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Introduction to Muscle Anatomy

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Presentation on theme: "Introduction to Muscle Anatomy"— Presentation transcript:

1 Introduction to Muscle Anatomy

2 Types of Muscle 1. Skeletal Elongated Cells Multi nucleated
Striated – striped appearance Voluntary Produces powerful contractions Tires easily, needs rest (fatigue). Covers bony skeleton (motility) Longitudinal View Notice striations and nuclei around outside of cell. Cross Section Notice nuclei around outside of cell.

3 Skeletal Muscle Composite Sketch

4 2. Smooth Spindle-shaped Cell Single nucleus in each cell
No Striations Involuntary Slow, sustained contractions In hollow visceral organs (stomach, bladder, respiratory passages) Cross Section Nucleus is in center of cell. Cells much smaller.

5 Smooth Muscle Composite Sketch

6 3. Cardiac (Heart) Branched cell Contain intercalated discs
Single nucleus in each cell Striations Involuntary Steady, constant contractions Never tires

7 Cardiac Muscle Composite Sketch

8 Muscle Functions Produce movement Maintain posture Stabilize joints
locomotion & manipulation Help blood move through veins & food thru small intestines Maintain posture Stabilize joints Body temp homeostasis Shivering: movement produces heat energy

9 Muscle Requirements Demands continuous oxygen/nutrient supply.
Axon of neuron Motor end plate (terminus) Demands continuous oxygen/nutrient supply. Lots of arteries/capillaries to muscle. Each muscle cell w/ its own nerve ending controlling its activity. Produce much metabolic waste due to constant activity.

10 Muscle Attachments Most muscles span joints
Attaches to bone in two places: (video) 1. Insertion: the moveable bone Bicep insertion is the radius 2. Origin: the stationary bone bicep originates in two different places in scapula Attachment types Direct: attaches right onto bone - ex. intercostal muscles of ribs Indirect: via tendon or aponeurosis (sheet-like tendon) to connect to bone - leaves bone markings such as tubercle

11 Muscle Organization Muscles are complex bundled structures: fibers within fibers

12 Muscle organization Muscle (organ) Fascicle Muscle fiber (cell)
Myofibril Sarcomere Myofilaments: Actin & Myosin

13 Muscle Fibers A Muscle Fiber = Muscle Cell HUGE cell:
m in diameter can be hundreds of centimeters long (created by cytoplasmic fusion of multiple embryonic cells) extends the length of the muscle Main content: bundles of proteins (actin and myosin) Multinucleated to maintain high rate of protein synthesis. Muscle fiber nucleus = myonucleus

14 Insulation of Muscles Muscle cells must be insulated from one another by specialized membranes Muscle cells work electrically if not insulated, nerves cannot control individual muscles.

15 Epimysium surrounds entire muscle
Dense CT that merges with tendon Epi = outer Mys = muscle Perimysium surrounds muscle fascicles Peri = around Within a muscle fascicle are many muscle fibers Endomysium surrounds muscle fiber Endo = within

16 Structural Terminology Associated with Muscle Fibers
Prefixes: myo, mys, and sarco all refer to muscle Sacroplasmic Reticulum = Smooth ER of muscle (regulates calcium levels for muscle contraction) Sarcoplasm = Cytoplasm To maintain ATP production during cellular respiration, contains high amounts of: mitochondria glycosomes that store sugar oxygen binding protein called myoglobin Sarcolemma = Plasma Membrane T tubules - The sarcolemma of muscle cells are not just on the outside, rather forms tubes that dive into the muscle cells Myosin and Actin= muscle proteins that create muscle cytoskeletal filaments for contraction

17 myofibril Sarcoplasmic Reticulum Myosin (red) and Actin (blue) T-tubule sarcolemma

18 Microstructures Each muscle fiber (muscle cell), is composed of many myofibrils. Organized system of cytoskeleton filaments of actin and myosin proteins that do the actual contracting Myofibrils are NOT CELLS A sarcomere is one segment of a myofibril (muscle segments). The series of sarcomeres produce the striated appearance of muscles

19 Muscle Fiber Sarcomere


21 Sarcomere organization
Myofibril composed of repeating series of sarcomeres with dark A and light I bands. I bands intersected by Z discs mark the outer edges of each sarcomere. Contraction happens within one sarcomere.

22 Sarcomere Banding Pattern

23 How do muscle contract? Let’s sketch the sarcomere together and discuss the sliding filament model of muscle contraction

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