The skeletal system consists of bones, cartilage, and other connective tissues. It has several functions including support, protection, movement, blood cell formation, and mineral storage. There are different types of bones classified by shape, organization, and histological structure. Long bones have a shaft and two ends, while other bones like those in the skull are flat, irregular, or short. Cartilage is weaker but more flexible than bone and found in joints. The skeletal system includes the axial skeleton of the skull, vertebral column, ribs, and appendicular skeleton of shoulder, pelvis, and limbs.

1. The skeletal system
Dr. Mohammed Mahmoud Mosaed

2. Skeletal system
Skeletal system includes:
 bones of the skeleton
 Cartilage
 Ligaments
 other connective tissues that stabilize
or connect the bones.
Functions:
• Supports our weight.
• Interacts with muscles to produce
movements.
• Protection
• Blood cell formation
– Red bone marrow
• Mineral storage
– Calcium
– phosphate

3. Cartilage Connective Tissue
Characteristics:
– Weaker than bone
– More flexible than bone
• Cells in an abundant matrix.
• Cell Types
– Chondroblasts
– Chondrocytes in lacunae
• Avascular
Functions
• Supporting soft tissues.
• Providing a gliding surface at
articulations (joints)
• Providing a model for the formation
of most of the bones in the body.
6-3

4. Types of cartilage
• Three types of cartilage:
– Hyaline cartilage
• Most abundant kind
• Has a perichondrium(membrane)
• Associated with synovial joints
• Most bones first modeled in
hyaline cartilage
– Fibrocartilage
• Has collagen fibers
• Intervertebral discs, pubic
symphysis
– Elastic cartilage
• Has elastic fibers
• Ear, respiratory tubing

6. Bone
Bones are highly vascular living
structures that are
continuously being remodeled
They are a strong and durable
type of connective tissue
It consists of:
• water (25%)
• organic constituents
including osteoid and bone
cells (25%)
• inorganic constituents,
mainly calcium phosphate
(50%).

7. Functions of the bone
• Support.
• Protection.
• Movement
• Blood cell formation
– Red bone marrow contains stem
cells
– form all of the blood cell types.
• Mineral storage
– Calcium
– phosphate

8. Classification of Bone by Organization
• Axial
 Skull
 Vertebral column
 Bones of Thorax
• Sternum
• ribs
• Appendicular
• Bones of Shoulder girdle
• Bones of the upper limb
• Bones of Pelvic Girdle
• bones of lower limb

9. The Skull
• The skull is the bony framework of the head.
• It consists of the 8 cranial and 14 facial bones.
facialcranial
2 zygomatic
2 maxilla
2 nasal bones
2 lacrimal bones
1 vomer
2 palatine bones
2 inferior conchae
1 mandible
1 frontal bone,
2 parietal bones,
2 temporal bones,
1 occipital bone
1 sphenoid bone
1 ethmoid bone.

12. Fontanelles of the skull
• At birth, ossification of the cranial
sutures is incomplete. Where three or
more bones meet there are distinct
membranous areas, or fontanelles.
• The two largest fontanelles are:
• The anterior fontanelle between the
frontal and the 2 parietal bones, not fully
ossified until the child is 12 to 18 months
old.
• The posterior fontanelle between the 2
parietal and occipital bones usually
ossified 2 to 3 months after birth.
• The skull bones do not fuse before birth
to allow for moulding of the baby's head
during its passage through the birth
canal.
• Other 2 fontanelle: sphenoid
(anterolateral) and mastoid
(posterolateral)

13. VERTEBRAL COLUMN
The structure unit of The
vertebral column is the vertebra
The vertebral column consists of:
A) 24 separate movable, irregular
bones (vertebrae)
• 7 cervical, 12 thoracic and 5
lumbar.
B) The sacrum (five fused bones)
C) The coccyx (four fused bones),

14. Curves of the vertebral column
• The vertebral column in the adult
presents four curves:
• two primary; the thoracic and
sacral curves
• two secondary; the cervical and
lumber curves
• The secondary cervical curve
develops when the child can hold
up his head (after about 3
months) and the secondary
lumbar curve develops when he
stands upright (after 12 to 15
months).

15. THORACIC CAGE
• The bones of the thorax
or thoracic cage are:
• 1 sternum
• 12 pairs of ribs
• 12 thoracic vertebrae.

16. APPENDICULAR SKELETON
The appendicular skeleton
consists of:
• 1. The shoulder girdle (Scapula
and Clavicle) with the bonesof
upper limbs
• 2. The pelvic girdle (Hip Bones)
with the bones of lower limbs.

17. Shoulder girdle (pectoral) and upper limb
• Each shoulder girdle consists
of:
• 1 clavicle
• 1 scapula.
• Each upper limb consists of the
following bones:
• 1 humerus
• 1 radius
• 1 ulna
• 8 carpal bones
• 5 metacarpal bones
• 14 phalanges.

18. Pelvic girdle and lower limb
• The bones of the pelvic girdle
are:
• 2 hip bones
• 1 sacrum.
• The bones of the lower limb are:
• 1 femur
• 1 patella
• 1 tibia
• 1 fibula
• 7 tarsal bones
• 5 metatarsal bones
• 14 phalanges.

19. Types of bones
Bones are classified according to the shape into:
long, short, irregular, flat and sesamoid
• Long bones. These consist of a shaft and two extremities.
• the length is much greater than the width. Examples include
the femur, tibia and fibula.
• Short, irregular, flat and sesamoid bones. These have no
shafts or extremities and are diverse in shape and size.
• Examples include:
• short bones — carpals (wrist) and tarsal bones
• irregular bones—vertebrae and some skull bones
• flat bones — sternum, scapula, ribs and most skull bones
• sesamoid bones — patella (knee cap).

21. Types of bone according to histological
structures
• Compact bone: dense outer
layer
• Spongy bone: honeycomb of
trabeculae filled with yellow
bone marrow

22. Structure of Long Bone
• Long bones consist of a diaphysis
and an epiphysis
• Diaphysis
– Tubular shaft that forms the axis of
long bones
– Composed of compact bone that
surrounds the medullary cavity
– Yellow bone marrow (fat) is
contained in the medullary cavity
• Epiphyses
– Expanded ends of long bones
– Exterior is compact bone, and the
interior is spongy bone
– Joint surface is covered with
articular (hyaline) cartilage

23. Bone Membranes
• Periosteum – double-layered
protective membrane
– Outer fibrous layer is dense
regular connective tissue
– Inner osteogenic layer is
composed of osteoblasts and
osteoclasts
– Richly supplied with nerve fibers,
blood, and lymphatic vessels,
which enter the bone via
nutrient foramina
– Secured to underlying bone by
Sharpey’s fibers
• Endosteum – delicate membrane
covering internal surfaces of bone

24. Structure of Long Bone
Figure 6.3

25. Flat Bones of the Skull
• Two layers of compact
bone
– Inner table
– Outer table
• Region of spongy bone
sandwiched between
them called the diploe
• Both layers of compact
bone are covered by
periosteum