Bone & Biomechanics 3 Flashcards
What does bone start off as?
A cartilage model in the shape of the eventual bones is formed 6 weeks after fertilization
How is the cartilage transformed into bone?
Endochronal ossification
What is endochronal ossification?
Chemical signals cause the centre of the cartilage to become calcified. This continues to happen and blood vessels form outside the cartilage which brings osteoblasts that secrete bone matrix. The osteoblasts can make their way to the centre of the shaft to form the diaphysis of the bone.
What is the primary ossification centre?
Diaphyses
What is the secondary ossification centre?
Epiphyses
Do the epiphyses and diaphyses develop at the same time?
No. When the diaphyses is bone, the epiphyses may still be cartilage depending on which bone it is.
What separates the diaphyses and epiphyses?
Then epiphyseal plate
What is the epiphyseal plate made of?
Cartilage
What does the epiphyseal plate allow?
Growth of the bone in length
What is the maintaining cells of cartilage?
Chondrocytes
How do bones grow in length?
The chondrocytes at the epiphyseal side of the cartilage continue to grow while on the diaphyses side they degenerate. Osteoblasts in the diaphysis can then move upwards and so cartilage is replaced by bone until eventually the whole growth plate disappears.
Why must bones grow in width and length?
For strength
What is the purpose of joints?
To hold bones together and allow for movement and control of movement
What is an articulation?
Where two or more bones meet
What is involved in a joint?
Bone shapes and soft tissue which holds everything together
What soft tissues are found at joints?
Cartilage, ligaments, muscles and tendons. Depends on the type of joint though
Why are soft tissues soft?
Because they have no inorganic (mineral) component
What is the structure of cartilage?
Collagen fibres are found in the ground substance along with water and some proteins. The maintaining chondrocyte cells are found in lacunae.
What is joint loading?
When pressure is put on a joint and the nutrients diffuse through the soft tissue matrix to reach the chondrocytes as blood vessels don’t penetrate cartilage.
What are the two types of cartilage?
Hyaline cartilage and fibrocartilage
What is the structure of hyaline cartilage?
Collagen fibres which are barely visible in the matrix which has a high water content
What is the function of hyaline cartilage?
To resist compression and provide a smooth, frictionless surface
Where is hyaline cartilage found and why?
Hyaline cartilage moulds to the outer surface of bones to form a covering where they articulate. This allows for smooth, frictionless movement because cartilage is moving over cartilage.
What happens to hyaline cartilage as we get older?
It degrades which means bone ends up rubbing over bone and this results in joint degradation
What is the structure of fibrocartilage?
Bundles of collagen fibres found throughout the matrix
How are the collagen fibres arranged?
To align with the stresses
What is the function of fibrocartilage?
To resist compression and tension. This is done by deepening the articulation surface and acting as a shock absorber because force is spread over a wider area.
Where is fibrocartilage found?
At articulations which experience compression and tension
What are ligaments and tendons made of?
Dense Fibrous Connective Tissue, collagen, elastin and fibroblasts (cytes)
What is DFCT made of?
Dense Fibrous Connective Tissue is made of protein fibres closely packed together
What is the difference between collagen and elastin?
Elastin is more stretchy
What do tendons connect?
Muscle to bone
What is the function of tendons?
To facilitate and control movement. The contraction of muscles is transmitted to bone
What has more elastin present?
Tendons
What do ligaments connect?
Bone to bone
What is the function of ligaments?
To restrict movement away from themselves
What do lateral ligaments restrict?
Movement medially
What do medial ligaments restrict?
Movement laterally
What is found in ligaments?
Minimal elastin compared to collagen
What is bony congruence?
The amount of surface area of bone touching
What does bony congruence affect?
The amount of soft tissue present in a joint. Less bony congruence means the joint will need more soft tissue support
What are tissues?
Cells grouped together in a highly organised manner according to a specific structure and function
What are structures?
Something formed of a tissue/s
What is the tissue found in fibrous joints?
Dense Fibrous Connective Tissue
What is the structure of fibrous joints?
Ligaments
What is the function of fibrous joints?
The ligaments limit movement and provide stability
What is examples of fibrous joints?
Cranial sutures and the distal tibiofibular joint
What is the tissue found in cartilaginous joints?
Fibrocartilage
What is the structure of cartilaginous joints?
Cartilage
What is the function of cartilaginous joints?
To allow slight movement, absorb shock and resist tension
What is examples of cartilaginous joints?
Fibrocartilage pad between vertebrae and the pubic symphysis
What is special about synovial joints?
They are free moving
Where are synovial joints found?
Most upper and lower limb joints
What does joint structure determine?
The amount and direction of movement
What is a synovial joints?
A complex association of tissues and structures
What is the function of synovial joints?
To facilitate free movement and control of movement
What determines the range and amount of movement?
Bone ends and bony congruence
What structures are found in synovial joints?
Bone ends, articular cartilage, joint capsule, joint cavity, synovial membrane and ligaments
What is the purpose of the articular cartilage?
To provide frictionless easy movement
What is the subchondral bone?
The bone beneath the articular cartilage which is smooth so that the cartilage is also smooth
Where is the synovial membrane found?
Lining the inner surface of the joint capsule
What does the synovial membrane do?
secretes synovial fluid for lubrication of the joint
What type of tissue is the synovial membrane?
Epithelial tissue
Why is the synovial fluid important?
Because it contains nutrients which can be passed into soft tissue by joint loading to repair damage
What is the purpose of the joint capsule?
To hold the bones together
What is the structure of the joint capsule?
Tight and thick where support is required and loose where movement is allowed
What is a potential space?
The joint capsule is a potential space as it is only there if we need it
What are the capsular ligaments?
Thickened areas of the joint capsule in some joints which need more support
What are intracapsular ligaments?
Ligaments found inside the joint capsule but aren’t part of it.
What is the function of intracapsular ligaments?
To restrict movement between bones
What are the functions of fibrocartilaginous pads?
To make bones fit together better as they counteract the low bony congruence. Also resisting compression and dispersing weight through a wider area
What does uniaxial mean?
Movement in one axis
What does biaxial mean?
Movement in 2 axis
What does mulitaxial mean?
Movement in 3 axis
If movement occurs in the saggital axis what plane is the?
Coronal
If movement occurs in the coronal axis what plane is the?
saggital
If movement occurs in the vertical axis what plane is the?
transverse
What is range of motion determined by?
Bone end shape, ligament location and length, body surface contact
What are the seven synovial joint shapes?
Plane, hinge, pivot, condylar, ellipsoid, saddle, ball and socket
What axial is a plane joint?
Multiaxial
What movement occurs at a plane joint?
Small sliding and gliding of flat articular surfaces
What joints are plane joints?
Intertarsal and inter carpal joints
What axial is a hinge joint?
Uniaxial
What movement occurs at a hinge joint?
Flexion and extension
What joints are hinge joints?
Ankle, elbow, interphalangeal
What axial is a pivot joint?
Uniaxial
What movement occurs at a pivot joint?
Rotation/turning
What joints are pivot joints?
Radioulnar, C2-C2 vertebrae
What axial is a condylar joint?
Biaxial
What movement occurs at a condylar joint?
Flexion, extension and rotation when flexed
What joints are condylar joints?
Knee, temporomandibular joint
What axial is an ellipsoid joint?
Biaxial
What movement occurs at an ellipsoid joint?
Flexion, extension, adduction, abduction and circumduction
What joints are an ellipsoid joint?
Wrist joint as rotation only occurs at the forearm
What axial is a saddle joint?
Biaxial + as not as mobile as multiaxial
What movement occurs at a saddle joint?
Flexion, extension, adduction, abduction, circumduction, opposition
What joints are a saddle joint?
Carpometacarpal joint at the base of the thumb
What axial is a ball and socket joint?
Multiaxial
What movement occurs at a ball and socket joint?
Flexion, extension, adduction, abduction, circumduction, rotation
What joints are a ball and socket joint?
Shoulder and hip
