lecture 5 - bone growth + joint tissue Flashcards
What do bones begin as?
Cartilage models
What are cartilage models made of?
Hyaline
What is the name of the process of turning cartilage models into bone?
Endochondral ossification
What type of cartilage cells excrete cartilage matrix in the cartilage model initially?
Chondrocytes
What role to the blood vessels that develop around the cartilage model serve?
They supply fibroblasts, which differentiate into osteoblasts, which build bone.
What is the first bone structure formed in a developing bone?
A superifical layer of bone on the diaphysis under the periosteum - a ‘collar’ of bone
Where is the primary ossification centre of long bones?
In the diaphysis.
When blood vessels penetrate the centre of the developing bone, what occurs?
Osteoblasts produce cancellous/spongy bone in the shaft of the long bone.
What does remodelling in the developing bone create?
A medullary cavity.
How are the secondary ossification centres formed?
Capilalries and osteoblasts migrate into the ephysises.
What is intersitital growth?
The lengthening of the diaphysis/bone shaft, which takes place at the metaphysis.
What is the metaphysis?
The narrowed area that seperates the diaphysis from the epiphysis.
What seperates the spongy bone of the epiphysis from the diaphysis, during development?
The epiphyseal plate/growth plate
What is the epiphyseal plate?
A layer of cartilage that seperates the epiphysis of a bone from the diaphysis, allowing the diaphysis to grow in length.
What happens when bone size is at its maximum and epiphyseal plate disappears?
An epiphyseal closure will be formed by osteoblasts.
Do soft joint tissues have inorganic components?
No
What is the overall structure of cartilage?
Collagen fibres in a ground substance. Chondrocytes in lake like lacunae.
Does cartilage have blood supply?
No
How do nutrients reach cartilage cells?
By diffusing through the matrix via joint loading as pressure is applied to the joint
Why does cartilage take a long time to heal?
It does not have a blood supply, so nutrients are slowly diffused through the matrix meaning repair is slow.
What is the name for hyaline that coats bone ends, which reflects its function?
Articular cartilage
What is the function of articular cartilage?
It moulds to the surfaces of bones where they rub together, ensuring movement is smooth and reducing friction. resists compression
What is the microscopic structure of hyaline cartilage?
Invisible collagen fibres in a watery ground substance, which prevents the hyaline from rupturing when compressed. Contains chondrocytes in lacunae.
Where is fibrocartilage found?
At articulations/joints that experience compression and tension.
What is the main fibrocartilage structure of the knee?
The meniscus
What is the structure of fibrocartilage?
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.
What are ligaments and tendons made up of?
Dense Fibrous Connective Tissue
Why do ligaments and tendons heal slowly?
They have limited vascularity - very little blood supply.
What fibres do ligaments and tendons have?
Elastin and Collagen
What is the function of collagen in ligaments and tendons?
Provide give, and align with stresses to resist tension.
What is the role of elastin fibres in ligaments/tendons?
Elastin provides stretch and restores the positions of bones when moved out of position.
What cells make DFCT tissue?
Fibroblasts
What is the inactive/mature form of fibroblasts?
Fibrocytes
What do ligaments connect?
Bone with bone
What is the function of ligaments?
They restrict the movement of bones at joints, preventing them from slipping and creating stability.
Do ligaments or tendons contain more elastin?
Ligaments - they need to stretch and recoil to keep bones together
What do tendons connect?
Muscle with bone
How do tendons facilitate movement?
They transmit muscle contraction/movement to the bone.
Why do tendons contain less elastin that ligaments?
They do not need to stretch or recoil, they must pull the bones precisely.
What is bony congruence?
The sum of the bone surfaces that form an articulation.
What does low bone congruence mean?
There is little contact between the bones at an articulation, meaning more soft tissue is required to stabilise the joint.
What is the function of a fibrous joint?
They limit movement and hold two bones firmly together with ligaments (DFCT).
Cranial sutures are what type of joint?
Fibrous joint
What are cartilaginous joints?
They allow for some movement, by forming soft, squishy fibrocartilage ‘pads’ that resist compression and tension.
What type of joint sits between vertebrae?
Cartilaginous joints
What is the structure of elastic cartilage?
Collagen in watery ground substance, chondrocytes in lacunae. Contains lots of elastin fibres
What is the difference between appositional growth and endochondral ossification?
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.
What are the functions of synovial fluid? (3)
Lubrication, nutrient distribution, shock absorption
