The skeletal system is divided into the axial skeleton and appendicular skeleton. The axial skeleton forms the body's central axis and includes the skull, vertebral column, and bony thorax. The skull is composed of two sets of bones - the cranium and facial bones. The cranium is made up of eight flat bones: the frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones.

1. ELAINE N. MARIEB
EIGHTH EDITION
5
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
PART A
The Skeletal System
Reporter: Ronald L. Rubi

2. Divided into two divisions
 Axial skeleton
 Appendicular skeleton
Parts of the skeletal system
 Bones (skeleton)
 Joints
 Cartilages
 Ligaments
The Skeletal System

3. Functions of the Bones
• Support of the body
• Protection of soft organs
• Movement due to attached skeletal
muscles
• Storage of minerals and fats
• Blood cell formation

4. • The adult skeleton has 206 bones
• Two basic types of osseous tissue
 Compact bone
Is dense and looks smooth
Homogenous
 Spongy bone
Small needle-like
pieces of bone
Many open spaces
Classification of Bones

5. Classification of Bones on the
Basis of Shape

6. Long bones
 Typically longer than wide
 Have a shaft with heads at both ends
 Contain mostly compact bone
• Examples: Femur, humerus
Classification of Bones

7. Short bones
 Generally cube-shape
 Contain mostly spongy bone
• Examples: Carpals, tarsals
Classification of Bones

8. Flat bones
 Thin and flattened
 Usually curved
 Thin layers of compact bone around a
layer of spongy bone
• Examples: Skull, ribs, sternum
Classification of Bones

9. Irregular bones
 Irregular shape
 Do not fit into other bone classification
categories
• Example: Vertebrae and hip
Classification of Bones

10. Gross Anatomy of a Long Bone
Diaphysis
 Shaft
 Composed of
compact bone
Epiphysis
 Ends of the bone
 Composed mostly of
spongy bone

11. Structures of a Long Bone
Periosteum
 Outside covering of
the diaphysis
 Fibrous connective
tissue membrane
Sharpey’s fibers
 Secure periosteum to
underlying bone
Arteries
 Supply bone cells
with nutrients

12. Articular cartilage
 Covers the external
surface of the
epiphyses
 Made of hyaline
cartilage
 Decreases friction at
joint surfaces
Structures of a Long Bone

13. Medullary cavity
 Cavity of the shaft
 Contains yellow
marrow (mostly fat) in
adults
 Contains red marrow
(for blood cell
formation) in infants
Structures of a Long Bone

14. 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

17. • Osteon (Haversian System)
– A unit of bone
• Central (Haversian) canal
– Opening in the center of an osteon
– Carries blood vessels and nerves
• Perforating (Volkman’s) canal
– Canal perpendicular to the central canal
– Carries blood vessels and nerves
Microscopic Anatomy of Bone

18. Microscopic Anatomy of Bone

19. Microscopic Anatomy of Bone
• Lacunae
– Cavities containing
bone cells
(osteocytes)
– Arranged in
concentric rings
• Lamellae
– Rings around the
central canal
– Sites of lacunae

20. Microscopic Anatomy of Bone
• Canaliculi
– Tiny canals
– Radiate from the
central canal to
lacunae
– Form a transport
system

21. Bone Formation, Growth and
Remodeling
• 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 Formation, Growth and
Remodeling
• Ossification
– is the process of bone formation
• It involves two major phases:
– First, the hyaline cartilage model is completely
covered with bone matrix by bone forming
cells called osteoblasts.
– Then, the enclosed hyaline cartilage model is
digested away, opening up a medullar cavity
within the newly formed bone.

23. Long Bone Formation
and Growth

24. How do bones widen?
• Osteoblasts in the periosteum add bone to the
external face of the diaphysis as osteoclasts
in the endosteum remove bone from the inner
face of the diaphysis wall.
• Appositional growth
- The process by which the bones increase
in diameter.

25. Formation and Growth of
Long Bones

26. • Bones are remodelled continually in
response changes in two factors:
Calcium levels in the blood
The pull of gravity and muscles on the
skeleton.

27. • 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
Types of Bone Cells

28. • Is essential if bones are retain normal
proportions and strength during long-bone
growth as the body increases in size and
weight.
• Bones become thicker and form large
projections to increase their strength in
areas where bulky muscles are attached.
Bone Remodeling

29. • A break in a bone
• Types of bone fractures
 Closed (simple) fracture- break that does
not penetrate the skin.
 Open (compound) fracture- broken bone
penetrates through the skin
• Bone fractures are treated by reduction or
immobilization
 Realignment of the bone
Bone Fractures

30. Bone Fractures

32. Type of Bone Fractures

33.  Hematoma (blood-filled swelling) is
formed.
 Break is splinted by fibrocartilage to form
a callus.
 Fibrocartilage callus is replaced by a
bony callus
 Bony callus is remodeled to form a
permanent patch.
Repair of Bone Fractures

34. 3. The bony callus forms
 As the more osteoblasts and osteoclasts
migrate into the area and multiply, the
fibrocartilage callus is gradually replaced by
one made of spongy bone the bony callus.
4. Bone remodeling occurs
 Over the next few weeks or months, the bony
callus is remodeled in response to the
mechanical stressed placed on it and it forms
a strong permanent “patch” at the fracture
sight.

36. Axial Skeleton
 Forms the longitudinal axis of the body
 Divided into three parts:
 Skull
 Vertebral column
 Bony thorax

37. The Skull
 Two sets of bones
 Cranium
 Facial bones
 Bones are joined by sutures
 Only the mandible is attached by a freely
movable joint.

38. Cranium
 The boxlike cranium is composed of eight
large flat bones.
 Frontal Bone- forms the forehead, the bony
projections under the eyebrows and the
superior part of each eye’s orbit.
 Parietal Bones- form most of the superior
and lateral walls of the cranium. They meet
in the midline of the skull at the sagittal
suture and form the coronal suture,
where they meet the frontal bone.

39. Cranium
 Temporal Bone- it lies inferior to the parietal
bones; they join them at the squamous
sutures.
 Occipital Bone- the most posterior part of the
cranium. It forms the floor and black wall of
the skull.
 Sphenoid Bone- the butterfly-shaped
sphenoid bone spans the width of the skull
and forms part of the floor of the cranial cavity.

40. Cranium
 Ethmoid Bone- is very irregularly shaped and
lies anterior to the sphenoid. It forms the roof
of the nasal cavity and part of the medial walls
of the orbits.