Chapter 6.2 HSCI

epiphysis

ends of the long bone

diaphysis

the shaft of the bone

metaphysis

region between diaphysis and epiphysis

epiphyseal plate

a piece of hyaline cartilage in long bones where growth occurs

epiphyseal line

bony plate remains that indicate that growth has stopped

periosteum

Covers external surface of bone except joint surfaces

Compact Bone

the dense, hard outer layer of all bones that provides strength, support, and protection

• resist unidirectional stresses

spongy bone

• inside layer of bones that have a honeycomb framework that is lighter and less dense

• lined by endosteum

Red Bone Marrow

• hemotopoetic aka responsible for reproducing blood cells

• located in children: spongy bone, medullary cavity

• located in adults: axial skeleton

yellow bone marrow

• Production of bone marrow degeneration

• stores fat

• composition

  • Triglyceride

    Adipocytes

    Blood vessels

    Can convert back to red bone marrow

Osteoprogenitor cells

• Mitotically activate stem cells

• Located in

  • Periosteum

  • Endosteum

• evolve into: osteoblast

Osteoblasts

• Active cells

• Located in

  • Periosteum

  • Endosteum

• Perform bone deposition

  • Secrete organic bone matrix

  • Osteoid

• Becomes osteocytes

osteocytes

• Not active

• Housed in lacunae

• Maintained bone matrix

• Communicate with osteoblast and osteoclast

  • Determines the needs of bone

bone deposition

creating new bones

osteoclast

• Responsible for bone resorption  

  • Breakdown of bone

  • Secretion of:

    • H+ → inorganic matrix

    • Enzymes → organic matrix 

• large multinucleated cells: have ruffled border

• Looks like Mr. scrub

Inorganic matrix

• Hydroxyapatite crystal

  • Protection

  • Resist compression

• Bicarbonate

• Potassium

• Magnesium

hydroxyapatite crystal

contains: calcium and phosphorus

function: protection, resist compression

organic matrix/osteoid

• Components

  • Collagen fibers

  • Ground substance

• Function

  • strength 

  • Flexibility

  • Both helps resist stretching and twisting

bone remodeling

• Lifelong process of maintaining bone matrix

• Functions to:

  • Meet the changing mechanical needs

    • Ex. when you stop running, you don't need as much bone matrix

  • Repair microdamage

  • Maintain calcium homeostasis

Canaliculi

• spikes poking out from central canals; Senses the extracellular matrix to figure out if we need to build bones

canals

where blood vessels come through

volkmann

canal that connects central canals together

osteons

looks like logs in compact bones

concentric

rings of the log making up the osteons

interstitial

space between osteons

circumferential

Layers of bone matrix that form concentric rings around the Haversian canals in compact bone.

ossification

the natural process of bone formation, where soft tissues like cartilage or connective tissue are gradually hardened into bone

Intramembranous ossification

a process of bone formation where bone develops directly from mesenchymal connective tissue

• forms:

• Clavicle

  Frontal bones

  Premarital bones

  Occipital bones

  Temporal bones

endochondral ossification

forms bone by first creating a hyaline cartilage model which is then replaced by bone

forms: All ones inferior to head (except clavicle)

Longitudinal growth

• Growth in length

• Takes place in epiphyseal plate

• Involves division of chondrocytes (cartilage cells)

• Only in long bones

appositional growth

• the process of increasing the size of a bone or cartilage by adding new tissue to its outer surface

• Growth in width

• Involves osteoblast and osteoclasts

• Can occur in ALL bones

Zone of proliferation

a layer of the growth plate in long bones where chondrocytes cell division occur

proliferation

to make cells

Zone of hypertrophy and maturation

a region where chondrocytes enlarge, mature, and stop cell division

hypertrophy

the increase in the size of an organ or tissue due to the enlargement of its existing cells,

Zone of calcification

1. The matrix calcifies (hardens)

2. Results in cartilage cells dying

Zone of ossification

Calcified cartilage is replaced with bone

Bone remodeling

the continuous process of breaking down old bone and forming new bone tissue