The document provides an overview of the skeletal and muscular systems. It discusses the bones and classification of bones, including long bones, short bones, flat bones, and irregular bones. It also reviews the microscopic structure of bone. Additionally, it examines the three types of muscle tissue - skeletal, cardiac, and smooth muscle - and provides details on the structure, organization and sliding filament theory of contraction of skeletal muscle.

1. CLS 224
(Basic Anatomy & Physiology)
Lecture 9: Skeletal and Muscular Systems
Contents:
The Skeletal System:
1. Bones: An Overview
The Muscular System:
1. Overview of Muscle Tissues
2. Microscopic Anatomy of Skeletal Muscle
3. Skeletal Muscle Activity

2. The Skeletal System

3. Objectives:
•List the functions of the skeletal system.
•Identify the subdivisions of the skeleton as axial or
appendicular.
•Name the four main classifications of bones.
Bones: An Overview

4. Functions of Bones:
 Support of the body
 Protection of soft organs
 Movement due to attached skeletal
muscles
 Storage of minerals and fats
 Blood cell formation (hematopoiesis)

5. The Skeletal System
 Parts of the skeletal system
a. Bones (skeleton)
b. Joints
c. Cartilages
d. Ligaments
 Divided into two divisions
1. Axial skeleton
2. Appendicular skeleton

6. Bones: An Overview

7. Bones of the Human Body
 The skeleton has 206 bones
Classification of Bones:
 Two basic types of bone (osseous)
tissue
1. Compact bone
 Homogeneous
2. Spongy bone
 Small needle-like
pieces of bone
 Many open spaces

8. Classification of Bones
A. Long bones
Typically longer than wide
Have a shaft with heads at both ends
Contain mostly compact bone
Examples: Femur, humerus
B. Short bones
Generally cube-shape
Contain mostly spongy bone
Examples: Carpals, tarsals

9. Classification of Bones
C. Flat bones
 Thin and flattened
 Usually curved
 Thin layers of compact bone around a layer
of spongy bone
Examples: Skull, ribs, sternum
D. Irregular bones
 Irregular shape
 Do not fit into other bone classification categories
Example: Vertebrae and hip

10. Classification of Bones on the Basis of Shape

11. Gross Anatomy of a Long Bone
1. Diaphysis
Shaft
Composed of
compact bone
2. Epiphysis
Ends of the bone
Composed mostly of
spongy bone
Structure of Bone

12. 3. Periosteum
 Outside covering of the
diaphysis
 Fibrous connective
tissue membrane
4. Sharpey’s fibers
 Secure periosteum to
underlying bone
5. Arteries
 Supply bone cells with
nutrients
Structure of Bone
Gross Anatomy of a Long Bone

13. Structure of Bone
Gross Anatomy of a Long Bone
5. Articular cartilage
 Covers the external surface of the
epiphyses
 Made of hyaline cartilage
 Decreases friction at joint surfaces
6. Medullary cavity
 Cavity of the shaft
 Contains yellow marrow (mostly fat) in
adults
 Contains red marrow (for blood cell
formation) in infants

14. Structure of Bone

15. Bone Markings
 Surface features of bones
 Sites of attachments for muscles, tendons, and
ligaments
 Passages for nerves and blood vessels
 Categories of bone markings
Projections and processes – grow out from the
bone surface
Depressions or cavities – indentations
Structure of Bone

16. Microscopic Anatomy of Bone
1. Osteon (Haversian System)
 A unit of bone
2. Central (Haversian) canal
 Opening in the center of an osteon
 Carries blood vessels and nerves
3. Perforating (Volkman’s) canal
 Canal perpendicular to the central canal
 Carries blood vessels and nerves
Structure of Bone

17. Microscopic Anatomy of Bone
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

18. Microscopic Anatomy of Bone
Structure of Bone
4. Lacunae
 Cavities containing bone cells
(osteocytes)
 Arranged in concentric rings
5. Lamellae
 Rings around the central canal
 Sites of lacunae
6. Canaliculi
 Tiny canals
 Radiate from the central canal to lacunae
 Form a transport system

19. Microscopic Anatomy of Bone
Structure of Bone

20. Microscopic Anatomy of Bone
Structure of Bone
Types of Bone Cells
 Osteocytes
Mature bone cells
 Osteoblasts
Bone-forming cells
 Osteoclasts
Bone-destroying cells
Break down bone matrix
for remodeling and
release of calcium
 Bone remodeling is a process by both osteoblasts and
osteoclasts

21. Changes in the Human Skeleton
 In embryos, the skeleton is primarily hyaline
cartilage
 During development, much of this cartilage
is replaced by bone
 Cartilage remains in isolated areas
 Bridge of the nose
 Parts of ribs
 Joints

22. Bone Growth
 Epiphyseal plates allow for growth of long
bone during childhood
 New cartilage is continuously formed
 Older cartilage becomes ossified
Cartilage is broken down
Bone replaces cartilage
 Bones are remodeled and lengthened until
growth stops
 Bones change shape somewhat
 Bones grow in width

23. Long Bone Formation and Growth

24. Long Bone Formation and Growth

25. The Muscular System

26. Objectives:
•Describe similarities and differences in the structure
and function of the three types of muscle tissue, and
indicate where they are found in the body.
•Define muscular system.
•Define and explain the role of the following:
endomysium, perimysium, epimysium, tendon, and
aponeurosis.
The Muscular System

27. Function of Muscles
 Produce movement
 Maintain posture
 Stabilize joints
 Generate heat

28. Characteristics of Muscles
 Muscle cells are elongated
(muscle cell = muscle fiber)
 Contraction of muscles is due to the
movement of microfilaments
 All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh

29. The Muscular System
 Muscles are responsible for all types of
body movement
 Three basic muscle types are found
in the body:
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle

30. Skeletal Muscle Characteristics
 Most are attached by tendons to bones
 Cells are multinucleate
 Striated – have visible banding
 Voluntary – subject to con-scious control
 Cells are surrounded and bundled by
connective tissue

31. Cardiac Muscle Characteristics
 Has striations
 Usually has a
single nucleus
 Joined to another
muscle cell at an
intercalated disc
 Involuntary
 Found only in the
heart

32. Smooth Muscle Characteristics
Slide 6.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Has no striations
 Spindle-shaped
cells
 Single nucleus
 Involuntary – no
conscious control
 Found mainly in
the walls of hollow
organs

34. Connective Tissue Wrappings of
Skeletal Muscle
 Endomysium –
around single muscle
fiber
 Perimysium – around
a fascicle (bundle) of
fibers
 Epimysium – covers the
entire skeletal muscle
 Fascia – on the outside of
the epimysium

35. Skeletal Muscle Attachments
Slide 6.5
 Epimysium blends into a connective
tissue attachment
1. Tendon – cord-like structure
2. Aponeuroses – sheet-like structure
 Sites of muscle attachment
1. Bones
2. Cartilages
3. Connective tissue coverings

36. Microscopic Anatomy of Skeletal Muscle
 Cells are multinucleate
 Nuclei are just beneath the sarcolemma
 Sarcolemma – specialized plasma membrane
 Sarcoplasmic reticulum – specialized smooth
endoplasmic reticulum

37.  Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distrinct bands
I band =
light band
A band =
dark band
Microscopic Anatomy of Skeletal Muscle
 Sarcomere
Contractile unit of
a muscle fiber

38. Organization of the sarcomere
a. Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Microscopic Anatomy of Skeletal Muscle
b. Thin filaments = actin filaments
Composed of the protein actin

39.  Myosin filaments have heads (extensions,
or cross bridges)
 Myosin and actin overlap somewhat
Microscopic Anatomy of Skeletal Muscle
 At rest, there is a bare zone that lacks actin
filaments
 Sarcoplasmic
reticulum
(SR) – for
storage of
calcium

41. Properties of Skeletal Muscle Activity
 Irritability (excitability) – ability to receive
and respond to a stimulus
 Contractility – ability to shorten when an
adequate stimulus is received
 Extensibility: ability to be stretched
 Elasticity – ability to recoil to resting
length

42. Nerve Stimulus to Muscles
 Skeletal
muscles must
be stimulated
by a nerve to
contract
 Motor unit
One neuron
Muscle cells
stimulated by
that neuron

43. Nerve Stimulus to Muscles
 Neuromuscular
junctions – association
site of nerve and
muscle
 Synaptic cleft – gap
between nerve and
muscle
Nerve and muscle do
not make physical
contact
Area between nerve
and muscle is filled
with interstitial fluid

44. Transmission of Nerve Impulse to Muscle
 Neurotransmitter – chemical released by nerve upon
arrival of nerve impulse
 The neurotransmitter for skeletal muscle is acetylcholine
 Neurotransmitter attaches to receptors on the
sarcolemma
 Sarcolemma becomes permeable to sodium (Na+)
 Sodium rushing into the cell generates an action potential
 Once started, muscle contraction cannot be stopped

45. The Sliding Filament Theory of Muscle
Contraction
 Activation by nerve causes myosin heads (cross-
bridges) to attach to binding sites on the thin
filament
 Myosin heads then bind to the next site of the thin
filament
 This continued action causes a sliding of the myosin
along the actin
 The result is that the muscle is shortened
(contracted)

46. The Sliding Filament Theory of Muscle Contraction

47. References: