Three classes of muscle Skeletal muscle - responsible for locomotion Cardiac muscle - responsible for the action of the heart Smooth muscle - responsible for the contraction of irregular shaped organs such as the intestines.

MUSCLE TISSUE Skeletal muscle 100 µm Multiple nuclei Muscle fiber Sarcomere Cardiac muscle Nucleus Intercalated disk 50 µm Smooth muscle Nucleus Muscle fibers 25 µm NERVOUS TISSUE Neurons Process Cell body Nucleus 50 µm

Structure and Function of Skeletal Muscle

Skeletal Muscle Mammal body contains over 400 skeletal muscles –Approx % of total body weight

Skeletal Muscle Functions of skeletal muscle –Force production for locomotion and breathing –Force production for postural support –Heat production during cold stress –Saleable product in livestock production

Skeletal Muscles Muscles generally work in pairs to produce movement One muscle flexes (or contracts) the other relaxes This process is known as antagonism

Structure of Skeletal Muscle: Connective Tissue Covering Epimysium –Surrounds entire muscle Perimysium –Surrounds bundles of muscle fibers Fascicles Endomysium –Surrounds individual muscle fibers

Structure of Skeletal Muscle: Microstructure Sarcolemma –Muscle cell membrane Myofibrils –Threadlike strands within muscle fibers –Actin (thin filament) Troponin Tropomyosin –Myosin (thick filament)

Collagenous fiber Elastic fiber Chondrocytes Chondroitin sulfate Loose connective tissue Fibrous connective tissue 100 µm Nuclei 30 µm Bone Blood Central canal Osteon 700 µm55 µm Red blood cells White blood cell Plasma Cartilage Adipose tissue Fat droplets 150 µm CONNECTIVE TISSUE

Smooth Muscles Lumen of stomach Mucosa. The mucosa is an epithelial layer that lines the lumen. Submucosa. The submucosa is a matrix of connective tissue that contains blood vessels and nerves. Muscularis. The muscularis consists mainly of smooth muscle tissue. 0.2 mm Serosa. External to the muscularis is the serosa, a thin layer of connective and epithelial tissue. Smooth muscle