Biology 322 Human Anatomy I Muscle Histology

Muscle Tissue: 3 Types: Skeletal Muscle Cardiac Muscle Smooth Muscle Voluntary Striated Involuntary Nonstriated

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

We have learned the names, locations, origins, and insertions of skeletal muscles (organs) in lab. We will now discuss the cytology (cells) & histology (tissues) of skeletal muscle, then do a brief review of their shapes, sizes, and functions in different regions of the human body. We will discuss cardiac muscle when we discuss the heart, and we will discuss smooth muscle when we discuss the circulatory, digestive, and other systems where it is located.

Muscle: Special Terminology: Prefixes = Cell = Plasma membrane = Endoplasmic reticulum = Cytoskeletal Filaments = Myo- / Sarco- Myocyte ("Fiber") Sarcolemma Sarcoplasmic reticulum Myofilaments

Skeletal Muscle: Always voluntary: Each myocyte is connected to and controlled by an axon from a motor neuron. High metabolism Myocytes 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

Muscle Myocyte Myofibril Myofilaments

Thick and thin myofilaments forming part of a myofibril Z-line Sarcomere

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

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

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

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.

One motor neuron + All myocytes it innervates = one Motor Unit

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

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