lecture 5 - bone growth + joint tissue

Question 1

What do bones begin as?

Answer 1

Cartilage models

Question 2

What are cartilage models made of?

Answer 2

Hyaline

Question 3

What is the name of the process of turning cartilage models into bone?

Answer 3

Endochondral ossification

Question 4

What type of cartilage cells excrete cartilage matrix in the cartilage model initially?

Answer 4

Chondrocytes

Question 5

What role to the blood vessels that develop around the cartilage model serve?

Answer 5

They supply fibroblasts, which differentiate into osteoblasts, which build bone.

Question 6

What is the first bone structure formed in a developing bone?

Answer 6

A superifical layer of bone on the diaphysis under the periosteum - a ‘collar’ of bone

Question 7

Where is the primary ossification centre of long bones?

Answer 7

In the diaphysis.

Question 8

When blood vessels penetrate the centre of the developing bone, what occurs?

Answer 8

Osteoblasts produce cancellous/spongy bone in the shaft of the long bone.

Question 9

What does remodelling in the developing bone create?

Answer 9

A medullary cavity.

Question 10

How are the secondary ossification centres formed?

Answer 10

Capilalries and osteoblasts migrate into the ephysises.

Question 11

What is intersitital growth?

Answer 11

The lengthening of the diaphysis/bone shaft, which takes place at the metaphysis.

Question 12

What is the metaphysis?

Answer 12

The narrowed area that seperates the diaphysis from the epiphysis.

Question 13

What seperates the spongy bone of the epiphysis from the diaphysis, during development?

Answer 13

The epiphyseal plate/growth plate

Question 14

What is the epiphyseal plate?

Answer 14

A layer of cartilage that seperates the epiphysis of a bone from the diaphysis, allowing the diaphysis to grow in length.

Question 15

What happens when bone size is at its maximum and epiphyseal plate disappears?

Answer 15

An epiphyseal closure will be formed by osteoblasts.

Question 16

Do soft joint tissues have inorganic components?

Answer 16

No

Question 17

What is the overall structure of cartilage?

Answer 17

Collagen fibres in a ground substance. Chondrocytes in lake like lacunae.

Question 18

Does cartilage have blood supply?

Answer 18

No

Question 19

How do nutrients reach cartilage cells?

Answer 19

By diffusing through the matrix via joint loading as pressure is applied to the joint

Question 20

Why does cartilage take a long time to heal?

Answer 20

It does not have a blood supply, so nutrients are slowly diffused through the matrix meaning repair is slow.

Question 21

What is the name for hyaline that coats bone ends, which reflects its function?

Answer 21

Articular cartilage

Question 22

What is the function of articular cartilage?

Answer 22

It moulds to the surfaces of bones where they rub together, ensuring movement is smooth and reducing friction. resists compression

Question 23

What is the microscopic structure of hyaline cartilage?

Answer 23

Invisible collagen fibres in a watery ground substance, which prevents the hyaline from rupturing when compressed. Contains chondrocytes in lacunae.

Question 24

Where is fibrocartilage found?

Answer 24

At articulations/joints that experience compression and tension.

Question 25

What is the main fibrocartilage structure of the knee?

Answer 25

The meniscus

Question 26

What is the structure of fibrocartilage?

Answer 26

Dense layers of bundles of collagen fibres (in watery ground mass) that align with the directions of stresses, making it resistant to compression and tension. Contains chondrocytes in lacunae.

Question 27

What are ligaments and tendons made up of?

Answer 27

Dense Fibrous Connective Tissue

Question 28

Why do ligaments and tendons heal slowly?

Answer 28

They have limited vascularity - very little blood supply.

Question 29

What fibres do ligaments and tendons have?

Answer 29

Elastin and Collagen

Question 30

What is the function of collagen in ligaments and tendons?

Answer 30

Provide give, and align with stresses to resist tension.

Question 31

What is the role of elastin fibres in ligaments/tendons?

Answer 31

Elastin provides stretch and restores the positions of bones when moved out of position.

Question 32

What cells make DFCT tissue?

Answer 32

Fibroblasts

Question 33

What is the inactive/mature form of fibroblasts?

Answer 33

Fibrocytes

Question 34

What do ligaments connect?

Answer 34

Bone with bone

Question 35

What is the function of ligaments?

Answer 35

They restrict the movement of bones at joints, preventing them from slipping and creating stability.

Question 36

Do ligaments or tendons contain more elastin?

Answer 36

Ligaments - they need to stretch and recoil to keep bones together

Question 37

What do tendons connect?

Answer 37

Muscle with bone

Question 38

How do tendons facilitate movement?

Answer 38

They transmit muscle contraction/movement to the bone.

Question 39

Why do tendons contain less elastin that ligaments?

Answer 39

They do not need to stretch or recoil, they must pull the bones precisely.

Question 40

What is bony congruence?

Answer 40

The sum of the bone surfaces that form an articulation.

Question 41

What does low bone congruence mean?

Answer 41

There is little contact between the bones at an articulation, meaning more soft tissue is required to stabilise the joint.

Question 42

What is the function of a fibrous joint?

Answer 42

They limit movement and hold two bones firmly together with ligaments (DFCT).

Question 43

Cranial sutures are what type of joint?

Answer 43

Fibrous joint

Question 44

What are cartilaginous joints?

Answer 44

They allow for some movement, by forming soft, squishy fibrocartilage ‘pads’ that resist compression and tension.

Question 45

What type of joint sits between vertebrae?

Answer 45

Cartilaginous joints

Question 46

What is the structure of elastic cartilage?

Answer 46

Collagen in watery ground substance, chondrocytes in lacunae. Contains lots of elastin fibres

Question 47

What is the difference between appositional growth and endochondral ossification?

Answer 47

Appositional growth is growth of existing bone, endochondral ossification forms bone from cartilage model. Appositional growth builds new bone at periosteum where osteogenic cells differentiate into osteoblasts to build new circumferential lamellae. Endochondral ossification, has periosteum osteogenic cell compact bone secretion, as well as fibroblast to osteoblast differentiation in primary ossification centre, secreting bone matrix.

Question 48

What are the functions of synovial fluid? (3)

Answer 48

Lubrication, nutrient distribution, shock absorption