Anatomy: LE 1 | TRANS 1 Fascia and Muscle Compartments of the Upper Limbs PDF

ANATOMY: LE 1 | TRANS 1 Fascia and Muscle Compartments of the Upper Limbs Dr. Zorba Bnn R. Bautista | August 13, 2019 OUTLINE B. ANATOMIC...

ANATOMY: LE 1 | TRANS 1 Fascia and Muscle Compartments of the Upper Limbs Dr. Zorba Bnn R. Bautista | August 13, 2019 OUTLINE B. ANATOMICAL PLANES I. Review: General Anatomic II. Fascia and Muscle Median plane (median sagittal plane) Terms Compartments of the Upper → Divides body longitudinally into equal right and left halves A. Anatomical Position Limbs → Defines the midline of the head, neck, and trunk where it B. Anatomical Planes A. Bones and Joints of intersects the surface of the body C. Anatomical Terms Upper Limbs Sagittal plane Based on Laterality B. Deep Fasciae of → Parallel to the median plane D. Bones Upper Limbs Frontal (coronal) plane E. Joints C. Pectoral Region → Vertical planes passing through the body at right angles to F. Types of Muscles D. Muscles of the Arm the median plane, dividing body into anterior (front) and E. Muscles of the posterior (back) portions Forearm Transverse plane F. Muscles of the Hand → Horizontal plane passing through the body at right angles to III. Review Questions the median and frontal planes, dividing body into superior IV. References (upper) and inferior (lower) parts OBJECTIVES At the end of the lecture, students shall be able to: 1. Describe the anatomical position. 2. Define anatomical planes, and terms of relationship, laterality and movement. 3. Give the functions of bones. 4. Classify of bones. 5. Define the bone markings. 6. Classify muscles as to form and function. 7. Differentiate reflexive, tonic and phasic muscle contraction. 8. Differentiate regional, systemic and clinical anatomy. 9. Identify & Classify the bones and joints of the upper limb 10. Describe the deep fascia of the UL and its subsequent functional compartmentalization of the muscle groups. Figure 2. Anatomical Planes 11. Describe the fascial spaces: axilla, cubital fossa, and [Moore] those in the hand and enumerating their contents. Sections 12. Describe the muscles of the pectoral girdle conceived as The main use of anatomical planes is to describe sections an anatomical group / functional group and stating their → Longitudinal sections functions. ▪ Run lengthwise or parallel to the long axis of the body or 13. Identify the main muscles of the UL conceived as of any of its parts functional groups in each region with respect to the → Transverse sections (cross sections) principal joint movements rather than as individual ▪ Cut at right angles to the longitudinal axis of the body muscles. → Oblique sections 14. Identify the principal attachments of the muscle groups ▪ Slices of the body not cut along the previously listed and the joints upon which they act. anatomical planes I. REVIEW: GENERAL ANATOMIC TERMS C. ANATOMICAL TERMS BASED ON LATERALITY Regional Systemic Clinical Terms of Laterality Topographical; Study of the body’s Applied anatomy; Table 1. Anatomical Terms Based on Laterality organization of organ systems that emphasizes aspects Term Definition Example human body as work together to carry of bodily structure Bilateral Seen on both sides Kidneys major parts or out complex functions and function Unilateral Seen on one side only Spleen segment important in the Ipsilateral Seen on the same side of Right thumb and practice of medicine; the body right big toe incorporates region Contralateral Seen on the opposite side Right hand and and systemic of the body left hand A. ANATOMICAL POSITION Terms of Relationships Point of Reference Describe the position of one structure relative to another → Body is standing upright Table 2. Anatomical Terms Based on Relationships → Head, eyes, and toes directed forward (anteriorly) Term Definition → Arms at the side with palms facing forward (anteriorly) Anterior (ventral) Nearer the front → Lower limbs close together with the feet parallel Rostral Nearer the front, used when describing parts of the brain Posterior (dorsal) Nearer the back Dorsum Any superior aspect that protrudes anteriorly from the body (ex. tongue, nose, penis, posterior surface of the hand or foot) Superior (cranial) Upward or nearer the head Inferior (caudal) Downward or nearer the feet Figure 1. Anatomical Position [2022B Trans] LE 1 Trans 1 Group D: Olegario, Ong, Pacete, Pacheco, Padre TE: Sarte,Tagle VPAA: Vedan 1 of 20 Medial Toward the midline or median plane Lateral Farther from the midline or median plane Proximal Near from a reference point Distal Away from a reference point Superficial Closer to the surface Deep Farther from the surface External Outside or farther from the center of an organ or cavity Internal Inside or closer to the center, independent of direction Terms of Movement Ordinary Movements → Movements that occur in sagittal planes around transverse axis (SX –Sagittal plane around X-axis) ▪ Flexion – bending or decreasing the joint angle, occur in the ▪ Extension – straightening or increasing the joint angle Figure 5. Movements in the Forearm and Hand [Moore] ▪ Dorsiflexion – flexion at the angle joint ▪ Plantarflexion – bends the foot and toes toward the ground ▪ Abduction-adduction of the thumb– occurs at sagittal plane → Movements that occur in frontal plane around an anteroposterior axis (FZ-Frontal plane around Z-axis) ▪ Abduction – moving away from the median plane; for digits, defined as spreading apart ▪ Adduction – moving toward the median plane ▪ Flexion-extension of the thumb – occurs at frontal plane → Circumduction – circular movement that involves sequential flexion, abduction, extension, and adduction (ex. shoulder Figure 6. Movements in the Foot and Ankle [Moore] and hip joints) Other movements → Movements that revolve around its longitudinal axis (TY- → Opposition – movement by which the pad of the 1st digit Transverse plane around Y-axis) ▪ Medial Rotation (Internal Rotation) – brings the anterior (thumb) is brought to another digit pad surface of a limb closer to the median plane → Reposition – movement of the 1st digit from opposition back ▪ Lateral Rotation (External Rotation) – takes the anterior to its anatomical position surface away from the median plane → Protrusion – forward movement as in protruding the ▪ Pronation – rotates the radius medially so that the palm mandible (chin), lips, or tongue of the head faces posteriorly and its dorsum faces → Retrusion – backward movement, as in retruding the anteriorly mandible, lips, or tongue ▪ Supination – rotates the radius laterally and uncrossing it → Protraction – anterolateral movement of the scapula on the from the ulna, returning the pronated forearm to the thoracic wall, moving the shoulder region anteriorly anatomical position → Retraction – posteromedial movement of the scapula on the ▪ Eversion – moves the sole of the foot away from the thoracic wall, moving the shoulder region posteriorly median plane → Elevation – raises or moves a part superiorly, as in raising ▪ Inversion – moves the sole of the foot toward the median the shoulders when shrugging plane → Depression – lowers or moves a part inferiorly, as in depression of the shoulders when standing at ease Figure 4. Different Types of Ordinary Movements [Moore] Figure 7. Other Movements [Moore] D. BONES Highly specialized, hard form of connective tissue that makes up most of the skeleton ANA Fascia and Muscle Compartments of the Upper Limbs 2 of 19  Importance: Table 3. Types of Bones Markings → Support for the body and its vital cavities Term Description Example → Protection for vital structures Capitulum small, round, → Mechanical basis for movement articular head → Storage for salts → Continuous supply of new blood cells Classification of Bones According to Function → Axial Skeleton Capitulum of the humerus ▪ Comprises of 80 bones ▪ Consists of the bones of the head (cranium or skull), neck Condyle rounded, (hyoid bone and cervical vertebrae), and trunk (ribs, knuckle-like sternum, vertebrae), and trunk (ribs, sternum, vertebrae, articular area, and sacrum). often occurring in → Appendicular pairs ▪ Bones of Extremities ▪ Comprises of 126 bones ▪ Consists of the bones of the limbs, including those forming the pectoral (shoulder) and pelvic girdles. Table 1. Characteristics of Compact and Spongy Bones lateral and medial femoral Compact Spongy condyles provides strength for Branching network of Crest ridge of bone the iliac crest weight bearing trabeculae compact bone is greatest Resist stresses and near the middle of the strains shaft where the bones Usually short bones are liable to buckle (In long bones) All bones have a superficial thin layer of compact bone around a central mass of spongy bone, except where the latter is replaced by a medullary (marrow) cavity Epicondyle eminence lateral epicondyle of the According to Shape superior or humerus Table 2. Types of Bones According to Shape adjacent to a Type Description Example condyle Long bone Designed for Humerus, femur rigidity For attachment of muscles and ligaments Have elevations that serve as Facet smooth flat superior costal facet on the supports where area, usually body of a vertebra for large muscles covered with articulation with a rib attach cartilage, Tubular in shape where a bone Short bone Cuboidal in Tarsus (ankle), articulates shape carpus (wrist) with another bone Flat bone Protective Flat bones of the functions cranium protect the brain Irregular bone Various shapes Bones of the face Sesamoid bone Develop in Patella or knee cap Foramen passage obturator foramen certain tendons through a and are found bone where tendons cross the ends of long bones in limbs Fossa hollow or infraspinous fossa of the Protects the depressed scapula tendons from area excessive wear Bone Markings → Appear wherever tendons, ligaments, and fascias are attached or where arteries lie adjacent to or enter bones → Occurs in relation to passage of a tendon, cr control a type of movement occurring at a joint ANA Fascia and Muscle Compartments of the Upper Limbs 3 of 19 Groove elongated radial groove of the humerus Trochlea spool-like trochlea of the humerus depression or articular furrow process or Head large, round process that articular end acts as a pulley Tubercle small raised greater tubercle of the eminence humerus head of the humerus Line linear soleal line of the tibia elevation, sometimes called a ridge Tuberosity large rounded ischial tuberosity elevation Malleolus rounded lateral malleolus of the fibula process E. JOINTS Unions or junctions between 2 or more bones that makes movement possible Has a rich nerve supply Notch indentation at greater sciatic notch the edge of a Classification of Joints bone Fibrous Joint → United by fibrous tissues → Amount of movement made depends on the fibers uniting the articulating bones → Types: ▪ Syndesmosis − Joins the bones together with a sheet of fibrous tissue, either a ligament or fibrous membrane. ▪ Gomphosis (or Dento-alveolar syndesmosis) − Peg-like process (a tooth) fits into the socket Protuberance a bulge or external articulation between the root of the tooth and the projection of occipital alveolar process of the jaw. bone protuberance Cartilaginous Joint → United by hyaline cartilages or fibrocartilages → Types: ▪ Primary Cartilaginous Joint or Synchondroses − Connected by hyaline cartilages − Permits slight bending during early life Spine thorn-like the spine of the scapula − Temporary unions, present during the development of process long bones − Found in epiphyseal plates in long bones ▪ Secondary Cartilaginous Joint or Symphyses − Slightly movable joints united by fibrocartilages − Found in intervertebral discs Synovial Joint → Most common type of joint → Joints of locomotion and as such, allow free movement. → Components of a synovial joint: ▪ Joint cavity Trochanter large blunt greater trochanter of the − Space between the articulating bones elevation femur ▪ Synovial fluid − Viscous and slippery textured fluid that fills the joint cavity. It serves to nourish the articular cartilages, remove their wastes, and as lubricant for joint surfaces. ▪ Meniscus − Fibrocartilaginous articular disc which forms a gap between articulating bones, helping in shock absorption and force distribution ANA Fascia and Muscle Compartments of the Upper Limbs 4 of 19  ▪ Accessory ligaments and tendons − Support the area of articulation; either separate (extrinsic) or a thickening of a portion of the joint capsule (intrinsic) → Types of Synovial Joints According to type of movement permitted: ▪ Ball and Socket (or Spheroidal) joint − Multi-axial joints that allow movement on multiple axes and planes: flexion-extension, abduction-adduction, medial and lateral rotation, and circumduction. − Highly mobile, the “ball-like” surface of one bone fits into the socket of another bone. − e.g. hip joint ▪ Hinge (or Ginglymus) joint − Uniaxial joint that permits flexion and extension. − Movement occurs on the sagittal plane along a transverse axis. − e.g. elbow joint ▪ Saddle (or Sellar) joint − Bi-axial joints that permit movement in two planes: sagittal and frontal. − The opposing articular surfaces are reciprocally convex and concave, thus the name “Saddle joint”. − e.g. carpometacarpal joint at the base of the thumb. ▪ Condyloid (Ellipsoidal) joint − Bi-axial joints that permit flexion and extension, as well as abduction and adduction. Figure 8. Types of Joints in the Body − Movement in sagittal plane is usually greater. [Moore’s] − Circumduction is possible, but to a lesser extent than in F. MUSCULAR SYSTEM the saddle joint. Consists of about 600 muscles. ▪ Pivot (or Trochoid) joint Myology: study of muscles − Rotates around a central axis, and so are uniaxial. Functions: Movement, Stability, Communication, Control of − In these joints, a rounded process of bone rotates body openings & passages and Heat production. within a ring or sleeve. − e.g. radius and ulna General Anatomy of Muscles ▪ Plane (or Gliding) joint ORIGIN - the attachment site that doesn't move during − Permits gliding/sliding movements across the plane of contraction. articulation, and is usually uniaxial. INSERTION - the attachment site that does move when the − e.g. scapula and the clavicle muscle contracts. ACTION - movement of a muscle, can be described relative to Examples of Joints and Their Locations the joint or the body part moved. Sternoclavicular: Sellar/saddle joint (the only bony connection INNERVATION - "to supply nerves to." It also means "to between trunk and upper limb) stimulate" or "to supply with energy." Acromioclavicular: plane joint BELLY: part where you cut in dissection. Shoulder (glenohumeral): ball and socket TENDON: what the fascia becomes when attached to the bone Elbow: hinge joint Types of Muscles Radioulnar (proximal and distal): pivot joints Described on their characteristics relating to: Wrist: condylar joints → Voluntary vs Involuntary Intercarpal: plane or gliding joints → Somatic vs Visceral Carpometacarpal: plane joints → Striated vs Smooth vs Unstriated 1st Carpometacarpal (thumb): saddle joint Types: Intermetacarpal: plane joints → Skeletal striated muscle Metacarpophalangeal: condylar joints ▪ Voluntary, somatic muscle, multi-striated, with nucleus at Interphalangeal: hinge joint the periphery. Hip joint: ball and socket ▪ Makes up the gross skeletal muscles that compose the Knee joint: hinge joint (femoropatellar and two tibiofemoral muscular system, moving or stabilizing bones and other joints) structure (i.e. biceps brachii). Tibiofibular joint: plane joint → Cardiac striated muscle ▪ Involuntary, visceral muscle striated with intercalated discs, nucleus at the center. ▪ It forms the wall of the heart (myocardium) and the adjacent parts of the great vessels (aorta) and pumps blood. → Smooth (unstriated) muscle ▪ Involuntary, visceral muscle, unstriated, nucleus at the center, fusiform or spindle shaped. ▪ Forms walls of most vessels and hollow organs. ▪ Moving through pulsation/contraction (i.e. stomach, uterus) ANA Fascia and Muscle Compartments of the Upper Limbs 5 of 19 Shapes of Skeletal Muscles Types of Muscle Contractions Flat Reflexive – automatic; ex. diaphragm → Has parallel fibers often with aponeurosis. Tonic → Formed by muscle fibers that lie parallel to each other. → When muscles are “relaxed”, the muscles are almost → i.e. sartorius muscle (narrow flat); external oblique (broad always contracted flat) → Contributes to firmness and stability of muscle, Fusiform maintenance of posture → Has muscle belly fibers are arranged parallel to each other Phasic – voluntary → Spindle shaped and has thick bellies and tapered ends Coordinated Actions of Muscle Groups → i.e. biceps brachii Prime Mover Convergent → Primary muscles involved in the activation of many of the → Has a widespread expansion over a sizable area, but then major joints within the body. the fascicles come to a single, common attachment point. → Contracts concentrically to produce the desired movement, → i.e. pectoralis major doing most of the work required. Quadrate Antagonist → Stabilizers along with whatever other function they perform. → Often occur in pairs, called antagonistic pairs. → Has 4 sides → As one muscle contracts, the other relaxes. → i.e. rectus abdominis → Contracts eccentrically, relaxing progressively to produce Circular or sphincteral smooth movement. → Surrounds a body opening or orifice and constricting it when Synergist contracted. → The muscle that complements the prime mover. → i.e. orbicularis oculi → perform, or help perform, the same set of joint motion as the Multi-headed agonists → Has more than one head or attachment or more than one → Synergists muscles act on movable joints contractile belly, respectively. Fixator → i.e. triceps brachii → is one that serves as a stabilizer of one part of the body Pennate during movement of another part. → Fascicles attach obliquely (in a slanting position) to its → It allows the agonist muscle to work effectively by stabilizing tendon. the origin of the agonist muscle. → Allow higher force production but smaller range of motion Example: for elbow flexion When a muscle contracts and shortens, the pennation angle Prime mover: brachialis (prime movement is to flex the elbow) increases. Synergist: biceps brachii (also helps in flexing the elbow) → Muscle fibers are in feather-like arrangement. Antagonist: triceps brachii (will elongate to accommodate ▪ Unipennate (i.e. extensor digitorum longus) flexion of elbow) ▪ Bipennate (i.e. rectus femoris) Fixators: shoulder and scapular stabilizers (to inhibit ▪ Multipennate (i.e. deltoids) movement of the shoulder while undergoing elbow flexion) Naming Muscles Table 1. Basis of Naming Muscles Intrinsic and Extrinsic Muscles Intrinsic → Origin and insertion in the same region. → i.e. hand muscles such as lumbricals Extrinsic → Acts upon designated region but has its origin elsewhere. → i.e. forearm muscles acting on the fingers (the flexor digitorum superficialis and profundus, the extensor digitorum muscles) II. FASCIA AND MUSCLE COMPARTMENTS OF THE UPPER LIMBS Figure 9. Shapes of Skeletal Muscles [Moore’s] A. BONES AND JOINTS OF UPPER LIMBS Axial Types of Phasic Muscle Contractions → Central supporting axis Isotonic – change in muscle length → Total= 80 bones → Concentric – muscle shortening ▪ Skull= 22 + 6 bones → Eccentric – muscle lengthening ▪ Vertebral column= 26 bones Isometric – muscle length stays the same, but force is ▪ Thoracic cage= 25 bones increased above tonic levels to resist gravity or other ▪ Hyoid= 1bone antagonistic force Appendicular ANA Fascia and Muscle Compartments of the Upper Limbs 6 of 19  → Bones of extremities o Dense connective tissue → Total= 126 bones ▪ Sub-categories ▪ Pectoral girdle= 4 bones − Brachial Fascia ▪ Pelvic girdle= 2 bones o Encloses arm deep to the skin and subcutaneous ▪ Attached limbs tissue − Upper Limbs= 60 bones o Attached inferiorly to the epicondyles of the humerus − Lower Limbs= 60 bones and the olecranon of the ulna → Sternoclavicular joint-only bone to bone joint (connection) of − Antebrachial Fascia the shoulder complex to the thorax. o Deep fascia of the forearm o Surrounds the structures of the free upper limb Upper Limb Parts − Deltoid 32 bones per side o Descends over the superficial surface of the deltoid Segments of the Upper Limb: from the clavicle, acromion, and scapular spine. → Shoulder − Pectoral Fascia → Arm o Invests the pectoralis major and is continuous → Forearm inferiorly with the fascia of the anterior abdominal → Hand wall. Joints: − Axillary Fascia → Acromioclavicular joint o Forms floor of the axilla → Glenohumeral (shoulder) joint Investing layer-septae that surrounds the whole neck muscles → Elbow joint (lateral and medial) → Proximal radio-ulnar joint Intermuscular septae and humerus divide the space inside → Distal radio-ulnar joint brachial fascia into anterior and posterior compartments → Wrist (radio-carpal joint) Interosseous membrane and the radius and ulna divide the → Midcarpal joint space inside antebrachial fascia into anterior and posterior → Carpo-metacarpal joint compartments → Metacarpo-phalangeal joints Compartments of the Palm → Interphalangeal joint Hypothenar Compartment Thenar Compartment Central Compartment Adductor Compartment Interosseous Compartment Figure 11. Compartments of the Palm [Moore’s] C. PECTORAL REGION Anterior Axioappendicular Muscles 1. Pectoralis Major Figure 10. Bones and Joints of the Upper Limbs [Moore’s] B. DEEP FASCIAE OF UPPER LIMBS Types of Muscles Fasciae → Wrapping, packaging and insulating materials of the deep Figure 3.A Anterior Axioappendicular Muscles [Moore’s] structures ▪ Types of Fascia Acts on upper limbs − Superficial → Literal Translation: Greater breast muscle o Subcutaneous tissue → Most superficial muscle in the pectoral region. o Loose connective tissue with fat deposit → Large, fan-shaped muscle that covers the superior part of − Deep the thorax. o Named according to area covered → Composed of a sternocostal heads and a clavicular head ANA Fascia and Muscle Compartments of the Upper Limbs 7 of 19  ▪ Sternocostal heads are much larger. Its lateral borders Elevates the glenoid cavity for the arm to be raised above the form the muscular mass of the anterior wall of the shoulder. axilla. (FECS- Flexion Clavicular head, Extension Anchors the scapula. Enabling other muscles to use it as a Sternocostal head) fixed bone for movements of the humerus. → Winging of scapula - paralysis of serratus anterior / injury to long thoracic nerve. → (SMB- Serratus Ant, Medial Winging, Open Book deformity) Figure 3.B Pectoralis Major [Moore’s] 2. Pectoralis Minor Acts on upper limbs → Literal Translation: Lesser breast muscle Figure 6. Serratus Anterior [Moore’s] → A thin, flat muscle found immediately underneath the Posterior Axioappendicular Muscles pectoralis major. 1. Superficial Layer → Serves as landmark for axilla structures like brachial Acts on upper limbs plexus and axillary artery. → Trapezius ▪ Literal Translation: Four-sided muscle ▪ a large muscle bundle that extends from the back of your head and neck to your shoulder. ▪ Attaches pectoral girdle directly to the trunk. ▪ Attaches the pectoral girdle to the cranium and vertebral column. ▪ Assists in suspending the upper limb. Figure 4. Pectoralis Minor [Moore’s] 3. Subclavius Acts on upper limbs → Literal Translation: Muscle under the clavicle. → A small triangular muscle placed between the clavicle and the first rib. → Found along the Pectoralis major and Pectoralis minor. → Makes up the anterior wall of the axilla. → Helps resist the tendency of the clavicle to dislocate at the sternoclavicular (SC) joint. Figure 7.A Trapezius [Moore’s] → Latissimus dorsi ▪ Literal Translation: Widest back muscle ▪ Widest muscle of the back. ▪ With the pectoralis major, it is a powerful adductor of the humerus. ▪ Has a main role with the downward rotation of the scapula. ▪ Useful in restoring the upper limb from abduction superior to the shoulder Figure 5. Subclavius [Moore’s] 4. Serratus Anterior Literal Translation: Saw-like anterior muscle Inferior part of the serratus anterior rotates the scapula ANA Fascia and Muscle Compartments of the Upper Limbs 8 of 19  Figure 9. Posterior view of the rhomboids [Moore’s] Posterior Scapulohumeral Muscles: Intrinsic Shoulder Muscles Figure 7.B Latissimus dorsi [Moore’s] 1. Deltoid 2. Deep Layer Acts on the vertebral column MAIN ABDUCTOR OF THE ARM Provide direct attachment of the appendicular skeleton to the Shaped like an inverted delta/triangle (literal translation) axial skeleton Keeps shoulder round → Levator Scapulae 2. Teres Major ▪ Literal translation: muscle that lifts the scapula "Teres" means round ▪ Connects the upper limb to the vertebral column and Assists the latissimus dorsi in extending the humerus lies in the posterior triangle of the neck. 3. Teres Minor ▪ Superior aspect of the levator scapulae is covered by Narrow elongate muscle sternocleidomastoid, and its inferior part by trapezius 4. Supraspinatus ▪ Acts with the descending part of the trapezius to elevate the scapula, or fix it (resists forces that would Occupies the supraspinatus fossa depress it, as when carrying a load) Literal translation: muscle above the spine (spine of scapula) ▪ Acting bilaterally (also with the trapezius), the levators 5. Infraspinatus extend the neck Occupies the medial 3 quarters of the infraspinatus fossa ▪ Acting unilaterally, the muscle may contribute to lateral Action: Laterally rotates the arm (MAIN LATERAL flexion of the neck (toward the side of the active ROTATOR) muscle) Literal translation: muscle below the spine 6. Subscapularis Triangular muscle Lies on the costal surface of the scapula Forms the posterior wall of the axilla PRINCIPAL MEDIAL ROTATOR OF THE ARM Insert into lesser tubercle of humerus Literal translation: muscle under the scapula Figure 8. Posterior and lateral view of Levator Scapulae [Moore’s] → Rhomboids ▪ Literal translation: parallelogram shaped muscle ▪ Rhombus-shaped muscles ▪ Associated with the scapula and are chiefly responsible for its retraction. ▪ innervated by the dorsal scapular nerve. ▪ Thin, flat rhomboid major is approximately two times wider than the thicker rhomboid minor lying superior to it ▪ Also assist the serratus anterior in holding the scapula Figure 10. Scapulohumeral muscles [Moore’s] against the thoracic wall, and fixing the scapula during Glenohumeral Joints movements of the upper limb Is a ball and socket joint between the scapula and the humerus. It is the major joint connecting the upper limb to the trunk. It is one of the most mobile joints in the human body, at the cost of joint stability. protected: anterior, posterior, superior parts ANA Fascia and Muscle Compartments of the Upper Limbs 9 of 19  not protected: inferior part Triangle of Auscultation Shallow cavity of glenohumeral fossa: frequent dislocation a relative thinning of the musculature of the back, situated along towards the anterion part; common accident at basketball the medial border of the scapula. Rotator Cuff Muscles (“SITS”) Formed by superomedial border of latissimus dorsi, inferolateral a group of muscles and their tendons that act to stabilize the border of trapezius, lower part of scapula shoulder. Are where you apply your stethoscope to hear the sounds of the reinforce joint capsule, hold the humeral head in the glenoid posterior lungs, lesser intervening structures cavity primary function: to "grasp" and pull the relatively large head of Axilla humerus medially pyramidal space inferior to glenohumeral joint, superior to the → Supraspinatus axillary fascia at the junction of arm and thorax → Infraspinatus distribution center → Teres Minor has apex, base and 4 walls → Subscapularis → Anterior wall: Pectoralis major & Pectoralis minor → Posterior wall: Latissimus dorsi, Teres major, Subscapularis → Medial wall: Serratus anterior → Lateral wall: Humerus landmark for brachial artery, brachial plexus, and lymph nodes draining the breast (sometimes breast extends to axilla) → Apex of Axilla ▪ Cervico-axillary canal ▪ Passageway b/w neck and axilla ▪ Bounded by 1st rib, clavicle & superior edge of the scapula → Base of Axilla ▪ Forms the axillary fossa (armpit) ▪ Bounded by anterior and posterior axillary folds, Figure 11. Rotator Cuff muscles [Moore’s] thoracic wall and medial aspect of the arm Fascia of the Pectoral Region → Anterior Wall 1. Pectoral Fascia ▪ 2 layers: formed by Pectoralis major and minor & Covers Pectoralis major clavipectoral fascia sending numerous prolongations between its fasciculi ▪ Anterior axillary fold (inferior most part that may it is attached, in the middle line, to the front of the be grasped by fingers) sternum; above, to the clavicle; laterally and below it is → Posterior Wall continuous with the fascia of the shoulder, axilla, and ▪ Formed by scapula, subscapularis muscles, teres thorax. major and latissimus dorsi 2. Clavipectoral Fascia → Medial Wall ▪ Formed by thoracic wall (1st to 4th ribs and Extends from the clavicle, covers the Pectoralis minor intercostal muscles) and serratus anterior and extends to join the axillary fascia → Lateral Wall Suspensory ligament: part of clavipectoral fascia ▪ Narrow bony wall formed by intertubercular groove inferior to the pectoralis minor; supports the axillary in the humerus fascia 3. Axillary Fascia Fascia between the pectoralis major and latissimus dorsi, forming the base of axilla Subfascial Spaces 1. Quadrangular Space Above: Teres minor Below: Teres major Medial: long head of Triceps brachii Lateral: Humerus Contents: Axillary nerve, Post humeral circumflex artery 2. Triangular Space Above: Teres minor Figure 12. Axilla [Moore’s] Below: Teres major Lateral: long head of Triceps brachii D. MUSCLES OF THE ARM I. Anterior Arm: Flexor Muscles Contents: Circumflex scapular artery from subscapular Nerve supply: Musculocutaneous nerve artery 3. Lower Triangular Space Blood supply: Brachial artery Above: Teres major 3 flexor muscles Medial: long head of triceps brachii Biceps brachii Lateral: Humerus Fusiform muscle with 2 heads as the proximal attachment Contents: Radial Nerve and Profunda Brachii Artery ANA Fascia and Muscle Compartments of the Upper Limbs 10 of 19  → “bi” two + “caput” head → Musculocutaneous nerve (C5, C6, C7) Although located in the anterior compartment of the arm, it has Action no attachment to the humerus → Flexion and adduction of the arm “three-joint” muscle, affects movement primarily at the latter two → Stabilize glenohumeral joint → Glenohumeral joint → Resists downward dislocation of the head of the humerus → Elbow joint (Shunt muscle) → Radio-ulnar joint ▪ Resists dislocation of the shoulder Action and effectiveness markedly affected by the position of elbow and forearm II. Posterior Arm Extensor Muscle → Elbow flexed close to 90°, forearm is supinated Nerve supply: Radial nerve ▪ Most efficient in producing flexion Blood supply: Profunda brachii artery → Forearm is pronated 2 extensor muscles ▪ Biceps is the primary (most powerful) supinator of the forearm Triceps brachii ▪ Barely operates as a flexor when pronated A large fusiform muscle in the posterior arm Origin (Proximal) → “tri” three + “caput” head → Short head: Tip of the coracoid process of the scapula Three heads → Long head: Supraglenoid tubercle of the scapula → Long Insertion (Distal) → Lateral → Radial tuberosity → Medial → Fascia of the forearm via bicipital aponeurosis MAIN EXTENSOR of the forearm ▪ Bicipital aponeurosis Origin (Proximal) − A triangular membranous band that runs from the → Long head: Infraglenoid tubercle of the scapula biceps tendon across the cubital fossa and merges with → Lateral head: Posterior surface of the humerus, superior to the antebrachial fascia radial groove (proximal half) − Protects the structures in the cubital fossa → Medial head: Posterior surface of the humerus, inferior to − helps lessen the pressure of the biceps tendon during radial groove (distal 2/3) pronation and supination Insertion (Distal) Innervation → Proximal end of olecranon of ulna and fascia of forearm → Musculocutaneous nerve (C5, C6, C7) Innervation → Biceps reflex – tests the integrity of the musculocutaneous → Radial nerve (C5, C7, C8) nerve and the C5 and C6 spinal cord segments Action Action → Long head → Supination of the forearm (Primary supinator) ▪ Least active head → Flexion of elbow joint ▪ Extension and adduction of the arm → Short head resists dislocation of the shoulder ▪ Resists dislocation of the head of the humerus (Shunt muscle) Brachialis → Lateral head A flattened fusiform muscle lying posterior (deep) to the biceps ▪ Strongest head MAIN FLEXOR of the forearm ▪ Primarily acts against resistance → only the pure flexor of the forearm → Medial head → produces the greatest amount of flexion force ▪ Deep Flexes the forearm in all positions regardless of supination or ▪ Extension of the forearm pronation, unlike the biceps ▪ Workhorse of forearm extension Always contracts when the elbow is flexed − Active at all speeds with or without resistance → Primarily responsible for sustaining flexed position Anconeus → Regarded as the workhorse of the elbow flexors Small, triangular muscle on the posterolateral aspect of the Origin (Proximal) elbow → Distal half of anterior surface of the humerus Partially blended (continuous) with the triceps Insertion (Distal) Origin (Proximal) → Coronoid process → Posterior surface of lateral epicondyle of the humerus → Ulnar tuberosity Insertion (Distal) Innervation → Lateral surface of the olecranon fossa → Musculocutaneous nerve (C5, C6) → Superior part of the posterior surface of the ulna → Radial nerve (C5, C7) Innervation → Some lateral part is innervated by a branch of the radial → Radial nerve (C7, C8, T1) nerve (Moore, 2014) Action Action → Assists triceps in the extension of the forearm → Flexion of the forearm → Stabilizes the elbow joint Coracobrachialis → Abducts the ulna during pronation of the forearm Elongated muscle in the superomedial part of the arm → Tenses the capsule of the elbow joint Landmark for locating other structures ▪ Prevents it from being pinched during extension → Pierced by the musculocutaneous nerve Origin (Proximal) → Tip of the coracoid process of the scapula Insertion (Distal) → Middle third of the medial surface of humerus Innervation ANA Fascia and Muscle Compartments of the Upper Limbs 11 of 19  E. MUSCLES OF THE FOREARM − Origin: Humero-ulnar head: Medial epicondyle of I. Anterior Compartment humerus; Radial head: superior ½ of anterior border of radius − Insertion: shafts of middle phalanges of medial 4 digits − Innervation: median n (C7, C8, T1) − Action: flexes middle phalanges at PIP joints of middle 4 digits, Flexes proximal phalanges at MCP joints → Deep Group = 2 muscle ▪ Flexor Digitorum Profundus (FDP) − only muscle that can flex the distal interphalangeal joints of the fingers − “clothes” the anterior aspect of the ulna − Origin: Medial and Lateral Part- proximal ¾ of medial and anterior surfaces of ulna and interosseous membrane − Insertion: Medial- base of distal phalanges of 4th & 5th digits; Lateral- base of distal phalanges of 2nd & 3rd digits − Innervation: Medial- Ulnar n (C8, T1); Lateral- anterior Figure 13. Flexor Muscles of the Forearm[Moore’s] interosseous n, from median n (C8, T1) 3 muscle groups = Flexors/Pronators − Action: Medial- flexes distal phalanges 4 & 5 at DIP → Superficial group = 4 muscles joints; Lateral- flexes distal phalanges 2 & 3 at DIP → Common flexor tendon origin: medial epicondyle of humerus joints ▪ Pronator Teres (PT) ▪ Flexor Pollicis Longus (FPL) − Fusiform muscle − long flexor of the thumb (L. pollex, thumb), lies lateral − Most lateral of the superficial forearm flexors to the FDP − Its lateral border forms medial boundary of cubital − clothes anterior aspect of the radius distal to the fossa attachment of the supinator − Origin: Ulnar head- coronoid process; Humeral head- − Origin: anterior surface of radius and adjacent medial epicondyle of humerus interosseous membrane − Insertion: middle convexity of lateral surface of radius − Insertion: base of distal phalanx of thumb − Innervation: median n (C6, C7) − Innervation: anterior interroseous nerve − Action: Pronation, Flexion of forearm (at elbow) − Action: flexes phalanges of thumb ▪ Flexor Carpi Radialis (FCR) ▪ Pronator Quadratus (PQ) − Long fusiform muscle − Quadrangular − Medial to the pronator teres − Pronates the forearm − Origin: medial epicondyle of humerus − cannot be palpated or observed − Insertion: base of 2nd metacarpal − cannot be palpated or observed, except in dissections, − Innervation: median n (C6, C7) because it is the deepest muscle in the anterior aspect − Action: Flexes, abducts hand (at wrist joint) of the forearm ▪ Palmaris Longus (PL) − Origin: distal quarter of anterior surface of ulna − Small fusiform muscle − Insertion: distal quarter of anterior surface of radius − Guide to the median nerve at the wrist − Innervation: anterior interosseous nerve from median − Its tendon lies deep and medial to median nerve before nerve (C8, T1) it passes deep to the flexor retinaculum − Action: pronates forearm − Origin: medial epicondyle of humerus Nerve Supply: Median Nerve except for ½ ms (FCU + part of − Insertion: distal ½ of flexor retinaculum apex of palmar FDP) aponeurosis Anterior Forearm Subfascial Space − Innervation: median n (C7, C8) Cubital Fossa − Action: flexes hand (at wrist), tenses palmar → Radial nerve aponeurosis → Biceps brachii tendon ▪ Flexor Carpi Ulnaris (FCU) → Brachial artery and vein – terminal − Most medial of the superficial flexor muscles → Median nerve (overlying) median cubital vein − tendon of the FCU is a guide to the ulnar nerve and artery (lateral side at the wrist) III. Posterior Compartment − Origin: Humeral head- medial epicondyle of humerus; Ulnar head- olecranon & posterior border of ulna (via aponeurosis) − Insertion: pisiform bone, hook of hamate, 5th metacarpal bone − Innervation: ulnar n. (C7, C8) − Action: Flexes hand, adducts hand, at wrist joint → Intermediate group = 1 muscle ▪ Flexor Digitorum Superficialis (FDS) − sometimes considered one of the superficial muscles of the forearm, which attach to the common flexor origin and therefore cross the elbow − largest superficial muscle in the forearm − forms an intermediate layer between the superficial and Figure 14. Extensor Muscles of the Forearm[Moore’s] deep groups of forearm muscles Blood Supply: Radial & ulnar aa. Nerve supply: Radial nerve ANA Fascia and Muscle Compartments of the Upper Limbs 12 of 19  − Origin: lateral epicondyle of humerus, radial collateral → Flexor: Brachioradialis and annular ligaments, supinator fossa, crest of ulna − Fusiform muscle − Insertion: lateral, posterior, and anterior surfaces of − Superficial on the anterolateral surface of the forearm proximal 1/3 of radius − Forms the lateral border of the cubital fossa Innervation: deep branch of radial nerve − exceptional among muscles of the posterior (extensor) − Action: supinates forearm, rotates radius to turn palm compartment in that it has rotated to the anterior aspect anteriorly or superiorly (if elbow is flexed) of the humerus and thus flexes the forearm at the → Abductor Pollicis Longus (APL) elbow − Long fusiform belly − Origin: proximal 2/3 of supra-epicondylar ridge of − Distal to the supinator humerus − Origin: posterior surface of proximal ½ of ulna, radius − Insertion: lateral of distal end of radius proximal to and interosseous membrane styloid process − Insertion: base of 1st metacarpal − Innervation: radial n (C5, C6, C7) Innervation: posterior interosseous nerve − Action: weak flexion of forearm, maximal when forearm − Action: abducts thumb, extends thumb at CMC joint is midpronated position → Extensor Pollicis Brevis (EPB) → Extensors: − Fusiform short extensor of thumb ▪ Extensor carpi radialis longus (ECRL) − Distal to APL − fusiform muscle − Origin: posterior surface of middle 1/3 of ulna and − partly overlapped by the brachioradialis, with which it interosseous membrane often blends − Insertion: distal aspect of base of distal phalanx of − active when clenching the fist thumb − Origin: lateral supra-epicondylar ridge of humerus Innervation: posterior interosseous nerve − Insertion: dorsal aspect of base of 2nd metacarpal − Action: extends distal phalanx of thumb at IP joint, − Innervation: radial n (C6, C7) extends MCP and CMC joints − Action: extends, abducts hand (at wrist joint) → Extensor Pollicis Longus ▪ Extensor carpi radialis brevis (ECRB) − Origin: posterior surface of distal 1/3 of radius, and − shorter muscle than the ECRL because it arises distally interosseous membrane in the limb, yet it attaches adjacent to the ECRL in the − Insertion: dorsal aspect of base of proximal phalanx of hand (but to the base of the 3rd metacarpal rather than thumb the 2nd). − Innervation: posterior interosseous nerve − Origin: Lateral epicondyle of humerus (common − Action: extends proximal phalanx of thumb at MCP extensor) joint, extends CMC joint − Insertion: dorsal base of 3rd metacarpal → Extensor Indicis − Innervation: deep branch of radial n (C7, C8) − Origin: posterior surface of distal 1/3 of ulna − Action: extends, abducts hand (at wrist joint) interosseous membrane ▪ Extensor digitorum communis (EDC) − Insertion: extensor expansion of 2nd (index) digit − Main extensor of digits − Innervation: posterior interosseous nerve − Posterior surface of the forearm − Action: extends 2nd digit, helps extend hand at wrist − Origin: Lateral epicondyle of humerus (common extensor) Anatomical Snuffbox − Insertion: extensor expansion of medial 4 digits Fascial space between tendons of EPL & EPB (APL) − Innervation: deep branch of radial n (C7, C8) Content: Radial a. − Action: extends medial 4 digits primarily at MCP joints, Floor: scaphoid & trapezium secondarily at IP joints ▪ Extensor digiti minimi (EDM) − fusiform slip of muscle − extends little finger − Origin: Lateral epicondyle of humerus (common extensor) − Insertion: extensor expansion of 5 digits − Innervation: deep branch of radial n (C7, C8) − Action: extends 5th digit primarily at MCP joints, secondarily at IP joints ▪ Extensor carpi ulnaris (ECU) − long fusiform muscle − located on the medial border of the forearm, has two heads: a humeral head and an ulnar head − Origin: Lateral epicondyle of humerus posterior border of ulna visa shared aponeurosis − Insertion: dorsal aspect of base of 5th metacarpal − Innervation: deep branch of radial n (C7, C8) Figure 15. Anatomical Snuffbox[Moore’s] − Action: extends, adducts hand (at wrist joint), also active during first clenching Reconstruction of Anterior Cruciate Ligament (ACL) Palmaris Longus tendon is used -> made into a ligament for Extensor retinaculum – band of tissue, part of the pulley system ACL reconstruction that caused movement on fingers → Supinator − Lies deep in the cubital fossa − Along with brachialis, forms its floor ANA Fascia and Muscle Compartments of the Upper Limbs 13 of 19  F. MUSCLES OF THE HAND − Origin: Flexor retinaculum, Tubercle of trapezium Important Terminologies − Insertion: Lateral side of base of proximal phalanx of → Tendon thumb ▪ muscle to bone attachment − Action: Flexion of proximal phalanx of thumb → Ligament ▪ Opponens Pollicis ▪ bone to bone attachment − Quadrangular muscle that opposes the thumb → Aponeurosis − Origin: Flexor retinaculum, Tubercles of trapezium ▪ tendons that form flat sheets to attach muscle to the bone − Insertion: Lateral side of 1st metacarpal or fascia − Action: Flexion and medial rotation of 1 st metacarpal → Retinaculum/Retinacula at CMC joint (carpometacarpal joint) during opposition ▪ Thickened deep fascia that hold tendons in place Central Compartments ▪ Prevents the tendons from bow stringing or taking a ▪ Lumbricals shortcut across the angle created. − Literal trans: worm-like → Bursae/Bursa − Innervation: Median nerve (1st& 2nd), Ulnar nerve ▪ closed sacs serous membrane that secretes fluid to (3rd& 4th) lubricate/provide nourishment to the internal surface. − Origin: Lateral 2 tendons of FDP (for 1st& 2nd Deep Fascia of the Hand lumbricals), Medial 3 tendons of FDP (for 3rd& 4th Flexor retinaculum lumbricals) Palmar aponeurosis − Insertion: Lateral sides of extensor expansion of 2nd& Extensor retinaculum 3rd digits, Lateral sides of extensor expansion of 4th& Dorsal fascia 5th digits Digital fibrous flexor sheaths − Action: Flexion of digits at the MCP joints; Extends digits at IP joint Fascial Spaces ▪ Adductor Pollicis Thenar − Fan-shaped Hypothenar − Origin: (Oblique head) bases of 2nd& 3rd metacarpals; Central compartment capitate and adjacent bones; (Transverse head) → Palmar space anterior surface of 3rd metacarpal ▪ Thenar − Insertion: Medial side of base of proximal phalanx of ▪ Midalmar (via carpal tunnel → anterior forearm thumb compartment) − Action: Flexes thumb to the palm/adduction of thumb → Synovial flexor sheaths ▪ Interossei ▪ Ulnar bursa − Dorsal Interosseous Muscles – abduction of digits (4 ▪ Radial bursa muscles) Carpal Tunnel − Palmar Interosseous Muscles – adduction of digits (3 muscles) Median nerve − Mnemonic: D-Ab, P-Ad (nerve supply: ulnar nerve) Flexor digitorium superficialis − Together with lumbricals produce Z-movement (flexion Flexor digitorum profundus of MCP joints and extension of IP joint) which is the Flexor pollicis longus opposite of claw hands Intrinsic Muscles of the Hand Hypothenar Compartments (AFO- ADM, FDM, ODM) Thenar Compartment (AFO- APB, FPB, OP) → Acts on little finger (digiti minimi) – second greatest range of → Responsible for thumb movement (main use:opposition) motion in hand → Nerve Supply: Median nerve (Recurrent branch) → Innervation: Ulnar Nerve Figure 17. Muscles of the Hypothenar Compartment [Teach Me Anatomy App] ▪ Abductor Digiti Minimi − Most superficial layer − Origin: Pisiform, Tendon of FCU Figure 16. Muscles of the Thenar Compartment [Teach Me Anatomy App] − Insertion: Medial side of base of proximal phalanx of ▪ Abductor Pollicis Brevis (AbPoBre/APB) digiti minimi − Origin: Flexor retinaculum, Tubercles of scaphoid and − Action: Abduction of digiti minimi, Assist in flexion of trapezium proximal phalanx of digiti minimi − Insertion: Lateral side of base of proximal phalanx of ▪ Opponens Digiti Minimi thumb − Literal trans: muscle that places the little finger on the − Action: Abduction of thumb opposite side ▪ Flexor Pollicis Brevis − Origin: Flexor retinaculum, Hook of Hamate − Short flexor of thumb − Insertion: Palmar surface of 5th metacarpal − Innervations: median nerve for larger superficial head − Action: Draws 5th metacarpal anteriorly and rotates it ulnar nerve for smaller deep head to face thumb (opposition) ANA Fascia and Muscle Compartments of the Upper Limbs 14 of 19  ▪ Flexor Digiti Minimi − Short flexor (literal trans: bends little finger) − Origin: Flexor retinaculum − Insertion: Base of proximal phalanx of digiti minimi − Action: Flexion of digiti minimi III.REVIEW QUESTIONS 1. Question: Only muscle in the intermediate layer of the arm? a. Pronator Teres b. Flexor Digitorum Superficialis c. Flexor Digitorum Profundus 2. Question: Only joint that connects the thorax to the upper limbs? a. Glenohumeral b. Scapulothoracic c. Sternoclavicular Answer Key: 1.B, 2.C IV. REFERENCES 2022A Trans Dr. Bautista’s Fascia and Muscle Compartments of the Upper Limbs Lecture Slides and Voice Recording Moore, K. et. Al (n.d.), Clinically oriented anatomy (7 th ed) Baltimore: Lippincott Williams & Wilkins ANA Fascia and Muscle Compartments of the Upper Limbs 15 of 19  Muscles Connecting the Upper Limb to the Thoracic Wall/ Muscles of the Pectoral Region (except Serratus Anterior) Muscle Origin Insertion Innervation Action Pectoralis Major Clavicle, sternum and Lateral lip of the bicipital Medial and lateral pectoral Adducts arm and rotates it upper six costal cartilages groove of humerus nerves form brachial plexus medially; clavicular fibers also flex arm Pectoralis Minor 3rd, 4th and 5th ribs Coracoid process of Medial pectoral nerve from Depresses point of shoulder; if scapula brachial plexus the scapula is fixed, it elevates the ribs of origin Subclavius First costal cartilage Clavicle Nerve to subclavius from upper Depresses the clavicle and trunk of brachial plexus steadies this bone during movements of the shoulder girdle Serratus Anterior Upper eight ribs Medial border and inferior Long thoracic nerve Draws the scapula forward angle of the scapula around the thoracic wall; rotates the scapula Muscles Connecting the Upper limb to the Vertebral Column/ Superficial (Appendicular) Group of Back Muscles Muscle Origin Insertion Innervation Action Trapezius Occipital bone, ligamentum Upper fibers into lateral third Spinal part of accessory nerve Upper fibers elevate the nuchae, spine of 7th cervical of clavicle; middle and lower (motor) and C3 and C4 scapula; middle fibers pull the vertebra, spines of all thoracic fibers into acromion and spine (sensory) scapula medially; lower fibers vertebra of the scapula pull medial border of the scapula downward Latissimus Dorsi Iliac crest, lumbar fascia, Floor of bicipital groove of Thoracodorsal nerve Extends, adducts and spines of lower six thoracic humerus medially rotates the arm vertebrae, lower three or four ribs, and inferior angle of the scapula Levator Scapulae Transverse processes of first Medial border of the scapula C3 and C4 and dorsal Raises medial border of the four cervical vertebrae scapular nerve scapula Rhomboid Minor Ligamentum nuchae and Medial border of the scapula Dorsal scapular nerve Raises medial border of spines of 7th cervical vertebra scapula upward and medially and 1st thoracic vertebra Rhomboid Major 2nd to 5th thoracic spines Medial border of scapula Dorsal scapular nerve Raises medial border of scapula upward and medially Muscles Connecting the Scapula to the Humerus Muscle Origin Insertion Innervation Action Deltoid Lateral third of clavicle, Middle of lateral surface of Axillary nerve Abducts arm; anterior fibers acromion, spine of scapula shaft of humerus flex and medially rotate arm; posterior fibers extend and laterally rotate arm ANA Fascia and Muscle Compartments of the Upper Limbs 16 of 19 Supraspinatus Supraspinous fossa of Greater tuberosity of Spurascapular nerve Abducts arm and stabilizes scapula humerus; capsule of shoulder shoulder joint joint Infraspinatus Infraspinous fossa Greater tuberosity of Suprascapular nerve Laterally rotates arm and humerus; capsule of shoulder stabilizes shoulder joint joint Teres Major Lower third of lateral border of Medial lip of bicipital groove of Lower subscapular nerve Medially rotates and adducts scapula humerus arm and stabilizes shoulder joint Teres Minor Upper two thirds of lateral Greater tuberosity of the Axillary nerve Laterally rotates arm stabilizes border of the scapula humerus; capsule of shoulder shoulder joint joint Subscapularis Subscapular fossa Lesser tuberosity of humerus Upper and lower subscapular Medially rotates arm and nerves stabilizes shoulder joint Muscles of the Arm Muscle Origin Insertion Innervation Action Anterior Compartment Biceps Brachii ✓ Long head Supraglenoid tubercle of Tuberosity of radius and Musculocutaneous nerve Supinator of forearm and scapula bicipital aponeurosis into deep flexor of elbow joint; weak ✓ Short head Coracoid process of scapula fascia of forearm flexor of shoulder joint Coracobrachialis Coracoid process of scapula Medial aspect of shaft of Musculocutaneous nerve Flexes arm and also weak humerus adductor Brachialis Front of lower half of humerus Coronoid process of ulna Musculocutaneous nerve Flexor of elbow joint Posterior Compartment Triceps ✓ Long head Infraglenoid tubercle of scapula ✓ Lateral head Upper half of posterior surface Olecranon process of ulna Radial nerve Extensor of elbow joint of shaft of humerus ✓ Medial head Lower half of posterior surface of shaft of humerus Muscles of the Anterior Fascial Compartment of the Forearm Muscle Origin Insertion Innervation Action Pronator Teres ✓ Humeral head Medial epicondyle of humerus Lateral aspect of the shaft of Pronation and flexion of ✓ Ulnar head Medial border of coronoid Median nerve radius forearm process of ulna Flexor Carpi Rad