated during development. The muscles that cross these joints posteriorly
produce flexion, and those that cross anteriorly produce extension.
(b) A muscle that crosses on the posterior side of
a joint produces extension*
Example:
Latissimus dorsi
(posterior view)
*These generalities do not apply to the knee and ankle because the lower limb
is rotated during development. The muscles that cross these joints posteriorly
produce flexion, and those that cross anteriorly produce extension.
Muscle Actions & Interactions
(c) A muscle that crosses on the lateral side of a
joint produces abduction
Example:
Medial deltoid
(anterolateral view)
(d) A muscle that crosses on the medial side of a
joint produces adduction
Example:
Teres major
(posterolateral view)
Muscle Compartments of the
Limbs
• Dense fibrous connective tissue divides
limb muscles into compartments
• Muscles in opposing compartments are
– Agonist & antagonist pairs
• Each compartment is innervated by one
single nerve
Muscle Compartments of Arm &
Forearm
• The upper limb has anterior & posterior
compartments
– Anterior arm compartment muscles:
• Flex the shoulder or arm
• Innervation is the musculocutaneous nerve
(we’ll learn later)
– Anterior forearm compartment muscles:
• Flex the wrist & digits
• Innervation is the median or ulnar nerve (..later)
Muscle Compartments of the Arm
Extensors
Flexors
(a)
Triceps
brachii
Lateral
head
Long
head
Medial
head
Posterior compartment
of arm (extends elbow);
innervation: radial nerve
Humerus
Brachialis
Short head
Long head
(a) Muscles of the arm
Anterior compartment of
arm (flexes elbow); innervation:
musculocutaneous nerve
Biceps brachii
Muscle Compartments of the
Thigh
• Posterior compartment muscles
– Extend the hip & flex the knee
– Innervation is the tibial branch of the sciatic nerve (later)
• Anterior compartment muscles
– Flex the hip & extend the knee
– Innervation is the femoral nerve (later)
• Medial compartment
– Adduct the thigh
– Innervation is the obturator nerve (later)
Muscle Compartments of the Thigh
(a)
Adductors Hamstrings
Vastus
lateralis
Femur
Posterior compartment of
thigh (flexes leg and extends
thigh); innervation: tibial
nerve (portion of sciatic nerve)
Vastus
intermedius
Rectus femoris
Vastus medialis
Posterior compartment
muscles
Anterior compartment
Medial compartment
muscles
Anterior
compartment
(extends
(adducts thigh); innervation:
Medial compartment
leg); innervated by femoral nerve
obturator nerve
muscles of thigh and
lateral compartment
(a) Muscles of the thigh
muscles of leg
Lab Guide for Learning
the Muscles
Superficial Muscles of the Body
Shoulder
Trapezius
Deltoid
Head
Temporalis
Masseter
Arm
Triceps brachii
Biceps brachii
Brachialis
Forearm
Pronator teres
Brachioradialis
Flexor carpi radialis
Palmaris longus
Pelvis/thigh
Iliopsoas
Pectineus
Thigh
Rectus femoris
Vastus lateralis
Vastus medialis
Leg
Fibularis longus
Extensor digitorum
longus
Tibialis anterior
Facial
Epicranius, frontal belly
Orbicularis oculi
Zygomaticus
Orbicularis oris
Neck
Sternohyoid
Sternocleidomastoid
Platysma
Thorax
Pectoralis minor
Serratus anterior
Pectoralis major
Intercostals
Abdomen
Rectus abdominis
Internal oblique
Transversus abdominis
External oblique
Thigh
Tensor fasciae
latae
Sartorius
Adductor longus
Gracilis
Leg
Gastrocnemius
Soleus
Superficial Muscles of the Body
Arm
Triceps brachii
Brachialis
Forearm
Brachioradialis
Extensor carpi radialis
longus
Flexor carpi ulnaris
Extensor carpi ulnaris
Extensor digitorum
Iliotibial tract
Leg
Gastrocnemius
Soleus
Fibularis longus
Calcaneal
(Achilles) tendon
Neck
Epicranius, occipital belly
Sternocleidomastoid
Trapezius
Shoulder
Deltoid
Infraspinatus
Teres major
Rhomboid major
Triangle of auscultation
Latissimus dorsi
Hip
Gluteus medius
Gluteus maximus
Thigh
Adductor magnus
Gracilis
Hamstrings:
Biceps femoris
Semitendinosus
Semimembranosus
Muscles of the Head – Facial
Expression
• Muscles of facial expression
– Lie in the face & scalp
– Thin & variable in shape
– Often insert in the skin  not on bones
– (Innervated by cranial nerve VII  the facial
nerve)
Muscles of the Face & Head
Galea
aponeurotica
Frontal
belly
Corrugator supercilii
Orbicularis oculi
Levator labii
superioris
Epicranius
Occipital
belly
Temporalis
Zygomaticus
minor and major
Buccinator
Risorius
Orbicularis oris
Mentalis
Depressor
labii inferioris
Depressor anguli oris
Platysma
Masseter
Sternocleidomastoid
Trapezius
Splenius
capitis
Muscles of Mastication &
Tongue Movement
• 4 main pairs of muscles involved in
mastication
– Innervated by mandibular division of the trigeminal
nerve (cranial nerve V)
– Prime movers of jaw closure
• Masseter & temporalis
– Side-to-side movement
• Pterygoid muscles
– Compression of cheeks
• Buccinator muscles
PLAY
A&P Flix: Buccinator
PLAY
A&P Flix: Masseter
PLAY
A&P Flix: Temporalis
Muscles of Mastication & Tongue
Movement
Temporalis
Lateral
pterygoid
Orbicularis
oris
Medial
pterygoid
Masseter
Buccinator
Masseter
pulled away
(a)
(b)
Muscles of the Anterior Neck &
Throat – Swallowing
• The neck is divided into anterior &
posterior triangles
• Anterior triangle
– Divided into suprahyoid & infrahyoid muscles
– Participate in swallowing
• Pharyngeal constrictors
– Swallowing muscles  squeeze food into
esophagus
Muscles of the Anterior Neck & Throat
Tensor veli palatini
Levator veli palatini
Styloid process
Superior pharyngeal
constrictor
Middle pharyngeal
constrictor
Hyoid bone
Thyrohyoid
membrane
Inferior
pharyngeal
constrictor
Esophagus
Buccinator
Mandible
Mylohyoid
(cut)
Geniohyoid
Hyoglossus
Thyroid
cartilage
of larynx
Trachea
Muscles of the Neck & Vertebral
Column
• Head movement:
– Sternocleidomastoid
– Splenius muscles
– Neck movement – scalenes
1st cervical
vertebra
Base of
occipital
bone
Mastoid
process
Sternocleidomastoid
Middle
scalene
Anterior
scalene
Posterior
scalene
(a) Anterior
Muscles of the Neck & Vertebral Column
Mastoid process
Splenius capitis
Spinous processes
of the vertebrae
Splenius cervicis
(b) Posterior
Muscles of the Neck & Vertebral
Column
• Trunk extension
– Deep muscles of the back
• Maintain normal curvatures of the spine
• Form a column from sacrum to the skull
– Erector spinae group
• Largest of the deep back muscles
Muscles of the Neck & Vertebral Column
Mastoid process
of temporal bone
Longissimus capitis
Iliocostalis cervicis
Longissimus cervicis
Iliocostalis thoracis
Longissimus thoracis
Spinalis thoracis
Erector spinae
Ligamentum
nuchae
Semispinalis
capitis
Semispinalis
cervicis
Semispinalis
thoracis
Iliocostalis
Longissimus
Spinalis
Multifidus
Iliocostalis lumborum
External oblique
Quadratus
lumborum
PLAY
A&P Flix: Iliocostalis
PLAY
A&P Flix: Longissimus
PLAY
A&P Flix: Spinalis
Deep Muscles of the Thorax –
Breathing
• Deep muscles provide movements for
breathing
– External intercostal muscles
• Lift the rib cage during inhalation
– Internal intercostal muscles
• Aid expiration during heavy breathing
Deep Muscles of the Thorax—
Breathing
External
intercostal
Internal
intercostal
PLAY
A&P Flix: External intercostal muscles
PLAY
A&P Flix: Internal intercostal muscles
Deep Muscles of the Thorax –
Breathing
• Diaphragm
– Most important muscle of respiration!
– Flattens as it contracts
• Increases the volume of the thoracic cavity
• How does this aid in breathing?
• Innervated by phrenic nerve (your brain controls)
Deep Muscles of the Thorax—
Breathing
Xiphoid process of sternum
Foramen for inferior
vena cava
Foramen for
esophagus
Costal cartilage
Central
tendon of
diaphragm
Diaphragm
Foramen
for aorta
Lumbar
vertebra
12th rib
Quadratus
lumborum
Psoas major
Muscles of the Abdominal Wall
• Lateral & anterior abdominal wall
– Formed from 3 flat muscle sheets
• External oblique
• Internal oblique
• Transversus abdominis
– Fourth muscle pair
• Rectus abdominis
– Inserts at the linea alba
Muscles of the Abdominal Wall
Pectoralis major
Serratus
anterior
Linea alba
Tendinous
intersection
Transversus
abdominis
Rectus
abdominis
Internal oblique
External
oblique
Inguinal ligament
(formed by free
inferior border of
the external oblique
aponeurosis)
Aponeurosis
of the external
oblique
(a)
PLAY
A&P Flix: Internal obliques
PLAY
A&P Flix: External obliques
Muscles of the Abdominal Wall
External
oblique
Rectus
abdominis
Internal oblique
Transversus
abdominis
PLAY
A&P Flix: Transverse abdominis
PLAY
A&P Flix: Rectus abdominis
Muscles of the Pelvic Floor
• Pelvic floor (pelvic diaphragm)
• Sheet of 2 muscles
– Both support pelvic organs
• Levator ani
– Formed from iliococcygeus, puborectalis, &
pubococcygeus
• Coccygeus
Muscles of the Pelvic Floor
Anterior
Levator ani
Pubococcygeus
Symphysis pubis
IIiococcygeus
Urogenital diaphragm
Urethra
Vagina
Anal canal
Obturator
internus
Coccyx
Piriformis
Levator ani
Posterior
Coccygeus
Pelvic
diaphragm
Muscles of the Perineum
Midline raphe
Bulbospongiosus
Ischiocavernosus
Penis
Clitoris
Superficial
transverse
perineal
muscle
Urethral
opening
Vaginal
opening
Anus
Levator ani
Gluteus
maximus
Male
Female
Superficial Muscles of the
Anterior Thorax
• Movements of the scapula
– Pectoralis major
– Pectoralis minor
– Serratus anterior
– Subclavius
PLAY
A&P Flix: Pectoralis major
PLAY
A&P Flix: Pectoralis minor
PLAY
A&P Flix: Serratus anterior
Superficial Muscles of Anterior Thorax
Sternocleidomastoid
Subclavius
Clavicle
Deltoid
Pectoralis
major
Sternum
Biceps
brachii
Subscapularis
Pectoralis
minor
Coracobrachialis
Serratus
anterior
Humerus
Superficial Muscles of the
Posterior Thorax
• Movements of the scapula
– Trapezius
– Levator scapulae
– Rhomboid major
– Rhomboid minor
PLAY
A&P Flix: Trapezius
PLAY
A&P Flix: Levator scapulae
PLAY
A&P Flix: Rhomboid major
PLAY
A&P Flix: Rhomboid minor
Superficial Muscles of the Posterior Thorax
Levator
scapulae
Trapezius
Supraspinatus
Clavicle
Deltoid
Rhomboid
minor
Rhomboid
major
Spine of scapula
Infraspinatus
Teres minor
Teres
major
Humerus
Latissimus
dorsi
Muscles Crossing the Shoulder
Joint
• Movements of the arm
– Deltoid
– Pectoralis major
Clavicle
Deltoid
Sternum
Pectoralis major
Coracobrachialis
Triceps brachii
Lateral head
Long head
Medial head
Biceps brachii
PLAY
A&P Flix: Deltoid
Brachialis
Brachioradialis
(a) Anterior view
Muscles Crossing the Shoulder
Joint
• Movements of the arm
PLAY A&P Flix: Latissimus dorsi
PLAY A&P Flix: Supraspinatus
PLAY A&P Flix: Infraspinatus
Supraspinatus
Spine of scapula
Deltoid (cut)
Greater tubercle
of humerus
Infraspinatus
Teres minor
Teres major
Triceps brachii
Lateral head
Long head
Latissimus dorsi
Humerus
Olecranon process
of ulna
Anconeus
(b) Posterior view
Muscles Crossing the Shoulder
Joint
Supraspinatus
• Movements of arm
PLAY
A&P Flix: Teres minor
Spine of scapula
Deltoid (cut)
Greater tubercle
of humerus
Infraspinatus
Teres minor
PLAY
A&P Flix: Teres major
Teres major
Triceps brachii
PLAY
A&P Flix: Subscapularis
Lateral head
Long head
Latissimus dorsi
Humerus
Olecranon process
of ulna
Anconeus
(b) Posterior view
Questions…?
What’s Next?
Lab: Muscles
Next Lecture: Muscles cont…
Wed Lab: Finish Muscles
& Review