Anatomy Chapter 5

Front 1

Functions of skeletal

Back 1

1. support
2. storage of minerals
3. blood cell production
4. protection
5. leverage

Front 2

Number of bones

Back 2

approx 206

Front 3

osteocyte

Back 3

-mature bone cell
-maintain and monitor the protein and mineral content of surrounding matrix
-each osteocyte directs the release of calcium from bone to blood and the deposition of calcium salts in the surrounding matrix
-occupy lacunae

Front 4

Osteoblast

Back 4

-not a mature bone cell
-secretes the collagen fiber and ground substance of the matrix
-if osteoblast becomes surrounded by matrix, it differentiates into an osteocyte

Front 5

Osteoprogenitor

Back 5

-least mature
-least differentiated
-differentiate from mesenchyme
-can divide to produce daughter cells that differentiate into osteoblasts
-->important in repair process

Front 6

Osteoclast

Back 6

-secrete acids from lysosomes that dissolve the bony matrix and release amino acids and the stored calcium and phosphate

Front 7

Haversian canal system

Back 7

osteon
-the basic histological unit of compact bone, consisting of osteocytes organized around a central canal and separated by concentric lamellae

Front 8

Lamellae

Back 8

concentric layers of bony matrix within an osteon

Front 9

Canaliculi

Back 9

microscopic passageways in bone matrix; permit the diffusion of nutrients and wastes to and from osteocytes

interconnect the lacunae of an osteon and form a branching network that reaches the central canal
--allows communication

Front 10

Haversian canal

Back 10

central canal
Longitudinal canal in the center of an osteon that contains blood vessels and nerves
-runs parallel to the surface of the bone
-contians 2 blood vessels

Front 11

Volksman's canals

Back 11

perforating canal
a passageway in compact bone that runs at right angles to the axes of osteons, between the periosteum and endosteum
-perpendicular to surface
-links one vertical blood vessel to the next

Front 12

Concentric lamellae

Back 12

Lamellae of each osteon are cylindrical and aligned parallel to the long axis of the bone. Collectively, concentric lamellae form a series of concentric rings, resembling a bulls-eye target, around the central canal

Front 13

How does the matrix composition vary in compact and spongy bones?

Back 13

The matrix composition in compact bone is the same as that of spongy bone, but they differ in the three dimensional arrangement of osteocytes, canaliculi, and lamellae

Front 14

What is the major structural difference between spongy and compact bone?>

Back 14

The major difference between compact bone and spongy bone is the arrangment of spongy bone into parallel struts or thick branching plates called trabeculae. Numerous interconnecting spaces are found between the trabeculae in spongy bone. Spongy bone possesses lamellae and, if the trabeculae are sufficiently thick, osteons will be present

Front 15

Where is spongy bone found?

Back 15

spongy bone is found wherever bones are not stressed heavily or where stresses arrive from many directions

Front 16

Where is compact bone found?

Back 16

Compact bone is thickest where stresses arrive from a limited range of directions. The shaft of compact bone normally conducts applied stresses from one epiphysis to another. The osteons are parallel to its long axis, and as a result, the shaft is very strong when stressed along that axis

Front 17

Differences between compact and spongy bone

Back 17

-a lot of open spaces between trabeculae in spongy bone
-osteons parallel to axis in compact bone--gives strength as forces come from either end of the bone
-end of bone=mostly spongy
-because struts are in all directions in spongy bone, allows bone strength when forces come from all directions

Front 18

Periosteum

Back 18

layer that surrounds a bone, consisting of an outer fibrous and inner cellular layer
--usually outer surface

Front 19

Endosteum

Back 19

An incomplete cellular lining found on the medullary surface of bones
-contains osteoprogenitor cells
-active during growth of bone and whenever repair or remodeling is under way

Front 20

Sesamoid bones

Back 20

bone that forms in a tendon

Front 21

Sutural bones

Back 21

irregular bones that form in fibrous tissue between the flat bones of the developing cranium

Front 22

What kind of bones does intramembranous ossification mostly make?

Back 22

makes most flat bones

Front 23

Kinds of bone development

Back 23

intramembranous ossification
endochondral ossification

Front 24

Intramembranous ossification

Back 24

-primitive mesenchymal cells appear at sites of future bones
-primitive mesenchymal cells become arranged around blood vessels
-mesenchymal cells differentiate into osteoblasts, which form spongy bone
-osteoblasts become osteocytes when they are completely surrounded by bony matrix
-inorganic materials are deposited in the matrix
-connective tissue on the surface of each developing structure forms a periosteum

Front 25

Step 1 of intramembranous ossification

Back 25

1. mesenchymal cells aggregate, differentiate into osteoblasts and begin the ossification process. The bone expands as a series of spicules that spread into surrounding tissues

Front 26

Step 2 of intramembranous ossification

Back 26

2. As the spicules interconnect, they trap blood vessels within the bone

Front 27

Step 3 of intramembranous ossification

Back 27

Over time, the bone assumes the structure of spongy bone. Areas of spongy bone may later be removed creating medullary cavities. Through remodeling, spongy bone formed this way can be converted to compact bone

Front 28

Endochondral ossification

Back 28

-masses of hyaline cartilage form models of future bones
-cartilage breaks down as differentiating osteoblasts from periosteum invade the disintegrating tissue
-osteoblasts form spongy bone in space previous occupied by cartilage

Front 29

What bones are made by endochondral ossification?

Back 29

Most bones are made by endochondral ossification

Front 30

Step 1 of endochondral ossification

Back 30

As the cartilage enlarges through appositional and interstitial growth, chondrocytes near the center of the shaft increase greatly in size. The matrix is reduced to a series of small struts that soon begin to calcify. The enlarged chondrocytes then die and disintegrate, leaving cavities within the cartilage

Front 31

Step 2 of endochondral ossification

Back 31

Blood vessels grow around the edges of the cartilage, and the cells of the perichondrium convert to osteoblasts. The shaft of the cartilage then becomes ensheathed in a supericial layer of bone

Front 32

Step 3 of endochonral ossification

Back 32

Blood vessels penetrate the cartilage and invade the central region. Fibroblasts migrating with the blood vessels differentiate into osteoblasts and being producing spongy bone at a primary ossification center. Bone formation then spreads along the shaft toward both ends

Front 33

Step 4 of endochondral ossification

Back 33

Remodeling occurs as growth continues, creating a marrow cavity. The bone of the shaft becomes thicker, and the cartilage near each epiphysis is replaced by shafts of bone. Further growth involves increases in both length and diameter

Front 34

Appositional growth

Back 34

growth in width of an endochondral bone

Front 35

Growth in length of an endochondral bone

Back 35

length adds at each end at the epiphyseal plate
-primary ossification center
-secondary ossification center
-ephiphyseal disc
-osteoclasts continue to make marrow cavity as bone grows

Front 36

Bone remodeling

Back 36

-entire skeleton is replaced every 5-7 years
-osteoclasts come in to small area of bone, dissolve minerals
-osteoblasts form bone to replace

Front 37

Hematopoiesis

Back 37

process of blood cell formation

Front 38

Red bone marrow

Back 38

where hematopoiesis occurs

Front 39

Yellow bone marrow

Back 39

fat

Front 40

Epiphysis

Back 40

the end of a long bone, spongy bone covered in cartilage

Front 41

Epiphyseal cartilage

Back 41

cartilaginous region between the epiphysis and diaphysis of a growing bone

Front 42

Diaphysis

Back 42

the shaft of a long bone, compact bone

Front 43

Articular cartilage

Back 43

cartilage pad that covers the surface of a bone inside a joint cavity

Front 44

Trabeculae

Back 44

one of the two types of osseous tissue that form bones. Compared to compact bone, which is the other type of osseous tissue, it has a higher surface area but is less dense, softer, weaker, and less stiff. It typically occurs at the ends of long bones, proximal to joints and within the interior of vertebrae. Cancellous bone is highly vascular and frequently contains red bone marrow where hematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of spongy bone is the trabecula.