Anatomy Chapter 6 Bones And Skeletal Tissue

Front 1

What is the cartilage most closely associated with bone development?

Back 1

The cartilage most closely associate with bone development is hyaline cartilage. They are the most abundant skeletal cartilages. The growth of bones in length involves the production of hyaline cartilage followed by bone replacement.

Front 2

What is the perichondrium? Describe its inner and outer layer.

Back 2

Skeletal cartilage is surrounded by a layer of double-layered connective tissue called perichondrium. The outer layer of perichondrium contains dens irregular connective tissue containing fibroblasts.
The inner layer is more delicate with fewer fibers. It contains chondroblasts. Lacuna are the open spaces that allow chondrobasts to mature into chondrocytes.

Front 3

Describe the blood vessels and osteochondral progenitor cells in the inner layer of perichondrium.

Back 3

Blood vessels extend through the outer layer but do not reach the inner layer, thus lowering oxygen levels.
Osteochondral progenitor cells, which are the stem cells of bone and cartilage), are located within the inner layer and differentiate into chondroblasts because of the low oxygen levels.

Front 4

What are the two kinds of cartilage growth?

Back 4

Appositional growth is when condroblasts lay down new matrix (ECM) and add new chondrocytes to the outside of the tissue.
Interstitial growth is when chondrocytes within the tissue divide and add more matrix between the cells.

Front 5

Bone is composed of organic and inorganic substances. Describe the organic substances. What are the two kinds of ossification?

Back 5

Organic substances give bone its flexibility while inorganic substances give bone its strength.
Cartilage and membranes are the most common organic substances.They serve as the structure to which the inorganic substances will be added in a process called ossification. There are two kinds of ossification:
Endochondral ossification gives rise to most bones of the body.
Intramembraneous ossification produces the flat bones of the skull and clavicle.

Front 6

What is the most common inorganic substance secreted by bone producing cells? What happens with the loss of organic and inorganic matrix?

Back 6

Calcium hydroxypatite is the most common inorganic substance secreted by the bone producing cells.
The loss of organic matrix of bone makes the bone brittle. The loss of inorganic matrix makes the bone flexible or rubbery.

Front 7

What are the four kinds of bone cells?

Back 7

Osteochondral progenator cells, osteoblasts, osteocytes, osteoclasts.

Front 8

Describe osteochondral progenator cells

Back 8

stem cells of bone and cartilage). Located in the inner layers of the periosteum and the endosteum. These layers have vascularity allowing for elevated oxygen levels. This stimulates the osteochondral progenator cells to develop into osteoblasts.

Front 9

Describe osteoblasts.

Back 9

Form bone matrix (ossification) around themselves and join to other osteoblasts to form the extracellular bony matrix.

Front 10

Describe osteocytes

Back 10

Mature osteoblasts become inactive except to maintain the bone matrix.

Front 11

Describe osteoclasts.

Back 11

Derived from the stem cells of red bone marrow. They secrete hydrogen ions to decalcify bone matrix for resorption during remodeling.

Front 12

Describe what compact bone is made of and where it is located. What is it also known as?

Back 12

Compact Bones is found in the external regions of all bones. It is composed of layers (lamellae) of concentric bone matrix. Known as lamellar bone because of its laminated appearance.

Front 13

Describe the outermost layers of compact bone as well as the internal layers.

Back 13

The outermost layers encircle the entire bone. They are called circumfential lamellae. Then resist the twisting of the bone.

Internally, an osteon is a group of lamella that form a cylinder. The cylinder shape gives the osteon its strength and is orientated in the direction of stress.

Front 14

Describe the Haversian system.

Back 14

The osteon along with blood vessels and nerves comprise the Haversian system.

The Haversian system provides the needed oxygen, nutrients, and communications necessary for proper functioning. Volksman's canals connect the blood and nerve supply of the periosteum to the central canas and endosteum.

Front 15

Describe spongy bone

Back 15

Spongy Bone is found internally in all bones. It allows for resistance to stress in multiple directions. No osteons are present, but plates of bone (trabeculae) are organized in random directions. Other names for spongy bone are woven bone or trabecular bone because of this arrangement.

Front 16

What happens in case of breakage?

Back 16

In case of breakage trabeculae arrange in the direction of force during repair. Osteoblasts and osteocytes receive oxygen and nurtrients by diffusion through the canaluculi in the trabeculae from capillaries located in the surrounding endosteum.

Front 17

Describe the process of fetal intramembranous ossification.

Back 17

Ossification begins centrally and proceeds marginally.
Mesenchymal cells group together and differentiate into osteoblasts secreting bone matrix (osteoid).
Trapped osteoblasts develop into osteocytes.
Bone matrix is laid down around blood vessels forming trabeculae.
Trapped blood vessels develop into red bone marrow.
Internal mesenchyme around the trabeculae develops into endosteum.
External mesenchyme develops into the periosteum.
As the trabeculae continue to develop, the most superficial are remodeled into lamellae forming compact bone.

Front 18

Describe endochondral ossification. When does it begin? Describe how trabeculae is formed.

Back 18

Except for the skull and clavicles, most bones are formed this way. Beginning in the second month of development, hyaline cartilage is ossified/classified. This limits nutrient availability thus causing the deterioration of the cartilage. When complete, cartilage remains only as articular and epiphyseal cartilage.

Ossification of the remaining cartilage forms the trabeculae of spongy bone. Osteoclasts break down the spongy one to form the medullary cavity and to allow the external surfaces to be remodeled into compact bone.

Front 19

Describe bone remodeling. WHere does it occur most frequently? WHy is it necessary?

Back 19

Bone remodeling:
involves the reabsorption and secretion of bone matrix by osteoclasts and osteoblasts respectively.
Osteoblasts secrete bone matrix and osteoclasts secrete HCl to reabsorb bone matrix.
occurs most frequently at the surfaces of the periosteum and endosteum.
necessary for bone growth while reducing bone weight.
allows long bones to retain their cylinder shape for strength.

Front 20

Describe appositional bone growth.

Back 20

Appositional growth (width) involves osteoblasts beneath the periosteum secreting bone matrix concentrically around periosteal blood vessels (osteon formation).
Trapped periosteum develops into endosteum.
The process continues increasing the bone’s width.

Front 21

Describe how bones grow in length

Back 21

Chondroblasts within the articular and epiphyseal cartilages produce new cartilage matrix.
Osteoblasts secrete new bone matrix onto the adjacent cartilage surfaces.
Epiphyseal cartilage growth must precede and be in relationship to bone growth in order to maintain the growth plate.
Ossification of the growth plate forms the growth or epiphyseal line and no additional bone growth in length can occur.

Front 22

Describe the four bone shapes

Back 22

Long bones are longer than they are wide.
Short bones are about as wide as they are long. Sesamoid bones are a special type of short bone formed in a tendom (patella).
Flat bones are relatively thin, usually curved.
Irregular bones do not fit into the above categories (vertebrae).

Front 23

What are the three components of long bone?

Back 23

Diaphysis, epiphysis, epiphysis plate.

Front 24

Describe diaphysis of long bone. Describe the epiphysis.

Back 24

1. Diaphysis (shaft): made of compact bone, may have medullary cavity that contains red marrow as a child and yellow marrow as an adult. 2. Epiphysis (end of bone): made of cancellous bone with red marrow

Front 25

Describe the epiphysis plate.

Back 25

Epiphysis plate (growth plate): hyaline cartilage between the epiphysis and diaphysis creates bone growth in length an ossifies when bone stops growing to form the epiphyseal line

Front 26

Describe flat bone structure

Back 26

Flat bons consist of spongy bone between two layers of compact bone.
No medullary cavity
Red marrow may be found around the trabeculae of the spongy bone, especially in the sternum.

Front 27

What are bone breaks/fractures classified by? What are the four steps of bone repair?

Back 27

Bone breaks or fractures are classified by their completeness and position of the two bone ends.
In repair, a hematoma will form due to rupture of localized blood vessels. Then, a fibrocartilaginous callus will be produced by fibroblasts forming connective tissue (mostly cartilage) between the two bone ends. Then, a bony callus will be produced by osteoblasts secreting new bone matrix upon the newly formed cartilage forming spongy bone. Finally, remodeling of the bone will form a new medullary cavity and external compact bone.

Front 28

How is evidence of healed fractures seen?

Back 28

Evidence of a healed fracture can be seen with the remnants of the bony collar and traveculae of the spongy bone will be orientated in teh direction of stress.