Wvsom Msk - Cartilage, Bone, Bone Growth

Front 1

Compare the extracellular matrix of other connective tissues to cartilage

Back 1

Avascular - diffusion through ECM is vital.

Made of cells, fibers, ground substance

Front 2

Describe cartilage cells:

Back 2

Cells are derived from the same stem cells as fibroblasts but are called chondrocytes

Front 3

Describe cartilage fibers:

Back 3

Type 2 collagen is the main fiber of cartilage, is unique to cartilage, but is too small to see

Front 4

Describe cartilage ground substance:

Back 4

Glycosaminoglycans

Chondrotin sulfate

Keratin sulfate

Front 5

List the defining characteristics of chondrocytes including their location and the substances they release in to the extracellular matrix.

Back 5

Surrounded by ECM and live in lacunae - Lacuna means Island

Live in lacunae either single or in recently divided forms called isogenous groups

Increase age > lose ability to repair and maintain ECM > dehydration and calcification

Front 6

Relate the roles of chondroitin, keratin sulfate and hyaluronan to the function of the extracellular matrix of cartilage.

Back 6

1. Chondroitin: NEGATIVELY charged > Linked to proteoglycan
2. keratin sulfate: NEGATIVELY charged > linked to proteoglycan
3. Hyaluronan > form a core for which the proteoglycans can attach
4. Overall look like a PIPECLEANER: provide structural integrity while pulling a lot of water into the cell

Front 7

Differentiate between chondroblasts and chondrocytes.

Back 7

1. Located in the lacunae as either single or newly divided isogenous groups
2. Look like they have a halo with a nucleus in the center around pink ECM
3. Chondroblasts: found in the inner layer of the periosteum > Turn into chondrocytes once in a lacunae

Front 8

Differentiate between appositional and interstitial growth.

Back 8

Appositional growth: cartilage growth from the perichondrium

Interstitial growth: division of chondrocytes to produce daughter cells in the isogenous groups

Important for long bone growths

Occurs in ADDITION to appositional growth

Front 9

Identify and list the functions of the perichondrium.

Back 9

Thin layer of dense irregular connective tissue with

outer fibrous layer - filled with fibroblasts & blood vessels that supply the cartilage.

Inner layer - produce new chondroblasts which become chondrocytes once encased by Lacunae

Front 10

Describe hyaline cartilage with reference to location, appearance, function, extracellular products and blood supply.

Back 10

Location: epiphyseal plates, articular surfaces, larynx, trachea and bronchi, and nasal cartilages

Appearance: uniform glassy appearance due to large amount of extracellular matrix between widely spread cells

Function: appositional (chondrocyte production from chondroblasts from periosteum) and interstitial growth (division of chondrocytes)

EC products:

Blood supply: outer layer of periosteum (fibrous layer) has fibroblasts and type I collagen with small blood vessels that supply cartilage

Front 11

Describe elastic cartilage with reference to location, appearance, function, extracellular products and blood supply.

Back 11

same as hyaline but also has large amount of ELASTIC fibers in ECM > rubbery and mobile

Location: external ear, auditory tube (eustacean), epiglottis cartilages

Appearance:

Function: allows rubbery/mobile function

EC products: elastin

Blood supply: only receive blood from surrounding periosteum

Front 12

Describe fibrocartilage with reference to location, appearance, function, extracellular products and blood supply.

Back 12

dense irregular CT and hyaline cartilage. Fibroblasts also present. Has both type I and type II collagen fibers but NO periosteum (not ENTIRELY avascular)

Location: annulus fibrosis of IVD, pubic symphysis, menisci, TMJ, triangular ligament between carpus and ulnar

Appearance: cotton candy like = type I collagen with chondrocytes in their lacunae

Function: provide compression and sheering resistance

EC products: type II collagen

Blood supply: no completely avascular

Front 13

Outline the steps in endochondral ossification.

Back 13

1. Overall: mesenchyme replaced by hyaline cartilage which then eventually becomes bone
2. Outside cartilage ossifies for form “bone collar”
3. Vessel invade the bone and create a cavity in shaft/diaphysis
4. Vascular region begins to ossify as cartilage matrix is replaced by bone and chondrocytes are replaced by osteocytes forming the primary ossification center
5. Vessels invade ends of long bones and repeat same process à secondary ossification center
6. Hyaline cartilage REMAINS at the articular surfaces and between epiphysis and diaphysis at the growth/epiphyseal plates

Front 14

In flat bones, mesenchyme transitions directly to become bone cells via

Back 14

intramembranous ossification

Front 15

List the five regions of the epiphyseal plate

Back 15

1. Zone of reserve cartilage (chondrocytes in lacunae)

2. Zone of proliferating cartilage (rows of isogenous groups)

3. Zone of hypertrophic cartilage (long rows of isogenous groups)

4. Zone of calcified matrix (calcium salts in the matrix)

5. Zone of resorption (cartilage in the bone cavity becoming ossified)

Front 16

Compare and contrast the inner and outer layers of the synovial joint capsule.

Back 16

1. Provide smooth movements between bones
2. Have colorless viscous fluid rich in hyaluronic acid and proteins
3. Outer layer of capsule: fibrous layer of dense CT that is CONTINUOUS with the periosteum of nearby bone
4. Synoviocytes: have prominent rough ER; secrete synovial fluid
5. Synovial macrophages: phagocyte cells to clear debris from joint
6. Enough force can cause inner layer to leak into the outer layer causing a great deal of pain

Front 17

Compare and contrast osteoprogenitor cells, osteoblasts and osteocytes from each other in terms of their appearance, function, location and origin

Back 17

osteoprogenitor cells: carried by arteries that create primary and secondary sites of ossification

- Found on the inner layer of the periosteum

- Enlarge to BECOME osteoblasts

- Osteoblasts: lay down ECM and become encases within their OWN lacunae à osteocytes

Front 18

List the components of bone matrix and outline how the matrix becomes mineralized.

Back 18

Osteoblasts become active = Release osteoid (un-mineralized matrix)

- A lot of type I collagen with small amounts of proteoglycans & multiadhesive glycoprotiens

- Once surrounded by matrix à osteocytes which can release type I collagen

Osteocytes concentrate Ca+2 by releasing alkaline phosphates into ECM - Increased amount of phosphate ions à draw MORE Ca+2 to site

Enzymes initiate crystallization of HYDROXYAPATITE - Serve as a reservoir for Ca and Phosphate which hormonal signals can control the breakdown and deposition of the mineralized matrix of bone

Front 19

Outline how osteoclasts degrade bone matrix and how the ruffled border, resorptive bay and extracellular space are involved in the process

Back 19

Osteoclasts: responsible for removing bone in LARGE quantities

Large, acidophilic, multinucleated and have a brushy surface in contact with bone

From the same stem cells as monocytes and macrophages which are phagocytic cells

Seal off region of bone directly UNDER them called the resorption bay (Howship’s lacuna) where they will be removed

Ruffled border: large # of Cytoplasmic extensions on cell appears like a fuzzy layer. Increases the surface area of cell

Clear zone: around periphery of cell. Contains circular area actin filaments that SEAL the resorptive bay from the extracellular space

Important to seal because in the sealed area, the pH is LOWERED to 4-5 by pumping out H into bay. Low pH dissolves hydroxyapatite crystals into Ca and phosphate ions while matrix metalloproteases and other enzymes break down collagen and proteins

Then endocytose digested material and release it into EC space

Front 20

Outline how parathyroid hormone & calcitonin influence blood calcium levels and bone density.

Back 20

PTH: released by cells in parathyroid gland when serum Ca is LOW = Increases osteoclast activity, osteocytic osteolysis, Ca absorption in small intestine and more

Calcitonin: released by cells in thyroid gland in response to HIGH Ca levels = Inhabits bone resorption by osteoclasts and osteocytes

Front 21

Outline/describe the function of osteoclasts and osteoblasts in bone remodeling and how cutting and clearing cones create new osteons

Back 21

Osteocytes lay down materials on nearby collagen WITHOUT organization (woven bone)

- Waves of osteoclasts tunnel though one and osteoblasts follow behind.

- Osteoblasts produce osteoid and encase themselves in a ring

- - - Additional “waves” repeat same process until you get multiple rings of mineralized matrix, each containing multiple rings of osteocytes, fill in the tunnel, leaving a small HOLE in the center for vessels/nerves = Stronger than woven bone now

Front 22

List the structures included in an osteon

Back 22

1. Osteocytes in lacuna
2. Canaliculi: processes that the osteocytes use to communicate with neighboring osteocytes and end in gap junctions
3. Osteal canal

Front 23

List the structures in compact bone and how blood flows through it

Back 23

Network of osteons connected to each other by their blood supply running through

- osteal (central/Haversian) canals = run parallel to the bone

- Perforating (Volkmann’s canals) = Run perpendicular and connect to Haversion canals

Disruption of blood supply = avascular necrosis

Front 24

Compare and contrast spongy and compact bone.

Back 24

1. Surrounds spongy bone
2. Located immediately deep to periosteum
3. Forms trabecular mech in the interior
4. Open region in spongy bone holds marrow – fat, and hematopoietic cells
5. Laid out in a specific way that provides the most support to bone

Front 25

Outline the process of healing a bone fracture

Back 25

- Immediate hemorrhaging of blood

- Neutrophils, macrophages begin to remove blood and debris

- Capillaries and fibroblasts grow INTO area and form loose CT to rejoin fragments = Replaced by a callus of hyaline cartilage

- Periosteal cells differentiate into osteoblasts that form a bone collar around callus

- Osteogenic buds invade cartilage to create callus of immature bone

- Remodeling replaces immature bone with lamellar bone and completed 6-12wks

Front 26

Describe auricular hematomas

Back 26

1. hematoma between the perichondrium and cartilage in elastic cartilage of the ear
2. cartilage of the ear loses its only bloody supply from the periosteum around it because of trauma leading to replacement of cartilage t dense irregular CT

Front 27

Describe Meniscal tears

Back 27

1. menisci of knee are fibrocartilage structures to stabilize and cushion (sheer and compressive resistant)
2. excessive stress causes meniscus tear. The thick outer region of each meniscus has blood supply while the narrow inner regions DO NOT

Front 28

Describe Achondroplasia

Back 28

Early closure of the growth plates fur to FGF receptor mutation

Large head with midfacial hypoplasia and prominent forehead

Short limbs, especially in proximal segments

Front 29

Describe Pseudoachondroplasia

Back 29

Similar presentation to achondroplasia but because of mutation that KILLS chondrocytes, also causes premature closure of growth plates

Front 30

Describe Gigantism

Back 30

Excessive growth hormone à growth plates hypertrophy = extreme size

Occurs BEFORE the growth plates close so they look proportional

Acromegaly - caused by excessive GH after growth plates have closed. s/sx adults buying progressively bigger shoes, Increase in weight, no increase in height

Front 31

Describe osteoarthritis

Back 31

1. presents as joint pain that becomes WORSE with activity and is relieved by REST.
2. Poster injury, other inflammatory factors active and prevent cartilage from fully regenerating
3. Clefts can develop in the articular cartilage leading to leakage and entrance of different substances including matrix metalloproteases and inflammatory cells
4. You find cartilage and type II collagen in the once clear synovial fluid

Front 32

Describe eburnation

Back 32

occurs when articular cartilage wears away and underlying bone is “polished” as its worn away

Front 33

Describe rheumatoid arthritis

Back 33

1. Autoimmune reaction making antibodies to synovial tissue
2. Causes synovial macrophages to release pro-inflammatory factors and [MMPs] matrix metalloproteases
3. Long term inflammation à destruction of the synovial lining, thickening of the capsule, and deformity of the joints
4. Occurs systematically and bilaterally = Usually seen at metacarpal phalangeal joints
5. Better with exercise and worse with rest

Front 34

Describe Rickets & Osteomalacia

Back 34

Too little Ca in diet OR lack of Vit D (required to absorb Ca in small intestine) = poorly mineralized bone

Bones cannot accommodate as much force à lower limbs warp under body weight (bow legged appearance but the actual bone is curved abnormally)

Front 35

Describe Osteoporosis

Back 35

1. PTH, inflammatory signals INCREASE activity of osteoclasts = Estrogen INHIBITS this process
2. Decrease in estrogen removes the inhibition of osteoclasts > decrease bone density because osteoclast activity becomes greater than osteoblast activity

Front 36

Describe Osteopetrosis

Back 36

Mutations in enzymes that allow osteoclast to function

Internal remodeling of bone does not occur > thick, but brittle woven bone

No osteon architecture

Front 37

Describe Osteogenesis Imperfecta

Back 37

Autosomal dominant disorder affecting all racial/ethnic groups

Structural or quantitative defects in type I collagen, the main type of connective tissue found in bone.

Clinical features: Fragile bones, blue sclera, early deafness