Intro to the Skeletal System

Anatomy lab exam 1

Functions of the skeletal system

• Physical support

• Site of attachment for muscles

• Protects vital organs

• Store red and yellow marrow

• Energy metabolism

• Mineral and element reservoir

What is the skeleton made up of?

Bones, cartilage joints, and ligaments. It is moved by skeletal muscle attached by tendons

How many bones are in the adult skeleton?

206

Subdivisions of the skeleton

Axial and appendicular

Axial skeleton

Cranium, ribs, vertebra, and midline structures

Appendicular skeleton

Associated with the limbs

Cartilage

• Flexible, resilient, mostly water

• Resists tension and compression

• Three types depending on fibers

Bone

• Strong and stiff

• Support skeletal system

• Protects organs

• Store and metabolize minerals

• Store red and yellow marrow

Cartilage structre

Made of chondrocytes (cartilage cells) in an extracellular matrix of collagen and fibers

Hyaline cartilage

Costal cartilages, articular joint cartilage, larynx, and trachea

Fibrocartilage

Pubic symphysis, menisci, and intervertebral discs

Elastic cartilage

Epiglottis and ears

Microstructure of bone

1. Osteocytes

2. Osteoblasts

3. Osteoclasts

Osteocytes

• 90-95% of bone cells

• Bone maintainers (trapped in osteoblasts)

• Sit in lacunae of osteons

Osteoblasts

Bone builders

Osteoclasts

Bone destroyers

Bone remodeling

• Bone is alive and continually undergoes remodeling

• Resorption of old and less essential bone is done by osteoclasts

• Deposition of new bone in critical areas is done by osteoblasts

• New bone replaces old bone with a complete cycle every 7-10 years

• Same process allows for healing after injury

Osteon (haversian system)

Structural unit of compact bone

Lamellae

Concentric rings/layers that make up osteons

Central (haversian) canal

Runs through the core of each osteon and provides blood supply

Lacunae

Small spaces between adjacent lamellae where osteocytes live

Cortical (compact) bone

• Smooth, dense outer layer

• Thickest in the diaphysis of long bones

Trabecular (spongy, cancellous) bone

• Network of beams of bone

• Deep to cortical bone

• Spaces filled in by marrow

Parts of a long bone

• Epiphysis

• Epiphyseal plate (growth plate) > Epiphyseal line

• Diaphysis

• Articular cartilage

• Periosteum

• Endosteum

• Marrow (medullary) cavity

• Articular cartilage

Ossification

Biological process of bone formation or growth

Intramembranous ossification

• Most cranial bones and medial parts of the clavicles

• Develops in a membrane

Endochondral ossification

• Most postcranial bones

• Develops from cartilage

Primary center of ossification

Diaphysis

Secondary centers of ossification

Epiphyses

Growth termination of bones

When the centers of ossification in the diaphysis and epiphyses meet (at the epiphyseal plate), longitudinal growth stops.

Foramen

A hole in a bone

Fossa

A flat area or depression in a bone

Process

Projection from bone, narrow or wide

Styloid

An especially long and skinny process

Meatus

A hole or tube like structure

Canal

A groove or tube like structure, a tunnel

Condyle

A knuckle like joint surface of a bone

Head

Round articular end of a bone

Tuber(cle/osity)

Roughened area for muscle attachment