Lecture 10 Connective Tissue, Bone and Cartilage Flashcards
Connective Tissue
Embryonic
Adult
Special
Adult CT 4 Types
Loose
Dense
Reticular
Elastic
4 Types of Special CT
Adipose
Cartilage
Bone
Hematopoietic
Type 1 Collagen Fibers
General CT and bone
tensile strength
Type II Collagen
Hyaline and elastic cartilage
tensile strength
Type III collagen
Parenchyma of organs and walls of blood vessels
Reticular framework
Type IV collagen
Basement membranes
Meshwork, scaffolding
Collagen Fiber Synthesis
- Type I collagen is synthesized as a prepropeptide
- The signal (pre-) sequence is cleaved after the translocation of the polypeptide into the ER lumen
- Pro-collagen molecule is secreted through exocytosis
- Tropocollagen - after secreted, altered into this. This self-assembles into collagen
- Collagen
Elastic Fiber Synthesis
Elastin is also synthesized as a prepropeptide
Secreted as a propeptide
Converted to tropoelastin - final component of elastin assembly
Assembled into amorphous fibers or sheets with the aid of fibrillin
Tropoelastin
Final component of elastin assembly
Fibrillin
Assembles tropoelastin into amorphous fibers or sheets
Fibroblasts and fibrocytes
Principal cell types found in connective tissue. They are also most numerous cells found in CT
-secrete and maintain connective tissue
Secretion and maintenance of CT matrix
Secrete precursor fibrous molecules
Secrete the amorphous components of the matrix, including the glycosaminoglycans
Glycosaminoglycans
GAGs
Large, negatively charged polysaccharides consisting of repeated discaccharide units.
GAGs fall into 4 groups
- Hyaluronic acid (cartilage, skin, synovial fluid and general CT)
- Heparin and heparan sulfate
- Chondroitin sulfate and dermatan sulfate
- Keratan sulfate (cartilage, cornea and intervertebral disk)
Adipocytes
Fat cells 150 micrometers in diameter 2 Types 1. White fat 2. Brown fat
White fat
Distribute through the body
Unilocular - large droplet of fat
Brown fat
Cells contain numerous smaller lipid droplets
Multilocular
Slightly more cytoplasm
Abundant mitochondria, give them coloration
3 Major classes of cartilage
- Hyaline cartilage
- Elastic
- Fibrocartilage
Hyaline Cartilage
Most common type of cartilage Avascular Contains type II collagen fibers Surrounded by perichondrium Translucent, bluish gray Solid but flexible Chondrocytes are often found in cell groups
Hyaline Cartilage Growth Pattern
Appositional - add new onto existing
Interstitial - New
Elastic Cartilage
Specialized by addition of elastic fibers to the matrix
Surrounded by perichondrium
Yellow color because of presence of elastic fibers
More opaque, flexible and elastic than hyaline cartilage
Chondrocytes mostly located singly
Type II collagen plus elastic fibers
Found in -Auricle of ear
-epiglottis
Fibrocartilage
Increased collagen in the matrix Reduced cellularity compared to hyaline Not surrounded by perichondrium Opaque appearance from fibrous texture Type I collagen Single sparse chondrocytes
Fibrocartilage Locations
Intervertebral discs
Pubic symphysis
Insertion of some tendons and ligaments
Closely associated with dense connective tissue or hyaline cartilage
Avascular
Slow to heal
Bone characteristics
A canalicular system
Vascular
Elongation through appositional growth
Continuous resorption, reconstruction and remodeling
Bone is formed by osteoblasts which become osteocytes
2 Types of Matrix
- Osteoid - organic
2. Hydroxyapatite - inorganic
3 Types of Bone
- Woven
- Compact (aka lamellar)
- Spongy (aka trabecular or cancellous)
Compact Bone
Lacks cavities and forms dense plate on the outside of long bones or flat bones
Consists of concentric (Haversian) lamellae which encircle a central blood vessel
Trabecular (Spongy) Bone
Has a 3-D lattice of branching, bony spicules intertwined to form trabeculae surrounding the bone marrow spaces in the long bones and flat bones
