1. Essentials of Human Anatomy Anatomy of the Muscular System
Dr Fadel Naim
Ass. Prof. Faculty of Medicine
IUG
Chapter 6

2. Introduction There are more than 600 skeletal muscles in the body
From 40% to 50% of body weight is skeletal muscle
Muscles, along with the skeleton, determine the form and contour of the body

3. Functions of skeletal Muscles
Body movements
Maintaining Posture
Stabilizing Joints
Body positions
Generating heat

4. 4 Unique Characteristics of Muscle Tissue
Excitability is equated with responsiveness.
Contractility causes the fiber to shorten resulting in either a pull on bones or the movement of specific body parts.
Elasticity is the muscle’s ability to return to its original length when tension is released.
Extensibility is capability of extending in length in response to the contraction of opposing muscle fibers.

5. Structure of a Skeletal Muscle
organ of the muscular system
- skeletal muscle tissue
- nervous tissue
- blood
- connective tissues
fascia
tendons
aponeuroses

6. Skeletal Muscle Tissue
Skeletal muscles are organs
Vary in shape and size
A skeletal muscle is composed of cells
Each cell is as long as the muscle
Small muscle: 100 micrometers long; 10 micrometers in diameter
Large muscle: 35 centimeters long; 100 micrometers in diameter

7. Skeletal Muscle Structure
Connective tissue components
Endomysium—delicate connective tissue membrane that covers specialized skeletal muscle fibers
Perimysium—tough connective tissue binding together fascicles
Epimysium—coarse sheath covering the muscle as a whole
These three fibrous components may become a tendon or an aponeurosis

8. Skeletal Muscle Anatomy

10. Muscle Fiber Structure
Multiple nuclei
Sarcolemma
T-tubules
Sarcoplasmic reticulum
Sarcoplasm
Mitochondria
Glycogen & ions
Myofibrils

11. Muscle Fiber Structure

12. Skeletal Muscle Has Striations
Appearance is due to size and density differences between thick filaments and thin filaments.
Under the light microscope, two differently shaded bands are present.
The dark bands, called A bands, contain the entire thick filament.
At either end of a thick filament is a region where thin filaments extend into the A band between the stacked thick filaments.
Light bands, called I bands, contain thin filaments only.
I band is lighter shaded than an A band because only the thin filaments occupy this region.

13. Sarcomere: Organization of Fibers
Z disks
I band
A band
H zone
M line

14. Neuromuscular Junction
also known as myoneural junction
site where an axon and muscle fiber meet
motor neuron
motor end plate
synapse
synaptic cleft
synaptic vesicles
neurotransmitters

15. Motor Unit single motor neuron
all muscle fibers controlled by motor neuron

16. skeletal muscles Classification
By the way fascicles are organized
By relationships of fascicles to tendons
4 patterns of fascicle organization:
parallel
convergent
pennate
circular

17. Parallel Muscles Fibers parallel to the long axis of muscle
e.g., biceps brachii
The center or body of the muscle thickens when parallel muscle contracts
Parallel muscles contract about 30%

18. Convergent Muscles
A broad area converges on attachment site (tendon, aponeurosis, or raphe)
Muscle fibers pull in different directions, depending on stimulation
e.g., pectoralis muscles

19. Pennate Muscles Unipennate:
fibers on 1 side of tendon e.g., extensor digitorum
Bipennate:
fibers on both sides of tendon e.g., rectus femoris
Multipennate:
tendon branches within muscle e.g., deltoid

20. Circular Muscles Also called sphincters
Open and close to guard entrances of body
e.g., obicularis oris

21. Types of Contractions isotonic – muscle contracts and changes length
concentric – shortening contraction
isometric – muscle contracts but does not change length
eccentric – lengthening contraction

22. Descriptive Names or Skeletal Muscles
Location in the body-identifies body regions:
e.g., temporalis muscle
Origin and insertion-First part of name indicates origin, second part of name indicates insertion: e.g., genioglossus muscle
Fascicle organization-Describes fascicle orientation within muscle: i.e., rectus (straight), transversus, oblique
Relative position-
Externus (superficialis):visible at body surface
Internus (profundus):deep muscles
Extrinsic:muscles outside an organ
Intrinsic:muscles inside an organ
Structural characteristics
Number of tendons: bi = 2, tri = 3
Shape: trapezius, deltoid, rhomboid
Size
Action

23. Names for Muscle Size Longus = long Major = larger
Longissimus = longest
Teres = long and round
Brevis = short
Magnus = large
Major = larger
Maximus = largest
Minor = small
Minimus = smallest
Action
Movements:
e.g., flexor, extensor, retractor

24. Muscle Atrophy Reduction in muscle size, tone, and power.
Due to reduced stimulation, it loses both mass and tone.
Muscle becomes flaccid, and its fibers decrease in size and become weaker.
Even a temporary reduction in muscle use can lead to muscular atrophy.

25. Muscle Hypertrophy An increase in muscle fiber size.
Muscle size may be improved by exercising.
Repetitive, exhaustive stimulation of muscle fibers results in more mitochondria, larger glycogen reserves, and an increased ability to produce ATP.
Ultimately, each muscle fiber develops more myofibrils, and each myofibril contains a larger number of myofilaments.

26. Three Types of Skeletal Muscle Fibers
Fast
are large in diameter
contain large glycogen reserves
densely packed myofibrils
relatively few mitochondria
called white fibers due to lack of myoglobin
majority of skeletal muscle fibers in the body
Intermediate
resemble fast fibers; however
have a greater resistance to fatigue
Slow
smaller and they
contract more slowly
called red fibers because due to myoglobin

27. Posture
Maintaining the posture of the body is one of the major roles muscles play
“Good posture”—body alignment that most favors function and requires the least muscular work to maintain, keeping the body’s center of gravity over its base

28. Posture How posture is maintained
Muscles exert a continual pull on bones in the opposite direction from gravity
Structures and systems other than muscle and bones have a role in maintaining posture
Nervous system—responsible for determining muscle tone and also regulation and coordination of the amount of pull exerted by individual muscles
Respiratory, digestive, excretory, and endocrine systems all contribute to maintain posture

29. Cycle of Life: Muscular System
Life cycle changes—manifested in other components of functional unit
Infancy and childhood—coordination and controlling of muscle contraction permits sequential development steps
Degenerative changes of advancing age result in replacement of muscle cells with nonfunctional connective tissue
Diminished strength

30. Cycle of Life: Muscular System
Muscle cells—increase or decrease in number, size, and ability to shorten at different periods
Pathological conditions at different periods may affect the muscular system

31. Axial Muscles
Have both their origins and insertions on parts of the axial skeleton.
Support and move the head and spinal column.
Function in nonverbal communication by affecting facial features.
Move the lower jaw during chewing.
Assist in food processing and swallowing.
Aid breathing.
Support and protect the abdominal and pelvic organs.
Are not responsible for stabilizing or moving the pectoral or pelvic girdles or their attached limbs.

32. Appendicular Muscles
Control the movements of the upper and lower limbs.
Stabilize and control the movements of the pectoral and pelvic girdles.
Organized into groups based on their location in the body or the part of the skeleton they move.
Work in groups that are either synergistic or antagonistic.

33. Appendicular Muscles Organized into specific groups.
muscles that move the pectoral girdle
muscles that move the glenohumeral joint/arm
arm and forearm muscles that move the elbow joint/forearm
forearm muscles that move the wrist joint, hand, and fingers
intrinsic muscles of the hand

34. Intramuscular Injections
The gluteus maximus is a large, thick muscle with coarse Fasciculi that can be easily separated without damage.
The great thickness of this muscle makes it ideal for intramuscular Injections.
To avoid injury to the underlying Sciatic nerve, the injection should be given well forward On the upper outer quadrant of the buttock.

35. MOVEMENT—FLEXSION

36. MOVEMENT—EXTENSION

37. MOVEMENT—EXTENSION

38. MOVEMENT HYPEREXTENSION

39. MOVEMENT—DORSIFLEXION PLANTAR FLEXION

40. MOVEMENT—ABDUCTION ADDUCTION, CIRCUMDUCTION

41. MOVEMENT--ROTATION

42. MOVEMENT—SUPINATION PRONATION

43. MOVEMENT—INVERSION EVERSION

44. MOVEMENT—PROTRACTION RETRACTION

45. THE END