1. Basic Concepts In MSK - Bone Flashcards
What are the three major components of the MSK?
Bone, skeletal muscle, connective tissues`
From which of the germ layers do the three major components of the MSK derive from?
Mesoderm
What are the 6 functions of bone?`
• Support • Protection • Metabolic • Storage • Movement (i.e. joints) • Haematopoiesis
Describe the function of bone to support
The skeleton provides the framework for maintaining our body posture, with the limbs acting as pillars to support the trunk in space, and the rib cage supporting the thoracic wall.
Describe the function of bone as protection
- The ribs protect the lungs and heart;
- the skull protects the brain;
- the vertebrae protect the spinal cord
- the pelvic structures are protected by the bony pelvis
Describe the metabolic function of bone
- Bone is a living, actively-metabolising tissue; it is not inert.
- The metabolic functions of bone largely involve the homeostasis of calcium and phosphate.
Describe the storage function of bone
- the skeleton is the main body reservoir for calcium and phosphate.
- bone also contains a large amount of protein (e.g. collagen) and the bone marrow is rich in fat.
- The skeleton is the primary site of storage of some growth factors and cytokines e.g. insulin like growth factors, transforming growth factors and bone morphogenetic proteins (BMPs).
Describe the function of bone in movement
• Movement occurs at joints between bones.
• The bones act as an attachment site for the muscles and tendons, which use the bones as levers.
• The shape of the articulating surfaces determines the range of
motion.
Describe the haemopoietic function of bone, including where it occurs in children and adults
• This takes place within the cavities of the bones.
• In children, the long bones such as the femur and
tibia are important sites of haematopoiesis
• in the adult the residual sites are mainly the pelvis, skull, vertebrae and the sternum.
What are the 6 functions of skeletal muscle?
1) LOCOMOTION: Contraction of muscles acting across a joint lead to movement of that joint
2) POSTURE: Postural muscles enable us to maintain equilibrium e.g. when standing upright
3) METABOLIC: fast-twitch and slow-twitch
4) VENOUS RETURN: The muscles in the leg compress deep veins and help to propel venous blood back up towards the heart.
5) HEAT PRODUCTION: Shivering results in an increase in the metabolic rate of muscle, which in turn results in the generation of heat (thermogenesis) and an increase in body temperature
6) CONTINENCE: The muscles of the pelvic floor are responsible for the maintenance of urinary and faecal continence
What are the different types of connective tissue?
Tendons Ligaments Fascia Cartilage - hyaline/elastic/fibrocartilage Synovial membrane
What are the functions of tendons?
Tendons connect muscle to bone.
Their role is force-transmission from the contracting the muscle to the bone to which they are attached.
Through what are tendons anchored to bone?
Sharpey’s fibres
Why do tendons heal slowly?
Relatively poor blood supply
Low water content - limits diffusion of nutrients
Why don’t tendons stretch too much when pulled?
Contain lots of collagen but little elastin - minimal waste of energy transfer
What are the functions of ligaments?
Ligaments connect bone to bone.
They support joints and prevent an excessive range of movement
Why is ligament healing compromised?
Relatively poor blood supply
What are ligaments composed of?
Dense regular bundles of connective tissue protected by dense irregular connective tissue sheaths
What do peri-articular (capsular) ligaments comprise of and what do they do? Give an example
Comprise of thickening of the capsule that surrounds synovial joints
Act as mechanical reinforcements
E.g. anterior and posterior cruciate ligaments of the knee
What is fascia and what is its function?
Fascia is sheets of connective tissue. One of the major functions of fascia is to envelop groups of muscles and divide body parts (e.g. the arm) into anatomical compartments. Some sheets of fascia are very tough (e.g. fascia lata in the thigh) and therefore also serve a protective function for the underlying structures.
What is superficial fascia?
loose connective tissue and fat underlying the skin - subcutaneous fatty layer
Also surrounds organs and glands and neurovascular bundles
What is the purpose of superficial fascia?
- storage of fat and water
- passageway for lymphatics, nerves and blood vessels
- protective padding for organs
What is deep fascia?
- Deep fascia is a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments.
- This fibrous connective tissue interpenetrates and surrounds the muscles, bones, nerves, and blood vessels of the body.
- Comprises of collagen bundles and elastin fibres orientated in a wavy pattern parallel to the direction of pull
- Flexible and able to resist great unidirectional forces
What is the purpose of articular/hyaline cartilage?
• the cartilage found on the ends of bones contributing to joints. It is very smooth and helps to create almost
frictionless motion at the joint
• shock-ansorber
What is the purpose of fibrocartilage?
• Fibrocartilage has a higher collagen content than hyaline cartilage.
• involved in shock absorption
• increase bony congruity at joints (congruity = creating a complementary shape of bony surfaces to improve stability).
• The menisci of the knee are made of
fibrocartilage
What is the purpose of the synovial membrane and where is it found?
- This tissue is found within joints, bursae and tendon sheaths.
- It produces synovial fluid which lubricates the joints.
- act as a shock absorber
- transport nutrients to (and remove waste from) the articular cartilage of the joint as articular cartilage is avascular and synovial joints are surrounded by a plexus of arteries so have a rich blood supply
What does synovial fluid contain?
hyaluronic acid and lubricin, proteinases and collagenases
What is the nature of synovial fluid?
Clear/pale yellow, viscous, slightly alkaline at rest
What are bursae?
- A bursa is a small sac lined by synovial membrane and containing a thin layer of synovial fluid.
- It provides a cushion between bones and tendons and/or muscles around a joint.
- This helps to reduce friction between the bones and allows free movement.
- They can either be communicating or non communicating with the joint cavity.
What are tendon sheaths?
Tendon sheaths are elongated bursae that wrap around a tendon and reduce the friction associated with movement of the tendon.
What is the major component that differentiates bone from other connective tissue?
The presence of calcium phosphate (CaPO4)/ hydroxyapatite which mineralises the extracellular matrix conferring rigidity into the bone
What are the two divisions of bone?
Bone is divided into cellular and non-cellular components
What are the cellular components of bone?
The cellular components of bone are predominantly osteocytes, osteoblasts and osteoclasts. There are also fibroblasts, macrophages, mast cells and adipocytes
within bone.
What does the ECM of the bone contain?
Fibres: collagen(mainly) and elastic(small amounts)
Ground substance: water, GAGs, PGs