1

THE SKELETAL SYSTEMCHAPTER 5

2

VOCABULARY 5Aappositional growth lacunae articular cartilage ossification canaliculi osteoblasts comminuted fracture osteoclasts compact bone osteocytes compound fracture osteon (Haversian system)

compression fracture periosteum diaphysis rickets epiphyseal plate sesamoid bones epiphyses Sharpey's fibers greenstick fracture simple fracture hematopoiesis spongy bone (24)

3

I. Bones (overview)A. skeleton subdivisions1. axial skeleton – bones that form longitudinal axis of body2. appendicular skeleton – bones of limbs and girdlesB. bone functions1. supporta. forms internal frameworkb. supports and anchors all soft organs2. protectionprotect soft body organs3. movementattachment for skeletal muscles via tendons

4

4. storagea. stores fat in internal cavitiesb. storehouse for minerals (>

imp. is Ca & P)5. blood cell formation

a. also called hematopoiesisb. occurs in marrow cavities of

certain bonesc. red marrow blood cells

5

C. bone classification1. 2 basic types of bone (osseous) tissue:

a. compact bone – dense, looks smooth and homogeneous

b. spongy bone – composed of small needle-like pieces of bone &

open space2. classified according to shape:

a. long bones1. longer than they are wide2. have a shaft w/ heads @ both

ends3. bones of limbs (except wrist & ankle)

6

b. short bones1. usu. cube-shaped & spongy

bone2. bones of wrist & ankle3. sesamoid bones –

*special type of short bone *form w/i tendons (patella)

c. flat bones1. thin, flattened, usu. curved

2. layer of spongy bone b/t 2 layers of compact bone

3. most bones of skulld. irregular bones

1. vertebrae (make up spinal col.)

2. hip bones (coxal)

7

COLOR CODE – PLATE 18

Long – yellowShort – light greenFlat – purpleIrregular – light blueSesamoid – orangeAxial skeleton – redAppendicular skeleton - blue

8

D. Long bone structure1. gross anatomy

a. diaphysis*shaft*makes up most of bone’s

length*composed of compact bone

b. periosteum*protective membrane-

covering of diaphysisc. Sharpey’s fibers

*also called perforating fibers*c.t. fibers that secure

periosteum to bone

9

d. epiphyses*ends of long bones*area of spongy bone enclosed

in thin layer of compact bone

e. articular cartilage*covers external surface of

epiphyses*glassy hyaline cartilage*provides a smooth, slippery

surface to reduce friction @ joints

f. epiphyseal plate*flat plate of hyaline cartilage*seen in young, growing bone*causes lengthwise growth of a

long bone

10

g. medullary cavity*also called the yellow

marrow cav.*cavity of the shaft*adultsstorage area for

adipose tissue*infantscontains red marrow

& forms blood cells (adults: red marrow is found

only in spongy bone cavities of flat bones & epiphyses)

11

12

COLOR CODE - BONEEpiphysis – dark greenEpiphyseal line – light greenDiaphysis – brownArticular cartilage – purplePeriosteum – blueSpongy bone/red marrow – redCompact bone – pinkMedullary cavity/yellow marrow –

yellowNutrient artery - orange

13

2. microscopic anatomya. osteocytes

*mature bone cellsb. lacunae

*tiny cavities w/i matrix*contain osteocytes

c. lamella*concentric circles in wh/

lacunae are arrangedd. Haversian canals

*central canals around wh/ the lamella form

NOTE: see page 92 for micrograph of the structure of bone

14

e. osteon*also called Haversian system*each complex consisting of a central canal + matrix rings*canals run lengthwise carrying blood vessels & nerves to all areas of bonef. canaliculi*transportation system*connect bone cells to nutrient supply*radiate o/w from the central canals to all lacunae*reason bone cells are well nourished

15

16

17

18

3. bone markings (pg.134)a. fossa

*shallow, basinlike depression in a bone

*may serve as an articular surface

b. fissure*narrow, slit-like opening

c. foramen*round/oval opening through a

bone*for blood vessels &/ nerves

19

Fossa

Fissure

Foramen

20

E. Bone formation, growth, remodeling1. formation & growtha. ossification*process of bone formation*2 phases-osteoblasts (bone forming cells) cover hyaline cartilage-hyaline cartilage is digested away forming medullary cavityb. appositional growth*increase in diameter of bonec. osteoclasts*bone-destroying cells

21

22

2. bone remodelinga. nec. for bones to retain normal

prop. & strength as body increases in size & strength

b. PTH (parathyroid hormone)*determines when bone is to be broken down(body needs calcium)/formed (has to much Ca)*stresses (muscle pull, gravity) determine where bone matrix

is to be broken down/formedc. allows skeleton to remain as

strong & vital as possible during growth, injury, etc.

23

24

F. Problems1. Rickets

a. childhood disease in wh/bones fail to calcify

b. bones soften bowing of legsc. usu. due to lack of Ca or lack of

Vit. D wh/ is needed to absorb Ca into bloodstream

25

2. Fractures (bone breaks)a.simple (closed)

*bone breaks cleanly*does NOT penetrate the skin

b. compound (open)*bone ends penetrate through

the skin

Simple fractureCompound

fracture

26

c. comminuted fracture*bone breaks i/t many

fragments*common in elderly (bones are more brittle)

d. compression fracture*bone is crushed*common in porous bones

e. greenstick*incomplete break*common in children (flexible

bones)

comminuted

compression

Greenstick ----------

27

3. fracture repair (pg. 138) 4 mj. Events:

a.hematoma formsblood-filled swelling

b. break is splintered by a fibrocartilage callus

c. bony callus is formedfibrocartilage is gradually replaced by spongy bone

d. bone remodeling occurs

28