CT, Cartilage, and Bone Histology

Question 1

What are the three components of CT?

Answer 1

Cells, fibers, ECM

Question 2

What is the resident cell of CT?

Answer 2

Fibroblast

Question 3

What are the features of loose CT?

Answer 3

More cells than collagen fibers

Question 4

Where is loose CT usually found?

Answer 4

Surrounding blood vessels, nerves, and muscles

Question 5

What are the features of dense CT?

Answer 5

More collagen fibers than cells

Question 6

What are the features of dense regular CT?

Answer 6

Preferentially oriented collagen fibers

Question 7

What are the features of dense irregular CT?

Answer 7

Randomly oriented collagen fibers

Question 8

What is the structure of GAGs?

Answer 8

Long, unbranched polysaccharides consisting of repeating disaccharide units; highly negatively charged

Question 9

What is the function of GAGs?

Answer 9

Associate with large amounts of water to create hydrated gels with high viscosity and low compressibility

Question 10

What are the four main components of the ECM?

Answer 10

Glycoaminoglycans (GAGs), proteoglycans, adhesive glycoproteins, and collagen

Question 11

What is the structure of proteoglycans?

Answer 11

Protein core with at least one covalently bound GAG; highly negatively charged

Question 12

What are the functions of proteoglycans?

Answer 12

Organization and stabilization of the ECM by interaction with other molecules; component of the basal lamina of epithelial cells to create a barrier to the passage of positively charged molecules

Question 13

What is the structure of adhesive glycoproteins?

Answer 13

Proteins with disulfide-bound subunits and binding sites for cells and other ECM components

Question 14

What are the functions of adhesive glycoproteins?

Answer 14

Facilitate the attachment of cells to the ECM; affect growth, survival, morphology, differentiation, and motility of cells

Question 15

What are the two primary glycoproteins?

Answer 15

Laminin and fibronectin

Question 16

What is the general function of type I, II, and III collagen?

Answer 16

Providing tensile strength to tissues

Question 17

What is the structure of mature collagen fibers?

Answer 17

Multiple associated triple helices formed by three individual α-chains

Question 18

How is collagen formed?

Answer 18

Fibroblast translates and modifies individual α-chains; assembly of α-chains into soluble triple helix (procollagen); secretion of procollagen into extracellular space; cleavage via proteases (C and N propeptidase) into insoluble tropocollagen; spontaneous assembly of tropocollagen into collagen fibrils; association of collagen fibrils into immature collagen fibers; crosslinking of immagture collagen fibers via lysyl oxidase to form mature collagen fibers

Question 19

What are the three types of cartilage?

Answer 19

Hyaline, elastic, and fibrous

Question 20

What are the primary cells that form cartilage?

Answer 20

Chondrocytes

Question 21

What type of cartilage is this?

Answer 21

Hyaline cartilage

Question 22

What type of cartilage is this?

Answer 22

Elastic cartilage

Question 23

What type of cartilage is this?

Answer 23

Fibrous cartilage

Question 24

What is the connective tissue layer that surrounds most cartilage?

Answer 24

Perichondrium

Question 25

What is the function of the perichondrium?

Answer 25

Contains stem cells that differentiate into chondroblasts, then chondrocytes

Question 26

What are the two mechanisms by which chondrocytes grow?

Answer 26

Interstitial growth by division of existing chondrocytes; appositional growth by the production of new cells from the perichondrium

Question 27

Not a real question, but did you know that cartilage and dense regular connective tissue are avascular and therefore heal poorly?

Answer 27

\*In the voice of Cecil from WTNV\*: ...neat!

Question 28

What is the structure of hyaline cartilage?

Answer 28

Surrounded by perichondrium; chondrocytes surrounded by type II collagen, proteoglycans, and water (provides compressive strength)

Question 29

Where is hyaline cartilage found?

Answer 29

Skeleton of the embryo, articular cartilage in joints, cartilage of respiratory tract

Question 30

What is the structure of elastic cartilage?

Answer 30

Surrounded by perichondrium; surrounded by type II collagen, proteoglycans, and elastic fibers

Question 31

Where is elastic cartilage found?

Answer 31

External ear and epiglottis

Question 32

What is the structure of fibrous cartilage?

Answer 32

No perichondrium; surrounded by type I collagen; resembles dense fibrous connective tissue

Question 33

Where is fibrinous cartilage found?

Answer 33

Intervertebral disks, menisci of the knee, pubic symphysis

Question 34

What is the composition of the organic matrix of the bone (osteoid)?

Answer 34

Type I collagen and proteoglycans (osteocalcin, osteopontin, osteonectin)

Question 35

What is the composition of the inorganic matrix of the bone (bone mineral)?

Answer 35

Hydroxyapatite (calcium and phosphate salt)

Question 36

What are the four major cell types in bone?

Answer 36

Osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells

Question 37

What are the functions of osteoblasts?

Answer 37

Deposit osteoid along the osteoblast-bone interface; initiate and control mineralization of the osteoid

Question 38

Maybe make a card that says: What are some of the proteins that osteoblasts express?

Answer 38

Cool

Question 39

What is the first bone matrix produced by the osteoblast?

Answer 39

Primary or woven bone

Question 40

What are the characteristics of primary/woven bone?

Answer 40

Loose, randomly oriented collagen fibers; low amounts of hydroxyapatite

Question 41

What is the primary/woven bone matrix remodeled into?

Answer 41

Secondary or lamellar bone

Question 42

What are the characteristics of secondary/lamellar bone?

Answer 42

Organized sheets of collagen fibers (lamella); high amounts of hydroxyapatite

Question 43

What is the function of osteocytes?

Answer 43

Respond to forces on the bone, release factors that stimulate bone remodeling or turnover

Question 44

What are the characteristics of osteocytes?

Answer 44

Highly branched cells; cell bodies occupy lacunae within the layers of bone matrix; processes pass through canaliculi and interconnect

Question 45

How are osteocytes formed?

Answer 45

Osteoblasts flatten out and transform into osteocytes when bone formation is complete

Question 46

What is the primary function of osteoclasts?

Answer 46

Degradation of the bone matrix

Question 47

What are the characteristics of osteoclasts?

Answer 47

Large, multinucleated cells; highly polarized with a ruffled border; contains high levels of carbonic anhydrase II (creates acidic microenvironment for solubilizing mineralized component of bone; lots of steps that I don't really care to memorize unless McGuire says we have to)

Question 48

How are osteoclasts formed?

Answer 48

Derive from monocyte precursors in the bone marrow; undergo osteoclastogenesis (lots of steps that I don't really care to memorize unless McGuire says we have to)

Question 49

What is the function of calcitonin?

Answer 49

Decreases bone turnover by activating osteoclast calcitonin receptors (CTR), which inhibits osteoclast activity, causing immobilization and retraction away from the bone surface

Question 50

What are the two classifications of bone structure?

Answer 50

Cortical or compact bone; trabecular or cancellous bone

Question 51

What are the features of cortical/compact bone?

Answer 51

Osteocytes and bone matrix are arranged into osteons

Question 52

What is the structure of an osteon?

Answer 52

Central (Haversian) canal with blood vessel; canal surrounded by concentric layers (lamellae) of bone cells and matrix; canaliculi traverse the lamellae to form connections between lacunae and central canals

Question 53

What is the structure of trabecular/cancellous bone?

Answer 53

Layers of lamellae form bony trabeculae that project into the marrow cavity; randomly distributed osteocytes within trabeculae; surface of trabeculae covered with osteoblasts and osteoclasts

Question 54

What hormone is released in response to hypocalcemia?

Answer 54

Parathyroid hormone (PTH)

Question 55

What are the functions of PTH?

Answer 55

Decreases osteoid matrix synthesis by activating osteoblast receptors; increase bone turnover by secretion of osteoclast activating factors, which cause the differentiation of osteoclasts

Question 56

What hormone is released in response to hypercalcemia?

Answer 56

Calcitonin