Histology Ch. 5 Flashcards
Connective Tissue (107 cards)
1
Q
What is the primary function of connective tissue?
A
Provides a matrix supporting and physically connecting other tissues and cells to form the organs of the body
2
Q
What does the interstitial fluid of connective tissue provide to cells?
A
Metabolic support and serves as the medium for diffusion of nutrients and waste products
3
Q
What is extracellular matrix (ECM) composed of?
A
- Long protein fibers (collagen and elastic fibers)
- Ground substance (proteoglycans, glycosaminoglycans, multiadhesive glycoproteins)
4
Q
What is the origin of all connective tissues?
A
Embryonic mesenchyme
5
Q
Describe mesenchymal cells.
A
Undifferentiated cells with large nuclei, fine chromatin, prominent nucleoli, and spindle-shaped morphology
6
Q
What are myofibroblasts and their role?
A
Fibroblasts involved in wound healing with contractile function, enriched with actin
7
Q
What are the primary cells in connective tissue proper?
A
Fibroblasts
8
Q
What do fibroblasts synthesize and secrete?
A
- Collagen
- Elastin
- Glycosaminoglycans
- Proteoglycans
- Multiadhesive glycoproteins
9
Q
What distinguishes active fibroblasts from quiescent fibrocytes?
A
Active fibroblasts have larger, euchromatic nuclei and more abundant cytoplasm, while fibrocytes are smaller with heterochromatic nuclei
10
Q
What is the role of macrophages in connective tissue?
A
Phagocytic ability, turnover of protein fibers, and removal of apoptotic cells and debris
11
Q
How do macrophages contribute to the immune defense system?
A
Remove cell debris, neoplastic cells, bacteria, and present antigens for lymphocyte activation
12
Q
What triggers the activation of macrophages?
A
Infection or injection of foreign substances
13
Q
What are mast cells and their primary function?
A
Oval or irregularly shaped cells that release bioactive substances important in local inflammatory responses and tissue repair
14
Q
List some key substances released from mast cells.
A
- Heparin
- Histamine
- Serine proteases
- Eosinophil and neutrophil chemotactic factors
- Cytokines
- Phospholipid precursors
15
Q
Where are mast cells predominantly located?
A
Near small blood vessels in skin and mesenteries, and in mucosal tissues of the digestive and respiratory tracts
16
Q
What is the significance of mast cells in allergy?
A
Release mediators that promote immediate hypersensitivity reactions upon antigen appearance
17
Q
Fill in the blank: Connective tissue contains a large amount of _______.
A
Extracellular matrix (ECM)
18
Q
True or False: Fibroblasts are transient cells in connective tissue.
A
False
19
Q
What is adipose connective tissue primarily composed of?
A
Adipocytes (fat cells)
20
Q
What is the function of adipose tissue?
A
Cushioning and insulation of organs
21
Q
What role do macrophages play in tissue repair?
A
Secrete growth factors important for tissue repair and increase in number during inflammation
22
Q
What are the morphological characteristics of macrophages?
A
Eccentrically located oval or kidney-shaped nucleus, size varies, and highly developed phagocytic ability
23
Q
Where do mast cells primarily occur?
A
Near small blood vessels in skin and mesenteries, and in the tissue lining digestive and respiratory tracts
Mast cells serve as sentinels detecting invasion by microorganisms.
24
Q
What type of allergic reactions do mast cells promote?
A
Immediate hypersensitivity reactions
This includes conditions like anaphylactic shock.
25
What happens during the first exposure to an allergen?
Antibody-producing cells produce IgE that binds to mast cell receptors
## Footnote
This primes mast cells for subsequent exposure.
26
What triggers the rapid release of mediators from mast cells upon reexposure to an allergen?
Binding of antigen to IgE on mast cells
## Footnote
This leads to degranulation and release of histamine, leukotrienes, and chemokines.
27
What is the role of leukocytes in connective tissue?
They migrate from blood to connective tissue, especially during inflammation
## Footnote
This process enhances the immune response.
28
What are the main signs of inflammation?
Redness, swelling, heat, and pain
## Footnote
These are caused by increased blood flow and vascular permeability.
29
What are the three main types of fibers in connective tissue?
* Collagen fibers
* Reticular fibers
* Elastic fibers
30
What is the most abundant protein in the human body?
Collagen
## Footnote
It represents 30% of the body's dry weight.
31
What are fibrillar collagens?
Collagens that form large fibrils, notably types I, II, and III
## Footnote
They are visible in microscopy and provide structural strength.
32
What is the process of collagen synthesis?
Procollagen α chains assemble, hydroxylation and glycosylation occur, and the triple helix is formed
## Footnote
This occurs in the RER before secretion.
33
What is the significance of keloids?
Localized swellings caused by excessive collagen formation in scars
## Footnote
They are a clinical problem, especially in individuals of African descent.
34
What is chemotaxis?
The attraction of specific cell types by specific molecules
## Footnote
It increases leukocyte numbers in inflamed tissues.
35
What do plasma cells derive from?
B lymphocytes
## Footnote
They are responsible for antibody production.
36
What characterizes the cytoplasm of plasma cells?
Basophilic cytoplasm rich in rough endoplasmic reticulum
## Footnote
This is essential for antibody synthesis.
37
What is the life span of plasma cells?
10–20 days
38
What are the main functions of leukocytes?
* Immune response
* Phagocytosis
* Inflammation response
39
What role do fibroblasts play in collagen synthesis?
They secrete collagen and are involved in its assembly
## Footnote
Fibroblasts are the primary cells responsible for producing collagen.
40
What are the two main forms of collagen subunits?
* Homotrimeric
* Heterotrimeric
41
What stabilizes the triple helix structure of collagen?
Disulfide bonds and hydrogen bonds
## Footnote
These bonds are crucial for the structural integrity of collagen.
42
What is the diameter range of type I collagen fibrils?
20 to 90 nm
43
What is the characteristic feature of type I collagen visible by electron microscopy?
Transverse striations with a regular periodicity
## Footnote
This results from the staggered arrangement of collagen subunits.
44
What is the function of linking/anchoring collagens?
They link fibrillar collagens to one another and to ECM components
## Footnote
Type VII collagen is an example.
45
What feature is visible in type I collagen when observed by EM?
Transverse striations with a regular periodicity
## Footnote
This characteristic is due to the assembly of rodlike triple-helix collagen molecules.
46
How do type I collagen fibrils further assemble?
They form large, extremely strong collagen fibers that may be bundled by linking collagens and proteoglycans.
47
What is the primary characteristic of type II collagen?
It occurs as more delicate fibrils and does not form fibers or bundles.
48
What type of collagen is found in epithelial basal laminae?
Sheet-forming collagen type IV.
49
What appearance do collagen bundles have when filling the ECM?
They appear white.
50
What makes collagen fibers birefringent?
The highly regular orientation of subunits.
51
What color do collagen fibers stain with eosin in light microscopy?
Pink.
52
What is the role of collagenases in collagen turnover?
They degrade collagen fibrils or sheets to make them susceptible to further degradation by nonspecific proteases.
53
What is the main component of reticular fibers?
Collagen type III.
54
What characterizes the staining of reticular fibers?
They appear black after impregnation with silver salts and stain poorly with H&E.
55
What is the function of reticular fibers in connective tissue?
They form an extensive network for the support of many different cells.
56
What is the primary property of elastic fibers?
They have rubberlike properties allowing tissues to stretch and return to their original shape.
57
What proteins compose elastic fibers?
Fibrillin and elastin.
58
What is the role of hyaluronan in the ground substance of the ECM?
It forms a viscous, pericellular network binding a considerable amount of water.
59
Fill in the blank: GAGs are long polymers of repeating _______.
[disaccharide units].
60
What are the four major GAGs found in proteoglycans?
* Dermatan sulfate
* Chondroitin sulfates
* Keratan sulfate
* Heparan sulfate
61
What is a proteoglycan composed of?
A core protein with various numbers and combinations of sulfated GAGs covalently attached.
62
What is the significance of the negative charges in GAGs?
They produce extended conformations and cause GAGs to sequester cations and water.
63
True or False: Elastin is easily digested by most proteases.
False.
64
What is the condition associated with mutations in the fibrillin genes?
Marfan syndrome.
65
What role do fibroblasts play in collagen production?
They secrete collagen and are involved in the assembly of collagen fibers.
66
How does collagen turnover vary among different tissues?
Tissues like tendons and ligaments have stable collagen, while others like the periodontal ligament have high turnover rates.
67
What are glycoproteins that have multiple binding sites for cell surface integrins?
Multiadhesive glycoproteins
## Footnote
These glycoproteins allow adhesion of cells to their substrate.
68
What is the key proteoglycan found in all basal laminae?
Perlecan
## Footnote
Perlecan is essential for the structure of basal laminae.
69
What is the composition of aggrecan?
250-kDa core protein with chondroitin and keratan sulfate chains
## Footnote
Aggrecan is a large proteoglycan abundant in cartilage.
70
What role does hyaluronan play in embryonic mesenchyme?
It produces wide spacing of cells and a matrix ideal for cell migrations and growth
## Footnote
Hyaluronan is rich in water, aiding in tissue development.
71
What are some disorders caused by deficiencies in lysosomal enzymes for degrading GAGs?
Hurler, Hunter, Sanfilippo, Morquio syndromes
## Footnote
These disorders result in the accumulation of GAGs in tissues.
72
What is the function of hyaluronidase produced by certain bacteria?
It hydrolyzes hyaluronan and disassembles proteoglycan complexes
## Footnote
This reduces the viscosity of connective tissue, increasing bacterial invasiveness.
73
What are the main types of connective tissue proper?
Loose connective tissue and dense connective tissue
## Footnote
These types are classified based on the amount of collagen present.
74
What characterizes loose connective tissue?
Contains cells, fibers, and ground substance in roughly equal parts
## Footnote
It provides flexibility but not much resistance to stress.
75
What is the primary function of dense regular connective tissue?
Provides great resistance to prolonged or repeated stresses from the same direction
## Footnote
It consists mostly of parallel bundles of type I collagen.
76
What is edema?
Excessive accumulation of interstitial fluid in connective tissue
## Footnote
It occurs when capillary walls become more permeable during inflammation.
77
What two forces act on water in capillaries?
Hydrostatic pressure and colloid osmotic pressure
## Footnote
These forces regulate the movement of water between blood and interstitial fluid.
78
What is the primary source of nutrients for cells in connective tissue?
Capillaries
## Footnote
They also carry away metabolic waste products.
79
What is the role of integrins in connective tissue?
Act as matrix receptors for specific sequences on ECM proteins
## Footnote
Integrins allow cells to explore their environment while maintaining attachment.
80
What type of collagen characterizes reticular tissue?
Type III collagen
## Footnote
This collagen forms a delicate network supporting various cell types.
81
True or False: Fibronectin is a multiadhesive glycoprotein involved in cell migration and maintenance of tissue structure.
True
## Footnote
Fibronectin has binding sites for collagens and GAGs.
82
Fill in the blank: The degradation of proteoglycans is carried out by several cell types and depends on the presence of several _______.
lysosomal enzymes
## Footnote
These enzymes are crucial for degrading specific GAGs.
83
What is the primary cellular component in dense irregular connective tissue?
Fibroblasts
## Footnote
These cells are primarily responsible for producing collagen in this tissue type.
84
What are the characteristics of dense irregular connective tissue?
Randomly interwoven collagen fibers with no definite orientation
## Footnote
It provides resistance to stress from all directions.
85
What is the significance of focal adhesions in connective tissue?
They are structures formed by integrin–microfilament complexes
## Footnote
Focal adhesions allow cells to respond to the physical properties of the ECM.
86
What is the main function of laminin in connective tissue?
Provides adhesion for epithelial and other cells
## Footnote
Laminin is essential for the assembly and maintenance of basal and external laminae.
87
What are the best examples of dense regular connective tissue?
Tendons, aponeuroses, ligaments
## Footnote
These structures are characterized by densely packed parallel collagen fibers.
88
What creates a meshwork for the passage of leukocytes and lymph?
Reticular tissue
## Footnote
Reticular tissue includes macrophages and dendritic cells to monitor and remove debris.
89
What type of collagen forms reticular fibers?
Type III collagen
## Footnote
Reticular fibers stain irregularly and are abundant in lymphoid tissues.
90
What does mucoid connective tissue represent in the fetal umbilical cord?
Wharton’s jelly
## Footnote
It is gelatinous and composed chiefly of hyaluronan.
91
What is the primary component of the extracellular matrix (ECM) in connective tissue?
Extracellular material
## Footnote
Connective tissues consist primarily of ECM rather than cells.
92
What is the embryonic form of connective tissue called?
Mesenchyme
## Footnote
Mesenchyme contains uniformly undifferentiated cells in a gel-like matrix.
93
What are the major cells of connective tissue proper?
Fibroblasts
## Footnote
Fibroblasts synthesize and secrete most components of the ECM.
94
What specialized cells in connective tissue are responsible for triglyceride storage?
Adipocytes
## Footnote
Adipocytes are very large cells found in adipose tissue.
95
What type of cells differentiate from monocytes in connective tissue?
Macrophages
## Footnote
They function in ECM turnover and phagocytosis.
96
What do mast cells release during inflammatory reactions?
Vasoactive agents
## Footnote
Mast cells are filled with granules containing these substances.
97
What do plasma cells secrete abundantly?
Antibodies (immunoglobulins)
## Footnote
Plasma cells differentiate from B lymphocytes.
98
How many types of collagen are known?
Approximately 20 types
## Footnote
Collagen is the most important and abundant fiber in connective tissue.
99
What process involves hydroxylation of prolines and lysines in collagen synthesis?
Posttranslational modifications
## Footnote
These modifications occur in the rough endoplasmic reticulum (RER).
100
What type of collagen produces a network of delicate reticular fibers?
Type III collagen
## Footnote
These fibers are abundant in immune and lymphoid tissues.
101
What gives connective tissues their elastic properties?
Elastic fibers and elastic lamellae
## Footnote
These are composed of elastin and fibrillin.
102
What is the major component of ground substance in connective tissue?
Hydrated glycosaminoglycans (GAGs)
## Footnote
Ground substance is rich in GAGs, proteoglycans, and multiadhesive glycoproteins.
103
What are the major types of GAGs?
* Hyaluronan (hyaluronic acid)
* Chondroitin sulfate
* Keratan sulfate
## Footnote
GAGs are bound to core proteins of proteoglycans.
104
What is the classification of loose connective tissue?
More ground substance than collagen
## Footnote
Loose connective tissue surrounds small blood vessels and is adjacent to other epithelia.
105
What type of connective tissue has parallel bundles of type I collagen?
Dense regular connective tissue
## Footnote
This type is prominent in tendons and ligaments.
106
What type of connective tissue is abundant in lymphoid organs?
Reticular tissue
## Footnote
Reticular fibers form attachment sites for lymphocytes.
107
Mucoid tissue is primarily found around what structures?
Blood vessels in the umbilical cord
## Footnote
It is gel-like with few cells.
