CT

Adipocyte- yellow or white

- yellow or white Cells synthesize and store lipid for nutrition and insulation Nucleus and cytoplasm are displaced by large lipid droplet May appear as small clusters of cells or large accumulations Most common is a yellow/white adipocyte. The adipocyte is a huge cell, the large airy looking areas in the images above are all adipocytes. These are the cells that synthesize lipid for nutrition and insulation. Their large size is due to the accumulated lipid in the cell. The nucleus is flattened and displaced to one side of the lipid mass; the cytoplasm forms a thin rim around the lipid. In routine histologic sections, the lipid is lost through extraction by solvents; consequently, adipose tissue appears as a delicate meshwork of polygonal profiles. metabolism results in the liberation of fatty acids that leave the cell and travel in the blood stream to distant tissues for energy production.

Monocyte

. Large, round cell, horseshoe-shaped nucleusb. They migrate from the bloodstream into connective tissues, where they rapidly differentiate into macrophages. c. Found in peripheral blood and connective tissue

Dense Reg CT

1. Collagen bundles in parallel rows 2. Few cell numbers and little variety, mainly fibroblasts 3. Little ground substance or vascularity- takes longer to heal 4. Ideal for resisting stretch in one direction 5. Found in tendons, ligaments Composed of collagen bundles all arranged in parallel orientation. Few elastic or reticular fibers. Few cells present and all one cell type ie. Inactive fibroblasts. Ground substance is in short supply since most of the area is occupied by fibers. The tissue is not very vascular. Found in tendons and ligaments. These cells can be awakened and transform into active fibroblasts. Little vascularity and therefore a tendon or a ligament is very slow to heal.

Neutrophils

7. Neutrophils a. Multi-lobed nucleus with 3-5 lobes b. weakly-staining cytoplasmic granules c. function as phagocytes Attracted to sites of infection: 1st line of resistance Most common WBC Neutrophils are the most common white blood cells as well as the most common granulocytes (white blood cells that contain granules). They are slightly larger than a RBC.. Has many lobes to its single nucleus ie. multilobed. Has granules of two types. They are motile cells; they leave the circulation and migrate to their site of action in the connective tissue ie. are pulled to sites of infection.

Myofibroblast

A unique, contractile fibroblast, characterized by the presence of bundles of actin filaments. These cells function to promote wound closure.

CT Proper

A. Loose connective tissue: 1. Contains a variety of cells and cell types 2. Fibers are mainly collagen, with some elastic and reticular fibers, interspersed. 3. Collagen fibers in thin fiber bundles of less than7μm in diameter 4. Ground substance is gelatinous and abundant 5. Distribution: prominent beneath epithelia covering body surfaces and lining the internal surfaces of the body. 6. Allows diffusion and cell migration initial site where pathogenic agents such as bacteria that have breached the epithelium first contact immune cells to initiate inflammatory and immune reactions. fills the spaces between muscle fibers, surrounds blood and lymph vessels and is present in the papillary layer of the dermis and in the lamina propria of the intestinal and respiratory tracts.

White Adipose CT

Adipocytes predominate, storing fat as triglycerides Collagen fiber septa form lobules, blood vessels within Reticular fibers form supporting framework Distribution: most parts of the body Fat cells can be found in most parts of the body but can also be found in large accumulations. All cells of the body need to be nourished, need access to nutrients so all cells have access to tissue fluid and nutrients from blood. Collagenous fibrillar septa divide tissue into lobules and blood vessels found here also. Reticular fibers form the supporting framework. Found throughout the body.

Dense IRR CT

B. Dense irregular connective tissue1. Thick collagen fibers and bundles (larger than 7μm in diameter) 2. Sparse ground substance3. Few cells (fibroblasts) interspersed with elastic and reticular fibers 4. Predominance of fibers compared to cells (mainly fibroblasts)5. Provides significant strength and resists stretching eg. dermis of skin Composed primarily of bundles of collagen which measure at least 7um in diameter or larger. Basically have masses of collagen and little ground substance. Bundles are randomly arranged. Some elastic fibers are present, but few reticular fibers. Since larger amounts of fiber are present, the number of cells is fewer, although all cell types may be represented, cells are mainly fibroblasts. Ground substance present in smaller amounts since fibers occupy more of the space. The example shown here is the dermis of the skin.

Erythrocyte

Biconcave, 7.5 μm in diameter b. Filled with hemoglobin c. Actin-containing cytoskeleton d. No cellular organelles e. 4 -7 million RBCs per μL of peripheral blood

Wound Healing

Blood clot forms Neutrophils and monocytes arrive Monocytes transform into macrophages and replace neutrophils by day 3 Growth factors pull in fibroblasts and vascular endothelial cells - granulation tissue Fibroblasts differentiate into myofibroblasts that contract connective tissue fibers New collagen fibers and ECM generated lead to tissue remodeling. By 2nd week, most cells die and disappear and leave a connective tissue scar.

Brown fat babies

Brown adipose tissue is present during fetal life and diminishes during the first decade after birth. In newborns, brown adipose tissue makes up about 5% of the total body mass. Brown fat cells can rapidly metabolize fat and generate heat. This heat helps offset the extensive heat loss that results from a newborns high surface-to-mass ration and avoids lethal hypothermia, a major risk of death for premature babies. the fatty acids generated are retained by the cell and rapidly metabolized. Due to the unique properties of mitochondria in brown fat, fatty acid metabolism results in the generation of heat. For this reason, brown fat is referred to as thermogenic. This heat helps offset the extensive heat loss that results from the newborn's high surface-to-mass ratio and avoids lethal hypothermia, a major risk of death for premature babies.

Elastic CT

Elastic fibers predominate that are arranged in sheets Produced by fibroblasts and smooth muscle cells Form the walls of large arteries As heart contracts, these sheets expand and the arteries dilate, heart relaxes, so do the elastic sheets. These elastic sheets have openings in them that allow nutrients to flow freely. The primary fiber is elastic and these fibers in this section are arranged in fenestrated sheets found in the walls of large arteries.

Brown adipose CT

Few connective tissue septa and a rich blood supply Brown multilocular fat cells predominate Found in newborns/hibernating animals Brown adipose tissue is a thermogenic tissue. It is present in large amounts in humans during fetal life. It diminishes during the first decade after birth but continues to be present in varied amounts, mainly around internal organs. Brown fat cells are held in place by collagen fibers and reticular fibers. Lipid droplets can be rapidly mobilized due to the large number of mitochondria that are present in the cytoplasm. The metabolic activity of brown adipose tissue is regulated by the sympathetic nerve system and is related to ambient outdoor temperature. An increase in the amount of brown adipose tissue has been reported on the neck during the winter months, especially in lean individuals and outdoor workers.

Macrophage or Histocyte

Macrophage or histiocytea. Highly phagocytic cellsb. Long-livedb. Indented nucleus, cytoplasm visiblec. Lysosomes and phagosomes in cytoplasmd. Other phagocytes derived from monocytes include Langerhans cells (skin); Kupffer cells (liver) and alveolar macrophages (lung).

Cells w heparin and histamine

Mast cells Basophils

Ground Substance

May be a watery fluid Forms the solid framework of bones Forms a barrier to prevent invasion by bacteria Functions to transport nutrients and waste products

Hematopoises-Blood cell formation

Mesoblastic: Blood cells form from mesenchymal cells in yolk sac and body stalk (from hypoblast); Hepatic: Blood cells form in liver, thymus, spleen Myeloid: Blood cells form in the bone marrow Starts very early about the 3rd week of gestation. Obviously need the heart forming and blood vessels and blood cells forming very early on in development. Hypoblast from yolk sac that is the first site of blood cell formation - referred to as the mesoblastic phase. Then the liver starts to form at about one month, it's first function is blood cell formation, then as bone starts to form, bone marrow will take over as the site of hematopoiesis. Fetal hemoglobin has a very strong affinity form oxygen to pull it away from the mother's hemoglobin, near the end of gestation the bone marrow then makes the adult form of hemoglobin.

Adipocyte brown

Multiple droplets of lipid (multilocular) Central nucleus Used in thermoregulation Abundant in newborns and hibernating animals Brown adipocytes contain multiple small droplets of lipid in the cytoplasm. The cytoplasm also contains numerous mitochondria. Fat can be mobilized very quickly with all these mitochondria so can heat up the body quickly. Found in newborn infants and hibernating animals.

Blood Cell Counts

Neutrophils : 40-75% of WBC's Lymphocytes: 20-50% of WBC's Eosinophils: 5% of WBC's Monocytes: 1-5% of WBC's Basophils: 0.5% of WBC's A microliter of blood contains only 6-10 thousand leukocytes/white blood cells.

Inactive Fibroblast

Nucleus very spindle-shaped, very heterochromatic Cytoplasm not always apparent with L/M; very thin with E/M Low metabolic rate With an inactive fibroblast, also known as a fibrocyte, the nucleus is, of course, heterochromatic. The nucleus is also very elongated, and again the cytoplasm is not readily visible in sections using a light microscope.. This cell is metabolically inactive but will reactivate when given the appropriate signal eg. Injury or trauma to the tissue.

CLot Formation

Platelets aggregate to stop bleeding; Fibrinogen from platelets reacts with factors from blood plasma; Fibrin forms a network of fibers trapping blood cells to form a clot.

Mucous CT

Primitive fibroblastsAbundant ground substance, primarily hyaluronic acidLimited fibersFound in umbilical cord, called Wharton's jelly. An embryonic kind of connective tissue, mesenchymal cells have the capacity to form into different kinds of connective tisue. Two umbilical arteries, one vein. Lots of ground substance, mainly hyaluronic acid . Very few fibers. As a mucous tissue it protects and insulates umbilical blood vessels. Also called Wharton's jelly, when exposed to temperature changes, collapses structures within the umbilical cord and thus will provide a physiological clamping of the cord, an average of 5 minutes after birth.

Elastic Fibers

Produced by fibroblasts, vascular smooth muscle cells and chondrocytes in elastic cartilage Amorphous core of elastin in a sheath of microfibrils Found with collagen fibers in all loose connective tissue May form branching sheets with fenestrations in blood vessels

Reticular Fiber Collagen Type 3

Thin fibers that branch Not visible with H&E staining; visible with silver stains (argyrophilic or "affinity for silver") Abundant in smooth muscle, surround nerves, small bv, adipocytes, and provide the framework of hematopoietic tissue bone marrow and lymphoid organs Prominent during embryogenesis, inflammatory process, wound healing.

Plasma Cells

a. Antibody-producing cells b. Oval shape, eccentric round nucleus with clumps of heterochromatin peripherally, described as "clock-face" b. Basophilic cytoplasm due to extensive RER c. Large Golgi apparatus in prominent pale-staining region of cytoplasm that lacks RER "negative Golgi"

Eosinophils

a. Bi-lobed nucleusb. Distinct eosinophilic granules which are lysosomesc. Phagocytic and increase in number with parasitic infections Eosinophils are named for the large, eosinophilic, refractile granules in their cytoplasm. Found in peripheral blood, about 12 to 14 um in size with a bilobed nucleus. Eosinophils are associated with allergic reactions, parasitic infections and chronic inflammation. Contains granules that are lysosomes that function in the destruction of parasites. The count of eosinophils in blood samples of individuals with allergies and parasitic infections is usually high. Eosinophils play a major role in host defense against helminthic parasites. They are also found in large numbers in the GI tract and other sites of potential chronic inflammation, such as the lungs of patients with asthma.

Lymphocyte

a. Small, 6 to 7 μm in diameter b. Heterochromatic nucleus c. T and B lymphocytes exist d. Plasma cells from B lymphocytes Lymphocytes accumulate beneath the epithelium of the respiratory and gastrointestinal tracts. Here they are involved in immunosurveillance against pathogens and foreign substances that enter the body after crossing the epithelium. Lymphocytes have a very heterochromatic nucleus with a thin rim of cytoplasm visible. They are the smallest of the wandering cells, and also will leave the blood and enter the connective tissue. T lymphocytes are associated with the thymus. B lymphocytes come from the bone marrow. They are two arms of the immune system. But the B lymphocytes are the ones that are going to differentiate into our next connective tissue cell type, the plasma cell.

Mast Cells

a. Small, centrally located nucleus b. Granules contain, heparin and histamine  c. Involved in the inflammatory response, tissue repair  c. Become activated in allergic reactions are stimulated to release their granules upon exposure to allergens. Release of the contents promotes the allergic reaction known as immediate hypersensitivity reactions . The reactions are immediate because they occur within a few minutes after exposure to an antigen, to which an individual is previously sensitized. There are many examples of immediate hypersensitivity reactions, however, a dramatic one is anaphylactic shock, a potentially fatal condition. Other granules contain chemotactic factors for eosinophils and neutrophils that attract these cells to sites of inflammation. Mast cells are widely distributed in the human body, they are particularly abundant beneath epithelial surfaces in the respiratory and digestive tracts and skin, where they are most likely to encounter allergens.

Basophils

bi-lobed nucleus Least common of WBC's Large granules contain heparin and histamine Basophils are so named because the numerous large granules in their cytoplasm stain with basic dyes. Basophils are the least numerous of the white blood cells. Often several hundred WBCs must be examined in a blood smear before one basophil is seen. Basophils are functionally related to, but not identical with, mast cells of the connective tissue. Granules contain vasoactive agents that are responsible for the severe vascular disturbances associated with hypersensitivity reactions and anaphylaxis.

Neutrophils

highly phagocytic > cardinal signs of inflammation Dolar: pain Calor: warmth Tumor: swelling Rubor: redness After intracellular digestion, remnants are stored or exocytosed. During this process most neutrophils die: the accumulation of dead bacteria and dead neutrophils forms pus. Neutrophils are motile cells; they leave the circulation and migrate to their site of action in the connective tissue. Neutrophils are the most numerous of the first wave of cells to enter an area of tissue damage. Histamine and heparin released by mast cells at the injury site open the intercellular junctions between endothelial cells, allowing the neutrophil to migrate into the connective tissue. Drawing shows a neutrophil sucking a bacteria into its interior, lysosome will dump its enzymes into that vacuole to kill the bacteria. Thousands and thousands of cells will accumulate at sites of infection. Cardinal signs of inflammation, dolar is pain and the first sign of a problem. Calor and tumor and rubor result of bvs dilating more blood coming in and more neutrophils leaving the blood.

Heparin

in mast cell granule local anticoagulant

Histamine

in mast cell granulepromotes increased vascular permeability and smooth muscle contraction causes capillaries to dilate and become leaky allowing fluid and cells to escape from blood vessels into the surrounding tissue during an inflammatory or allergic response.

Lamina ProprIa

loose C.T. located beneath an epitheliumgastrointestinal tract; respiratory tract, genitourinary tract This type of loose connective tissue is the kind that supports an epithelium. The core of each of these finger-like projections (intestinal villi) is composed of loose connective tissue. There is a rich blood supply in this area to pick up the nutrients that are going to pass through this loose connective tissue. Lamina propria refers specifically to a loose ct supporting an epithelium.

CT Cellls Active Fibroblast

the principal cell of CT, stay in the CT, long term resident Nucleus is oval or spindle-shaped, very euchromatic, nucleoli, takes over complete view Cytoplasm not discernible at L/M level E/M reveals abundant RER, and prominent Golgi Function to produce and maintain c.t. fibers and ground substance

Reticular CT

tissue Collagen type III is predominant fiber Reticular cell produces fiber and wraps around fiber Forms framework of blood cell forming organs Network of reticular fibers forming the supporting framework of specific organs, particularly in lymphatic and hemopoietic tissues. Can be produced by fibroblasts or reticular cells. Silver stains these fibers black, otherwise they cannot be discerned.