microscopic structure of bone. osseous tissue another name for bone tissue bone is a connective...
TRANSCRIPT
Microscopic Structure of Bone
Osseous Tissue
Another name for bone tissue Bone is a connective Tissue
Widely spread cells Matrix:
Water, Collagen Fibers, Mineral Salts
Calcification
Hardening of bone tissue by the deposition of mineral salts in the collagen fiber of the matrix
Hardness and Flexibility
Hardness – Provided by the crystallized mineral salts
Flexibility – Provided by the collagen fibers Bones can resist being stretched or
torn apart
Cells
There are 4 major types of cells found in osseous tissue Osteoblast Osteocyte Osteoprogenitor Osteoclast
Osteoblast
Bone building cells Synthesize and secrete collagen
fibers and other organic components needed to build the matrix of the tissue
Osteoblasts surround themselves with matrix, become trapped in their secretions and become osteocytesosteocytes
Do not undergo Mitosis
Osteocyte
Mature Bone Cell Main cells in bone tissue
Maintains daily metabolism Do not undergo mitosis
Osteoprogenitor
“Bone stem cells” These cells undergo mitosis then
differentiate to form osteoblasts
Osteoclasts
HUGE cells formed from the fusion of as many as 50 monocytes
Concentrated in the endosteum Release lysosomal enzymes and
acids to digest the matrix
Reabsorption
Breakdown of bone matrix Part of the normal development,
growth, repair and maintenance
Categories of Bone Tissue
Bone has many small spaces between the cells and matrix – it is not completely solid.
The category of tissue is based on the size and distribution of these spaces
About 80% of bone is compact bone; 20% is spongy bone
Compact Bone Tissue
Contains very few spaces Forms the external layer of all
bones and the diaphyses of long bones
Provides protection and support Resists stress produced by weight
and movement
Osteon
Organizational Unit of Compact Bone
Perforating Canals
Transverse openings through which vessels from the periosteum penetrate the compact bone and eventually meet up with other vessels
Central (Haversian) Canal
Run longitudinally through bone It is the center of the osteon Contains blood vessels and nerves
Concentric Lamellae
Rings of hard calcified matrix surrounding the central canal
Lacunae
Means “little lake” Small spaces between the lamellae Contain osteocytes
Canaliculi
Minute canals that radiate off the lacunae in all directions.
Contain projections of the osteocytes Connect lacunae creating a network
throughout the compact bone to provide nutrients and oxygen to all the osteocytes and to get rid of waste
Spongy Bone
Does not contain ostons Made of trabeculae – an irregular
network of thin columns of bone with many spaces in between
Trabeculae contain osteocytes within lacunae connected by canaliculi
Spongy tissue makes up most of flat, short and irregular bones
Forms most of the epiphyses of long bones
Found in a narrow rim around the medullary cavity
Spongy tissue is light – reducing the weight of the skeletal system
Red bone marrow is found in the spaces between trabeculae Hemopoiesis only occurs in the hip
bones, ribs, sternum, vertebrae and epiphyses of long bones – where red bone marrow is found
Bone Scan
Radioactive Tracer is injected through an IV and absorbed by the bone
A scanning device measures the amount of radiation emitted by the bones and translates the information into an x-ray
Normal bones have a consistent gray color
Darker/lighter areas indicate an abnormality Ex - Bone cancer, abnormal healing,
infections, arthritis
Checkpoint Questions – answer these in your notes…
1. What kinds of tissue make up the skeletal system?
2. How do red and yellow bone marrow differ in composition and function?
3. What are the types of bones?4. Draw and label the parts of a typical long
bone.5. What are the 4 types of bone cells?6. How are spongy and compact bone
different in microscopic appearance, function and location?