Skeletal System

Functions:

1. Support
2. Movement (Levers)
3. Protection (brain, thoracic)
4. Storage of Minerals
5. Hemopoiesis (blood cells synthesis)
   1. red marrow of bones
      1. sternum
      2. hip
      3. femur
      4. humerus (adult)

Classes of Bone (based on shape)

1. Long
   1. Examples: humerus, radius, phalanges
2. Short
   1. Examples: carpals, tarsals
3. Flat
   1. Examples: sternum, ribs, skullcap
4. Irregular
   1. Examples: vertebrae, pelvic girdle

Bone Tissue Type

1. Spongy ( Trabecular)
   1. located on epiphyses; interior of flat bones ( diploe)
2. Compact ( lamellar )
   1. located on diaphyses
   2. most dense

Bone Composition

1. Organic components
   1. collagen
   2. glycosaminoglycans
2. Inorganic components
   1. calcium phoshate salts
      1. withstand compression
3. Enzymes
   1. alkaline phosphatase
      1. promotes deposition of calcium salts in matrix

Anatomy of Bone

1. Structural unit = Osteon (haversian system)
   1. Lamellae (concentric layers)
2. Harversian,Volkmanns canals = Site for blood, nerve, lymph supply
3. Osteocytes reside in Lacunae, connected via Canaliculi
4. Other Terms:
   1. endosteum
   2. periosteum
   3. medullary Cavity
   4. diaphyses
   5. epiphyses

Bone growth - Ossification of Cartilage

1. Length - at Epiphyseal Plate
2. Width - Appositional
   1. osteoblasts (increase) osteons on periosteum
   2. osteoclasts (increase) breakdown endosteum precursor is white blood cell

Bone Remodeling

1. Control mechanisms in adults
   1. hormones (Negative feedback loop )
      1. parathyroid (PTH)
         1. released when blood [Calcium] (decreases)
         2. increases Osteoclast activity
         3. resorption of bone
      2. calcitonin (thyroid gland)
         1. released when blood [Ca2+]
         2. increased bone deposition (osteoblasts)
         3. decreased resorption of bone
   2. response to mechanical stress
      1. where bone deposited
      2. 'piezoelectric effect'
      3. skeletal muscle pull, gravity stimulate
      4. Bone Mineral Content loss (BMC)
         1. micro-gravity lose 1% BMC per week
         2. hormonal (women peak BMC age 30) menopause decreases BMC
         3. osteoporosis - due to low Calcium intake (1500 mg)
            • other minerals
            • inactivity
            • low Estrogen
2. Hormonal control in youth bone growth
   1. growth Hormone (somatomedins)
      1. target is Epiphyseal Plate cartilage
   2. thyroid hormone
      1. potentiates GH
   3. sex hormones (testosterone/estrogen)
      1. responsible for growth spurt then close epiphyseal plates

Bone Markings

1. Openings (nerves/blood. vessels)
   1. foramen
   2. sinus
   3. meatus
2. Site for muscle attachment
   1. epicondyle
   2. spine
   3. trochanter
   4. tuberosity\tubercle
3. Projections forming joints
   1. condyle
   2. facet
   3. head
   4. fossa

Bones of the Skeleton- 206


1. Axial Skeleton
   1. includes skull, vertebrae, thorax
   2. 80 bones
   3. function to support & protect
2. Appendicular skeleton
   1. includes limbs, pelvic & pectoral girdle
   2. 126 bones
   3. articulate with axial skeleton at sacrum, sternum
   4. provides mobility and ability to manipulate via "opposable thumbs"

Skull Bones (29, 11 pairs)


1. Immovable Joints (sutures)
   1. at birth composed of fibrous connective tissue - fontanels ('soft spots')
      1. allow compressions during birth
      2. permit rapid brain growth in infancy
      3. aid in determining position of fetal head prior to birth
2. All skull bones have sutures except mandible
   1. sutures all articulate with Parietal bone
   2. frontal (coronal) suture
   3. sagittal suture
   4. lambdoidal suture
   5. squamosal suture
3. Calvarium ( skull roof)
   1. frontal bone -single anterior bone (forehead)
      1. contains sinuses, foramen
   2. parietal bones (2)
      1. articulate with other cranial bones
      2. located superiorally
   3. occipital bone (1)
      1. has foramen magnum (connects medulla to vertebrae)
      2. has 2 occipital condyles (articulates with C-1 -> nodding)
4. Cranial cavity floor (6 bones)
   1. temporal bones - ' temples'
      1. contains external auditory meatus, jugular foramen
   2. ethmoid - 'sieve'
      1. contains nasal cavities, nasal septum
   3. sphenoid
      1. complex butterfly shape
      2. 'keystone' of cranium
      3. sella turcica (pituitary gland) sits on sphenoid

Facial bones

1. Mandible - lower jaw
   1. strongest, largest of facial bones
   2. only "movable" bone (temporomandibular joint)
2. Maxilla - upper jaw
   1. keystone of face
   2. large sinuses
   3. articulates with temporal bone
3. Nasal bones(2)
   1. 'bridge' of the nose
4. Lacrimal bones (2)
   1. smallest facial bones
   2. form medial wall of orbits
   3. tear ducts
5. Vomer
   1. part of nasal septum (with ethmoid, septal cartilage)
   2. thin "plow-like"
6. Hyoid bone
   1. U shaped in neck (not true facial bone)
   2. no articulation with any other bone
   3. attachment for neck muscles, tongue
   4. fractured in strangulation
7. Paranasal sinuses
   1. ethmoid
   2. sphenoid
   3. frontal
   4. maxillae
8. Auditory ossicles
   1. malleus
   2. incus
   3. stapes


Vertebral column (26)

1. 4 regions:
   1. cervical (C1 - C7)
   2. thoracic (T1 - T12)
   3. lumbar ( L1 - L5)
   4. sacrum (S1- S5)
2. Vertebrae structure
   1. all have body (weight bearing)
   2. tranverse process
   3. spinous process
   4. vertebral foramen (spinal cord)
   5. intervertebral discs- fibrocartilage
3. Cervical Vertebrae
   1. C1 - Atlas
      1. no disc between C1 & C2
      2. carries skull (occipital)
      3. permits nodding
   2. C2 - Axis
      1. dens (tooth)
      2. permits rotation of head
   3. C2 - C6 bifid spinous process, large discs
   4. C7 prominent
4. Thoracic vertebrae: (12)
   1. articulate w/ ribs
   2. larger, downward spinous process
5. Lumbar
   1. largest, strongest centrum
   2. short, blunt spinous process
6. Sacral
   1. fused triangular
   2. form pelvic girdle w/ alae
7. Coccyx
   1. 'tailbone'
   2. no real physiological importance
8. Curves of Spine (4)
   1. concave posterior:
      1. cervical
      2. lumbar
   2. convex posterior:
      1. thoracic
      2. sacrum
   3. functions of curves
      1. increase strength
      2. maintain balance while upright
      3. shock absorb from walking
      4. less likely to fracture
   4. abnormal Curves
      1. scoliosis - abnormal lateral curve
         1. usually thoracic region
      2. lordosis - "swayback"
         1. exaggerated lumbar curve
      3. kyphosis - " hunchback"
         1. dorsal exaggeration of thoracic curve
         2. e.g. osteoporosis, rickets

Thoracic Cage


1. Components
   1. thoracic vertebrae
   2. ribs
   3. sternum - "breastbone"
   4. costal cartilages
2. Sternum
   1. manubrium (joins clavicle)
   2. body (joins ribs)
   3. xiphoid process (muscles)
3. Ribs
   1. 12 pair
   2. true ribs 1-7 attach to sternum
   3. false ribs 8-12 indirect attach to sternum
   4. floating ribs 11 & 12 no anterior attachment
4. Costal cartilages
   1. comprised of hyaline cartilage
   2. anchor ribs to sternum anteriorally
   3. allow expansion with respiration

Appendicular Skeleton

1. Major Components
   1. pectoral (shoulder) Girdle
   2. pelvic (hip) Girdle
   3. limbs (arm and legs)
2. Shoulder girdle
   1. joins axial skeleton at sternoclavicular joint
   2. clavicle - 'collar bone'
      1. S shape, acts as anterior brace
      2. sternal and acromial (scapula) end
      3. most frequently bone fractured
   3. scapula - 'shoulder blade'
      1. thin triangular bone (spade)
      2. glenoid fossa - articulates with humeral head
      3. acromion process ('point of shoulder' )
      4. coracoid process (beaklike)
      5. spine of scapula
   4. arm - humerus (only bone)
      1. head - located at proximal end
      2. contains anatomical neck, tubercles
      3. distal end condyles:
         1. medial - trochlea (ulna)
         2. lateral - capitulum (radius)
      4. forms elbow joint with ulna (olecranon fossa)
3. Forearm (2 parallel bones)
   1. radius
      1. located lateral , ' thumb' side
      2. head (proximal)
      3. styloid process (distal)
   2. ulna
      1. located medial, 'little finger' side
      2. proximal landmarks: olecranon, coronoid process
      3. distal landmarks: styloid process (more narrow)
   3. interosseous membrane connects ulna, radius
4. Hand
   1. wrist (carpals - 8 )
      1. scaphoid
      2. lunate
      3. triquetral
      4. wrist forms joint with radius
   2. palm (metacarpals - 5)
      1. numbered from lateral to medial (pinkie is #5)
   3. digits (phalanges - 14)
      1. thumb (pollex) contains only 2 phalanges
      2. other digits have 3 phalanges (proximal, intermediate, distal)
5. Pelvic girdle
   1. ossa coxae bones (pelvic or innominate)
      1. posterior articulation forms sacroiliac joint
   2. coxal bone (3 parts)
      1. fushion of bones after birth, but names are retained
      2. ilium- broad, superior - iliac crests
      3. ischium - strongest part of hip
         1. posterior, inferior location
         2. ischial tuberosity - bear weight of sitting
      4. pubis - anterior location
         1. landmark: pubic symphysis (join 2 coxal bones)
      5. other landmarks:
         1. acetabulum: deep cup articulates with femur (ball & socket)
         2. obturator foramen: large inferior opening, nerves & blood vessels pas
         3. gender difference in pelvic dimensions
            • males: Pubic arch ( acute angle )
            • narrower, heavier pelvis
6. Thigh ( Femur- largest, heaviest bone)
   1. head articulates with acetabulum
   2. contains fovea capitis (pit in head)
   3. landmarks:
      1. greater & lesser trochanters
      2. distal end Condyles- medial, lateral
7. Leg:
   1. tibia - 'shin bone'
      1. medial, weight bearing bone
      2. proximal end articulates with femur, fibula
      3. distal end articulates with talus, fibula
      4. tibial tuberosity (attachment for quadriceps)
      5. medial malleolus
   2. fibula
      1. slender, lateral bone
      2. non-weight bearing
      3. articulates with tibia both ends
      4. landmark: lateral malleolus
8. Foot (analogous to Hand)
   1. tarsals (7)
      1. largest
      2. talus- tibia, fibula articulation
      3. calcaneus
         1. achilles insertion
         2. located inferior aspect
   2. metatarsals (Sole)
      1. numbered laterally 1 to 5 (little toe = 5)
      2. distal end = ' ball of foot'
      3. disorder: Hallux Valgus
   3. phalanges (Toes)
      1. proximal, middle, distal except Hallux - Great Toe
9. Patella - Knee cap
   1. sesamoid bone (seed)
   2. embedded in tendon of quadriceps femoris