Chapter 12 Flashcards
Bones are
Rigid mineralized structure that help perform five major roles in the body
The 5 major roles bones help perform in the body
Support
Protection
Movement
Mineral storage
Hematopoiesis
Bones are often called ——
There are —— bones in the humans body
- bones are often called Osseous tissue
- 80 axial, 126 appendicular (206)
The five shape categories of bones
Long bones
Short bones
Flat bones
Irregular bones
Sesamoid bones
Diaphysis
Main shaft-like portion, hollow, cylindrical and thick with compact bone
Epiphyses
At distal and proximal ends of the bone that provide points of muscle attachments and stability to joints
Articulate cartilage
Thin layer of hyaline cartilage
Periosteum
Dense, white fibrous membrane that covers bone (except joint surfaces)
Medullary cavity
“Marrow cavity”
Endosteum
Thin, fibrous membrane that covers the medullary cavity
Compact bone
External table: compact bone around the external (distal) cortex
Internal table: compact bone around the internal (proximal) cortex
Diploe: the region between the external and internal tables, which is composed of cancellous bone
Bones differ in?
Both size and shape
They also differ in the amount and proportion of two main types of bone:
Cortical (cortex-> outside) - dense and solid bone, primarily around the edge (outer layer) of bone structures
Cancellous - “spongy born”/ “trabecular bone”
- a network of thin branched crossbeams, which provide structural support of bone structures, primarily found in the center
Compact bone constitutes about —— of the total bone mass in adult bones
- compact bone constituents about 80% of total bone mass in adults
- cylinder-shaped structural units “Haversian systems”
- Each osteon surround a Central Canal: delivers nutrient and removes wastes from the metabolically active, but imprisoned, bone cells
Structures of the osteon:
Lamellae:
Concentric lamellae: cylinder-shaped layers of calcified matrix in the osteon
Interstitial lamellae: layers of calcified matrix between osteons
Circumferential lamellae: lamellae that run along the inner circumference and outer circumference of a bone
Structures of the osteon
Lacunae: smalls spaces in bone matrix that contain tissue fluid and bone cells
Canaliculi: ultra-small canals that radiate in all directions from the lacunae and connect them to teach other and to the central canal
Central Canal: “Osteonal canal”/ “Haversian canal” - lined with endosteum and contains blood vessels,, lymphatic vessels and nerves
Bones are held together by and critical for what
Bones are held together by ligaments
Critical structures for support, movements and maintaining homeostasis
Bone to bone
Bone to muscle
Bone to bone = ligaments (Sprains)
Bone to muscle - tendons (strains)
The three bone cells
Osteoblast:
- “Bone-building” cells -> synthesize and secrete an organic matrix called osteoid
- collagen strands in the osteoid serve as a framework for the formation of hydroxyapatite crystals, which mineralizes the bone tissue
Osteoclast:
- “Bone-destroying” / “Bone-reabsorbing” cells
- Giant multinucleate cells which are responsible for the active erosion of bone minerals (hydrochloric acid (HCL) and collagenase)
Osteocyte:
- “mature cells”
- mature no dividing osteoblasts that have become surrounded by matrix and now lie within Lacunae
Cancellous bone consists of?
Cancellous bone consists of about 20% of total bone mass
- They contain no osteons but instead consist of crisscrossing bony branches called trabeculae (“trabecular bone”)
Fractal -> cancellous bone
They appear random, but they are more complex in orientation
Trabeculae are actually arranged along liens of ——
Arranged along lines of stress
- their size and orientation will there differs between individual bones according to the nature and magnitude of the applied load
- the direction of stresses created by the weight of the body
Wolff’s law
- developed from the German Anatomist and surgeon Julius Wolff
- “bone in a healthy person or animal will adapt to the loads under which it is placed”