Bone, Cartilage and Joints 1

M.8R, W.2, L.1

List the 3 main types of CT

• Embryonic CT

• Adult CT

• Special CT

List the subtypes of Adult CT

• Loose CT

• Dense CT

  • Dense Regular CT

  • Dense Irregular CT

• Reticular CT

• Elastic CT

List the 4 main types of Special CT and their subtypes

• Adipose tissue

  • White adipose tissue

  • Brown adipose tissue

• Cartilage

  • Hyaline Cartilage

  • Elastic Cartilage

  • Fibrocartilage

• Bone

  • Compact Bone

  • Woven bone (in developing bone)

  • Cancellous bone

• Bone Marrow

List the two main cells that make up the ECM of cartilage and their functions

• ChondroBLASTS

  • cell that is responsible for producing ECM

• ChrondroCYTES

  • maintenance of ground substances

Describe the ECM of cartilage

• Made up of:

  • fibers

  • ground substance

• Avascular

what do the fibers in the ECM of cartilage provide? what does the ground substance of the ECM of cartilage provide?

• Fibers: Rigidity

• Ground Substance: resiliency

List the 3 types of cartilage and list a histological characteristic of each

• Hyaline cartilage

  • clear looking ground substance

• Fibrocartilage

  • densely layered collagen fibers

  • more flattened and organized cell rows

• Elastic cartilage

  • visible elastic fibers in matrix

List the most common type of cartilage

Hyaline cartilage

What type of cartilage is present in embryo skeleton and what is it replaced by?

• Hyaline cartilage

• gradually replaced by bone

Define Hyaline cartilage (what it forms and what that enables, abundant in what, found in who, found in where, surrounded by what)

• forms epiphyseal growth plate

  • enables longitudinal growth of long bones via endochondral ossification

• abundant ground substance

  • rich in proteoglycans & fine Type II collagen fibrils

• found in adults at

  • articular surfaces

  • costal cartilages

  • respiratory passages

  • nasal cartilages

  • portions of the larynx

• surrounded by perichondrium

What does Hyaline Cartilage being surrounded by perichondrium enable?

Most hyaline cartilage is surrounded by perichondrium, except where?

• Enables

  • appositional growth

• Except

  • articular cartilage

  • growth plate cartilage

How does interstitial growth of hyaline cartilage occur?

through division of chondrocytes within cartilage matrix

Where is elastic cartilage found?

• auricle (pinna) of the ear

• epiglottis

• auditory (Eustachian) tube

List the components of Elastic Cartilage ECM.

What do these components provide?

• Components:

  • elastic fibers

  • type II collagen

• provides greater flexibility and resilience

List the two ways how elastic cartilage grows and explain how these work

• Appositional growth

  • addition at the surface via perichondrium

• Interstitial growth

  • expansion from within by chondrocyte proliferation

List the regions fibrocartilage is found in

Regions subjected to tensile and compressive forces:

• Intervertebral discs

• Intra-articular discs (menisci)

• Where ligaments and tendons attach to bones

Describe Fibrocartilage histologically (what is it made up of, what kind of connective tissue)

• Type 1 collagen (dense bundles)

• scattered chondrocytes in lacunae

• minimal ground substance

• lacks perichondrium

• intermediate between dense regular CT and hyaline cartilage

What kind of growth does fibrocartilage undergo and why?

interstitial growth

• bcus it lacks a perichondrium

Describe Appositional Growth (what kind of cartilage forms and where, types of cells involved and their function, where does this growth occur)

• new cartilage forms at surface of existing cartilage from perichondrium

• chondrogenic cells differentiate into chondroblasts and synthesize cartilage ECM

• chondrocytes maintain and remodel surrounding ECM

• occurs in elastic cartilage and most hyaline cartilage

Where does Appositional Growth not occur and why?

• Articular cartilage

• Growth plate cartilage

• lack of perichondrium

Describe Interstitial Growth (where does growth occur, what cells are involved and their function, what forms and their function, and where does this growth occur)

• growth occurs from within existing cartilage

• chondrocytes proliferate; form isogenous groups which synthesize additional ECM

• occurs in all types of cartilage

Describe Hyaline Cartilage (location, perichondrium?, describe the chondrocytes, describe ECM, type of collagen fibers)

Location

• costal cartilages, nose, larynx, trachea, bronchi, epiphyseal plates, articular cartilage

• most of fetal skeleton (until replaced by bones)

Perichondrium

• Present

Chondrocytes

• smaller compared to elastic cartilage

• arranged in isogenous groups (2-8 cells)

ECM

• Basophilic and homogenous

Collagen Fibers

• Type II

Describe Elastic Cartilage (location, perichondrium?, describe the chondrocytes, describe ECM, type of collagen fibers)

Location

• Auricle or pinna

• Epiglottis

• External auditory meatus

Perichondrium

• Present

Chondrocytes

• large

• closely placed

• isogenous groups (2-4 cells)

ECM

• Abundance of elastic fibers

Collagen Fibers

• Type II

Describe Fibrous Cartilage (location, perichondrium?, describe the chondrocytes, describe ECM, type of collagen fibers)

Location

• Intervertebral discs

• Pubic Symphysis

• Articular discs in sternoclavicular and temporomandibular joints

• Glenoidal mabrum and Acetabular labrum

Perichondrium

• NOT present

Chondrocytes

• small

• arranged in rows between bundles of collagen fibers

ECM

• Eosinophilic

• abundance of collagen fibers

Collagen Fibers

• Type I

Give an example of hyaline cartilage where only interstitial growth occurs

Articular cartilage and synovial joints

Define the Synovial Membrane / Synovium (what is it and what is it made up of)

• specialized type of CT

• made up of:

  • Type A Synoviocyte

  • Type B synoviocyte

Define Type A Synoviocyte (what are they and what is their function)

• Macrophage-like cell

• Responsible for:

  • maintenance and “clean up”

Define Type B Synoviocyte (what are they and what do they synthesize)

• Fibroblast-like cell

• Synthesizes:

  • hyaluronan and lubricin

Describe the sub-intima of the synovial membrane (what is it, what does it contain and the function of those structures)

• deeper, supportive layer of the synovial membrane; lines synovial joint

• contains blood vessels

  • provide nutrients to avascular intima

  • contribute to synovial fluid formation

Describe the composition of Synovial Fluid, what they are, and their functions

• Hyaluronan

  • glycosaminoglycan

  • contributes to fluid’s viscosity + lubricating properties

• Lubricin

  • glycoprotein

  • enhances lubrication

  • reduces friction in joint

• Electrolytes and Proteins

  • derived from plasma ultrafiltration

List and describe the functions of Synovial Fluid

• Lubrication

  • provided by hyaluronin and lubricin

  • reduces friction between articular cartilage during movement

    • bones can glide smoothly against eachother

• Shock Absorption

  • helps distribute loads and absorb mechanical forces across joint

• Nutrient Distribution

  • nutrients provided to avascular articular cartilage

  • removes waste products

    • maintains joint health

What is an Arthrocentesis and what is it used for?

• Joint tap

  • cytology, microbial culture, assessment of joint disease

Which cell type is primarily responsible for the formation of the ECM in cartilage?

Which type of cartilage leads to the formation of isogenous groups?

Which type of cartilage is found at articulating surfaces of bones?

• Chondroblasts

• Interstitial

• Hyaline cartilage

Define bone (what is bone, what kind of tissue, vascular or avascular, what cells maintain structure and function)

• cells and collagen fibers embedded in hard mineralized ECM

• dynamic tissue - continuously undergoes remodeling repair

• highly vascular

• structure and function maintained by osteoblasts, osteocytes, and osteoclasts

List the functions of bone

• rigid and hard support

• protects vital organs

• houses bone marrow 9site of hematopoiesis)

• reservoir (Calcium, phosphate, other ions)

• transforms forces of skeletal muscle contraction into bodily movements

Label A-G of the long bone with the correct terminology

Describe Compact / Cortical Bone (type of bone, structural organization, orientation of collagen)

• Lamellar bone

• Structural Organization:

  • Haversian systems or osteons

• specific orientation of collagen fibers

Describe Cancellous / Spongy / Trabecular Bone (type of bone, structural organization, function)

• Lamellar Bone

• Organization:

  • interconnected trabeculae

  • lacks Haversian systems

• reduces weight of bone and supports marrow

Describe Woven Bone (type of bone, orientation of collagen, how fast is this bone deposited, when is this bone seen, and what is this bone replaced by)

• Temporary / Immature bone

• random orientation of collagen fibers

• rapidly deposited bone during

  • development

  • fracture repair

  • some pathological conditions

• replaced by lamellar bone

List the 3 bone cell types

• Osteoblasts

• Osteocytes

• Osteoclasts

Describe Osteoblasts (where do they originate, function, what do they become, and why)

• Originate from osteoprogenitor (osteogenic) cells associated with the periosteum and endosteum​

• Function

  • form Osteoid (organic part of ECM)​

• Become osteocytes

  • when entrapped in the mineralised matrix​

Describe Osteocytes (where are they located, how they communicate, and function)

• Located

  • within lacunae in calcified bone ECM.

• Communicate

  • via cytoplasmic processes

    • extend through canaliculi​

• Function

  • maintain the bony matrix

Describe Osteoclasts (where are they found, describe the cells, list a histological characteristic, what are they derived from, and function)

• Found

  • on endosteal and periosteal bone surfaces ​

• Large, motile, multinucleated cells​

• Ruffled border​

• Derived:

  • from hematopoietic precursors

    • (of the monocyte macrophage linage​)

• Function

  • resorb mineralised bone matrix

    • during growth repair and remodelling

Label A-D in the photo

What do canaliculi contain and list their function

• Cytoplasmic processes

  • connect neighboring osteocytes

What does the Lacunar-canalicular system allow?

• communication between osteocytes + nutrient/waste exchange

• Mechanosensation

  • osteocytes able to:

    • detect mechanical stress

    • regulate bone remodelling

List the components of Bone Matrix (ECM)

• Osteoid (organic compound)

  • Fibers (collagen type I)

  • Glycoproteins

    • involved in mineralization and Ca2+ binding

• Inorganic components

  • hydroxyapatite crystals

  • small amts of minerals (sodium, magnesium)

What is the function of the organic and inorganic components of bone matrix (ECM)

• Organic Component

  • provides tensile strength

• Inorganic Component

  • provides hardness + compressive strength

Which cell type in bone is responsible for forming new bone?

Osteoblasts

What is the functional role of the lacunar-canalicular system in compact bone?

communication and nutrient/waste exchange