Chapter 6 Study Guide: Bone Tissue

diaphysis

The long middle part of the bone (like the shaft of a baseball bat).

epiphyses

The rounded ends of the bone (like the knob at the end of a drumstick).

metaphyses

The zones between the middle and ends where growth happens (like the stretchy part of a rubber toy).

periosteum

The outer layer covering the bone, like skin on a sausage.

medullary cavity (marrow cavity)

The hollow center of the bone filled with marrow (like jelly in a donut).

endosteum

The inner lining of the medullary cavity (like the inner wrapper lining a chocolate bar).

osteogenic cells

Stem cells that develop into osteoblasts. The “baby” cells that can become builders.

osteoblasts

produce the molecules of the bone matrix. The builders – they build new bone.

osteocytes

mature bone cells that maintain the bone matrix (and bone tissue). The managers they maintain and check on the bone.

osteoclasts

Cells that destroy the bone matrix (dissolving bone tissue). The demolition crew – they break down bone to release calcium.

compact bone

Hard and solid like concrete (outer layer of bone).

spongy bone

Lightweight and airy like a sponge or honeycomb (inside of bone).

osteons or Haversian systems

Circular building blocks of compact bone (like tree rings).

perforating (Volkmann's) canals

Side roads bringing blood from the outside into the bone.

central (Haversian) canals

Main roads running through each osteon for blood vessels.

lamellae

Layers or rings in the osteon (like onion layers). Thin (concentric) layers of bone matrix that form the structure of osteons.

lacunae

Small “rooms” where bone cells (osteocytes) live. Tiny holes or spaces in the bone layers where osteocytes live

canaliculi

Tiny tunnels that connect bone cells so they can talk (like text messages). Microscopic canals that connect lacunae and allow for communication between osteocytes.

trabeculae

The lattice-like beams in spongy bone (like scaffolding in a building. The small, rod-like structures in spongy bone provide support.

ossification or osteogenesis

The process by which bone forms. The process of bone formation (like pouring concrete to make a sidewalk).

intramembranous ossification

The process by which bone develops directly from mesenchymal tissue. Bone forms directly from soft tissue (like a flat bone of the skull forming from a soft sheet).

endochondral ossification

The process by which bone forms by replacing hyaline cartilage. Bone replaces cartilage (like turning rubber into stone — most bones do this).

interstitial growth

Growth in length occurs at the growth plate epiphyseal plates. Bones grow longer at the growth plate (like stretching a rubber band).

appositional growth

Bones grow thicker by adding layers (like wrapping more tape around a pipe).

primary ossification center

The first spot where bone starts to form (in the middle of the bone).

secondary ossification center

They show up later at the ends of the bone (epiphyses) after the primary center does its thing.

epiphyseal plate

The growth plate is where bone lengthens (like a stretchy band). Where, the cartilage between the diaphysis and epiphysis lets your bone grow longer

epiphyseal line

What’s left after growth stops (a scar that shows you’re done growing). It means you've stopped growing

bone remodeling

Constantly replacing old bone with new (like renovating your house a little at a time).

bone resorption

Breaking down bone to release calcium (like taking apart a Lego set).

Disuse (like muscles shrinking if you don’t use them)

No use = bone loss

Stress (like lifting weights makes bones denser).

More stress = stronger bones

Cardiac arrest (heart can’t beat right).

Too much blood calcium

Respiratory arrest (muscles can’t contract properly).

Too little blood calcium

Blood calcium levels regulated by control of rate of resorption from bone 

Pulling calcium out

Blood calcium levels regulated by control of rate of deposition into bone

Putting calcium in

Turns on the calcium-releasing team.

Increased PTH (parathyroid hormone) production

Decreasing blood calcium levels results. More bone breakdown = more calcium released

Increase the number and activity of osteoclasts

Decreasing blood calcium levels. Kidneys save calcium instead of peeing it out.

Decrease urine calcium loss

Helps absorb more calcium from food in the intestines. Promotes calcium absorption from GI tract

Calcitriol

Rising blood calcium levels. Hormone that stores calcium back in bone

Increased Calcitonin Production

Calcitonin accelerates. Bone “soaks up” extra calcium like a sponge.

Calcium deposition