Pathology 2 Flashcards
What are the forms of repair?
Regeneration and scarring
What’s regeneration?
Repair with the growth of fully functional tissue to replace injured or dead tissue
What is required for total pure regeneration?
An intact connective tissue scaffold or only superficial injury (so it’s rare)
What’s a superficial injury?
Only affects epidermal or epithelial layer
Scarring replaces injured/dead tissue with ______.
Fibrous tissue lacking the specialized function of the tissue it replaces
What’s the most common scenario of wound repair?
A regeneration/scarring combo
Removal of one kidney causes _______. Is this regeneration?
Hyperplasia and hypertrophy of the remaining kidney, which doubles in size. Nope, not regeneration.
Removal of one lobe of the liver causes ______. Is this regeneration?
Hyperplasia and hypertrophy of the remaining lobe, which generate the same volume of fully functional liver tissue as pre-removal. Yep, regeneration.
What’s an ulcer?
A local defect in the surface of an organ or tissue produced by shedding of inflamed necrotic tissue
What’s an erosion?
Superficial sloughing of mucosa (or epidermis)
T or F: Ulcers are too deep to heal by regeneration.
T
What’s an adhesion?
An abnormal connection between any two things in the body
Early on, adhesions are composed primarily of _____. What is this called?
Fibrin, fibrinous
Later on, adhesions are referred to as _____.
Fibrous
What’s a fistula?
An abnormal opening between two places in the body
T or F: Fibrous adhesions are an inevitable side-effect of surgery.
T
What’s a common complication of fibrous adhesions?
Intestinal obstruction
_________ cells have self-renewal capacity.
Stem
Stem cells undergo ____ replication.
Asymmetric: in every division, one daughter cell retains self-renewing capacity and the other enters a differentiation pathway to a mature cell.
What are pluripotent stem cells?
They can give rise to any tissue
T or F: Adult stem cells can give rise to any tissue.
F: Limited number of tissues
What is the replicative capacity of labile cells?
They continuously lose cells and replace them by proliferation of mature cells and stem cells
What are examples of labile tissues?
Skin and linings of the mouth GI tract Bladder Vagina Cervix Uterus Fallopian tubes Exocrine gland ducts Bone marrow
What is the replicative capacity of stable cells?
They’re composed of cells capable of proliferation, but they’re not normally called on to proliferate
What are examples of stable tissues?
Liver Kidney Pancreas Smooth muscle tissues Blood vessel linings Fibroblasts
What is the replicative capacity of permanent cells?
They don’t proliferate except under extraordinary circumstances
What are examples of permanent tissues?
Parenchymal cells of the brain and heart (neurons and cardiac myocytes)
Which tissues are particularly vulnerable to radiation injury?
Continuously proliferating labile tissues
Erythema
Redness
Pruritis
Itching
Desquamation
Sloughing
Side effects of radiation
- Skin: erythema, pruritis, desquamation, loss of hair
- Chest/Abdomen: vomiting, nausea, diarrhea
- Bone marrow: Leukopenia
The process of healing is orchestrated by _____.
Growth factors
What does EGF stimulate?
Fibroblast migration and proliferation
What does FGF stimulate?
Fibroblast migration and proliferation
Monocyte chemotaxis
Angiogenesis
What does PDGF stimulate?
Fibroblast migration and proliferation
Monocyte chemotaxis
(more prevalent early in the process)
What does TGF-beta stimulate?
Fibroblast migration and proliferation
Monocyte chemotaxis
Collagen synthesis
T or F: TGF-beta is more prevalent early in the repair process.
F: more prevalent later in the process
What growth factors mediate monocyte chemotaxis?
PDGF, FGF, TGF-beta
What growth factors mediate fibroblast migration and proliferation?
PDGF, EGF, FGF, TGF-beta
What growth factors mediate angiogenesis?
FGF and VEGF
What growth factors mediate collagen synthesis?
PDGF and TGF-beta
What comprises the extracellular matrix?
Basement membrane and interstitium
Where is the basement membrane of the ECM?
Right underneath the epithelium and around blood vessels
What’s the interstitium of the ECM?
Supporting tissue between epithelium and vessels and between cells in connective tissue
What does the interstitium of the ECM contain?
Fibrillar collagen, fibrillin, elastin, hyaluronic acid, and proteoglycans
Which types of collagen are fibrillar?
I, II, III, and V
Review time! What’s the general structure of collagen?
3 polypeptide chains braided into a ropelike triple helix
What strengthens fibrillar collagen?
Lateral cross links
What are characteristics of the classical form of Ehlers-Danlos syndrome?
- A disease that causes defective type V collagen, leading to hypermobile joints and hyperextensible skin
- Autosomal dominant
What are characteristics of the vascular type of Ehlers-Danlos syndrome?
- It causes defective type III collagen, which is prevalent in blood vessels and bowel wall
- Autosomal dominant
What are characteristics of the kyphoscoliotic type of Ehlers-Danlos syndrome?
- It’s due to deficiency of lysyl hydroxyls enzyme, which impairs the cross linking of type I and III collagen
- Results in crooked spines
- Autosomal recessive
Fibrillin is secreted by ______ and is a major component of _____.
Fibroblasts, microfibrils
Microfibrils serve as scaffolding for the deposition of ________, an integral component of elastin.
Tropoelastin
What are the characteristics of Marfan syndrome? :(
- Caused by defects in the fibrillin gene
- Long body, long limbs, fingers, and toes
- Aorta prone to rupture
Loss of microfibrils leads to _____.
Excessive TGF-Beta
What is being evaluated as treatment for Marfans?
ARBs (angiotensin receptor blockers) that inhibit the activity of TGF-Beta, which is in excess in Marfan syndrome
What enzymes catalyze the formation of the covalent bonds cross-linking fibrillar collagen? What cofactor is needed?
Prolyl hydroxylase and lysyl hydroxylase; Vitamin C
What happens in vitamin C deficiency?
It weakens blood vessels, resulting in bleeding and poor wound healing
What pattern of inheritance do genetic defects in structural proteins tend to have?
Autosomal dominant
What pattern of inheritance do genetic defects in enzymes tend to have?
Autosomal recessive
What’s granulation tissue?
Healing tissue with residual chronic inflammatory cells, cellular debris, fibroblasts, neovascularization, and new collagen
What does granulation tissue look like?
Red or pink, soft, and granular
What are the number 1 and 2 features that are most characteristic of granulation tissue?
- Angiogenesis
2. Proliferating activated fibroblasts
What makes granulation tissue soft?
The new blood vessels of early granulation are leaky and the fluid that leaks out of them makes granulation tissue soft
What makes granulation tissue hard?
Replacement of granulation tissue by scar
What is organization?
The process replacing injured, necrotic, and inflamed tissue by healing and scar tissue
Who’s the key player in the process of organization?
Fibroblast
What’s the order of cell appearance in skin wound inflammation and healing?
- Neutrophils
- Macrophages
- Fibroblasts
- Lymphocytes
What’s the order of cell appearance in MI inflammation and healing?
- Neutrophils
- Lymphocytes
- Macrophages
- Fibroblasts
What do macrophages do in skin wounds?
Come early, peak fast, and leave fast
What do macrophages do in MI?
Come late, peak slowly, and persist for weeks
What’s angiogenesis?
The formation of new blood vessels in healing tissue, tumors, and atherosclerosis
What mediates angiogenesis?
VEGF (which also increases vascular permeability, endothelial migration, and proliferation)
How does angiogenesis work in skin wounds?
Starts early, peaks soon, and dissipates fast
How does angiogenesis work in MI?
Begins simultaneously with fibroblast infiltration on day 4, and persists for weeks
What are the phases of skin wound healing?
Inflammation
Proliferation
Maturation
When does healing by first intention occur?
When wounds are clean, uninfected, and have their edges approximated by sutures
When does healing by second intention occur?
In larger wounds with commonly irregular edges
In healing by first intention, on what day do all the playas come in?
1: Neutrophils
2: Epithelial cells
3: Macrophages
4: Fibroblasts
5: Granulation, angiogenesis
7-14: Collagen
What happens in healing by second intention?
- A larger blood clot fills the space of the wound
- More intense inflammation and more granulation tissue
- Wound contraction by myofibroblasts
- Scar formation
- Tissue remodeling
- Thinning of epidermal layer
The third phase of healing is a matter of ______.
Tissue remodeling, which alters the cellular content and extracellular matrix
What is the “high point” of healing?
The proliferative phase (middle phase)