Week 2 - Cartilage

What is cartilage?

- A tough, flexible, resilient specialized type of CT

Cartilage forms from what?

- Embryonic mesenchyme

What is the function of cartilage?

- Structurally supports specific soft tissues such as those found in the respiratory tract and provides cushioned, low-friction surfaces in joints

Cartilage is composed of __________ ________ cells and abundant _____________ ___________.

- Relatively few

- Extracellular matrix

What are the 3 types of cartilage and their commonality?

1) Hyaline cartilage - most common form

2) Elastic cartilage - Less common

3) Fibrocartilage - Least common

Ground substance is composed of ______ families of macromolecules. What are they?

- 3: Glycosaminoglycans (GAGs), proteoglycans, glycoproteins

What are glycosaminoglycans (GAGs)/what is their function?

- Negatively charged molecules which attract sodium ions, drawing in extracellular fluid due to osmotic activity, resulting in hydration of the ground substance allowing resistance to compressive forces

What are proteoglycans/what is their function?

- They are molecules which have a protein core to which GAGs bind and function as large space occupying molecules which resists compression and cause the gel-state of the extracellular matrix.

What are glycoproteins/what is their function?

- Function in cell adhesion by facilitating attachment of cells to the extracellular matrix; help bind things together.

Explain the organization of the cartilage matrix: _______________ ____________ ___________ and __________________ are linked to ____________ ___________ ( _________________ and _______________ cartilage). ____________ _____________ molecules bind to collagen binds, resulting in a cross-linked matrix that is ________ ___________, ____________, and _____________.

- Collagen type II fibrils

- Proteoglycans

- Hyaluronic acid

- Hyaline

- Elastic

- Chondroitin sulfate

- Highly hydrated

- Pliable

- Strong

Is cartilage vascular? Why?

- No; Avascular

- Nourished by blood vessels in surrounding CT or by diffusion from synovial fluid that bathes articular cartilage

Is cartilage innervated? Are there lymphatic vessels in cartilage?

- No and no

What are chondrocytes? What do they do?

- Cells associated with cartilage which exhibit low metabolic activity and are located in spaces called lacunae

- They produce the extracellular matrix.

Cartilage is usually surrounded by a _______________ which is a sheath of _________ ___________ _____________ ____________ that is __________ and has ___________ and ____________ _______________.

- Perichondrium

- Dense irregular collagenous CT

- Vascularized

- Nerve

- Lymphatic vessels

What does the perichondrium provide?

- An interface between the cartilage and surrounding tissues

With what types of cartilage is the perichondrium associated?

- Associated with hyaline and elastic cartilage

- No associated with fibrocartilage or articular (hyaline) cartilage

What are the layers of the perichondrium? Describe them.

- Outer fibrous layer: Fibroblasts are present and collagen type 1

- Inner cellular layer: Consists of mostly chondrogenic cells that divide and some become chondroblasts which secrete cartilage matrix.

Chondroblasts are located deep to the fibrous layer of the perichondrium in the _____________ __________ _____________. They make ________________ ______________. This allows the cartilage to grow from the ___________ which is called _____________ growth.

- Inner cell layer

- Extracellular matrix

- Periphery

- Appositional

Appositional growth is fast or slow? Can it continue in adults?

- Slow

- Yes

Each chondroblast is in a ______________.

- Lacuna

As more matrix is deposited, the chondroblast becomes a _______________. The matrix around each lacuna is called ___________ __________. The matrix between the clusters and individual lacunae is called _______________ ____________.

- Chondrocyte

- Territorial matrix

- Interterritorial matrix

Does the territorial or interterritorial matrix form the bulk of the extracellular matrix.

- Interterritorial matrix

Describe the composition and subsequent staining of territorial matrix and interterritorial matrix.

- Territorial matrix has relatively few fibers but is rich in chondroitin sulfate (a GAG), which is very basophilic, so it tends to stain a dark blue. Proteoglycans and hyaluronic acid are also present.

- Interterritorial matrix has more fibers and fewer proteoglycans than territorial matrix; tends to stain less blue than territorial matrix. It also contains chondronectin, which helps bind the fibers, GAGs, and integrins

Which stains darker, territorial matrix or interterritorial matrix?

- Territorial matrix

What type of fibers does hyaline cartilage contain in its matrix?

- Type II collagen fibrils

How does fresh hyaline cartilage appear?

- Looks blue-gray and semitranslucent

Do the fibers appear in the matrix of hyaline cartilage?

- No; they have the same refractive index as the ground substance

Hyaline cartilage is _________ but not ____________.

- Pliable

- Compressible

Which is the most abundant type of cartilage in the body?

- Hyaline cartilage

Can chondrocytes undergo cell division?

- To some extent

Explain how chondrocytes can undergo cell division. What is this process called?

- They form clusters of 2 or 4 cells in a lacuna called isogenous clusters or isogenous groups. Each of these cells produces matrix and the cells become separated and each cell is in its own lacuna.

- Interstitial growth

When and where does interstitial growth occur?

- Occurs only in the early phase of hyaline cartilage formation

- Occurs in articular cartilage and in epiphyseal plates (growth plates) of long bones

Why does growth in the epiphyseal plate have to be interstitial and not appositional?

- The is no perichondrium from which appositional growth can occur

Does articular cartilage have a perichondrium? How does it get nutrition?

- No

- From synovial fluid

What type of cartilage is articular cartilage typically?

- Hyaline cartilage

In mammals, the cartilage model for the majority of the bones of the skeleton is found in the ________ _________ and is replaced for the most part by __________.

- Developing fetus

- Bone

Elastic cartilage looks similar to ____________ ____________ except it contains ___________ fibers in addition to the _____________ __________ __________ fibers.

- Hyaline cartilage

- Elastic fibers

- Type II collagen

Describe the appearance of fresh elastic cartilage.

- It appears yellow-ish due to the abundant elastic fibers

While elastic cartilage does have a ___________, _________ growth can still occur.

- Perichondrium

- Interstitial

The chondrocytes of elastic cartilage are still in _________ and tend to be ___________ than in hyaline cartilage.

- Lacunae

- Closer

What does fibrocartilage look similar to? How can one distinguish them?

- Dense CT

- Fibrocartilage has chondrocytes that are in lacunae

Where is fibrocartilage often found in association with?

- With hyaline cartilage and dense CT

How are the chondrocytes of fibrocartilage often seen?

- Lined up in short rows.

What are the fibers of fibrocartilage?

- Type I collagen

Does fibrocartilage have a perichondrium?

- No