Histology Exam 2 study prep- Binghamton University

What is cartilage composed of?

Fibers, ground substance (matrix), and cells.

What type of collagen is characteristic of cartilage?

Type II collagen.

What is the function of a chondroblast?

Produces the fibers and ground substance (matrix) of cartilage.

What is a chondrocyte?

A mature cartilage cell surrounded by the matrix it secreted and located in a lacuna.

What is the perichondrium?

A dense fibrous connective tissue covering on the outer surface of cartilage.

What is appositional growth of cartilage?

Growth at the surface as new matrix is added onto existing matrix, increasing thickness.

What is interstitial growth of cartilage?

Growth from within cartilage as cells divide and produce new matrix.

What are the three types of cartilage?

Hyaline cartilage, fibrocartilage, and elastic cartilage.

Where is hyaline cartilage found?

Articular surfaces of long bones, trachea, nose, and bronchi.

What important developmental role does hyaline cartilage have?

It forms the cartilaginous precursor of long bones.

What is endochondral ossification?

The gradual replacement of a hyaline cartilage precursor with bone.

What is the ground substance of cartilage rich in?

Sulfated GAGs, proteoglycans, and water.

Which cartilage is the strongest of the three types?

Fibrocartilage.

Does fibrocartilage have a perichondrium?

No.

What forces does fibrocartilage resist?

Compression and stretching.

Where is fibrocartilage found?

Between vertebrae and at tendon-long bone junctions.

What types of collagen are associated with fibrocartilage?

Type I collagen from the dense CT component and type II collagen from the cartilage component.

What is the major property of elastic cartilage?

Flexibility.

Where is elastic cartilage found?

External ear and epiglottis.

What fibers are found in elastic cartilage matrix?

Elastic fibers and type II collagen.

What is bone tissue composed of?

Cells and a mineralized extracellular matrix.

What mineral hardens bone matrix?

Hydroxyapatite.

What ions make up hydroxyapatite?

Calcium and phosphate.

What are the two major types of bone tissue?

Compact (lamellar) bone and cancellous/spongy/trabecular bone.

Where is compact bone primarily located?

On the outer surface of bone.

Where is spongy bone primarily located?

Inside bone, underneath compact bone.

What are the two major regions of a long bone?

Diaphysis and epiphyses.

What is the diaphysis?

The shaft/middle portion of a long bone.

What is the medullary cavity?

The hollow space within the diaphysis.

What are the epiphyses?

The ends of a long bone that contain spongy bone.

What type of marrow is associated with blood formation?

Red bone marrow.

What does hemopoietic mean?

Blood forming.

Where is red bone marrow found?

In spaces within spongy bone.

What primarily fills the adult medullary cavity?

Yellow marrow, consisting primarily of white fat.

What is the epiphyseal plate?

A primarily cartilaginous growth plate.

What is the epiphyseal line?

The adult remnant of the epiphyseal growth plate.

What is the periosteum?

Dense fibrous connective tissue covering bone.

What are Sharpey's fibers?

Type I collagen fibers that connect the periosteum to compact bone.

What is osteoid?

The organic matrix of bone.

What are the major components of osteoid?

Type I collagen and ground substance.

What is the inorganic portion of bone primarily composed of?

Calcium and phosphate.

What is ossification?

The process by which osteoid becomes mineralized bone.

What enzyme is important in bone mineralization?

Alkaline phosphatase.

What cells produce osteoid?

Osteoblasts.

How do osteoblasts initiate hydroxyapatite formation?

They release matrix vesicles containing alkaline phosphatase into the matrix.

What accumulates inside matrix vesicles?

Calcium and phosphate.

What happens after hydroxyapatite forms inside a matrix vesicle?

The vesicle ruptures and ossification occurs.

What are osteoprogenitor cells?

Mesenchyme-derived cells that can differentiate into osteoblasts.

What are osteoblasts?

Active bone-forming cells that produce osteoid. Arise from osteoprogenitor cells which come from the mesenchyme

What are osteocytes?

Mature bone cells located within lacunae.

What is a major function of osteocytes?

Maintenance of bone and small repairs.

What are osteoclasts?

Cells that break down/resorb bone.

What is the developmental origin of osteoclasts according to the notes?

Blood-derived cells closely related to monocytes.

What are the two types of bone formation?

Intramembranous ossification and endochondral ossification.

What is intramembranous ossification?

Bone formation from an embryological membrane derived from mesenchyme.

Which bones undergo intramembranous ossification according to the notes?

Cranium, some facial bones, and part of the clavicle.

What is endochondral ossification?

Bone formation through replacement of a hyaline cartilage precursor.

Which type of ossification is responsible for formation of long bones?

Endochondral ossification.

What is the spongy bone of the skull called?

Diploë.

What do mesenchymal cells differentiate into during intramembranous ossification?

Osteoblasts.

What do osteoblasts produce during intramembranous ossification?

Osteoid, which is converted into bone.

How do flat bones increase in size at their surfaces?

Appositional growth.

What do mesenchymal cells differentiate into early in endochondral ossification?

Chondroblasts.

What do chondroblasts produce during endochondral ossification?

A hyaline cartilage precursor.

What type of collagen is characteristic of this cartilage precursor?

Type II collagen.

What happens to the perichondrium around the developing diaphysis?

It begins producing osteoblasts and becomes periosteum.

What is the bony collar?

A layer of bone formed around the diaphysis.

What happens to chondrocytes beneath the bony collar?

They enlarge, secrete alkaline phosphatase, and eventually die as the matrix calcifies.

Why do chondrocytes die after cartilage calcification?

Calcification interferes with diffusion of nutrients and oxygen.

What are cartilage spicules?

Remaining thin walls of cartilage matrix between enlarged spaces.

How does cartilage stain according to the notes?

Basophilic/blue because of its GAG and carbohydrate-rich matrix.

How does bone stain according to the notes?

Acidophilic/pink because type I collagen is a major component.

What happens when blood vessels invade the developing diaphysis?

Mesenchymal cells enter with them and form osteoprogenitor cells.

What do osteoprogenitor cells become after entering the developing bone?

Osteoblasts.

What do osteoblasts deposit onto cartilage spicules?

Osteoid.

What is a mixed spicule?

A spicule containing both cartilage matrix and newly formed bone.

What eventually happens to the cartilage portion of a mixed spicule?

It disappears and is replaced by bone.

What cells create the medullary cavity?

Osteoclasts.

How is the medullary cavity created?

Osteoclasts resorb spongy bone from the diaphysis.

Where does growth in length of a long bone occur?

At the epiphyseal growth plate.

What are the five zones of the epiphyseal growth plate in order?

Reserve cartilage → proliferation → hypertrophy → degeneration → resorption.

What happens in the zone of reserve cartilage?

It consists of relatively unchanged hyaline cartilage.

What happens in the zone of proliferation?

In the 2nd layer of Epiphysial growth plate cells divide, produce cartilage matrix, and organize into columns.

What happens in the zone of hypertrophy?

Chondrocytes enlarge and fill their lacunae.

What happens in the zone of degeneration?

Alkaline phosphatase causes matrix calcification, followed by cell death and formation of gaps.

What happens in the zone of resorption?

Osteoblasts enter, deposit osteoid on remaining surfaces, and produce mixed spicules that become spongy bone.

What allows bone to continue growing in length?

Continued cartilage production in the zone of proliferation provides cartilage that can be replaced by bone.

Where does primary ossification occur?

In the diaphysis.

When does primary ossification begin?

Before birth.

Where does secondary ossification occur?

In the epiphyses.

When does secondary ossification occur?

After birth.

What cartilage remains after secondary ossification?

Articular cartilage (part of Hyaline) and the epiphyseal growth plate.

How does bone increase in width/girth?

Appositional growth.

What is bone remodeling?

The removal of old bone followed by formation of new bone.

What happens to an osteoclast when it becomes active?

It develops a ruffled border.

What regulates osteoclast activity according to the notes?

PTH and cytokines secreted by osteoblasts.

What acid do osteoclasts produce?

Carbonic acid.

What does carbonic acid dissociate into?

Hydrogen ions and bicarbonate ions.

What do osteoclasts use hydrogen ions for?

To create an acidic environment that breaks down hydroxyapatite.

What enzyme breaks down collagen during osteoclast activity?

Cathepsin K.