Lab Exam 4
Muscle Histology Quick-Reference
Muscle Type | Key Microscopic Identifiers | Control & Action | Primary Locations |
Skeletal | Striated, long unbranched cylinders, peripheral multinuclear | Voluntary; locomotion & posture | Skeleton, tongue, pharynx |
Cardiac | Striated, branching, single central nucleus, intercalated discs | Involuntary; pumps blood | Heart wall (myocardium) |
Smooth | Non-striated, spindle/fusiform shape, single central nucleus | Involuntary; peristalsis & vasoconstriction | Hollow organs, blood vessels |
High-Yield Muscle Functional Groups
Mastication (Chewing): Masseter & Temporalis (both elevate mandible).
Anterior Abdominal Wall (Superficial to Deep): External oblique → Internal oblique → Transverse abdominis. Rectus abdominis sits vertically inside the rectus sheath along the linea alba.
Rotator Cuff (SITS): Supraspinatus (abduction initiation), Infraspinatus (lateral rotation), Teres minor (lateral rotation), Subscapularis (medial rotation).
Quadriceps Femoris (Knee Extensors): Rectus femoris (also flexes hip), Vastus lateralis, Vastus medialis, Vastus intermedius.
Hamstrings (Hip Extensors / Knee Flexors): Biceps femoris, Semitendinosus, Semimembranosus.
Calf / Plantar flexors: Gastrocnemius (flexes knee & foot) and Soleus (flexes foot only) via calcaneal tendon.
Origins & Insertions Summary
Sternocleidomastoid: Sternum/Clavicle → Mastoid process of temporal bone
Pectoralis Major: Sternum/Clavicle → Greater tubercle of humerus
Pectoralis Minor: Ribs 3–5 → Coracoid process of scapula
Deltoid: Clavicle/Acromion/Spine of scapula → Deltoid tuberosity of humerus
Latissimus Dorsi: T7–L5/Sacrum/Iliac crest → Intertubercular groove of humerus
Biceps Brachii: Long head (Supraglenoid tubercle) & Short head (Coracoid process) → Radial tuberosity
Supraspinatus & Infraspinatus: Fossa of same name → Greater tubercle of humerus
Gastrocnemius: Femoral condyles → Calcaneus
Rectus Abdominis: Pubic crest/symphysis → Xiphoid process & costal cartilages 5–7