CT 2 B Flashcards
If one makes a longitudinal section through a bone, there are two distinct areas:
- The outer, or cortical region, is solid and is composed of compact bone.
- The inner portion contains spongy bone which has thin anastomosing spicules called trabeculae
At a gross level, there are two general types of bone:
- the flat bones (e.g. the skull, mandible)
2. the long bones (e.g. tibia, femur, humerus).
A long bone consists of a
- central shaft
- the diaphysis
- two expanded ends, each called an epiphysis.
The outer, or cortical region, is:
solid and is composed of compact bone.
The inner portion contains:
spongy bone which has thin anastomosing spicules called trabeculae (spongy bone is also called cancellous or trabecular bone).
Compact and trabecular bone contain:
the same types of cells and the same matrix but different relative activities of bone cells lead to different structural arrangements.
compact bone provides:
most of the strength of the bone for support
trabeculae provides:
extensive surface area for metabolism.
Within the spaces between the trabeculae of the inner spongy bone is:
soft tissue called bone marrow.
Bone marrow consists of:
either hematopoietic tissue (red bone marrow) or adipose cells (white bone marrow) surrounded by loose connective tissue containing numerous blood vessels.
The outer surface covering the bone called the ____
periosteum, which contains dense connective tissue containing fibroblasts, bone precursors and bone cells.
The inner surface where trabeculae contact internal soft tissue is called the _____
endosteum, which is where most calcium mobilization and storage occurs.
there are tunnel-like channels through bone that also contain _____
small amounts of soft connective tissue, blood vessels, and nerves.
Bone cells:
- osteoprogenitor
- osteoblasts
- osteocytes
- osteoclasts
Osteoprogenitor cells are ____
stem cells that are capable of cell division to generate the osteoblasts and osteocytes that comprise most of the cells of bone.
Osteoprogenitors are present in both _____
the periosteal and endosteal surfaces, and in the soft connective tissue of the channels.
Osteoblasts line _____
the inner layers of both periosteal and endosteal surfaces where bone growth or remodeling is occurring.
Osteoblasts actively secrete _____.
the initial un-mineralized extracellular matrix of bone, which is called osteoid
Osteoblasts also pinch off _____.
membrane-enclosed vesicles, the matrix vesicles, which contain enzymes that initiate bone calcification (mineralization)
Osteoblasts are connected to each other and to nearby osteocytes by ____
gap junctions.
Osteoblasts are also capable of _____
cell division
Osteocytes are directly derived from ____.
osteoblasts
Osteocytes arrest in___.
Go
canaliculi
osteocytes extend long processes through tiny channels in the calcified matrix
form gap junctions with processes from other osteocytes
the cells of bone form a_____.
living interconnected lattice of cells, which can communicate directly, and are surrounded by abundant calcified matrix
Osteocytes retain a limited ability to ______.
modify bone matrix, but they do not secrete much matrix material
the ____ are the secretory engines that make bone matrix.
osteoblasts
The role of osteocyte activity in bone maintenance is to ___
signals to each other and to osteoblasts at the surface through their gap junctions
Osteoclasts are derived from ____
monocytes in the blood, which themselves originate from hematopoietic stem cells in the bone marrow.
Osteoclasts resemble and are related to _____.
macrophages
Like macrophages, osteoclasts are phagocytic cells.
osteoclasts specifically _____
degrade bone or cartilage matrix.
Osteoclast roles in bone dynamics:
- degrade cartilage or bone matrix to allow inward growth of blood vessels during bone formation.
- resorb already made bone to promote remodeling of the bone matrix.
- resorb bone for the purpose of mobilizing Ca2+ into the bloodstream
(critical for maintaining proper Ca2+ concentrations in blood)
