Lecture 3: Introduction to the Skeletal System Flashcards
What kind of tissue are Cartilage and bone?
Specialized connective tissue
What is the function of Cartilage?
- Supports and preserves soft tissues
- Provides a smooth, frictionless shock absorbing surface at articulations (joints)
- Provide a model for the formation of the majority of bones in the body
What are the properties of Cartilage?
- Resists compression
- Firm yet flexible
- Avascular
How is Cartilage supported since its avasacula?
•It undergoes exchange of nutrients and wastes by diffusion with another CT
What is a consequence of Cartilage being Avascular?
- Its thickness is restricted
* It capacity to heal is restricted
What are most Cartilage surrounded by?
Perichondrium
What are Mesenchymal cells?
The stem cells of all connective tissue
What are Chondroblasts?
Immature cartilage cells the secrete ECM
What are Chondrocytes?
Mature cartilage cells that Maintain ECM
What occurs when Chondrocytes die?
They activate calcification of the extracellular matrix which makes bone
What are the 3 different types of Cartilages?
- Hyaline Cartilage
- Elastic Cartilage
- Fibrocartilage
What differentiates the type of Cartilage?
- Type of fibers found in them
* How many of those fibres there are
What is the function of Hyaline Cartilage?
Provide support, flexibility, and resilience
Where is Hyaline Cartilage found?
- Growth plates
- Costal cartilage
- Most respiratory cartilage
- Nasal cartilage
- Articular cartilage
What is different about Fibrocartilage?
It never exists on its own, is a transition cartilage
How can Hyaline cartilage get nutrients?
Either through bone or synovial joints that have the synovial membrane to nourish
What is the function of Elastic Cartilage?
Provide more elasticity and maintain shape of the structure while allowing flexibility
Where is Elastic Cartilage found?
- Epiglottis
* External ear
What is Fibrocartilage super specialized to do?
Be highly compressible with tensile strength
Where are some places that fibrocartilage is found?
- Menisci of synovial joints (knee)
- Intervertebral discs
- Pubic symphysis
- Temporomandibular joint (TMJ)
What tissue are Intervertebral discs made of?
Fibrocartilage
What are the function of Bones?
- Support and protect soft tissue
- Support and generates shape of body
- Muscle/Tendon attachments
- Dynamic Mineral storage
- Marrow space for blood formation
What minerals does Bone store?
Calcium and Phosphate ions
What does Calcium Phosphate do for bones?
Makes it very strong but inflexible; making it resists compressive stress
What do Collagen fibers do for bones?
They make it tough and flexible; allowing it to resist stretching, bending, and twisting stress
What is the Composite material that makes up bone?
Calcium phosphate and collagen fibers
What are cells in bone embedded in?
The Matrix
What is the turnover rate of bones?
They have a high turnover
Why do bones break down sometimes?
Because sometimes the minerals are needed
What are the two types of Connective tissue that bones are surrounded by?
Periosteum (outer) and Endosteum (inner)
What is the meaning behind ‘bone is Anisotropic’?
Bone has different strength depending on its orientation
What are the two types of bone?
- Spongy (Cancellous/trabecular) bone
* Compact (Cortical) bone
What is the Diaphysis?
the shaft of the bone
Which part of the bone does the bone start growing?
the Diaphysis
What is the Epiphysis?
The end of the bone
What is the Metaphysis?
The transitional portion of the bone
What are the features of Spongy (cancellous/trabecular) bone?
Open network of struts and plates
What are the features of Compact (cortical) bone?
- Relatively dense and solid
* Reservoir for minerals
What are the features of the Endosteum and Periosteum?
- Highly vascularized
- Contain stem cells
- Can grow by increasing diameter (appositional growth)
What is Appositional growth?
Growth by increasing diameter
Where is the Medullary cavity?
In the middle of bones
What does the Medullary cavity contain?
- Yellow marrow (adipocytes)
* Red marrow
What is Red marrow?
Mature and immature red and white blood cells
How do Osteoblasts become Osteocytes?
Osteoblasts secrete fluid that collides with gel that attract minerals to form osteocytes
What are Osteoclasts?
Cells the break down bone
How do Osteoclasts work?
They suck out all the mineral and put it in the bloodstream
How are Osteons organized?
In concentric layers around a central canal containing blood vessels. They are oriented in the line of stress
What are the two ways the bones form?
- Intramembranous ossification
* Endochondral Ossification
What occurs in Intramembranous ossification?
Osteoblasts differentiate directly from mesenchymal cells
What are the usual bones that develop from Intramembranous ossification?
Mainly flat bones (e.g, crania, face)
What occurs in Endochondral ossification?
Bone replaces a hyaline cartilage template
What kind of bones are usually formed in Endochondral ossification?
Mainly long bones (e.g., limbs, ribs vertebrae)
What is the process of Intramembranous growth?
Mesenchymal cells differentiate into osteoblasts forming a center of ossification forming spongy bone. Then it attracts blood vessels that migrate towards it and get trapped with it. The periosteum forms at extremities. Trabeculae become interconnected to form spongy like bone
What are the steps in Endochondral Growth (Pre-natal)?
Mesenchymal cells form chondroblasts which form chondrocytes. The chondrocytes secrete matrix creating a hyaline cartilage model. The large chondrocytes secrete an attractant for blood vessels and then undergo cell death. The invading blood vessels bring osteoblasts and osteoclasts which will make bone
When do all Primary ossification centres develop?
In utero
What makes the Periosteum in Endochondral growth?
The dying off mesenchyme
What is the Endochondral growth (Post-natal)?
The epiphyses are still cartilage and secondary ossification occurs to expand and ossify most of the epiphysis
What remains between the epiphysis and diaphysis?
The Epiphyseal cartilage plate
What does the Epiphyseal cartilage plate allow for?
Growth (lengthening) of the bone until it fuses with the metaphysis and is fused with bone
What is Interstitial growth?
Growth in length
What is Appositional growth?
The change in diameter or the change in shape of the bone
What happens when bone gets reabsorbed by Osteoclasts?
The inner segment increases in diameter
What happens when bone is deposited by Osteoblasts?
The diameter of the outer part
After growth plates have fused how can bones grow?
They can grow appositionally in response to stimuli or bone damage
How does Bone Repair work?
- After the fracture bleeding occurs and a clot forms
- An internal callus forms as spongy bone forms inside and cartilage and bone stabilize outside
- Cartilage is replaced by bone and the struts of the spongy bone unite
What are Joints places of contact between?
- Bone and bone
- Bone and Cartilage
- Bone and Tooth
What does structure of the joint determine?
Its mobility and stability
What are the two ways joints can be classified?
1) The CT that binds the bones together and the potential space between them
2) Functionality
What are the 3 types of Joints?
- Fibrous joints
- Cartilaginous joints
- Synovial joints
What are Fibrous Joints?
When bones are held together by fibrous connective tissue
What are some examples of fibrous joints?
Sutures between skull bones
Interosseous membrane between radius and ulna
Gomphosis that holds teeth in the jaw
What is the Interosseous membrane?
A type of fibrous joint that connects the radius and ulna
What are Cartilaginous joints?
When bones are joined by cartilage
What are the two types of Cartilaginous Joints?
- Primary/Synchondrosis
* Secondary/Symphysis
What are Primary or Synchondrosis Cartilaginous joints?
Temporary cartilaginous union between bones
What do Primary or Synchondrosis Cartilaginous joints allow for?
Don’t allow movement but allow growth
What are Secondary or Symphysis Cartilaginous joints?
Permanent Cartilaginous union between bones
What are examples of Secondary or Symphysis Cartilaginous joints?
Intervertebral discs
Pubic symphysis
What are examples of Primary or Synchondrosis Cartilaginous joints?
Cartilage of growth plate
What are Synovial joints?
Fluid filled cavity that separates cartilage-covered joint surface
What do Synovial joints allow for?
Allow for motion especially in the limbs
What si the difference between a hinge joint and a ball and socket joint?
A hinge joint is uniaxial and a ball-and-socket joint is multiaxial
