The Skeletal System Classification of Bones Objectives Know

The Skeletal System Classification of Bones Objectives: -Know the basic types of bones -Identify examples of bones Agenda: 1) Quick Read 2) Classification presentation 3) Hands on bone identification Reminders: HW & Vocab/ Stems due TODAY A person who never made a mistake never tried anything new. – Albert Einstein

Classification of Bones 206 bones in body organized into two groups: • Axial skeleton • • forms the long axis of body includes bones of skull, vertebral column and ribcage • Appendicular skeleton • consists of bones of upper and lower limbs & girdles (shoulder & hip bones)

Classified by their shape: 1. Long • bones of limbs except patella & wrist • based on elongated shape NOT size

2. Short roughly cube shaped in wrist and ankle

3. Sesamoid • shaped like a sesame seed • special type of bone that form within a tendon kneecap (patella)

4. Flat thin, flattened & usually a bit curved sternum (breastbone) scapulae (shoulder blade) ribs skull

5. Irregular • complicated shapes that don’t fit into the other categories • hip bone vertebrae

What are bone Markings? -Projections on bones: -sites of muscle/ligament attachment -formation of joints -depressions & openings allowing blood vessels & nerves

Functions of Bones • Support – a framework for the body • Protection • bones protect many internal organs • cranial bones surround the brain; vertebrae surround the spinal cord; pelvic girdle surrounds the reproductive organs • Movement - muscles attach to bones • Mineral homeostasis - Ca++, PO-4 storage • Site of blood cell production - hematopoiesis in red bone marrow

Types of Bone • Compact • Appears very dense • Most of the bone mass in the body • Spongy • Small struts of bone (trabeculae) • May appear randomly organized, but the trabeculae are generally oriented in the directions of stresses

Macroscopic Bone Structure • Diaphysis • the shaft of a long bone • contains medullary or marrow cavity • infants have red (hematopoietic) bone marrow • red marrow gradually replaced by yellow (fatty) bone marrow throughout life

Epiphysis (epiphyses) -ends of a long bone Epiphyseal plate – growth plate made of cartilage Nutrient foramen - site of blood vessel entry into bone Articular cartilage - hyaline cartilage covering epiphysis

Periosteum • 2 layers of connective tissue around bone • Fibrous layer (outer) - dense irregular connective tissue • Osteogenic layer (inner) • osteoblasts – bone-forming cells • osteoclasts – boneremodeling cells • Site of ligament, tendon attachment • Large supply of nerves & blood vessels

Endosteum • Lines the medullary cavity • Contains osteoblasts and osteoclasts

Assignment: Anatomy of a Long Bone worksheet DUE WEDNESDAY