I. Divisions of the Skeletal System – total bones of 206

A. Axial skeleton

1. bones of the longitudinal axis of the body

2. includes ribs, breastbone, hyoid, bones of skull, and backbone

3. about 80 bones

* skull

# cranium – 8

# face – 14

* hyoid – 1

* auditory ossicles (3 in each ear) – 6

* vertebral column – 26

* thorax

# sternum – 1

# ribs – 24

B. Appendicular skeleton

1. bones of the appendages

2. includes upper and lower extremities (limbs) & bones of the girdles (which connect to Axial skeleton

3. about 126 bones

* pectoral girdles

# clavicle – 2

# scapula – 2

* upper extremities

# humerus – 2

# ulna – 2

# radius – 2

# carpals – 16

# metacarpals – 10

# phalanges – 28

* pelvic (hips) girdle

# coxal (+pelvic of hip) bone – 2

* lower extremities

# femur – 2

# fibula - 2

# tibia – 2

# patella – 2

# tarsals – 14

# metatarsals – 10

# phalanges – 28

II. Types of Bones

A. Long Bones

1. greater length than width

2. consist of diaphysis & variable number of epiphyses

a. one epiphysis in metacarpal, metatarsals & phalanges

b. femur has four

c. most have two

3. curved slightly for strength

B. Short Bones

1. somewhat cube-shaped & equal in length & width

2. mostly spongy bone with thin compact outer layer

3. examples – wrist and ankle bones

C. Flat Bones

1. thin & with two parallel plates of compact bone enclosing a layer of spongy bone

2. protect broad areas & provide extensive areas for muscle attachment

3. examples – cranial bones, sternum, ribs, scapulae

D. Irregular Bones

1. others with complicated shapes

2. examples – vertebrae & some facial bones

E. Another Classification System Based on Location 

1. sutural bones – between joints of some cranial bones

2. sesamoid bones – small bones in tendons

a. some in wrist

b. patellas

c. in general in high pressure areas but varies in different individuals

III. Surface Markings – structural features related to functions

A. Depressions & openings

1. Fissure – A narrow, cleft like opening between adjacent parts of bones through which blood vessels or nerves pass (e.g. superior orbital fissure of the sphenoid)

2. Foramen – An opening through which blood vessels, nerves, or ligaments pass (e.g. infraorbital foramen of the maxilla)

3. Meatus – a tubelike passageway running within a bone (e.g. the external auditory meatus of the temporal)

4. Paranasal sinus – an air-filled cavity within a bone connected to the nasal cavity (e.g. frontal sinus of the frontal bone)

5. Groove or sulcus – furrow or depression that accommodates a soft structure such as a blood vessel, nerve, or tendon (e.g. intertubercular sulcus of the humerus)

6. Fossa – a depression in or on a bone (e.g. mandibular fossa of the temporal bone)

B. Processes that form joints (note: processes are projections)

1. Condyle – a large, rounded articular prominence (e.g. medial condyle of the femur)

2. Head – a rounded articular projection supported on the constricted portion (neck) of a bone (e.g. head of the femur)

3. Facet – a smooth, flat surface (e.g. articular facet for the tubercle of rib on a vertebra)

C. Processes to which tendons, ligaments, and other connective tissues attach

1. Tubercle – a small, rounded process (e.g. greater tubercle of the humerus)

2. Tuberosity – a large, rounded, usually roughened process (e.g. ischial tuberosity of the coxal bone)

3. Trochanter – a large, blunt projection found only on the femur (e.g. greater trochanter of the femur)

4. Crest – a prominent border or ridge (e.g. illiac crest of the coxal bone)

5. Line – a less prominent ridge than a crest (e.g. linea aspera of the femur)

6. Spinous process – a sharp, slender process (e.g. spinous process of a vertebra)

7. Epicondyle – a prominence above a condyle (e.g. medial epicondyle of the femur)

Reminder about Textbook Study

As with other topics, your textbook has excellent presentations of the materials on the skeletal system. While you should focus on the specific material in the Notes on the Web, you should always use your textbook as a resource for illustrations and for understanding content that your notes cover.

As with all materials throughout the semester, you will have opportunities to ask questions or ask that any relevant material from your assignments be discussed in class.

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