Skeletal Muscle Overview
Responsible for voluntary movements.
Connected to bones by tendons.
Muscle Functionality by Joint Position
Muscles crossing a joint influence movements around all axes of rotation associated with that joint.
Locating muscles on the skeleton helps predict movements:
Observe direction of muscle fibers indicating contraction and shortening.
Identify possible movements such as flexion, extension, abduction, adduction, medial rotation, and lateral rotation.
Basic Mechanics
Muscles only pull, they do not push.
Example:
Muscle: Biceps
Movement Completed: Flexion at the elbow.
Joint: Elbow
Axis of Rotation: Horizontal
Generality: Muscles crossing the elbow joint affect forearm movement.
Function of Muscles Across Joints:
SC joint: Moves the shoulder.
Shoulder joint: Moves the arm.
Elbow joint: Moves the forearm.
Wrist joints: Move the hand.
Joints of the digits: Move the fingers.
Similar functionality applies for the lower extremity.
Muscle Function by Location
Most anterior muscles serve as flexors and medial rotators.
Most posterior muscles function as extensors and lateral rotators.
Abduction and adduction depend on muscle position relative to the joint (superior or inferior).
Types of Muscles:
Axial Muscles:
Associated with the head, vertebral column, and thoracic cage (60% of skeletal muscles).
Appendicular Muscles:
Linked to pectoral and pelvic girdles and limbs (40% of skeletal muscles).
Types of Head and Neck Muscles:
Muscles of Facial Expression
Muscles of Mastication
Muscles of the Eye
Muscles of the Tongue
Muscles of the Pharynx
Muscles of the Larynx
Muscles that move the head
Key Muscles:
Frontalis: Raises eyebrows.
Obicularis Oris: Puckers lips.
Obicularis Oculi: Closes eyes.
Levator Labii Superioris: Raises lips.
Zygomaticus: Smile muscle.
Buccinator: Tightens cheeks.
Depressor Labii Inferioris: Lowers lips.
Key Muscles:
Masseter: Main muscle for chewing.
Muscles of the Pharynx and Larynx:
Control diameter of windpipe and throat.
Extrinsic Eye Muscles:
Aid in speech, pitch changes, and direct eye movement.
Suprahyoid Muscles: Elevate hyoid bone and depress mandible.
Infrahyoid Muscles: Depress hyoid bone; elevate larynx & pharynx.
Functions include chewing, talking, swallowing, singing.
Sternocleidomastoid: Functions as a head/neck rotator.
Functionality:
Head (neck) extensors aid in moving the head backward (looking up).
Muscle Attachment:
Primarily attached to spinous processes; some attach to transverse processes.
Function: Maintain trunk erect and extended.
Note: This is the most overworked muscle group; individual muscles not required to be memorized for lectures.
Intercostal Muscles:
Exterior: Pull up and away from each other.
Interior: Pull down and away.
Purpose: Maintain distance between ribs.
Obliques:
Exterior: Pull belly button up and away.
Interior: Pull belly button down and out.
Transverse Abdominis: Flattens abdomen.
Rectus Abdominis: Flexes the trunk.
Muscle Layers:
Most superficial: External obliques
Next layer: Internal obliques
Deeper: Transverse abdominis
Most internal: Rectus abdominis.
Other important structures: Aponeurosis, rectus sheath, linea alba.
Functionality:
Separates thoracic and abdominal cavities.
Primary muscle of respiration.
Inspiration: Involves contraction of diaphragm.
Expiration: Forceful expiration utilizes abdominal muscles.
Key Areas:
Urethral Sphincter: Controls urination.
Anal Sphincter: Controls defecation.
Note: Individual muscles are not required to be memorized.
Important Muscles:
Brachial muscles
Flexor carpi
Palmars longue
Flexor digitorum.
Various adaptations and branches are specified in the notes.
Main Muscles:
Deltoid: Covers shoulder joint and serves as arm abductor.
Rotator Cuff Muscles:
Supraspinatus: Arm abduction.
Infraspinatus: External rotation of the arm.
Teres Minor: External rotation and assists in adduction.
Subscapularis: Internal rotation.
Teres Major: Arm adductor; assists with internal rotation.
Key Muscles:
Biceps Brachii: Main elbow flexor.
Brachialis: Assists in elbow flexion.
Coracobrachialis: Assists in shoulder adduction and flexion.
Key Muscle:
Triceps Brachii: Role in extending elbow; consists of lateral, long, and medial head origins.
Key Muscles:
Pronator Teres: Arm pronation.
Palmaris Longus: Longest muscle, aids wrist flexion.
Flexor Carpi Muscles: Flex wrist.
Flexor Pollicis: Flexes the thumb.
Flexor Digitorum: Flexes digits 2-5.
Key Muscles:
Supinator: Arm supination.
Brachioradialis: Assists in elbow flexion and pronation/supination.
Extensor Carpi Muscles: Extends wrist.
Extensor Digitorum: Extends digits 2-5.
Extensor Pollicis: Extends thumb.
Muscle Overview: Listed key muscles associated with lower extremities; includes gluteal and hamstring muscles among others.
Notable Functions: Highlighted for various actions such as hip extension, abduction, and flexion.
Main Functions:
Hip extension, abduction, and lateral rotation.
Key Muscles:
Gluteus Maximus - Major hip extensor and abductor.
Gluteus Medius - Assists in hip extension and abduction.
Gluteus Minimus - Same function as Gluteus Medius.
Piriformis - Lateral rotator.
Key Muscles:
Hip Flexors: Iliacus and Psoas Major.
Hip Adductors: Adductor Magnus, Longus, Brevis, and Gracilis.
Key Muscles:
Semimembranosus
Semitendinosus
Biceps Femoris Long Head
Biceps Femoris Short Head
Functions: Hip extensors and knee flexors.
Functions:
Extends knee: Rectus Femoris, Vastus Lateralis, Vastus Intermedius, Vastus Medialis.
FLEXES knee: Sartorius, with insertion at the medial surface of proximal tibia; origin is superior iliac spine.
Functions:
Toe and foot extensors/Dorsi flexors include: Extensor Digitorum Longus, Extensor Hallucis Longus, and Tibialis Anterior.
Main Muscles:
Foot flexors/plantar flexors: Fibularis Longus, Fibularis Brevis.
Other associated muscles include Vastus Medialis, Lateral head of Gastrocnemius, Soleus.
Functions:
Foot flexors/plantar flexors: Gastrocnemius and Soleus.
Toe flexors: Tendons of Flexor Digitorum Longus and Flexor Hallucis Longus.
Function:
Toe extensors; focus on relevant functions rather than specific muscle names.
Function:
Toe flexors; focus on relevant functions rather than specific muscle names.