Chapter Six – Osseous Tissue and Bone Structure
The skeletal system includes the bones of the skeleton and the cartilages, ligaments, and other connective tissues that stabilize
or connect the bones.
Six primary functions of the skeletal system:
Bones are classified by: shape, bone markings, and internal tissue organization
A. Shape – There are 6 main shapes
1. Long bones
2.
Flat bones
3.
Sutural bones
4.
Irregular bones
5.
Short bones
6.
Sesamoid bones
B. Bone Markings (Surface features)
 Depressions or grooves
 Along bone surface
 Projections
 Where tendons and ligaments attach
 At articulations with other bones
 Tunnels
 Where blood and nerves enter bone
General description
Elevation and Project
Anatomical term
Process
Ramus
Processes formed where
tendons or ligaments attach
Trochanter
Processes formed for
articulation with adjacent
bones
Definition
Any projection or bump
An extension of a bone making an angle with the
rest of the strucuture.
A large, rough projection
Tuberosity
Tubercle
Crest
Line
Spine
Head
A smaller, rough projection
A small, rounded projection
A prominent ridge
A low ridge
A pointed process
The expanded articular end of an epiphysis,
separated from the shaft by a neck.
Neck
A narrow connection between the epiphysis and
the diaphysis.
Condyle
Trochlea
Facet
Fossa
Sulcus
Foramen
Depressions
Openings
Canal
Fissure
Sinus or antrum
A smooth, rounded articular process
A smooth, grooved articular process shaped like a
pulley
A small, flat articular surface
A shallow depression
A narrow groove
A rounded passageway through the substance of a
bone
A passageway through the substance of a bone
An elongate cleft
A chamber within a bone, normally filled with air
Two main types of bone
1. Compact
2. Spongy
Bone Structure of a Long Bone
Diaphysis
Epiphysis
Medullary Cavity
Epiphyseal Line
Bone Structure of a Flat Bone
Resembles a “spongy bone sandwich” in that it has a layer of compact bone
covering each side of the spongy bone
Although bone marrow is present within the spongy bone, there is no marrow
cavity.
C. Internal Tissue Organization
Characteristics of Bone Tissue
Matrix
Canaliculi
Periosteum
Bone Matrix is made of the following:
 Calcium phosphate

Collagen fibers
The Cells of Bone
Bone contains four types of cell: osteocytes, osteoblasts, osteoprogenitor cells, and osteoclasts.
1. Osteocytes
2. Osteoblasts
3. Osteoprogenitor Cells
4.
Osteoclasts
Bone Homeostasis
The Structure of Compact Bone
Osteon
Haversian canal
Volkmann canals (Perforating)
Lamellae
Concentric
Interstitial
Circumferential
Good for heavy stress in one direction. Can not withstand much pressure in a different direction.
The Structure of Spongy Bone
No osteons & no blood vessels
Trabeculae
Space between trabeculae is filled with:
Red bone marrow
Yellow bone marrow
Located where bones are not heavily stressed and where stress
arrives in many different directions.
Periosteum
Location
Sharpey’s fibers (Perforating fibers)
Functions include:
Endosteum
Location
Function
.
It consists of a simple flattened layer of osteoprogenitor cells
that cover the bone matrix. Where the cellular layer is not complete, the matrix is exposed so steoclasts and osteoblasts
can remove or deposit matrix components.
Howship’s lacunae
Bone Formation and Growth
The bony skeleton begins to form about six weeks after fertilization and
continues through adolescence. Portions of the skeleton do not stop
growing until about the age of 25.
Osteogenesis –
Ossification -
Calcification -
There are two types of ossification- endochondral and intramembranous
ossification
Endochondral Ossification
During development, most bones originate as hyaline cartilage and are converted to bone through endochondral ossification
The cartilage can grow by expansion of the cartilage matrix (interstitial growth) and the production of new cartilage at the
outer surface (appositional growth).
There are six steps to this process:
Appositional Growth
A superficial layer of bone forms early in endochondral ossification. Once this occurs, the bone is able to increase its diameter
through appositional growth at the outer surface. In this process, cells of the inner layer of the periosteum differentiate into
osteoblasts and deposit superficial layers of bone matrix. Eventually, these cells become surrounded by matrix and
differentiate into osteocytes. Appositional growth forms a series of layers that form circumferential lamellae.
Epiphyseal Lines
Mature Bones
Intramembranous Ossification
Begins when osteoblasts differentiate within a mesenchymal or fibrous connective tissue.
Also called dermal ossification because it normally occurs in the deeper layers of the dermis.
The bones that result are called dermal bones.
Examples include flat bones of the skull, mandible, and the clavicle.
Three main steps:
The Blood and Nerve Supplies
Osseous tissue is highly vascular, and the bones of the skeleton have an extensive blood supply.
There are three major set of blood vessels in bone:
1. The Nutrient Artery and Vein
2. Metaphyseal Vessels
3. Periosteal Vessels
Bone Remodeling
The organic and mineral components of the bone matrix are continuously
being recycled and renewed through the process of remodeling.
Remodeling can replace the matrix but leave the bone as a whole
unchanged, or it may change the change, internal architecture, or mineral
content of the bone.
In regards to exercise the phrase “what you don’t use, you lose” is a
reality. The stresses applied to bones during physical activity are essential
to maintaining bone strength and bone mass.
Bones get stronger –
Bones get weaker Normal bone growth and maintenance requires nutritional and hormonal
factors

A dietary source of ______________ and
__________________
 Plus small amounts of magnesium, fluoride,
iron, and manganese

The hormone __________________
 Is made in the kidneys
 Helps absorb calcium and phosphorus from digestive tract
 Synthesis requires vitamin D3 (cholecalciferol)
Abnormal bone growth and development
Dwarfism
Gigantism
Acromegaly
Marfan’s Syndrome
Calcium
Calcium is the most abundant mineral in the human body, and it
plays a role in a variety of physiological processes. Therefore,
the body must tightly control calcium ion concentrations in order
to prevent damage to essential physiological systems.
Calcium ion homeostasis is maintained by a pair of hormones
with opposing effects. These hormones, parathyroid hormone
and calcitonin, coordinate the storage, absorption, and excretion
of calcium ions.
When calcium ion concentrations in the blood fall below normal:
Hormone released
Organ
Function
When calcium ion concentration in the blood rises above normal:
Hormone released
Organ
Function
Fractures
-cracks or breaks in bone
-caused by physical stress
Four Steps to Fracture Repair
Homeostatic Imbalances
Osteoporosis
Aging and the Skeletal System
The bones of the skeleton become thinner and weaker as a normal part of the aging process. The reduction of bone mass
begins between the ages of 30 and 40. Over that period, osteoblast activity begins to decline while osteoclasts activity
continues normally.
Women lose about 8% of their skeletal mass every decade and men 3%.