Cartilage & Bones Flashcards
1
Q
Cartilage Connective Tissue
A
- Avascular, supportive connective tissue
- Contains a lot of semi-rigid extracellular matrix that contains chondroitin sulfate, collagen, and elastic fibers
- 3 types of cartilage that help in supporting soft tissues, creating articulations and creating models for bone growth
2
Q
What are the 3 types of cartilage?
A
- Hyaline Cartilage
- Elastic Cartilage
- Fibrocartilage
3
Q
Chondroblast
A
- Cells that secrete the gel-like ground substance until they are surrounded by the extracellular matrix
- Ground substance contains chondroitin sulfate and hyaluronic acid
- Produce type 2 (predominant type) and type 1 collagen fibers
4
Q
What two types of collagen do Chondroblasts produce?
A
- Type 1
- Type 2 (predominant)
5
Q
Chondrocyte
A
- Mature chondroblasts (meaning chondroblasts that are completely surrounded by the matrix they produce) contained in bubble-looking structures called lacunae
- Once in lacunae they continue to help maintain the tissue and can undergo mitosis when needed
6
Q
What are Isogenous Groups?
A
Clumps of chondrocytes that are surrounded by lacunae
7
Q
Perichondrium
A
- Cartilage tissue that is not vascularized or innervated
- Surrounded by dense irregular connective tissue which supports this cartilage
- Outer part is composed of type 1 collagen and fibroblasts
- Inner layer contains mesenchymal cells which provide a source of chondroblasts
- Functions in providing strong but flexible support to the tissue it surrounds
- Located in the respiratory system (nose, larynx, trachea, bronchi), costal cartilages (ribs), the framework for most bones, epiphyseal plates of long bones, and articular surfaces
8
Q
What is the source of Chondroblasts?
A
The inner layer of perichondrium, specifically the mesenchymal cells
9
Q
Hyaline Cartilage
A
- Connective tissue that has a homogenous and semitransparent appearing matrix
- Typically found on articular surfaces or in trachea
- Contains type 2 collagen fibers within the extracellular matrix; Chondrocytes are in lacunae, do not have perichondrium surrounding if articular hyaline cartilage
- Histology: “glassy” appearance
10
Q
Territorial Matrix
A
- Component of Hyaline cartilage
- Matrix that immediately surrounds the chondrocyte in the lacunae
- Microscope: stains darker due to increased amount of proteins
11
Q
Interterritorial Matrix
A
- Component of Hyaline cartilage
- Surrounds the territorial matrix
- Microscope: stains lighter due to slightly different composition of the extracellular matrix
12
Q
Elastic Cartilage
A
- Type of connective tissue that contains elastic fibers within the gel-like extracellular matrix
- Chondrocytes are in lacunae with perichondrium surrounding the outside of the tissue
- Chondrocytes can be found in isogenous groups
- Provides flexibility while maintaining shape
- Located in external ear and epiglottis
13
Q
Where is elastic cartilage found in the body?
A
- External Ear
- Epiglottis
14
Q
Fibrocartilage
A
- Type of connective tissue
- Contains visible bunches of collagen (type 1) and has both fibrocytes and chondrocytes
- Chondrocytes are in lacunae and are often arranged in rows
- Fibroblasts (have long, thin nuclei) are associated with collagen areas, filling in areas between the chondrocytes
- Tissue has loose nature
- No perichondrium needed/seen
- Provides resistance to compressive forces
- Located in the intervertebral discs and pubic symphysis
15
Q
Where is Fibrocartilage found in the body?
A
- Intervertebral Discs
- Pubic Symphysis
- Meniscus
16
Q
Chondrogenesis
A
- Process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondrocytes and begins secreting the molecules that form the extracellular matrix
- Outer mesenchyme transitions into the perichondrium for support
17
Q
What are the two different methods cartilage use to grow after undergoing chondrogenesis?
A
- Interstitial growth
- Appositional growth
18
Q
Interstitial Growth of Cartilage
A
- the growth of the cartilage starting in the center of the cartilage tissue
- chondrocytes undergo mitosis within the lacunae creating two cells; these cells begin to secrete matrix, pushing them apart; chondrocytes eventually end up in a new lacunae, separated from each other
- process is limited by the avascular nature of the tissue
19
Q
Appositional Growth of Cartilage
A
- growth in width occurring around the outer edges of the cartilage with the assistance of the perichondrium
- perichondrial mesenchymal cells, located in the chondrogenic layer of the perichondrium, undergo mitosis; new cells develop into a chondroblast that starts secreting matrix (collagen and ground substance) near the perichondrium
- results in buildup of cartilage around the edges of the tissue
20
Q
Cartilage Repair
A
- Repair is limited due to the avascular nature
- Sometimes the cartilage is replaced by dense connective tissue or bone
21
Q
Bone Connective Tissue
A
- Functions in providing support and protection for the body, and acts as the bodies calcium reserve
- Extracellular matrix is heavily mineralized (calcium) resulting in a solid tissue
- Matrix includes type 1 collagen fibers, proteoglycans, glycoproteins (1/3 of the overall tissue), and inorganic minerals
- Located within the organs of the skeletal system
- Has support tissue surrounding it that is called the periosteum (superficially) and endosteum (deep)
- 3 main cell types found here: osteoblast, osteocytes, osteoclast
22
Q
What is the name of the support tissue that surrounds bone?
A
(1) Periosteum (superficial layer)
(2) Endosteum (deep layer)
23
Q
Osteoprogenitor Cell
A
- Originates from mesenchyme
- Differentiates into the osteoblast
- Located in the periphery of the bone tissue – the periosteum and the endosteum
24
Q
Osteoblast
A
- Cell that secretes the ground substance Osteoid
- Secreted osteoid is covered by hydroxyapatite which makes the bone connective tissue hard – mineralizes the bone
25
Osteocyte
- Mature osteoblast cells
- Surrounded by the matrix within the lacunae -- some undergo apoptosis
- Help maintain the tissue and communicate with other cells to ensure tissue is functioning properly
- Cells have long processes that help interconnected cells and transport material
26
Osteoclast
- Monocytes that fuse to break down bone connective tissue for remodeling
- Active (remodeling is occurring) when there are microfractures or if the body needs calcium (process is called resorption)
- Cell first breaks down the hydroxyapatite then the collagen
- Located in depressions called Howship's Lacuna which is also known as the subosteoclastic acidic compartment
27
Periosteum
- Located on the outside/superficial surface of a bone
- Made up of two layers that support and maintain bone tissue
- The most superficial layer is made of dense irregular connective tissue; allows the anchoring of tendons, ligaments, blood vessels and nerves to the bone that are held in place by fibers that run perpendicularly into the bone called perforating (sharpey's) fibers
- Inner layer contains osteogenic cells which help maintain and grow the bone; innervated and vascularized
28
Endosteum
- Connective tissue that lines the internal bone tissue (marrow cavity or osteon's central canal)
- Contains osteogenic cells
- Associated with capillaries to supply the underlying bone connective tissue
- Not as thick as the periosteum
- Does not serve as an anchor point
29
Compact Bone (Cortical Bone)
- Found on the outside of long bones and on the superficial surfaces of flat bones
- Solid and dense
- Provides structure to the bone
- Covers the less dense spongy bone
- Made up of highly organized bone connective tissue with osteons as the main subunit
30
Osteon (Haversian System)
- Concentric ring/cylindrical structure that makes up the solid tissue of the cortical bone
- Runs parallel to the shaft of the long bone
- Contains several distinct features including the central canal, concentric lamellae, lacuna, canaliculi, and interstitial lamellae
31
Central Canal (Haversian Canal)
- Found at the center of the osteon
- Contains blood vessels, lymphatics, and nerves
- Provides the pathway for nutrients needed for bone connective tissue to work properly
- Lined with endosteum
32
Concentric Lamellae
- Mineralized extracellular matrix produced by the osteoblast
- Encircles the central canal
- Fibers run differently in each layer, giving it a tree-like appearance; this fiber structure also provides additional strength to the bone connective tissue
33
Lacuna
- Holes that are present within the concentric lamellae
- Contain osteocytes which help maintain the bone connective tissue
34
Canaliculi
- Tunnels that run between the lacunae and the central canal
- Connects the osteocytes for communication, and provides a path for nutrient and waste movement
- Cells send projections through the tunnels within the matrix, providing a spider-like appearance under the microscope
35
Interstitial Lamellae
- Remnants of old osteons within the compact bone
- As the tissue grow and repair, osteons are broken down when/where needed
- Some parts of the osteon remain to help hold the tissue together
36
Circumferential Lamellae
- Large rings of bones around the entire circumference of the long bone on the external and internal aspects
- Created by osteoblasts from the inner layer of the periosteum or the endosteum
- Perforating fibers of the periosteum anchor into the outer lamellae
37
Perforating Canal (Volkmann's Canal)
- Channels that run perpendicular to the osteons; run from the periosteum or the endosteal surface and bring blood vessels into the bone connective tissue (osteon)
- Interconnect with the vessels in the osteon's central canal
38
Spongy Bone (Trabecular Bone, Cancellous Bone)
- Found on the inside of bones surrounded by compact bone
- Does not develop osteons
- Made up of varied bars/plates of bones called trabeculae; these form along lines of stress to provide strength to forces applied to the bone
- Lamellae are put down by the osteoblasts but not in a visually recognizable pattern; once finished osteoblasts transition to osteocytes in lacuna (or undergo apoptosis)
- Cancaliculi run towards the endosteum for the maintenance of the bone
- Marrow (red or yellow) fills in between the bars of bones
39
Osteogenesis (Ossification)
- Process of bone formation
- Starts around the 8th week of gestation and continues into adulthood
- Two types can occur that both start with mesenchyme: in one method the mesenchyme transitions into the bone connective tissue (intramembranous), in the other method it transitions first to hyaline cartilage and then to bone (endochondral)
- After intramembranous or endochondral ossification occurs, the products are transformed into woven bone first then mature lamellar bone
40
Woven Bone (Immature Bone, Primary Bone, Bundle Bone)
- Bone that is placed more haphazardly for a quick repair or initial growth (not in rings or lamellae)
- Collagen is in a looser arrangement, has lower calcification, and contains more cells
- Remodeled over time into lamellar bone
- Histology: collagen fibers arranged randomly
41
Lamellar Bone (Mature Bone, Secondary Bone)
- Mature form of bone
- Contains a structure that has been placed and modified to meet the needs of the bone (along lines of force)
- Takes longer to build because of its more organized nature
- Histology: sheets/layered bone matrix
42
Intramembranous Ossification
- Bone tissue growth occurs directly from the mesenchyme that forms the shape of the bone being created
- Mesenchyme arranges itself in sheets -> mesenchymal cells differentiate into osteoblasts -> bone connective tissue is laid down -> woven bone tissue is remodeled to create the lamellar form
- Layer of mesenchyme that surrounds the bone tissue develops into the periosteum and functions in supporting new bone
- This type of ossification includes the bones of the skull and clavicle
43
Endochondral Ossification
- Bone connective tissue growth occurs after a hyaline cartilage model of the bone is formed
- Mesenchymal cells create the shape of the future bone -> cells differentiate into chondroblasts which create the hyaline bone model; the surrounding mesenchyme differentiates into the perichondrium to support the cartilage -> blood vessels come into the hyaline model and trigger bone tissue transition to begin (perichondrium -> periosteum; woven bone remodeled to create the lamellar form of the bone)
- Process used by the body to form the majority of bones
44
Diaphysis
- Shaft of the bone
- Long, cylindrical
- Contains bone marrow (red which is myeloid or yellow which is fatty) within the medullary cavity (hollow in the center of the bone)
45
Epiphysis
- Knob-like, rounded area that is present at the proximal and distal ends of long bones
- Articulation with other bones occurs here
- Articulation surface is covered by articular cartilage (hyaline cartilage) to allow the bones to interact smoothly without damage
46
During growth, the __ is separated from the ___ by the cartilaginous growth plate
- Epiphysis
- Diaphysis
47
Articular Cartilage
- Hyaline cartilage at the articular surface of the bone remains after endochondral ossification to create a smooth articulation surface; this tissue never becomes bone, instead it protects the bone at the joint allowing for protection and smooth movement between bones
- No perichondrium is associated with this tissue
- Avascular and not innervated so it receives supplies from an external source (ex. synovial fluid)
48
Metaphysis
- Area between the diaphysis and the epiphysis
- Where growth occurs
- During growth, this part of the long bone contains the hyaline cartilage of the epiphysial plate; once growth finishes it transitions into bone connective tissue and is called the epiphyseal line; this line disappears over time and remodeling, and the metaphysis won't be distinct from the other areas of the long bone
49
Epiphyseal Plate
- Some of the hyaline cartilage remains from the endochondral bone model at the metaphysis; this allows the endochondral ossification to continue as the person ages to increase the length of the bone (interstitial growth)
50
What are the 5 zones present in the hyaline cartilage in the metaphysis (epiphyseal plate) during interstitial growth?
- Zone of reserved cartilage
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcification
- Zone of ossification
51
Zone of Reserved Cartilage (Zone of Resting Cartilage)
- Layer of the hyaline cartilage adjacent to the epiphysis
- Helps keep the growth plate attached to the epiphysis
- Not active in the growth process
52
Zone of Proliferation
- Chondrocytes in this area undergo rapid cell division creating one cell stacked on another
53
Zone of Hypertrophy
- Where the chondrocytes begin to expand and secrete chemicals to initiate blood vessels to enter the area
54
Zone of Calcification
- Extracellular matrix of the cartilage begins to calcify here
55
Zone of Ossification
- Located nearest to the diaphysis
- Osteoprogenitor cells brought in by the blood vessels transform into osteoblasts and begin producing bone; it lays down woven bone first then remodels it to lamellar bone
56
Bone Repair
- Occurs when mature (lamellar) bone is damage
- Steps: body forms a collagen-based callus to fill in the gap in the bone -> osteoblasts come in and form bone connective tissue -- woven bone -> over time the normal maintenance and function returns so the bone can be remodeled into the appropriate type of tissue (cortical or spongy)
57
Bone Remodeling
- During this process old osteons are reabsorbed by osteoclasts, creating tunnels in the bone connective tissue
- Blood vessels follow the tunnels and bring osteoprogenitor cells into the area; these become osteoblasts and begin forming the new osteon
Steps:
(1) Osteoblasts sense microcracks
(2) Osteoblasts produce RANKL
(3) RANKL binds to RANKL receptors on nearby monocyte precursor cells, and induces these cells to form osteoclasts
(4) Osteoclasts secrete collagenase which digests collagen protein in organic matrix; leads to formation of "pits" on bone surface called Howship's Lacunae, and release of Ca2+
(5) Osteoblasts also secrete Osteoprotegerin which binds to RANKL and prevents it from activating RANKL receptors, and they secrete Osteoid Seam which fills in the holes on the surface of the bone
58
Joint
- Where two bones meet each other
- Classified based on either their function and/or structure
59
Functional Classification of Joints
- Classification based on the movement that can occur where two bones articulate
- 3 classifications: synarthrosis, diarthrosis, amphiarthrosis
60
Synarthrosis Joints
- Immovable joints
- Can be fibrous or cartilaginous
- Ex. the sutures holding the bones of the skull together
61
Diarthrosis Joints
- Slightly movable joints
- Can be fibrous or cartilaginous
- Ex. where the ribs and sternum come together (movement allows breathing)
62
Amphiarthrosis Joints
- Joints that can move freely
- Synovial
- Often found in the appendicular skeleton (contains UE and LE)
63
Structural Classification of Joints
- Classification based on the type of tissue that is found associated with the bone articulation
- 3 classifications: fibrous, cartilaginous, synovial
64
Fibrous Joints
- Joint that uses dense connective tissue to anchor the bones together; "fixed" joints
- Ex. sutures that hold the bones of the skull together, gomphosis that hold the teeth in the jaw, interosseous membranes that hold the paired long bones of the arm and leg together
65
Cartilaginous Joints
- Joint that uses cartilage to join the ends of bones together; surrounded by hyaline cartilage
- Ex. synchondrosis between the first ribs and sternum or the epiphyseal plates, symphysis found between the vertebrae (intervertebral discs) or pubic bones
66
Synovial Joints
- The two bones that come together are surrounded by a joint capsule that is lined with a synovial membrane that produces synovial fluid (helps with lubrication and ease of movement between the two bones)
- Outer layer of synovial membrane is fibrous and is continuous with the periosteum
- Typically have accessory ligaments to support the structure and help keep bones together during overexertion
- Ex. hip joint, knee joint
67
What distinguishes cartilage from most other connective tissue?
It lacks blood vessels
(also lacks lymphatics and nerves, but is surrounded by dense connective tissue that is vascularized)
68
Feature that is typical of elastic cartilage:
Collagen is mainly type 2
69
What area in cartilage is relatively collagen-poor and proteoglycan rich?
Territorial Matrix
70
What is the source of progenitor cells activated for the repair of hyaline cartilage of accident-damaged costal cartilage?
Perichondrium
71
How does articular cartilage differ from most other hyaline cartilage?
It lacks a perichondrium
(perichondrium is not present with the hyaline cartilage of articular surfaces or epiphyses of growing long bones)
72
What component of bone impedes the distribution of nutrients and oxygen to osteocytes?
Extracellular Matrix
73
In healthy bone, canaliculi contains:
Osteocytic processes
(osteocytes communicate with adjacent cells via a network of long dendritic processes that extend through the matrix via narrow canaliculi radiating from each lacuna)
74
In the diaphysis of a typical long bone, what structure is closest in proximity to the trabeculae of cancellous bone?
Inner Circumferential Lamellae
(located around the marrow cavity)
75
Zone of endochondral ossification in a growing femur that is farthest from the bone's secondary ossification center (epiphysis):
Zone of Ossification
76
Structure where cells synthesize the major lubricant for diarthrotic joints:
Synovial Membrane
(membrane extends folds and villi into the joint cavity and produces synovial fluid)
77
Interstitial Growth of Bone
- type of growth that allows the bone to lengthen
- hyaline cartilage in the metaphysis (epiphyseal plate) can be divided histologically into several zones, each having a role in forming the bone connective tissue: zone of reserved cartilage, zone of proliferation, zone of hypertrophy, zone of calcification, zone of ossification
78
Appositional Growth of Bone
- type of growth that allows the diameter of the bone to become larger
- the osteoblasts within the inner layer of the periosteum secrete the matrix creating the circumferential lamellae; osteoclasts in the endosteum break down the inner cortical bone, increasing the size of the medullary cavity
79
Structure of Long Bone
- Outermost layer: composed of cortical bone that is made of osteons, which are made of many lamellae; center of each osteon contains a Haversian Canal (blood supply, nerve)
- Inner layer: Medullary Canal which is lined by spongy bone that contains bone marrow (mesenchymal stem cells and hematopoietic stem cells found here)
