Skeletal System: Bones and Bone Tissue

estrogen

a clss of female reproductive hormones that aids in bone growth

periosteum

a connective tissue membrane covering the outer surface of a bone

interstitial growth

chondrocytes in the center of the tissue divide and add more matrix in-between the existing cells

concentric lamellae

circular layers of bone matrix that surround the central canal

long, flat, short, irregular

classification of bone shape

epiphysis

part of a long bone that develops from a center of ossification distinct from that of the diaphysis

diaphysis

shaft composed primarily of compact bone, but it can also contain some spongy bone

zone of hypertrophy

the chondrocytes produced in the zone of proliferation mature and enlarge in this zone

articular cartilage

the end of a long bone covered with hyaline cartilage

centers of ossification

the locations in the membrane where ossification begins

collagen and proteoglycan

the matrix contains ___ and ___

bone remodeling

the process of removing old bone and adding new bone

osteoblasts, osteocytes, osteoclasts

three types of bone cells

hyaline cartilage, fibrocartilage, elastic cartilage

three types of cartilage

-blast

"seed" or "bud"

osteoclasts

- Bone-destroying cells - cells that perform reabsorption or breakdown

osteomalacia

- adult rickets - a softening of the bones due to calcium depletion.

interstitial lamellae

- between osteons - remnants of concentric or circumferential lamellae that were partially removed during bone remodeling

osteoblasts

- bone-forming cells - produces collagen and proteoglycans - also releases matrix vesicles

epiphyseal plate

- growth plate - located between the epiphysis and the diaphysis - where growth in the bone length occurs

long bones

- longer than they are wide - traditional model for overall bone structure

Type 1 osteogenesis imperfecta

- mildest and most common form of OI - caused by too little formation of normal type 1 collagen (collagen-deficiency)

circumferential lamellae

- outer surface of compact bone - thin plates that extend around the bone

perichondrium

- protective connective tissue sheath that covers most cartilage - double-layered outer layer of dense irregular connective tissue containing fibroblasts

osteoprogeterin (OPG)

- secreted by osteoblasts and other cells - inhibits osteoclast production by binding to RANKL

calcitonin

- secreted from thyroid gland when blood calcium ion levels are too high - inhibits osteoclast activity by binding to receptors on the osteoclasts

perforating fibers

- sharpey fibers - bundles of collagen fibers - strengthen the attachment of the tendons or ligaments to the bone

fontanels

- soft spots - larger, membrane-covered spaces between the developing skull bones that have not yet been ossified

ruffled border

- the osteoclast cell membrane then further differentiates into a highly folded form - reabsorption-specific area of the membrane

scurvy

- vitamin C deficiency - marked by ulceration and hemorrhage in almost any area of the body because normal collagen synthesis is not occurring in connective tissues

Gigantism

Abnormally increased body size due to excessive growth at the epiphyseal plates

Dwarfism

Abnormally small body size due to improper growth at the epiphyseal plates

greenstick fracture

An incomplete fracture on the convex side of the curve of the bone

every 10 years

BMU activity renews the entire skeleton

Osteogenesis imperfecta

Brittle bones that fracture easily due to insufficient or abnormal collagen

Rickets

Growth retardation due to nutritional deficiencies in minerals (Ca2+) or vitamin D; results in bones that are soft, weak, and easily broken

closed fracture

If the skin is not perforated

receptor activator of nuclear factor kappaB ligand

RANKL meaning

osteoporosis

Reduction in overall quantity of bone tissue

osteomalacia

Softening of adult bones due to calcium depletion; often caused by vitamin D deficiency

testosterone

a male reproductive hormone that aids in bone growth

callus

a mass of tissue that forms at a fracture site and connects the broken ends of the bone

autosomal dominant

a mutation in only one copy of the gene will cause OI, even if the other gene is normal

lacuna

a rounded cell that occupies a space within the matrix

endosteum

a single cell layer of connective tissue that lines th internal surfaces of all cavities within bones

secondary ossification centers

additional sites of ossification that are created in the epiphyses by osteoblasts

sinuses

air-filled spaces of some flat and irregular bones of the skull which are lined by mucous membranes

osteocyte

an osteoblast that has secreted enough bone matrix to become surrounded by it

spongy bone

appears porous, has less bone matrix and more space

approximately 6 months

average life span of a BMU

osteomyelitis, tuberculosis

bacterial infections

intramembranous ossification

begins approximately the eighth week of embryonic development and is completed by approximately 2 years of age

perforating canals (volkmann canals)

blood vessels from the periosteum or medullary cavity enter the bone through ___

appositional growth

chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage

osteomyelitis

bone inflammation often due to a bacterial infection that may lead to complete destruction of the bone

intramembranous ossification and endochondral ossification

bone patterns during fetal development

1. Hematoma formation 2. callus formation 3. callus ossification 4. Bone remodeling

bone repair steps (4)

bone remodeling

bone that becomes old is replaced with new bone

brittle

bone without collagen will be ___

flexible

bone without mineral will be ___

osteogenesis imperfecta

brittle bone disorder

chondrocyte

by the time the matrix has surrounded a chondroblast, the cell has differentiated into a ___

hyaline cartilage

cartilage mostly associated with bone

osteomalacia, osteoporosis

decalcification

connective tissue

developed embryologically from mesenchymal cells

medullary cavity

diaphyses of long bones tend to have a hollow center called ___

growth hormone

from the anterior pituitary increases general tissue growth, including overall bone growth, by stimulating interstitial cartilage growth and appositional bone growth

osteon or haversian system

functional unit of a long bone

1. Body support 2. Organ protection 3. Body movement 4. Mineral storage 5. Blood cell production

functions of skeletal system (5)

rickets

disease resulting from reduced mineralization of the bone matrix

incomplete fracture

does not extend completely across the bone

RANKL

expressed on the surface of the osteoblasts

nutrition, hormones

factors affecting bone growth

woven bone

first type of bone that osteoblasts form during ossification

ossification

formation of new bone by osteoblasts

external callus

forms a collar around the opposing ends of the bone fragments

internal callus

forms between the ends of the broken bone, as well as in the marrow cavity if the fracture occurs in the diaphysis of a long bone

gigantism, dwarfism, osteogenesis imperfecta, rickets

growth and developmental disorders

compact bone

has more matrix and is denser with fewer pores

irregular bones

have shapes that do not readily fit into the other three categories

creatingnew cartilage in the epiphyseal plate

how do long bones grow?

articular cartilage

hyaline cartilage that covers the ends of bones where they come together to form joints, has no perichondrium, blood vessels, or nerves

central canal

in a cross section, an osteon resembles a circular target (bull's eye)

Hairline fractures

incomplete fractures in which the two sections of bone do not separate

reproductive hormones

initially stimulate bone growth, which accounts for the burst of growth at puberty when production of these hormones increases.

hydroxyapatite

inorganic material that consists primarily of a calcium phosphate crystal

trabeculae

interconnecting rods or plates of bone

lamellae

lamellar bone sheets

hematoma

localized mass of blood released from blood vessels but confined within an organ or a space

Parathyroid hormone (PTH)

major regulator of blood calcium ion levels

proteoglycan

makes cartilage resilient by trapping water

lamellar bone

mature bone

35% organic, 65% inorganic

mature bone matrix material percentage ratio

increases osteoblast activity

mechanical stress applied to bone

yellow marrow

mostly adipose tissue

zone of resting cartilage

nearest the epiphysis and contains slowly dividing chondrocytes

vitamin C

necessary for collagen synthesis by osteoblasts

vitamin D

necessary for the normal absorption of calcium from the intestines

canaliculi

no blood vessels penetrate the trabeculae, so osteocytes must obtain nutrients through their ___

-blast to -cyte

once the immature cell has grown and differentiated into its mature form (suffix change)

Staphylococcus aureus

organism that causes osteomyelitis

epiphyseal line

ossified epiphyseal plate

diaphysis

primary ossification center

hyalin cartilage chondroblast

produces a matrix surrounding themselves

collagen

provides cartilage strength

flat bones

relatively thin shap, flattened shape and are usually curved

decreases osteoblast activity

removal of mechanical stress

thyroid hormone

required for normal growth of all tissues, including cartilage; therefore, a decrease in this hormone can result in a smaller individual

collagen and mineral components

responsible for the major functional characteristics of bone

short bones

round or nearly cube-shaped

red marrow

site of blood cell formation

bones, cartilage, tendons, ligaments

skeletal system components (4)

complicated fracture

soft tissues around a closed fracture are damaged

stem cells

some mesenchymal cells become ___

canaliculi

spaces occupied by osteocyte cell extensions

lacunae

spaces without matrix but occupied by the osteocyte cell bodies

endochondrial ossification

stars at approximately the eighth week of embryonic development, but this process might not begin in other cartilage until as late as 18-20 years of age

osteochondral progenitor cells

stem cells that can become osteoblasts or chondroblasts

tendons

strong bands of connective tissue that attaches skeletal muscles to bones

ligaments

strong bands of fibrous connective tissue that hold bones together

basic multicellular unit (BMU)

temporary assembly of osteoclasts and osteoblasts that travels through or across the surface of bone, removing old bone matrix and replacing it with new bone matrix

1. A hollow cylinder is lighter in weight than a solid rod 2. a hollow cylinder with the same height, weight, and composition as a solid rod, but with a greater diameter, can support much more without bending

two mechanical advantages of a long bone structure

appositional growth and interstitial growth

two types of cartilage growth

tuberculosis

typically, a lung bacterium that can also affect bone

zone of calcification

very thin and contains hypertrophied chondrocytes and calcified cartilage matrix

open fracture

when an open wound extends to the site of the fracture or when a fragment of bone protrudes through the skin

zone of proliferation

where chondrocytes produce new cartilage through interstitial cartilage growth

on the cell surfaces of osteoclast precursor stem cells

where to find RANK

inner layer of the perichondrium and in layers of connective tissue that cover bone

where you can find osteochondral progenitor