Muscles & Joints Anatomy Study Guide PDF

Muscles - 1. Muscles that Flex/Extend, Laterally Flex, and Rotate the Vertebral Column ​ Flexion: ○​ Rectus Abdominis Muscle ○​ External Oblique Muscle ○​ Internal Oblique Muscle ​ Extension: ○​ Erector Spinae Muscles ​ Lateral Flexion: ○​ Exte...

Muscles - 1. Muscles that Flex/Extend, Laterally Flex, and Rotate the Vertebral Column ​ Flexion: ○​ Rectus Abdominis Muscle ○​ External Oblique Muscle ○​ Internal Oblique Muscle ​ Extension: ○​ Erector Spinae Muscles ​ Lateral Flexion: ○​ External Oblique Muscle ○​ Internal Oblique Muscle ​ Rotation: ○​ External Oblique Muscle (contralateral rotation) ○​ Internal Oblique Muscle (ipsilateral rotation) 2. Primary and Accessory Muscles of Respiration ​ Primary Muscles (Responsible for normal breathing): ○​ Diaphragm Muscle ○​ External Intercostal Muscles ​ Accessory Muscles (Used during deep or forced breathing): ○​ Sternocleidomastoid Muscle ○​ Scalene Muscles ○​ Internal Intercostal Muscles ○​ Abdominal Muscles (Rectus Abdominis, External/Internal Obliques) 3. Muscles that Protract/Retract and Elevate/Depress the Scapula ​ Protraction (Move scapula forward): ○​ Serratus Anterior Muscle ○​ Pectoralis Minor Muscle ​ Retraction (Move scapula towards spine): ○​ Rhomboid Major Muscle ○​ Rhomboid Minor Muscle ○​ Trapezius Muscle (middle fibers) ​ Elevation (Lift scapula up): ○​ Trapezius Muscle (upper fibers) ○​ Levator Scapulae Muscle ​ Depression (Move scapula down): ○​ Trapezius Muscle (lower fibers) ○​ Pectoralis Minor Muscle 4. Muscles that Flex/Extend, Abduct/Adduct, Medially/Laterally Rotate the Arm at the Shoulder Joint ​ Flexion: ○​ Pectoralis Major Muscle ○​ Deltoid Muscle (anterior fibers) ​ Extension: ○​ Latissimus Dorsi Muscle ○​ Deltoid Muscle (posterior fibers) ​ Abduction: ○​ Deltoid Muscle (middle fibers) ○​ Supraspinatus Muscle ​ Adduction: ○​ Pectoralis Major Muscle ○​ Latissimus Dorsi Muscle ​ Internal Rotation: ○​ Subscapularis Muscle ○​ Latissimus Dorsi Muscle ○​ Pectoralis Major Muscle ​ External Rotation: ○​ Infraspinatus Muscle ○​ Teres Minor Muscle 5. Muscles that Flex/Extend the Forearm at the Elbow Joint ​ Flexion: ○​ Biceps Brachii Muscle ○​ Brachialis Muscle ○​ Brachioradialis Muscle ​ Extension: ○​ Triceps Brachii Muscle ○​ Anconeus Muscle 6. Muscles that Pronate/Supinate the Forearm ​ Pronation: ○​ Pronator Teres Muscle ○​ Pronator Quadratus Muscle ​ Supination: ○​ Biceps Brachii Muscle ○​ Supinator Muscle 7. Muscles that Flex/Extend, Abduct/Adduct, and Medially/Laterally Rotate the Thigh at the Hip Joint  ​ Flexion: ○​ Iliopsoas Muscle (Iliacus and Psoas Major) ○​ Rectus Femoris Muscle ○​ Sartorius Muscle ​ Extension: ○​ Gluteus Maximus Muscle ○​ Hamstrings Muscles (Biceps Femoris, Semitendinosus, Semimembranosus) ​ Abduction: ○​ Gluteus Medius Muscle ○​ Gluteus Minimus Muscle ○​ Tensor Fasciae Latae Muscle ​ Adduction: ○​ Adductor Longus Muscle ○​ Adductor Brevis Muscle ○​ Adductor Magnus Muscle ○​ Gracilis Muscle ​ Medial Rotation: ○​ Gluteus Medius Muscle ○​ Gluteus Minimus Muscle ○​ Tensor Fasciae Latae Muscle ​ Lateral Rotation: ○​ Gluteus Maximus Muscle ○​ Piriformis Muscle Note: The Iliopsoas Muscle also acts on the vertebral column by assisting with flexion. 8. Muscles that Flex/Extend, Medially Rotate the Leg at the Knee Joint ​ Flexion: penis muscle ○​ Hamstrings Muscles (Biceps Femoris, Semitendinosus, Semimembranosus) ○​ Gastrocnemius Muscle ​ Extension: ○​ Quadriceps Femoris Muscles (Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius) ​ Medial Rotation: ○​ Semitendinosus Muscle ○​ Semimembranosus Muscle ○​ Gracilis Muscle 9. Muscles that Dorsiflex/Plantar Flex the Foot at the Ankle Joint ​ Dorsiflexion (Lift foot upwards): ○​ Tibialis Anterior Muscle ○​ Extensor Digitorum Longus Muscle ○​ Extensor Hallucis Longus Muscle  ​ Plantar Flexion (Point toes downward): ○​ Gastrocnemius Muscle ○​ Soleus Muscle ○​ Plantaris Muscle ○​ Tibialis Posterior Muscle ○​ Flexor Digitorum Longus Muscle ○​ Flexor Hallucis Longus Muscle Acromioclavicular Joint - ​ Diarthrotic synovial plane joint ​ Stabilized by ligaments: 1.​ Acromioclavicular ligament (limits horizontal movement of clavicle) 2.​ Coracoclavicular ligaments (limits vertical movement of clavicle) 3.​ Coracoacromial ligament (strengthens superior capsule) ​ Mobility is limited and only allows for small controlled gliding movements Glenohumeral Joint - ​ Diarthrotic synovial ball-and-socket joint ​ Partial articular capsule is loose and only partially covers the joint to allow for the extensive range of motion needed for shoulder movements ​ Partial coverage reduces the joint's structural stability ​ The humeral head is significantly larger than the glenoid fossa, which allows for a wide range of motion in the shoulder joint (e.g., flexion, extension, abduction, adduction, rotation, and circumduction) ​ Stability: The tendon of the long head of the biceps brachii muscle attaches to the superior aspect of the glenoid fossa and crosses the shoulder joint, helping to stabilize the humeral head in the glenoid cavity during arm movements ​ High risk of dislocation ​ Glenoid Labrum is made of fibrocartilage tissue  ​ It enhances stability by deepening the glenoid cavity and providing a more secure attachment for the humeral head ​ Superior, Middle, Inferior Glenohumeral Ligaments: contribute to stability by reinforcing the capsule, particularly anteriorly and superiorly Elbow Joints - ​ Share common joint cavity, surrounded by the same articular capsule ​ Stability provided by interlocking of trochlea with trochlear notch Ulnohumeral joint ​ Diarthrotic synovial hinge joint ​ Flexion & extension, no rotation Radiohumeral joint ​ Diarthrotic synovial hinge joint ​ Flexion & extension, some rotation Proximal radioulnar joint ​ Diarthrotic synovial pivot joint ​ Annular ligament here, limits movement but allows rotation during supination and pronation Elbow Ligaments - Radial collateral ligament: stabilizes the lateral surface of the joint Annular ligament: connects head of radius to the ulna Ulnar collateral ligament: stabilizes the medial surface of the joint Radioulnar Joints - Proximal radioulnar joint ​ Diarthrotic synovial pivot joint ​ Annular ligament here, limits movement but allows rotation during supination and pronation Middle radioulnar joint ​ Amphiarthrotic fibrous syndesmosis joint ​ Interosseous membrane holds articulating surfaces together Distal radioulnar joint ​ Diarthrotic synovial pivot joint ​ Ulna is the stabilizing bone of the forearm and does not move Articular capsule (joint capsule): double layered structure that encloses the cavity of a synovial joint Function: provides stability, movement, and protection Layers: ​ Outer Fibrous layer is dense irregular CT provides strength and stability, connecting bones, inner ​ Inner Synovial Membrane is loose areolar CT, secretes synovial fluid for lubrication to reduce friction Key Anatomical Structures of the Pelvic Girdle, Pelvis, & Lower Limbs - ​ Pelvic Girdle: protects abdominopelvic organs and transmit forces between axial skeleton and lower limb ​ Articulates with the sacrum at the sacroiliac to form sacroiliac joint ​ Sacroiliac Joint: ○​ Location (Bones): Auricular surfaces of ilium and sacrum ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial: nonaxial gliding ○​ Allowed movement(s): Slight gliding movements ​ Pubic Symphysis: ○​ Location (Bones): Symphyseal surfaces of pubic bones -- the bony connection between right and left hip bones, separated by a fibrocartilage pad (pubic disc) which absorbs shock ○​ Functional Classification: Amphiarthrosis ○​ Structural Classification: Cartilaginous: symphysis ○​ Allowed movement(s): Slight movements ​ Hip Joint: ○​ Location (Bones): Head of femur and acetabulum ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial: ball-and-socket ○​ Allowed movement(s): Flexion–extension, abduction–adduction, circumduction, lateral–medial rotation  ○​ Stability is enhanced by the deep acetabulum, labrum, and strong ligaments (e.g., iliofemoral, ischiofemoral, pubofemoral) ○​ Mobility is limited ​ Knee Joint: ○​ Location (Bones): Medial and lateral condyles of femur and tibia; patella and patellar surface of femur ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial biaxial hinge ○​ Allowed movement(s): Flexion–extension, slight lateral–medial rotation ○​ Stabilizing tissues: medial and lateral menisci, ACL, PCL, and collateral ligaments ○​ ***Knee joint is less stable than the hip due to its high mobility, dependence on ligaments that are prone to injury, and lack of bony reinforcement ○​ ***6 muscles that cross the knee: vastus muscles, rectus femoris, bicep femoris, gastrocnemius muscle ​ Patellofemoral Joint: ○​ Location: Between the posterior surface of the patella and the patellar surface of the femur ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial, nonaxial gliding joint ○​ Allowed Movements: Nonaxial gliding of the patella within the femoral groove during knee flexion and extension Ligaments of knee - ​ Lateral and Medial collateral ligaments ​ Ligaments are tightest when knee is in extension ​ Lateral collateral resists varus force < > ​ Prevents lateral displacement ​ Medial collateral resists valgus force > < ​ Prevents medial displacement ​ Anterior and posterior cruciate ligaments ​ ACL tightens when knee is in extension, prevents hyperextension ​ PCL tightens when knee is in flexion, prevents hyperflexion ​ Proximal Tibiofibular Joint: ○​ Location (Bones): Tibial lateral condyle and fibular head ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial: nonaxial gliding ○​ Allowed movement(s): Slight gliding movements  ​ Distal Tibiofibular Joint: ○​ Location (Bones): Distal tibia and distal fibula ○​ Functional Classification: Amphiarthrosis ○​ Structural Classification: Fibrous: syndesmosis ○​ Allowed movement(s): Slight movements Joints of the Lower Limb (Ankle/Foot) - ​ Distal Tibiofibular Joint ○​ Location (Bones): Distal tibia and distal fibula ○​ Functional Classification: Amphiarthrosis ○​ Structural Classification: Fibrous: syndesmosis ○​ Allowed movement(s): Slight movements ​ Talocrural (Ankle) Joint ○​ Location (Bones): Medial malleolus, distal tibia, and talus; lateral malleolus and talus ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial: biaxial hinge ○​ Allowed movement(s): Plantarflexion–dorsiflexion ​ Subtalar Joint ○​ Location (Bones): Talus and calcaneus ○​ Functional Classification: Diarthrosis ○​ Structural Classification: Synovial: nonaxial gliding ○​ Allowed movement(s): Inversion–eversion Ligaments of the Ankle - ​ Anterior and Posterior Tibiofibular ligaments ​ Primarily stabilizes tibia and fibula at ankle joint ​ Lateral ligaments (anterior and posterior talofibular ligaments) ​ Most commonly sprained ​ Resists inversion and limits displacement of talus ​ Deltoid ligaments ​ Stabilizes ankle during eversion and prevents dislocation ​ Reinforces medial aspects of ankle ​ Superficial and deep layer Glenohumeral VS Hip Joint Stability - ​ Hip Joint: ○​ Highly stable due to deep acetabulum and the presence of the acetabular labrum ○​ Strong supporting ligaments (e.g., iliofemoral, ischiofemoral, pubofemoral ligaments) and surrounding muscles ○​ Designed to bear weight and resist forces during movement and standing ​ Glenohumeral Joint (Shoulder Joint): ○​ Less stable due to the shallow glenoid fossa and smaller glenoid labrum ○​ Relies heavily on surrounding muscles (e.g., rotator cuff) and ligaments for stabilization ○​ Prone to dislocation due to reduced structural support and high mobility Glenohumeral VS Hip Joint Mobility - ​ Hip Joint: ○​ Moderately mobile but more limited than the shoulder ○​ Allows flexion-extension, abduction-adduction, circumduction, and medial-lateral rotation ○​ Designed for weight-bearing movements while maintaining stability ​ Glenohumeral Joint (Shoulder Joint): ○​ Extremely mobile, offering a greater range of motion than the hip ○​ Allows flexion-extension, abduction-adduction, circumduction, and medial-lateral rotation ○​ Sacrifices stability for mobility, making it more prone to injury