Connective Tissue Flashcards
(37 cards)
1
Q
White (Unilocular) Adipose Tissue
A
- Function as insulation and fat storage
- Composed of cells with single large fat droplet surrounded by thin rim of cytoplasm which contains nucleus
- Fat metabolized slowly
- Found in adults
1
Q
Elastic Fibers
A
- Form thin, branching, elastic networks; highly refractile in light microscope
- Unstained with eosin (can still be seen by adjusting condensor because it refracts light); Verhoeff’s stain - black; [resorcin fuschin - purple]
- Consists of core of elastin covered by microfibrillar glycoproteins
2
Q
Neutrophils
A
- Phagocytic cells that defend against infection; found in the connective tissue only during active infection.
- Have multi-lobed nucleus
3
Q
Loose/Areolar Connective Tissue
A
- Loosely interwoven network of fibers (predominately collagen fibers) that binds different tissue types together and provide support and cushioning for various structures.
- Contain relatively large amount of cells, ground substance, and tissue fluid
4
Q
Gycosaminoglycans (GAGs)
A
- Large, unbranched polymer of two disaccharides:
a. Negatively charged sugar acid
i. Glucuronic acid
ii. Iduronic acid
b. Neutral amino sugar
i. N-acetylglucosamine
ii. N-acetylgalactosamine - Polyanionic/High negative charge density due to carboxyl and sulfate groups
- Negative charge allows binding of water to form hydrated gel and determines consistency of ground substance
- Basophilic staining due to negative charge: hematoxylin - purple; aniline blue - blue; azure - metachromatically purple (intensity dependent on GAG concentration)
4
Q
Plasma Cells
A
- Cells derived from activated B lymphocytes and produce humoral (soluble) antibodies in the presence of a specific antigen.
- Polygonal cells with characteristic “clock face” nucleus
5
Q
Types of Ordinary Connective Tissue
A
- Mucous
- Fibrous
a. Loose/Areolar
b. Dense Irregular
c. Dense Regular
d. Elastic
6
Q
Basophils
A
Cells serve same function as mast cells (granules contain same substances); excessive degranulation can cause anaphylactic shock and death.
7
Q
Classifying Ordinary Connective Tissue
A
- Arrangement of fibers
- Chemical composition of ground substance
- Arrangement of cells
- Relative proportion of cells and matrix components
7
Q
Fibroblasts/Fibrocytes
A
- Produce collagen, elastin, GAGs and other components of extracellular matrix
- Fusiform cells with elongated nuclei
- Cytoplasm unstained to basophilic depending on level of protein synthesis
- Only permanent resident of connective tissue
7
Q
Macrophages
A
- Irregularly shaped cell with round/oval or indented nucleus
a. Can only be truly distinguished when filled with stained phagocytized material (e.g. carbon particles in India Ink) - Found throughout body as part of body-wide system of phagocytic cells, those that consume foreign molecules, cells, and components of dead cells
8
Q
Types of Connective Tissue
A
- Ordinary
- Adipose
- Reticular
- Vascular
- Cartilage - non-mineralized skeletal tissue with firm matrix
- Bone - skeletal tissue with very hard, mineralized matrix
8
Q
Pericytes
A
Undifferentiated epithelial cells associated with capillaries and serves as source of new endothelial cells; located inside basement membrane and bulges away from lumen
9
Q
Proteoglycan Aggregates
A
- Hyaluronic acid core with proteoglycans radiating outward, attached via linker proteins
- Associate with collagen fibrils
10
Q
General Functions
A
- Structural Support
a. Holds together tissues of body and connects them into functional whole - Metabolic Support
a. Medium for diffusion of nutrients and waste products to and from cells
b. Fat cells store nutrients and provide insultion against heat loss - Defense
a. Physical barrier to free movement of microorganisms
b. Environment for immune system to destroy foreing organisms and substances
12
Q
Dense Regular Connective Tissue
A
- Fibers packed tightly in parallel arrays, oriented in same direction or in layers with fibers in each layer oriented in same direction but different from adjacent layers
- Connects different tissues and is resistant to stretching (high tensile strength)
- Contains relatively large amount of fibers, fewr and less variety of cells (flattened with elongated nuclei), and reduced amount of ground substance
- Found in tendons, ligaments, and aponeuroses
13
Q
Cells of Connective Tissue
A
- Fibroblasts/Fibrocytes
- Macrophages
- Endothelial Cells
- Pericytes
- Plasma Cells
- Smooth Muscle Cells
- Adipocytes
- Nerves and Nerve Endings
- Mast Cells
- Blood Cells
a. Lymphocytes
b. Eosinophils
c. Basophils
d. Neutrophils
15
Q
Reticular Fibers
A
- Composed of Type III collagen with large amounts of associated carbohydrates/sugar groups (4%)
- Form fine, branching threadlike fibrils (20 nm diameter), arranged in a loose, mesh-like network
- Silver (black); PAS (magenta); does not stain with H&E
16
Q
Types of Collagen
A
Differences in AA sequence of alpha chains results in various polymerized forms and tissue distribution.
- Type I (most abundant)- fibril; bone, skin, tendons, organs
- Type III - fibril; reticular fibers in CT of organs, smooth muscle, blood vessels, nerves, etc.
- Type IV - sheet-like; basal lamina
- Type VII - anchoring fibrils between basal lamina and CT in stratified squamous epithelia
17
Q
Tissue Fluid
A
- Derived from fluid portion of blood (water, salts, nutrients, signaling molecules, and other small molecules)
a. Fluid from blood forced out of capillaries (designed to leak) through basement membrane into ECM due to hydrostatic pressure, while larger molecules kept in blood
b. Greater concentration of blood proteins increases colloid osmotic pressure drawing fluid from ECM back into venules
c. Excess fluid drained by lymphatic vessels into venous circulation - Maintains hydration of ECM/tissues; brings nutrients, gases, signalling molecules to cells and removes waste and cellular products
19
Q
Reticular Connective Tissue
A
- Forms a three-dimensional scaffold for cells in blood-forming and lymphoid tissues
- Composed of reticular fibers
21
Q
Brown (Multilocular) Adipose Tissue
A
- Functions to provide heat
- Composed of polygonal cells with multiple fat droplets and numerous mitochondria
- Fat metabolized rapidly with heat production
- Found in infants and hibernating animals
22
Q
Types of GAGs
A
- Hyaluronic Acid
- Sulfated GAGs
a. Chondroitin-4-sulfate
b. Chondroitin-6-sulfate
c. Heparan sulfate
d. Keratan sulfate
e. Dermatan sulfate
24
Q
Proteoglycans
A
- Consists of core protein with GAGs attached, radiating outward
25
General Composition
1. Cells
a. Produce and maintain fibers and ground substance of extracellular matrix
b. Carry out various biological functions
2. Extracellular Matrix
a. Fibers - long protein filaments (collagen main fibrillar component)
b. Ground Substance - large macromolecules made of proteins and carbohydrates
c. Tissue Fluid - derived from blood
25
Collagen Fibers - Structure
1. Alpha chains are polypeptide building blocks
a. 1/3 Glycine
b. Hydroxyproline found only in collagen and formed by enzymatic hydroxylation of proline
2. Procollagen - 3 Alpha chains assembled into a triple helix
3. Collagen molecule (Tropocollagen) - formed by enzymatic cleavage of ends of procollagen (300 x 1.5 nm)
4. Collagen fibril - formed by end-to-end and side-to-side association of collagen molecules; 68 nm banding pattern
5. Collagen fibrils form collagen fibers
6. Collagen fibers form fiber bundles
26
Ground Substance
1. Homogenous, semi-fluid material (viscous to nearly solid) that fills space between fibers of connective tissue
a. Decrease in ground substance with age causes thinning of CT (wrinkling)
2. Provides hydrated medium for diffusion of nutrients, wastes, and gases, while filtering large particles (bacteria)
3. Chemical Composition
a. Proteoglycans and proteoglycan aggregates
b. Glycosaminoglycans (GAGs)
c. Water
28
Endothelial Cells
Simple squamous epithelial cells that form lining of blood vessels and lymphatic vessels.
29
Dense Irregular Connective Tissue
1. Composed of collagen fibers arranged in a dense, strong, yet still flexible, interwoven network
2. Provide support to tissues
3. Contains relatively large amounts of fibers, fewer and less variety of cells (flattened with elongated nuclei), and reduced amount of ground substance)
4. Found in dermis of skin, organ capsules,and septa [periosteum, perichondrium, etc.]
30
Elastic Connective Tissue
1. Elastic fibers predominate
2. Can store energy under stretching and recoil to return tissue to its original shape
3. Found in walls of blood vessels and intervertebral ligaments
31
Collagen Fibers - Properties
1. Flexible and high tensile strength
2. Characteristic 68 nm banding pattern in electron microscope due to staggering of collagen molecules
3. Stained with acidic dyes: eosin - pink; aniline blue - blue
32
Collagen Fibers - Synthesis and Assembly
1. Synthesis (Intracellular)
a. Synthesis, glycosylation, and formation of procollagen within rough ER
b. Packaging in Golgi
c. Secretion in vescicles
2. Assembly (Extracellular)
a. Enzymatic cleavage of procollagen and assembly of fibrils in extracellular "coves"
b. Assembly of fibers and bundles in extracellular space
33
Mast Cells
1. Contain basophilic granules with heparin, histamine, SRS-A, ECF-A)
2. Degranulation: IgE antibody binds to antigen, and IgE-antigen complex binds to receptors on surface of mast cells, causing vescicles of granules to fuse with plasma membrane and release contents into ECM
a. Inc. smooth MM contraction (inc. hydrostatic pressure) and more leaky capillaries = inc tissue fluid --\> causes edema
b. Inc. smooth MM contraction also restricts air passages in lungs --\> causes difficulty breathing
34
Mucoid Connective Tissue
1. Cells and ground substance predominate; relatively few fibers
2. Found in umbilical cord (Wharton's jelly) and embryonic mesenchyme
35
Lymphocytes
Responsible for cellular immunity; common in loose connective tissue; thin rim of cytoplasm and round, deeply staining (heterochromatic) nucleus
36
Eosinophils
1. Cells responsible for defense against parasites and fungi and counteracting the effects of basophil and mast cell substances
2. Common in loose CT
3. Have eosinophilic granules and bi-lobed nucleus (often folded into a circle)
37
Types of Adipose Tissue
1. White Adipose Tissue
2. Brown Adipose Tissue
