block III: CT video 3 Flashcards
By what is the adult CT proper classified by?
subdivided based upon
size and number of fibers and types and number of cells present into:
-Loose CT (subdividion of Loose cellular CT)
-Dense irregular CT
-Dense regular CT (subdivided into:
1. Dense regular collgaenous CT
2. Dense regular elastic CT
Mention the characteristic of loose CT
- Small diameter collagen
fibers - Large numbers of cells
- Abundant ground substance
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Examples of both loose CT and dense irregular CT in mammary gland
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Loose CT from lamina propia layer of esophagus
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Loose cellular CT in lamina propria of small intestine exrremely cellular. Very few fibers, but large numbers of cells related to immune function
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Higher magnification micrograph of loose cellular CT in lamina propria
of small intestine
by what is dense irregular CT characterized bye?
- Large diameter collagen fibers
- Fibers more closely packed together than in loose CT
- Relatively smaller numbers of cells than in loose CT
- Smaller amount of ground substance than in loose CT
- Fibers run in all different directions and are not preferentially ordered.
Where do we find dense irregular CT?
areas requiring greater strength of
the CT, for example as in the reticular area of the dermis or the capsules of organs
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Mammary gland showing regions of dense irregular CT; trichome stain
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dense irregular CT
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dense irregular CT
What is dense regular collagenous CT composed of?
collage fibers
What is dense regular elastic CT composed of?
elastic fibers
Where is dense regular collagenous CT found?
Is present in tendons and collagenous ligaments and the
cornea
How is dense regular collagenous CT different than dense irregular CT?
Similar to dense irregular CT, but
fibers are large & very tightly packed
and have an ordered parallel
arrangement (allowing movement; maximum amount of mechanical fiber)
What structure is considered dense regular collagenous CT?
The stroma of the cornea with
alternating layers of orthogonally
arranged collagen fibers
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EM of section through cornea showing regular alternating layers of collagen fibrils. dense regular collagenous CT
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Micrograph of section through a tendon; dense regular collagenous CT
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Elastic fibers stained in wall of aorta; Dense regular elastic CT
what are some examples of Dense regular elastic CT?
- The elastic lamellae in the wall of elastic arteries are often considered to represent dense regular elastic CT
- Also find in some elastic ligaments such as ligamenta flava associated with the spinal column
What are some fucntions of dense regular elastic CT?
- allows to expand
- allow wall of artery to maintain the pressure
- recoil, elastic pressure
What characteristic does Messenchymal CT have?
Mainly mesenchymal cells with an
extracellular matrix of GAGs and hyaluronic acid
What characteristic does Mucoid CT have?
has fibroblasts in a very gelatinous
ground substance with numerous small collagen fibers.
Found in umbilical cord as Wharton’s
jelly
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Mesenchymal connective tissue.
Note the mesenchymal cells with few if any fibers in the extracellular space. This is the type of tissue which may develop into other mesodermal tissues and organs
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Mucoid (mucous) connective
tissue. This is at much lower magnification than the mesenchymal CT seen in Figure 4- 3A. The cells (labeled C in inset) are considered to be true fibroblasts. Note the
relatively abundant thin collagen fibers as compared to the mesenchymal CT
What type of cells are normally found in CT proper that are FIXED (resident)?
Derived from mesenchymal cells:
1. fibroblast
2. myofibroblast
3. adipocytes: fat cells
What type of cells are normally found in CT proper that are TRANSIENT (wandering)?
Origin usually in bone marrow:
1. mast cell
2. macrophage
3. plasma cell
4. numerous types of white blood cells [lymphocytes, monocytes, neutrophils, eosinophils, basophils]
which cell is found in most regions of CT and its function?
- fibroblast
- synthesis of all fibers (elastic fibers, reticular fibers and collagen fibers) and ground substance [GAG synthesis]
How does fibroblast look?
- mainly see nucleus with small amounts of cytoplasm around it
- rest of cytoplasm drawn out into long whip like processes
- content of organelles depends on level of synthetic activity. RER frequently swollen with product
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EM of two fibroblasts surrounded by collagen fibers composed of collagen
fibrils secreted by the fibroblasts
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Loose CT in the submucosa of small intestine. The arrows In both micrographs indicate the thin cytoplasmic processes of fibroblasts
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Loose CT in the submucosa of small intestine. The arrows In both micrographs indicate the thin cytoplasmic processes of fibroblasts
what are myofibroblasts?
similar to fibroblast but has more actin and smooth muscle proteins and is contractile; thus, having more contractile ability & similarity to smooth muscle cells
What does the actin bundles contain?
composed of α-smooth muscle
actin (α-SMA) and associated nonmuscle myosin) as well as
cytoplasmic dense bodies containing smooth muscle-like α-actinin.
when do myofibroblast proliferate?
After a wound these cells may
proliferate after about the 5th day and through interactions with the
extracellular matrix fibers and using
contractile force that they generate
help to close the wound. After the 2nd week of healing their number normally decreases in most cases.
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EM of myofibroblast
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showing fibroblasts green in color and myofibroblasts antibody labeled for smooth muscle actin (orange)
what is hypertrophic scar formation?
In some pathological conditions
continued remodeling by myofibroblasts causes hypertrophic scar formation, resulting in excessive connective tissue contracture
What can we found in palmar fibromatosis (Dupuytren’s disease)?
Extensive numbers of myofibroblasts are found in most contractive diseases of connective tissue (fibromatoses)
By what is palmar fibromatosis (Dupuytren’s disease) characterized by?
characterized by the thickening of palmar aponeurosis, which leads to progressive flexion contracture of the fourth and fifth digits of the hand
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Hand of a patient with Dupuytren disease
