exam 2 AP

What structures make up the skeletal system?

Bones, cartilage, ligaments, and other connective tissues.

What are the primary functions of the skeletal system?

Support, gives the body shape, and storage of minerals and lipids.

What are additional functions of the skeletal system?

Protection of organs, movement with muscles, and blood cell production (hematopoiesis).

What are the five classifications of bones?

Long bones, short bones, flat bones, irregular bones, and sesamoid bones.

Characteristics of long bones

Longer than they are wide; have a diaphysis and epiphyses; mostly compact bone with spongy bone at the ends; examples include femur, humerus, tibia, and fibula.

Characteristics of short bones

Roughly cube-shaped; mostly spongy bone surrounded by compact bone; examples are carpals and tarsals.

Characteristics of flat bones

Thin and often curved; two layers of compact bone with spongy bone between; provide protection and muscle attachment; examples are skull, ribs, and sternum.

Characteristics of irregular bones

Complex shapes that do not fit other categories; examples include vertebrae and pelvic bones.

Characteristics of sesamoid bones

Small bones embedded in tendons; reduce friction and modify pressure; example is the patella.

What is the diaphysis?

The shaft of a long bone made mainly of compact bone surrounding the medullary cavity.

What are the epiphyses?

The enlarged ends of long bones that contain mostly spongy bone.

What is the metaphysis?

The region between the diaphysis and epiphysis that contains the epiphyseal plate.

What is the medullary cavity?

The hollow cavity inside the diaphysis that contains bone marrow.

What is the periosteum?

The outer connective tissue covering of bone containing blood vessels, nerves, and osteogenic cells.

What is the endosteum?

A membrane lining the medullary cavity and internal surfaces of bone.

What are the two types of bone tissue?

Compact bone and spongy bone.

What is compact bone?

Dense, strong bone organized into osteons that provides strength and protection.

What is spongy bone?

Porous bone made of trabeculae that contains red bone marrow.

What are the two components of bone matrix?

Organic matrix (osteoid) and inorganic mineral salts.

What makes up the organic matrix?

Collagen fibers and ground substance; provides flexibility and tensile strength.

What makes up the inorganic matrix?

Calcium phosphate crystals (hydroxyapatite); provides hardness and resistance to compression.

What are osteogenic cells?

Stem cells that divide and develop into osteoblasts.

What are osteoblasts?

Bone-building cells that secrete osteoid and promote mineralization.

What are osteocytes?

Mature bone cells that maintain the bone matrix and monitor mechanical stress.

What are osteoclasts?

Large cells that break down bone during bone resorption.

What is bone remodeling?

The continual replacement of old bone with new bone.

Which cells are responsible for bone remodeling?

Osteoclasts remove old bone while osteoblasts build new bone.

How does stress affect bone?

Appropriate stress increases bone strength.

What is ossification (osteogenesis)?

The process of bone formation.

What are the two types of ossification?

Intramembranous ossification and endochondral ossification.

What bones are formed by intramembranous ossification?

Mostly flat bones.

Where does intramembranous ossification occur?

Within fibrous membranes.

What does endochondral ossification begin with?

A hyaline cartilage model.

Stage 1 of endochondral ossification

Bone collar forms around the diaphysis from the perichondrium.

Stage 2 of endochondral ossification

Primary ossification center develops in the diaphysis; diffusion is blocked, chondrocytes die, and osteoblasts form bone.

Stage 3 of endochondral ossification

Periosteal bud invades the cavity and spongy bone forms.

Stage 4 of endochondral ossification

Diaphysis elongates and a medullary cavity forms.

Stage 5 of endochondral ossification

Secondary ossification centers form in the epiphyses, leaving the epiphyseal plate between the diaphysis and epiphyses.

Where does longitudinal bone growth occur?

At the epiphyseal plate.

How do bones grow in length?

Chondrocytes add cartilage while osteoblasts replace the cartilage with bone.

What happens when the epiphyseal plate closes?

It becomes the epiphyseal line and lengthwise growth stops.

What is appositional growth?

Growth that increases the diameter of a bone.

How does appositional growth occur?

Osteoblasts beneath the periosteum deposit new bone while osteoclasts remove internal bone, enlarging the medullary cavity.

How much of the body's calcium is stored in bones?

About 99% of the body's calcium.

What hormones regulate blood calcium levels?

Parathyroid hormone (PTH) and calcitonin.

What does parathyroid hormone (PTH) do?

Increases blood calcium levels by stimulating bone resorption.

What does calcitonin do?

Lowers blood calcium levels by promoting calcium deposition in bone.

What are the four stages of fracture repair?

Hematoma formation, fibrocartilaginous (soft) callus formation, bony (hard) callus formation, and bone remodeling.

What occurs during hematoma formation?

Bleeding occurs and a blood clot forms to stop blood loss.

What occurs during fibrocartilaginous callus formation?

New blood vessels grow, the hematoma is removed, and cartilage forms a temporary bridge.

What occurs during bony callus formation?

The cartilage is replaced with spongy bone.

What occurs during fracture remodeling?

The bone is reshaped and excess material is removed until it returns close to its original structure.

How does bone aging affect bone tissue?

Osteoblast activity decreases or stops while osteoclasts continue bone resorption, leading to bone loss and increased fracture risk.