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