Chapter 11: The Muscular System

Origins and Insertions Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) Most muscles originate or insert on the skeleton Origin is usually proximal to insertion

Muscle Interactions Muscles work in groups to maximize efficiency Smaller muscles reach maximum tension first, followed by larger, primary muscles

Muscle Terminology Based on Function Agonist (prime mover): –produces a particular movement Antagonist: –opposes movement of a particular agonist

Muscle Terminology Based on Function Synergist: –a smaller muscle that assists a larger agonist –helps start motion or stabilize origin of agonist (fixator)

Muscle Opposition Agonists and antagonists work in pairs: –when 1 contracts, the other stretches –i.e., flexors–extensors, abductors– adductors, etc.

Descriptive Names for Skeletal Muscles 1.Location in the body 2.Origin and insertion 3.Fascicle organization 4.Relative position 5.Structural characteristics 6.Action

Location in the Body Identifies body regions: –e.g., temporalis muscle

Origin and Insertion First part of name indicates origin Second part of name indicates insertion: –e.g., genioglossus muscle

Fascicle Organization Describes fascicle orientation within muscle: –i.e., rectus (straight), transversus, oblique

Relative Position Externus (superficialis): –visible at body surface Internus (profundus): –deep muscles Extrinsic: –muscles outside an organ Intrinsic: –muscles inside an organ

Structural Characteristics Number of tendons: – bi = 2, tri = 3 Shape: –trapezius, deltoid, rhomboid Size

Names for Muscle Size Longus = long Longissimus = longest Teres = long and round Brevis = short Magnus = large

Names For Muscle Size Major = larger Maximus = largest Minor = small Minimus = smallest

Action Movements: –e.g., flexor, extensor, retractor Occupations or habits: –e.g., risor = laughter

Axial and Appendicular Muscles Figure 11–3a

Axial and Appendicular Muscles Figure 11–3b

Divisions of the Muscular System 1.Axial muscles: –position head and spinal column –move rib cage –60% of skeletal muscles 2.Appendicular muscles: –support pectoral and pelvic girdles –support limbs –40% of skeletal muscles

The Axial Muscles Divisions based on location and function: –muscles of head and neck –muscles of vertebral column –oblique and rectus muscles –muscles of pelvic floor

Muscles of Facial Expression Figure 11–4a

Muscles of Facial Expression Figure 11–4b

3 Muscles of Mastication Masseter: –the strongest jaw muscle Temporalis: –helps lift the mandible Pterygoid muscles: –position mandible for chewing

Oblique and Rectus Muscles Lie within the body wall Figure 11–11a, b

Rectus Group Rectus abdominis: –between xiphoid process and pubic symphysis –divided longitudinally by linea alba –divided transversely by tendinous inscriptions

Rectus Group Diaphragmatic muscle or diaphragm: –divides thoracic and abdominal cavities –performs respiration

The Appendicular Muscles Figure 11–13a

The Appendicular Muscles Figure 11–13b

The Appendicular Muscles Position and stabilize pectoral and pelvic girdles Move upper and lower limbs

Muscles that Move the Arm Figure 11–15a

Muscles that Move the Arm Figure 11–15b

The Rotator Cuff Muscles involved in shoulder rotation –supraspinatus, subscapularis, infraspinatus, teres minor,and their tendons

Muscles that Move the Forearm and Hand Figure 11–16a

Muscles that Move the Forearm and Hand Figure 11–16b

Muscles that Move the Hand and Fingers Figure 11–17a, b

The Intrinsic Muscles of the Hand Figure 11–18a

The Intrinsic Muscles of the Hand Figure 11–18b

Muscles that Move the Thigh Figure 11–19a, b

Muscles that Move the Thigh Figure 11–19c, d

Muscles that Move the Leg Figure 11–20a

Muscles that Move the Leg Figure 11–20b, c

Hamstrings Made up of: –biceps femoris –semimembranosus –semitendinosus

Muscles that Move the Foot and Toes Figure 11–21a, b

Muscles that Move the Foot and Toes Figure 11–21c, d

The Achilles Tendon The calcaneal tendon (Achilles tendon): –shared by the gastrocnemius and soleus

The Intrinsic Muscles of the Foot Figure 11–22a

The Intrinsic Muscles of the Foot Figure 11–22b, c