Chapter 6 - Bones and Bone Tissue

bone remodeling

ongoing replacement of old bone tissue by new bone tissue

hematoma

a solid swelling of clotted blood within the tissues.

How do each of the following dietary factors influence bone development? a) calcium ion intake b) vitamin D intake c) vitamin C intake d) vitamin K intake e) protein intake

a) calcium ion intake - if it's too low, bone depositioning won't take place b) prevents loss of calcium ions to the urine. The net effect on bone is to increase bone deposition and mass c) vitamin C - if intake is inadequate, collagen synthesjis in bone decreases d) vitamin K - increases bone deposition. It is key in production of calcium ion-binding glycoproteins by osteoblasts e) protein - necessary for osteoblasts to synthesize the collagen fibers needed for the organic matrix of the bone

What injury testifies to the fact that bones are: a)Well supplied with blood vessels b) innervated

a) extensive bleeding that occurs whenever a bone is injured b) they're supplied with many sensory fibers which is why we feel such an injury so accutely.

red bone marrow in adults: a) where is it located? b) why is it limited?

a) in bones and pelvis, proximal femur and humerus, vetebrae, ribs, sternum, clavicles, scapulae, certain bones of skull b) limited because adults are not actively growing and therefore do not need hematopoiesis to occur as rapidly

describe bone activity: a) in athletic person b) in sedentary person

a) place intense compression forces on his or her bones and therefore deposits more bone tissue, leading to higher bone mass b) decreases osteoblast activity but normal osteoclast activity

osteoclasts a) location b) derivation c) function

a) reside in shallow depressions on the internal or external surfaces of bone b) derived from the fusion of cells formed in bone marrow c) responsible for the process of bone resorption during which they break down the bone ECM. They accomplish this by secreting hydrogen ions and enzymes from the ruffled border which creates an acidic environment that disolves the inorganic matrix

lacunae characteristics: a. where are they located? b. what are they filled with? c. what cells reside there?

a. located between lamellae b. filled with ECF c. osteocytes reside there

describe the functions of the skeletal system: a. protection b. mineral storage c. acid-base homeostasis d. blood cell formation e. fat storage f. movement g. support

a. protection - protect the underlying organs b. mineral storage - most important store house in the body for minerals such as K, P, Mg salts c. acid-base homeostasis d. blood cell formation - house "red bone marrow" where "hematopoiesis" takes place e. fat storage - "yellow bone marrow" contains fat, adipocytes with stored triglycerides. Fatty acids from the breakdown of these can be released and used by cells for fuel if necessary f. movement - bones serve as a site of attachment for most skeletal muscles. When muscles contract, they pull on the bones which generates movement around a joint g. support - skeleton supports the weight of the body and provide its structural framework

what happens if you remove organic or inorganic matrix?

bone begins to weaken and any minor twisting may break it

open reduction

surgical realignment of broken bone ends

Describe the fairly simple structure of short/flat/irregular/sesamoid bones.

-no diaphyses or epiphyses. in result, they contain no medullary cavity, epiphyseal plates -covered with periosteum attached by perforating fibers and well supplied with blood vessels and nerves -outer layer of compact bone that surrounds the inner spongy bone

describe the process of fracture healing.

1. A hematoma fills the gap between the bone fragments. 2. Fibroblasts and chondroblasts infiltrate the hematoma and a soft callus forms 3. Osteoblasts build a bone callus. 4. The bone callus is remodeled and primary bone is replaced with secondary bone

explain three ways that growth hormones promote both longitudinal and appositional growth.

1. an increase in the rate of mitosis of chondrocytes in the epiphyseal plate. 2. an increase in the activity of osteogenic cells, including their activity in the zone of ossification 3. direct stimulation of osteoblasts in the periosteum, triggering appositional growth

list four critical processes of the body that calcium is needed for.

1. contraction of the heart 2. contraction of the skeletal muscles 3. transmission of nerve impulses 4. blood clotting

descibe two effects of testosterone on both growth.

1. it increases appositional bone growth causing bones in males to become much thicker and have greater salt deposits than bones in females. 2. also increases the rate of mitosis at the epiphyseal plate, and so the large increase in testosterone that occur during the teenage years are accompanied by "growth spurts"

List 5 reasons why there is a cycle in which bone is destroyed and then formed.

1. maintenance of calcium ion homeostasis 2. bone repair 3. replacement of primary bone with secondary bone 4. replacement of older, brittle bone with newer bone 5. bone adaptation to tension and stresses

Describe the 5 zones of cells in the epiphyseal plate, and what is happening in each zone? 1. reserve cartilage 2. proliferation 3. hypertrophy and maturation 4. calcification 5. ossification

1. reserve cartilage - contains cells that are not directly involved in bone growth but that can be called upon to divide if needed. 2. proliferation - actively dividing chondrocytes in lacunae divide and the cells above them become part of the next zone. 3. hypertrophy and maturation - contains mature chondrocytes that reach this zone and maturation enlarge and cease dividing. 4. calcification - contains dead chondrocytes, some of which are calcified that are too far from blood supply, so they die and their ECM accumulates calcium salt deposits 5. ossification - has calcified chondrocytes and osteoblasts that invade calcified cartilage and begin to lay down bone on top of it.

describe in detail the sequence of events of endochondral ossification process

1. the chondroblasts in the perichondrium differentiate into osteoblasts. 2. the bone begins to ossify from the outside: - osteoblasts build the bone collar on the external surface of bone - simultaneously the internal cartilage begins to calcify and the chondrocytes die 3. in the primary ossification center, osteoblasts replace the calcified cartilage with early spongy bone; the secondary ossification centers and medullary cavity develops 4. as the medullary cavity enlarges, the remaining cartilage is replaced by bone; the epiphyses finish ossifying

Weight of the bone

65% is inorganic 35% organic

what is the relationship between stress on the bone and bone deposition?

Bone depositioning occurs in proportion to stress on a bone Simply: the heavier load a bone must carry, the more bone tissue is deposited in that bone.

compare the effect of calcitonin and parathyroid hormone on blood calcium levels

Calcitonin decreases both the activity of osteoclasts and the formation of new osteoclasts, and it is not as potent a regulator of blood calcium ion concentration as is PTH.

lamellae

Concentric rings made up of groups of hollow tubes of bone matrix the collagen fibers run in opposite directions allowing the osteon to resist twisting and bending forces in more than one direction

in what cases are the bone ends united only by scar tissue or cartilage instead of bone?

If it is inadequately stabilized or immobilized, or if the blood supply to the bone is poor.

what is the function of the articular cartilage covering the epiphyses?

It allows bones to rub together with reduced friction at joints

How do lamellae of an osteon resemble the cross section of a tree?

Just as tree rings enable a tree to withstand a great deal of stress, the lamellar structure of compact bone greatly enhances its strength

what does our skeletal system include?

Made up of bones and joints, other supplemental tissues

Homeostasis!

Maintaining a constant level of calcium in the blood via a negative feedback loop

hormone

One of the main factors that influences bone growth. group of chemicals which are secreted by the cells of endocrine glands in the blood.

endochondral ossification: what is it? a. occurs in which bones? b. occurs during which stage of development? c. replaces which type of cartilage?

Process of transforming hyaline cartilage into bone. a. It occurs in all bones in the body below the head, except the clavicles b. it occurs in the fetal period and is completed by age 7 c. hyaline cartilage

calcitonin

Produced by the cells of the thyroid gland located in the anterior neck decreases both the activity of osteoclasts and the formation of new ones

skeletal system

Protects and supports body organs and provides a framework the muscles use to support movement.

what types of marrow fills the medullary cavity?

Red or yellow depending on the age of the person

what happens at about age 13-15?

The rate of mitosis slows, but the rate of ossification continues unabated.

define and describe the factors of homeostasis: a. set point b. stimulus c. receptor d. control center e. effector/response f. homeostasis and negative feedback loop

a. set point - decrease concentration of calcium ions in blood b. stimulus - blood calcium ion level is decreased below normal range c. receptor - parathyroid gland cells release parathyroid hormone into the blood d. control center - e. effector/response - parathyroid hormone stimulates effects that increase the blood calcium ion level f. homeostasis and negative feedback - the calcium ion concentration returns to normal homeostatic range, and negative feedback decreases parathyroid gland cell secretion of the parathyroid hormone

canaliculi: a. how are lacunae connected to each other? b. what type of cell extension extends through them and how does it function? c. how are they involved in nourishment of the osteocytes?

a. they are connected together by tiny canals called canaliculi b. cytoplasmic extensions that extend through the canaliculi to connect osteocyes to each other and to the blood supply c. they allow oxygen and nutrients from blood to reach every osteocyte

what is the joint surface of long bones covered with?

articular cartilage (hyaline)

what happens to the medullary cavity as the diaphysis grows in width?

as the bones grow in width, their marrow cavities enlarge as well.

what does the central canal contain?

blood vessels and nerves that supply the cells of osteon

When in adult development does bone deposition approximately equal bone resorption? What about during childhood?

bone deposition approximately equals bone resorption when the epiphyseal plates close and longitudinal growth ceases in childhood, depositioning far outweighs resorption as this is a period of active growth

intramembraneous ossification

bone formation occuring within membranes

osseous tissue

bone tissue which is a special connective tissue that consists mainly of ECM with small numbers of cells scattered throughout

what changes in the bone occur with osteoporosis? what are the risk factors?

bones become weak and brittle due to inadequate inorganic matrix in the bone ECM risks of fractures that heal more slowly when fractured

trabeculae

branching "ribs" of bone which project into the marrow cavity

fracture

broken bone

epiphyseal plate

cartilaginous area at the ends of long bones where lengthwise growth takes place in the immature skeleton (unossified)

acromegaly

causes an enlargement in bone. cartilage, and soft tissue

what is the predominant type of protein fiber in osteoid and how does its structure relate to its functions?

collagen fibers, which form cross-links with one another and help bone to resist torsion and tensile, and align with hydroxyapatite crystals, significantly enhancing the hardness of bone.

compare the structure of compact bone to spongy bone.

compact bone is made of osteons spongy bone is usually not the weightbearing part of the bone, so it does not have a dense structure like that of compact bone

what diseases require bone marrow transplantation? Why?

diseases of the blood such as leukemia, sickle-cell anemia, aplastic anemia they each have improperly functioning hematopoietic cells

irregular bones: characteristics, location, specific example

do not fit any other classes due to their irregular shapes vetebrae and facial bones ex. vetebrae, sacrum, coccyx

Bone is ____ _____. New bone is continually being ____ as older bone is ______ ______.

dynamic tissue. brown down.

hematopoiesis

formation of red blood cells

parathyroid glands

gland detects low levels of blood calcium, and released PTH into blood which stimulates osteoclasts to resorb bone which leads to calcium being released into blood. The blood level of the calcium goes up and are now stable

yellow bone marrow

gradually replaces red bone marrow in adult bones; functions as storage for fat tissue and is inactive in the formation of blood cells

epiphyseal line

growth plate remnant

compact bone: what is it, structure, and how this suits its functions

hard, dense outer bone which enables it to resist the majority of stresses placed on it.

medullary (marrow) cavity

hollow, cylindrical space within the diaphysis containing yellow or red bone marrow depending on the person's age

articular cartilage

hyaline cartilage that covers ends of bones in synovial joints

osteoblasts: what is it? a) location b) derivation c) function

immature bone building cells a) in the inner periosteum and endosteum b) derived from flattened cells called osteogenic cells, which differentiate into osteoblasts when stimulated by certain chemical signals c) bone building cells that perform the process of bone deposition, during which they build the bone ECM. They secrete the organic matrix and aid in the formation of the inorganic matrix

spongy (cancellous) bone: what is it, structure, and how this suits its functions

inner honeycomb-like bone which forms the framework of bone struts that allows it to resist forces in many directions and provides a place for the bone marrow to reside

appositional bone growth. describe the process.

involves addition of new layers on previously formed layers so that a bone grows in width as thickening of the compact bone of the diaphysis occurs, osteoclasts in the medullary cavity digest the inner circumferential lamellae, so that as the bones grow in width, their marrow cavities enlarge as well.

describe the arrangement of collagen fibers with respect to adjacent lamellae. How does this affect the characteristics of bone?

it allows the osteon to resist twisting and bending forces in more than one direction

What causes achondroplasia? (the most common cause of dwarfism)

it results from a defect

What is scurvy and how is it related to the collagen content of bones?

lack of vitamin C This leads to scurvy because vitamin C is necessary for collagen synthesis

What are the only bones that undergo longitudinal process?

long bones

long bones: characteristics, location, specific example

longer than they are wide (not named for size) found in most bones of the arms and legs as well as the bones of the hands, feet, fingers, and toes ex. humerus

how do testosterone and estrogen levels affect the bone?

male testosterone promotes bone deposition female estrogen depresses osteoclast activity

oteocytes: what is it? a) location b) derivation c) function

mature bone cells a) small cavity called the "lacuna" b) they are essentially osteoblasts that have been surrounded and trapped by secreted bone matrix in a small cavity known as the lacuna c) relatively inactive, but do secrete chemicals required for maintaining the ECM. They also appear to recruit osteoblasts to build up areas of the bone under tension

periosteum:

membrane composed of dense irregular connective tissue that is richly supplied with blood vessels and nerves and osteogenic cells firmly attached to underlying bone by collagen fibers called "perforating fibers" that penetrate deeply into matrix anchoring membrane to bone tissue

endosteum

membranous lining of the hollow cavity of the bone contains osteogenic cells

hydroxyapatite crystals

mineral that stores calcium and phosphorus

what characterizes the bone marrow of infants and young children and why? What type of bone marrow is predominant in adults?

most is red because their rapid rate of growth requires a constant supply of new blood cells yellow is the most predominant type in adults because it is not actively growing and do not need "hematopoiesis to occur as rapidly as needed in young children

short bones: characteristics, location, specific example

name of their shape rather than their size - they're as long as they are wide, or roughly cube-shaped found in the bones of the wrists and ankles ex. carpals, tarsals

bone resporption: 1. which cells are involved? 2. what do they secrete? 3. how are the inorganic and organic matrices degraded? 4. what happens to the breakdown products?

old bone continually broken down by osteoclasts that release hydrogen ions from their ruffled borders onto the bone ECM mostly done to get calcium and minerals 1. osteoclasts 2. Hydrogen ions 3. inorganic matrix degraded by the hydrogen ions that make the pH more acidic which breaks down pH sensitive hydroxyapatite crystals organic matrix degraded by osteocytes that secrete enzymes to catalyze reactions that degrade proteoglycans, glycosaminoglycans, and glycoproteins

describe the composition of organic and inorganic matrix

organic - (osteoid) consists of protein fibers, proteoglycans, glycosaminoglycans, glycoproteins, and bone-specific proteins. inorganic - calcium and phosphorus which exist as large molecules of hydroxapatite crystals.

Gigantism

people become very tall

closed reduction

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

Ossification (osteogenesis)

process of bone formation; begins in embryonic period and continues through childhood with most bones completing the process by age 7

longitudinal growth: what is it and how does growth occur in long bones

process that long bones use to lengthen via the division of chondrocytes in the "epiphyseal plate"

red bone marrow

produces red and white blood cells and platelets loose connective tissue supporting island of blood-forming or "hematopoietic" cells

what constitutes a healthy bone?

properly functioning cells, adequate quantities and quality of ECM. If not, bone disease nearly always results.

Epiphyses - what is it and structure ****

proximal and distal ends of the bone

parathyroid hormone (PTH)

raises blood calcium level involved in bone maintenance

where is the blood supply located in each of the bone types?

red - hematopoietic cells yellow - blood vessels

Maintaining homeostasis:

response to low blood calcium ion level by a negative feedback loop

describe the process of bone resorption by osteoclasts

secrete hydrogen ions and enzymes from region of the cell called the ruffled border. The Hydrogen ions create an acidic environment that dissolves the inorganic matrix, and enzymes break down the organic matrix

Diaphysis - what is it and structure ***

shaft of a long bone

Lacunae

small cavities in bone that contain osteocytes

nutrient foramen

small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment

sesamoid bones: characteristics, location, specific example

specific bones located within tendons - small, regular, flat, ovalshaped. - give tendons a mechanical advantage and provide better leverage for muscles, and also reduce wear and tear on tendon ex. patella (knee cap)

diploe

spongy bone in flat bones

whar is the primary treatment of fractures?

stabilization of the fracture, followed by immobilization

osteogenic cells

stem cells that differentiate into osteoblasts

how to prevent osteoporosis

stop smoking, increased exercise, consume more calcium

Osteon (Haversian system)

structural unit of compact bone each "tree" in a bone that resembles a forest is a unit

bone deposition: 1. which cells are involved? 2. where does it take place? 3. what do the osteoblasts do?

the addition of minerals and collagen fibers to bone by osteoblasts 1. carried out by osteoblasts 2. in the periosteum and endosteum 3. the osteoblass make the components of the organic matrix as well as facilitate the formation of the inorganic matrix --- they secrete certain proteoglycans and glycoproteins that bind to calcium ions and secrete vesicles containing it

describe what happens to the epiphyseal plate as mitosis slows.

the plate begins to shrink as the zone of proliferation is progressively overtaken by the zones of calcification and ossification. Eventually around 18-21, the zone of proliferation completely ossifies, which makes the plate "closed"

what causes gigantism and acromegaly? what is the difference between them?

the presence of excess growth hormone they each depend on when in life it develops, so... if excess is secreted before the epiphyseal plate closes, then gigantism occurs if excess secreted after then acromegaly occurs

perforating fibers (sharpey's fibers)

thick bundles of collagen that extend from the periosteum into the bone extracellular matrix

flat bones: characteristics, location, specific example

thin and broad These bones are thin, flat, and curved. They form the ribs, breastbone, bones of the pelvis, and skull. clavicles (collar bones)

canaliculi

tiny canals that connect lacunae to one another

osteoid

unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

all bones grow in...

width

Compact bone is built to ....

withstand great amounts of stress.