Skeletal System BSN YEAR 1 SEMSESTER 1..

The Skeletal System
By
Syed Yousaf Shah

• At the completion of this unit, learners will
be able to:
1. Define skeletal system
2. Discuss the structure, types and functions
of bone
3. List the functions of the skeletal system
4. Identify the bones of axial & appendicular
skeleton
Objectives

5. Describe the various markings on the surface of bones.
6. Describe the bones of:
The skull
Vertebral column
The rib cage or chest
Pectoral girdle and upper extremity
Pelvic girdle and lower extremity
7. Briefly discuss the difference between male & female pelvis.
Objectives

The Human skeleton
• The framework of the body, consisting of
bones and other connective tissues, which
protects and supports the body tissues and
internal organs.

The Skeletal System
 Parts of the skeletal system
 Bones (skeleton)
 Joints
 Cartilages
 Ligaments (bone to bone)(tendon=bone to
muscle)
 Divided into two divisions
 Axial skeleton
 Appendicular skeleton – limbs and girdle

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

Bones of the Human Body
 The skeleton has 206 bones
 Two basic types of bone tissue
Compact bone
 Homogeneous
Spongy bone
 Small needle-like
pieces of bone
 Many open spaces

Bones are classified by
their shape:
1.long
2.short
3.flat
4.irregular

Classification of Bones on the
Basis of Shape

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

Gross Anatomy of a Long Bone
 Diaphysis
Shaft
Composed of
compact bone
 Epiphysis
Ends of the bone
Composed mostly of
spongy bone

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

 Short bones
Generally cube-shape
Contain mostly spongy bone
Examples: Carpals, tarsals

 Flat bones
Thin and flattened
Usually curved
Thin layers of compact bone around a layer
of spongy bone
Examples: Skull, ribs, sternum

 Irregular bones
Irregular shape
Do not fit into other bone classification
categories
Example: Vertebrae and hip

 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

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

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

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

Bone Fractures
 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
and immobilization
 Realignment of the bone

Stages in the Healing of a Bone
Fracture

Axial skeleton supports and protects organs of head,
neck and trunk
Axial skeleton:
skull (cranium and facial bones)
hyoid bone (anchors tongue and muscles
associated with swallowing)
vertebral column (vertebrae and disks)
bony thorax (ribs and sternum)
Appendicular skeleton includes bones of limbs and
bones that anchor them to the axial skeleton
Appendicular skeleton:
pectoral girdle (clavicles and scapulae)
upper limbs (arms)
pelvic girdle (sacrum, coccyx)
lower limbs (legs)
Articulation- where joints meet, connect, and are formed.

22 bones in skull
6 in middle ears
1 hyoid bone
26 in vertebral column
25 in thoracic cage
4 in pectoral girdle
60 in upper limbs
60 in lower limbs
2 in pelvic girdle
206 bones in all

The Axial Skeleton
 Forms the longitudinal part of the body
 Divided into three parts
Skull
Vertebral column
Bony thorax

The skull
8 sutured bones in cranium
Facial bones: 13 sutured bones, 1 mandible
Cranium
encases brain
attachments for muscles
sinuses

Human Skull, Inferior View
Figure 5.9

Paranasal Sinuses
 Hollow portions of bones surrounding
the nasal cavity

The Hyoid Bone
 The only bone that
does not articulate
with another bone
 Serves as a
moveable base for
the tongue

The Vertebral Column
 Vertebrae
separated by
intervertebral discs
 The spine has a
normal curvature
 Each vertebrae is
given a name
according to its
location

Vertebral column
7 cervial vertebrae
12 thoracic
5 lumbar
1 sacrum (5 fused
1 coccyx (4 fused)
Vertebrae vary in size and morphology

Structure of a Typical Vertebrae

Thoracic cage
ribs
thoracic vertebrae
sternum
costal cartilages
True ribs are directly attached to the sternum
(first seven pairs)
Three false ribs are joined to the 7th rib
Two pairs of floating ribs

Difference Between Male &
Female Pelvis
• The pelvis is one of the most useful skeletal
elements for differentiating between males
and females.
• Female pelves are larger and wider than
male pelves and have a rounder pelvic inlet.
• Male iliac crests are higher than females,
causing their false pelves to look taller and
narrower

Skeletal System BSN YEAR 1 SEMSESTER 1..

Skeletal System BSN YEAR 1 SEMSESTER 1..

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