Connective Tissue Biomechanics and Tissue Response to Load

What dictates the function of biological tissue?

The biology of the tissue.

What are the two main components of connective tissue?

Cells and extracellular matrix.

What is the primary function of tendons?

To attach muscle to bone and transmit tensile loads from muscle to bone.

What is the primary function of ligaments?

To attach bone to bone and stabilize joints during motion.

What are the four primary tissue types?

Epithelial, muscular, nervous, and connective tissue.

What are the two components of the extracellular matrix?

Fibrillar component (fibers) and interfibrillar component (ground substance).

What types of fibers are found in connective tissue?

Collagen and elastin.

What is the role of glycosaminoglycans (GAGs) in connective tissue?

They attract water molecules and contribute to the properties of the extracellular matrix.

What type of collagen is primarily found in hyaline cartilage?

Type II collagen.

What are the main types of connective tissue?

Dense fibrous connective tissue, cartilage, and bone.

What is the stress-strain curve for tendons and ligaments?

It shows how these tissues respond to applied forces, primarily loaded in tension.

What happens when the ultimate tensile strength of tendons is surpassed?

Rupture occurs, leading to complete failure.

What is the function of hyaline cartilage?

To distribute compressive forces and minimize friction between joint surfaces.

What is the difference between compact bone and cancellous bone?

Compact bone is dense and forms the outer surface, while cancellous bone is spongy and found inside.

What is Wolff's Law?

Bone is laid down where needed and reabsorbed where it is not needed, influenced by the stresses and strains it experiences.

What are the mechanical properties of cartilage related to?

The composition, including the relative proportions of collagen and elastin.

What is the primary loading condition for cartilage?

Primarily loaded in compression.

What is the significance of the parallel alignment of collagen fibers in tendons?

It allows tendons to sustain predominantly tensile stresses in one direction.

What is the difference between the mechanical behavior of bone and cartilage?

Bone is primarily loaded in compression and has a high mineral content, while cartilage is primarily loaded in compression and has a high water content.

What is the role of fibroblasts in connective tissue?

They produce and maintain the extracellular matrix.

What is the primary function of skin?

To protect against physical damage.

How does the structure of ligaments contribute to their function?

They have a high collagen:elastin ratio and nearly parallel alignment of collagen fibers.

What is the effect of aging on the strength of ligaments compared to bone?

Children have greater strength in ligaments compared to bone.

What is the relationship between cartilage stiffness and permeability?

Cartilage stiffness is inversely related to permeability; healthy cartilage has low permeability.

What happens to cartilage during loading?

Fluid diffuses out of the matrix, creating a pressure differential.

What is the function of fibrocartilage?

To support and stabilize joints and absorb and dissipate forces.

What is the primary role of skeletal muscle?

To move our bones.

What are the three types of motion associated with skeletal muscles?

Speed, power, and endurance.

What is the function of skeletal stabilizers?

To control posture and contribute to joint stability.

What factors influence active force generation in muscles?

Muscle and fiber size, muscle architecture, fiber type, number of cross bridges, length-tension relationship, and force-velocity relationship.

What is the significance of muscle cross-sectional area?

It is directly related to maximal force potential.

What is the difference between anatomical and physiological cross-section?

Anatomical cross-section is perpendicular to the long dimension of the muscle, while physiological cross-section is perpendicular to the direction of muscle fibers.

What is a pennation angle?

The angle between muscle fibers and the tendon; greater angles result in less force per fiber transferred to the tendon.

What are the two architectural classifications of muscles?

Fusiform and pennate.

What characterizes fusiform muscles?

Long muscle fibers that run parallel to the tendon, built for motion with no pennation angle.

What characterizes pennate muscles?

Shorter fibers that run diagonally with respect to the tendon, providing greater physiological cross-section for increased tension development.

What is the length-tension relationship in muscles?

It describes how muscle force production depends on the length of the muscle and the active and passive components.

What are active structures in muscle force production?

Actin-myosin cross-bridges.

What is the role of passive structures in muscle?

They include connective tissue sheaths, extracellular structural proteins, and tendons, contributing to passive force generation.

What is active insufficiency?

When a muscle is shortened across one joint, resulting in decreased ability to generate force at another joint.

What is passive insufficiency?

When a muscle is lengthened across one joint, resulting in decreased range of motion at another joint.

What is the difference between prime mover (agonist) and antagonist muscles?

The prime mover is the muscle most directly involved in a joint motion, while the antagonist opposes that action.

What is a synergist muscle?

A muscle that assists another muscle in producing movement.

What are the three types of muscle contractions?

Concentric, eccentric, and isometric.

What occurs during a concentric contraction?

The muscle shortens as it generates force.

What occurs during an eccentric contraction?

The muscle lengthens while controlling the load.

What occurs during an isometric contraction?

The muscle length remains nearly constant while generating force.

What is the force-velocity relationship in muscles?

It describes how the velocity of muscle contraction is inversely related to the force produced.

What is muscle stiffness?

The resistance to lengthening through passive movement.

What are the four primary tissue types in the body?

Epithelial, muscular, nervous, and connective.

What are the components of connective tissue?

Fibrous proteins (like collagen and elastin), ground substance, and cells (such as chondroblasts, fibroblasts, and osteoblasts).

What are the two main types of collagen fibers?

Type I and Type II collagen

What is the primary function of collagen Type I?

Provides high tensile strength and contributes to stiffness.

What are examples of tissues that contain collagen Type I?

Ligaments, fibrous joint capsules, and tendons.

What is the primary example of collagen Type II?

Hyaline cartilage.

What is the function of elastin in connective tissue?

Provides high flexibility.

What factors influence the mechanical properties of connective tissue?

Composition, relative proportion of collagen and elastin, structural orientation of fibers, and intrinsic properties of fibers.

What are the main types of connective tissues?

Dense connective tissue, cartilage, and bone.

What are the functions of tendons?

Attach muscle to bone, transmit tensile loads, and produce joint motion.

What is the structural characteristic of tendons?

High collagen to elastin ratio with parallel alignment of collagen fibers.

What factors affect tendon stress?

Magnitude of force from muscle contraction and area of tendon relative to muscle.

What is the function of ligaments?

Attach bone to bone and stabilize joints during motion.

How do ligaments primarily sustain stress?

They are primarily loaded in tension.

What is the enthesis in relation to ligaments?

The site of attachment to bone where there is a gradual change from fibrous tissue to bone.

What are the functions of hyaline cartilage?

Distributes compressive forces and minimizes friction between joint surfaces.

What are the structural features of hyaline cartilage?

Contains Type II collagen, high Glycosaminoglycan concentration, is largely aneural and avascular.

What are the functions of fibrocartilage?

Support and stabilize joints, absorb and dissipate forces.

What is Wolff's Law in relation to bone?

Bone is laid down where needed and reabsorbed where it is not needed.

What is the primary function of bone?

Provides a structural framework and serves as a reservoir for calcium and phosphate.

What are the two types of bone?

Cortical bone and cancellous (spongy) bone.

What is the role of skin in the body?

Protects against physical damage, microbes, and acts as a barrier to water and chemicals.

How does injury risk vary with pressure and duration on skin?

High magnitudes of pressure are tolerated for a short duration, while low magnitudes are tolerated for longer.

What is the relationship between collagen concentration and tissue stiffness?

Higher collagen concentration results in stiffer tissue.

What are the functions of muscle?

Skeletal mover and stabilizer, controlling posture and contributing to joint stability.

What factors influence active force generation in muscle?

Muscle and fiber size, architecture, fiber type, number of cross bridges, and neural drive.

What is the relationship between cross-sectional area and force generation in muscles?

Maximal force generating potential is directly related to cross-sectional area; greater area leads to greater force.

What is the difference between anatomical and physiological cross-section in muscles?

Anatomical cross-section is perpendicular to the muscle's long dimension, while physiological cross-section is perpendicular to the direction of muscle fibers.

What is the pennation angle?

The angle between the muscle fibers and the tendon.

What happens to force transfer as the pennation angle increases?

The greater the angle, the less force per muscle fiber is transferred to the tendon.

What characterizes fusiform muscle architecture?

Long muscle fibers run parallel to the tendon, with no pennation angle.

What is the physiological cross-sectional area (PCSA) of fusiform muscles compared to anatomical cross-sectional area?

They are equal.

What is the primary advantage of fusiform muscles?

They are built for motion over stability and have a greater ability to change length.

What is the characteristic of pennate muscle architecture?

Fibers run diagonally to the tendon, resulting in a greater physiological cross-section.

What is the result of having more fibers packed into a muscle volume in pennate muscles?

They can develop greater tension but have a limited range of lengthening/shortening.

What are the active components of the length-tension relationship in muscles?

Myofilaments, specifically actin and myosin.

What are the passive components of the length-tension relationship?

Connective tissues (epi-, peri-, endomysium), extracellular structural proteins, tendons, and the titin structure.

What happens to passive force generation as muscle length increases?

It increases due to stored elastic energy.

What is a prime mover or agonist?

The muscle most directly related to the initiation and execution of a joint motion.

What is a synergist?

Muscles that work together to produce a movement.

What is a force-couple?

Two or more muscles producing force in different linear directions but the same rotational direction.

What is relative flexibility/stiffness?

Resistance to lengthening through the range of motion in the absence of active contraction.

What is the basic premise of the Physical Stress Theory?

Changes in the relative level of physical stress cause a predictable adaptive response in all biological tissues.

What happens when physical stress levels are below the maintenance range?

There is decreased tolerance of tissues to subsequent stress.

What is the response when physical stress levels are in the maintenance range?

There is no apparent tissue change, maintaining tissue homeostasis.

What is the impact of increased physiological cross-sectional area (PCSA) on passive stiffness?

Increased PCSA leads to increased passive stiffness.

What is the significance of two-joint muscles?

Contraction affects both joints simultaneously, leading to active and passive insufficiency.

What is the relationship between muscle architecture and force generation?

Muscle architecture influences the ability to generate force and the range of motion.

What is the role of neural drive in muscle function?

Neural drive affects the number of cross bridges formed, impacting force generation.

What is the maintenance range in physical stress?

The maintenance range is the level of physical stress that tissues can tolerate without injury.

How can the maintenance stress range differ among individuals?

It can differ based on individual fitness levels, age, and physiological conditions.