Flashcards in Lecture 10: Connective Tissue I Deck (26)
What are some characteristics of connective tissue?
- Unlike epithelial tissues, connective tissues have relatively few cells.
- The major characteristic of connective tissues is an abundant matrix. - Connective tissue matrix contains varying amounts of protein fibers.
- Connective tissue is typically classified on the basis of the type of matrix, fiber density, and fiber organization.
What connective tissue is used in Embryos?
Wharton's Jelly. No idea what it is yet.
Name the 4 types of Adult Connective Tissues and describe each
1. Elastic - Elastic fibers predominate
2. Reticular - Reticular fibers predominate
3. Loose - Both collagen and elastic fibers are present and arranged in a very loose, random fashion.
4. Dense - Collagen fibers predominate (Subcategories: Regular, or Irregular)
Name the 4 special classes grouped in with connective tissue
4. Hematopoietic Tissue
Yeah, you know what time it is...review them fucking photomicrographs
I. Hate. Human. Beings.
Describe embryonic connective tissues
- Found in umbilical cord and in the pulp of developing teeth.
- Referred to as “Wharton’s” jelly in umbilical cord.
- Composed of some collagen and elastic fibers but mostly an abundance of extracellular matrix. (Review that tissue - Slide 12)
Describe Loose Connective Tissue
- Also called Areolar, high ratio of fibroblasts to fibrous components
- Type I collagen fibers and elastic fibers
- Usually found beneath epithelial tissues of most organs, including the tunica adventitia of blood vessels.
- Contains fibroblasts, mast cells, macrophages, and capillaries
- Review tissue on Slide 13 and 14
Describe Dense regular CT
-High ratio of fibrous components to fibroblasts
- Thicker bundles of collagen than in loose CT
- Dense regular connective tissue is characterized by highly ordered bundles of collagen separated by single rows of fibroblasts.
- Found in tendons and ligaments.
- Review Slide 15 & 16
Describe Dense Irregular CT
- High ratio of fibrous components to fibroblasts
- Thicker bundles of collagen than in loose CT
- Dense irregular connective tissue has no specific orientation of collagen bundles.
- Found in fascia, submucosa of GI tract, and in dermis of integument
- Review Slide 17
Describe and Compare Reticular CT to Elastic CT
1. Reticular CT:
- A type of dense irregular connective tissue with a predominance of reticular fibers.
- These are associated primarily with lymphatic tissue, they branch to form a network with the immune system (support role)
2. Elastic CT:
- A type of dense irregular connective tissue with an abundance of elastic fibers which form discontinuous lamellae.
- Associated with walls of blood vessels.
- Note that elastic fibers in walls of blood vessels are produced by smooth muscle cells rather than fibroblasts.
- Review Tissue Slide 19 - 20
What is unique about the CT special Classes?
These are not characterized by fibers, but have embryological similarities to adult connective fibers.
Describe Adipose tissue
-Adipocytes are derived from undifferentiated mesenchymal cells and are distinguished by their unique appearance. Most are about 150 micrometers in diameter.
- White fat is distributed throughout the body: Unilocular
- Brown fat cells contain numerous smaller lipid droplets: Multilocular
--Brown Fat has Slightly more cytoplasm and abundant mitochondria, which give them their brown coloration.
Review Slides 23-26
Describe the Connective Tissue Matrix
- Connective tissue proper consists of cells scattered in a relatively homogeneous matrix.
- Most common cells are fibrocytes and fibroblasts.
- Cells are covered in the next lecture.
- The matrix consists of protein fibers and ground substance.
- The most abundant fibers are collagen fibers.
- Other fiber types include reticular fibers and elastic fibers. •
- Ground substance is mostly composed of glycosaminoglycans and glycoproteins.
Collagen is the most abundant fiber in the body.
Describe the function and location of Collagen Type I, II, and IV
1. Type I: Found in General CT and bone. Function: Tensile Strength
2. Type II: Found in Hyaline and Elastic Cartilage. Function: Tensile Strength
4. Type IV: Found in Basement Membrane. Function: Meshwork and scaffolding
Describe Collagen Fiber Synthesis
* Type I collagen is synthesized as a prepropeptide. The signal (pre-) sequence is cleaved after translocation of the polypeptide into the endoplasmic reticulum (ER) lumen of the fibroblast. After the signal sequence is cleaved, the propeptide (procollagen) molecule is secreted by the fibroblast into the extracellular matrix.
* The procollagen molecule has terminal non-helical ends that prevent polymerization. These non-helical ends are cleaved by peptidases in order to allow polymerization to occur. After the terminal ends are cleaved, the molecule is referred to as tropocollagen.
* Tropocollagen monomers spontaneously assemble into staggered arrays to form collagen fibers with a characteristic 64 nm banded pattern. This assembled polymer is collagen.
- See Slide 32 for a visual
How are elastic fibers synthesized?
- Elastin is synthesized as a prepropeptide.
- The prepropeptide is secreted as a propeptide
- The propeptide is converted to tropoelastin by extracellular enzymes, also secreted by the fibroblast.
- Tropoelastin monomers are assembled into amorphous fibers or sheets with the aid of several types of fibrillins.
- See slide 36 for a visual
What are glycosaminoglycans?
- Glycosaminoglycans (GAGs) are large, negatively charged linear polymers (polysaccharides) consisting of repeated disaccharide units.
- GAGs were originally referred to as acid mucopolysaccharides.
- Along with glycoproteins, GAGs form most of the amorphous substances of connective tissue.
- All GAGs, except hyaluronic acid, are covalently linked to protein to form proteoglycans.
There are 4 types of glycosaminoglycans. Name the 4 categories.
1. Hyaluronic Acid
2. Heparin or Heparin Sulfate
3. Chondroitin Sulfate and dermatan sulfate
4. Keratan Sulfate
Describe Hyaluronic Acid
- Largest of the GAGs
- Cartilage, skin, synovial fluid, and general CT
- Only GAG which lacks sulfate groups.
- Consists of repeating carbohydrate chains of N-acetylglucosamine and D-glucuronic acid.
- Present in nearly all connective tissues and in vitreous body of eye, synovial fluid, and Wharton’s jelly.
- Binds readily with water and serves as a lubricant in synovial fluids.
Describe heparin and heparin sulfate
- Basement membrane, skin, lung, liver, blood vessels, mast cell granules
- Repeating unit is N-acetylglucosamine and D-glucuronic acid.
Chondroitin Sulfate and Dermatan Sulfate
- Cartilage, bone, skin, blood vessels, heart valves, cornea
- Most abundant of the sulfated GAGs.
- Repeating unit in chondroitin sulfate is N-acetylglucosamine and D-glucuronic acid.
- Repeating unit in dermatan sulfate is N-acetylglucosamine and iduronic acid.
Describe Keratan Sulfate
- Type I is found only in cornea.
- Type II is found in cartilage and nucleus pulposus of intervertebral disks
- Repeating unit is N-acetylglucosamine and galactose.
Visual for GAG is on slide 43
* Secreted products of resident cells:
- Fibroblasts, chondroblasts, osteoblasts, synovial cells, smooth muscle cells (all derived from the primitive mesenchyme).
* Stain with conventional dyes such as hematoxylin because of sulfate groups.
* Toluidin blue and crystal violet are cationic dyes that are metachromatic when reacting with the anionic groups of the proteoglycans.
- Glycoproteins are proteins with one or more heterosaccharide chains containing hexosamine, galactose, and other sugars.
- Glycoproteins are PAS+
- Main characteristics are high protein content and branched carbohydrate moieties.
What are some examples of glycoproteins?
1. Fibronectin: Major surface protein of fibroblasts. Synthesized also by epithelia and endothelia. Occurs in plasma (= cold-insoluble globulin or plasma fibronectin). Occurs in alpha granules of platelets. Links cells, collagen, and glycosaminoglycans
2. Chondronectin: Isolated from cartilage. Promotes adhesion of mature chondrocytes to collagenous substrates
3. Laminin : Found in basal laminae (component of lamina rara). Involved in the attachment of epithelial cells to the lamina propria. Noncollagenous glycoprotein