CARTILAGE AND BONE Flashcards
(126 cards)
1
Q
______ is a tough, durable form of supporting connective tissue, characterized by an extracellular matrix (ECM) with high concentrations of Glycosaminoglycans or GAGs and proteoglycans, interacting with collagen and elastic fibers.
A
Cartilage
2
Q
Structural features of its matrix make ______
ideal for a variety of mechanical and protective
roles within the adult skeleton and elsewhere.
A
cartilage
3
Q
______ has a firm consistency that allows the tissue to bear mechanical stresses without permanent distortion.
A
Cartilage ECM
4
Q
In the respiratory tract, ears, and nose, ______ forms the framework supporting softer tissues.
A
cartilage
5
Q
Because of its resiliency and smooth, lubricated surface, ______ provides cushioning and sliding regions within skeletal joints and facilitates bone
movements.
A
cartilage
6
Q
Cartilage consists of cells called ______ embedded in the ECM which unlike connective tissue proper contains no other cell types.
A
chondrocytes
7
Q
Chondrocytes synthesize and maintain all ECM components and are located in matrix cavities called ______.
A
lacunae
8
Q
The physical properties of cartilage depend on electrostatic bonds between ______, ______, and the sulfated GAGs on densely packed ______.
A
type II collagen fibrils, hyaluronan, proteoglycans
9
Q
CARTILAGE
Its semi-rigid consistency is attributable to water bound to the ______ charged hyaluronan and GAG chains extending from proteoglycan core proteins, which in turn are enclosed within a dense
meshwork of thin ______.
A
negatively, type II collagen fibrils
10
Q
The high content of bound ______ allows cartilage to serve as a shock absorber, an important functional role.
A
water
11
Q
TYPES OF CARTILAGE:
A
Hyaline Cartilage, Elastic Cartilage, Fibrocartilage
12
Q
The ______ is a sheath of dense connective tissue that surrounds cartilage in most places, forming an interface between the cartilage and the tissues supported by the cartilage.
A
perichondrium
13
Q
This harbors the blood supply serving the cartilage and a small neural component.
A
perichondrium
14
Q
______ cartilage, which covers the ends of bones in movable joints and which 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
15
Q
Many genetic conditions in humans or mice that cause defective cartilage, joint deformities, or short
limbs are due to recessive mutations in genes for ______, the aggrecan ______, the ______, and other proteins required for normal chondrocyte function.
A
collagen type II, core protein, sulfate transporter
16
Q
______ cartilage, the most common of the three types, is homogeneous and semitransparent in the fresh state.
A
Hyaline
17
Q
In adults ______ cartilage is located in the articular surfaces of movable joints, in the walls of larger respiratory passages (nose, larynx, trachea, bronchi), in the ventral ends of ribs, where they articulate with the sternum, and in the epiphyseal plates of long bones, where it makes possible longitudinal bone growth.
A
hyaline
18
Q
In the embryo, ______ cartilage forms the temporary skeleton that is gradually replaced by bone.
A
hyaline
19
Q
The ______ is part of the extracellular material found in connective tissues like cartilage. It is not a cellular component but rather a mixture of proteins, fibers, and other substances that provide structural and biochemical support to the surrounding cells.
A
matrix
20
Q
The dry weight of hyaline cartilage is nearly ______% collagen embedded in a firm, hydrated gel of proteoglycans and structural glycoproteins. The proteoglycan make the matrix generally basophilic and the thin collagen fibrils are barely discernible. Most of the collagen in hyaline cartilage is ______, although small amounts of minor collagens are also present.
A
40, type II
21
Q
______ (250 kDa), with approximately 150 GAG side chains of chondroitin sulfate and keratan sulfate, is the most abundant proteoglycan of hyaline cartilage. Hundreds of these proteoglycans are bound noncovalently by link proteins to long polymers of ______. These proteoglycan complexes bind further to the surface of type II collagen fibrils. Water bound to GAGs in the proteoglycans constitutes up to ______%-______% of the weight of fresh hyaline cartilage.
A
Aggrecan, hyaluronan, 60, 80
22
Q
Another important component of cartilage matrix is the structural multiadhesive glycoprotein ______.
A
chondronectin
23
Q
Like fibronectin in other connective tissues, ______ binds specifically to GAGs, collagen, and integrins, mediating the adherence of chondrocytes to the ECM.
A
chondronectin
24
Q
Staining variations within the matrix reflect local differences in its molecular composition. Immediately surrounding each chondrocyte, the ______ is relatively richer in GAGs than collagen, often causing these areas of ______ to stain differently from the intervening areas of ______.
A
ECM, territorial matrix, interterritorial matrix
25
______ are the cells responsible for the synthesis and maintenance of the cartilage matrix. They are a specific type of cell found within cartilage tissue.
Chondrocytes
26
Cells occupy relatively little of the hyaline cartilage mass. At the periphery of the cartilage, young chondrocytes or ______ have an elliptic shape, with the long axes parallel to the surface. Deeper in the
cartilage, they are round and may appear in
groups of up to ______ cells that originate from
mitotic divisions of a single chondroblast and are called ______. As the chondrocytes become more active in secreting collagens and other ECM components, the aggregated cells are pushed apart and occupy separate lacunae.
chondroblasts, eight, isogenous aggregates
27
Cartilage cells and matrix may shrink slightly, leading to irregularly shaped chondrocytes and their retraction from the matrix, though in living tissue, chondrocytes fully occupy their ______. Due to the avascular nature of cartilage, chondrocytes respire under low-oxygen tension and metabolize glucose mainly through ______. Nutrients diffuse to chondrocytes from the cartilage surface, aided by the movement of water and solutes during tissue compression and decompression, which also defines the maximum thickness of ______ cartilage, typically found as small, thin plates.
lacunae, anaerobic glycolysis, hyaline
28
In contrast to other forms of cartilage and most other tissues, ______ cartilage is susceptible to partial or isolated regions of calcification during aging, especially in the costal cartilage adjacent to the ribs.
hyaline
29
______ of the hyaline matrix, accompanied by degenerative changes in the chondrocytes, is a common part of the aging process and in many respects resembles endochondral ossification by which bone is formed.
Calcification
30
Chondrocyte synthesis of sulfated GAGs and secretion of proteoglycans are accelerated by many hormones and growth factors. A major regulator of hyaline cartilage growth is the pituitary-derived protein called ______ hormone or ______.
growth, somatotropin
31
This hormone acts indirectly, promoting the endocrine release from the liver of insulin-like growth factors, or somatomedins, which directly stimulate the cells of hyaline cartilage.
somatotropin.
32
Cells of cartilage can give rise to either benign (______) or slow-growing, malignant (______) tumors in which cells produce normal matrix components. ______ seldom metastasize and are generally removed surgically.
chondroma, chondrosarcoma, Chondrosarcomas
33
The ______ is a dense layer of connective tissue that surrounds most types of cartilage, providing mechanical support and protection. It plays a crucial role in cartilage growth and repair by supplying new chondrocytes.
perichondrium
34
Except in the articular cartilage of joints, all hyaline cartilage is covered by a layer of dense connective tissue, the ______, which is essential for the growth and maintenance of cartilage.
perichondrium
35
The outer region of the perichondrium consists largely of collagen ______ fibers and ______, but an inner layer adjoining the cartilage matrix also contains ______ which provide a source for new chondroblasts that divide and differentiate into chondrocytes.
type I, fibroblasts, mesenchymal stem cells
36
______ cartilage is essentially similar to hyaline cartilage except that it contains an abundant network of elastic fibers in addition to a meshwork of collagen type II fibrils, which give fresh elastic cartilage a yellowish color. With appropriate staining the elastic fibers usually appear as dark bundles distributed unevenly through the matrix.
Elastic
37
More flexible than hyaline cartilage, ______ cartilage is found in the auricle of the ear, the walls of the external auditory canals, the auditory (Eustachian) tubes, the epiglottis, and the upper respiratory tract. This cartilage in these locations includes a perichondrium similar to that of most hyaline cartilage. Throughout this cartilage the cells resemble those of hyaline cartilage both physiologically and structurally.
elastic
38
The chondrocytes (C) and overall organization of ______ cartilage are similar to those of hyaline cartilage, but the matrix (M) also contains elastic fibers that can be seen as darker components
with proper staining. The abundant elastic fibers provide greater flexibility to this type of cartilage. The section in part b includes perichondrium (P) that is also similar to that of hyaline cartilage.
elastic
39
______ takes various forms in different structures but is essentially a mingling of hyaline cartilage and dense connective tissue . It is found in intervertebral discs, in attachments of certain ligaments, and in the pubic symphysis—all places where it serves as very tough, yet cushioning support tissue for bone.
Fibrocartilage
40
The relative scarcity of proteoglycans overall makes fibrocartilage matrix more ______ than that of hyaline or elastic cartilage. There is no distinct surrounding ______ in fibrocartilage.
acidophilic, perichondrium
41
______ varies histologically in different structures, but is always essentially a mixture of hyaline cartilage and dense connective tissue. In a small region of intervertebral disc, the axially arranged aggregates of chondrocytes (C) are seen to be surrounded by small amounts of matrix and separated by larger regions with dense collagen and scattered fibroblasts with elongated nuclei (arrows).
Fibrocartilage
42
Cartilage forms from embryonic mesenchyme through ______. Initially, mesenchymal cells round up, retract extensions, multiply, and pack closely. These cells are termed “______” during proliferation and “______” afterward, both with basophilic cytoplasm rich in RER for collagen synthesis. As the extracellular matrix (ECM) forms, it encloses cells in lacunae, separating chondroblasts. Cartilage differentiation progresses from the center outward, with central cells becoming chondrocytes and peripheral cells remaining chondroblasts, while the perichondrium develops from ______ mesenchyme.
chondrogenesis, chondroblasts, chondrocytes, superficial
43
Cartilage grows through ______ growth (mitotic division of chondrocytes) and ______ growth (differentiation of chondroblasts from perichondrium cells).
interstitial, appositional
44
______ growth predominates postnatally, while ______ growth in long bones increases length. In ______ cartilage, where there is no perichondrium, worn-away cells and matrix are replaced from within.
Appositional, interstitial, articular
45
______ tissue, the 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.
Bone
46
______ (or ______) tissue also serves as a reservoir of calcium, phosphate, and other ions that can be released or stored in a controlled fashion to maintain constant concentrations in body fluids.
Bone, osseous
47
______ is a specialized connective tissue composed of calcified extracellular material, the bone matrix, and following three major cell types.
Bone
48
BONE
three major cell types :
OSTEOCYTES
OSTEOBLASTS
OSTEOCLASTS
49
BONE CELL TYPE
______- found in cavities (lacunae) between bone matrix layers (lamellae), with cytoplasmic processes in small canaliculi (L. canalis, canal) that extend into the matrix
OSTEOCYTES
50
BONE CELL TYPE
______- growing cells which synthesize and secrete the organic components of the matrix
OSTEOBLASTS
51
BONE CELL TYPE
______- giant, multinucleated cells involved in removing calcified bone matrix and remodeling bone tissue
OSTEOCLASTS
52
______
- originates from mesenchymal stem cells
- produce the organic components of bone matrix, including type I collagen fibers, proteoglycans, and matricellular glycoproteins such as ______.
OSTEOBLASTS, osteonectin
53
______ osteoblasts are located exclusively at the surfaces of bone matrix where they are bound by integrins.
Active
54
When their synthetic activity is completed:
-Some osteoblasts differentiate as osteocytes entrapped in matrix bound lacunae
-Some flatten and cover the matrix surface as ______ CELLS
-Majority undergo ______.
BONE LINING, apoptosis
55
______
- layer of unique collagen-rich material
- produced when matrix components are secreted at the cell surface in contact with existing bone between the osteoblast layer and the preexisting bone surface.
This process of bone appositional growth is completed by subsequent deposition of ______ salts into the newly formed matrix.
OSTEOID, calcium
56
______
- vitamin K-dependent polypeptide
- is prominent among the noncollagen proteins secreted by osteoblasts
- together with various glycoproteins binds Ca ions and concentrates this mineral locally.
OSTEOCALCIN
57
______
- membrane-enclosed - released by osteoblasts
- rich in alkaline phosphatase and other enzymes whose activity raises the local concentration of PO ions
MATRIX VESICLES
58
In the microenvironment with high concentrations of both these ions, ______ serve as foci for the formation of hydroxyapatite crystals, the first visible step in calcification. These crystals grow rapidly by accretion of more mineral and eventually produce a confluent mass of calcified material embedding the collagen fibers and proteoglycans
matrix vesicles
59
Cancer originating directly from bone cells (a primary bone tumor) is fairly uncommon (______% of all cancer deaths), although a cancer called ______ can arise in osteoprogenitor cells. The skeleton is often the site of secondary, ______ TUMORS , however, arising when cancer cells move into bones via small blood or lymphatic vessels from malignancies in other organs, most commonly the breast, lung, prostate gland, kidney, or thyroid gland.
0.5, OSTEOSARCOMA, METASTATIC
60
This is A cell found within the material of fully formed bone. It lives in a small chamber known as a lacuna, which is found in the calcified matrix of bone.
OSTEOCYTE
61
During the transition from osteoblasts to osteocytes, the cells extend many long dendritic processes, which also become surrounded by calcifying matrix. The processes thus come to occupy the many ______, 250-300 nm, radiating from each lacuna .
canaliculi
62
Diffusion of metabolites between osteocytes and blood vessels occurs through the small amount of interstitial fluid in the ______ between the bone matrix and the osteocytes and their processes. ______ also communicate with one another and ultimately with nearby osteoblasts and bone lining cells via gap junctions at the ends of their processes. These connections between osteocyte processes and nearly all other bone cells in the extensive lacunar-canalicular network allow osteocytes to serve as mechanosensors detecting the mechanical load on the bone as well as stress- or fatigue-induced microdamage and to trigger remedial activity in osteoblasts and osteoclasts.
canaliculi, Osteocytes
63
______
- are very large, motile cells with multiple nuclei due to their origin from the fusion of bone marrow-derived monocytes which is essential for matrix resorption during bone growth and remodeling.
OSTEOCLASTS
64
OSTEOCLAST DEVELOPMENT
- requires two polypeptides produced by osteoblasts:
1. ______
2. ______
Macrophage colony stimulating factor (M-CSF), Receptor activator of nuclear factor-κB ligand (RANKL)
65
______ ( or ______)
- enzymatically etched depressions or cavities in the matrix where osteoclasts on the bone surface lie in , in areas of bone undergoing resorption
RESORPTION LACUNAE, HOWSHIP LACUNAE
66
In an active osteoclast, the membrane domain that contacts the bone forms a circular ______ that binds the cell tightly to the bone matrix and surrounds an area with many surface projections, called the ______.
SEALING ZONE, RUFFLED BORDER
67
This circumferential ______ allows the formation of a specialized microenvironment between the osteoclast and the matrix in which bone resorption occurs.
sealing zone
68
In the genetic disease ______, which is characterized by dense, heavy bones (“______ bones”), the osteoclasts lack ruffled borders and bone resorption is defective. This disorder results in overgrowth and thickening of bones, often with obliteration of the marrow cavities, depressing blood cell formation and causing anemia and the loss of white blood cells. The defective osteoclasts in most patients with this disease have mutations in genes for the cells’ proton-ATPase pumps or chloride channels.
OSTEOPETROSIS, marble
69
About 50% of the dry weight of bone matrix is ______ materials.
inorganic
70
INORGANIC MATERIALS bone matrix
______ is the most abundant, but bicarbonate, citrate, magnesium, potassium, and sodium ions are also found. The surface of ______ crystals are hydrated, facilitating the exchange of ions between the mineral and body fluids.
Calcium hydroxyapatite, hydroxyapatite
71
The organic matter embedded in the calcified matrix is ______% type I collagen, but also includes mostly small proteoglycans and multiadhesive glycoproteins such as osteonectin.
90
72
Calcium-binding proteins, notably ______, and the ______ released from cells in matrix vesicles promote calcification of the matrix.
osteocalcin, phosphatases
73
The association of minerals with collagen fibers during calcification provides the ______ and ______ required for bone function.
hardness, resistance
74
If a bone is decalcified by a histologist, its shape is preserved but it becomes soft and pliable like other connective tissues. Because of its high collagen
content, decalcified bone matrix is usually ______.
acidophilic
75
External and internal surfaces of all bones are covered by connective tissue of the ______ and ______, respectively.
periosteum, endosteum
76
The ______ has an outer fibrous layer of dense connective tissue which contains mostly bundled type I collagen, fibroblasts, and blood vessels.
periosteum
77
Bundles of periosteal collagen, called ______ (or ______) fibers, penetrate the bone matrix and bind the periosteum to the bone. Periosteal blood vessels branch and penetrate the bone, carrying metabolites to and from bone cells.
perforating, Sharpey
78
The periosteum’s ______ layer is more cellular and includes osteoblasts, bone lining cells, and mesenchymal stem cells referred to as ______ cells.
inner, osteoprogenitor
79
With the potential to proliferate extensively and
produce many new osteoblasts, ______ cells play a prominent role in bone growth and repair.
osteoprogenitor
80
This is An imbalance in skeletal turnover wherein bone resorption exceeds bone formation and is Frequently found in immobilized patients and in
postmenopausal women.
OSTEOPOROSIS
81
This Leads to calcium loss from bones and reduced bone mineral density (BMD) and is Tested through dual-energy x-ray absorptiometry (DEXA scans).
OSTEOPOROSIS
82
TYPES OF BONE:
Woven bone
Lamellar bone
Compact bone
Cancellous bone
83
______ (______)
(80% of total bone mass)
- a dense area near the surface
Compact, cortical
84
______ (______)
(20% of total bone mass)
- deeper areas with numerous interconnecting cavities
Cancellous, trabecular
85
______- made of cancellous bone covered by a thin layer of compact cortical bone.
Epiphysis
86
______- cylindrical part that is almost totally dense compact bone with a thin region of cancellous bone on the inner surface around the central marrow cavity
Diaphysis
87
______- thicker layer of cancellous bone in flat bones.
Diploë
88
At the microscopic level both compact and cancellous bones typically show two types of organization: ______ bone, with matrix existing as discrete sheets, and ______ bone, newly formed with randomly arranged components.
mature lamellar, woven
89
Macroscopic photo of a thick section of bone showing the cortical compact bone and the lattice of trabeculae in cancellous bone at the bone’s interior. The small ______ that make up highly porous cancellous bone serve as supportive struts, collectively providing considerable strength, without greatly increasing the bone’s weight. The ______ bone is normally covered externally with periosteum and all trabecular surfaces of the ______ bone are covered with endosteum.
trabeculae, compact, cancellous
90
______ bone is nonlamellar and characterized by random disposition of type I collagen fibers and is the first bone tissue to appear in embryonic development and in fracture repair.
Woven
91
______ bone is usually temporary and is replaced in adults by lamellar bone, except in a very few places in the body, for example, near the sutures of the calvaria and in the insertions of some tendons.
Woven
92
In addition to the irregular, interwoven array of collagen fibers, ______ bone typically has a lower mineral content (it is more easily penetrated by x rays) and a higher proportion of osteocytes than mature lamellar bone. These features reflect the facts that immature ______ bone forms more quickly but has less strength than lamellar bone.
woven, woven
93
Bone Development or Osteogenesis occurs by one of the two processes:
Intramembranous ossification
Endochondral ossification
94
Bone Development or Osteogenesis occurs by one of the two processes:
______ ossification, in which osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
Intramembranous
95
Bone Development or Osteogenesis occurs by one of the two processes:
______ ossification, in which a preexisting matrix of hyaline cartilage is eroded and invaded by osteoblasts, which then begin osteoid production
Endochondral
96
The names refer to the mechanisms by which the bone forms initially; in both processes ______ bone is produced first and is soon replaced by stronger
______ bone. During growth of all bones, areas of woven bone, areas of bone resorption, and areas of lamellar bone all exist contiguous to one another.
woven, lamellar
97
______ ossification, by which most flat bones begin to form, takes place within condensed sheets (“membranes”) of ______ tissue. Most bones of the skull and jaws, as well as the scapula and clavicle, are formed embryonically by ______ ossification.
Intramembranous, embryonic mesenchymal, intramembranous
98
INTRAMEMBRANOUS OSSIFICATION
Within the condensed ______ bone formation begins in ossification centers, areas in which
osteoprogenitor cells arise, proliferate, and form incomplete layers of osteoblasts around a network of developing ______. ______ secreted by the osteoblasts calcifies as described earlier, forming small irregular areas of woven bone with osteocytes in lacunae and canaliculi.
mesenchyme, capillaries, Osteoid
99
INTRAMEMBRANOUS OSSIFICATION
Continued matrix secretion and calcification enlarges these areas and leads to the fusion of neighboring ossification centers. The ______ bone forms gradually as woven bone matrix is replaced by compact bone that encloses a region of cancellous bone with marrow and larger blood vessels. Mesenchymal regions that do not undergo ossification give rise to the ______ and the ______ of the new bone. In cranial flat bones, lamellar bone formation predominates over bone resorption at both the internal and external surfaces. Internal and external plates of compact bone arise, while the central portion (______) maintains its cancellous nature. The ______ or “______” on the heads of newborn infants are areas of the skull in which the membranous tissue is not yet ossified.
anatomical, endosteum, periosteum, diploë, fontanelles, soft spots
100
______ (Gr. ______, within + ______, cartilage) ossification takes place within hyaline cartilage shaped as a small version, or model, of the bone to be formed. This type of ossification forms most bones of the body and is especially well studied in developing long bones, where it consists of the sequence of events.
Endochondral, endon, chondros
101
ENDOCHONDRAL OSSIFICATION
- ______ cartilage within the joints between long bones, which normally persists through adult life
- The specially organized ______ cartilage (also
called the ______ or ______), which connects each epiphysis to the diaphysis and allows longitudinal bone growth
Articular, epiphyseal, epiphyseal plate, growth plate
102
Basic growth involves both the continuous resorption of bone tissue formed earlier and the simultaneous laying down of new bone at a rate exceeding that of bone removal. The sum of osteoblast and osteoclast activities in growing bone constitutes ______ or the process of ______, which maintains the bone’s general shape while increasing its mass.
osteogenesis, bone modeling
103
the rate of bone turnover is very active in young children where it can be ______ times faster than adults. in adults, the skeleton is also renewed continuously in a process of ______ which involves the coordinated, localized, cellular activities for bone resorption and formation.
200, bone remodeling
104
The constant remodeling of bone ensures that, despite its ______, this tissue remains plastic and capable of adapting its internal structure in the face of changing stresses. A well known example of bone ______ is the ability of the positions of teeth in the jawbone to be modified by the lateral pressures produced by orthodontic appliances. Bone forms on the side where traction is applied and is resorbed on the opposite side where pressure is exerted. In this way, teeth are moved within the jaw while the bone is being remodeled
hardness, plasticity
105
Because it contains ______ cells in the periosteum, endosteum, and marrow and is very well vascularized, bone normally has an excellent capacity for repair. Bone repair after a fracture or other damage uses cells, signaling molecules, and processes already active in bone remodeling. Surgically created gaps in bone can be filled with new bone, especially when ______ is left in place.The major phases that occur typically during bone fracture repair include initial formation of ______ and its replacement with a tempo rary callus of ______ bone.
osteoprogenitor stem, periosteum, fibrocartilage, woven
106
Because it contains ______ cells in the periosteum, endosteum, and marrow and is very well vascularized, bone normally has an excellent capacity for repair. Bone repair after a fracture or other damage uses cells, signaling molecules, and processes already active in bone remodeling. Surgically created gaps in bone can be filled with new bone, especially when ______ is left in place.The major phases that occur typically during bone fracture repair include initial formation of ______ and its replacement with a tempo rary callus of ______ bone.
osteoprogenitor stem, periosteum, fibrocartilage, woven
107
______ are required for the activity of many enzymes and many proteins mediating cell adhesion, cytoskeletal movements, exocytosis, membrane permeability, and other cellular functions.
Calcium ions
108
The ______ serves as the calcium reservoir, containing ______% of the body’s total calcium in ______ crystals. The concentration of calcium in the blood (9-10 mg/dL) and tissues is generally quite stable because of a continuous interchange between blood calcium and bone calcium.
skeleton, 99, hydroxyapatite
109
The principal mechanism for raising blood calcium levels is the mobilization of ions from ______ to ______, primarily in cancellous bone. ______ mobilization is regulated mainly by paracrine interactions among bone cells, many of which are not well understood, but two olypeptide hormones also target bone cells to influence calcium homeostasis
hydroxyapatite, interstitial fluid, Ca2+
110
two olypeptide hormones also target bone cells to influence calcium homeostasis:
PARATHYROID HORMONE
CALCITOSIN
111
______
- raises low blood calcium levels by stimulating osteoclasts and osteocytes to resorb bone matrix and release Ca2+. The PTH effect on osteoclasts is indirect; PTH receptors occur on osteoblasts, which respond by secreting RANKL and other paracrine factors that stimulate osteoclast formation and activity
PARATHYROID HORMONE
112
______
- produced within the thyroid gland, can reduce elevated blood calcium levels by opposing the effects of PTH in bone. This hormone directly targets osteoclasts to slow matrix resorption and bone turnover.
CALCITOSIN
113
______ are regions where adjacent bones are capped and held together firmly by other connective tissues.
Joints
114
The type of ______ determines the degree of movement between the bones.
joint
115
Joints classified as ______ (Gr. ______, together + ______, articulation) allow very limited or no movement and are subdivided into fibrous and cartilaginous joints, depending on the type of tissue joining the bones.
synarthroses, syn, arthrosis
116
Major subtypes of synarthroses include the following:
SYNOSTOSES
SYNDESMOSES
SYMPHYSES
117
Major subtypes of synarthroses
______
- involve bones linked to other bones and allow essentially no movement. In older adults ______ unite the skull bones, which in children and young adults are held together by sutures, or thin layers of dense connective tissue with osteogenic cells.
SYNOSTOSES, synostoses
118
Major subtypes of synarthroses
______
- 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.
SYNDESMOSES
119
Major subtypes of synarthroses
______
- have a thick pad of fibrocartilage between the thin
articular cartilage covering the ends of the bones. All
symphyses, such as the intervertebral discs and pubic symphysis, occur in the midline of the body.
SYMPHYSES
120
Joints classified as ______ permit free bone move ment.
diarthroses
121
______ such as the elbow and knee generally unite long bones and allow great mobility.
Diarthroses
122
In a ______ ligaments and a capsule of dense connective tissue maintain proper alignment of the bones. The capsule encloses a sealed joint cavity containing a clear, viscous liquid called ______ fluid. The joint cavity is lined, not by epithelium, but by a specialized connective tissue called the ______ that extends folds and villi into the joint cavity and produces the lubricant synovial fluid.
diarthrosis, synovial, synovial membrane
123
In different ______ joints the synovial membrane may have prominent regions with dense connective tissue or fat. The superficial regions of this tissue however are usually well vascularized, with many ______ (fenestrated) capillaries. Besides having cells typical of connective tissue proper and a changing population of leukocytes, this area of a synovial membrane is characterized by two specialized cells with distinctly different functions and origins:
_______ SYNOVIAL CELLS
_______ SYNOVIAL CELLS
diarthrotic, porous, MACROPHAGE-LIKE, FIBROBLASTIC
124
two specialized cells with distinctly different functions and origins
______ CELLS
- are derived from blood monocytes and remove wear-and-tear debris from the synovial fluid. These modified macrophages, which represent approximately 25% of the cells lining the synovium, are important in regulating inflammatory events within diarthrotic joints.
MACROPHAGE-LIKE SYNOVIAL
125
two specialized cells with dis tinctly different functions and origins
______ CELLS
- produce abundant hyaluronan and smaller amounts of proteoglycans. Much of this material is 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
126
The ______ fibers of the hyaline articular cartilage are disposed as arches with their tops near the exposed surface which, unlike most hyaline cartilage, is not covered by perichondrium. This arrangement of collagen helps distribute more evenly the forces generated by pressure on joints. The resilient ______ cartilage efficiently absorbs the intermittent mechanical pressures to which many joints are subjected.
collagen, articular
