The Muscular System: Micro and Macro Anatomy

Muscle tissue is composed of excitable muscle fibers (cells containing the fibrous proteins actin and myosin). Muscles may provide movement, maintain posture, stabilize joints, and generate heat. There are three type of muscle tissue: uninucleate cardiac muscle, multinucleated smooth muscle, and multinucleated skeletal muscle. Diagram

I. Skeletal Muscle 

A. Gross Anatomy

B. Microanatomy

C. Contraction of a Skeletal Muscle Fiber Diagram

D. Regulation of Contraction Diagram

E. Excitation-Contraction Coupling Diagram

  1. Action potential travels along axon until axon terminal; here ACh is released causing depolarization of the motor end plate; action potential propagates along sarcolemma down T tubules.
  2. Action potential triggers Ca++ release from terminal cisternae of sarcoplasmic reticulum (calcium ion gates open).
  3. Calcium ions bind to troponin causing troponin to change shape and expose actin active sites.
  4. Contraction occurs
  5. Calcium levels decrease (due to change in permeability) and tropomyosin blockage is restored.

II. Myogram and Frequency of Stimulation

III. Muscle Metabolism

IV. Superficial Muscles Diagram1 (Anterior Superficial) Diagram2 (Anterior Trunk) Diagram3 (Superficial Facial) Diagram4 (Posterior Superficial) Diagram5 (Posterior Trunk)


  • Frontailis
  • Orbicularis oculi
  • Temporalis
  • Zygomaticus
  • Masster
  • Orbicularis oris
  • Platysma
  • Sternohyoid
  • Sternocleidomastoid
  • Deltoid
  • Pectoralis minor
  • Pectoralis major
  • Serratus anterior
  • Intercostals
  • Rectus abdominis
  • External oblique
  • Internal Oblique
  • Transverse abdominis
  • Triceps brachii
  • Biceps brachii
  • Brachialis
  • Brachioradialis
  • Flexor carpi radialis
  • Palmaris longus
  • lliopsoas
  • Pectineus
  • Tensor fasciae latae
  • Sartorius
  • Adductor longus
  • Gracilis
  • Rectus femoris
  • Vastus lateralis
  • Vastus medialis
  • Tbialis anterior


  • Occipitalis
  • Trapezius
  • Deltoid
  • Infraspinatus
  • Teres major
  • Rhomboid
  • Latissimus dorsi
  • Triceps brachii
  • Extensor carpi ulnaris
  • Extensor carpi radialis
  • Flexor carpi ulnaris
  • Extensor digitorum
  • Gluteus medius
  • Gluteus maximus
  • Biceps femoris
  • Semitendinosus
  • Semimembranosus
  • Gastrocnemius
  • Soleus