Chapter 5: The Skeletal System

Differentiate between axial and appendicular skeletons.

Differentiate between axial and appendicular skeletons.

The axial skeleton is composed of a longitudinal axis while the appendicular skeleton is composed of limbs and girdles.

List and describe the 5 functions of bones.

Bones function to support the framework of the body, protect the internal organs and brain, move by the attachment of skeletal muscles, store minerals such as calcium and phosphorus, and form blood cells through hematopoiesis.

Differentiate between compact and spongy bones.

Compact bones are dense and smooth. Spongy bones have open spaces and a honeycomb appearance.

List the 4 types of bones categorized by their shape.

The 4 types of bones categorized by their shape are long bones, short bones, flat bones, and irregular bones.

Describe each type of bone based on their shape.

Long bones - longer than they are wide, are mostly compact bones

Short bones - sesamoid (embedded within a tendon), cube-shaped, and mostly spongy bones

Flat bones - thin, flat, curved, and the “sandwich” of compact and spongy bone

Irregular bones - do not fit into any other category

Give an example of each type of bone.

Long bones - all limbs except for wrists and ankles

Short bones - patella, wrists, ankles

Flat bones - skull, ribs, sternum

Irregular bones - vertebrae, hips

Diaphysis

the shaft of a long bone, composed of compact bone

Periosteum

the membrane that covers and protects the diaphysis

Sharpey’s (perforating) fibers

anchor the periosteum to the bone

Epiphyses

the ends of long bones, composed of spongy bone

Articulate cartilage

covers the ends of epiphyses, decreases friction

Epiphyseal line

a remnant of epiphyseal plate

Epiphyseal plate

composed of hyaline cartilage, lengthwise growth, and is replaced by bone

Medullary cavity

the hollow part containing red marrow and yellow marrow

Red marrow

site for blood cell formation

Yellow marrow

adipose tissue

What is ossification?

the process of bone formation

What are osteoblasts?

bone-forming cells

What are osteoclasts?

bone-destroying cells

List 2 reasons bones are continually remodeled.

Bones are continually remodeled in response to calcium levels in the blood and the pull of gravity and muscles on the skeleton.

Briefly describe what happens when calcium levels are too high and too low.

When calcium levels are too high, calcium is deposited into the bone matrix for later use. When calcium levels are too low, the hormone PTH (parathyroid) activates osteoclasts to break down bone and release calcium.

What is the importance of bone remodeling?

Bone remodeling is necessary to retain normal proportions and strength.