BIOLOGY 235 MIDTERM 2 REVIEW
CHAPTER 11: THE MUSCULAR SYSTEM
origin - stationary bone, usually proximal
Insertion - attachment of muscle's other tendon to movable bone, usually distal
belly (body) - fleshy portion of muscle between their tendons (origin and insertion)
Actions - main movements that occur when the muscle contracts
reverse muscle action (RMA) - during specific movements the actions are reversed;
• bones act as levers, and joints function as the fulcrums of these levers
• lever: rigid structure that can move around a fixed point called a fulcrum
• effort: causes movement force exerted by muscular contraction
• load or resistance: opposes movement.
• the load is typically the weight of the body part that is moved or some resistance that the moving
body part is trying to overcome - motions occur when effort applied at insertion exceeds the load
mechanical advantage - only needs small amount of force to move load over small distance
mechanical disadvantage - larger amount of force to overcome load
Lever types (3)
1. first-class levers - scissors and seesaws
a. produce either mechanical advantage or disadvantage
b. fulcrum is between effort and the load
2. second-class levers - wheelbarrow
a. always produce mechanical advantage
b. sacrifices speed and ROM for force
c. load is between fulcrum and the effort
3. third-class levers - most common in body
a. produce mechanical disadvantage
b. favors speed and ROM over force
c. effort between the fulcrum and the load
prime mover or agonist – contracts, causes an action
antagonist - stretches, yields to prime mover
synergists - aid movement of prime mover, prevent unwanted
movement Fixators - stabilize origin of prime mover, so it can move
more efficiently
Compartment - group of skeletal muscles, blood vessels and associated nerves have a common function - eg.
upper limbs: flexor compartment is anterior and extensor compartment is posterior
Classification of Skeletal Muscles (2):
1) Terms that refer to muscle features: pattern/direction of fascicles, size, shape, action, number of origins
and location
2) Sites of origin and insertion of the muscle
,Characteristics Used to Name Muscles:
Direction
Size
Shape
Action
Number of origins
Location
Origin and insertion
Muscles of the Head That Produce Facial Expressions
• ability to express emotion lie in subcutaneous layer
• Orifices: openings of the head - eyes, nose and mouth
• Sphincers: close orifices
• Dilators: dilate or open orifices
orbicularis oculi - closes the
eye occipitofrontalis - 2 parts:
Frontal belly (frontalis) - superficial to frontal bone, draws scalp anteriorly + raises eyebrows, wrinkles skin of
forehead horizontally
Occipital belly (occipitalis) - posterior part, superficial to occiptal bone + draws scalp posteriorly held together by
strong aponeurosis - covers superior and lateral surfaces of the skull
buccinator - forms major muscular portion of the cheek
Orbicularis oris - closes and protrudes lips, compresses lips against teeth and shapes lips during speech
Zygomaticus major - draws angle of mouth superiorly and laterally (smiling)
Muscles That Move the Mandible and Assist in Mastication
Masseter - strongest muscle of mastication
• Origin: Maxilla and zygomatic arch
• Insertion: angle and ramus of mandible
• Action: Elevates mandible (closes mouth)
temporalis
• Origin: temporal bone
• Insertion: coronoid process and ramus of mandible
• Action: elevates and retracts mandible
Muscles of the Neck That Move the Head
Balance and movement of the head on the vertebral column
Sternocleidomastoid - two bellies: sternal head and clavicular head
• Origin:
, o sternal head --> manubrium of sternum
o clavicular head --> medial third of clavicle
• Insertion: Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone
• Action: RMA: elevate sternum during forced inhalation
o Bilaterally - flexes cervical portion of the vertebral column and flexes the head
o Unilaterally - laterally flexes and rotates the head
Muscles of the Abdomen That Protect Abdominal Viscera
Anterolateral abdominal wall - composed of skin fascia and 4 pairs of muscles
external oblique - superficial muscle - fascicles extend inferiorly and medially
internal oblique - intermediate flat muscle - fascicles extend at right angles to external obliques
rectus abdominis - long muscle extending whole length of anterior abdominal wall
• Origin: pubic crest and pubic symphysis
• Insertion: cartilages of ribs 5-7 and the xiphoid process
• Action: Flexes vertebral column (esp. lumbar), compresses abdomen to aid in defecation,
urination, forced exhalation and childbirth (RMA: flexes pelvis on the vertebral column)
transversus abdominis - deep muscle, fascicles directed transversely around abdominal wall
• Together with internal and external oblique, structural arrangement of muscle fascicles in
different directions provide consideration protection to abdominal viscera
• Form linea alba
• During forceful exhalation – compresses abdomen
Muscles of the Thorax That Assist in Breathing
alter the size of thoracic cavity so breathing can occur
Inhalation: breathing in (thoracic cavity increases in size)
Exhalation: breathing out (thoracic cavity decreases in size)
diaphragm - important muscle that powers breathing - separates thoracic and abdominal cavities
• Convex superior surface - forms floor of thoracic cavity
• Concave inferior surface - forms roof of abdominal cavity
• Contraction of diaphragm causes it to flatten and increases vertical height in thoracic cavity
(inhalation) Relaxation of diaphragm causes it to move superiorly and decrease in height in thoracic cavity
(exhalation)
Intercostals - involved in breathing - in intercostal spaces (spaces between ribs)
1. external intercostals - 11 pairs occupy superficial layer, fibers run in an oblique direction interiorly
and anteriorly from rib above and rib below
a. Elevate ribs during inhalation - expends thoracic cavity
b. During relaxation: depress ribs and decreases anteroposterior and lateral dimensions of thoracic cavity
(exhalation)
2. internal intercostals - 11 pairs occupy intermediate layer of intercostal spaces, fibers run at right
angles to the external intercostals
a. Draw adjacent ribs together during forced exhalation - helps to decrease size of thoracic cavity
, Muscles of the Thorax That Move the Pectoral Girdle
scapular movements accompany humeral movements to increase ROM of the humerus
anterior thoracic muscles (3): subclavius, pectoralis minor, serratus anterior
pectoralis minor - thin, flat, triangular muscle - deep to pectoralis major
• origin: ribs 2-5, 3-5, 2-4
• insertion: clavicle
• action: depresses and moves clavicle anteriorly and helps stabilize pectoral
girdle posterior thoracic muscles (3): trapezius, levator scapulae, rhomboid minor
Trapezius - large, flat, triangular sheet of muscle - extends from the skull and vertebral column medially and to
the shoulder girdle laterally most superficial back muscle - covers posterior neck region and superior portion of
the trunk (found on both sides - form a diamond shape)
• origin: superior nuchal line of occipital bone, ligamentum nuchae and spines of c7-t12
• insertion: clavicle and acromion and spine of scapula superior fibers
• action: upward rotation of scapula middle fibers - adduction of scapula inferior fibers - depress
and upward rotation of scapula superior and inferior fibers - upward rotation, stabilizes scapula
o RMA - superior fibers help extend head
levator scapulae - narrow, elongated muscle
• origin: transverse processes of c1-c4
• insertion: superior vertebral border of scapula
• action: elevates scapula and rotates downward
rhomboid major - deep to trapezius - parallel bands that pass inferiorly and laterally from vertebrae to the
scapula
• Action: elevates and adducts scapula rotates it downward stabilizes scapula
Muscles of the Thorax and Shoulder That Move the Humerus
9 muscles cross the shoulder joint
2 do not originate on scapula (latissimus dorsi and pectoralis major) - axial muscles (originate on the axial
skeleton)
7 muscles originate on scapula - scapular muscles
pectoralis major - large, thick, fan-shaped - forms anterior fold of thorax
• origin: clavicular head, sternum and costal cartilages of ribs 2-6, sometimes ribs 1-7 (sternocostal
head) insertion: greater tubercle, lateral lip of intertubercular sulcus of humerus
• action: adducts and medially rotates arm at shoulder joint clavicular head - flexes arm sternocostal head
extends flexed arm to side of trunk
latissimus dorsi - broad, triangular muscle - inferior part of the back forming posterior wall of the axilla
"swimmers muscle" enables vertebral column and torso to be elevated (pullup)
• Action: extends, adducts and medially rotates arm at shoulder joint
• Draws arm inferiorly and posteriorly
o RMA: elevates vertebral column and torso
CHAPTER 11: THE MUSCULAR SYSTEM
origin - stationary bone, usually proximal
Insertion - attachment of muscle's other tendon to movable bone, usually distal
belly (body) - fleshy portion of muscle between their tendons (origin and insertion)
Actions - main movements that occur when the muscle contracts
reverse muscle action (RMA) - during specific movements the actions are reversed;
• bones act as levers, and joints function as the fulcrums of these levers
• lever: rigid structure that can move around a fixed point called a fulcrum
• effort: causes movement force exerted by muscular contraction
• load or resistance: opposes movement.
• the load is typically the weight of the body part that is moved or some resistance that the moving
body part is trying to overcome - motions occur when effort applied at insertion exceeds the load
mechanical advantage - only needs small amount of force to move load over small distance
mechanical disadvantage - larger amount of force to overcome load
Lever types (3)
1. first-class levers - scissors and seesaws
a. produce either mechanical advantage or disadvantage
b. fulcrum is between effort and the load
2. second-class levers - wheelbarrow
a. always produce mechanical advantage
b. sacrifices speed and ROM for force
c. load is between fulcrum and the effort
3. third-class levers - most common in body
a. produce mechanical disadvantage
b. favors speed and ROM over force
c. effort between the fulcrum and the load
prime mover or agonist – contracts, causes an action
antagonist - stretches, yields to prime mover
synergists - aid movement of prime mover, prevent unwanted
movement Fixators - stabilize origin of prime mover, so it can move
more efficiently
Compartment - group of skeletal muscles, blood vessels and associated nerves have a common function - eg.
upper limbs: flexor compartment is anterior and extensor compartment is posterior
Classification of Skeletal Muscles (2):
1) Terms that refer to muscle features: pattern/direction of fascicles, size, shape, action, number of origins
and location
2) Sites of origin and insertion of the muscle
,Characteristics Used to Name Muscles:
Direction
Size
Shape
Action
Number of origins
Location
Origin and insertion
Muscles of the Head That Produce Facial Expressions
• ability to express emotion lie in subcutaneous layer
• Orifices: openings of the head - eyes, nose and mouth
• Sphincers: close orifices
• Dilators: dilate or open orifices
orbicularis oculi - closes the
eye occipitofrontalis - 2 parts:
Frontal belly (frontalis) - superficial to frontal bone, draws scalp anteriorly + raises eyebrows, wrinkles skin of
forehead horizontally
Occipital belly (occipitalis) - posterior part, superficial to occiptal bone + draws scalp posteriorly held together by
strong aponeurosis - covers superior and lateral surfaces of the skull
buccinator - forms major muscular portion of the cheek
Orbicularis oris - closes and protrudes lips, compresses lips against teeth and shapes lips during speech
Zygomaticus major - draws angle of mouth superiorly and laterally (smiling)
Muscles That Move the Mandible and Assist in Mastication
Masseter - strongest muscle of mastication
• Origin: Maxilla and zygomatic arch
• Insertion: angle and ramus of mandible
• Action: Elevates mandible (closes mouth)
temporalis
• Origin: temporal bone
• Insertion: coronoid process and ramus of mandible
• Action: elevates and retracts mandible
Muscles of the Neck That Move the Head
Balance and movement of the head on the vertebral column
Sternocleidomastoid - two bellies: sternal head and clavicular head
• Origin:
, o sternal head --> manubrium of sternum
o clavicular head --> medial third of clavicle
• Insertion: Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone
• Action: RMA: elevate sternum during forced inhalation
o Bilaterally - flexes cervical portion of the vertebral column and flexes the head
o Unilaterally - laterally flexes and rotates the head
Muscles of the Abdomen That Protect Abdominal Viscera
Anterolateral abdominal wall - composed of skin fascia and 4 pairs of muscles
external oblique - superficial muscle - fascicles extend inferiorly and medially
internal oblique - intermediate flat muscle - fascicles extend at right angles to external obliques
rectus abdominis - long muscle extending whole length of anterior abdominal wall
• Origin: pubic crest and pubic symphysis
• Insertion: cartilages of ribs 5-7 and the xiphoid process
• Action: Flexes vertebral column (esp. lumbar), compresses abdomen to aid in defecation,
urination, forced exhalation and childbirth (RMA: flexes pelvis on the vertebral column)
transversus abdominis - deep muscle, fascicles directed transversely around abdominal wall
• Together with internal and external oblique, structural arrangement of muscle fascicles in
different directions provide consideration protection to abdominal viscera
• Form linea alba
• During forceful exhalation – compresses abdomen
Muscles of the Thorax That Assist in Breathing
alter the size of thoracic cavity so breathing can occur
Inhalation: breathing in (thoracic cavity increases in size)
Exhalation: breathing out (thoracic cavity decreases in size)
diaphragm - important muscle that powers breathing - separates thoracic and abdominal cavities
• Convex superior surface - forms floor of thoracic cavity
• Concave inferior surface - forms roof of abdominal cavity
• Contraction of diaphragm causes it to flatten and increases vertical height in thoracic cavity
(inhalation) Relaxation of diaphragm causes it to move superiorly and decrease in height in thoracic cavity
(exhalation)
Intercostals - involved in breathing - in intercostal spaces (spaces between ribs)
1. external intercostals - 11 pairs occupy superficial layer, fibers run in an oblique direction interiorly
and anteriorly from rib above and rib below
a. Elevate ribs during inhalation - expends thoracic cavity
b. During relaxation: depress ribs and decreases anteroposterior and lateral dimensions of thoracic cavity
(exhalation)
2. internal intercostals - 11 pairs occupy intermediate layer of intercostal spaces, fibers run at right
angles to the external intercostals
a. Draw adjacent ribs together during forced exhalation - helps to decrease size of thoracic cavity
, Muscles of the Thorax That Move the Pectoral Girdle
scapular movements accompany humeral movements to increase ROM of the humerus
anterior thoracic muscles (3): subclavius, pectoralis minor, serratus anterior
pectoralis minor - thin, flat, triangular muscle - deep to pectoralis major
• origin: ribs 2-5, 3-5, 2-4
• insertion: clavicle
• action: depresses and moves clavicle anteriorly and helps stabilize pectoral
girdle posterior thoracic muscles (3): trapezius, levator scapulae, rhomboid minor
Trapezius - large, flat, triangular sheet of muscle - extends from the skull and vertebral column medially and to
the shoulder girdle laterally most superficial back muscle - covers posterior neck region and superior portion of
the trunk (found on both sides - form a diamond shape)
• origin: superior nuchal line of occipital bone, ligamentum nuchae and spines of c7-t12
• insertion: clavicle and acromion and spine of scapula superior fibers
• action: upward rotation of scapula middle fibers - adduction of scapula inferior fibers - depress
and upward rotation of scapula superior and inferior fibers - upward rotation, stabilizes scapula
o RMA - superior fibers help extend head
levator scapulae - narrow, elongated muscle
• origin: transverse processes of c1-c4
• insertion: superior vertebral border of scapula
• action: elevates scapula and rotates downward
rhomboid major - deep to trapezius - parallel bands that pass inferiorly and laterally from vertebrae to the
scapula
• Action: elevates and adducts scapula rotates it downward stabilizes scapula
Muscles of the Thorax and Shoulder That Move the Humerus
9 muscles cross the shoulder joint
2 do not originate on scapula (latissimus dorsi and pectoralis major) - axial muscles (originate on the axial
skeleton)
7 muscles originate on scapula - scapular muscles
pectoralis major - large, thick, fan-shaped - forms anterior fold of thorax
• origin: clavicular head, sternum and costal cartilages of ribs 2-6, sometimes ribs 1-7 (sternocostal
head) insertion: greater tubercle, lateral lip of intertubercular sulcus of humerus
• action: adducts and medially rotates arm at shoulder joint clavicular head - flexes arm sternocostal head
extends flexed arm to side of trunk
latissimus dorsi - broad, triangular muscle - inferior part of the back forming posterior wall of the axilla
"swimmers muscle" enables vertebral column and torso to be elevated (pullup)
• Action: extends, adducts and medially rotates arm at shoulder joint
• Draws arm inferiorly and posteriorly
o RMA: elevates vertebral column and torso
