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)