Cartilage & Bones Flashcards
Cartilage Connective Tissue
- 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
What are the 3 types of cartilage?
- Hyaline Cartilage
- Elastic Cartilage
- Fibrocartilage
Chondroblast
- 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
What two types of collagen do Chondroblasts produce?
- Type 1
- Type 2 (predominant)
Chondrocyte
- 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
What are Isogenous Groups?
Clumps of chondrocytes that are surrounded by lacunae
Perichondrium
- 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
What is the source of Chondroblasts?
The inner layer of perichondrium, specifically the mesenchymal cells
Hyaline Cartilage
- 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
Territorial Matrix
- Component of Hyaline cartilage
- Matrix that immediately surrounds the chondrocyte in the lacunae
- Microscope: stains darker due to increased amount of proteins
Interterritorial Matrix
- Component of Hyaline cartilage
- Surrounds the territorial matrix
- Microscope: stains lighter due to slightly different composition of the extracellular matrix
Elastic Cartilage
- 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
Where is elastic cartilage found in the body?
- External Ear
- Epiglottis
Fibrocartilage
- 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
Where is Fibrocartilage found in the body?
- Intervertebral Discs
- Pubic Symphysis
- Meniscus
Chondrogenesis
- 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
What are the two different methods cartilage use to grow after undergoing chondrogenesis?
- Interstitial growth
- Appositional growth
Interstitial Growth of Cartilage
- 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
Appositional Growth of Cartilage
- 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
Cartilage Repair
- Repair is limited due to the avascular nature
- Sometimes the cartilage is replaced by dense connective tissue or bone
Bone Connective Tissue
- 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
What is the name of the support tissue that surrounds bone?
(1) Periosteum (superficial layer)
(2) Endosteum (deep layer)
Osteoprogenitor Cell
- Originates from mesenchyme
- Differentiates into the osteoblast
- Located in the periphery of the bone tissue – the periosteum and the endosteum
Osteoblast
- Cell that secretes the ground substance Osteoid
- Secreted osteoid is covered by hydroxyapatite which makes the bone connective tissue hard – mineralizes the bone
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
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
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
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
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
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
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