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Chapter 6: Osseous Tissue and Bone Structure

front 1

The Skeletal System

back 1

• Skeletal system includes:
– bones of the skeleton
– cartilages, ligaments, and connective tissues

front 2

Functions of the Skeletal System

back 2

1. Support
2. Storage of minerals (calcium)
3. Storage of lipids (yellow marrow)
4. Blood cell production (red marrow)
5. Protection
6. Leverage (force of motion)

front 3

Classification of Bones

back 3

• Bone are identified by:
– shape
– internal tissues
– bone markings

front 4

Bone Shapes

back 4

1. Long bones
2. Flat bones
3. Sutural bones
4. Irregular bones
5. Short bones
6. Sesamoid bones

front 5

Long Bones

(Bone Shapes)

back 5

• Are long and thin
• Are found in arms, legs, hands, feet, fingers, and toes

• Diaphysis:
– the shaft
- A heavy wall of compact bone, or dense bone
- A central space called marrow cavity

• Epiphysis:
– wide part at each end
– articulation with other bones
• Mostly spongy (cancellous)bone
• Covered with compact bone (cortex)

• Metaphysis:
– where diaphysis and epiphysis meet

front 6

Flat Bones

(Bone Shapes)

back 6

• Are thin with parallel surfaces
• Are found in the skull, sternum, ribs,and scapula

• Resembles a sandwich of spongy bone
• Between 2 layers of compact bone

front 7

Sutural Bones

(Bone Shapes)

back 7

• Are small,irregular bones
• Are found between the flat bones of the skull

front 8

Irregular Bones

(Bone Shapes)

back 8

• Have complex shapes
• Examples:
– spinal vertebrae
– pelvic bones

front 9

Short Bones

(Bone Shapes)

back 9

• Are small and thick
• Examples:
– ankle
– wrist bones

front 10

Sesamoid Bones

(Bone Shapes)

back 10

• Are small and flat
• Develop inside
tendons near joints of knees, hands, and feet

front 11

Bone Markings

back 11

• Depressions or grooves:
‐ along bone surface
– Projections:
– where tendons and ligaments attach
– at articulations with other bones

• Tunnels:
– where blood and nerves enter bone

front 12

Bone Markings

back 12

front 13

Bone (Osseous) Tissue

back 13

• Dense, supportive connective tissue
• Contains specialized cells
• Produces solid matrix of calcium salt deposits
• Around collagen fibers

front 14

Characteristics of Bone Tissue

back 14

• Dense matrix, containing:
– deposits of calcium salts
– bone cells within lacunae organized around blood vessels

• Canaliculi:
– form pathways for blood vessels
– exchange nutrients and wastes

• Periosteum:
– covers outer surfaces of bones
– consist of outer fibrous and inner cellular layers

front 15

Matrix Minerals

back 15

• 2/3 of bone matrix is calcium phosphate, Ca3(PO4)2:
– reacts with calcium hydroxide, Ca(OH)2 to form – crystals of hydroxyapatite, Ca10(PO4)6(OH)2
– which incorporates other calcium salts and ions

front 16

Matrix Proteins

back 16

• 1/3 of bone matrix is protein fibers (collagen)

front 17

Bone Cells

back 17

• Make up only 2% of bone mass:

- Osteocytes
- Osteoblasts
– osteoprogenitor cells
– osteoclasts

front 18

Osteocytes

(Bone Cells)

back 18

• Mature bone cells that maintain the bone matrix
• Live in lacunae
• Are between layers (lamellae) of matrix
• Connect by cytoplasmic extensions through canaliculi in lamellae
• Do not divide

Functions
• To maintain protein and mineral content of
matrix
• To help repair damaged bone

front 19

Osteoblasts

(Bone Cells)

back 19

• Immature bone cells that secrete matrix compounds
(osteogenesis)

front 20

Osteoid

back 20

• Matrix produced by osteoblasts, but not yet
calcified to form bone
• Osteoblasts surrounded by bone become
osteocytes

front 21

Osteoprogenitor Cells

(Bone Cells)

back 21

• Mesenchymal stem cells that divide to produce
osteoblasts
• Are located in inner,cellular layer of periosteum
(endosteum)
• Assist in fracture repair

front 22

Osteoclasts

(Bone Cells)

back 22

• Secrete acids and proteindigesting enzymes
• Giant, mutlinucleate cells
• Dissolve bone matrix and release stored minerals
(osteolysis)
• Are derived from stem cells that produce macrophages

front 23

Homeostasis

back 23

• Bone building (by osteocytes) and bone recycling (by osteoclasts) must balance:
– more breakdown than building, bones become weak
– exercise causes osteocytes to build bone

front 24

Compact Bone

back 24

front 25

Osteon

back 25

• The basic unit of mature compact bone
• Osteocytes are arranged in concentric lamellae
• Around a central canal containing blood vessels

front 26

Perforating Canals

back 26

• Perpendicular to the central canal
• Carry blood vessels into bone and marrow

front 27

Circumferential Lamellae

back 27

• Lamellae wrapped around the long bone
• Binds osteons together

front 28

Spongy Bone

back 28

• Does not have osteons
• The matrix forms an open network of trabeculae
• Trabeculae have no blood vessels

front 29

Red Marrow

back 29

• The space between trabeculae is filled with red bone marrow:
– which has blood vessels
– forms red blood cells
– and supplies nutrients to osteocytes

front 30

Yellow Marrow

back 30

• In some bones, spongy bone holds yellow bone marrow:
– is yellow because it stores fat

front 31

Weight–Bearing Bones

back 31

• The femur transfers weight from hip joint to knee joint:
– causing tension on the lateral side of the shaft
– and compression on the medial side

front 32

Periosteum and Endosteum

back 32

• Compact bone is covered with membrane:
– periosteum on the outside
– endosteum on the inside

front 33

Periosteum

back 33

• Covers all bones:
– except parts enclosed in joint capsules

• It is made up of:
– an outer, fibrous layer
– and an inner,cellular layer

Functions of Periosteum
1. Isolate bone from surrounding tissues
2. Provide a route for circulatory and nervous
supply
3. Participate in bone growth and repair

front 34

Perforating Fibers

back 34

• Collagen fibers of the periosteum:
– connect with collagen fibers in bone
– and with fibers of joint capsules,attached tendons,and ligaments

front 35

Endosteum

back 35

• An incomplete cellular layer:
– lines the marrow cavity
– covers trabeculae of spongy bone
– lines central canals

• Contains osteoblasts,osteoprogenitor cells, and osteoclasts

• Is active in bone growth and repair

front 36

Bone Development

back 36

• Human bones grow until about age 25

• Osteogenesis:
– bone formation

• Ossification:
– the process of replacing other tissues
with bone

front 37

Calcification

back 37

• The process of depositing calcium salts
• Occurs during bone ossification and in other
tissues

front 38

Ossification

back 38

• The 2 main forms of ossification are:
– intramembranous ossification
– endochondral ossification

front 39

Intramembranous Ossification

back 39

• Also called dermal ossification:
– because it occurs in the dermis
– produces dermal bones such as mandible and
clavicle

• There are 3 main steps in intramembranous
ossification

front 40

Intramembranous Ossification: Step 1

back 40

• Mesenchymal cells aggregate:
– differentiate into osteoblasts
– begin ossification at the ossification center
– develop projections called spicules

front 41

Intramembranous Ossification: Step 2

back 41

• Blood vessels grow
into the area:
– to supply the osteoblasts

• Spicules connect:
– trapping blood vessels inside bone

front 42

IntramembranousOssification: Step 3

back 42

• Spongy bonedevelops and is remodeled into:
– osteons of compact bone
– periosteum
– or marrow cavities

front 43

Endochondral Ossification

back 43

• Ossifies bones that originate as hyaline
cartilage

• Most bones originate as hyaline cartilage

• Growth and ossification of long bones occurs in 6 steps

• Appositional growth:
– compact bone thickens and strengthens long bone with layers of circumferential lamellae

front 44

Endochondral Ossification: Step 1

back 44

• Chondrocytes in the center of hyaline cartilage:
– enlarge
– form struts and calcify
– die, leaving cavities in cartilage

front 45

Endochondral Ossification: Step 2

back 45

• Blood vessels grow around the edges of the cartilage

• Cells in the perichondrium change to osteoblasts:
– producing a layer of superficial bone around the shaft which will continue to
grow and become compact bone (appositional growth)

front 46

Endochondral Ossification: Step 3

back 46

• Blood vessels enter the cartilage:
– bringing fibroblasts that become osteoblasts
– spongy bone develops at the primary ossification center

front 47

Endochondral Ossification:

back 47

Step 4
• Remodeling creates a marrow cavity:
– bone replaces cartilage at the metaphyses

front 48

Endochondral Ossification: Step 5

back 48

• Capillaries and osteoblasts
enter the epiphyses:
– creating secondary ossification centers

front 49

Endochondral Ossification: Step 6

back 49

• Epiphyses fill with spongy bone:
– cartilage within the joint cavity is articulation cartilage
– cartilage at the metaphysis is epiphyseal
cartilage

front 50

Endochondral Ossification: Step 7

back 50

• As long as the epiphyseal cartilage continues to grow at its epiphyseal surface, the bone will continue to increase in length.

front 51

Bone Growth in Length

back 51

• Epiphyseal plate or cartilage growth plate
- cartilage cells are produced by mitosis on epiphyseal side of plate
- cartilage cells are destroyed and replaced by bone on diaphyseal side of plate

• Between ages 18 to 25, epiphyseal plates close.
- cartilage cells stop dividing and bone replaces the cartilage (epiphyseal line)

• Growth in length stops at age 25

front 52

Zones of Growth in Epiphyseal Plate

back 52

• Zone of resting cartilage
- anchors growth plate to bone

• Zone of proliferating cartilage
- rapid cell division (stacked coins)

• Zone of hypertrophic cartilage
- cells enlarged & remain in columns

• Zone of calcified cartilage
- thin zone, cells mostly dead since matrix calcified
- osteoclasts removing matrix
- osteoblasts & capillaries move in to create bone over calcified cartilage

front 53

Bone Growth in Width

back 53

• Only by appositional growth at the bone’s surface

• Periosteal cells differentiate into osteoblasts and form bony ridges and then a tunnel around periosteal blood vessel.

• Concentric lamellae fill in the tunnel to form an osteon.

front 54

Epiphyseal Lines

back 54

• When long bone stops growing, after puberty:
– epiphyseal cartilage disappears
– is visible on X‐rays as an epiphyseal line

front 55

Mature Bones

back 55

• As long bone matures:
– osteoclasts enlarge marrow cavity
– osteons form around blood vessels in compact
bone

front 56

Blood Supply of Mature Bones

back 56

• 3 major sets of blood vessels develop

1) Nutrient artery and vein:
– a single pair of large blood vessels
– enter the diaphysis through the nutrient foramen
– femur has more than 1 pair

2) Metaphyseal vessels:
– supply the epiphyseal cartilage
– where bone growth occurs

3) Periosteal vessels provide:
– blood to superficial osteons
– secondary ossification centers

front 57

Lymph and Nerves

back 57

• The periosteum also contains:
– networks of lymphatic vessels
– sensory nerves

front 58

Remodeling

back 58

• The adult skeleton:
– maintains itself
– replaces mineral reserves

• Remodeling:
– recycles and renews bone matrix
– involves osteocytes, osteoblasts, and osteoclasts

• Bone continually remodels, recycles, and replaces
• Turnover rate varies
• If deposition is greater than removal, bones get stronger
• If removal is faster than replacement, bones get weaker

front 59

Effects of Exercise on Bone

back 59

• Mineral recycling allows bones to adapt to stress
• Heavily stressed bones become thicker and stronger

front 60

Bone Degeneration

back 60

• Bone degenerates quickly
• Up to 1/3 of bone mass can be lost in a few weeks of inactivity

• What you don’t use, you lose
• Stresses applied to bones during physical activity are essential to maintain bone strength and mass

front 61

Effects of Hormones and Nutrition on Bone

back 61

• Normal bone growth and maintenance
requires nutritional and hormonal factors

front 62

Minerals

Effects of Hormones and Nutrition on Bone

back 62

• A dietary source of calcium and phosphate salts:
– plus small amounts of magnesium, fluoride, iron,
and manganese

front 63

Vitamins

Effects of Hormones and Nutrition on Bone

back 63

• Vitamin C is required for collagen synthesis,
and stimulates osteoblast differentiation

• Vitamin A stimulates osteoblast activity

• Vitamins K and B12 help synthesize bone proteins

front 64

Calcitriol

Effects of Hormones and Nutrition on Bone

back 64

• The hormone calcitriol:
– is made in the kidneys
– helps absorb calcium and phosphorus from digestive tract
– synthesis requires vitamin D3 (cholecalciferol)

front 65

Other Hormones

Effects of Hormones and Nutrition on Bone

back 65

• Growth hormone and thyroxine stimulate
bone growth
• Estrogens and androgens stimulate osteoblasts
• Calcitonin and parathyroid hormone regulate
calcium and phosphate levels

front 66

Hormones for Bone Growth and Maintenance

back 66

front 67

The Skeleton as Calcium Reserve

back 67

• Bones store calcium and other minerals
• Calcium is the most abundant mineral in the
body

front 68

Chemical Composition of Bone

back 68

front 69

Functions of Calcium

back 69

• Calcium ions are vital to:
– membranes
– neurons
– muscle cells, especially heart cells

front 70

Calcium Regulation

back 70

• Calcium ions in body fluids:
– must be closely regulated

• Homeostasis is maintained:
– by calcitonin and parathyroid hormone
– which control storage, absorption, and excretion

KEY CONCEPTS
• Calcium and phosphate ions in blood are lost in urine
• Ions must be replaced to maintain homeostasis
• If not obtained from diet, ions are removed
from the skeleton, weakening bones
• Exercise and nutrition keep bones strong

front 71

Calcitonin and Parathyroid Hormone Control

back 71

• Bones:
– where calcium is stored

• Digestive tract:
– where calcium is absorbed

• Kidneys:
– where calcium is excreted

front 72

Parathyroid Hormone (PTH)

back 72

• Low calcium ion levels in the blood cause the parathyroid glands in neck to secrete Parathyroid Hormone (PTH)

• Increases calcium ion levels by:
– stimulating osteoclasts to release stored calcium ions from the bone
– increasing intestinal absorption of calcium
- kidneys retain calcium ions

– decreases calcium loss in urine
- calcium is absorbed quickly in intestines

front 73

Calcitonin

back 73

• High calcium ion levels in blood cause Calcitonin to be secreted by C cells (parafollicular cells) in thyroid

• Decreases blood calcium ion levels by:
– inhibiting osteoclast activity
- rate of intestinal absorption decreases
- Kidneys allow calcium loss

– increasing calcium excretion at kidneys and increased calcium loss in urine
- Calcium is absorbed slowly in intestines
- Calcium is stored in bone matrix

front 74

Fractures

back 74

• Fractures:
– cracks or breaks in bones
– caused by physical stress

• Fractures are repaired in 4 steps

front 75

Fracture Repair: Step 1

back 75

• Bleeding:
– produces a clot (fracture hematoma)
– establishes a fibrous network

• Bone cells in the area die

front 76

Fracture Repair: Step 2

back 76

• Cells of the endosteum and periosteum:
– Divide and migrate into fracture zone

• Calluses stabilize the break:
– external callus of cartilage and bone surrounds break
– internal callus develops in marrow cavity

front 77

Fracture Repair: Step 3

back 77

• Osteoblasts:
– replace central cartilage of external callus
– with spongy bone

front 78

Fracture Repair: Step 4

back 78

• Osteoblasts and osteocytes remodel the fracture for up to a year:
– reducing bone calluses

front 79

Pott’s fracture

The Major Types of Fractures

back 79

- occurs at the ankle and affects both bones of the leg

front 80

Comminuted fractures

The Major Types of Fractures

back 80

- shatter the affected area into a multitude of bony fragments.

front 81

Transverse fractures

The Major Types of Fractures

back 81

- break a bone shaft across its long axis

front 82

Spiral fractures

The Major Types of Fractures

back 82

- twisting stresses that spread along the length of the bone

front 83

Displaced fractures

The Major Types of Fractures

back 83

- produce new and abnormal bone arrangements, non-displaced fractures retain the normal alignment of the bones or fragments

front 84

Colles’ fracture

The Major Types of Fractures

back 84

- break in the distal portion of the radius (usually from reaching to cushion a fall)

front 85

Greenstick fracture

The Major Types of Fractures

back 85

- one side of the shaft is broken, and the other side is bent.

front 86

Epiphyseal fractures

The Major Types of Fractures

back 86

- where bone matrix is undergoing calcification and chondrocytes are dying. A clean transverse fracture along this line can generally heal well. Unless carefully treated, fractures between the epiphysis and the epiphyseal cartilage can permanently stop growth at this site.

front 87

Compression fractures

The Major Types of Fractures

back 87

- occur in the vertebrae subjected to extreme streses

front 88

Age and Bones

back 88

• Bones become thinner and weaker with age
• Osteopenia begins between ages 30 and 40
• Women lose 8% of bone mass per decade, men 3%

front 89

Effects of Bone Loss

back 89

• The epiphyses, vertebrae, and jaws are most
affected:
– resulting in fragile limbs
– reduction in height
– tooth loss

front 90

Osteoporosis

back 90

• Severe bone loss
• Affects normal function
• Over age 45, occurs in:
– 29% of women
– 18% of men

front 91

Hormones and Bone Loss

back 91

• Estrogens and androgens help maintain bone mass
• Bone loss in women accelerates after menopause

front 92

Cancer and Bone Loss

back 92

• Cancerous tissues release osteoclastactivating
factor:
– that stimulates osteoclasts
– and produces severe osteoporosis

front 93

Name the five primary functions of the skeletal system. p170

back 93

The 5 primary functions of the skeletal system are: - support,
- storage of minerals and lipids,
- blood cell production,
- protection,
- and leverage.

front 94

Identify the six broad categories for classifying a bone according to shape. p173

back 94

The 6 broad categories for classifying bones according to shape are:
- flat
- irregular
- long
- sesamoid
- short
- sutrural

front 95

Define bone marking. p173

back 95

A bone marking, (surface feature) is an area on the surface of a bone structured for a specific function, such as:
- joint formation,
- muscle attachment,
- or the passage of nerves and blood vessels.

front 96

Mature bones cells are known as _____, bone-building cells are called __________, and ______ are bone-resorbing cells. p175

back 96

Mature bones cells are known as OSTEOCYTES, bone-building cells are called OSTEOBLASTS, and OSTEOCLASTS are bone-resorbing cells.

front 97

How would the compressive strength of a bone be affected if the ration of collagen to hydroxyapatite increased? p175

back 97

IF the ration of collagen to hydroxyapatite in a bone increased, the bone would become less strong (as well as more flexible.)

front 98

If the activity of osteoclasts exceeds the activity of osteoblasts in a bone, how will the mass of the bone be affected? p175

back 98

because osteoclasts break down or demineralize bone, the bone would have a reduced mineral content (less mass), as a result, it would be weaker.

front 99

Compare the structures and functions of compact bone and spongy bone. p179

back 99

Compact bone consists of osteons (Haversian systems) with little space between them. Compact bone lies over spongy bone and makes up most of the diaphysis. It functions to protect, support, and resist stress. Spongy bone consists of trabeculae with numerous red marrow-filled spaces. Spongy bone makes up most of the structure of short, flat, and irregular bones and is also found at the epiphyses of long bones. Spongy bone functions in storing marrow and providing some support.

front 100

A sample of bone has lamellae, which are not arranged in osteons, Is the sample most likely taken from the epiphysis or diaphysis? p179

back 100

The presence of lamellae that are not arranged in osteons is indicative of spongy bone, which is located in an epiphysis.

front 101

During intramembraneous ossification, which type of tissue is replaced by bone? p183

back 101

During intramembranous ossification, fibrous connective tissue is replaced by bone.

front 102

In endochondral ossification, what is the original source of osteoblasts? p183

back 102

In endochondral ossification, cells of the inner layer of the pericondrium differentiate into osteoblasts, and a cartilage model is gradually replaced by bone.

front 103

How could x-rays of the femur be used to determine whether a person has reached full height? p183

back 103

Long bones of the body, such as the femur, have an epiphyseal cartilage, a plate of cartilage that separates the epiphysis from the diaphysis so long as the bone is still growing lengthwise. An x-ray would indicate whether the epiphyseal cartilage is still present. If it is, growth is still occurring; if it is not, the bone has reached its adult length.

front 104

Describe bone remodeling. p184

back 104

Bone remodeling refers to the process whereby old bone is continuously being destroyed by osteoclasts while new bone is being constructed by osteoblasts.

front 105

Explain how heavy-metal ions could be incorporated into bone matrix. p184

back 105

The biochemistry of some heavy-metal ions, such as strontium, cobalt, uranium, and plutonium, is very similar to that of calcium. Osteoblasts cannot differentiate these abnormal heavy-metal ions from normal calcium ions, so the heavy metal ions become incorporated into the bone matrix. Over time, these dangerous ions can be released into circulation during normal bone remodeling.

front 106

Why would you expect the arm bones of a weight lifter to be thicker and heavier than those of a jogger? p186

back 106

The larger arm muscles of the weight lifter would apply more mechanical stress to the bones of the upper limbs. in response to that stress, the bones would grow thicker.

front 107

A child who enters puberty several years later than the average age is generally taller than average as an adult, Why? p186

back 107

Growth continues throughout childhood. At puberty, a growth spurt occurs and is followed by the closure of the epiphyseal cartilages. The later puberty begins, the taller the child will be when the growth spurt begins, so the taller the individual will be when growth is completed.

front 108

A 7yr old child has a pituitary gland tumor involving the cells that secrete growth hormone (GH), resulting in increased levels of GH. How will this condition affect the child's growth? p186

back 108

increased levels of growth hormone prior to puberty will result in excessive bone growth, making the individual taller.

front 109

Identify the hormones involved in stimulating and inhibiting the release of calcium ions from bone matrix. p188

back 109

Parathyroid hormone (PTH) influences osteoclast activity to cause a release of stored calcium ions from the bone. Under the influence of calcitonin, osteoclast activity is inhibited, while osteoblasts continue to lock calcium ions in the bone matrix. Therefore, PTH serves to increase blood calcium levels by causing its release from bone, and calcitonin decreases blood calcium levels by causing calcium to remain in bone.

front 110

Why does a child who has rickets have difficulty walking? p188

back 110

The bones of children who have rickets are poorly mineralized and as a resulte are quite flexible. under the weight of the bondy, the leg bones bend. The instability makes walking difficult and can lead to other problems of the legs and feet.

front 111

What effect would increased PTH secretion have on blood ion calcium levels? p188

back 111

Parathyroid hormone (PTH) stimulates osteoclasts to release calcium ions from bone and enhances calcitriol's effect on the intestinal absorption of calcium. Increase PTH secretion would result in an increase in the level of calcium ions in the blood.

front 112

How does calcitonin help lower the calcium ion concentration of blood? p188

back 112

Calcitonin lowers blood calcium levels by inhibiting osteoclast activity and increasing the rate of calcium excretion by the kidneys.

front 113

List the steps involved in fracture repair, beginning at the onset of the bone break. p192

back 113

Immediately following a fracture, extensive bleeding occurs at the site of injury. after several hours, a large blood clot called a fracture hematoma develops. Next, an internal callus forms as a network of spongy bone unties the inner edges, and an external callus of cartilage and bone stabilizes the outer edges. The cartilaginous external callus is eventually replaced by one, and the struts of spongy bone now unite the broken ends. With time, the swelling that initially marks the location of the fracture is remodeled, and little evidence that a break occurred remains.

front 114

At which point in fracture repair would you find an external callus? p192

back 114

An external callus forms early in the healing process, when cells from the endosteum and periosteum migrate to the area of the fracture. These cells form an enlarged collar (external Callus) that encircles the bone in the area of the fracture.

front 115

Define osteopenia. p193

back 115

Osteopenia is inadequate ossification and is common to the aging process. It results as a consequence of decreasing osteoblast activity accompanied with normal osteoclast activity.

front 116

Why is osteoporosis more common in older women that in older men? p193

back 116

In women, the sex hormones known as estrogens play an important role in moving calcium into bones. after menopause, the level of these hormones decreases dramatically; as a result, older women have difficulty replacing the calcium in bones that is being lost due to normal aging. In men, the level of sex hormones (androgens) does not decrease until much later in life.

front 117

Which of the following is NOT a function of the skeletal system?

protection
contraction
support
blood cell production

back 117

contraction

front 118

The femur and the humerus are examples of __________.

back 118

long bones

front 119

The carpals or wrist bones are examples of __________.

back 119

short bones

front 120

What is the term for the extended tubular shaft of a long bone?

back 120

diaphysis

front 121

Which of the following types of cells are the mature bone cells that maintain the bone matrix?

back 121

osteocytes

front 122

Which of the following statements about bone tissue is FALSE?

It is made primarily of cells.
It contains collagen.
It is made primarily of calcium phosphate.
It contains four different cell types.

back 122

It is made primarily of cells.

front 123

Which of the following types of bone cells is responsible for removing and recycling bone?

back 123

osteoclasts

Osteoclasts are responsible for removing and recycling bone.

front 124

Which of the following are NOT structural components of compact bone?

trabeculae
osteons
concentric lamellae
central canals

back 124

trabeculae

front 125

Which component of bone is responsible for blood cell formation?

back 125

Red bone marrow

Red bone marrow is responsible for blood cell formation.

front 126

What is the name of the membrane that covers the outer surface of the bones?

back 126

periosteum

front 127

Which of the following forms the flat bones of the skull?

back 127

intramembranous ossification

front 128

In which of the following does bone replace existing cartilage?

back 128

endochondral ossification

front 129

Which of the following allows a bone to increase in diameter or width?

back 129

appositional growth

Appositional growth allows a bone to increase in diameter.

front 130

What is the term for the process in which the organic and mineral components of bone are continuously recycled and renewed?

back 130

remodeling

front 131

Which of the following is an effect of stress on a bone?

back 131

The bone will become thicker.

Bones become thicker and stronger in response to stress.

front 132

Text: __________ is required for collagen synthesis, and a deficit results in a condition called scurvy.

back 132

Vitamin C

front 133

Which two hormones play opposing roles in regulating the calcium level in blood and body fluids?

back 133

calcitonin and parathyroid hormone

front 134

Which of the following is the term for a fracture in which the broken bone breaks through the skin?

back 134

open or compound

An open or compound fraction occurs when the broken bone projects through the skin.

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Which of the following is the last step of fracture repair?

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remodeling to return the bone to its normal shape

Remodeling is the last step of fracture repair.

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What is the term for a reduction in bone mass that is sufficiently large that it compromises the normal function of the bone?

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osteoporosis

Osteoporosis is a reduction in bone mass that is sufficiently large to compromise the normal function of bone. It results in weakening of the bones, making them likely to break.