Histology - Connective Tissue - Reverse

Abundant cells, euchromatic nuclei & with lots of cytoplasmic processes. Abundant ground substance. Few, if any, reticular fibers.

Scattered cells with heterochromatic nuclei. Fair amt ground substance. Clearly visible fibrils and fibers.

1. 1. Loose (areolar) (LCT) 2a. Dense irregular 2b. Dense regular 3. Reticular tissue

Primarily beneath epithelium, LOTS of cells, fair amt of ground substance. Loosely arranged ECM, “woven mat”. Site of immune responses.

Clear spaces, multidirectional. Fewer cells, much less ground tissue. Large bundles of collagen fibers oriented in multiple directions.

Fewer cells, box car nuclear arrangement, unidirectional. Little ground substance. Collagen fibers: Large bundles oriented in one direction.

Stroma of liver, spleen, bone marrow, lymph nodes, endocrine organs

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.

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.

Throughout body, large round oval cells, appear white. Long term energy homeostasis.

Multilocular adipocytes that are smaller and appear vacuolated. Heat-generation. Found mostly in infants (back, neck, shoulders) and adults around organs.

structural framework, harnesses muscle contraction into movement, scaffolding of gland and organs, medium for metabolic exchange, protection, fat storage.

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.

Repeating, mostly sulfated, disaccharide units.

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.

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”.

Charge-based filtration barrier

Multidomain and multifunctional molecules that stabilize the ECM assembly and link it to the CT.

Fibronectin, Laminin, Tenascin, Osteopontin, Entactin/Nidogen

Elastic, Collagen, Reticular

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.

Orcein

Surround and permeate elastic fibers, helping to organize their growth.

Most abundant structural component (30% of dry weight of the body). Imparts tensile strength to tissues. Flexible but not elastic.

Fibrillar (I, II, III), Sheet-forming (IV), Anchoring (VII).

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.

mature collagen molecule

orderly alignment of tropocollagen molecules

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).

Less common, found in cartilage and vitreous humor. Provides tensile strength and restrains PG aggregate expansion.

slender fibrils, no bundling.

Heavily glycosylated. Fibrils only. First collagen laid down in embryo and after an injury.

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.

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).

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.

Anchoring, non-fibrillar. Anchors basal lamina to reticular lamina.

From mesenchyme, which is sourced from mesoderm and neural crest. Mesenchyme-like cells, retained in adult CTs are source of stem cells.

Fribroblast, Chondrocyte, Adipocyte

Benign: lipoma. Malignant: Liposarcoma

Benign: Chondroma. Malignnant: Chondrosarcoma

Principal CT cell. Synthesizes & secretes all ECM components.

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.

Quiescent fibroblast. Fewer cells, more widely dispersed. Reduced activity, ECM maintenance.

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).

Arise from monocytes (white blood cell) after migration from blood into CT, whereafter they are considered resident CT cells.

1. 1. Host response to injury: Inflammation. 2. Host defense.

Large cells, eccentric nuclei, pften appear vacuolated

Features of a phagocytic cell

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.

Preformed chemical mediators of inflammation. Secrete Cytokines & Leukotrienes. Skin, Respiratory & GI systems.

Anticoagulant mast cell. (a GAG).

A mast cell that promotes increased vascular permeability, intense smooth muscle contraction, and mucus secretion by nasal & bronchial glands.

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.

(brown) fat cells located in brown adipose tissue. Function: Heat generation (thermogenesis)

1. 1. Develop elsewhere (bone marrow) 2. Migrate into CT’s to perform their functions 3. Short-lived: White blood cells and Plasma cells

Oval-shaped cell (tear drop), Eccentric nucleus, Prominent nucleolus, Heterochromatin distributed in “Clock-face or Cartwheel” pattern.

Comprises the functional parts of an organ. Liver = hepatocytes.

The connective, supportive framework of a biological cell, tissue, or organ.

Epithelium + Lamina propria

Simple columnar with brush border + goblet cells

Ground Substances

Marfan’s Syndrome

Osteogenesis Imperfecta

Provides Tensile strength and Restrains Proteoglycan Aggregate expansion

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.

Ehlers-Danlos Type IV

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.

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.

A tendency to blister with minor trauma and are prone to sunburns resulting form absence of anchoring fibrils (NO type VII collagen).

Tendon function and associated connective tissue

Intestine function and associated connective tissue

Joint Capsule function and associated connective tissue