Bones and Skeletal Tissues
Part A
Skeletal Cartilages



Consist primarily of water this is what allows it to
spring back to its original shape after being compressed.
Contain no blood vessels or nerves
Surrounded by dense connective tissue, the
perichondrium


contains blood vessels for nutrient delivery to cartilage
acts as a girdle to resist outward expansion
Skeletal Cartilages
Hyaline cartilages
1.


Provide support, flexibility, and resilience
Most abundant type
Elastic cartilages
2.



Similar to hyaline cartilages, but contain more stretchy elastic
fibers
Better able to stand up to repeated bending
Only found in the external ear and the epiglottis
Fibrocartilages
3.


Collagen fibers—have great tensile strength
Areas subjected to heavy pressure and stretch- menisci (knee)
Cartilage in
external ear
Cartilage in
Intervertebral
disc
Cartilages in
nose
Articular
Cartilage
of a joint
Epiglottis
Thyroid
cartilage
Cricoid
cartilage
Larynx
Trachea
Lung
Costal
cartilage
Respiratory tube cartilages
in neck and thorax
Pubic
symphysis
Meniscus (padlike
cartilage in
knee joint)
Articular cartilage
of a joint
Bones of skeleton
Axial skeleton
Appendicular skeleton
Cartilages
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Figure 6.1
Growth of Cartilage

Cartilage grows in two ways:

Appositional “growth from the outside”


Interstitial “growth from the inside”


Cells secrete matrix against the external face of existing cartilage
Chondrocytes divide and secrete new matrix, expanding cartilage
from within
Under certain conditions calcification of cartilage (calcium salts
are deposited in the matrix) occurs during



Normal bone growth
Old age
THIS IS NOT BONE 2 separate tissues!
Bones of the Skeleton

Two main groups, by location

Axial skeleton (brown)


Skull, vertebral column, and rib cage
Appendicular skeleton (yellow)

Bones of the upper and lower limbs and the girdles.
Cartilage in
external ear
Cartilage in
Intervertebral
disc
Cartilages in
nose
Articular
Cartilage
of a joint
Costal
cartilage
Pubic
symphysis
Meniscus
(padlike
cartilage in
knee
joint)
Articular
cartilage
of a joint
Figure 6.1
Classification of Bones by Shape

Long bones



Longer than they are wide
All limb bones except the
patella, wrist, and ankle
bone are long bones.
Short bones


Cube-shaped bones (in
wrist and ankle)
Sesamoid bones (within
tendons  patella)
Classification of Bones by Shape

Flat bones



Thin, flat, slightly curved
Sternum, scapulae, ribs,
and most skull bones
Irregular bones


Complicated shapes that
fit none of the other
classes
Vertebrae and hip bones
Functions of Bones

Support


Protection


For the body and soft organs (framework)
For brain, spinal cord, and vital organs
Movement

Levers for muscle action muscles use bones as levers to
move the body.
Functions of Bones

Storage



Minerals (calcium and
phosphorus) and growth
factors
Blood cell formation
(hematopoiesis) in marrow
cavities
Triglyceride (energy)
storage in bone cavities
Bone Markings

Bulges, depressions, and holes serve as



Sites of attachment for muscles, ligaments, and tendons
Joint surfaces
Channels for blood vessels and nerves
Bone Markings: Projections
Table 6.1
Bone Markings: Projections

Projections (grow outward from bone surface) that help
to form joints
Bone Markings: Depressions and Openings
Bone Textures

Compact bone


Dense outer layer that looks smooth and solid
Spongy bone

Honeycomb of trabeculae internal layer filled with bone
marrow
Structure of a Long Bone

Diaphysis (shaft)



Forms the long axis of the
bone
Constructed from a thick
compact bone collar that
surrounds a central
medullary (marrow) cavity
Medullary cavity in adults
contains fat (yellow marrow)
Structure of a Long Bone

Epiphyses



Bone ends
Compact bone exterior & spongy
bone interior
Epiphyseal line


remnant of growth plate- a disc of hyaline
cartilage that grows during childhood to
lengthen the bone
Articular (hyaline) cartilage on joint
surfaces
Articular
cartilage
Proximal
epiphysis
Compact bone
Spongy bone
Epiphyseal
line
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
(b)
Diaphysis
Distal
epiphysis
(a)
Figure 6.3a-b
Membranes of Bone

Periosteum





Covers the entire external surface of bones
Outer fibrous layer dense irregular
connective tissue
Inner osteogenic layer mainly bone forming
cells
Nerve fibers, nutrient blood vessels, and
lymphatic vessels enter the bone via nutrient
foramina
Secured to underlying bone by perforating
“Sharpey’s” fibers

Tufts if collagen fibers that extend from the fibrous
layer into the bone matrix
Membranes of Bone

Endosteum



Delicate connective tissue
membrane on internal surfaces
of bone
Covers the trabeculae of
spongy bone and lines the
canals that pass through
compact bone
Also contains osteoblasts and
osteoclasts
Structure of Short, Irregular, and Flat
Bones

All consist of:




Periosteum-covered compact bone on the outside
Endosteum-covered spongy bone within
Spongy bone called diploë in flat bones
Bone marrow between the trabeculae
Location of Hematopoietic Tissue (Red
Marrow)


Red marrow cavities of adults
 Trabecular cavities of the heads of the femur and humerus
 Trabecular cavities of the diploë of flat bones
 In most adult long bones the fat containing medullary cavity
extends well into the epiphysis and little red marrow is present
 blood cell production occurs in the heads of the femur (thigh
bone) and humerus (long bone of arm)
 The red marrow found in the diploë of flat bones (sternum) or
some irregular bone (hip) is much more active in
hematopoiesis and these sites are routinely used for obtaining
bone marrow biopsies when problems with blood forming
tissue are suspected.
Red marrow of newborn infants
 Medullary cavities and all spaces in spongy bone
Microscopic Anatomy of Bone

Cells of bones


Osteogenic cells

Stem cells in periosteum
and endosteum that give
rise to osteoblasts
Osteoblasts


Osteocytes


Bone-forming cells
Mature bone cells
Osteoclasts

Cells that break down bone
matrix
Microscopic Anatomy of Bone: Compact
Bone


Although compact bone looks
solid it is riddled with
passageways for nerves, blood
vessels, and lymphatic vessels
Osteons—structural units


“Tiny pillars”
Lamellae



Weight-bearing
Column-like matrix tubes
Haversian canal

Contains blood vessels and nerves
Microscopic Anatomy of Bone: Compact
Bone

Perforating (Volkmann’s) canals




At right angles to the central
canal
Connects blood vessels and
nerves of the periosteum and
central canal
Lacunae—small cavities that
contain osteocytes
Canaliculi—hairlike canals that
connect lacunae to each other
and the central canal
Microscopic Anatomy of Bone: Spongy Bone

Trabeculae




Align along lines of stress
No osteons
Contain irregularly arranged lamellae, osteocytes, and canaliculi
Capillaries in endosteum supply nutrients
Chemical Composition of Bone: Organic


Osteogenic cells, osteoblasts, osteocytes, osteoclasts
Osteoid—organic bone matrix secreted by osteoblasts


Ground substance (proteoglycans, glycoproteins)
Collagen fibers

Provide strength and flexibility
Chemical Composition of Bone: Inorganic

Hydroxyapatites (mineral salts)




Tiny, tightly packed crystals in and around the collagen fibers in
the extracellular matrix
65% of bone by mass
Mainly calcium phosphate crystals
Responsible for hardness and resistance to compression