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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

Function macrophage

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


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?

- Blood

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?

Kupffer Cells

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

Basement Membrane

- 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.

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