1. The Skeletal System An overview
Includes:
Bones – structure, protection and support
Joints – for flexibility and allow motion
Cartilages and Ligaments – Hold bones together

2. The Skeletal System . . . The Body’s Framework in 2 parts
The human skeleton consists of
two main divisions:
Axial skeleton – forms the upright
axis of the body (74 bones + 6 tiny
bones of the middle ear)
Appendicular skeleton – forms the
Appendages of the upper and
Lower body (126 bones)
The limbs and pelvic girdle
Total # = 206 bones in the human
adult skeleton

3. Five General Functions of Bone
Support – bones contribute to shape, alignment and
positioning of the body parts
Protection – bones act as hard “boxes” to protect the
delicate structures they enclose
Movement – bones with their joints constitute levers;
muscle tissue attached to the bones contract, pulling on
bones and producing movement
Mineral storage – bones serve as a major reservoir for
calcium, phosphorus and certain other minerals needed
for essential healthy survival
Hematopoiesis (blood cell formation) – a vital process
that takes place in red bone marrow, myeloid tissue

4. Structurally, there are four types of bones:
Long bones
Short bones
Flat bones
Irregular bones
The structural function of a bone is determined by
its size, shape, location, appearance and constitutional
makeup

5. TYPICAL LONG BONE STRUCTURE OF Prepare your Color Plate
of the Femur, outlining the
structures that are seen
here

6. The periosteum is a dense, white fibrous membrane that covers bone; it
attaches tendons firmly to bones
contains blood vessels that send branches into bone
is essential for bone cell survival and bone formation

7. The medullary (or marrow) cavity: tubelike, hollow space in diaphysis
Medullary cavity
The medullary (or marrow) cavity:
tubelike, hollow space in diaphysis
filled with yellow marrow

8. BONE GROWTH AND EARLY DEVELOPMENT
Parts of the skeletal system begin to form during the first few weeks of
life, and bony structures continue to develop and grow into adulthood.
bones form by the replacement of existing connective tissues in one of
two ways:
1. Intramembranous Bones
examples are the broad,
flat bones of the skull . . .
during their development,
sheetlike masses of
connective tissues appear
at the sights of future bone
Some of the connective
tissues enlarge and
differentiate to form
osteoblasts
Spongy bone then forms,
growing outward in all
directions building a bony
matrix

9. Mesenchyme cells cluster together
2. Endochondral Bone
Most of the bones of the skeleton are of this type and are formed from
masses of hyaline cartilage with shapes similar to the future bony
structure.
Mesenchyme cells cluster together
and transform into osteoblasts . . .
Osteoblasts secrete boney matrix
until cells are surrounded
surrounded osteoblasts become
osteocytes that reside in lacunae
within the matrix . . .calcium and
mineral salts are deposited rapidly
the bone matrix develops into
columns of bone called trabeculae
that fuse together to form spongy
bone
red marrow forms in the spaces
between the trabeculae
Double-click on the title of this page to observe a virtual ossification process

10. The skull of the neonate is not one sealed container,
but a collection of plates, attached by flexible cartilage. . .
Areas where there is a considerable distance between the skull
plates are called fontanelles. There are 4 main fontanelles; the
most common of which is the anterior fontanelle called the
“soft spot”.

11. There are 2 reasons for this arrangement of skull plates in
the fetus:
the separations allow shifting and movement of these plates
as the baby navigates the mother’s birth canal, allowing a
shape that facilitates molding the head to a shape where the
baby can deliver
At birth the brain doesn’t stop growing. . . This arrangement
of skull plates gives considerable slack so that the skull can
expand outward as the brain grows

12. Later Bone Development
Throughout childhood, the epiphyses of developing long bones remains cartilaginous and continue to grow. . . As we reach adulthood, secondary ossification centers appear in the epiphyses, leaving an epiphyseal line where the two areas were once separated
Young children often have a “greenstick” fracture in a bone rather
than a complete break because the cartilage leaves the bone more
resilient
A break along the epiphyseal disk in a young
child can result in an interference of growth
in that bone

13. EPIPHYSEAL
LINES

14. BONE TEXTURES: COMPACT AND SPONGY BONE
BONE TISSUE STRUCTURE
BONE TEXTURES: COMPACT AND SPONGY BONE
- The dense outer layer that appears smooth and solid
to the naked eye is compact bone
- The internal area of the bone is called spongy bone
(also called cancellous bone) It appears as a
honeycomb of small needle-like or flat pieces called
trabeculae (“little beams”). In living bones, the open
spaces between trabeculae are filled with red or yellow
bone marrow.
Compact bone
Spaces containing
red marrow
trabeculae

16. Endosteum
The endosteum is the thin epithelial tissue that
lines the medullary cavity

17. COMPOSITION OF BONE TISSUE – THE MOST DISTINCTIVE
FORM OF CONNECTIVE TISSUE
Extracellular components are hard and calcified
Apatite – highly specialized chemical crystals of
calcium and phosphate contribute to bone
hardness
slender needle-like crystals are oriented to effectively
resist stress and mechanical deformation
magnesium and sodium are also found in bone

18. Organic matrix of bone:
composite of collagenous fibers and an amorphous mixture
of protein and polysaccharides (ground substance)
ground substance substance secreted by connective tissue
cells
adds to overall strength and resilience of bones

19. Osteon/Haversian System

20. Cancellous (spongy or trabecular) bone:
characterized by open spaces
partially filled by an assemblage of
needlelike spicules called
(trabeculae)
no osteons are present
bone cells are found within the
trabeculae
nutrients are delivered to cells, and
waste products removed, by
diffusion through tiny canaliculi that
extend to the surface of the very
thin spicules
found in the epipyses of long bones
this type of bone greatly enhances
the bone’s strength

21. Bone Marrow – A Production Factory

22. Bone marrow is a specialized type of soft, diffuse
connective tissue called myeloid tissue
It serves as the site for production of blood cells
It is found in the medullary cavities of long bones and
in the spaces of spongy bone
During the lifetime of an individual, two types of marrow occur:
Red Marrow – its function is production of red blood cells; in an
infant or young child, virtually all bones contain red marrow
Yellow Marrow – cells are saturated with fat, rendering them
inactive in blood cell production; red marrow is replaced by
yellow marrow as a person ages

23. Hip Replacement
Click on the picture to see video

24. In the adult, the main locations of red marrow are the ribs, iliac crests, bodies of the vertebrae, and the epiphyses of long bones During times of decreased blood supply (prolonged anemia, blood loss, exposure to radiation or chemotherapy), yellow marrow can alter to become red marrow
Bone Marrow Transplant
In patients with leukemia, aplastic anemia,
Hodgkin’s disease (lymphomas) and some immune deficiency diseases, stem cells in the bone marrow malfunction and produce
Immature or defective blood cells.
Marrow transplant may help these patients.
Their own marrow is destroyed by radiation or chemotherapy; they then receive an infusion of donated marrow. . . In successful
transplants, the marrow migrates to cavities of large bones and begins producing
normal blood cells

25. Bone Fractures Fractures are breaks in bone and can
be divided into 3 general categories:
Incomplete (often called “greenstick”
fractures) – a bending of the bone; most
often seen in children whose bones have
not been completely ossified by calcium
deposits
Simple (nondisplaced, transverse) – bone
is broken at a right angle to the bone’s
axis and is “in line” with the corresponding
part (may also be simple oblique fracture)
Compound (open) – bone is usually
broken obliquely and breaks through the skin

26. SCOLIOSIS
KYPHOSIS
LORDOSIS

27. Bone Markings
Bumps, holes, ridges or grooves for muscle attachment and blood vessel and nerves to pass through.
2 Categories of Markings
Projections or Process are raised. Depressions or Cavities are not raised. Know these….
Angle body condyle epicondyle
Crest tuberosity suture foramen Tubercle
Fossa head line margin trochanter
Meatus process notch sinus spine
Look up the meanings for these markings in your book.

28. Synovial Joints (Diarthroses) Freely movable
Most numerous of the body’s joints
Examples:
Uniaxial Biaxial
Hinge joint (elbow) Saddle joint thumb joint)
Pivot joint (atlas & axis) Condyloid (ellipsoidal) joint (wrist)
Multiaxial
Ball and socket (shoulder and hip) Gliding (between vertebrae; tarsals/carpals)