Chapter 7: The Skeleton

I. The Skeleton A. 206 bones total divided into 2 main groups

1. Axial skeleton: skull, rib cage, spinal column 2. Appendicular skeleton: upper and lower limbs plus girdles (bones that

hold limbs to axial skeleton)

II. The Axial Skeleton A. Skull: body’s most complex bony structure

1. 22 bones in 2 sets: cranial and facial 2. Sutures: specialized joints that connect bones together 3. Cranium: encloses brain: 8 bones

a. Frontal bone 1) Anterior portion of cranium 2) Forms part of eye orbits 3) Contains frontal sinuses

b. Parietal bone: forms most of cranium, superior and lateral aspects c. Occipital bone 1) Posterior and inferior part of cranium

2) Foramen magnum: large opening for connecting brain stem to

spinal cord 3) Occipital condyles: articulate with C1 (atlas)

d. Temporal bone 1) Part of lateral aspects of skull 2) Squamous (thin) portion: forms part of zygomatic arch 3) Mandibular fossa: articulation point with jaw 4) Petrous region: thick portion, 2 main divisions

a) Tympanic region: contains middle and inner ear b) Mastoid region: mastoid process is attachment point for muscles

e. Sphenoid bone: butterfly shaped: part of cranial floor 1) Optic foramina: openings for optic nerves 2) Hypophyseal fossa: depression for hypophysis (pituitary)

f. Ethmoid bone: most of area between nasal cavity and eye orbits 1) Crista galli: upward projection that attaches to outer brain coverings 2) Cribiform plate: openings that allow olfactory neurons to pass into

nasal cavity 3) Perpendicular plate forms part of nasal septum

4. Sutures: immovable joints that connect skull bones a. Coronal: parietal and frontal b. Sagittal: parietals at the midline c. Lambdoidal: parietals and occipital d. Squamous: parietal and temporal

5. Facial bones: 14 bones a. Mandible (jaw): largest, strongest bone of the face b. Maxillary bones: fused along midline 1) Hold upper teeth 2) Anterior part of hard palate

c. Zygomatic bones: cheekbone d. Nasal bones: form bridge of nose e. Lacrimal bones: about size of fingernail: medial side of eye orbit f. Palatine bones: posterior third of the hard palate g. Inferior nasal conchae: lateral walls of nasal cavity h. Vomer bone: inferior part of nasal septum

6. Hyoid bone: does not articulate with any other bone a. Horseshoe shaped; attachment point for muscles of

the tongue b. Helps in the movement of the larynx: speech and swallowing

B. Vertebral column: commonly called spine (not technically correct)

1. Ligaments: anterior and posterior longitudinal ligaments run the length of the

column to help reinforce 2. Intervertebral discs: cartilage pads between vertebrae 3. General structure of vertebra:

a. Body (centrum): disc shaped, weight bearing anterior portion b. Vertebral arch: posterior part c. Vertebral foramen: opening for spinal cord formed by body and arch d. Pedicles: at the base of the arch e. Processes: bony projections 1) Spinous: projects posteriorly 2) Transverse: projects laterally

f. Articular surfaces: superior and inferior g. Intervertebral foramina: openings between adjacent vertebrae

4. Regions (divisions) and curvatures: (curvatures follow regions) a. 5 regions 1) Cervical: neck - (7 vertebrae): 2 special: C1 and C2

a) C1

b) C2

2) Thoracic vertebrae: (12): like the typical vertebra, but have costal facets for the ribs

3) Lumbar: (5): the largest and strongest of the vertebrae

4) Sacrum: (5 fused into1) - has superior articular surfaces

5) Coccyx: 3-5 fused into 1 called the tailbone

C. Bony thorax: thoracic cage 1. Sternum: breastbone - anterior midline of thorax 2. Ribs: 12 pairs

a. True ribs: vertebrosternal b. False ribs 1) Vertebrochondral 2) Vertebral

III. Appendicular skeleton A. Pectoral Girdle: holds the upper extremity to the axial skeleton

1. 3 reasons why upper extremity has such great mobility: a. Only one small articulation point: sternoclavicular joint

b. Scapula freely moves over posterior thorax

c. Socket is shallow and loose

2. Clavicle: collar bone a. Sternal end: connects to sternum 1) The only attachment point to axial skeleton

b. Acromial end: articulates with acromion of scapula

3. Scapula: shoulder blade a. Glenoid cavity: for humerus (arm bone) b. Acromion: large anterior process that articulates with clavicle

B. Upper limb 1. Arm: 1 bone: humerus: largest and strongest of upper limb

a. Head is proximal

b. Deltoid tuberosity: attachment point for deltoid muscle c. Distal end has 2 condyles: 1) Trochlea: articulates with ulna 2) Capitulum: articulates with radius

d. Epicondyles: points of muscle attachment

2. Forearm (antebrachium): 2 bones: radius and ulna a. Ulna: longer than radius and forms most of elbow: medial in anatomical

position 1) Olecranon process: articulates with trochlea 2) Head is distal 3) Plays no role in hand movement

b. Radius: lateral in anatomical position 1) Head is proximal

3. Hand: wrist, palm, and fingers a. Carpus (wrist): 8 bones in 2 rows of 4 each b. Metacarpus (palm): numbered 1 through 5; thumb to little finger 1) Head (distal), shaft, and base (proximal) 2) The head is the "knuckles" in a clenched fist

c. Phlanges: finger bones, fingers are digits 1) Each digit has 3 phalanges 2) Except digit 1 (thumb) has only proximal and distal

phalanges

C. Pelvic girdle (hip): formed by 2 bones: coxal (os coxae)

1. 2 coxal bones + sacrum = pelvis 2. Each coxal bone is divided in fetal skeleton into:

a. Ilium: largest flaring portion b. Ischium: posterior, inferior part of coxal bone 1) Thick part 2) Thinner ramus 3) Ischial tuberosities are inferior-most part

c. Pubis: anterior most part of coxal bone 1) Fibrocartilage disc: forms the midline of symphysis pubis

D. Lower Limb: thigh, leg and foot 1. Thigh: femur: largest, strongest bone in the body

a. Proximal head: articulates with acetabulum of coxal bone b. Bows medially c. Neck d. Greater and lesser trochanter e. Lateral and medial condyles f. Patellar notch

2. Leg: 2 bones: tibia and fibula: no movement between the two like in radius and

ulna a. Tibia: shin: medial bone of leg - supports entire weight from femur, transfers

weight to ankle

1) Shaft 2) Medial and lateral condyles proximally articulates

with femur 3) Tibial tuberosity 4) Medial malleolus forms medial bulge of ankle area

b. Fibula: does not bear any weight 1) Interosseous membrane holds fibula to tibia 2) Lateral malleolus

3. Foot: ankle, instep, and toes a. Tarsus: ankle 7 bones (8 were in carpus) 1) 2 largest tarsals support weight of body talus and

calcaneus (heel) 2) Achilles tendon

b. Metatarsus: (instep) 5 metatarsals (like metacarpals) 1) Numbered 1 through 5

c. Phalanges: toes: same structure as phalanges in fingers but smaller

E. Arches of the foot 3: allow "springiness" in foot 1. Medial longitudinal: digit 1 side of the foot 2. Lateral longitudinal: elevates foot just enough to

transfer weight to head of 5th metatarsal 3. Transverse: