Mss: Lab 1 - Skeletal Tissues - Cartilage & Bone

Front 1

What do all connective tissues (e.g., cartilage and bone) consist of?

Back 1

- Cells (e.g., chondrocytes)
- ECM (fibers and ground substance)

Front 2

What happens to the cells of cartilage in the connective tissue?

Back 2

Chondrocytes become trapped within abundant ECM secretions

Front 3

What part of cartilage makes it firm and pliable?

Back 3

ECM

Front 4

What are the three types of cartilage?

Back 4

- Hyaline
- Elastic
- Fibrocartilage

Front 5

What kind of cartilage is shown in this specimen?

Back 5

Hyaline cartilage (dark purple-stained portion)

Front 6

What is the pink-staining supporting tissue along the periphery of the hyaline cartilage (dark purple)?

Back 6

Perichondrium

Front 7

What are the fibroblast-like, spindle-shaped cells within the perichondrium? What is their function?

Back 7

Chondrogenic Cells - when cartilage is actively growing, these cells gradually enlarge to become Chondroblasts (which secrete ECM)

Front 8

What is the function of Chondroblasts (mature Chondrogenic Cells)? Terminology?

Back 8

- Maintain integrity of cartilaginous matrix by synthesizing and secreting ECM components (Collagen, Elastic Fibers, Ground Substance)
- Called Chondrocytes when they are surrounded by ECM

Front 9

Which organelles are prominent in Chondrocytes?

Back 9

- Round Endoplasmic Reticulum
- Golgi Apparatus

Front 10

The process of cartilage growth at its periphery by mitotic division of Chondrogenic Cells and subsequent production of ECM by Chondroblasts is called what?

Back 10

Appositional Growth

Front 11

What is the appearance of hyaline cartilage? Why?

Back 11

Homogenous - because Type II collagen fibrils in matrix are small

Front 12

What are two components of the ground substance in hyaline cartilage?

Back 12

- Proteoglycans
- Glycoproteins

Front 13

Are there blood vessels or nerves in cartilage?

Back 13

No

Front 14

What is the name of the compartments / cavities that are occupied by chondrocytes?

Back 14

Lacunae

Front 15

Chondrocytes are capable of mitosis and yield small clones called what?

Back 15

Cell Nests (up to 8 cells) = isogenous aggregates

Front 16

What happens in the cell nests?

Back 16

- Cells are originally close together
- Differentiate and secrete ECM around the cells
- Cells become separated into lacunae

Front 17

How many chondrocytes are there in a lacuna?

Back 17

Usually only one chondrocyte / lacuna (although it is possible to have 2/lacuna)

Front 18

Cartilage growth from within by mitosis of chondrocytes is called what?

Back 18

Interstitial Growth

Front 19

What is the ECM directly surrounding the chondrocytes called? As opposed to the ECM further from the chondrocytes?

Back 19

- Directly = Territorial Matrix (may surround only one lacuna or a group of lacunae that were from same cell nest)
- Further = Inter-Territorial Matrix

Front 20

Which type of ECM surrounding chondrocytes is more basophilic?

Back 20

ECM directly surrounding chondrocytes (Territorial Matrix)

Front 21

Why is the ECM directly surrounding the chondrocytes more basophilic than the ECM further from the chondrocytes?

Back 21

- Territorial Matrix is poor in collagen and has a greater concentration of newly synthesized proteoglycans
- Sulfated proteoglycans are negatively charged (=basophilic)

Front 22

What type of cartilage (pink stain) is this? What is pointed at by the arrow?

Back 22

Elastic Cartilage

Front 23

What is A?

Back 23

Perichondrium

Front 24

What is B?

Back 24

Chondrocytes

Front 25

What is C?

Back 25

Lacunae

Front 26

What is D?

Back 26

Cell Nests

Front 27

What is the appearance of elastic cartilage? Why?

Back 27

Heterogenous - pink, stringy appearance of ECM d/t presence of elastic fibers that do not stain well

Front 28

What is shown in this slide?

Back 28

- Elastic cartilage that has been treated with a stain
- Turns the elastic fibers black
- Note branching of the fibers in the cartilage matrix.

Front 29

What is shown in this slide?

Back 29

Elastic fibers (black) in connective tissue and walls of blood vessels

Front 30

What are three sites in the human body where elastic cartilage is found?

Back 30

- Pinna
- External auditory canal eustachian tube
- Some laryngeal cartilages (e.g., epiglottis)

Front 31

What property of elastic fibers make elastic cartilage more suitable for these sites (e.g., pinna, external auditory canal eustachian tube, epiglottis) than hyaline cartilage?

Back 31

More flexible

Front 32

What is shown in this slide?

Back 32

- Fibrocartilage
- Chondrocytes are surrounded by very little matrix and tend to be arranged in rows between coarse bundles of collagen fibers
- Alternating arrangement of collagen bundles in adjacent layers of fibrocartilage
- No perichondrium

Front 33

What is the major type of collagen fiber present in fibrocartilage?

Back 33

Type I Collagen

Front 34

What are some sites in the human body where fibrocartilage is found?

Back 34

- Intervertebral disks (annulus fibrosus)
- Pubic symphysis
- Menisci of knee joint
- Some tendinous attachments to bone
- Within articular discs of the sternoclavicular and temporomandibular joints

Front 35

How does the arrangement of collagen bundles in adjacent layers of fibrocartilage contribute to the function of this supporting tissue?

Back 35

Arrangement helps it function as a shock absorber, resisting compression and sheer forces

Front 36

What is shown in this slide?

Back 36

- Annulus fibrosis of intervertebral disc (fibrocartilage)
- Parallel rows of chondrocytes are arranged between layers of collagen bundles
- Gives it a herringbone appearance

Front 37

What is shown in this slide?

Back 37

Articular Cartilage

Front 38

What type of cartilage does Articular Cartilage resemble? How is it different?

Back 38

Hyaline cartilage - but no perichondrium

Front 39

This is an image of a mouse embryo, how does the cartilage compare to mature cartilage?

Back 39

Developing cartilage has MORE cells and LESS matrix

Front 40

Hyaline Cartilage:
- Homogenous ECM?
- Fiber types present?
- Locations in body?
- Perichondrium present?

Back 40

Hyaline Cartilage:
- Homogenous ECM
- Type II collagen, elastic fibers, ground substance
- Ventral ends of ribs, larynx, trachea, and bronchi
- Perichondrium present

Front 41

Elastic Cartilage:
- Homogenous ECM?
- Fiber types present?
- Locations in body?
- Perichondrium present?

Back 41

Elastic Cartilage:
- Heterogenous ECM
- Elastic fibers
- Pinna, external auditory canal, eustachian tube, and laryngeal cartilages
- Perichondrium present

Front 42

Fibrocartilage:
- Homogenous ECM?
- Fiber types present?
- Locations in body?
- Perichondrium present?

Back 42

Fibrocartilage:
- Homogenous ECM
- Type I collagen
- IV discs, pubic symphysis, knee minisci, some tendonous attachments to bone, articular discs
- No perichondrium

Front 43

How can bones be classified?

Back 43

- Shape
- Gross appearance
- Microscopic appearance

Front 44

How can bone tissue be classified by gross appearance?

Back 44

- Compact (cortical) bone - found in diaphysis of long bones and inner and outer tables of some skull bones
- Spongy (trabecular, cancellous) bone - found in epiphysis and metaphysis of long bones and between tables of some skull bones

Front 45

How can bone tissue be classified by microscopic appearance?

Back 45

- Woven (immature, primary) - randomly oriented collagen fiber bundles
- Lamellar (mature, secondary) - organized into parallel sheets for great mechanical strength

Front 46

When and where does lamellar bone appear?

Back 46

- During development, lamellar bone appears during late fetal period
- In mature bone, both compact and spongy bone is lamellar

Front 47

How can bone pieces be analyzed histologically?

Back 47

- Bone pieces dried and ground into thin sections (preserves ECM)
- Bone is decalcified in acid or chelating agents (e.g., EDTA) to preserve cells and collagenous material which is sectioned and stained

Front 48

What is shown in this slide?

Back 48

- Fetal digit - bone tissue is initially "woven" or "primary"
- Woven bone comprises the diaphysis

Front 49

The collagen fiber bundles (pink) are oriented in what manner?

Back 49

Randomly oriented (woven/primary bone tissue)

Front 50

The majority of the periosteum consists of what type of tissue?

Back 50

Fibrous Connective Tissue

Front 51

What type of bone is this? How are the collagen fiber bundles organized?

Back 51

Compact bone - organized into distinct layers or lamellae

Front 52

What is the concentric arrangement of lamellae in compact bone called?

Back 52

Haversion system (Osteon)

Front 53

What is at the middle of each Osteon?

Back 53

Haversion Canal - which contains blood vessels, nerves, and osteoblasts

Front 54

What fills in the gaps in compact bone between the Osteons?

Back 54

Interstitial Lamellae (remnants of older osteons that have been partially resorbed)

Front 55

What are the layers of bone surrounding the osteonal canals?

Back 55

Concentric Lamellae

Front 56

What are the spaces between the concentric lamellae surrounding the osteonal canals? What is in these spaces?

Back 56

Lacunae - contain Osteocytes

Front 57

What is the name for the tiny dark lines radiating from each lacuna? Function?

Back 57

Canaliculi - contain cytoplasmic processes of osteocytes that form gap junctions with processes of adjacent osteocytes, enabling diffusion of metabolites between osteocytes and blood vessels in the Haversian canals

Front 58

What are the forces that keep bone continuously remodeling?

Back 58

- Structural forces placed on bone (basis of orthodontics)
- Hormones which regulate blood calcium level

Front 59

What are the canals that are oriented perpendicular to Haversian canals called?

Back 59

Volkmann's Canals

Front 60

What comprises 70% of the dry weight of bone tissue?

Back 60

Inorganic, mineralized matrix

Front 61

What is Structure A?

Back 61

Trabeculae / Spicules = projections of spongy bone cut in various directions; interconnected to form a network (in 3D)
(Like the material of the sponge)

Front 62

What is Structure B?

Back 62

Red Bone Marrow (within spongy bone)
(like the water held by the sponge - occupies spaces between trabeculae)

Front 63

What is shown in this slide?

Back 63

- A broken bone (bone layers and marrow cavity on each side are not in alignment across middle of slide)
- Dome shaped upper portion = thickening = primary callus

Front 64

What is this material?

Back 64

Transitory Cartilage - appears to be fibrocartilage involved in fracture repair (serves as a platform for endochondral ossification and replacement by woven/primary bone tissue to form the secondary callus)

Front 65

The secondary callus will be remodeled and replaced by what kind of bone tissue?

Back 65

Secondary

Front 66

What are the purple cells lining the white psaces within bone?

Back 66

Cuboid-shaped osteoblasts and osteoprogenitor cells

Front 67

Why are these purple osteoblasts and osteoprogenitor cells considered "basophilic"?

Back 67

They have abundant RER for synthesis of matrix components, which is stained by hematoxylin

Front 68

What process of bone growth is facilitated by these cells?

Back 68

Apositional growth (girth of a bone at its diaphysis is increased)

Front 69

What are the cells marked by "O"? Describe?

Back 69

- Osteocytes
- Large, multinucleated cells
- Function is bone resorption (calcium release)

Front 70

What causes bone to be a very dynamic tissue?

Back 70

- Alternating activity of osteoblasts and osteoclasts
- Architecture is remodeled to meet needs of physical stresses
- Mechanical support and calcium storage/release

Front 71

What factors influence the activity of osteoblasts and osteoclasts?

Back 71

Osteoclasts are stimulated by Parathyroid Hormone (PTH) and inhibited by Calcitonin

Front 72

Bone formation occurs in what two ways?

Back 72

- Intramembranous ossification
- Endochondral ossification (formation of a hyaline cartilage model which is gradually replaced by bone)

Front 73

Where does endochondral ossification bone formation occur?

Back 73

- Long bones of embryo
- Epiphyseal plates of long bones

Front 74

What kind of cells absorb cartilage? What kind of cells are they similar to?

Back 74

Chondroclasts (multinucleated cells) - histologically indistinguishable from osteoclasts

Front 75

What are the zones of the epiphyseal plate?

Back 75

- Reserve cartilage
- Proliferative zone
- Hypertrophy and Calcification
- Cartilage Degeneration
- Osteogenic

Front 76

What might happen in the embryo regarding endochondral ossification if osteoblasts were dysfunctional?

Back 76

Bone formation would not occur

Front 77

What is osteoporosis?

Back 77

Decrease in bone mass - affects >30 million Americans, especially chronically immobilized patients and postmenopausal women

Front 78

A vs B?

Back 78

A = normal
B = osteoporotic bone

Front 79

Which bone cell type likely contributes to osteoporosis?

Back 79

Osteoclasts

Front 80

As a physician, what type of treatment interventions might you recommend to manage the osteoporotic patient?

Back 80

- Drugs that stimulate osteoblast formation (fluorides)
- Estrogen (maintains bone mass)
- Calcium supplements
- Drugs that decrease osteoclast formation (calcitonin, bisphosphonates)

Front 81

What are some nutritional or hormonal factors which influence bone calcification, growth, or maintenance?

Back 81

- Protein deficiency
- Ca2+ deficiency
- Increase in PTH
- Increase in Calcitonin

Front 82

Bone:
- Cell nests?
- Blood vessels within matrix?
- Lamellae?
- Speed of tissue turnover?
- Amount of mineralization?

Back 82

Bone:
- No cell nests
- Blood vessels in matrix
- Lamellae
- Rapid tissue turnover
- ~65% mineralization

Front 83

Cartilage:
- Cell nests?
- Blood vessels within matrix?
- Lamellae?
- Speed of tissue turnover?
- Amount of mineralization?

Back 83

Cartilage:
- Cell nests
- No blood vessels in matrix
- No lamellae
- Slow tissue turnover
- No mineralization