Exam #2: Connective Tissue Flashcards
Migratory Cells in Connective Tissue
- Plasma Cells
- Leukocytes (Neutrophils & Monocytes)
Fixed Cells in Connective Tissue
- Fibroblasts
- Myofibroblasts
- Adipocytes
- Mast Cells
- Macrophages
What are the four functions of connective tissue?
1) Structure
2) Defense/ Protection
3) Nutrition
4) Cushion & Insulation
What is the most undifferentiated type of a connective tissue cell? What are they derived from?
- Undifferentiated mesenchymal cell
- Mesoderm & neural crest cells
What cell types can an undifferentiated mesenchymal cell become?
- Chondroblast = cartilage
- Adipocyte= Fat
- Fibroblast= Collagen/ ECM
- Osteoblast= Bone
Characteristics of an Active Fibroblast
- Euchromatic nucleus
- rER= very intense basophilic cytoplasm
- Golgi Apparatus
- Mitochondria
- Many processes that increase SA
Characteristics of an Inactive Fibroblast
- Decreased volume
- Less rER
- Less robust Golgi
- Heterochromatic nucleus
What is the effect of cortisol on fibroblasts?
- Cortisol decreases the activity of fibroblasts & decreased synthesis of connective tissue elements
- Degradation of connective tissue elements including bone (osteoporosis)
How do the nuclei of inactive fibroblasts differ from active fibroblasts?
Inactive fibroblasts have a very prominent basophilic nucleus because they are heterochromatic
How do fibroblasts change in wound healing?
1) Much more active
2) Greater tendency to divide
3) Light (euchromatic) & more spherical nucleus
4) Multinucleated
5) More robust cytoplasm
What important steps of collagen formation occur in the rER?
1) Formation of triple helix
2) Vitamin C dependent hydroxylation of prolyl & lysyl residues (Scurvy)
What is the function of collagen pro-peptides?
Maintain the solubility of the structure
What contains the procollagen peptidases that cleave pro-collagen into collagen?
ECM
Myofibroblast
- Possess characteristics of fibroblast & smooth muscle
- Contains actin & myosin for contractile activity
- Become more numerous in wound healing
Dupuytren’s Contracture
- Microvascular ischemia of the palmar aponeurosis leads to increased activity of fibroblasts & myofibroblasts
- Increased type III collagen synthesis occurs
- Type III collagen cross links with myofibroblasts
- Type III collagen/ myofibroblast cross-links lead to contracture of digits 4 &5
How do white adipocytes appear in a micrograph?
- As signet rings (the large space is where the lipid droplet was)
- Nucleus is located in the periphery
- Stippling seen is vimentin
What is vimentin?
Intermediate filament of adipocytes
Leptin
- Hormone synthesized by adipocytes that indicates satiety
- Mutation in leptin leads to morbid obesity
Lipodystrophy
- Disorders that affect the distribution of fat on the body
- Can be caused by a defect in Lamin (intermediate filament associated with the nucleus)
How do brown adipocytes differ from white adipocytes?
- Multilocular (multiple fat droplets per cell) vs. Unilocular
- Nucleus is centrally located vs. peripheral
- Acidophilic b/c of a large volume of mitochondria
What is the function of brown fat cells?
Production of heat, especially in newborns
What is the signature feature of mast cells?
Metachromatic granules
Characteristics of Mast Cells
- Metachromatic granules
- Large centrally located nucleus
- Packed with secretory granules (histamine, heparin, chemotaxic factors)
Histamine
Vasodilation
Leukotryenes
Produce bronchoconstriction & incude vaso-permability that is typical of anaphylaxis
What induces mast cell to release their contents?
Fc Receptor binding to antigen/antibody complex
What cell type are macrophages derived from?
- Monocytes
- Monocytes migrate into the connective tissue and morph into macrophages
What are the different types of marcophages?
- Microglia (CNS)
- Kupffer Cells (Liver)
- Alevolar Macrophages (Lung)
- Osteoclasts (bone)
Characteristics of Macrophages
- Centrally located nucleus with indentation
- Well developed Golgi
- Lysosomes
Giant Cell
- Fusion of macrophages in response to chronic inflammation
- Horseshoe nuclei appearance in some
What are conditions that would cause chronic inflammation?
- IBS
- TB
- Arthritis
- Autoimmune Disorders
What cell type do plasma cells originate from?
B-lymphocytes
What is the function of plasma cells?
Secretion of antibodies
Characteristics of Plasma Cells
- Basophilic cytoplasm (rER synthesizing antibodies)
- Clock Face Nucleus (Euchromatin central, Heterchromatin peripheral)
- Large Negative Golgi (packaging antibodies)
- NO SECRETORY VESICLES (constitutive release of antibodies)
Describe the leukocyte response to inflammation of heart tissue.
1st wave= neutrophils in the first day
2nd wave= monocytes that become macrophages on second day
What are the two types of embryonic connective tissue?
1) Mesenchyme
2) Mucous
What are the types of proper connective tissue?
1) Loose (areolar)
2) Dense, which can be regular or irregular
What are the different types of specialized connective tissue?
1) Adipose
2) Reticular
3) Cartilage
4) Bone
5) Blood
Mesenchymal Connective Tissue
Least differentiated form of connective tissue
Contains:
- Fibroblasts
- Type III Collagen (Reticular Fibers)
- Ground Substance
How does mucous connective tissue differ from mesenchymal connective tissue?
- More differentiated
- Contains Type I & Type III Collagen vs. Type III only
Where is loose/ areolar connective tissue found?
Immediately deep to the epithelium & surrounding blood vessels
Structure of Loose CT
- Loose array of Type I Collagen
- Reticular Fibers/ Type III Collagen
- Elastic Fibers
- Many cell types seen
Where is dense regular collagenous connective tissue found?
Tendons & Ligaments
Structure of Dense Regular Collagenous CT
- Type I Collagen arranged parallel (densely)
- Elongated nuclei of fibroblasts seen occasionally
- Don’t see many cell types b/c of tight collagen packing
What is the hallmark feature of mucoid degeneration of the ACL on MRI?
“Celery Stalk” Appearance
Where is dense regular elastic connective tissue found?
- Ligamentum flava
- Suspensory Ligament of the Penis
- Vocal Ligament
Structure of Dense Regular Elastic CT
- Elastin forms sheets of membranes
- Few collagen fibers are found
- Fibroblasts are trapped between
Where is dense irregular connective tissue found?
- Organ capsulses
- Dermis of skin
- Around sleeves of nerves
Structure of Dense Irregular CT
- Type I Collagen packed along different axes
- Elastic fibers interspersed
- Scattered Fibroblasts
Ehler’s Danlos Syndrome
Defect in Type I Collagen
Where is reticular tissue found?
- Red bone marrow
- Liver
- Lymphatic Tissues/ Organs
Xanthoma
Accumulation of lipid in tissue
How would a xanthoma appear histologically?
- Foam cells
- Macrophages that attempt to rid the body of cholesterol take on a foam-like appearance
