A&P Ch 6
spongy bone purpose
- lighter than compact bone - shock absorption - if present, always interior -tissue support
steps of endochondral ossification
1. Development of cartilage model 2. Growth of cartilage model 3. Development of primary ossification center 4. Development of medullary cavity 5. Development of secondary ossification center 6. Formation of articular cartilage & epiphyseal plate
Steps in bone thickening
1. Ridges in periosteum create groove for periosteal blood vessel. 2. Periosteal ridges fuse, forming an endosteum-lined tunnel. 3. Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon. 4. Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels.
steps of intramembranous ossification
1. development of ossification center 2. calcification 3. formation of trabeculae 4. development of periosteum
layers of epiphyseal plate
1. zone of resting cartilage 2. zone of proliferating cartilage 3. zone of hypertrophic cartilage 4. zone of calcified cartilage
Osteoporosis
A condition in which the body's bones become weak and break easily.
Paget's disease
A disease of unknown origin that is characterized by extensive breakdown of bone tissue followed by abnormal bone formation.
Bone deoposition
Addition of minerals and collagen fibers to bone by osteoblasts
What type of cartilage covers the epiphesis?
Articular Cartilage (hyaline cartilage)
perforating canals (Volkmann's canals)
Connect the haversian canals with each other and the periosteum. Small channels in bone that transmit blood vessels from the periosteum into the bone and that communicate with the Haversian canals. The perforating canals provide energy and nourishing elements for osteons.
Pott fracture-dislocation of ankle
Fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation
Canaliculi
Hairlike canals that connect lacunae to each other and the central canal
importance of calcium
Muscle contractions Nerve signaling Blood clotting Enzymatic reactions
Bone Reabsorption
Removal of minerals and collagen fibers from bone by osteoclasts
fracture repair
Step 1: Fracture hematoma forms Step 2: Fibrocartilage (soft) callus forms Step 3: Hard (bony) callus forms Step 4: Bone remodeled
Osteology
Study of bones
stress fracture
a small crack in the bone that often develops from chronic, excessive impact
greenstick fracture
bending and incomplete break of a bone; most often seen in children
Osteoblasts
bone forming cells
closed (simple) fracture
bone is broken but no external wound exists
Ossification
bone making
impacted fracture
broken bone ends are forced into each other
open (compound) fracture
broken bone penetrates through the skin
central canal (haversian canal)
canal that houses blood vessels located at the center of the osteon
What lines the medullary cavity?
endosteum
metaphyseal arteries
enter the metaphyses of a long bone and, together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyses
comminuted fracture
fracture in which the bone is splintered or crushed
Colles fracture
fracture of the distal radius at the wrist
Calcitonin
inhibits activity of osteoclasts, Lowers blood calcium levels
Two types of bone formation (Fetal)
intramembranous ossification and endochondral ossification
Where is the osteocyte located?
lacunae
Osteocytes
mature bone cells
Where is the epiphyseal plate located?
metaphysis
Complexity of skeletal cells
osteo-progenitor cells->osteoblasts->osteocytes | osteoclasts
What is calcium regulated by
parathyroid hormone (negative feedback loop)
What covers long bones?
periosteum
purpose of articular cartilage?
reduces friction and absorbs shock
osteoclasts function
resorption, breakdown of bone matrix
concentric lamellae
rings of bony matrix around a central canal
Lacunae
small cavities in bone that contain osteocytes
Osteon
structural unit of compact bone
epiphyseal artery
supplies blood to the ends of long bones
Compact bone purpose
support and protection
6 main functions of the skeletal system
support, protection, assistance in movement, mineral homeostasis, blood cell production, triglyceride storage
periosteal artery
this enters the diaphysis of a bone through a perforating (Volkmann's) canal and delivers blood to the periosteum and outer part of compact bone tissue
nutrient artery
this passes through a foramen in compact bone, and enters the medullary cavity, where it divides into proximal and distal branches that supply both the inner compact bone tissue of the diaphysis and the spongy bone tissue and red marrow of the epiphyseal plates
spongy bone made of
trabeculae