Muscles, Bones, Joints & Movement Study Guide

Key Anatomical and Skeletal Terms

• Muscle: Specialized tissue that contracts to produce force, enabling the body to move.

• Bone: Rigid, calcified hard tissue that provides structural support to the body, protects internal organs, and facilitates movement by serving as levers.

• Joint: An anatomical junction where two or more bones meet and articulate.

• Axial Skeleton: The foundational central core of the skeletal framework, consisting of:

  • Skull: Cranial and facial bones protecting the brain and supporting sensory structures.

  • Spine (Vertebral Column): Articulated column providing axial support and protecting the spinal cord.

  • Ribs: Protective cage enclosing vital thoracic structures.

  • Sternum: Central anterior chest bone anchoring the thoracic cage.

• Appendicular Skeleton: The bones comprising the upper and lower extremities and their supporting girdles, including:

  • Upper extremities: Arms, forearms, wrists, and hands.

  • Lower extremities: Thighs, legs, ankles, and feet.

  • Shoulder girdle: Clavicle and scapula.

  • Hip girdle: Pelvis.

• Ligament: Tough, fibrous band of connective tissue that connects bone to bone, serving specifically to stabilize joints and restrict abnormal movement.

• Tendon: Inflexible, high-tensile fibrous connective tissue band that connects muscle to bone, transmitting contractile force to facilitate body movement.

• Cartilage: Smooth, resilient connective tissue lining articular surfaces that reduces friction between adjacent bones and absorbs mechanical shock.

Skeletal Divisions and Major Bones

• Cranial and Facial Bones:

  • Skull: Superior skeletal enclosure that protects the brain and houses specialized sensory organs.

  • Mandible: The lower jawbone, providing structural attachment for lower dentition and enabling mastication.

• Thoracic Cage:

  • Sternum: Flat bone located anteriorly at the center of the chest, articulating with the costal cartilages of the ribs and the clavicle.

  • Ribs: Curved, paired bilateral bones extending from the thoracic vertebrae to encase the cardiopulmonary organs.

• Vertebral Column (Spine): Segmented axial structure composed of distinct regions with specific bone counts:

  • Cervical Vertebrae: Superior section supporting the head and neck, comprising $7$ individual vertebrae.

  • Thoracic Vertebrae: Intermediate section articulating with the ribs, comprising $12$ individual vertebrae.

  • Lumbar Vertebrae: Robust lower-back section bearing axial weight, comprising $5$ individual vertebrae.

• Upper Extremities and Shoulder Girdle:

  • Clavicle: Anterior collarbone connecting the sternum to the shoulder girdle.

  • Humerus: Long bone of the brachium (upper arm).

  • Radius: Lateral long bone of the antebrachium (forearm), located on the thumb side.

  • Ulna: Medial long bone of the antebrachium (forearm), running parallel to the radius on the pinky-finger side.

  • Carpals: Cluster of small, gliding bones forming the wrist complex.

  • Metacarpals: Intermediate bones forming the palm and structural framework of the hand.

  • Phalanges (Hand): Articulated bones forming the individual fingers and thumb.

• Pelvic Girdle and Lower Extremities:

  • Pelvis (Hip Bone): Sturdy basin-shaped complex of fused bones transferring weight from the axial skeleton to the lower limbs.

  • Femur: Longest and strongest bone in the human body, situated in the thigh.

  • Patella: Sesamoid bone (kneecap) articulating with the anterior surface of the distal femur.

  • Tibia: Larger, medial weight-bearing bone of the lower leg (shin bone).

  • Fibula: Slender, lateral stabilizing bone of the lower leg running parallel to the tibia.

  • Tarsals: Group of irregular bones forming the ankle and rearfoot.

  • Metatarsals: Elongated bones comprising the midfoot and forefoot arches.

  • Phalanges (Foot): Articulated bones forming the individual toes.

Muscular Anatomy: Major Muscles, Locations, and Functions

• Anterior Muscles (Front View):

  • Deltoid:

  • Location: Shoulder region.

  • Function: Primary abductor of the arm; assists in shoulder flexion and rotation.

  • Pectoralis Major:

  • Location: Chest (anterior thoracic wall).

  • Function: Adduction, medial rotation, and horizontal flexion of the humerus across the chest.

  • Biceps Brachii:

  • Location: Front of the upper arm (anterior compartment of brachium).

  • Function: Flexes the elbow joint and acts as a powerful supinator of the forearm.

  • Flexors:

  • Location: Anterior compartment of the forearm.

  • Function: Flexes the wrist, hand, and fingers.

  • Abdominals:

  • Location: Core (anterior abdominal wall).

  • Function: Trunk flexion, compression of abdominal viscera, and postural stabilization.

  • Adductors:

  • Location: Inner thigh (medial compartment of the thigh).

  • Function: Adducts the femur, pulling the lower limb inward toward the body's midline.

  • Quadriceps:

  • Location: Front thigh (anterior compartment of the thigh).

  • Function: Powerful extensor of the knee joint; assists in hip flexion.

  • Tibialis Anterior:

  • Location: Front of the shin (anterior compartment of the lower leg).

  • Function: Primary dorsiflexor of the foot; lifts toes and foot toward the shin.

• Posterior Muscles (Back View):

  • Trapezius:

  • Location: Upper back and neck.

  • Function: Elevates, retracts, depresses, and stabilizes the scapula; supports neck extension.

  • Latissimus Dorsi:

  • Location: Middle and lower back.

  • Function: Broad back muscle that extends, adducts, and medially rotates the arm.

  • Triceps Brachii:

  • Location: Back of the upper arm (posterior compartment of brachium).

  • Function: Primary extensor of the elbow joint.

  • Gluteus Maximus:

  • Location: Buttocks.

  • Function: Primary extensor and external rotator of the hip joint; vital for standing, climbing, and propulsion.

  • Hamstrings:

  • Location: Back of the thigh (posterior compartment of the thigh).

  • Function: Flexes the knee joint and extends the hip joint.

  • Gastrocnemius:

  • Location: Calf (posterior compartment of the lower leg).

  • Function: Plantarflexes the foot at the ankle joint; assists in knee flexion.

Joint Types, Articulations, and Functional Examples

• Ball-and-Socket Joint:

  • Functional Movement: Multi-axial articulation capable of movement in all directions, including flexion, extension, abduction, adduction, rotation, and circumduction.

  • Anatomical Examples: Shoulder joint (glenohumeral joint) and Hip joint (iliofemoral joint).

• Hinge Joint:

  • Functional Movement: Uniaxial back-and-forth movement restricted entirely to a single plane, specifically flexion and extension.

  • Anatomical Examples: Elbow joint (humeroulnar joint) and Knee joint (tibiofemoral joint).

• Pivot Joint:

  • Functional Movement: Uniaxial rotation (turning) of a bone around its longitudinal axis.

  • Anatomical Examples: Neck articulation between the atlas and axis vertebrae ($C_1$ and $C_2$).

• Saddle Joint:

  • Functional Movement: Biaxial articulation allowing movement in two perpendicular planes: flexion, extension, abduction, and adduction.

  • Anatomical Examples: Carpometacarpal joint of the Thumb.

• Gliding Joint:

  • Functional Movement: Non-axial sliding or slipping motions involving minimal, small displacement between flat bone surfaces.

  • Anatomical Examples: Intercarpal joints of the Wrist and Intertarsal joints of the Ankle.

• Immovable Joint (Suture):

  • Functional Movement: Synarthrodial joint with no movement permitted between adjacent bones, bonded by dense fibrous tissue.

  • Anatomical Examples: Cranial sutures of the Skull.

• Partially Moveable Joint:

  • Functional Movement: Amphiarthrodial joint permitting limited, restricted movement while offering high structural stability and shock absorption.

  • Anatomical Examples: Cartilaginous joints located between adjacent vertebrae of the spine.

Types of Anatomical Movement

• Flexion:

  • Definition: A joint action that decreases the angle between articulating bones (bending).

  • Anatomical Example: Bending the elbow joint, bringing the forearm toward the upper arm.

• Extension:

  • Definition: A joint action that increases the angle between articulating bones (straightening).

  • Anatomical Example: Straightening the elbow joint back to an anatomical resting alignment.

• Abduction:

  • Definition: A lateral movement that moves an anatomical structure away from the midline of the body.

  • Anatomical Example: Raising the arms laterally out to the sides.

• Adduction:

  • Definition: A medial movement that moves an anatomical structure toward the midline of the body.

  • Anatomical Example: Lowering the arms from an outstretched lateral position back to your side.

• Rotation:

  • Definition: The turning or pivoting of an anatomical structure around a bone's longitudinal axis.

  • Anatomical Example: Turning the head left or right at the atlantoaxial neck junction.

• Circumduction:

  • Definition: A complex, multi-planar circular movement that sequentially combines flexion, extension, abduction, and adduction, tracing a conical path in space.

  • Anatomical Example: Making a continuous circular movement with your entire arm at the shoulder joint.

• Pronation:

  • Definition: Rotational movement of the forearm that turns the palm down (facing posteriorly or toward the floor).

  • Anatomical Example: Turning your palm downward from an anterior or upward orientation.

• Supination:

  • Definition: Rotational movement of the forearm that turns the palm up (facing anteriorly or toward the ceiling).

  • Anatomical Example: Turning your palm upward from a downward orientation.

• Dorsiflexion:

  • Definition: Specialized ankle movement that lifts the foot and toes upward toward the anterior shin.

  • Anatomical Example: Pulling your toes and foot up off the ground toward the lower leg.

• Plantarflexion:

  • Definition: Specialized ankle movement that depresses or points the foot and toes downward away from the shin.

  • Anatomical Example: Pointing your toes downward toward the ground (as in standing on tiptoes).

Anatomical Positions and Directional Terminology

• Anterior (Front):

  • Definition: Toward the front of the body.

  • Structural Reference: The sternum, quadriceps, and abdominal wall are anterior structures.

• Posterior (Back):

  • Definition: Toward the back of the body.

  • Structural Reference: The spine, hamstrings, and latissimus dorsi are posterior structures.

• Superior (Above):

  • Definition: Above; situated closer to the head or upper part of a structure.

  • Structural Reference: The skull is superior to the sternum.

• Inferior (Below):

  • Definition: Below; situated closer to the feet or lower part of a structure.

  • Structural Reference: The pelvis is inferior to the thoracic cage.

• Medial:

  • Definition: Toward the midline (center line) of the body.

  • Structural Reference: The sternum is medial relative to the shoulders; adductors pull toward the medial line.

• Lateral:

  • Definition: Away from the midline of the body; situated toward the outer sides.

  • Structural Reference: The arms are positioned lateral to the torso.

• Proximal:

  • Definition: Closer to the point of attachment of a limb to the body trunk.

  • Structural Reference: The femur is proximal to the tibia; the humerus is proximal to the radius.

• Distal:

  • Definition: Farther from the point of attachment of a limb to the body trunk.

  • Structural Reference: The phalanges are distal to the carpals and tarsals.

• Superficial:

  • Definition: Closer to the external surface of the body (outer).

  • Structural Reference: Skin and superficial fascia lie outer to skeletal muscle.

• Deep:

  • Definition: Farther away from the external surface of the body (inner).

  • Structural Reference: Bones and internal visceral organs lie deep relative to overlying musculature.