1. BIO L 105-lab 9 Muscle Gross Ana
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

2. BIO L 105-lab 9 Muscle Gross Ana
Skeletal Muscles: Functional Groups
Prime movers-Agonist
Provide major force for producing specific movement
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

3. BIO L 105-lab 9 Muscle Gross Ana
Synergists
Add force to a movement
Reduce undesirable or unnecessary movement
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

4. BIO L 105-lab 9 Muscle Gross Ana
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

5. BIO L 105-lab 9 Muscle Gross Ana
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

6. BIO L 105-lab 9 Muscle Gross Ana
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

7. BIO L 105-lab 9 Muscle Gross Ana
Muscles of the Head
Two groups
Muscles of facial expression
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

8. BIO L 105-lab 9 Muscle Gross Ana
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

9. BIO L 105-lab 9 Muscle Gross Ana
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

10. BIO L 105-lab 9 Muscle Gross Ana
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

11. BIO L 105-lab 9 Muscle Gross Ana
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

12. BIO L 105-lab 9 Muscle Gross Ana
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

13. Muscles of the Forearm: Anterior Compartment
Flexors
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Flexor digitorum muscles (superficialis and profundus)
Flexor pollicis longus

14. 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

15. 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

16. Hamstring muscles (prime movers of extension)
Thigh extensors
Hamstring muscles (prime movers of extension)
Biceps femoris
Semitendinosus
Semimembranosus
Gluteus maximus (prime mover during forceful extension)

17. Movements of the Thigh Anterior Leg Muscles
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

18. Flexors of foot and toes
Gastrocnemius
Soleus

19. 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

20. BIO L 105-lab 9 Muscle Gross Ana
LABWORK Identify, describe, and state the actions of the selected muscles in the handout provided.
BIO L 105-lab 9 Muscle Gross Ana