•
•
•
•
Muscular System
Skeletal muscles work together or in
opposition to each other
Muscles can only pull, never push
As a muscle shortens, the insertion
(attachment on movable bone) moves toward
the origin (attachment on bone that does not
move)
Whatever one muscle or muscle group does,
another muscle or muscle group can “undo”
BIO L 105-lab 9 Muscle Gross Ana
1
Skeletal Muscles: Functional Groups
1. Prime movers-Agonist
– Provide major force for producing specific
movement
2. Antagonists
– Oppose or reverse specific movement
– May stretch or remain relaxed when prime mover
contracts
– Typically help regulate action of prime mover by
contracting slightly to help control movement
– Located on opposite sides of joint (from the
prime mover) on which it acts
BIO L 105-lab 9 Muscle Gross Ana
2
3. Synergists
•
•
Add force to a movement
Reduce undesirable or unnecessary movement
4. Fixators
•
Synergists that immobilize a bone or muscle’s origin to
add a stable base upon which to act
– Muscles which help maintain upright position
BIO L 105-lab 9 Muscle Gross Ana
3
Naming Skeletal Muscles
• Location—bone or body region associated
with the muscle
• Shape—e.g., deltoid muscle (deltoid =
triangle)
• Relative size—e.g., maximus (largest),
minimus (smallest), longus (long)
• Direction fibers or fascicles run in relation to
an imaginary line or longitudinal body axis
– Rectus- fibers run straight,
– Transversus-fibers run at right angles
– Oblique -fibers run at an oblique angle
BIO L 105-lab 9 Muscle Gross Ana
4
• Number of origins—e.g., biceps (2 origins) and
triceps (3 origins)
• Location of attachments—named according to
point of origin or insertion
– Sternocleidomastoid muscle—origin = sternum
and clavicle, insertion on mastoid process of
temporal bone
• Action—e.g., flexor or extensor
BIO L 105-lab 9 Muscle Gross Ana
5
Major Skeletal Muscles of the Body
• Grouped by function and location
• Information for each muscle
– Name and description—note information in name
– Origin and insertion—is usually a joint between origin and
insertion
– Action—insertion moves toward origin;
• best learned by acting out muscle movement on your own body
BIO L 105-lab 9 Muscle Gross Ana
6
Muscles of the Head
• Two groups
1. Muscles of facial expression
2. Muscles of mastication and tongue movement
Muscles of Facial Expression
• Insert into skin
• Important in nonverbal communication
• Epicranius (occipitofrontalis)
– 2 part muscle consisting of the
• Frontalis – raises eyebrows
• Occipitalis – pulls scalp backward
• Galea aponeurotica —cranial aponeurosis (fibrous
connective tissue sheet connecting these muscles
and part(s) they move)
BIO L 105-lab 9 Muscle Gross Ana
7
Muscles of the Torso
• Muscles of respiration
– External intercostals —more superficial muscles
that elevate ribs for inspiration
– Internal intercostals —deeper muscles that aid
forced expiration
– Diaphragm
• Partition between thoracic and abdominal
cavities
• Most important muscle in inspiration
BIO L 105-lab 9 Muscle Gross Ana
8
Muscles of the Abdominal Wall
• Fascicles of muscles run at angles to one another,
providing added strength
• Four paired muscles; their fasciae and aponeuroses
form lateral and anterior abdominal wall
– Internal obliques
– External obliques
– Transversus abdominis
– Rectus abdominis
BIO L 105-lab 9 Muscle Gross Ana
9
• Extrinsic shoulder muscles
– Act in combination to fix shoulder girdle (mostly the
scapula) and move it to increase range of arm
movements
– Actions include elevation, depression, rotation, lateral
and medial movements, protraction, and retraction
• Anterior extrinsic shoulder muscles
– Serratus anterior
– Pectoralis minor
– Subclavius
• (Pectoralis major considered later with muscles that act
on the humerus)
BIO L 105-lab 9 Muscle Gross Ana
10
Muscles Crossing the Shoulder Joint
• Insert on and move the humerus
– Three are prime movers of the arm
• Pectoralis major
• Latissimus dorsi
• Deltoid
– Actions include flexion, extension, adduction,
abduction, and rotation of humerus
BIO L 105-lab 9 Muscle Gross Ana
11
Selected Muscles of the Upper Arm
• Anterior flexor muscles
– Brachialis and biceps brachii —chief forearm
flexors
– Brachioradialis—synergist and stabilizer
• Posterior extensor muscles
– Triceps brachii —prime mover of forearm
extension
– Anconeus—weak synergist
BIO L 105-lab 9 Muscle Gross Ana
12
Muscles of the Forearm: Anterior
Compartment
• Flexors
– Flexor carpi radialis
– Palmaris longus
– Flexor carpi ulnaris
– Flexor digitorum muscles (superficialis and
profundus)
– Flexor pollicis longus
Muscles of the Forearm: Posterior
Compartment
• Extensors
– Extensor carpi radialis longus and brevis
– Extensor digitorum
– Extensor carpi ulnaris
– Extensor pollicis brevis and longus
– Extensor indicis
– Abductor pollicis longus
Muscles Crossing Hip and Knee Joints
• Most anterior muscles flex femur at hip and extend
lower leg at knee
• Most posterior muscles extend thigh and flex lower
leg
• Medial muscles all adduct thigh
Thigh extensors
• Hamstring muscles (prime movers of
extension)
– Biceps femoris
– Semitendinosus
– Semimembranosus
• Gluteus maximus (prime mover during
forceful extension)
Movements of the Thigh
• Abductors
– Gluteus maximus (also laterally rotates thigh)
– Gluteus medius (also medially rotates thigh)
– Gluteus minimus (also medially rotates thigh)
Anterior Leg Muscles
• Primary toe extensors and ankle dorsiflexors
– Tibialis anterior
• Flexors of foot and toes
– Gastrocnemius
– Soleus
Extrinsic Eye Muscles
• Six extrinsic eye muscles attach to scleral layer and
move eyeball
– Originate from bony orbit; insert on eyeball
– Enable eye to follow moving objects; maintain shape of
eyeball; hold in orbit
• Four rectus muscles originate from common
tendinous ring; names indicate movements
– Superior, inferior, lateral, medial rectus muscles
• Two oblique muscles move eye in vertical plane and
rotate eyeball
– Superior and inferior oblique muscles
LABWORK
Identify, describe, and state the actions of the selected
muscles in the handout provided.
BIO L 105-lab 9 Muscle Gross Ana
20