Skeletal System

Support

Holds your body upright and gives it shape.

Protection

Shields vital organs like the brain and heart.

Movement

Bones work with muscles to help you move.

Blood Cell Formation

Red bone marrow makes blood cells.

Mineral Storage

Stores and releases minerals like calcium and phosphate.

Fat Storage

Yellow marrow stores fat for energy.

pH Balance

Helps keep your blood’s acidity balanced by managing minerals.

Long bones

Long and skinny, help you move and stand up.

Short bones

Small and blocky, help with balance and stability.

Flat bones

Thin and flat, protect your organs like a shield.

Irregular bones

Weird shapes that don’t fit other groups, protect and support parts of your body.

Collagen

A soft, stretchy protein in bones that allows them to bend.

Hydroxyapatite

A hard mineral in bones that makes them tough and strong.

Osteogenic cells

Stem cells that can become osteoblasts.

Osteoblasts

Cells that build new bone by making collagen and adding minerals.

Osteocytes

Mature bone cells that maintain bone tissue.

Osteoclasts

Cells that break down bone and release calcium.

Periosteum

The outer covering of bones, containing an inner layer of osteogenic cells.

Endosteum

The thin lining inside bones that contains osteogenic cells.

Osseous Tissue

Hard tissue that makes up bones, providing support and protection.

Hyaline Cartilage

Smooth and flexible cartilage present at joints to reduce friction.

Trabeculae

Thin branches in spongy bone that support lightweight structure.

Osteons

Circular units in compact bone that provide strength and protection.

Calcium ions (Ca²⁺)

Help muscles contract, carry nerve signals, help form blood clots, and keep bones strong.

Phosphate ions (PO₄³⁻)

Build DNA and ATP, balance acid-base levels, and contribute to bone hardness.

Bicarbonate ions (HCO₃⁻)

Maintain blood pH balance, neutralize acids, and help carry carbon dioxide in blood.

Calcitriol

Active vitamin D that raises blood calcium levels.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium levels by activating bone breakdown.

Calcitonin

Hormone produced by the thyroid gland that lowers blood calcium levels.

Red Bone Marrow

Produces red and white blood cells.

Yellow Bone Marrow

Stores fat and can convert back to red marrow if needed.

Osteoporosis

Condition where bones become weak and brittle, often due to age or nutrient deficiency.

Rickets

A disease in children characterized by soft and weak bones due to vitamin D deficiency.

Intramembranous Bone Formation

Process where bone develops from mesenchymal cells to form spongy bone.

Endochondral Bone Formation

Process where bone replaces a cartilage model as the body grows.

Canaliculi

Tiny tubes in compact bone that connect bone cells for nutrient exchange.