First half of chapter 7

Question 1

Bones and their dynamics

Answer 1

Bones and teeth are the most durable remains of a once-living body .Living skeleton is made of dynamic tissues, full of cells, permeated with nerves and blood vessels. Continually remodels itself and interacts with other organ systems of the body. Osteology is the study of bone

Question 2

Skeletal system

Answer 2

Skeletal system—composed of bones, cartilages, and ligaments

Question 3

Cartilage

Answer 3

Cartilage—forerunner of most bones

Covers many joint surfaces of mature bone

Question 4

Ligaments

Answer 4

Ligaments—hold bones together at joints

Question 5

Tendons

Answer 5

Tendons—attach muscle to bone

Question 6

Functions of the Skeleton

: Support and protection

Answer 6

Support—limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera
Protection—of brain, spinal cord, heart, lungs, and more

Question 7

Functions of the Skeleton:Movement and electrolyle balance.

Answer 7

Movement—limb movements, breathing, and other movements depend on bone
Electrolyte balance—calcium and phosphate levels

Question 8

Functions of skeleton: Acid–base balance,Blood formation

Answer 8

Acid–base balance—buffers blood against large pH changes by altering phosphate and carbonate salt levels
Blood formation—red bone marrow is the chief producer of blood cells

Question 9

Bones and Osseous Tissue:Bone (osseous tissue)

Answer 9

Bone (osseous tissue)—connective tissue with the matrix hardened by calcium phosphate and other minerals

Question 10

Bones and Osseous Tissue:Mineralization or calcification

Answer 10

Mineralization or calcification—the hardening process of bone

Question 11

Bones and Osseous Tissue:Individual bones (organs)

Answer 11

Individual bones (organs) consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue

Question 12

General Features of Bones: flat and long bones

Answer 12

Flat bones
Thin, curved plates 
Protect soft organs 
Long bones
Longer than wide
Rigid levers acted upon by muscles; crucial for movement

Question 13

General Features of Bones: short and irregular bones

Answer 13

Short bones
Approximately equal in length and width
Glide across one another in multiple directions
Irregular bones
Elaborate shapes that do not fit into other categories

Question 14

General Features of Bones:Compact bone

Answer 14

Compact bone—dense outer shell of bone.

Skeleton three-fourths compact and one-fourth spongy bone by weight.

Question 15

General Features of Bones:Spongy (cancellous) bone

Answer 15

Spongy (cancellous) bone—loosely organized bone tissue
Found in center of ends and center of shafts of long bones and in middle of nearly all others
Covered by more durable compact bone

Question 16

Long bone features:

Diaphysis,Epiphyses and Medullary cavity (marrow cavity)

Answer 16

Diaphysis—shaft that provides leverage
Medullary cavity (marrow cavity)—space in the diaphysis of a long bone that contains bone marrow
Epiphyses—enlarged ends of a long bone
Strengthen joint and anchor ligaments and tendons

Question 17

Articular cartilage

Answer 17

Articular cartilage—layer of hyaline cartilage that covers joint surface; allows joint to move more freely

Question 18

Nutrient foramina

Answer 18

Nutrient foramina—minute holes in bone surface that allows blood vessels to penetrate

Question 19

Periosteum

Answer 19

Periosteum—external sheath covering most of bone

Question 20

Outer fibrous layer of collagen

Answer 20

Outer fibrous layer of collagen

Some fibers continuous with tendons.Perforating fibers—penetrate into bone matrix

Question 21

Inner osteogenic layer

Answer 21

Inner osteogenic layer of bone-forming cells

Important to bone growth and healing of fractures

Question 22

Endosteum

Answer 22

Endosteum—thin layer of reticular connective tissue lining marrow cavity
Has cells that dissolve osseous tissue and others that deposit it

Question 23

Epiphyseal plate (growth plate)—

Answer 23

Epiphyseal plate (growth plate)—area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones
Enables growth in length
Epiphyseal line—in adults, a bony scar that marks where growth plate used to be.

Question 24

Flat bone

Answer 24

Flat bone
Sandwich-like construction
Two layers of compact bone enclosing a middle layer of spongy bone
Both surfaces covered with periosteum
Diploe—spongy middle layer 
Absorbs shock
Marrow spaces lined with endosteum

Question 25

Bone Cells

Answer 25

Bone is connective tissue that consists of cells, fibers, and ground substance

Four principal types of bone cells
Osteogenic cells; osteoblasts; osteocytes; osteoclasts

Question 26

Bone Cells: Osteogenic cells

Answer 26

Osteogenic cells—stem cells found in endosteum and inner layer of periosteum
Arise from embryonic mesenchymal cells
Multiply continuously and give rise to most other bone cell types

Question 27

Bone Cells: Osteoblasts

Answer 27

Osteoblasts—bone-forming cells
Form single layer of cells under endosteum and periosteum
Nonmitotic
Synthesize soft organic matter of matrix which then hardens by mineral deposition
Stress stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforce bone
Secrete hormone osteocalcin
Stimulates insulin secretion of pancreas
Increases insulin sensitivity in adipocytes which limits the growth of adipose tissue

Question 28

Bone Cells: Osteocytes

Answer 28

Osteocytes: Osteocytes—former osteoblasts that have become trapped in the matrix they deposited.Cytoplasmic processes of osteocytes reach into canaliculi and contact processes of neighboring cells
Gap junctions allow for passage of nutrients, wastes, signals
Some osteocytes reabsorb bone matrix while others deposit it
Act as strain sensors—when stressed, produce biochemical signals that regulate bone remodeling (shape and density changes that are adaptive)

Question 29

Bone cells:Lacunae

Answer 29

Lacunae—tiny cavities where osteocytes reside

Question 30

Bone cells: Canaliculi

Answer 30

Canaliculi—little channels that connect lacunae

Question 31

Bone Cells, Osteoclasts

Answer 31

Osteoclasts—bone-dissolving cells found on bone surface
Osteoclasts develop from same bone marrow stem cells that give rise to blood cells (different origin from other bone cells)
Very large cells formed from fusion of several stem cells
Have multiple nuclei in each cell

Question 32

Bone Cells, Ruffled border

Answer 32

Ruffled border (large surface area) faces bone

Question 33

resorption bays

Answer 33

Cells often reside in resorption bays (pits in bone surface)

Dissolving bone is part of bone remodeling

Question 34

The Matrix:

Matrix of osseous tissue

Answer 34

Matrix of osseous tissue is, by dry weight, about one-third organic and two-thirds inorganic matter

Question 35

The Matrix:Organic matter

Answer 35

Organic matter—synthesized by osteoblasts

Collagen, carbohydrate–protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins

Question 36

The Matrix:Inorganic matter

Answer 36

Inorganic matter
85% hydroxyapatite (crystallized calcium phosphate salt)
10% calcium carbonate
Other minerals (fluoride, sodium, potassium, magnesium)

Question 37

The Matrix:composite material

Answer 37

Bone is a composite material—a combination of a ceramic and a polymer

Question 38

The Matrix,composite material: Hydroxyapatite

Answer 38

Hydroxyapatite and other minerals are the ceramic and collagen (protein) is the polymer

Question 39

The Matrix,composite material: Ceramic portion

Answer 39

Ceramic portion allows the bone to support body weight without sagging
Rickets is a disease caused by mineral deficiency and resulting in soft, deformed bones

Question 40

The Matrix,composite material: Polymer (protein)

Answer 40

Polymer (protein) gives some flexibility
Osteogenesis imperfecta (brittle bone disease) results from a defect in collagen deposition