Biology 322 Human Anatomy I Histology of Muscle

Muscle Tissue: 3 Types: Skeletal Muscle Cardiac Muscle Smooth Muscle

Muscle Muscle Muscle Myocytes Nuclei Striations Skeletal Cardiac Smooth Muscle Muscle Muscle Very long Unbranched Shorter Branched Short Spindle-shaped Hundreds per cell Peripheral One or two per cell Central One per cell Yes No Myocytes Nuclei Striations

Muscle: Special Terminology: Prefixes = Cell = Plasma membrane = Endoplasmic reticulum = Cytoskeletal Filaments =

Skeletal Muscle: Always voluntary. Each myocyte connected to and controlled by an axon from a motor neuron. Because of high metabolism, myocytes must be very close to capillaries. Myocytes are all oriented parallel to long axis of muscle which is Parallel to direction which muscle pulls when it contracts & lengthens when it relaxes

Prominent Organelles in Myocytes: - Sarcolemma - Nuclei - Myofibrils (highly organized bundles of myofilaments - Transverse tubules (inward extensions of sarcolemma) - Sarcoplasmic reticulum - Mitochondria Keep in mind: Even though not prominent, all other organelles also present (vesicles, ribosomes, lysosomes, Golgi apparatus, etc.

Myocyte (muscle cell) Myofibril Thick & thin myofilaments

Thick and thin myofilaments forming part of a myofibril

Skeletal Muscle Anatomy: Each myocyte surrounded by, and firmly attached to, layer of loose connective tissue called

Skeletal Muscle Anatomy: Myocytes grouped together into bundles called each fascicle surrounded by, and firmly attached to, layer of dense irregular connective tissue called

Skeletal Muscle Anatomy: Entire muscle surrounded by, and firmly attached to, layer of dense irregular connective tissue called

Skeletal Muscle Anatomy: All three layers of connective tissue blend together at each end of muscle. Thus force transmitted from: Myocytes Endomysium Perimysium Epimysium Tendon, bone, etc.

Skeletal myocytes = VOLUNTARY Can only contract when stimulated by motor neuron Myoneural junction or Neuromuscular junction

One motor neuron + All myocytes it innervates =

1. Myocytes and muscles always pull (exert force by Skeletal Muscle: 1. Myocytes and muscles always pull (exert force by contraction), they never push. They usually, although not always, pull on bone through a tendon. 2. If a sarcomere shortens, it always does so completely "All-or-none" 3. All of the sarcomeres in the entire myocyte shorten at the same time. "All-or-none" But: 4. All of the myocytes in a muscle don't always contract at the same time. No "all-or-none"

Skeletal Muscle: The total force produced by a myocyte is equal to the sum of the forces produced by individual sarcomeres. Thus: More sarcomeres = more force The total force produced by a muscle is equal to the sum of the forces produced by individual sarcomeres. Thus: More myocytes = more force