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