Histology - Connective Tissue - Reverse Flashcards
Abundant cells, euchromatic nuclei & with lots of cytoplasmic processes. Abundant ground substance. Few, if any, reticular fibers.
Mesenchyme
Scattered cells with heterochromatic nuclei. Fair amt ground substance. Clearly visible fibrils and fibers.
Mucous Connective Tissue
- Loose (areolar) (LCT) 2a. Dense irregular 2b. Dense regular 3. Reticular tissue
Connective Tissues Proper Types
Primarily beneath epithelium, LOTS of cells, fair amt of ground substance. Loosely arranged ECM, “woven mat”. Site of immune responses.
Loose (areolar) connective tissue (LCT)
Clear spaces, multidirectional. Fewer cells, much less ground tissue. Large bundles of collagen fibers oriented in multiple directions.
Dense Irregular Connective Tissue (DiRCT)
Fewer cells, box car nuclear arrangement, unidirectional. Little ground substance. Collagen fibers: Large bundles oriented in one direction.
Dense Regular Connective Tissue (DRCT)
Stroma of liver, spleen, bone marrow, lymph nodes, endocrine organs
Reticular Tissue Location
LOTs of cells, Meshwork of delicate specifically stained, black fibers (silver-stained). LOTs of open spaces for lymph, blood, or cells to move through. “Chicken-wire” appearance.
Reticular Tissue Features
Highly cellular, packed, surrounded by delicate ECM of reticular fibers. Not polarized or joined by tight junctions, not contractile, and do not conduct impulses. Mesenchymal origin.
Adipose tissues
Throughout body, large round oval cells, appear white. Long term energy homeostasis.
White Adipose Tissue
Multilocular adipocytes that are smaller and appear vacuolated. Heat-generation. Found mostly in infants (back, neck, shoulders) and adults around organs.
Brown Adipose Tissue
structural framework, harnesses muscle contraction into movement, scaffolding of gland and organs, medium for metabolic exchange, protection, fat storage.
Conective Tissue Support Functions
Clear, gel-like substance of varying density depending on water content that occupies the space between the cells & fibers. Usually lost with histological processing, so appears empty. Composed of Glycosaminoglycans, Proteoglycans and their aggregates, and multiadhesive glycoproteins.
Ground substance
Repeating, mostly sulfated, disaccharide units.
Glyscosaminoglycans (GAGs)
Core protein (I) + GAGs (-). Sulfated GAGs give them a high negative charge that attracts Na+ and thus water, forming a hydration shell. Present in ALL CTs, purposeof hydrating ECM.
Proteoglycans (PGs)
A core component of cartiledge ECM. Individual PG’s indirectly bound to hyaluronan (re-enforced by link protein) creating giant macromolecules that attract large volumes of water, giving ECM gel-like “shock- absorbers”.
Proteoglycan Aggregates
Charge-based filtration barrier
Primary function of GAGs & PGs in BM
Multidomain and multifunctional molecules that stabilize the ECM assembly and link it to the CT.
Multiadhesive glycoproteins (MGPs)
Fibronectin, Laminin, Tenascin, Osteopontin, Entactin/Nidogen
Multiadhesive glycoprotein examples
Elastic, Collagen, Reticular
ECM Fiber Types
Typically thinner than collagen fibers and often arranged in a branching patter. Look like “rubber bands” that have stretched then recoiled. Permit tissues to be stretched and then recoil. Found in skin, large blood vessels, lung walls.
Elastic fibers
Orcein
Specific stain for elastic fibers
Surround and permeate elastic fibers, helping to organize their growth.
Fibrillin microfibrils
Most abundant structural component (30% of dry weight of the body). Imparts tensile strength to tissues. Flexible but not elastic.
Collagen
Fibrillar (I, II, III), Sheet-forming (IV), Anchoring (VII).
Collagen types
All fibrillar collagens mature to fibril stage, but not all go on to form fibers or fiber bundles. Tropocollagen molecule to fibril to fiber to fiber bundle.
Fiber bundle assembly
mature collagen molecule
Tropocollagen molecule
orderly alignment of tropocollagen molecules
Fibril
90% of collagen, provides tensile strength and is only fibrillar collagen that can form fibrils, fibers & bundles. Widely distibuted (dermis, bone, ligaments, tendons, joint capsules, muscle, nerve, sclera of eye, scar tissue).
Type I Collagen
Less common, found in cartilage and vitreous humor. Provides tensile strength and restrains PG aggregate expansion.
Type II Collagen
slender fibrils, no bundling.
Type II Collagen TEM appearance
Heavily glycosylated. Fibrils only. First collagen laid down in embryo and after an injury.
Type III Collagen: Reticular fibers
Surround: Adipocytes, smooth muscle fibers, prepheral nerve fibers, small blood & lymph vessels (microcirculation). Also a major component of the reticular lamina that underlies the basal lamina.
Reticular fiber distribution
Forms a delicate latticework (network) providing support for organs that: 1. filter blood or lymph (spleen, lymph nodes) 2. Have rich microvasculature (liver, GI tract, encocrine organs) and 3. Have rapidly changin populations of proliferating cells (bone marrow).
Reticular fiber function
Monomers form flat sheet-like meshwork. No fibrils (no periodicity). Found in basal lamina (epithelium) and external lamina (muscle & nerve). Provides support (epithelium) and filtration.
Type IV Collagen (basal lamina)
Anchoring, non-fibrillar. Anchors basal lamina to reticular lamina.
Type VII collagen
From mesenchyme, which is sourced from mesoderm and neural crest. Mesenchyme-like cells, retained in adult CTs are source of stem cells.
Connective Tissue Embryonic Origins
Fribroblast, Chondrocyte, Adipocyte
CT Cell Types
Benign: lipoma. Malignant: Liposarcoma
Adipocyte Tumor (benign and malignant)
Benign: Chondroma. Malignnant: Chondrosarcoma
Chondrocyte Tumor (benign and malignant)
Principal CT cell. Synthesizes & secretes all ECM components.
Fibroblasts
Numerous cells in close proximity, cell structure reflects intense synthetic activity, gwoth or repair within 2 hours after injury. Secrete type III collagen. Later replace type II with type I.
Fibroblast (activated)
Quiescent fibroblast. Fewer cells, more widely dispersed. Reduced activity, ECM maintenance.
Fibrocyte
Protein-secreting cell containing bundles of actin filaments (contractile). Most active during 1st week (2nd week: undergo apoptosis). Generate & maintain steady contractile force (approximate tissues) Assist with synthesis & secretion initial ECM (quick repair).
Myofibroblasts
Arise from monocytes (white blood cell) after migration from blood into CT, whereafter they are considered resident CT cells.
Macrophages
- Host response to injury: Inflammation. 2. Host defense.
Macrophage functions
Large cells, eccentric nuclei, pften appear vacuolated
Macrophage LM appearance
Features of a phagocytic cell
Macrophage TEM appearance
When macrophages encounter large foreign bodies, they may fuse to form a very large cell. These very large cells engulf or “wall-off” the foreign body.
Foreign Body Giant Cells
Preformed chemical mediators of inflammation. Secrete Cytokines & Leukotrienes. Skin, Respiratory & GI systems.
Mast cells
Anticoagulant mast cell. (a GAG).
Heparin
A mast cell that promotes increased vascular permeability, intense smooth muscle contraction, and mucus secretion by nasal & bronchial glands.
Histamine
Most common type of fat cell. Large, spherical cells with eccentric nucleus and thin rim of cytoplasm that synthesize and store lipids as TAGs for energy and secrete hormones, growth factors, and cytokines.
Unilocular Adipocytes
(brown) fat cells located in brown adipose tissue. Function: Heat generation (thermogenesis)
Multilocular Adipocytes
- Develop elsewhere (bone marrow) 2. Migrate into CT’s to perform their functions 3. Short-lived: White blood cells and Plasma cells
Transient Cells
Oval-shaped cell (tear drop), Eccentric nucleus, Prominent nucleolus, Heterochromatin distributed in “Clock-face or Cartwheel” pattern.
Plasma cells: LM Appearance
Comprises the functional parts of an organ. Liver = hepatocytes.
Parenchyma
The connective, supportive framework of a biological cell, tissue, or organ.
Stroma
Epithelium + Lamina propria
Mucosa
Simple columnar with brush border + goblet cells
Epithelium
Ground Substances
Glycosaminoglycan, Proteoglycans, Multiadhesive Glycoproteins
Marfan’s Syndrome
- Problem with elastic fibers. Test w/ Steinberg test (Make a fist w/ thumb inside) and Walker-Murdoch sign (Thumb to pinky around wrist).
- Dilation of ascending aorta and aortic arch.
Osteogenesis Imperfecta
a congenital bone disorder characterized by brittle bones that are prone to fracture because of a deficiency of Type-I collagen.
Provides Tensile strength and Restrains Proteoglycan Aggregate expansion
Type II Collagen
A disorder of bone growth characterized by short stature (dwarfism) with other skeletal abnormalities and problems with vision and hearing caused defects in making type II collagen.
Kniest dysplasia
Ehlers-Danlos Type IV
Characterized by thin, translucent skin; easy bruising; characteristic facial appearance (in some individuals); and arterial, intestinal, and/or uterine fragility caused by abnormalities in production of _type III reticular fibers. _
Sheet forming collagen, supports and anchors the epithelium and provides filtration. Loacted at Basal Basal Lamina of Epithelium and External Lamina of Muscle and Nerves. No fibrils, no periodicity.
Type IV Collagen
Hermaturia resulting from resulting from stuctural changes in the glomelular membrane of the kidney, progressive hearing loss and ocular lesions. Cause by mutations that prevent the formation of type IV collagen fibers.
Alport’s Syndrome
A tendency to blister with minor trauma and are prone to sunburns resulting form absence of anchoring fibrils (NO type VII collagen).
Kindler’s Syndrome
Tendon function and associated connective tissue
Function: Receiving and then Transmitting Large Muscles contraction forces
• Primarily in a Single Direction
Connective Tissue: Dense Regular Connective Tissue
Intestine function and associated connective tissue
- Function: Nutrient absorption from lumen and transportation to Blood and Lymph vessels in underlying connective tissue
- Connective Tissue: Loose Connective Tissue
Joint Capsule function and associated connective tissue
Function: Receives and Transmit Ligament and Muscular Forces
• Multi-directional Forces
Connective Tissue: Dense Irregular Connective Tissue
