Bones Flashcards
smallest bone in the human body
The stapes or stirrup bone
humans have ? bones
206 in adults and 300-350 in infants
Functions of bones
• Support • Protection • Movement • Mineral storage • Blood cell formation • Energy storage . Attachment sites for muscle
Compact bone tissue - in outer regions of the bone. Why?
• Bending exerts strongest forces in these areas.
• Spongy bone tissue -
in inner regions,
mainly near epiphyses
- Spongy bone “pillars” (trabeculae) are aligned along stress lines
- Red bone marrow (even in adults) – in marrow cavities
- Osteoblasts:
bone-building cells
Osteoclasts
bone-dissolving cells. Larger than other bone cells.
Osteocytes
mature osteoblasts, trapped in matrix
Compact bone tissue. In outer regions. Why?
Strongest force there.
Red bone marrow tissue
Lymphoid tissue, all lymphoid tissue is reticular tissue.
In the spongy bone cavities.
What structure is flat bones of the skull.
Spongy bone sandwiched between compact bone. Think about how heavy a compact bone head would be. Also spongy bone helps impact.
Perichondrium
- Which acts like a girdle to to resist outward pressure of the cartilage
- growth and repair of cartilage
- 60-80% water very resilient
Hyaline cartilage
Most abundant
• Periosteum:
- Dense irregular CT
- Covers most of bone - Functions:
– Resists tension
– Growth
– Attachments
(Periosteum secured by perforating fibers)
• Articular cartilage
a thin layer hyaline cartilage covering the joint surface of each epiphysis.
• Medullary cavity in
diaphysis. Contains:
- Red bone marrow (at birth)
- Contains hematopoietic stem cells (immature blood cells)
- A lymphoid structure (reticular connective tissue)
- Yellow bone marrow (in adults)
- Adipose tissue
• Endosteum
for remodeling interior surfaces of bone
Exists as the interior layer lining the inside of the medullary cavity.
And canals in compact bone.
hydroxyapatite
primarily calcium phosphate
- Resists compression
What are the 2 types of mature bone tissue?
compact and spongy
- Osteoid
- the matrix( ground substance and fibers) secreted by the osteoblasts.
- This also includes enzymes promoting calcium phosphate formation
Concentric lamellae
form an osteon
Interstitial lamellae
remnants of old osteon
Woven bone
immature bone
• Bone tissue that has recently formed
- Produced rapidly (e.g. fetus or healing fracture)
- Eventually remodeled into spongy or compact bone
• Has trabeculae
• Collagen fibers randomly arranged (“woven”), so…
- No lamellae
- Weaker than spongy or compact bone
= mature bone
Intramembranous bone formation steps
- Mesenchyme gives rise to osteoblasts
And secrete the organic part of the bone matrix( Osteoid) - Surrounded by the matrix blasts become cytes. And woven bone is the result
- The woven bone tissue are trabeculae but no lamellae. During this stage the mesenchyme condenses to form the periosteum.
- Trabeculae at apical surface grow thicker and become compact bone. Inner trabeculae remain and form spongy bone.
This is flat bone of the skull and clavicle. No other intramembraneous bones exist.
Endochondral bone formation steps
- Cartilage model grows a periosteum
• Periosteum produces bone collar - Chondrocytes in center of diaphysis cause cartilage matrix to calcify
• Calcified matrix blocks nutrient diffusion • Chondrocytes die -> cavity is produced - Periosteal bud (vessels, bone cells) invades diaphysis • Spongy bone deposited over calcified cartilage
• Resulting bony region is called the primary ossification center
 - Steps 2 & 3 occur in the epiphyses as well: - Cartilage matrix calcifies
- Chondrocytes die
- Bud invades
- Bone tissue deposited
• Results in secondary ossification centers
• Does not happen until
around birth
5. Further ossification and remodeling • Mature arrangement of compact & spongy bone • Cartilage remains in two places: - Articular cartilage - Epiphyseal plate 
Diaphysis
Shaft of the long bone.
Epiphysis
The bone ends
Epiphyseal line
Between the diaphysis and each epiphyses of the adult longbone. Consists of compact bone.
-remnant of the epiphyseal plate, a disk of hyaline cartilage that grows during childhood to lengthen the bone.
Intramembranous ossification
Process of bone development of ‘membrane bones’ develop from mesenchymal membranes.
Endocondral ossification
Bones develop as hyaline cartilage, know as cartilage replacement bones.
Epiphyseal plates
Elongation/ bone lengthening occurs here.
Tribecular bones.
Spongy bone
Has lamellae but not osteons.
Compact bone interior.
- central Haversian canal
- perforating Volkmans canals connect them
- these canals lined by endosteum
- arteries veins nerves run through these canals
