intro to skeletal Flashcards
Endosteum
- a layer of bone cells that cause the bone to grow, repair, and remodel throughout life.
*Lining the inside of the bone adjacent to the medullary cavity
Periosteum
Part of the outer double layered structure on the outside of bones that grow, repair and remodel bone as well.
Osteoblasts
*responsible for building new bone tissue
* FORM OSTEOCYTES
* cells that synthesize bone matrix and coordinate the mineralization of the skeleton.
Osteocytes
FORM NEW BONES
The longest living bone cell, making up 90–95% of cells in bone tissue
Osteoclasts
BREAKDOWN BONE
The cells that degrade bone to initiate normal bone remodeling and mediate bone loss in pathologic conditions by increasing their resorptive activity.
Diaphysis
is the hollow, tubular shaft that runs between the proximal and distal ends of the bone.
Epiphysis
The area of the long bone where bone growth takes place.
Long bones have
a long longitudinal axis
Short bones have
a short longitudinal axis and are more cube-like
Flat bones are
thin and curved such as some of the bones of the skull
Irregular bones are
often found in groups and have a variety of shapes and sizes
Sesamoid bones are found in
ligaments
There are also 2 types of bone tissue in different amounts in bones.
Compact bone (sometimes called cortical bone) is very dense. Cancellous bone (sometimes called spongy bone) looks more like a trabeculated matrix.
The bone forming cells (called osteoblasts) get their nutrients by
diffusion
Compact bone is organized according to structural units called
Haversian systems or osteons. These are located along the lines of force and line up along the long axis of the bone. The Haversian systems are connected together and form an interconnected structure that provides support and strength to bones.
Osteons contain a central canal (Haversian canal) that serves as
a pathway for blood vessels and nerves.
Bone is deposited along concentric rings called
lamellae
Along the lamellae are small openings called
lacunae
The lacunae contain fluid and bone cells called
osteocytes
Radiating out in all directions from lacunae are small canals called
canaliculi
Osteons are interconnected by a series of larger canals called
Volksmann’s canals (perforating canals).
Osteoblasts undergo
mitosis and secrete a substance that acts as the framework for bone. Once this substance (called osteoid) is secreted, minerals can deposit and form hardened bone. Osteoblasts respond to certain bone forming hormones as well as from physical stress.
Osteocytes
are mature osteoblasts that cannot divide by mitosis.
Osteocytes reside in
lacunae
Osteoclasts are capable of
demineralizing bone. They free up calcium from bone and release it into the blood depending on the body’s needs.
There are 2 bone forming processes.
Flat bones called intramembraneous bones develop in sheet like layers.
Tubular bones called endochondral bones develop from cartilage templates.
During intramembranous ossification, bones form from
sheet-like layers of connective tissue.
These layers have a vascular supply and contain bone forming cells called
osteoblasts
The osteoblasts secrete
bony matrix in all directions around the cell. The matrix unites with that secreted by other osteoblasts as the bone forms.
Eventually the osteoblasts may be walled off by the bony matrix. At this point the osteoblast is called
an osteocyte
Tubular bones develop from a process known as
endochondral ossification. During this process, bones develop from hyaline cartilage templates.
Some important steps of Endochondral ossification include:
Formation of the outer covering called the periosteum.
Development of the primary and secondary ossification centers.
Development of the medullary cavity
Formation of the epiphyseal plates and spongy bone.
The middle tubular portion is called ___ and then ends are called___
diaphysis
epiphyses
Between the diaphysis and epiphysis is the
metaphysis
The outer covering of long bone is called
the periosteum
the hollow inner cavity of long bone is called
the medullary cavity the contains the bone marrow
The epiphysis contains
the epiphyseal plate or growth plate
what type of bone is in the epiphysis
spongy trabeculated bone
what type of bone is in the diaphysis
compact bone
