The Skeletal System and Integument Repair

osteon

functional unit of compact bone

lamella

ring of compact bone tissue

plural form of lamella

lamellae

lacunae

structure in compact bone that houses osteocytes

osteocytes were at one point

osteoblasts

canaliculi

structures that connect osteocytes to each other and blood vessels, allowing for nutrient exchange and cell signaling

osteocytes secrete and surround themselves with __ that calcified and trapped them in the lacuna

osteoid

central canal

canal in the center of the osteon that contains nerves and blood vessel supply running through compact bone

interstitial lamellae

lamellae that fill the space between osteons

circumferential lamellae

lamellae that run around the circumference of the entire diaphysis

the skeletal system consists of

bone organs and cartilage organs

cartilages provide

flexibility and resistance

three types of cartilage

hyaline, elastic, and fibrocartilage

where is hyaline cartilage found

• respiratory system (larynx, trachea, bronchi, and nasal cartilages)

• connecting ribs to sternum (costal cartilage)

• end of bones (articular)

• growth plates of long bones (epiphyseal bone)

elastic cartilage locations

epiglottis and external ear

fibrocartilage locations

• pubic symphysis

• intervertebral discs

• menisci of knees

what is cartilage matrix made of

• 80% water

• 20% collagens, elastic fibers, hyaluronic acid, chondrotins

cells of cartilages

• chondrocytes

• chondroblasts

chondrocytes

mature form of cartilage cells that maintain the matrix

chondroblasts

cells that produce the cartilage tissue matrix

calcification

calcium-phosphate replaces cartilage matrix

calcification makes cartilage

less resilient and more rigid

calcification is normal during

endochondral ossification, repair of bone fractures, and epiphyseal plates during bone growth

calcification can occur during

old age

appositional growth

growth from outside of cartilage inward; growth in thickness

interstitial growth

growth of cartilage from within; expand in length

cartilage is surrounded by the

perichondrium

perichondrium

layer of dense irregular tissue that covers cartilage and bones and contain mesenchymal cells

mesenchymal cells

stem cell precursors that produce osteoblasts and osteoclasts

bone (organ) functions

• support

• protection

• movement

• mineral storage

• blood cell formation

• triglyceride

• hormone production

osteocalcin

hormone that helps regulate insulin and glucose metabolism

long bone

longer than they are wide

short bone

cube-shaped

flat bone

thin and flattened

irregular bone

complex, unique shapes

tissues in bone (organ)

• osseous tissue

• nervous tissue

• fibrous, dense irregular connective tissue

• cartilages

• muscle tissue

• adipose tissue

• reticular connective tissue

where is reticular connective tissue found in bones

red bone marrow

hematopoiesis

red blood cell formation

compact bone

dense outer layer of bone; also called cortical or lamellar bone

spongy bone

inner layer of bone that is a honeycomb of ossified “struts”; also called trabecular or cancellous

where is adipose tissue located in bone organs

yellow marrow

purpose of adipose tissue in bone

triglyceride storage

periosteum

membrane that covers bones consisting of an outer fibrous layer (of dense irregular connective tissue) and an inner osteogenic layer with mesenchymal cells

epiphyses

enlargements of long bones that form articulations; “upon” growth

diaphysis

shaft of long bone that contains the medullary cavity; “apart” growth

endosteum

lines trabeculae of spongy bone (osteogenic layer)

what is on the outside of bone

periosteum and articular cartilage

cells of bone tissue

• osteoblasts

• osteocytes

• osteoclasts

• fibroblasts

osteoblasts

cells that produce new bone matrix

osteoclasts

cells derived from macrophages responsible for the reabsorption of bone

osteocytes

maintain bone matrix

fibroblasts

produce protein fibers

two parts of non-living bone matrix

organic and inorganic

organic component of non-living bone matrix

osteoid

osteoid

part of bone matrix made of ground substance and collagen fibers

osteoid is ___ of the volume of bone matrix

1/3

osteoid contains chemicals that

promote precipitation and calcification of the inorganic bone matrix

hydroxyapatites

inorganic component of bone matrix that is made of calcium phosphates and precipitates around collagen fibers

how much of the bone matric does hydroxyapatites make up

2/3

bone is very strong in

compression

bone is moderately strong in

tension

bone has marginal strength in

torsion and shear

when does skeletal development begin?

8 weeks of fetal development

endochondral ossification

converting a hyaline cartilage scaffold into bone tissue

intramembranous ossification

converting a fibrous dense connective tissue membrane into bone tissue

when does bone development end?

mid/late childhood

hypertrophy

enlargement

Steps for converting hyaline cartilage to osseous tissue

1. chondrocytes accumulate alkaline phosphate and enlarge

2. chondrocytes lyse and die, dumping alkaline phosphate onto cartilage matrix

3. vascular tissue and osteoprogenitor cells invade the calcified cartilage

4. osteoblasts secret osteoid and promote ossification

the enlargement of chondrocytes causes what type of growth

interstitial

The dumping of alkaline phosphate into the cartilage matrix promotes

calcification of cartilage

What forms the ossification center?

vascular tissue and osteoprogenitor cells invading the calcified cartilage

primary ossification

formation of the diaphysis during endochondral ossification

steps for endochondral primary ossification

1. perichondrium converts into periosteum

2. osteoblasts secrete osteoid, promoting calcification on the exterior margin of cartilage

3. hyaline cartilage is converted into bone tissues

4. periosteal bud invades the center of diaphysis

5. osteoblasts secrete osteoid and create spongy bone

6. bone tissue, interior of diaphysis, and bone collar thicken

7. osteoclasts remove bone tissue and form medullary cavity

primary ossification continues toward

the end of fetal development

thickening of the bone collar, bone tissue, and interior of diaphysis causes

spongy bone to be filled in and become compact

osteoblasts secreting osteoid and promoting calcification on the exterior margin of cartilage creates

the bone collar

what is the center of diaphysis made of

vasculature and osteoprogenitor cells

secondary ossification

formation of the epiphysis during endochondral ossification

when does secondary ossification begin

at the end of fetal development

what occurs during secondary ossification

hyaline cartilage remaining at the ends of the diaphysis is converted into osseous tissue

As the epiphyses ossify, hyaline cartilage remains at

articular surface and the epiphyseal (growth) plate

epiphyseal (growth) plate

interface of epiphysis with diaphysis

what forms the secondary ossification center

hyaline cartilage converted into osseous tissue

steps of intramembranous ossification

1. ossification center forms

2. osteoid calcifies matrix and osseous tissue thickens

3. osteoid is secreted around vasculature, creating spongy bone

4. bone tissue at periphery thickens, creating compact bone plates

5. mesenchyme and periphery condense, becoming the periosteum

6. osteoblasts continue to thicken the trabeculae

post-natal growth

growth of epiphyseal plate

what forms the ossification center in intramembranous ossification

mesenchymal cells becoming osteoblasts

zones of the epiphyseal plate

0. resting/quiescent zone

1. proliferation zone

2. hypertrophic zone

3. calcification zone

4. ossification zone

resting/quiescent zone

area where cartilage is inactive

proliferation zone

where chondrocytes undergo mitosis

hyperplasia

increase in cell number

where is the resting zone

the epiphysis side of the epiphyseal plate

the proliferation zone creates

interstitial growth and hyperplasia

hypertrophic zone

where chondrocytes accumulate alkaline phosphate and hypertrophy

hypertrophic zone creates

interstitial growth

calcification zone

where chondrocytes die and lyse, dumping alkaline phosphate onto the cartilage matrix

ossification zone

where osteoclasts dissolve calcified cartilage and osteoblasts secrete osteoid, producing bone tissue

osteoblasts secreting osteoid and producing bone tissue causes

elongation of the length of diaphysis

which zone “overruns” the other zones of the epiphyseal plate

ossification zone

rate of cartilage growth is equal to the rate of

ossification