MIDTERM LEC 2: BONE AND CARTILAGE Flashcards
● Part of/surrounded by connective tissue
● Tough, durable form of supporting
connective tissue, characterized by its
extracellular matrix (ECM)
● Lacks nerves
CARTILAGE
CARTILAGE ORIGNATED FROM?
EMBRYONIC MESENCHYME
ECM of cartilage:
➢ Has high concentrations of ___and __________, interacting with collagen and elastic fibers
GAGs, proteoglycans
- is a SHEATH OF DENSE CONNECTIVE TISSUES that surrounds cartilage in most places
- forming an interface between the cartilage and the tissues supported by the cartilage
- HARBORS THE BLOOD SUPPLY serving the cartilage and a small neural component
PERICHONDRIUM
THE PHYSICAL PROPERTIES OF CARTILAGE DEPEND ON ELECTROSTATIC BONDS BETWEEN:
● ECM TYPE II COLLAGEN
● HYALURONAN/ HYALURONATE/ HYALURONIC ACID
- COVERS THE ENDS OF BONE in
movable joints - erodes in the course of arthritic
degeneration, - LACKS PERICHONDRIUM and is
sustained by the diffusion of
oxygen and nutrients from the
synovial fluid
ARTICULAR CARTILAGE
● (Gr. chondros, cartilage + kytos, cell)
● Cartilage cells
● Cells of the cartilage embedded in the
ECM which unlike connective tissue
proper contains no other cell types
SYNTHESIZE ANDMANTAIN ALL ECM COMPONENTS
● Exhibit LOW METABOLIC ACTIVITY
● Location: cavities (LACUNAE)
CHONDROCYTE
- HYALOS: glass; glassy appearance,
bluish - MOST COMMON TYPE OF CARTILAGE
● Fresh state: HOMOGENOUS and
SEMI TRANSPARENT
● Location in adult:
1. Articular surfaces of movable joints
2. Walls of larger respiratory
passages - (nose, larynx, trachea,
bronchi)
3. Ventral ends of ribs - where they articulate with the sternum, and
4. Epiphyseal plates of long
bones - where it makes possible longitudinal bone growth
HYALINE CARTILAGE
hyaline cartilage that forms the temporary skeleton and later on replaced by bones
EMBRYO
● Nearly 40% collagen (mostly type II)
● Embedded in a firm, hydrated gel of
proteoglycans and structural
glycoproteins
ECM OF HYALINE CARTILAGE
make the matrix generally BASOPHILIC (negative) and the thin collagen fibrils are barely discernible.
PROTEOGLYCANS
- MOST ABUNDANT PROTEOGLYCAN OF HYALINE CARTILAGE
- bound noncovalently by link proteins to long polymers of hyaluronan
AGGRECAN
- a form of structural MULTIADHESIVE GLYCOPROTEIN
- Binds specifically to GAGs, collagen, and integrins, mediating the adherence of chondrocytes to the ECM.
CHONDRONECTIN
CHONDROCYTES OF HYALINE CARTILAGE
● Chondrocytes respire under________
tension because cartilage matrix is
AVASCULAR
LOW - OXYGEN
Cell metabolism: Glucose metabolized
mainly by
ANAEROBIC GLYCOLYSIS
young chondrocytes that has an elliptic
shape, with the long axes parallel to the
surface; may appear in groups of up to
eight cells that originate from mitotic
divisions of a single chondroblast and
are called ISOGENOUS AGGREGATES
CHONDROBLAST
most collagen in hyaline cartilage
TYPE II COLLAGEN
metabolize glucose
ANAEROBIC GLYCOLYSIS
DRY WEIGHT OF HYALINE CARTILAGE (40% collagen embedded in firm, hydrated gel of proteoglycans and structural glycoproteins)
MATRIX
- elliptic shape, with long axes parallel to the surface
- Round and may appear in groups of up to 8 cells (Isogenous aggrefates)
- Secretes collagen and other ECM
components
CHONDROBLAST
- a PITUITARY -DERIVED protein
- major regulator of hyaline cartilage growth
- acts INDIRECTLY, promoting the
endocrine release from the liver
of insulin-like growth factors,
or somatomedins, which directly
stimulate the cells of hyaline
cartilage
SOMATOTROPHIN
- Source of nutrients
- Dense connective tissue
- Essential for growth and maintenance of cartilage
PERICHONDRIUM
OUTER REGION OF PERICHONDRIUM is consists largely of collagen ______ fibers and ____
TYPE I, FIBROBLASTS
OUTER REGION OF PERICHONDRIUM contains ________ which provide a SOURCE FOR A NEW CHONDROBLASTS hat divide and differentiate into chondrocytes
MESENCHYMAL STEM CELLS
- Flexible due to abundant network of
elastic fibers - Contains an abundant network of ELASTIC FIBERS and COLLAGEN TYPE II FIBRILS which gives fresh elastic cartilage a YELLOW COLOR
- MORE FLEXIBLE than hyaline
- Found in the auricle of the ear, walls of the external auditory canals, auditory
(Eustachian) tube, epiglottis, and upper respiratory tract - Has perichondrium
- Cells are the same with hyaline cartilage
ELASTIC CARTILAGE
- MINGLING OF HYALINE CARTILAGE and dense connective tissue
- Hyaline cartilage + dense CT
- Found in intervertebral discs,
attachment of certain ligaments, and in pubic symphysis - All place where it serves as VERY TOUGH, YET CUSHIONING SUPPORT tissue for bone
FIBROCARTILAGE
occur single and often in aligned isogenous aggregates producing
type II collagen and other ECM components
CHONDROCYTES
- Areas with chondrocytes and hyaline
matrix are SEPARATED by other regions
with FIBROBLASTS and dense BUNDLES OF TYPE I COLLAGEN which confer extra tensile strength to this tissue
● Proteoglycans: Its scarcity makes
fibrocartilage matrix more ACIDOPHILIC
● Relatively lacks proteoglycans - perichondrium: ABSENT
ECM SPARSE
- scarcity of proteoglycans
- NO DISCTINCT PERICHONDRIUM
ACIDOPHILIC
- FIBROCARTILAGE ACT AS LUBRICATED CUSHIONS and shock absorbers preventing damage to adjacent vertebrae from abrasive forces of impacts
INTERVERTEBRAL DISCS OF SPINAL
COLUMN
- FORMATION OF CARTILAGE
- Embryonic cartilage formation
(mesenchyme) - Rounding up mesenchymal cell: first indication of cell differentiation
- Mesenchymal cell → chondroblasts → chondrocyte → ECM → cartilage
- Superficial mesenchyme develops as the perichondrium
CHONDROGENESIS
CARTILAGE GROWTH
- divide by chondrocytes; mitosis of chondrocytes
- Involving mitotic division of pre-existing chondrocyte
- WITHIN LONG BONES: it is important in increasing the length of these structures
INTERSTITIAL GROWTH
CARTILAGE GROWTH
- Involves chondroblast differentiation from progenitor cells in the
perichondrium
- More important during POSTNATAL DEVELOPMENT
APPOSITIONAL GROWTH
CARTILAGE REPAIR/REGENERATION IS?
slow or doesn’t heal; low metabolic rate
Cartilage repair primarily dependent on
cells in the __________ which invade the injured area and produce new cartilage
perichondrium
● GRADUAL LOSS/CHANGED physical properties of the HYALINE CARTILAGE that lines the articular ends of bones in joints (prone to cartilage degeneration)
● Bone tends to crash (friction)
- Cartilage loss (hyaline)
- Joint space narrowing
- Bone spurs
- Case friction between 2 bones
OSTEOARTHRITIS (OA
TUMORS:
- (capsulated to prevent spread) arising from cells of cartilage (BENIGN TUMOR)
CHONDROMA
slow growing; seldom metastasize and
are generally removed surgically
(MALIGNANT TUMOR)
CHONDROSARCOMA
Due to MUTATION IN FBN1 GENE, which encodes fibrillin-1
- protein that plays a crucial role in the
formation of elastic fibers within the connective tissue
● Abnormalities include skeletal, cardiovascular, ocular, pulmonary,
dural ectasia (covering of the spinal cord)
MARFAN SYNDROME
● Specialized CT composed of calcified ECM (bone matrix)
● MAIN CONSTITUENT OF THE ADULT SKELETON
- Provides solid support for the body
- Protects vital organs such as those in the cranial and thoracic cavities, and encloses internal (medullary) cavities containing bone marrow where blood cells are formed
- Reservoir for calcium, phosphate, and other ions
3 MAJOR CELL TYPES: OSTEOCYTE, OSTEOBLASTS, OSTEOCLASTS
BONE (OSSEOUS) TISSUE
- formation of blood cell
HEMATOPOIESIS
2 SPECIALIZED BONE TISSUE
(connective tissue covering)
● Layer of dense connective tissue on the outer (external) surface of the bone
● bound to bone matrix by bundles
of type I collagen called Perforating (Sharpey’s) fibers, that secures the periosteum
● Rich in osteoprogenitor cells & osteoblast that mediate much bone growth and remodeling
PERIOSTEUM (OUTER)
● Thin layer of active/inactive osteoblast, which LINES ALL THE INTERNAL SURFACES WITHIN BONE
● Osteoblast here also required for
bone growth
ENDOSTEUM (INNER)
origin of OSTEOBLASTS
OSTEOPROGENITOR CELL
BONE TISSUE SECTIONING
● Bone matrix is usually softened by immersion in a ___________before paraffin embedding/embedded in plastic after fixation & sectioned within specialized microtome
decalcifying solution
UNIT OF BONE (MATRIX RINGS)
OSTEON (HAVERSIAN SYSTEM)
● OPENING in the CENTER OF AN OSTEON, carrying blood vessels and nerves to all areas of the bone.
● run lengthwise through the bony
matrix
CENTRAL (HAVERSIAN) CANALS
● Canal perpendicular (90*) to the central canal
PERFORATING (VOLKMANN’S) CANAL
● TINY CAVITY, containing osteocyte
(mature bone cells) , arranged in
concentric rings
LACUNAE
● containing arranged lacunae
● Rings around central (Haversian)
canals of lacunae
LAMELLAE
● Tiny canals that radiate outward from
the central canals to all lacunae
● GIVES OSTEON A TINY CRACK APPEARANCE
CANALICULI
3 TYPES OF BONE CELLS
● BONE - FORMING CELLS
● Origin: mesenchymal stem cell
● SYNTHESIZE AND SECRETE THE ORGANIC COMPONENTS OF BONE MATRIX: type I collagen fibers, proteoglycans, and matricellular glycoproteins (osteonectin).
● Location: surfaces of the bone matrix, bound by integrins, typically forming a single layer of cuboidal cells joined by adherent and gap junctions
● Secretes non-collagen protein
(osteocalcin)
OSTEOCALCIN: for bone
metabolism
OSTEOBLASTS (build)
- LAYER OF UNIQUE COLLAGEN rich material between the osteoblast layer and the preexisting bone surface
- Involves in the MINERALIZATION OF MATRIX
OSTEOID
(osteon: bone + kytos: cell)
● mature bone cell
● MOST ABUNDANT CELL in the bone
- Found in cavities (lacunae) between bone matrix layers (lamellae) with cytoplasmic processes in small canaliculi (L.canalis, canal) that extend into the matrix
● Express many different proteins, including factors with PARACRINE and ENDOCRINE effects that HELP REGULATE BONE REMODELLING
● Communicate with one another
and ultimately with nearby
osteoblasts and bone lining cells
via GAP JUNCTIONS
OSTEOCYTES
-(blastos: germ)
- Growing cells which synthesize and
secrete the organic components of the matrix
OSTEOBLAST
● giant among the 3 types;
development rely on osteoblasts (klastos: broken)
● (osteon + Gr. klastos, broken), which are giant, motile, multinucleated cells involved in REMOVING CALCIFIED BONE MATRIX and REMODELLING bone tissue
● SECRETES ENZYMES AND ACIDS that dissolved the mineralized matrix, releasing calcium & phosphate ions
● Location: lie within the enzymatically etched depressions or cavities in the matrix known as resorption lacunae (or Howship lacunae)
● Development: requires 2 polypeptides produced by osteoblasts
1. Macrophage-Colony-Stimulating Factor (M-CSF)
2. Receptor Activator of Nuclear factor-κB Ligand (RANKL)
OSTEOCLAST
a layer of unique collagen-rich material between osteoblast layer and the pre-existing bone surface
OSTEOID
a vitamin K-dependnet polypeptide, prominent among the noncollagen proteins secreted by osteoblasts
OSTEOCALCIN
- release membrane-enclosed by osteoblast rich in alkaline phosphatase and other enzymes which raises the local concentration of PO4 3− ions
- SERVE AS FOCI for the formation of
hydroxyapatite crystals, the first visible step in calcification
MATRIX VESICLES
- Most abundant in bone
- Enclosed singly within the lacunae spaced throughout the mineralized matrix
OSTEOCYTES
- where diffusion of metabolites between osteocytes and blood vessels occurs
- Communicates via GAP JUNCTIONS which allows osteocytes to serve s
mechnosensors
CANNALICULI
- DETECTS MECHANICAL LOAD on the bone as well as
stress-or fatigue-induced micro-
damage and trigger remedial activity
in osteoblasts and osteoclasts - Has less RER, smaller Golgi complexes, and more condensed nuclear chromatin than osteoblast
- Maintain the calcified matrix and their death is followed by rapid matrix resorption
MECHANOSENSORS
paracrine and endocrine
that helps regulate bone remodeling
PROTEINS
- BINDS THE CELL TIGHTLY TO THE BONE MATRIX and surrounds an area with
many surface projection called
“ruffled border” - allows the formation of a
specialized microenvironment
between the osteoclast and matrix
in which bone resorption occurs
SEALING ZONE
BONE MATRIX
- ____ INORGANIC MATERIALS
50%
Flat bones that form the calvaria
(skullcap) have two layers of compact
bone
PLATES
a thicker layer of cancellous bone that
separates the plates
DIPLOE
organized most bone in adults compact or
cancellous bones
- characterized by multiple layers or
lamellae calcified matrix (3-7 um thick)
LAMELLAR BONE
- Occurs continuously thoughout life
- In compact bone, remodeling resorbs
parts of old osteons and produce new
ones - In healthy adults, 5%-10% of the bone
turns over annually
BONE REMODELING
- Where most flat bones begin to form
- osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
- Most bones of the skull and jaws, as well as the scapula and clavicle, are formed embryonically by intramembranous ossification
INTRAMEMBRANOUS OSSIFICATION
2 TYPES OF BONE
● Dense bone immediately beneath, periosteum
● Represents 80% of the total bone mass
COMPACT (CORTICAL BONE)
2 TYPES OF BONE
● A.K.A: Spongy bone/Diploe
(makapal) - has porous
● Inner region/deeper areas with
numerous interconnecting cavities
● Constitutes 20% of the total bone
mass
CANCELLOUS (TRABECULAR) BONE
- Body of long bone
- medullary cavity; bone marrow located
DIAPHYSIS
- Ends of the long bone
- cancellous covered by compact bone
EPIPHYSIS
2 types of organization that both compact and cancellous bones typically show:
● A.K.A: IMMATURE BONE primary bone; bundle bone
● Non Lamellar, random disposition of type I collagen fibers & 1st bone tissue to appear in an embryonic development & in fracture repair
● Usually temporary & replaced in adults by lamellar bone lower mineral content and a higher proportion of osteocytes than mature lamellar bone
● Location: Developing and growing bones; hard callus of bone fractures
WOVEN BONE
● A.KA: MATURE BONE; secondary bone
● Has matrix existing as DISCRETE SHEETS
● Multiple layers (lamellae) of calcified matrix
● Alternating organization of collagen fibers in lamellae add greatly to strength
● Remodeled from woven bone
● Location: adults bone
● Canals communicate with one another through transverse perforating (Volkmann) canal
LAMELLAR BONE
outer boundary of each osteon
CEMENT LINE
numerous irregularly shaped of parallel
lamellae; scattered among intact osteons
Interstitial lamellae
● Have cores of cancellous bone
surrounded by compact bone.
● Example: wrist and ankle
SHORT BONES
● EPIPHYSIS
- Bulbous ends
- Composed of cancellous bone
(spongy) covered by a thin layer
of compact bone
● DIAPHYSIS
- Cylindrical part
- Body of long bone
- Almost totally dense compact
bone, with a thin region of
cancellous bone on the inner
surface around the central
marrow cavity
- Start of first bone formation
● MEDULLARY CAVITY: contains bone
marrow
LONG BONE
● Have 2 layers of compact bones (plates),
separated by a thick layer of cancellous
bone (diploe)
● Example: calvaria (skullcap)
FLAT BONES
BONE DEVELOPMENT/OSTEOGENESIS
● Osteoblast differentiate DIRECTLY
from mesenchyme & begin secreting osteoid
● Forms most flat bone (skull, jaws, scapula
INTRAMEMBRANOUS OSSIFICATION
● Pre-existing matrix of hyaline cartilage is eroded & invaded by osteoblasts, which then begin osteoid production
● Forms most bones of the body
ENDOCHONDRAL OSSIFICATION
GROWTH
- Increase the circumference of a
bone by osteoblast activity at the
periosteum & is accompanied by
enlargement of the medullary
marrow cavity
APPOSITIONAL BONE GROWTH
A region of cartilage located at the epiphyses of long bones & is responsible for the increase in the bone length unit skeletal maturity
EPIPHYSEAL PLATE
- composed of typical hyaline cartilage
ZONE OF REVERSE (resting) cartilage
- Cartilage cells divide repeatedly,
enlarge, & secrete more type II
collagen & proteoglycans &
become ORGANIZED INTO COLUMNS
PROLIFERATIVE ZONE: (cell division
of chondrocytes)
- most MATURE CHONDROCYTES in these lacunae SWELL UP, compress the matrix & undergo apoptosis
ZONE OF HYPERTROPHY: (increase in size of chondrocytes)
- Bone tissue first appears
- osteoprogenitor cells differentiate into osteoblasts leading to bone tissue formation (ossification)
ZONE OF OSSIFICATION: (bone formalin takes place; cartilage replaced by bone)
● Growth of bones occurs throughout life, with cells & matrix turning over
continuously through activities of
osteoblasts & osteoclast
- Very active in young children
(200x faster than that of adults)
BONE REMODELING AND REPAIR
➢ By degrading bone, calcium will go back to blood
➢ Continuous process involving the
removal of old/damaged bone tissue &
formation of new bone tissue
➢ Bones change size & shape according to changes in mechanical stress
➢ Key cells: osteoclasts & osteoblasts
➢ OSTEOCLASTS - remove damage bone tissue
➢ OSTEOBLASTS - form/relapse new bone tissue
BONE REMODELING
_________-disrupt blood vessels, causing
bone cells near the break to die
BONE FRACTURES
The damaged blood vessels produce a localized hemorrhage or __________
hematoma
bubble bone for repair
FIBROCARTILAGE
bone removes tissue
RESORPTION
_________required for the activity of many enzymes and many proteins mediating cell adhesion, cytoskeletal movements, exocytosis, membrane
permeability, and other cellular functions.
Calcium ions
Skeleton serves as the ____________, containing 99% of the body’s total calcium in hydroxyapatite crystals
calcium reservoir
The concentration of calcium in the blood ? and tissues is generally quite stable because of a continuous interchange between blood calcium and bone calcium
(9-10 mg/dL)
The principal mechanism for raising blood calcium levels is the mobilization of ions from _____________ TO ____________, primarily in the cancellous bone.
hydroxyapatite to interstitial fluid
Ca2+ mobilization is regulated mainly by
____________ among bone cells
paracrine interactions
2 polypeptide hormones that target bone cells
to influence calcium homeostasis:
PTH & CALCITONIN
- From the parathyroid glands
- RAISES LOW BLOOD CALCIUM LEVELS by stimulating/ activating osteoclasts and osteocytes to resorb/ regrade bone matrix and release Ca2+ in the blood
PARATHYROID HORMONE (PTH)
- Produced within the thyroid gland
- REDUCE/DECREASE BLOOD CALCIUM LEVELS by opposing the effects of PTH in bone.
- This hormone directly targets osteoclasts to slow matrix resorption and bone turnover
CALCITONIN
● Cancer of the bone
● Arise in osteoprogenitor cell
● Sunburst appearance
OSTEOSARCOMA
● Genetic disease characterized by dense heavy bone (“MARBLE BONES”)
● Osteoclast lacks raffled borders & bone resorption is lacking
● Mutation in genes for the osteoclasts’ proton-ATPase pumps/chloride channels
● Overgrowth & thickening of bones
OSTEOPETROSIS
● Imbalance in skeletal turnover so that bone resorption exceeds bone formation
● Leads to Ca2+ loss from bones & reduce bone mineral density (BMR)
● Common: immobilized patients & in POSTMENOPAUSAL WOMEN
A. OSTEOPOROSIS
B. RICKETS
C. OSTEITIS FIBROSA CYSTICA
D. OSTEOPETROSIS
OSTEOPOROSIS
● In children: primarily due to a DEFICIENCY OF VITAMIN D or problem with its absorption → mineralization of bone tissue is impaired → soft
RICKETS
DEFICIENCY OF VITAMIN D in adults
A. OSTEOPOROSIS
B. OSTEOGENESIS IMPERFECTA
C. OSTEITIS FIBROSA CYSTICA
D. OSTEOMALACIA
OSTEOMALACIA
● INCREASED OSTEOCLAST ACTIVITY results in removal of bone matrix and fibrous degeneration
● Severe & rare manifestation of hyperparathyroidism → increased PTH → increased bone resorption
A. OSTEOPOROSIS
B. OSTEOGENESIS IMPERFECTA
C. OSTEITIS FIBROSA CYSTICA
D. OSTEOMALACIA
OSTEITIS FIBROSA CYSTICA
● A.K.A: “ Brittle bone disease”
● Group of related congenital disorders
● Osteoblasts produce deficient amount of type I
collagen/defective type I collagen due to genetic
mutations
● Significant fragility of the bones
A. OSTEOPOROSIS
B. OSTEOGENESIS IMPERFECTA
C. OSTEITIS FIBROSA CYSTICA
D. OSTEOMALACIA
OSTEOGENESIS IMPERFECTA
● Lack of growth hormone during the growing years
PITUITARY DWARFISM
● excess of growth hormone causes excessive growth of the long bones
GIGANTISM
A disease in which the bones (long become very thick.
ACROMEGALY
● chronic inflammation of the synovial membrane
● causes thickening of connective tissue and stimulates macrophages to release collagenases and other hydrolytic enzymes → . Destruction of articular cartilage
A. GOUTY ARTHRITIS
B. RHEUMATOID ARTHRITIS
C. OSTEOARTHRITIS
- high concentration of URIC ACID CRYSTAL in blood
A. GOUTY ARTHRITIS
B. RHEUMATOID ARTHRITIS
C. OSTEOARTHRITIS
GOUTY ARTHRITIS
● Regions where adjacent bones are capped and held together firmly by other connective tissues.
● Places where bones meet, or articulate, allowing at least the potential for bending or movement in that portion of the skeleton.
● Classified as SYNARTHROSES (no movement) & DIARTHROSES (free mobile)
JOINTS
● Allow very limited or no movement
● Subdivided into fibrous and cartilaginous joints, depending on the type of tissue joining the bones.
SYNARTHROSES JOINTS
● Involve bones linked to other bones and allow essentially no movement.
● Older adults: unite the skull bones, which in children
● Young adults: held together by SUTURES, or thin layers of dense connective tissue with osteogenic cells.
A. SYMPHYSES
B. SYNOSTOSES
C. SYNDESMOSIS
SYNOSTOSES
● Join bones by DENSE CONNECTIVE TISSUE ONLY
● Examples include the interosseous ligament of the
inferior tibiofibular joint and the posterior region of the sacroiliac joints
A. SYMPHYSES
B. SYNOSTOSES
C. SYNDESMOSIS
SYNDESMOSIS
- Have a THICK PAD OF FIBROCARTILAGE between the thin articular cartilage covering the ends of the bones.
● Such as the intervertebral discs and pubic symphysis, occur in the midline of the body.
A. SYMPHYSES
B. SYNOSTOSES
C. SYNDESMOSIS
SYMPHYSES
● LARGE SYMPHASES between the articular surfaces of successive bony vertebral bodies.
● Held in place by ligaments
● Discoid components of the intervertebral joints cushion the bones and facilitate limited movements of the vertebral column
A. NUCLEUS PULPOSUS
B. INTERVERTEBRAL DISC
C. ANNULUS FIBROSUS
INTERVERTEBRAL DISC
● Outer portion of each intervertebral disc
● Consisting of concentric fibrocartilage laminae in which collagen bundles are arranged orthogonally in adjacent layers.
● Multiple lamellae of fibrocartilage produce a disc with unusual toughness able to withstand pressures and torsion generated within the vertebral column.
A. NUCLEUS PULPOSUS
B. INTERVERTEBRAL DISC
C. ANNULUS FIBROSUS
ANNULUS FIBROSUS
● Gel-like body, found in the center of annulus fibrosus
● In children: large, but these structures gradually become smaller with age and are partially replaced by fibrocartilage.
● Allows each disc to function as a shock absorber
● Consists of a viscous fluid matrix rich in hyaluronan and type II collagen fibers, but also contains scattered, vacuolated cells derived from the embryonic notochord, the only cells of that structure to persist postnatally
A. NUCLEUS PULPOSUS
B. INTERVERTEBRAL DISC
C. ANNULUS FIBROSUS
NUCLEUS PULPOSUS
● PERMIT FREE BONE MOVEMENT
● Generally unite long bones and allow great mobility such as in the elbow and knee.
● In a diarthrosis ligaments and a capsule of dense connective tissue maintain proper alignment of bones.
- Capsule encloses a sealed joint cavity containing a synovial fluid (clear, viscous liquid)
- joint cavity is lined, not by epithelium, but by a synovial membrane
DIARTHROSES JOINTS
● Specialized connective tissue
● Extends folds and villi into the joint cavity and produces the lubricant synovial fluid.
● May have prominent regions with dense connective tissue or fat.
● Superficial regions: - well vascularized, with many porous (fenestrated) capillaries.
- characterized by 2 specialized cells with distinctly different functions and origins
SYNOVIAL MEMBRANE
2 SPECIALIZED CELL IN THE SUPERFICIAL REGION OF SYNOVIAL MEMBRANE
● Type A cells
● Derived from blood monocytes and remove wear-and-tear debris from the synovial fluid.
● Modified macrophages, which represent approximately 25% of the cells lining the synovium,
● Important in regulating inflammatory events within diarthrotic joints.
MACROPHAGE-LIKE SYNOVIAL CELLS
2 SPECIALIZED CELL IN THE SUPERFICIAL REGION OF SYNOVIAL MEMBRANE
● Type B cells
● PRODUCE ABUNDANT HYALURONAN and smaller amounts of proteoglycans.
● Transported by water from the capillaries into the joint cavity to form the synovial fluid, which lubricates the joint, reducing friction on all internal surfaces, and supplies nutrients and oxygen to the articular cartilage.
FIBROBLASTIC SYNOVIAL CELLS
● COLLAGEN LOSS or other degenerative changes in the annulus fibrosus are often accompanied by displacement of the nucleus pulposus
SLIPPED / HERNIATED DISC
