bone growth and joints Flashcards
How do bones grow in length?
✔ Bones start as a cartilage model (~6 weeks after fertilization).
✔ Endochondral ossification – the process of turning cartilage into bone.
✔ Primary ossification center forms in the diaphysis (shaft).
✔ Secondary ossification centers form in the epiphyses (ends of bones).
✔ Epiphyseal (growth) plate separates diaphysis & epiphyses and allows for bone elongation.
✔ Growth plates fuse at puberty, stopping further lengthening.
How do bones grow in width?
✔ Appositional growth – osteoblasts produce circumferential lamellae, increasing width.
✔ Osteoclasts break down bone inside to form the medullary cavity.
What is the difference between primary and secondary ossification centers?
✔ Primary ossification center – forms in the diaphysis, responsible for initial bone formation.
✔ Secondary ossification centers – develop in the epiphyses, allowing later bone growth.
What is the difference between epiphyseal plates and appositional growth?
✔ Epiphyseal plates – allow growth in length (cartilage turns into bone).
✔ Appositional growth – increases width through osteoblast activity.
What are the key soft tissues in joints?
✔ Cartilage – cushions and protects bones.
✔ DFCT (dense fibrous connective tissue) – forms ligaments and tendons.
✔ Ligaments – connect bone to bone, provide stability.
✔ Tendons – connect muscle to bone, control movement.
✔ Joint capsules – enclose synovial joints.
What are the two main types of cartilage in joints?
✔ Hyaline (articular) cartilage – resists compression, provides smooth, frictionless movement.
✔ Fibrocartilage – resists both compression & tension, acts as a shock absorber.
What are the properties of hyaline (articular) cartilage?
✔ Function: Provides smooth movement, reduces friction.
✔ High water content – helps resist compression.
✔ Sparse collagen fibers – allows smooth articulation.
✔ Found on: Bone surfaces at joints.
✔ Degrades with age, leading to arthritis.
What are the properties of fibrocartilage?
✔ Function: Resists compression & tension, absorbs shock.
✔ Collagen fibers in bundles – align with forces experienced.
✔ Found in joints with both compression and tension (e.g., intervertebral discs, knee meniscus).
✔ Distributes force over a wider area, reducing wear on joints.
What are the key differences between hyaline cartilage and fibrocartilage?
✔ Hyaline cartilage – smooth, low friction, resists compression, found in joint surfaces.
✔ Fibrocartilage – stronger, resists tension & compression, found in intervertebral discs and menisci.
What are the properties of DFCT?(Dense Fibrous Connective Tissue)
✔ Fibroblasts produce collagen fibers.
✔ Tightly packed collagen resists tension.
✔ Little vascularity, so healing is slow.
✔ Forms ligaments and tendons.
What is the function of ligaments?
✔ Connect bone to bone.
✔ Made of collagen & elastin – strong but slightly flexible.
✔ Restrict movement – prevent excessive motion.
✔ Example: ACL (anterior cruciate ligament) stabilizes the knee.
What is the function of tendons?
✔ Connect muscle to bone.
✔ Contain less elastin than ligaments – more rigid.
✔ Facilitate movement by transmitting muscle force to bones.
✔ Example: Achilles tendon connects calf muscles to the heel.
What is bony congruence, and why is it important?
✔ Bony congruence = the total surface area where bones meet.
✔ Lower congruence = more reliance on soft tissue for stability.
✔ Example: Shoulder joint has low congruence, so it depends on muscles & ligaments for stability.
What are the three types of joints?
✔ Fibrous joints – least movement, high stability (e.g., skull sutures).
✔ Cartilaginous joints – some movement, shock absorption (e.g., intervertebral discs).
✔ Synovial joints – most movement, complex structure (e.g., knee, shoulder).
What are the characteristics of fibrous joints?
✔ Tissue = DFCT.
✔ Structure = ligament connecting bones.
✔ Function = limit movement, provide stability.
✔ Examples:
Cranial sutures – protect the brain.
Distal tibiofibular joint – prevents ankle rotation.
What are the characteristics of cartilaginous joints?
✔ Tissue = fibrocartilage.
✔ Function = some movement, shock absorption.
✔ Bones are connected entirely by cartilage.
✔ Examples:
Intervertebral discs – absorb shock in the spine.
Pubic symphysis – stabilizes pelvis.
What are the characteristics of synovial joints?
✔ Most mobile joints in the body.
✔ Tissues & structures involved:
Articular (hyaline) cartilage – cushions bones.
Joint capsule – encloses the joint.
Synovial membrane – secretes synovial fluid for lubrication.
✔ Examples: Shoulder, knee, hip, wrist.
Which tissue resists both compression and tension?
Fibrocartilage – strong fibers align with stress, found in intervertebral discs & knee menisci.
What allows bones to grow in length vs. width?
✔ Length – epiphyseal (growth) plates.
✔ Width – appositional growth (osteoblasts & osteoclasts remodel bone).
What type of joint has the least movement?
(e.g., skull sutures, distal tibiofibular joint).
What is the main function of ligaments?
Restrict movement and provide stability by connecting bone to bone.
What is the main function of tendons?
Transmit muscle force to bone, facilitating movement.
