Chapter 7: bone tissue

formation of a calculus (calcified mass) in an otherwise soft organ such as a lung, brain, eye, muscle, tendon, or artery (arteriosclerosis)

Abnormal calcification (ectopic ossification)

brittle bone disease resulting from a defect in collagen deposition

Osteogenesis imperfecta

the most common bone disease Severe loss of bone density, brittle -Subject to pathological fractures of hip, wrist, and vertebral column

Osteoporosis

The most common and deadly form of bone cancer. It occurs most often in the tibia, femur, and humerus of males between the ages of 10 and 25. In 10% of cases, it metastasizes to the lungs or other organs; if untreated, death occurs within 1 year.

Osteosarcoma (osteogenic sarcoma)

-secreted by parathyroid glands on posterior surface of thyroid -released when calcium levels low in blood -raises calcium blood levels

Parathyroid hormone

transverse or diagonal passages that join central canals

Perforating (Volkmann) canal

-Lack of growth hormone -Normal proportions with short stature -stunts the growth of all of the bones

Pituitary dwarfism

endosteum

The central and perforating canals are lined with ______

connective tissue with the matrix hardened by calcium phosphate and other minerals

Bone (osseous tissue) as a tissue

the most active form of vitamin D

Calcitriol

the forerunner of most bones in embryonic and childhood development, covers many joint surfaces in the mature skeleton

Cartilage

Inhibits osteoclast activity, but if secreted in excess (Cushing disease), can cause osteoporosis by reducing bone deposition (inhibiting cell division and protein synthesis), inhibiting growth hormone secretion, and stimulating osteoclasts to resorb bone

Cortisol

in adults, a bony scar that marks where growth plate used to be

Epiphyseal line

deformity of spine due to vertebral bone loss

Kyphosis

involves surgical exposure of the bone and the use of plates, screws, or pins to realign the fragments

Open reduction

-branch of medicine dealing with prevention and correction of injuries and disorders of bones, joints, and muscles -Includes the design of artificial joints and limbs and the treatment of athletic injuries

Orthopedics

Excessive proliferation of osteoclasts and resorption of excess bone, with osteoblasts attempting to compensate by depositing extra bone. This results in rapid, disorderly bone remodeling and weak, deformed bones. Osteitis deformans usually passes unnoticed, but in some cases it causes pain, disfiguration, and fractures. It is most common in males over the age of 50.

Osteitis deformans

many different directions

spongy bone can receive force from ______

compact bone

spongy bone is always covered by

a break caused by abnormal trauma to a bone

stress fracture

trabeculae

the branch-like parts of spongy bone are called

support the weight of the body without sagging

the ceramic components enables a bone to ______

twisting, can only receive force from one direction

the diaphysis of a bone is not good at _____

articular cartilage (hyaline cartilage) -enables a joint to move far more easily than it would if one bone rubbed directly against the other

the ends of bones (joint surfaces) are covered in ____

endosteum

the marrow spaces in a flat bone are lined with _____

1/3, 2/3

the matrix of osseous tissue is ___ organic matter, and ____ inorganic

a degree of flexibility.

the polymer component enables the bone with _____

done growing

there is a epiphyseal line if we are _____

the bone's lines of stress

trabeculae develop along ______

the architecture of bone determined by mechanical stresses placed on it -"use it or lose it" -exercise stimulates osteoblasts -bony processes grow larger in response to mechanical stress -example: the trabeculae of spongy bone have developed along the lines of stress placed on the femur

Wolff's law of bone

-In the late teens to early twenties, all the cartilage of the epiphyseal plate is depleted. -primary and secondary marrow cavities now unite into one cavity (The junctional region where they meet is filled with spongy bone) -the site of the original epiphyseal plate is marked with a line of slightly denser -a person can grow no taller. -The epiphyseal plates close at different ages in different bones and in different regions of the same bone

at what age does the cartilage of the epiphyseal plate deplete

hypocalcemia

because calcitriol is all about resorbing calcium from bone, it is activated when the body is in _____

interstitial growth -Bone elongation is a result of cartilage growth within the epiphyseal plate

bone elongation by epiphyseal plates is called

puberty and adolescence

bone growth is especially rapid in _____

cells, fibers, and ground substance

bone is connective tissue consisting of ______

soft tissue occupying marrow cavities of long bones and small spaces of spongy bone

bone marrow

osteoblasts and osteoclasts -If a bone is little used, osteoclasts remove matrix and get rid of unnecessary mass -If a bone is heavily used, or a stress is consistently applied, osteoblasts deposit new osseous tissue and thicken the bone

bone remodeling is a collaborative action of __________

-exchanging minerals with tissue fluid -Disturbance of calcium homeostasis in skeleton disrupts function of other organ systems

bone tissue exerts a profound influence over the rest of the body by _____

individual bones that consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue

bones as a organ

30%

by age 70, the average loss of bone is what percent

-secreted by C cells (clear cells) of thyroid gland when blood calcium levels rise too high -lowers blood calcium concentration

calcitonin

bone deposition -provides adequate calcium and phosphate

calcitriol is also necessary for ______ and why

dietary intake, urinary and fecal losses, exchanges between osseous tissue

calcium homeostasis depends on a balance between _____

normally used to stabilize and immobilize healing bone

cast

in the center of a osteon, carries blood vessels and nerves

central canal

-The inner and outer boundaries of dense bone are arranged in circumferential lamellae that run parallel to the bone surface. - -fill outer region of dense bone

circumferential lamellae

procedure in which bone fragments are manipulated into their normal positions without surgery

closed reduction

a fracture in which a bone is broken into three or more pieces

comminuted fracture is one

layers of matrix concentrically arranged around a central (haversian) canal

concentric lamellae

-osteogenic cells give rise to osteoblasts (bone builders) -osteoblasts move to areas of growth or repair -osteocyte produced by osteoblast gets trapped in a lacuna, and becomes a mature bone cell

explain how a osteocyte comes to be

-bones are banks, the money is calcium and phosphate -osteoblasts make deposits from blood into bone -osteoclasts make withdrawls from bone into blood

explain the bank analogy regarding bones and calcium

-Osteoblasts of inner periosteum deposit osteoid tissue -Become trapped as tissue calcifies -Lay down matrix in layers parallel to surface, forms circumferential lamellae -Osteoclasts of endosteum enlarge marrow cavity so the bone isn't so thick

explain the process of appositional growth

1. hematoma formation. the hematoma is converted to granulation tissue by invasion of cells and blood capillaries 2. soft callus formation. deposition of collagen and fibrocartilage converts granulation tissue to a soft callus 3. hard callus formation. osteoblasts deposit a temporary bony collar around the fracture to unite the broken pieces while ossification occurs 4. bone remodeling. small fragments are removed by osteoclasts, while osteoblasts deposit spongy bone and then convert it to compact bone

explain the process of how a fracture heals

-Mesenchyme condenses into a soft sheet of tissue (membrane) permeated with blood vessels. Mesenchymal cells line up along the blood vessels, become osteoblasts, and secrete osteoid tissue (prebone) in the direction away from the vessel. Osteoid tissue resembles bone but is not yet calcified. -Calcium phosphate and other minerals crystallize on the collagen fibers of the osteoid tissue and harden the matrix. blood vessels and future bone marrow are squeeze into narrow spaces. Osteoblasts become trapped in their own hardening matrix, they become osteocytes. - more of the mesenchyme adjacent to the developing bone condenses and forms a fibrous periosteum on each surface. The spongy bone becomes a honeycomb of slender calcified trabeculae. -At the surfaces, osteoblasts beneath the periosteum deposit layers of bone, fill in the spaces between trabeculae, and create a zone of compact bone on each side. This process gives rise to the sandwichlike structure typical of a flat cranial bone—a layer of spongy bone between two layers of compact bone.

explain the process of intramembranous ossification

-Thin, curved plates -Protect soft organs

flat bones (description)

intramembranous ossification, intramembranous ossification and endochondral ossification

flat bones develop by ______, but long bones develop by a combination of _____ and ______

support protection movement electrolyte balance acid-base balance blood formation

function of the skeleton

a fracture in which the bone is incompletely broken on one side but merely bent on the opposite side (occurs often in youth)

greenstick fracture

tooth enamel

hardest substance in body

red blood cell production

hemopoiesis

-direction of fracture line -break in the skin -multiple pieces

how are fractures classified

1. Calcitriol raises the phosphate level by promoting its absorption from the diet by the small intestine. 2. Parathyroid hormone, on the other hand, lowers the blood phosphate level by promoting its urinary excretion.

how are phosphate levels of the blood controlled

-by epiphyseal plates -functions as growth zone where bone elongates

how do bones grow in length

These hormones stimulate multiplication of osteogenic cells, matrix deposition by osteoblasts, and chondrocyte multiplication and hypertrophy in metaphyses

how do growth hormones, estrogen, and testosterone promote ossification

Tooth moves because osteoclasts dissolve bone ahead of tooth; osteoblasts deposit bone behind the tooth

how do orthodontic appliances reposition teeth through resporption and deposition

1. Inhibits osteoclasts thereby reducing bone resorption 2. Stimulates osteoblasts to deposit calcium into bone

how does calcitonin lower blood calcium concentrations

slows bone resorption, but increases risk of breast cancer, stroke, and heart disease

how does estrogen replacement therapy help treat osteoporosis (and risks)

-Blood vessels, along with nerves, enter the bone tissue through nutrient foramina on the surface -These foramina open into the perforating canals that feed into the central canals -the innermost osteocytes around each central canal receive nutrients from these blood vessels and pass them along through their gap junctions to neighboring osteocytes

how does nurtirents from outside the bone enter the bone

1.Increases osteoclast population and bone resorption 2. Promotes calcium reabsorption by kidneys, so less lost in urine 3. Promotes the final step of calcitriol synthesis in the kidneys, enhancing calcium-raising effect of calcitriol 4. Inhibits collagen synthesis by osteoblasts, inhibiting bone deposition

how does the parathyroid hormone raise blood calcium levels

-Epidermal keratinocytes use UV radiation to convert 7-dehydrocholesterol to vitamin D3 -Liver adds hydroxyl group converting that to calcidiol -Kidney adds hydroxyl group converting that to calcitriol

how is calcitriol produced

in osteons (haversian systems) that include lamellae, central canals, and canaliculi

how is compact bone organized

-slivers of bone called spicules -thin plates of bone called trabeculae

how is spongy bone organized

it "tones" it down (tonin)

how to remember that calcitonin lowers blood calcium levels

crystallized calcium phosphate salt

hydroxyapatite

excessive calcium levels

hypercalcemia

deficient calcium in blood

hypocalcemia

osteoblasts are going to deposit bone by taking calcium out of the blood and putting it into bone

if the body is in hypercalcemia what's gonna happen to correct it

osteoclasts are going to resorb bone and make sure calcium gets into the blood

if the body is in hypocalcemia, what's gonna happen to correct it

red bone marrow

in between the marrow spaces of flat bones (spongy bone), what will you find

loss of organic matrix and minerals

in osteoporosis, bones lose mass and become brittle due to ____

osteons, central canals because all osteocytes are close to bone marrow

in spongy bone, there are few ____ and no _____

epiphyseal plate

in terms of the epiphysis, what would you see in a child

epiphyseal line

in terms of the epiphysis, what would you see in an adult

1. increase calcium absorption by small intestine 2. increases calcium resorption from the skeleton by stimulating osteoclasts 3. weakly promotes kidney resorption of calcium ions, so less is lost in urine

in what three ways does calcitriol increase blood calcium levels

rickets and osteomalacia

inadequate calcitriol results in ______

-85% hydroxyapatite -10% calcium carbonate -fluoride, sodium, potassium, magnesium

inorganic matter of bone tissue

Stimulates bone formation; significant bone loss occurs in untreated diabetes mellitus

insulin

-fill irregular regions between osteons -the remains of old osteons that broke down as the bone grew and remodeled itself.

interstitial lamellae

Elaborate shapes that do not fit into other categories

irregular bones (description)

hold bones together

ligaments

-Longer than wide -Rigid levers acted upon by muscles; crucial for movement

long bones (description)

space in the diaphysis of a long bone that contains bone marrow

medullary cavity

area between the epiphysis and diaphysis of a long bone

metaphysis

process in which calcium, phosphate, and other ions are taken from blood and deposited in bone

mineral deposition (mineralization)

process of dissolving bone and releasing minerals into blood

mineral resorption

the hardening process of bone

mineralization of calcification

fracture where the bone pieces remain in proper anatomical alignment

nondisplaced fracture

minute holes in bone surface that allows blood vessels to penetrate

nutrient foramina

a fracture in which the broken bone penetrates the skin

open/compound fracture

-syntesized by osteoblasts -Collagen, carbohydrate-protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins

organic matter of bone tissue

island of bone

ossification center

the formation of bone

ossification or osteogenesis

-bone-forming cells -Form single layer of cells under endosteum and periosteum on the bone surface -Nonmitotic-come only from osteogenic cells -Synthesize soft organic matter of matrix which then hardens by mineral deposition -Stress/fracture stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforces/rebuilds bone

osteoblasts

-bone dissolving cells found on bone surface -=develop from same bone marrow stem cells that give rise to blood cells (different origin from other bone cells) -Very large cells formed from fusion of several stem cells -Have multiple nuclei in each cell -Ruffled border (large surface area) faces bone -often reside in resorption bays (pits in bone surface) -Dissolving bone is part of bone remodeling

osteoclasts

-former osteoblasts that have become trapped in the matrix they deposited -reside in lacunae, and lacunae are connected by channels called Canaliculi -Cytoplasmic processes of osteocytes reach into canaliculi and contact processes of neighboring cells -Gap junctions allow for passage of nutrients, wastes, signals -Some osteocytes reabsorb bone matrix while others deposit it (contributes to the homeostatic maintenance of both bone density and blood concentrations of calcium and phosphate ions)

osteocytes

stem cells that develop from embryonic mesenchymal cells -found in the endosteum and inner layer of the periosteum -gives rise to most bone cell types

osteogenic cells

the study of bone

osteology

normal bone loss

osteopenia

break in a bone weakened by disease (such as bone cancer or osteoporosis) (Usually caused by a stress that would not break a healthy bone)

pathological fracture

layer of dense irregular connective tissue surrounding a bone that holds blood vessels in place and is where ligaments and tendons attach -Perforating fibers—penetrate into bone matrix -inner osteogenic layer of bone forming cells is important to the growth of bone and healing of fractures

periosteum

-chondroblasts lay down cartilage on top of epiphysis and at the top of the epiphyseal line -osteoblast follow behind and convert the cartilage to bone (spongy bone) -as long as the cartilage stays above the following osteoblasts, then bones grow -when chondroblasts slow down and osteoblasts speed up, the the epiphyseal plate closes and a line is formed -one needs a growth hormone for chondroblasts to build cartilage, so when we get older and have less growth hormone, chondroblasts slow down and osteoblasts speed up

process of interstitial growth by epihyseal plates

1. deposition of osteoid tissue into embryonic mesenchyme 2. calcification of osteoid tissue and entrapment of osteocytes 3. honeycomb of spongy bone with developing periosteum 4. filling of space to form compact bone at surfaces, leaving spongy bone in middle

process of intramembranous ossification (simplified)

-contains hemopoiectic tissue that produces blood cells -in every bone in a child -in a adult, confined to bone in skull, vertebrae, ribs, sternum, pelvic girdle, and proximal heads of humerus and femur

red bone marrow

a disease in kids caused by mineral deficiency and resulting in soft, deformed bones (lack of ceramic component, hydroxyapatite)

rickets

-Approximately equal in length and width -Glide across one another in multiple directions

short bones (description)

resorption and deposition

what 2 actions are part of bone remodeling

-length -width

what 2 directions do bones grow

ethmoid sphenoid vertebrae sacrum hyoid mandible maxilla

what are irregular bones

race, age, gender, smoking, diabetes mellitus, diets poor which are poor in: calcium, protein, vitamins C and D

what are risk factors in osteoporosis

-estrogen replacement therapy -drugs

what are some treatments for osteoporosis

bones and teeth

what are the most durable remains of a once living body

-intramembranous -endochondral

what are the two methods of ossification

vertebrae, ribs, sternum, scapula, pelvic girdle, and bones of the limbs

what bones are developed by endochondral ossification

cranial bones (roofing bones) ribs ilium sternum scapula

what bones are flat bone

fibula ulna radius humerus femur tibia metacarpals/tarsals phalanges

what bones are long bones

carpals tarsals patella (also a sesamoid bone)

what bones are short bones

-not enough calcification -low sunlight (not enought vitamin d production and therefore not enough calcium) -legs bow out -bones are not strong enough to support weight of body

what causes rickets

osteoblasts -proproduce collagen fibers that spiral the length of the osteon -Fibers become encrusted with minerals Hydroxyapatite crystals form

what cells are responsible for mineral deposition

preformed by osteoclasts at ruffled border -Hydrochloric acid (pH 4) dissolves bone minerals -Acid phosphatase enzyme digests collagen

what cells are responsible for mineral resorption

-flexibility -removed by baking -left over after soaking in acid -if bone was only organic matter, it wouldn't be sturdy enough to support the body

what characteristic does organic matter give to bone

-hardness, rigidity -removed by soaking in acid -left over after baking -if bone was only inorganic matter, it would be too brittle

what characteristics does inorganic matter give to bone

it is a combination of two basic structural materials hydroxyapatite/minerals =ceramic collagen= polymer

what do we mean when we say that bone tissue is a composite material

-Makes ion channels less responsive and thus nerve and muscle are less excitable -emotional disturbance, muscle weakness, sluggish reflexes, cardiac arrest

what does hypercalcemia cause

overly excitable nervous system and tetany (muscle spasms)

what does hypocalcemia cause

-the flat bones of skull and clavicle in fetus -thickens long bones throughout life

what does intramembranous ossification produce

strength to bone with minimal weight

what does spongy bone provide

Fosamax, Actonel: destroy osteoclasts

what drugs help treat osteoporosis

red bone marrow

what fills the spaces in spongy bone

3/4

what fraction of the skeleton's weight is compact bone

growth hormone, estrogen, testosterone

what hormones promote ossification

Repairs microfractures, releases minerals into blood, reshapes bones in response to use and disuse

what is bone remodeling responsible for

-calcium: contractions of heart and muscle tissue -synapses of nervous system -Phosphate: component of DNA, RNA, ATP, and pH buffers

what is calcium and phosphate important for ____

it is a parathyroid hormone derivative that increases density by 10% in one year it may promote bone cancer, so use is limited to 2 years

what is forteo and and how does it help treat osteoporosis

vitamin D deficiency, diarrhea, thyroid tumors, underactive parathyroid glands

what is hypocalcemia caused by

appositional growth

what is it called when a bone grows in thickness

two layers of compact bone enclosing a middle layer of spongy bone (bone surfaces are covered with periosteum)

what is meant by the phrase "flat bones have a sandwich-like construction"

osteomalacia

what is rickets called when it is in adults

prevention: exercise and a good bone-building diet between ages 25 and 40

what is the best treatment for osteoporosis

hyaline cartilage with transition zone on each side where cartilage is replace by bone (metaphysis is the zone of transition facing the marrow cavity)

what is the epiphyseal plate made out of

to raise blood calcium levels

what is the function of calcitriol

bones, cartilage, ligaments (made out of dense regular connective tissue)

what is the skeletal system composed of

spongy bone

what kind of bone is a epiphyseal line

yellow bone marrow

what kind of bone marrow do adults have in the medullary cavity

red bone marrow

what kind of bone marrow do children have in the medullary cavity

red bone marrow

what kind of bone marrow is found in spongy bone

it has carbon and hydrogen

what makes something organic

athletes and people engaged in heavy manual labor

what people have more bone mass/density

99% most exists as part of hydroxyapatite, but a little is in a form that is easily exchanged with the blood

what percent of the body's calcium is in bone

10%

what percent of the skeleton is remodeled each year

hormones -calcitriol, calcitonin, and parathyroid hormone

what three things regulate calcium homeostasis

Affects spongy bone the most since it is the most metabolically active

what type of bone does osteoporosis affect the most

as early as age 35

when do women begin to lose bone mass

when body is in hypercalcemia

when is calcitonin activated

in the diaphysis of long bones, covering edge of epiphysis (epiphyses for plural)

where can you find compact bone

center of ends/shafts of long bones, in the middle of nearly all other bones

where is spongy bone found

intramembranous ossification -the method of depositing new tissue on the bone surface even past the age where the bones can no longer grow in length

which process carries out appositional growth

membranes, cartilage

while intramembranous ossification turns _____ into bone, endochondral ossification turns ______ into bone

-estrogen maintains bone density in both sexes by inhibiting resorption by osteoclasts -when the ovaries cease to secrete estrogen, they are at higher risk for bone loss because the osteoclasts keep going and the osteoblasts slow down

why are postmenopausal women more at risk for osteoporosis

-only found in adults -fatty -does not produce blood -can transform back to red marrow in the event of chronic anemia

yellow bone marrow

endosteum

all spicules and trabeculae are covered with ____

buffers blood against large ph changes by altering phosphate and carbonate salt levels (ph of blood is 7.35-7.45)

explain "acid base balance" as a function of the skeleton

red bone marrow is the chief producer of blood cells (hematopoiesis or hemopoiesis)

explain "blood formation" as a function of the skeleton

calcium and phosphate levels

explain "electrolyte balance" as a function of the skeleton

limb movement, breathing, other movements depend on bone

explain "movement" as a function of the skeleton

of brain, spinal cord, heart, lungs

explain "protection" as a function of the skeleton

limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera

explain "support" as a function of the skeleton

-Long bones stop growing in childhood -normal sized torso, short limbs -Failure of cartilage growth in metaphysis -results from a spontaneous mutation that produces a dominant allele -Two people of normal height can therefore have a child with achondroplastic dwarfism. -The mutant allele is dominant, so the offspring of a heterozygous achondroplastic dwarf have at least a 50% chance of exhibiting dwarfism, depending on the genotype of the other parent.

achondroplastic dwarfism

hyaline cartilage

all bones begin as ____

1. Mesenchyme develops into hyaline cartilage with a perichondrium in the location of a future bone 2. in a primary ossification center near the middle of this cartilage, chondrocytes begin to inflate and die, while the thin walls between them calcify. The perichondrium begins producing osteoblasts. These deposit a thin collar of bone around the middle of the cartilage model. The former perichondrium is now considered a periosteum 3. Osteoclasts arrive in the blood form a primary marrow cavity. Osteoblasts arrive and deposit layers of bone lining the cavity, thickening the shaft. Cartilage death/calcification continues, with osteoclasts digesting it, enlarging the marrow cavity. The region of transition from cartilage to bone at each end of the primary marrow cavity is called a metaphysis. secondary ossification center in epiphysis appears 4. The secondary ossification center hollows out, forming a secondary marrow cavity in the epiphysis. At the time of birth, the bone has an enlarged primary marrow cavity, and a secondary marrow cavity in one epiphysis. 5. During infancy and childhood, the epiphyses fill with spongy bone. Cartilage is then limited to the articular cartilage covering each joint surface, and to an epiphyseal plate, a thin wall of cartilage separating the primary and secondary marrow cavities at one or both ends of the bone. The plate persists through childhood and adolescence and serves as a growth zone for bone elongation. 6. By the late teens to early twenties, all remaining cartilage in the epiphyseal plate is generally consumed and the gap between the epiphysis and diaphysis closes. The primary and secondary marrow cavities then unite into a single cavity.

describe the process of endochondral ossification

shaft of long bone, within it is the medullary cavity -provides leverage

diaphysis

The spongy layer in the cranium that absorbs shock

diploe

a fracture in which at least one piece is shifted out of alignment with the other

displaced fracture

a process in which a bone develops from a preexisting model composed of hyaline cartilage -begins around the sixth week of fetal development and continues into a person's 20s -Most bones of the body develop in this way, including the vertebrae, ribs, sternum, scapula, pelvic girdle, and bones of the limbs.

endochondral ossification

layer of reticular connective tissue lining the inside of the medullary cavity -has cells that dissolve osseous tissue and others that deposit it

endosteum

area of hyaline cartilage that separates epiphyses and diaphyses of children's bones -enables growth in length

epiphyseal plate

cartilage of epiphsyeal plate is gone

epiphyses close when ______

enlarged end of a long bone -strengthen joint and anchor for ligaments and tendons -provide added surface area for the attachment of tendons and ligaments

epiphysis (ses)