Baker Ch. 6

Front 1

Define Bone

Back 1

Organ made up of several different tissues working together. Bone (osseous) tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissure.

Front 2

What constitutes the skeletal system?

Back 2

The entire framework of bones and their cartileges.

Front 3

What is remodeling?

Back 3

the building of new bone tissue and breaking down of old bone tissue.

Front 4

Define Osteology

Back 4

The study of bone structure and the treatment of bone disorders.

Front 5

Describe 6 main functions of bone and skeletal system.

Back 5

1. Support
2. Protection
3. Assistance
4. Mineral storage and release
5. Blood cell production
6. Triglyceride storage

Front 6

Describe the function of support

Back 6

The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.

Front 7

Describe the function of protection

Back 7

The skeleton protects the most important internal organs from injury. For example, cranial bones protect the brain, vertebrae (backbones) protect the spinal cord, and the rib cage protects the heart and lungs.

Front 8

Describe the function of assistance in movement

Back 8

Most skeletal muscles attach to bones; when they contract, they pull on bone to produce movement

Front 9

Describe the function of mineral storage

Back 9

Bone tissue stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone. Bone tissue stores about 99 percent of total body calcium. On demand, bone releases minerals into the blood to maintain critical mineral balances and to distribute the minerals to other parts of the body

Front 10

Describe the function of blood cell production

Back 10

Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets in a process called hem opoiesis or hematopoiesis. Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and macrophages within a network of reticular fibers. It is present in developing bones of the fetus and in some adult bones, such as the hip bones (pelvic bones), ribs, sternum (breastbone), vertebrae (backbones), skull, and ends of the humerus (arm bone) and femur (thigh bone). In a newborn, all bone marrow is red and is involved in hemopoiesis. With increasing age, much of the bone marrow changes from red to yellow.

Front 11

Describe the function of triglyceride storage

Back 11

Yellow bone marrow consists mainly of adipose cells, which store triglycerides. The stored trigly cerides are a potential chemical energy reserve.

Front 12

Name the type of bones

Back 12

Long
Short
Flat
Irregular
Sesamoidal
Sutural

Front 13

Describe long bones

Back 13

have greater length than width and consist of a diaphysis (shaft) and a variable number of epiphyses or extremities (ends). They are slightly curved for strength. A curved bone absorbs the stress of the body's weight at several different points so that it is evenly distributed. If such bones were straight, the weight of the body would be unevenly distributed and the bone would fracture easily. Long bones consist mostly of compact bone tissue, which is dense and has smaller spaces, but they also contain considerable amounts of spongy bone tissue, which has larger spaces (see Figure 6.4). Long bones include the humerus (arm bone), ulna and radius (forearm bones), femur (thigh bone), tibia and fibula (leg bones), metacarpals (hand bones), metatarsals (foot bones), and phalanges (finger and toe bones).

Front 14

Describe short bones

Back 14

are somewhat cube‐shaped and nearly equal in length, width, and depth. They consist of spongy bone except at the surface, where there is a thin layer of compact bone. Examples of short bones are most carpal (wrist) bones and most tarsal (ankle) bones.

Front 15

Describe Flat bones

Back 15

are generally thin and composed of two nearly parallel plates of compact bone enclosing a layer of spongy bone. The layers of compact bone are called external and internal tables. In cranial bones, the spongy bone is referred to as diploe [Pronunciation] (DIP‐lō‐ē) (see Figure 6.6). Flat bones afford considerable protection and provide extensive areas for muscle attachment. They include the cranial (skull) bones, which protect the brain; the sternum (breastbone) and ribs, which protect organs in the thorax; and the scapulae (shoulder blades).

Front 16

Describe irregular bones

Back 16

have complex shapes and cannot be grouped into any of the three categories just described. They also vary in the amounts of spongy and compact bone they contain. Such bones include the vertebrae (backbones), certain facial bones, and the calcaneus (heel bone).

Front 17

Describe sesamoid bones

Back 17

develop in certain tendons where there is considerable friction, compression, and physical stress. They are not always completely ossified and measure only a few millimeters to centimeters in diameter except for the two patellae (kneecaps), the largest of the sesamoid bones. Sesamoid bones vary in number from person to person except for the patellae, which are located in the quadriceps femoris tendon (see Figure 11.24a, b) and are normally present in all individuals. Functionally, sesamoid bones protect tendons from excessive wear and tear, and they often change the direction of pull of a tendon, which improves the mechanical advantage at a joint.
In the upper limbs, sesamoid bones usually occur only in the joints of the palmar surface of the hands. Two frequently encountered sesamoid bones are in the tendons of the adductor pollicis and flexor pollicis brevis muscles at the metacarpophalangeal joint of the thumb (see Figure 8.6a). In the lower limbs, there are two constant sesamoid bones in addition to the patellae; these occur on the plantar surface of each foot in the tendons of the flexor hallucis brevis muscle at the metatarsophalangeal joint of the great (big) toe (see Figure 8.12b).

Front 18

Describe sutural bones

Back 18

or wormian bones (named after a Danish anatomist, O. Worm, who lived from 1588 to 1654) are small bones located within the sutures (joints) of certain cranial bones (see Figure 7.5a). The number of sutural bones varies greatly from person to person.

Front 19

Diaphysis (long bone)

Back 19

is the bone's shaft, or body—the long, cylindrical, main portion of the bone.

Front 20

epiphyses (long bone)

Back 20

or extremities are the proximal and distal ends of the bone

Front 21

metaphyses (long bone)

Back 21

are the regions between the diaphysis and the epiphyses. In a growing bone, each metaphysis contains an epiphyseal (growth) plate (ep‐i‐FIZ‐ē‐al), a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length (a process described later in this chapter). When bone growth in length stops somewhere between the ages of 18 and 21, the cartilage in the epiphyseal plate is replaced by bone and the resulting bony structure is known as the epiphyseal line

Front 22

epiphyseal line (long bone)

Back 22

cartilage in the epiphyseal plate is replaced by bone and the resulting bony structure is known as the epiphyseal line

Front 23

articular cartilage (long bone)

Back 23

is a thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation (joint) with another bone. Articular cartilage reduces friction and absorbs shock at freely movable joints. Because articular cartilage lacks a perichondrium and lacks blood vessels, repair of damage is limited.

Front 24

periosteum (long bone)

Back 24

is a tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage. It is composed of an outer fibrous layer of dense irregular connective tissue and an inner osteogenic layer that consists of cells. Some of the cells enable bone to grow in thickness, but not in length. The periosteum also protects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons. The periosteum is attached to the underlying bone by perforating (Sharpey's) fibers, thick bundles of collagen that extend from the periosteum into the bone extracellular mat

Front 25

perforating (sharpey's) fibers

Back 25

The periosteum is attached to the underlying bone by perforating (Sharpey's) fibers, thick bundles of collagen that extend from the periosteum into the bone extracellular mat

Front 26

meduallary cavity (long bone)

Back 26

or marrow cavity, is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults. This cavity minimizes the weight of the bone by reducing the dense bony material where it is least needed. The long bones' tubular design provides maximum strength with minimum weight.

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endosteum (long bone)

Back 27

is a thin membrane that lines the medullary cavity. It contains a single layer of bone‐forming cells and a small amount of connective tissue.

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surface markings or osseous landmarks

Back 28

The surface of a bone is marked by a variety of bumps, grooves, indentations, projections, and holes

Front 29

Fissure

Back 29

Narrow slit between adjacent parts of bones through which blood vessels or nerves pass

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foramen

Back 30

Opening through which blood vessels, nerves, or ligaments pass

Front 31

fossa

Back 31

Shallow depression (fossa=trench

Front 32

sulcus

Back 32

Furrow along a bone surface that accommodates a blood vessel, nerve, or tendon

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meatus

Back 33

Tubelike opening

Front 34

processes

Back 34

Projections or outgrowths on bone that form joints or attachment points for connective tissue, such as ligaments and tendons.

Front 35

condyle

Back 35

Large, round protuberance with a smooth articular surface at the end of a bone

Front 36

depressions and openings

Back 36

Sites allowing the passage of soft tissue (nerves, blood vessels, ligaments, tendons) or formation of joints

Front 37

facet

Back 37

Smooth, flat, slightly concave or convex articular surface

Front 38

head

Back 38

Usually rounded articular projection supported on the neck (constricted portion) of a bone

Front 39

Processes that form attachment points for connective tissue:
crest

Back 39

Prominent ridge or elongated projection

Front 40

Processes that form attachment points for connective tissue:
epicondyle

Back 40

Typically roughened projection above a condyle

Front 41

Processes that form attachment points for connective tissue:
line

Back 41

Long, narrow ridge or border (less prominent than a crest)

Front 42

Processes that form attachment points for connective tissue:
spinous process

Back 42

Sharp, slender projection

Front 43

Processes that form attachment points for connective tissue:
trochanter

Back 43

Very large projection.

Front 44

Processes that form attachment points for connective tissue:
tubercle

Back 44

Variable sized rounded projection

Front 45

Processes that form attachment points for connective tissue:
tuberosity

Back 45

Variable sized projection that has a rough, bumpy surface

Front 46

The extracellular matrix contains

Back 46

15 percent water, 30 percent collagen fibers, and 55 percent crystallized mineral salts. [Dry bones (the nonliving bones that are studied in the laboratory) are 60 percent inorganic minerals and 40 percent organic substances by weight.] The most abundant mineral salt is calcium phos phate [Ca3(PO4)2]. It combines with another mineral salt, calcium hydroxide [Ca(OH)2], to form crystals of hydroxyapatite [Ca10(PO4)6(OH)2]

Front 47

Calcification

Back 47

mineral salts are deposited in the framework formed by the collagen fibers of the extracellular matrix, they crystallize and the tissue hardens.

Front 48

bones hardness depends on

Back 48

the crystallized inorganic mineral salts

Front 49

Bones flexability depends on

Back 49

its collagen fibers.

Front 50

tensile strength is provided by
(resistance to being stretched or torn)

Back 50

collagen fibers

Front 51

what are the 4 type of cells that make up bone?

Back 51

Osteogenic cells, osteoblasts, osteocytes, osteoclasts

Front 52

What is the functional significance of the periosteum

Back 52

The periosteum is essential for growth in bone thickness, bone repair, and bone nutrition. It also serves as a point of attachment for ligaments and tendons.

Front 53

osteogenic cells

Back 53

are unspecialized bone stem cells derived from mesenchyme, the tissue from which almost all connective tissues are formed. They are the only bone cells to undergo cell division; the resulting cells develop into osteoblasts. Osteogenic cells are found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels.

Front 54

osteoblasts

Back 54

are bone‐building cells. They synthesize and secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue, and they initiate calcification. As osteoblasts surround themselves with extracellular matrix, they become trapped in their secretions and become osteocytes. (Note: Cells with the suffix blast in bone or any other connective tissue secrete extracellular matrix.)

Front 55

osteocytes

Back 55

mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood. Like osteoblasts, osteocytes do not undergo cell division. (Note: Cells with the suffix cyte in bone or any other tissue maintain the tissue.)

Front 56

osteoclasts

Back 56

huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell), are concentrated in the endosteum. The plasma membrane of an osteoclast is deeply folded into a ruffled border on the side of the cell that faces the bone surface. Here the cell releases powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying extracellular matrix of bone. This breakdown of the extracellular matrix of bone, termed resorption (re‐SORP‐shun), is part of the normal development, growth, maintenance, and repair of bone. (Note: Cells with the suffix clast in bone break down extracellular matrix.) As you will see later, osteoclasts help regulate blood calcium level in response to certain hormones. They are also the target cells for drug therapy used to treat osteoporosis.

Front 57

resorption

Back 57

cell releases powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying extracellular matrix of bone. This breakdown of the extracellular matrix of bone, termed resorption

Front 58

cells with suffix blast in bone or any other connective tissue...

Back 58

secrete extracellular matrix

Front 59

cells with suffix cyte in bone or any other tissue...

Back 59

maintain the tissue

Front 60

cells with the suffix clast in bone...

Back 60

break down extracellular matrix

Front 61

a mneomic that will help you remember the difference b/w the functions of osteoblasts and osteoclasts is as follows:

Back 61

osteoBlasts Build bone, OsteoClasts Carve out bone

Front 62

compact bone

Back 62

also referred to as cortical or dense bone, is the type of bone tissue observed at the surface of a bone, but it also can extend deeper into the bone tissue. It makes up the bulk of the diaphyses of long bones

Front 63

compact bone is composed of repeating structural units called

Back 63

osteons or havarian system

Front 64

each osteon consists of concentric lamellae arranged around a

Back 64

Central canal

Front 65

concentric lamellae

Back 65

are circular plates of mineralized extracellular matrix of increasing diameter, surrounding a small network of blood vessels, lymphatics, and nerves located in the central canal (Figure 6.4a). These tube‐like units of bone generally form a series of parallel cylinders that, in long bones, tend to run parallel to the long axis of the bone

Front 66

lacunae

Back 66

Between the concentric lamellae are small spaces which contain osteocytes

Front 67

canaliculi

Back 67

radiating in all direction from the lacunae are tiny canaliculi, which are filled with extracellular fluid.

Front 68

interstitial lamellae

Back 68

The areas between neighboring osteons contain lamellae called which also have lacunae with osteocytes and canaliculi. Interstitial lamellae are fragments of older osteons that have been partially destroyed during bone rebuilding or growth.

Front 69

spongy bone tissue

Back 69

also referred to as trabecular or cancellous bone tissue, does not contain osteons
Spongy bone tissue is always located in the interior of a bone, protected by a covering of compact bone. It consists of lamellae that are arranged in an irregular pattern of thin columns called TRABECULAE

Front 70

the macroscopic spaces in trabeculae are filled with

Back 70

red bone marrow in bones that produce blood cells, and yellow bone marrow (adipose tissue) in other bones.

Front 71

Each trabecula consists of...

Back 71

concentric lamellae, osteocytes that lie in lacunae, and canaliculi that radiate outward from the lacunae

Front 72

spongy bone is different that compact bone in two ways:

Back 72

Light which allows for easier movement

trabeculae support and protect the red bone marrow.

Front 73

bone scan

Back 73

is a diagnostic pro cedure that takes advantage of the fact that bone is living tissue. A small amount of a radioactive tracer compound that is readily absorbed by bone is injected intravenously. The degree of uptake of the tracer is related to the amount of blood flow to the bone. A scanning device (gamma camera) measures the radiation emitted from the bones, and the information is translated into a photograph that can be read like an x‐ray on a monitor

Front 74

periosteal arteries

Back 74

small arteries accompanied by nerves, enter the diaphysis through numerous perforating (Volkmann's) canals and supply the periosteum and outer part of the compact bone

Front 75

nutrient artery

Back 75

Near the center of the diaphysis, a large nutrient artery enters the compact bone at an oblique angle through a hole called the nutrient foramen

Front 76

what is the path of the artery through the bone?

Back 76

The path of the artery through the bone is always away from the dominant growth end of the bone. (This is true of all the long bones of the limbs. To help you learn and remember this, use the following learning device: nutrient canals always “go to the elbow and flee the knee,”

Front 77

metaphyseal arteries

Back 77

enter the metaphyses of a long bone and, together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyses.

Front 78

epiphyseal arteries

Back 78

enter the epiphyses of a long bone and supply the red bone marrow and bone tissue of the epiphyses.

Front 79

veins that carry blood away from long bones are evident in three places:

Back 79

(1) One or two nutrient veins accompany the nutrient artery and exit through the diaphysis; (2) numerous epi physeal veins and metaphyseal veins accompany their respective arteries and exit through the epiphyses; and (3) many small periosteal veins accompany their respective arteries and exit through the periosteum. The periosteum surrounding the bone has numerous lymphatic capillaries and lymph vessels, but there is no evidence of any lymphatic vessels within the bone tissue.

Front 80

the process by which bone is formed is called

Back 80

ossification

Front 81

Intitial bone formation in an embryo and fetus

Back 81

The embryonic “skeleton” is at first composed of mesenchyme in the general shape of bones. These become the sites where subsequent cartilage formation and then ossification occurs. (Recall that mesenchyme is a connective tissue found mostly in an embryo and is the tissue from which most other connective tissues develop.) This begins during the sixth week of embryonic development and follows one of two patterns. Intramembranous ossification and endochondral ossification

Front 82

Where do periosteal arteries enter bone tissue?

Back 82

Periosteal arteries enter bone tissue through perforating (Volkmann's) canals.

Front 83

intramembranous ossification

Back 83

bone forms directly within mesenchyme, which is arranged in sheetlike layers that resemble membranes

Front 84

endochondral ossification

Back 84

bone forms within hyaline cartilage that develops from mesenchyme.

Front 85

what are the 4 steps of intramembranous ossifacation?

Back 85

1. Development of the ossifciation center
2. calcification
3. Formation of trabeculae
4. Develpment of the periosteum

Front 86

Development of the ossification center

Back 86

At the site where the bone will develop, specific chemical messages cause the mesenchymal cells to cluster together and differentiate, first into osteogenic cells and then into osteoblasts. The site of such a cluster is called an ossification center. Osteoblasts secrete the organic extracellular matrix of bone until they are surrounded by it.

Front 87

calcification

Back 87

Next, the secretion of extracellular matrix stops and the cells, now called osteocytes, lie in lacunae and extend their narrow cytoplasmic processes into canaliculi that radiate in all directions. Within a few days, calcium and other mineral salts are deposited and the extracellular matrix hardens or calcifies (calcification).

Front 88

formation of trabeculae

Back 88

As the bone extracellular matrix forms, it develops into trabeculae that fuse with one another to form spongy bone around the network of blood vessels in the tissue. Connective tissue that is associated with the blood vessels in the trabeculae differentiates into red bone marrow.

Front 89

Development of the periosteum

Back 89

In conjunction with the formation of trabeculae, the mesenchyme at the periphery of the bone condenses and develops into the periosteum. Eventually, a thin layer of compact bone replaces the surface layers of the spongy bone, but spongy bone remains in the center. Much of the newly formed bone is remodeled (destroyed and reformed) as the bone is transformed into its adult size and shape.

Front 90

What are the six steps of endochondral ossification?

Back 90

1. development of the cartilage model
2.Growth of the cartilege model
3.Development of the primary ossification center.
4. Development of the medullary (marrow) cavity.
5. Development of the secondary ossification centers.
6. formation of articular cartilage and the epipyseal (growth) plate.

Front 91

development of the cartilage model

Back 91

At the site where the bone is going to form, specific chemical messages cause the mesenchymal cells to crowd together in the general shape of the future bone, and then develop into chondroblasts. The chondroblasts secrete cartilage extracellular matrix, producing a cartilage model consisting of hyaline cartilage. A covering called the perichondrium [Pronunciation] (per‐i‐KON‐drē‐um) develops around the cartilage model.

Front 92

growth of the cartilage model

Back 92

Once chondroblasts become deeply buried in the cartilage extracellular matrix, they are called chondrocytes. The cartilage model grows in length by continual cell division of chondrocytes, accompanied by further secretion of the cartilage extracellular matrix. This type of cartilaginous growth, called interstitial (endogenous) growth [Pronunciation] (growth from within), results in an increase in length. In contrast, growth of the cartilage in thickness is due mainly to the deposition of extracellular matrix material on the cartilage surface of the model by new chondroblasts that develop from the perichondrium in a process called appositional (exogenous) growth (a‐pō‐ZISH‐i‐nal), meaning growth of the outer surface (described shortly).
As the cartilage model continues to grow, chondrocytes in its midregion hypertrophy (increase in size), and the surrounding cartilage extracellular matrix begins to calcify. Other chondrocytes within the calcifying cartilage die because nutrients can no longer diffuse quickly enough through the extracellular matrix. As these chondrocytes die, the spaces left behind by the dead chondrocytes merge into small cavities called lacunae

Front 93

development of the primary ossification center

Back 93

Primary ossification proceeds inward from the external surface of the bone. A nutrient artery penetrates the perichondrium and the calcifying cartilage model through a nutrient foramen in the midregion of the cartilage model, stimulating osteogenic cells in the perichondrium to differentiate into osteoblasts. Once the perichondrium starts to form bone, it is known as the periosteum [Pronunciation] . Near the middle of the model, periosteal capillaries grow into the disintegrating calcified cartilage, inducing growth of a primary ossification center, a region where bone tissue will replace most of the cartilage. Osteoblasts then begin to deposit bone extracellular matrix over the remnants of calcified cartilage, forming spongy bone trabeculae. Primary ossification spreads from this central location toward both ends of the cartilage model.

Front 94

development of the medullary (marrow cavity)

Back 94

As the primary ossification center grows toward the ends of the bone, osteoclasts break down some of the newly formed spongy bone trabeculae. This activity leaves a cavity, the medullary (marrow) cavity, in the diaphysis (shaft). Eventually, most of the wall of the diaphysis is replaced by compact bone

Front 95

development of the secondary ossification centers.

Back 95

When branches of the epiphyseal artery enter the epiphyses, secondary ossification centers develop, usually around the time of birth. Bone formation is similar to what occurs in primary ossification centers. However, in the secondary ossification centers spongy bone remains in the interior of the epiphyses (no medullary cavities are formed here). In contrast to primary ossification, secondary ossification proceeds outward from the center of the epiphysis toward the outer surface of the bone.

Front 96

Formation of articular cartilage and the epiphyseal (growth) plate.

Back 96

The hyaline cartilage that covers the epiphyses becomes the articular cartilage. Prior to adulthood, hyaline cartilage remains between the diaphysis and epiphysis as the epiphyseal (growth) plate, the region responsible for the lengthwise growth of long bones that you will learn about next.

Front 97

the growth in length of a long bone involves

Back 97

1. interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate
2.replacement of cartilage with bone by endochondral ossification on the diaphyseal side of the epiphyseal plate.

Front 98

epiphyseal (growth) plate

Back 98

is a layer of hyaline cartilage in the metaphysis of a growing bone that consists of four zones

Front 99

what are the 4 zones of hyaline cartilage in the metaphysis of a growing bone?

Back 99

1. Zone of restin cartilage
2. Zone of proliferating cartilage
3. Zone of hypertrophic cartilage
4. Zone of calcified cartilage

Front 100

Zone of resting cartilage

Back 100

This layer is nearest the epiphysis and consists of small, scattered chondrocytes. The term resting is used because the cells do not function in bone growth. Rather, they anchor the epiphyseal plate to the epiphysis of the bone.

Front 101

zone of proliferating cartilage

Back 101

Slightly larger chondrocytes arranged like stacks of coins undergo interstitial growth as they divide and secrete extracellular matrix. The chondrocytes in this zone divide to replace those that die at the diaphyseal side of the epiphyseal plate.

Front 102

zone of hypertrophic cartilage

Back 102

This layer consists of large, maturing chondrocytes arranged in columns.

Front 103

zone of calcified cartilage

Back 103

The final zone of the epiphyseal plate is only a few cells thick and consists mostly of chondrocytes that are dead because the extracellular matrix around them has calcified. Osteoclasts dissolve the calcified cartilage, and osteoblasts and capillaries from the diaphysis invade the area. The osteoblasts lay down bone extracellular matrix, replacing the calcified cartilage by the process of endochondral ossification. As a result, the zone of calcified cartilage becomes “new diaphysis” that is firmly cemented to the rest of the diaphysis of the bone.

Front 104

What activities of the epiphyseal plate account for the lengthwise growth of the diaphysis?

Back 104

The lengthwise growth of the diaphysis is caused by cell divisions in the zone of proliferating cartilage and replacement of the zone of calcified cartilage with bone (new diaphysis).

Front 105

epiphyseal plate closes how much sooner in females?

Back 105

1-2 years

Front 106

bone can grow in thickness only by

Back 106

appostitional growth
1. ridges in periosteum create groove for periosteal blood vessel.
2. periosteal ridges fuse, forming an endosteum-lined tunnel
3. osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon.
4. Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels.

Front 107

How does the medullary cavity enlarge during growth in thickness?

Back 107

The medullary cavity enlarges by activity of the osteoclasts in the endosteum

Front 108

paget's dx

Back 108

there is an excessive proliferation of osteoclasts so that bone resorption occurs faster than bone deposition. In response, osteoblasts attempt to compensate, but the new bone is weaker because it has a higher proportion of spongy to compact bone, mineralization is decreased, and the newly synthesized extracellular matrix contains abnormal proteins. The newly formed bone, especially that of the pelvis, limbs, lower vertebrae, and skull, becomes enlarged, hard, and brittle and fractures easily

Front 109

antireabsorptive drugs

Back 109

slow down the progression of bone loss

Front 110

bone‐building drugs

Back 110

promote increasing bone mass. Among the antireabsorptive drug

Front 111

stress fracture

Back 111

a series of microscopic fissures in bone that forms without any evidence of injury to other tissues. Formed from strenous activitys

Front 112

open fracture

Back 112

the broken ends of the bone protrude through the skin. conversely, a Closed (simple) fracture does not break the skin

Front 113

comminuted

Back 113

The bone is splintered, crushed, or broken into pieces at the site of impact, and smaller bone fragments lie between the two main fragments.

Front 114

greenstick

Back 114

A partial fracture in one side of the bone is broken and the other side bends; similar to the way a green twig breaks on one side while the other side stays whole, but bends; occurs only in children, whose bones are not fully ossified and contain more organic material than inorganic material.

Front 115

impacted

Back 115

One end of the fractured bone is forcefully driven the interior of the other.

Front 116

potts fracture

Back 116

Fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation.

Front 117

colles

Back 117

Fracture of the distal end the lateral forearm bone (radius) in which the distal fragment is displaced posteriorly.

Front 118

Identify the steps of repair of a bone fracture

Back 118

1. Formation of fracture hematoma
2. fibrocartilaginous callus formation
3.bony callus formation
4.bone remodeling

Front 119

Formation of fracture hematoma

Back 119

Blood vessels crossing the fracture line are broken. As blood leaks from the torn ends of the vessels, it forms a mass of blood (usually clotted) around the site of the fracture. This clot, called a fracture hematoma (hē‐ma‐TŌ‐ma; hemat‐=blood; ‐oma=tumor), usually forms 6 to 8 hours after the injury. Because the circulation of blood stops at the site where the fracture hematoma forms, nearby bone cells die. Swelling and inflammation occur in response to dead bone cells, producing additional cellular debris. Phagocytes (neutrophils and macrophages) and osteoclasts begin to remove the dead or damaged tissue in and around the fracture hematoma. This stage may last up to several weeks

Front 120

fibrocartilginous callus formation

Back 120

Fibroblasts from the periosteum invade the fracture site and produce collagen fibers. In addition, cells from the periosteum develop into chondroblasts and begin to produce fibrocartilage in this region. These events lead to the development of a fibrocartilaginous (soft) callus (fi‐brō‐kar‐ti‐LAJ‐i‐nus), a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone. Formation of the fibrocartilaginous callus takes about three weeks.

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bony callus formation

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In areas closer to well‐vascularized healthy bone tissue, osteogenic cells develop into osteoblasts, which begin to produce spongy bone trabeculae. The trabeculae join living and dead portions of the original bone fragments. In time, the fibrocartilage is converted to spongy bone, and the callus is then referred to as a bony (hard) callus. The bony callus lasts about three to four months.

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bone remodeling

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The final phase of fracture repair is bone remodeling of the callus. Dead portions of the original fragments of broken bone are gradually resorbed by osteoclasts. Compact bone replaces spongy bone around the periphery of the fracture. Sometimes, the repair process is so thorough that the fracture line is undetectable, even in a radiograph (x‐ray). However, a thickened area on the surface of the bone remains as evidence of a healed fracture.

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When placed under stress, bone tissue responds to the strain it experiences and becomes

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stronger through increased depostion of mineral salts and production of collagen fibers by osteoblasts.

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two principle effects of aging of bone tissue

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loss of bone mass and brittleness. Loss occurs of DEMINERALIZATION, the loss of calcium and other minerals from bone extracellular matrix.

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bone growth depends on what vitamins and mineral and hormones?

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Minerals:
Calcium and phosphorus
Magnesium
fluoride
manganese

Vitamins:
A, C, D, K, and B12

Hormones:
Human growth hormone (hGH)

Insulinlike growth factors (IGFs)

thyroid hormones
(throxine and triiodothyronine)

insulin

sex hormones
(estrogens and testostrone)

Parathyroid hormone (PTH)

calcitonin (CT)

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calcium and phosphorus

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Make bone extracellular matrix hard.

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magnesium

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Helps form bone extracellular matrix.

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fluoride

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Helps strengthen bone extracellular matrix.

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manganese

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Activates enzymes involved in synthesis of bone extracellular matrix.

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Vit A

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Needed for the activity of osteoblasts during remodeling of bone; deficiency stunts bone growth; toxic in high doses.

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Vit C

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Needed for synthesis of collagen, the main bone protein; deficiency leads to decreased collagen production, which slows down bone growth and delays repair of broken bones.

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Vit D

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Active form (calcitriol) is produced by the kidneys; helps build bone by increasing absorption of calcium from gastrointestinal tract into blood; deficiency causes faulty calcification and slows down bone growth; may reduce the risk of osteoporosis but is toxic if taken in high doses.

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Vit k and B12

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Needed for synthesis of bone proteins; deficiency leads to abnormal protein production in bone extracellularmatrix and decreased bone density.

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Human growth hormone (hGH)

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Secreted by the anterior lobe of the pituitary gland; promotes general growth of all body tissues, including bone, mainly by stimulating production of insulinlike growth factors.

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Insulinelike growth factors (IGFs)

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Secreted by the liver, bones, and other tissues upon stimulation by human growth hormone; promotes normalbone growth by stimulating osteoblasts and by increasing the synthesis of proteins needed to build new bone.

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thyroid hormones
thyroxine and triiodothyronine

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Secreted by thyroid gland; promote normal bone growth by stimulating osteoblasts.

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insulin

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Secreted by the pancreas; promotes normal bone growth by increasing the synthesis of bone proteins.

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sex hormons
estrogen and testosterone

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Secreted by the ovaries in women (estrogens) and by the testes in men (testosterone); stimulate osteoblasts and promote the sudden “growth spurt” that occurs during the teenage years; shut down growth at the epiphyseal plates around age 18–21, causing lengthwise growth of bone to end; contribute to bone remodeling during adulthood by slowing bone resorption by osteoclasts and promoting bone deposition by osteoblasts.

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parathyroid hormone (PTH)

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Secreted by the parathyroid glands; promotes bone resorption by osteoclasts; enhances recovery of calcium ions from urine; promotes formation of the active form of vitamin D (calcitriol).

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calcitonin (CT)

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Secreted by the thyroid gland; inhibits bone resorption by osteoclasts.

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age affect bone growth how

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As the level of sex hormones diminishes during middle age to older adulthood, especially in women after menopause, bone resorption by osteoclasts outpaces bone deposition by osteoblasts, which leads to a decrease in bone mass and an increased risk of osteoporosis.

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giantism

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Excessive or deficient secretion of hormones that normally control bone growth can cause a person to be abnormally tall or short. Oversecretion of hGH during childhood produces giantism

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pituitary dwarfism

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Undersecretion of hGH

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acromegaly

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Oversecretion of hGH during adulthood
Although hGH cannot produce further lengthening of the long bones because the epiphyseal plates are already closed, the bones of the hands, feet, and jaws thicken and other tissues enlarge. In addition, the eyelids, lips, tongue, and nose enlarge, and the skin thickens and develops furrows, especially on the forehead and soles.

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achondroplasia

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) is an inherited condition in which the conversion of cartilage to bone is abnormal. It results in the most common type of dwarfism, called achondroplastic dwarfism. These individuals are typically about four feet tall as adults. They have an average‐size trunk, short limbs, and a slightly enlarged head with a prominent forehead and flattened nose at the bridge. The condition is essentially untreatable, although some individuals opt for limb‐lengthening surgery

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osteoarthritis

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The degeneration of articular cartilage so that the bony ends touch; the resulting friction of bone against bone worsens the condition. Usually occurs in older individuals

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osteosarcoma

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Bone cancer that primarily affects osteoblasts and occurs most often in teenagers during their growth spurt; the most common sites are the metaphyses of the thighbone (femur), shinbone (tibia), and arm bone (humerus). Metastases occur most often in lungs; treatment consists of multidrug chemotherapy and removal of the malignant growth, or amputation of the limb.

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osteomyelitis

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An infection of bone characterized by high fever, sweating, chills, pain, and nausea; pus formation, edema, and warmth over the affected bone; and rigid overlying muscles. It is often caused by bacteria, usually Staphylococcus aureus. The bacteria may reach the bone from outside the body (through open fractures, penetrating wounds, or orthopedic surgical procedures); from other sites of infection in the body (abscessed teeth, burn infections, urinary tract infections, or upper respiratory infections) via the blood; and from adjacent soft tissue infections (as occurs in diabetes mellitus).

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osteopenia

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Reduced bone mass due to a decrease in the rate of bone synthesis to a level insufficient to compensate for normal bone resorption; any decrease in bone mass below normal. Osteoporosis is an example of severe osteopenia.

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osteoporosis

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literally a condition of porous bones

The basic problem is that bone resorption (breakdown) outpaces bone deposition (formation). In large part this is due to depletion of calcium from the body—more calcium is lost in urine, feces, and sweat than is absorbed from the diet

Osteoporosis primarily affects middle‐aged and elderly people, 80 percent of them women. Older women suffer from osteoporosis more often than men for two reasons: (1) Women's bones are less massive than men's bones, and (2) production of estrogens in women declines dramatically at menopause, while production of the main androgen, testosterone, in older men wanes gradually and only slightly. Estrogens and testosterone stimulate osteoblast activity and synthesis of bone matrix. Besides gender, risk factors for developing osteoporosis include a family history of the disease, European or Asian ancestry, thin or small body build, an inactive lifestyle, cigarette smoking, a diet low in calcium and vitamin D, more than two alcoholic drinks a day, and the use of certain medications.

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are two forms of the same disease that result from inadequate calcification of the extracellular bone matrix, usually caused by a vitamin D deficiency. Rickets is a disease of children in which the growing bones become “soft” or rubbery and are easily deformed. Because new bone formed at the epiphyseal (growth) plates fails to ossify, bowed legs and deformities of the skull, rib cage, and pelvis are common. Osteomalacia is the adult counterpart of rickets, sometimes called adult rickets. New bone formed during remodeling fails to calcify, and the person experiences varying degrees of pain and tenderness in bones, especially the hips and legs. Bone fractures also result from minor trauma. Prevention of and treatment for rickets and osteomalacia consists of the administration of adequate vitamin D and exposure to moderate amounts of sunlight.

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rickets and osteomalacia