BL - Cartilage And Endochondral Ossification

Question 1

What is the name given to an avascular tissue which consists of an extensive extracellular matrix in which lie chondrocytes?

Answer 1

Cartilage!

Question 2

What is the function of chondrocytes in cartilage?

Answer 2

They produce and maintain the extracellular matrix. Chondrocytes are the only cells found in healthy cartilage.

Question 3

What is the benefit of having a large ratio of GAGs to type 2 collagen in the cartilage matrix?

Answer 3

It permits ready diffusion of substances between the chondrocytes and the blood vessels surrounding the cartilage.

Question 4

The large amount of hyaluronic acid in the extracellular matrix allows it to be resilient to what?

Answer 4

Repeated application of pressure. The matrix is solid and firm but still pliable.

Question 5

How do GAGs attract water? (hint - it’s to do with the charge)

Answer 5

The high density of negative charges attract water, forming a hydrated gel.

Question 6

What are the three types of cartilage?

Answer 6

Hyaline, elastic, fibrocartilage.

Question 7

How is hyaline cartilage structured?

Answer 7

Matrix containing proteoglycans, hyaluronic acid and type II collagen.

Question 8

How is elastic cartilage structured?

Answer 8

Matrix like hyaline cartilage but with elastic fibres and elastic lamellae.

Question 9

How is fibrocartilage structured?

Answer 9

Abundant type I collagen in addition to hyaline matrix structure.

Question 10

What is an “isogenous group” in cartilage?

Answer 10

A small cluster of recently divided chondrocytes.

Question 11

How many different types of cell are present in hyaline cartilage?

Answer 11

Just one (chondrocytes).

Question 12

Where is hyaline cartilage situated?

Answer 12

At “articulating surfaces” (where bones rub together lots), in parts of rib cage, trachea, bronchi and larynx.

Question 13

What is the role of hyaline cartilage in the developing foetus?

Answer 13

It is the pre-cursor of bones which develop via echondral ossification.

Question 14

What is the perichrondrium?

Answer 14

A layer of dense connective tissue which covers the margin of hyaline cartilage. It contains many cells which can develop into chondrocytes. (It’s basically like having loads of spare tyres).

Question 15

Cartilage grows in from the perichrondrium towards the chondrocytes. What is this called?

Answer 15

Appositional growth

Question 16

How is the activity of the chondrocytes directed?

Answer 16

Pressure loads applied to the cartilage create mechanical, electrical and chemical signals that direct the synthetic activity of the chondrocytes.

Question 17

Is the perichondrium present at articulating surfaces?

Answer 17

Nope.

Question 18

What is the name given to the end of a bone?

Answer 18

The epiphysis.

Question 19

What is a lacuna?

Answer 19

A small space containing an osteocyte in bone, or a chondrocytes in cartilage.

Question 20

Does elastic cartilage calcify with aging?

Answer 20

Nah. Hyaline does though.

Question 21

Where is elastic cartilage found?

Answer 21

The external ear (pinna), acoustic meatus, epiglottis and eustachian tube.

Question 22

Why does elastic cartilage often appear dark on images?

Answer 22

An abundance of elastin fibres.

Question 23

What is fibrocartilage? Which cells does it contain?

Answer 23

It is a combination of dense regular connective tissue and hyaline cartilage. It contains chondrocytes and fibroblasts.

Question 24

Where is fibrocartilage found?

Answer 24

Intervertebral discs, menisci of knee, pubic symphysis, articulate discs of sternoclavicular (chest) and temporomandibular (side of head) joints.

Question 25

What is an enthesis?

Answer 25

A point of attachment of tendon and bone. Fibrocartilage may be present here.

Question 26

What is endochondral ossification?

Answer 26

The REPLACEMENT of a pre-existing HYALINE CARTILAGE TEMPLATE with BONE, which is the way that most of the bones of the body develop.

Question 27

What is an epiphyseal growth plate?

Answer 27

A hyaline cartilage plate found at the end of each long bone. It is where growth initiates from, and disappears once adulthood is reached.

Question 28

At which stage of development does a “collar” of periosteal bone begin to appear in the shaft of the developing bone?

Answer 28

6-8 weeks (embryo)

Question 29

At which stage of development does the central cartilage calcify, the nutrient artery penetrate and the primary ossification centre form?

Answer 29

8-12 weeks (foetus)

Question 30

During postnatal development, the medulla becomes cancellous bone and the cartilage forms _____ plates. Epiphyses develop secondary _______ .

Answer 30

1) epiphyseal growth plates

2) centres of ossification

Question 31

At what stage of human development do the epiphyses ossify?

Answer 31

Pre-puberty

Question 32

When are the epiphyses growth plates replaced by bone?

Answer 32

When maturity is reached.

Question 33

What’s the difference between an osteoblast and an osteoclast?

Answer 33

Osteoblasts make bone, osteoclasts degrade it.

Question 34

What is a synovial joint?

Answer 34

A moveable joint where the bone ends are covered by hyaline cartilage/fibrocartilage and lie within lubricating synovial fluid bounded by a joint cavity.

Question 35

What does the synovial membrane consist of?

Answer 35

MACROPHAGES (remove debris from joint space) and FIBROBLAST-LIKE CELLS (secrete synovial fluid probably)