Bones of the Axial Skeleton

The Skeletal System

Bones, joints, and other associated tissues

Epiphysis

Ends of long bones

Diaphysis

Middle shaft of long bones

Spongy bone

Interior of epiphysis & lining the medullary cavity

Trabeculae

Network of bony struts in spongy bone

Red bone marrow

In the empty space of spongy bone

Axial Skeleton

Trunk

Appendicular Skeleton

Limbs

Long bone

Bone is longer than it is wide (Humerus)

Short bone

Bone is about as long as it is wide (Trapezium - carpal bone)

Flat bone

Bone is broad, flat, and thin (Sternum)

Irregular bone

Bone’s shape does not fit into other classes (Vertebra)

Sesamoid bone

Round, flat bone found within tendon (patella)

Inorganic Matrix

Makes bones hard - designed to resist compressive forces

Hydroxyapatite crystals

Composed of calcium & phosphorus salts (inorganic matrix)

Organic matrix

Contribute to bone’s ability to resist twisting forces and tension

Osteogenic cells

Stem cells of bones (first stage of bone cells)

Osteoblast

Immature cells that secrete the bony matrix → bone deposition

Osteocytes

Mature cells of bone, maintain bone tissue

Osteoclasts

Break down bone by secreting H+ and enzymes → bone resorption

Osteon

units of compact bone (tree trunks)

Central canal

Center of osteon → contains blood vessels and nerves

Lamellae

Rings around central canal

Lacunae

Holes where osteocytes sit

Canaliculi

Channels connecting lacunae (branches)

Interstitial lamellae

Rings around individual osteons

Circumferential lamellae

Rings around entire diameter of bones

Periosteum

Covers outer surface of bone → attachment site for tendons and ligaments; route for blood vessels to enter the bone

Perforating fibers

Connect periosteum to bone

Endosteum

Covers the interior of bone surfaces

Medullary cavity

Empty space in bone → can be filled with yellow bone marrow

Epiphyseal line

Remnants of the growth plate (lines between spongy bone near the epiphyses)

Growth plate

Area of hyaline cartilage from which longitudinal bone growth occurs

Joint

Where two or more bones come together

Synarthrosis

Joints allow no movement

Amphiarthrosis

Joints allow very limited movement

Diarthrosis

Freely movable joint

Fibrous joints

Two bones are separated by dense regular connective tissue

Suture

Fibrous → found between the bones of the skull

Syndesmosis

Fibrous → Articulating bones joined by long piece of dense regular connective tissue ex. tibia & fibula

Gomphosis

Fibrous - Occurs between the teeth and the maxilla or mandible

Cartilaginous joints

Two bones are joined by cartilage

Synchondrosis

Cartilaginous → bones are connected by hyaline cartilage (ex. ribs to sternum; costochondral)

Symphysis

Cartilaginous → bones are connected by fibrocartliage (ex. intervertebral bodies)

Synovial joints

Two bones are separated by a synovial cavity, lined by a synovial membrane and filled with synovial fluid

Planar

Synovial → nonaxial movement (movement does NOT occur in relation to axis)

Pivot

Synovial → uniaxial movement (movement occurs around one axis) (ex. Atlantoaxial)

Hinge

Synovial → uniaxial movement (ex. temporomandibular)

Saddle

Synovial → biaxial movement (movement occurs around two axes)

Condylar

Synovial → biaxial movement (ex. Atlanto-occipital)

Ball & Socket

Synovial → triaxial movement (movement around 3 axes)

Cranial Skull

Houses and protects the brain

A

Frontal Bone

B

Coronal Suture

C

Parietal Bone

D

Lambdoid Suture

E

Occipital Bone

F

Temporal Bone

G

Mastoid Process of the temporal bone

H

External acoustic meatus

I

Styloid process of the temporal bone

J

Zygomatic Process of the temporal bone

K

Squamous suture

L

Mandible

M

Maxilla

N

Zygomatic bone

O

Temporal process of the zygomatic bone

P

Sphenoid bone

Q

Lacrimal bone

R

Nasal bone

S

Zygomatic arch of the temporal bone

A

Frontal

B

Nasal bone

C

Zygomatic bone

D

Superior nasal concha

E

Inferior nasal concha

F

Maxilla

G

Vomer

A

Parietal bone

B

Sagittal suture

C

Lambdoid suture

D

Occipital bone

E

External occipital protuberance

A

Occipital bone

B

Magnum foramen

C

Occipital condyle (connects to C1)

D

Palatine bone

E

Maxilla

F

Sphenoid bone

G

Pterygoid process

A

Sella Turcica

B

Lesser wing

C

Greater wing

A

Coronoid process of the mandible

B

Mandibular condyle

C

Ramus of the mandible

D

Mandible

A

Malleus

B

Incus

C

Stapes