Skeletal Tissue, Microanatomy NOT FINISHED

This makes up the ground substance of cartilage, aggregates of 100 or more molecules, accounts to the solid yet flexible consistency.

Proteoglycans

Cartilage has a very limited capacity to repair and regenerate because:

Poor blood supply, devloid of blood vessels

Exchange of metabolites between chondrocytes and surrounding tissue depends on diffusion through the:

water of the ground substance

These are rounded precursors, found in the perichondrium. Found from the differentiation of stellate-shaped primitive mesenchymal cells, cartilage formation begins.

Chondroblasts

These are mature cartilage cells that maintain the integrity of the cartilage matrix.

Chondrocytes

This is the layer surrounding the mature cartilage masses, composed to collagen fibers and spindle-shaped cells (resemble fibroblasts)

Perichondrium

Mitotic division of chondroblasts:

1. Start in ground substance, fibrous extracellular material synthesis

2. Secretion of extracellular material traps and separates chondroblasts, within the cartilaginous matrix.

3. Further mitotic division to form clusters of mature cells, separated by a small amount of extracellular material.

This growth of the cartilage is the transformation of the cells of the perichondrium into chondroblasts and form new cartilage.

Appositional growth

This growth of the cartilage is the further division of chondrocytes, trapped in the formed matrix and deposition of more matrix material. LIMITED IN MATURE CARTILAGE MASSES.

Interstitial growth

These are small vessels that enter the cartilage mass, where the cartilage is particularly thick, like costal cartilage.

Cartilage channels

This is the most common cartilage and type II collagen.

Hyaline cartilage

Where is hyaline cartilage commonly found?

Trachea

Nasal septum

Larynx

Sternal end of ribs

Hyaline cartilage of the articular surfaces of joints do not have this structure on the surfaces of joints.

Hyaline cartilage

Can hyaline cartilage repair itself?

No, it as no capacity to regenerate for new cartilage after damage

Characteristics of hyaline cartilage:

1. Not cross-branched

2. Arranged in an interlacing network of fine fibrils (no light microscopy)

3. Forms articular surfaces of synovial joints

4. Role in body skeleton

Where can fibrocartilage be found?

1. Intervertebral discs

2. Articular cartilages

3. Pubic symphysis

4. Dense collagenous tissue in joint capsules

5. Ligaments

6. Connections of some tendons to bone

Features of fibrocartilage:

Intermediate between hyaline cartilage and dense irregular connective tissue

This cartilage consists of alternating layers of hyaline cartilage matrix wth thick layers of dense collagen fibers. Orientated in the direction of functional stresses, an abundant of collagen.

Fibrocartilage

Chondrocytes in fibrocartilage appear:

arranged in rows, between the dense collagen layers, within lacunae in the glycoprotein matrix

Where is elastic cartilage found?

1. External ear

2. External auditory canal

3. Epiglottis

4. Some laryngeal cartilage

5. Walls of Eustachian tubes

Elastic cartilage is similar to hyaline, but the main difference is:

Abundant elastic fibers, that are stained BLACK

In a stained slide of elastic cartilage, the portion that is stained red is the:

collagen

Development and growth of elastic cartilage occurs in what growth pattern?

Interstitial and appositional growth

Bone is made out of what type of collagen?

Type 1

What are the three types of cells within bone?

1. Osteoblasts (osteoproginator cell, primitive mesenchymal stem cell)

2. Osteoclasts (macrophage-monocyte cell line, multiple phagocytic cells)

3. Osteocytes (osteoprogenitor cell)

Bone is mineralized by:

calcium hydroxyapatite deposition

What are the three components of bone?

1. Cortex (RIGID SHELL, COMPACT)

2. Medullary/cancellous zone (CENTRAL ZONE, THIN, INTERCONNECTING NARROW BONE)

3. Hematopoietic bone marrow (SPACE IN MEDULLARY BONE BETWEEN TRABECULAE)

Where are osteoblasts found?

Surface of trabeculae

What is the function of osteoblasts?

Synthesize new osteoid

Mediates its mineralization

What is the function of osteocytes?

Assist in nutrition of bone

Where are osteocytes found?

Largely inactive trapped within the bone matrix

When osteoblasts are active, what do they look like?

Large, broad, spindle-shaped or cuboidal cells with abundant basophilic cytoplasm

When osteoblasts are inactive, they appear how?

Narrow, attenuated, spindle-shaped lying on the bone surface and eventually will be undetectable

These bone cells are large, multi-nucleate cells. They are phagocytic and capable of eroding bone. It is in constant turnover and refreshing bone, along with osteoblasts. Involved in the reabsorption and remodeling of bone.

Osteoclasts

Osteoclasts participate in the long-term maintenance of blood calcium homeostasis by their response to these hormones:

PTH and calcitonin

Osteoclasts are often seen lying in depressions reabsorbed from the bone surface, called the:

Howship lacunae

Bone exists in two main forms:

Woven

Lamellar

Characteristics of woven bone:

Immature

Randomly oriented collagen fibers

In fetal bone development, produced when osteoblasts synthesize osteoid rapidly

Associated with healing/repair

Remodeled into lamellar

Characteristics of lamellar bone:

Mature

Collagen fibers are oriented in parallel arrays

Aligned to withstand stresses on the skeleton

Physically stronger and more resistant

virtually all bone in healthy adults

Two types of lamellar bone in the long bone:

Compact (cortical)

Cancellous (medullary) bone

Compact bone forms the:

dense wall of the shaft, or diaphysis

Cancellous bone occupies the:

large central medullary cavity (network of irregular plates called trabeculae)

Articular surfaces are the expanded ends of this part of the long bone.

Epiphyses of long bones

Articular joint surfaces are protected by:

articular cartilage, a form of hyaline

Long bones grow in length, prior to skeletal maturity. It occurs at a growth or epiphyseal plate, situated at the end of each bone at the junction of the diaphysis and epiphysis.

Endochondral ossification

This is dense fibrous tissue, surrounding the external surface of the bone. It is for the insertion site of muscles, tendons, and ligaments.

Periosteum

Periosteum’s main function:

Insertion site of muscles, tendons and ligaments

This surrounds the inner surfaces of the bone, including the trabeculae of cancellous bone.

Endosteum

this is the functional unit of the cortical bone. Concentric lamellae around central haversian canals, that have neurovascular bundles.

Osteon

This bone type is made up of parallel bone columns in the line of stress exerted on the bone.

Compact bone

Each column in the compact bone is made up of:

Lamellae

Two parts of the haversian systems:

Haversian canals and lamellae

this is the space in the matrix of compact bones, osteoblasts are trapped as osteocytes.

Lacuna

this is there neurovascular bundles interconnect with one another and the endosteum and periosteum, piercing the columns at the right angles (or obliquely) to the Haversian canals.

Volkmann canal

Periosteum contains what cells that are capable of converting into:

Osteoprogenitor cells and osteoblasts

Insignificant flattened cells with spindle-shaped nuclei, appears of what periosteum bone formation?

Inactive bone formation

Cells proliferate and increase in size to become osteoblasts, appears in what periosteum bone formation?

active bone formation

What are the two forms of bone development?

1. Endochondrial ossification

2. Intramembranous ossification

What are the zones of the epiphyseal growth plate?

Zone of reserve cartilage

Zone of proliferation

Zone of maturation

Zone of hypertrophy and calcification

zone of cartilage degeneration

Osteogenic zone