Muscle Microanatomy Department of Biology, WCU

Introduction Types 1. Skeletal Skeletal, smooth, cardiac cover skeleton Striations voluntary control rapid contractions

Introduction 2. Smooth walls of hollow organs no striations involuntary control slow contractions

Introduction 3. Cardiac involuntary control Striations contractions slow but variable

Structural characteristics Common features 1. Nucleated 2. Fibers 3. Myofilaments

Functional characteristics 1. Excitable 2. Contractible 3. Extensible 4. Elastic

Gross anatomy Layers 1. Epimysium 2. Perimysium 3. Endomysium Muscle 1 - 40 mm Body cell 10 - 40 µm

Microscopic anatomy Sarcolemma Sarcoplasm myofibril myoglobin elaborate ER

Myofibril rod-like filaments (80%) sarcomeres

Sarcomere Definition A band I band H zone M line

Sarcoplasmic Reticulum SER Terminal cisternae Store and release Ca++

Triad T system T tubule (telegraph)

Comparative anatomy 1. Skeletal Multinucleate Long axis contraction

Comparative anatomy 2. Smooth 1 nucleus no striations only endomysium no t-tubules poorly developed SR

Comparative anatomy 2. Smooth occurs in 2 layers outer longitudinal inner circular

Comparative anatomy 3. Cardiac muscle one or two nuclei striations only endomysium few SR intercalated disks

Comparative anatomy 3. Cardiac muscle intercalated disks desmosomes gap junctions