Connective tissue is composed of _______ and ________
Cells (fibroblast, mast cell, etc.); extra cellular matrix (ground substance, fibers)
Functions of the connective tissue
1. Provide structural support
2. Serve as a medium for exchange
3. Aiding in defense and protection
4. Storing fat
Connective tissue can be classified as _______ or ______. It arises from __________ ___________ _____________
(Connective tissue) proper; specialized (connective tissue) -> [bone, cartilage, blood]; embryonic mesenchymal tissue
Can you spot the: fibroblast, macrophage, elastic fibre, collagen fibre, extra cellular matrix, fat cell/adipose/adipocyte, mast cell, plasma cell?
Function of fibroblast
Produce and maintain the ECM
Battle between immune and pathogen in connective tissue
Properties collagen fibres
Bundled, around 20 different types (numbered 1-20), type 1 most abundant
2 Different Types of Proper CT
Loose CT, Dense CT (subdivided into Dense Irregular CT and Dense Regular CT)
Composition Loose CT
- Loose arrangement of fibres and dispersed cells, embedded in gel like ground substance and tissue fluid (lamina Properia in mucus membranes)
- Visually: About 50/50 cells to ECM
Function Loose CT
- Link to epithelial tissue (many blood vessels), superficial fascicle (tissue deep to skin)
- Primary battle field between immune response, inflammation allergic reactions, battle between antigens, bacteria, etc.
Image Loose CT
Can you spot the: mast cell, collagen fibres (random arrangement a characteristic), lymphocyte, lumen of vein, fibroblast
Types of Dense CT
IRREGULAR and REGULAR.
Properties Dense CT
- More fibres, fewer cells than loose CT
- See fewer blood vessels compared to loose CT
Properties Dense Irregular CT
- Collagen fibres distributed randomly
- Found in all capsules of the body, and in the dermis
Properties Dense Regular CT
- Collagen fibres distributed in parallel bundles
- Found in tendons (muscle to bone) and ligaments (bone to bone)
The most abundant cell type in the CT is the __________. It synthesizes almost all of the ______ _____ ________.
Fibroblast; extra cellular matrix
Shape of fibroblast
- Elongated, long euchromatin nucleus, abundant RER, spindle shaped
How many phases are in the fibroblast? What is the difference between the two?
- Inactive/resting (fibrocyte) and active. Inactive is smaller compared to active.
- Active has matured organelles, cytoplasmic is basophilic.
- Inactive has immature organelles, cytoplasmic is weakly acidophilic
In the image can you spot the cytoplasmic membrane, nucleus?
- Collagen formed outside of the cell, monomers formed in the nucleus
- Nucleus: heterochromatin (dark), euchromatin (light)
- Signals produced when cytoplasms touch between fibroblasts
What is the main protein of the extra cellular matrix?
Collagen fiber. It is also the major protein in the body (30-35%)
Properties of the Collagen Fiber
- Flexible but strong & resistant to stretching
- Made up of fibrils which is made up of tropocollagen molecules (seen as triple helix), which is made up of procollagens (3 polypeptide chains)
Collagen Synthesis Steps
1. DNA is transcribed (to mRNA) in nucleus
2. mRNA is translated (to pre-procollagen)
3. Pre-procollagen will be modified (to procollagen) in RER
- At ends of procollagen chains, propeptides (usually aren't part of helix) added to prevent spontaneous formation collagen fibers in cell
4. Procollagen secreted to ECM by trans golgi network
5. Procollagen peptidases cleave propeptides to form tropocollagen
6. Newly formed tropocollagen molecules spontaneously self assemble to form fibrils
Types of Loose CT
Elastic, Reticular, Adipose
Can elastic CT stretch as much as collagen fibres?
No. They can also bend very easily
Composition Elastic CT
Core made of elastin (protein), surrounded by sheath of microfibrils. Jelly like core.
Where can you find Elastic CT?
Urinary system, lungs, skin, bladder, arteries (wall of blood vessels)
Composition Reticular CT
Made of Type III collagen (reticular fiber), ~ 100-150nm in diameter, major fiber component
Function Reticuluar CT
Forms architectural framework (stroma) of liver, adipose tissue, bone marrow, spleen, basement membrane
Where can you find mast cells?
- By blood vessels, as they use blood circulation to move. They are transient and want to move to the target organ.
- Found close to arteries and sites of inflammation b/c play a role in allergic reaction
Where do mast cells come from?
- The bone marrow
Physical characteristics mast cells
Large (20-30um) cells w/ large central spherical nucleus, lots cytoplasmic granules (histamine, heparin), processes (filopodia)
What are the roles of histamine and heperin?
- Formed in granules of mast cell
- Histamin and heperin both used in allergic reaction
- Heperin is an anticoagulent
Plasma cells are derived from _ _____________, and produce and secrete ____________
B lymphocytes; antibodies
Physical characteristics plasma cells
- Large (10-20 um) ovoid cells, eccentrically located nucleus, well developed RER, basophilic cytoplasm, clock face nucleus
- Really big golgi, pale area (very prominent, an identifier)
- Lack large secretory vesicles b/c always secreting antibodies
Where are plasma cells found?
Macrophages are derived from _____________
Monocytes (hematopoietic stem cells)
Function of macrophages
- Remove cellular debris
- Protect against foreign invaders
- Produce cytokines & growth factors
Physical characteristics macrophages
- 10-30 um
- Trapping cell -> pseudopodia/fallopodia
- Basophilic cytoplasm
- Abundant lysosomes and RER, well developed Golgi
- Cytoskeleton & large vesicles
- Indented eccentric nucleus
What are the macrophages in the liver called?
What are the 2 types of adipose tissue?
Unilocular (white), and multilocular (brown)
Where can unilocular tissue be found?
In subcutaneous layer throughout the body (richly vascularized)
Physical properties of white adipose tissue
- Contain 1 fat droplet.
- Cell membranes possess receptors for insulin, growth hormone, norepinephrine, glucocorticoids -> regulate uptake and release of fatty acids and glycerols
- Born w/ certain #, can't destroy # of white adipose tissue
Where can multilocular (brown) adipose tissue be found?
- In neck and inter-scapular region of infants (highly vascularized)
Physical properties of brown adipose tissue
- Numberous mitochondria -> rapid oxidation fatty acids (20x faster than white adipose tissue) -> increase body heat production (3x)
- More vascularized than white, higher metabolism
- Integrin (purple block): Attached to cytoskeleton. Made of microtubules & filaments to give shape of the cytoskeleton.
- Proteoglycans (dots): Bind collagen fibres together
- Glycoprotein (red line): Bind integrin to collagen fibres and proteoglycans
- Collagen fibres (blue line): Mostly Type 4 (also types 1 and 3)
- Basement membrane: Components of both epithelial and connective tissue. Made up of collagen fibres, proteoglycans, glycoproteins, integrin.