Histology - Connective Tissue - Reverse Flashcards by N Eberhart

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

Mesenchyme

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

Mucous Connective Tissue

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

Connective Tissues Proper Types

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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)

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

Dense Irregular Connective Tissue (DiRCT)

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

Dense Regular Connective Tissue (DRCT)

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

Reticular Tissue Location

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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

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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

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

White Adipose Tissue

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

Brown Adipose Tissue

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

Conective Tissue Support Functions

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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

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Repeating, mostly sulfated, disaccharide units.

Glyscosaminoglycans (GAGs)

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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)

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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

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Charge-based filtration barrier

Primary function of GAGs & PGs in BM

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

Multiadhesive glycoproteins (MGPs)

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Fibronectin, Laminin, Tenascin, Osteopontin, Entactin/Nidogen

Multiadhesive glycoprotein examples

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Elastic, Collagen, Reticular

ECM Fiber Types

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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

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Orcein

Specific stain for elastic fibers

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

Fibrillin microfibrils

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

Collagen

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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

1. 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

1. 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

1. Problem with elastic fibers. Test w/ Steinberg test (Make a fist w/ thumb inside) and Walker-Murdoch sign (Thumb to pinky around wrist). 2. 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

Histology - Connective Tissue - Reverse Flashcards

(72 cards)