SKELETAL SYSTEMHonors Anatomy & Physiology

I. CONNECTIVE TISSUE ASSOCIATED WITH SKELETAL SYSTEM

A. Supporting connective tissue1. Matrix- Contains numerous fibers & in some cases, insoluble salts

B. Cartilage – Support, framework, model for developing bone1. Chondrocytes – cartilage cell2. Matrix- firm gel containing chondroitin sulfates3. Hyaline cartilage

a) Flexible- closely packed collagen fibersb) Location (1) Ends of bones involved in movable joints(2) Connections between ribs and sternum

http://upload.wikimedia.org/wikipedia/commons/0/0f/Hyaline_cartilage.jpg

4. Elastic cartilagea) Elastic fibers- Dense

network; more flexible than hyaline cartilage

b) Location – outer ear, tip of nose

5. Fibrocartilagea) Collagen fibers- Very high

concentration; shock absorbtion

b) Location- Intervertebral discs, between knees, pelvic girdle

6. Lacks direct blood supplya) Slow to heal

b) Blood supply comes from connective tissue covering → perichondrium

C. Bone1. Osteocyte – bone cell2. Matrix – Collagen fibers plus

calcium salts

II. SKELETAL SYSTEM

A. 206 bones of the skeleton can be grouped into two divisions1. Axial Skeleton

a) Skullb) Vertebral columnc) Thorax

2. Appendicular Skeletona) Appendagesb) Structures by which appendages are

attached to the axial skeleton

III. Functions of the Skeletal SystemA. Support – framework for the bodyB. Protection – protection for soft tissues and organsC. Movement - attachment for skeletal musclesD. Hematopoiesis – blood cell productionE. Storage of minerals (calcium &

phosphorous) and lipids

IV. Macroscopic Structures of the BoneA. Types of bones

1. Long bones – longer than they are wide e.g. femur

2. Short bone – roughly cube-shaped e.g. carpal, tarsal

3. Flat bones – thin, flat & often curved

e.g. sternum, ribs, skull4. Irregular bones – odd shapes

e.g. os coxa, scapula, vertebrae

B. Structure of a typical long bone 1. Diaphysis – the shaft or body

2. Epiphysis – the end3. Metaphysis – the junction of diaphysis and epiphysis4. Medullary cavity – area within the diaphysis5. Periosteum – connective tissue on the outer portion; contains blood vessels6. Endosteum - connective tissue lining the

medullary cavity7. Articular cartilage – hyaline cartilage on the ends of the epiphysis

V. CELLS

A. Osteoblasts: Bone building, bone repairing cells in the periosteumB. Osteocytes: Mature bone cells within the bone matrix (lacunae)C. Osteoclasts: Bone destroying cells – causes reabsorption of bone

VI. TYPES OF BONE TISSUE

A. Compact Bone1. Location and distribution –

80% of total bone massa) On the outer surface of

all bones – smooth, white appearance

b) Makes up most of the diaphysis of long bones

FIG. 7.02

2. Structurea) Very dense, stress-bearingb) Haversian System = Osteon

(1) Haversian canal (osteonic canal) – carries nutrients and wastes to and from the osteocytes

(2) Lamellae: concentric cylinder –shaped calcified structure

(3) Lacunae – small spaces containing osteocyte

(4) Osteocyte – Bone cell that facilitates exchange of calcium between blood and bone

(4) Osteocyte – Bone cell that facilitates exchange of calcium between blood and bone(5) Canaliculi – canals connecting the lacunae together and to the Haversian canal

Haversian System (Osteon)

c) Nutrient foramen – opening in bone that allows passage of blood vessels and nervesd) Matrix – calcium and phosphorous saltse) Yellow marrow – Medullary cavity of long bones - fat storage

B. Cancellous Bone – Spongy Bone1. Location and distribution

a) The inner surface of all flat, irregular, and short

bonesb) The epiphysis of long bones

2. Structure - Trabeculaea) Porous – No Haversian systems b) Contains blood vesselsc) Red marrow – contains blood-

forming cells

VII. BONE DEVELOPMENTA. Endochondral Ossification: Long Bone Growth

1. Embryo at 6-8 weeks has hyaline cartilage skeleton – mostly appendicular skeleton

2. At 8-12 weeks blood vessel invades perichondriuma) Changes nutrition of chondrocytes

(cartilage is avascular!)b) Chondrocytes respecialize into

osteoblasts3. Osteoblasts lay down layer of compact

bone around diaphysis = bone collar

4. Chondrocytes starve, die and hypertrophy (swell up)

a) Release alkaline phosphataseb) Causes Ca2+ salts to be deposited and

form a weak spongy bone5. Blood vessels, nerves, osteoblasts, osteoclasts and red bone marrow invade

the bone and move to center of diaphysis

a) Known as Periosteal Budb) Sets up the Primary Ossification

Center (POC)

6. Primary Ossification Center (POC) sets up “shop”

a) Osteoclasts begin to eat weak spongy bone from dead cartilage, forming the

medullary cavityb) Ossification center begins

to move towards the epiphysis – “The Chase”7. Bone grows in length as POC chases growing cartilage

8. Secondary Ossification Centers (SOC) begin to form at the epiphysis (around birth)a) Different from POC in that osteoclasts do not eat spongy bone – instead, weak spongy bone is remodeled and strengthenedb) Grows toward diaphysis TRAPPING the cartilagec) Known as epiphyseal growth plate 9. Growth hormone from pituitary gland stimulates this band of cartilage to become mitotic – results in bone growth (Length)

10. Sex hormones can also influence rapid growth – ie. Growth spurts during

puberty

11. When growth hormone levels fall – POC meets SOC and they form the epiphyseal line – growth in length is over

12. Growth in Diameter of Long Bonea) Endosteum contains packets of

osteoclasts b) Periosteum contains packets of

osteoblastsc) Stress on Bones

(1) Pull of muscles and amount of weight carried puts stress on bones

(2) Areas of bone that receives more stress stimulates osteoblasts to lay down more bone

(3) Stress determines WHERE the bone will remodel

d) Calcium levels of the blood(1) Must be between 9 -11 mg/100mL

of blood for proper nervous and muscle tissue function

(2) Calcitonin (thyroid) lowers blood calcium levels by stimulating osteoblasts to build bone

(3) Parathyroid Hormone (PTH) raises blood calcium levels by stimulating osteoclasts to remove calcium salts from bone matrix and place it into blood

(4) Hormones determine WHEN the bone remodels

PTH CALCITONIN

Osteoclasts Osteoblasts ↑ Ca2+ Levels ↓ Ca2+ Levels in

bloodin blood

Ca 2+ Levels

9-11 mg/100 mL blood

B. Intramembranous Ossification1. Flat bones (skull) and some irregular bones2. Cells within the middle of the tissue respecialize into osteoblasts and cluster together3. Osteoblasts secrete bony matrix around the collagen fibers and form ossification center- -Trabeculae are formed.4. Periosteum forms on the outside of the fibrous membrane and produces compact bone5. Ossification center moves outward in all

directions until the cartilage is completely ossified

VIII. FRACTURES & HEALING

A. Fracture Type1. Simple fracture – no damage to other tissue

2. Compound fracture – break in the skin3. Comminuted fracture – number of parts4. Impact fracture – driven into each other5. Spiral fracture – twisted apart (torque)6. Greenstick fracture – partial break (young

bone)

B. Healing of Fractures1. Realignment of bones –

Reduction a) Open Reduction – surgery

required to realign bones (screws, plates, or rods may be needed)

b) Closed Reduction – No surgery needed

2. Hematoma forms around the broken ends of bone

3. Fibrocartilage callus formation a) Break bridged with fibrocartilage b) Stabilizes broken ends and sets up ossification4. Ossification a)Cartilage converted into bone5. Healing time depends on fracture type, age of patient6. Remodeling a) Denser matrix of bone kept where break occurs b) Gives extra strength to this area

IX. BONE MARKINGS

A. Function1. Muscle and ligament

attachment2. Form joints

BONE MARKINGS

Every bump, groove, and hole has a name on your bones

BONE MARKINGS

Two types of bone markings: Projections (aka processes) that grow out

from the bone

Depressions (cavities) that indent the bone

JOINT PROJECTIONS

1) Condyle: Rounded articular projection

Condyle

JOINT PROJECTIONS

2) Head: bony expansion on a narrow neck

3) Facet: smooth, nearly flat articular surface

JOINT PROJECTIONS

4) Ramus: Armlike bar of bone

LIGAMENT/TENDON PROJECTIONS

1) Crest: Narrow ridge of bone (Line: smaller than a crest)

2) Epicondyle: Raised area on or above a condyle

ULNA

3) Tubercle: Small rounded projection

4) Tuberosity: large rounded or roughened projection

5) Trochanter: very large, blunt projection

(only on femur)

Proximal Tibia

6) Spine: Sharp, pointed projection

Thoracic Vertebrae

DEPRESSIONS

Allow blood vessels or nerves to pass through.

1) Meatus: (me - A- tus) Canal or tube

DEPRESSIONS

2) Fossa: shallow basin

3) Fissure: narrow, slit-like opening

DEPRESSIONS

4) Sinus: Cavity within a bone; filled with air and lined with mucous membranes

5) Foramen: Round or oval opening

Foramen Magnum

DEPRESSIONS

6) Sulcus, Groove or Furrow: a shallow depression

REVIEW:

Projections1) Condyle2) Head3) Facet4) Ramus5) Crest6) Epicondyle7) Tubercle8) Tuberosity9) Trochanter10) Spine

Depressions1) Meatus2) Fossa3) Fissure4) Sinus5) Sulcus or Groove or Furrow