MIDTERM LEC 2: BONE AND CARTILAGE Flashcards

1
Q

● Part of/surrounded by connective tissue
● Tough, durable form of supporting
connective tissue, characterized by its
extracellular matrix (ECM)
● Lacks nerves

A

CARTILAGE

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2
Q

CARTILAGE ORIGNATED FROM?

A

EMBRYONIC MESENCHYME

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3
Q

ECM of cartilage:
➢ Has high concentrations of ___and __________, interacting with collagen and elastic fibers

A

GAGs, proteoglycans

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4
Q
  • 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
A

PERICHONDRIUM

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5
Q

THE PHYSICAL PROPERTIES OF CARTILAGE DEPEND ON ELECTROSTATIC BONDS BETWEEN:

A

● ECM TYPE II COLLAGEN
● HYALURONAN/ HYALURONATE/ HYALURONIC ACID

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6
Q
  • 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
A

ARTICULAR CARTILAGE

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7
Q

● (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)

A

CHONDROCYTE

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8
Q
  • 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
A

HYALINE CARTILAGE

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9
Q

hyaline cartilage that forms the temporary skeleton and later on replaced by bones

A

EMBRYO

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10
Q

● Nearly 40% collagen (mostly type II)
● Embedded in a firm, hydrated gel of
proteoglycans and structural
glycoproteins

A

ECM OF HYALINE CARTILAGE

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11
Q

make the matrix generally BASOPHILIC (negative) and the thin collagen fibrils are barely discernible.

A

PROTEOGLYCANS

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12
Q
  • MOST ABUNDANT PROTEOGLYCAN OF HYALINE CARTILAGE
  • bound noncovalently by link proteins to long polymers of hyaluronan
A

AGGRECAN

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13
Q
  • a form of structural MULTIADHESIVE GLYCOPROTEIN
  • Binds specifically to GAGs, collagen, and integrins, mediating the adherence of chondrocytes to the ECM.
A

CHONDRONECTIN

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14
Q

CHONDROCYTES OF HYALINE CARTILAGE
● Chondrocytes respire under________
tension because cartilage matrix is
AVASCULAR

A

LOW - OXYGEN

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15
Q

Cell metabolism: Glucose metabolized
mainly by

A

ANAEROBIC GLYCOLYSIS

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16
Q

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

A

CHONDROBLAST

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17
Q

most collagen in hyaline cartilage

A

TYPE II COLLAGEN

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18
Q

metabolize glucose

A

ANAEROBIC GLYCOLYSIS

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19
Q

DRY WEIGHT OF HYALINE CARTILAGE (40% collagen embedded in firm, hydrated gel of proteoglycans and structural glycoproteins)

A

MATRIX

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20
Q
  • 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
A

CHONDROBLAST

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21
Q
  • 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
A

SOMATOTROPHIN

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22
Q
  • Source of nutrients
  • Dense connective tissue
  • Essential for growth and maintenance of cartilage
A

PERICHONDRIUM

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23
Q

OUTER REGION OF PERICHONDRIUM is consists largely of collagen ______ fibers and ____

A

TYPE I, FIBROBLASTS

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24
Q

OUTER REGION OF PERICHONDRIUM contains ________ which provide a SOURCE FOR A NEW CHONDROBLASTS hat divide and differentiate into chondrocytes

A

MESENCHYMAL STEM CELLS

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25
- 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
26
- 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
27
occur single and often in aligned isogenous aggregates producing type II collagen and other ECM components
CHONDROCYTES
28
- 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
29
- scarcity of proteoglycans - NO DISCTINCT PERICHONDRIUM
ACIDOPHILIC
30
- FIBROCARTILAGE ACT AS LUBRICATED CUSHIONS and shock absorbers preventing damage to adjacent vertebrae from abrasive forces of impacts
INTERVERTEBRAL DISCS OF SPINAL COLUMN
31
- 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
32
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
33
CARTILAGE GROWTH - Involves chondroblast differentiation from progenitor cells in the perichondrium - More important during POSTNATAL DEVELOPMENT
APPOSITIONAL GROWTH
34
CARTILAGE REPAIR/REGENERATION IS?
slow or doesn’t heal; low metabolic rate
35
Cartilage repair primarily dependent on cells in the __________ which invade the injured area and produce new cartilage
perichondrium
36
● 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
37
TUMORS: - (capsulated to prevent spread) arising from cells of cartilage (BENIGN TUMOR)
CHONDROMA
38
slow growing; seldom metastasize and are generally removed surgically (MALIGNANT TUMOR)
CHONDROSARCOMA
39
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
40
● 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
41
- formation of blood cell
HEMATOPOIESIS
42
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)
43
● Thin layer of active/inactive osteoblast, which LINES ALL THE INTERNAL SURFACES WITHIN BONE ● Osteoblast here also required for bone growth
ENDOSTEUM (INNER)
44
origin of OSTEOBLASTS
OSTEOPROGENITOR CELL
45
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
46
UNIT OF BONE (MATRIX RINGS)
OSTEON (HAVERSIAN SYSTEM)
47
● 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
48
● Canal perpendicular (90*) to the central canal
PERFORATING (VOLKMANN'S) CANAL
49
● TINY CAVITY, containing osteocyte (mature bone cells) , arranged in concentric rings
LACUNAE
50
● containing arranged lacunae ● Rings around central (Haversian) canals of lacunae
LAMELLAE
51
● Tiny canals that radiate outward from the central canals to all lacunae ● GIVES OSTEON A TINY CRACK APPEARANCE
CANALICULI
52
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)
53
- LAYER OF UNIQUE COLLAGEN rich material between the osteoblast layer and the preexisting bone surface - Involves in the MINERALIZATION OF MATRIX
OSTEOID
54
(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
55
-(blastos: germ) - Growing cells which synthesize and secrete the organic components of the matrix
OSTEOBLAST
56
● 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
57
a layer of unique collagen-rich material between osteoblast layer and the pre-existing bone surface
OSTEOID
58
a vitamin K-dependnet polypeptide, prominent among the noncollagen proteins secreted by osteoblasts
OSTEOCALCIN
59
- 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
60
- Most abundant in bone - Enclosed singly within the lacunae spaced throughout the mineralized matrix
OSTEOCYTES
61
- where diffusion of metabolites between osteocytes and blood vessels occurs - Communicates via GAP JUNCTIONS which allows osteocytes to serve s mechnosensors
CANNALICULI
62
- 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
63
paracrine and endocrine that helps regulate bone remodeling
PROTEINS
64
- 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
65
BONE MATRIX - ____ INORGANIC MATERIALS
50%
66
Flat bones that form the calvaria (skullcap) have two layers of compact bone
PLATES
67
a thicker layer of cancellous bone that separates the plates
DIPLOE
68
organized most bone in adults compact or cancellous bones - characterized by multiple layers or lamellae calcified matrix (3-7 um thick)
LAMELLAR BONE
69
- 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
70
- 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
71
2 TYPES OF BONE ● Dense bone immediately beneath, periosteum ● Represents 80% of the total bone mass
COMPACT (CORTICAL BONE)
72
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
73
- Body of long bone - medullary cavity; bone marrow located
DIAPHYSIS
74
- Ends of the long bone - cancellous covered by compact bone
EPIPHYSIS
75
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
76
● 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
77
outer boundary of each osteon
CEMENT LINE
78
numerous irregularly shaped of parallel lamellae; scattered among intact osteons
Interstitial lamellae
79
● Have cores of cancellous bone surrounded by compact bone. ● Example: wrist and ankle
SHORT BONES
80
● 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
81
● Have 2 layers of compact bones (plates), separated by a thick layer of cancellous bone (diploe) ● Example: calvaria (skullcap)
FLAT BONES
82
BONE DEVELOPMENT/OSTEOGENESIS ● Osteoblast differentiate DIRECTLY from mesenchyme & begin secreting osteoid ● Forms most flat bone (skull, jaws, scapula
INTRAMEMBRANOUS OSSIFICATION
83
● Pre-existing matrix of hyaline cartilage is eroded & invaded by osteoblasts, which then begin osteoid production ● Forms most bones of the body
ENDOCHONDRAL OSSIFICATION
84
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
84
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
85
- composed of typical hyaline cartilage
ZONE OF REVERSE (resting) cartilage
86
- Cartilage cells divide repeatedly, enlarge, & secrete more type II collagen & proteoglycans & become ORGANIZED INTO COLUMNS
PROLIFERATIVE ZONE: (cell division of chondrocytes)
87
- most MATURE CHONDROCYTES in these lacunae SWELL UP, compress the matrix & undergo apoptosis
ZONE OF HYPERTROPHY: (increase in size of chondrocytes)
88
- 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)
89
● 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
90
➢ 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
91
_________-disrupt blood vessels, causing bone cells near the break to die
BONE FRACTURES
92
The damaged blood vessels produce a localized hemorrhage or __________
hematoma
93
bubble bone for repair
FIBROCARTILAGE
94
bone removes tissue
RESORPTION
95
_________required for the activity of many enzymes and many proteins mediating cell adhesion, cytoskeletal movements, exocytosis, membrane permeability, and other cellular functions.
Calcium ions
96
Skeleton serves as the ____________, containing 99% of the body’s total calcium in hydroxyapatite crystals
calcium reservoir
97
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)
98
The principal mechanism for raising blood calcium levels is the mobilization of ions from _____________ TO ____________, primarily in the cancellous bone.
hydroxyapatite to interstitial fluid
99
Ca2+ mobilization is regulated mainly by ____________ among bone cells
paracrine interactions
100
2 polypeptide hormones that target bone cells to influence calcium homeostasis:
PTH & CALCITONIN
101
- 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)
102
- 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
103
● Cancer of the bone ● Arise in osteoprogenitor cell ● Sunburst appearance
OSTEOSARCOMA
104
● 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
105
● 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
106
● In children: primarily due to a DEFICIENCY OF VITAMIN D or problem with its absorption → mineralization of bone tissue is impaired → soft
RICKETS
107
DEFICIENCY OF VITAMIN D in adults A. OSTEOPOROSIS B. OSTEOGENESIS IMPERFECTA C. OSTEITIS FIBROSA CYSTICA D. OSTEOMALACIA
OSTEOMALACIA
108
● 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
109
● 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
110
● Lack of growth hormone during the growing years
PITUITARY DWARFISM
111
● excess of growth hormone causes excessive growth of the long bones
GIGANTISM
112
A disease in which the bones (long become very thick.
ACROMEGALY
113
● 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
114
- high concentration of URIC ACID CRYSTAL in blood A. GOUTY ARTHRITIS B. RHEUMATOID ARTHRITIS C. OSTEOARTHRITIS
GOUTY ARTHRITIS
115
● 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
116
● Allow very limited or no movement ● Subdivided into fibrous and cartilaginous joints, depending on the type of tissue joining the bones.
SYNARTHROSES JOINTS
117
● 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
118
● 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
119
- 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
120
● 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
121
● 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
122
● 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
123
● 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
124
● 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
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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
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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
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● COLLAGEN LOSS or other degenerative changes in the annulus fibrosus are often accompanied by displacement of the nucleus pulposus
SLIPPED / HERNIATED DISC