CHAPTER 6: SKELETAL SYSTEM: HISTOLOGY & DEVELOPMENT
I. SKELETAL SYSTEM:
A. TENDONS, LIGAMENTS, CARTILAGE & BONES
B. FXN:
1. SUPPORT/SHAPE
2. PROTECTION
3. LEVERS-MOVEMENT
4. MINERAL STORAGE
5. BLOOD CELL FORMATION
C. TENDONS - MUSCLE TO BONE LIGAMENTS - BONE TO BONE
- BOTH DENSE, REGULAR C.T.
- GROWTH:
APPOSITIONAL - FIBROBLASTS, OUTSIDE
INTERSTITIAL - FIBROCYTES, INSIDE
1. ROUND 1. FLATTER
2. COMPACT 2. LESS COMPACT
3. PARALLEL FIBERS 3. LESS PARALLEL FIBERS
4. STIFF, COLLAGEN, WHITE 4. LESS STIFF, ELASTIN, YELLOW
D. HYALINE CARTILAGE (Fig. 6.1, p. 173)
1. MORE H2O IN MATRIX, é RESILIENCY
2. PERICHONDRIUM - DOUBLE LAYERED, SURROUNDS
a. OUTER - FIBROBLASTS, DENSE, IRREG. C.T.
b. INNER - CHONDROBLASTS
3. CHONDROCYTES IN LACUNAE
4. GROWTH: APPOSITIONAL & INTERSTITIAL
II. BONE
A. HISTOLOGY
1. MATRIX – NONLIVING ( Fig 6.2, p. 174) – Strong yet flexible
- INORGANIC - HYDROXYAPATITE (65%), Calcium phosphate, STRENGTH
- ORGANIC - COLLAGEN (35%), FLEXIBILITY
2. OSTEOBLASTS - PRODUCE BONE (Fig. 6.3, p. 175)
3. OSTEOCYTES - MAINTAIN BONE, IN LACUNAE & CANALICULI
4. OSTEOCLASTS - BREAK DOWN BONE, from WBCs
B. CANCELLOUS/SPONGY BONE (Fig. 6.4, p. 177)
1. EPIPHYSIS OF LONG BONES, FLAT BONES, VERTEBRAE
2. LINE MEDULLARY CAVITY
3. TRABECULAE - beams lined w/ENDOSTEUM
C. COMPACT/DENSE BONE (Fig. 6.6, p. 178)
1. CANALS - transport & communication
a. CANALICULI - link OSTEOCYTES, small
b. CENTRAL/HAVERSIAN - blood & nerves, longitudinal
c. PERFORATING/VOLKMANN’S - blood & nerves, lateral
2. LAMELLAE - layers
a. CIRCUMFERENTIAL
b. CONCENTRIC = OSTEON around CENTRAL CANAL
c. INTERSTITIAL – remnants
D. SHAPE (Fig. 6.7, p. 179)
1. LONG - LIMBS
2. SHORT - CARPALS & TARSALS
3. FLAT - SKULL, RIBS, SCAPULA, STERNUM
4. IRREGULAR - VERTEBRAE, FACIAL
E. ANATOMY (Fig. 6.8, p. 180 & Tab. 6.1, p. 179)
1. DIAPHYSIS - SHAFT, COMPACT BONE
2. EPIPHYSIS - ENDS, CANCELLOUS BONE
3. EPIPHYSEAL/GROWTH PLATE - LINE WHEN GROWTH STOPS
4. MEDULLARY CAVITY
a. RED MARROW - RBCs, AXIAL BONES, PROX. LIMBS
b. YELLOW MARROW - FAT, APPENDICULAR
5. PERIOSTEUM - C.T. membrane around bone
- NOT at epiphyses
- ARTICULAR (HYALINE) CART. @ EPIPHYSES
a. OUTER - blood vessels & nerves
b. INNER - OSTEOBLASTS & some OSTEOCLASTS
6. ENDOSTEUM - lines MEDULLARY CAVITY & inner spaces
- OSTEOBLASTS & OSTEOCLASTS
III. BONE DEVELOPMENT = OSSIFICATION (* KNOW! Tab. 6.2, p. 181)
- COMPACT & CANCELLOUS
- MECHANISM OF BONE DEPOSITION SAME
- BONE FORMED BY ONE PROCESS INDISTINGUISHABLE FROM OTHER
- BONE REPLACES PRE-EXISTING C.T.
A. INTRAMEMBRANOUS - flat bones of skull & clavicle (Fig. 6.10, p. 182)
1. FIBROBLASTS - produce C.T. membrane & fibers
2. OSTEOPROGENITORS è OSTEOBLASTS
3. PERIOSTEUM - outer layer, double layered c.t. sheath
4. COMPACT - beneath PERIOSTEUM
5. CANCELLOUS - inner
6. OSSIFICATION CENTERS - joined @ FONTANELS (Fig. 6.11, p. 183)
B. ENDOCHONDRAL - most bones (Fig. 6.12, p. 184-185)
1. HYALINE CARTILAGE MODEL/TEMPLATE
2. PERICHONDRIUM è PERIOSTEUM è BONE COLLAR
3. CHONDROCYTES HYPERTROPHY (enlarge)è CALCIFIED CART. è die
4. VESSELS INVADE - OSTEOPROGENITORS IN è OSTEOBLASTS
5. OSTEOBLASTS INTO LACUNA è CANCELLOUS BONE
6. “ BENEATH PERIOSTEUM è COMPACT BONE
7. PRIMARY OSSIFICATION CENTER
a. EARLY FETUS
b. DIAPHYSIS
c. MEDULLARY CAVITY
8. SECONDARY OSSIFICATION CENTER
a. 1 MONTH BEFORE BIRTH
b. EPIPHYSIS è EPIPHYSEAL PLATE
IV. BONE GROWTH
A. APPOSITIONAL - é WIDTH/DIAMETER
1. PERIOSTEUM - OSTEOBLASTS ADD
2. MEDULLARY CAVITY - OSTEOCLASTS DISSOLVE
B. ENDOCHONDRAL - é LENGTH (Fig. 6.13, p. 185; Fig. 6.14, p. 186)
1. INTERSTITIAL GROWTH OF CART. @ EPIPHYSEAL PLATE
2. ENDOCHONDRAL OSSIFICATION OF CARTILAGE
3. STOPS @ 12-25 Y.O. - PLATE BECOMES LINE
V. FACTORS AFFECTING BONE GROWTH - GENETICS #1
A. STRESS
1. REMODELING (Fig. 6.19, p. 189)
2. IF NONE: a. OSTEOCLAST activity stays the same
b. OSTEOBLAST activity ê
c. LOSS OF BONE !
3. EXERCISE/STRESS é BONE HEALTH
B. NUTRITION - Ca+2 & phosphate in diet
1. IF VITAMIN D ê
a. ê Ca+2 ABSORPTION in intestines
b. OSTEOMALACIA - adults, soft bones
c. RICKETS - children, bowed bones
on the rise due to kids kept out of sun/sunblock used to êskin CA!
2. IF VITAMIN C ê
a. ê COLLAGEN synthesis
b. SCURVY - ê C.T. maintenance & repair, gums rot
C. HORMONES (Fig. 6.21, p. 192)
1. IF blood Ca2+é- CALCITONIN PROD. IF blood Ca2+ê - PTH PROD.
THYROID PARATHYROID
ê OSTEOCLASTS é OSTEOCLASTS - Ca+2 from bone
é OSTEOBLASTS – Ca+2 into bone ê OSTEOBLASTS
ê Ca+2 INTEST. UPTAKE é Ca+2 INTEST. UPTAKE
ê Ca+2 IN BLOOD é Ca+2 IN BLOOD
2. GROWTH HORMONE - é GENERAL SIZE & APPOSITIONAL GROW.
3. ê THYROID - ê CARTILAGE & C.T. GROWTH, shorter
4. SEX HORMONES
a. STIM. BONE GROWTH - BURST @ PUBERTY
b. é OSSIFICATION OF EPIPHYSEAL PLATES
c. ESTROGEN - quicker ossification, women shorter
- OSTEOPOROSIS - ê estrogen
d. TESTOSTERONE - slower ossification, men taller
VI. BONE FRACTURES & HEALING
A. FRACTURES (Fig. 6B, p. 193)
1. OPEN (COMPOUND) - surface
2. CLOSED (SIMPLE) - internal
3. COMPLETE - at least 2 parts
4. COMMINUTED - shattered
5. INCOMPLETE - a. GREENSTICK
b. HAIRLINE
6. IMPACTED - driven into another
B. HEALING (Fig. 6.20, p. 190)
1. HEMATOMA - CLOT
2A. INTERNAL CALLUS – between bone parts
a. FIBROBLASTS - fiber network
b. CHONDROBLASTS - FIBROCARTILAGE ISLETS
c. OSTEOBLASTS IN è CALCIFY & OSSIFY CALLUSè “WOVEN BONE
2B. EXTERNAL CALLUS – collar around fractured ends
a. CHONDROBLASTS è CARTILAGE
b. OSTEOBLASTS è “WOVEN BONE”
3. CARTILAGE & WOVEN BONE OSSIFIED èCANCELLOUS BONE
4. CANCELLOUS BONE REMODELLED è COMPACT BONE
5. OFTEN “SCAR” VISIBLE ON X-RAY, THICKER
6. SMALL BONES - 4 WEEKS
7. LARGE BONES - 6 WEEKS
VII. AGING
A. QUANTITY & QUALITYê AS AGE é
B. BRITTLE, ê in collagen