MSK_MT1_ILS1 (Histology of ConnTiss&Muscle) Flashcards
Epithelial Tissue
- continuous sheets of cells that line internal surfaces and cover the external surface of the body
- glands are derived from epithelium
Connective Tissue
supports, binds together, and protects tissues and organs.
It is composed of cells in an abundant extracellular matrix.
includes cartilage, bone, and blood.
Muscle Tissues
- cells that have the ability to contract.
- Uses the contractile proteins actin and myosin.
Nervous Tissues
- specialized for the rapid communication of information from one region of the body to another.
Connective Tissue Function
- Tissue for connecting, linking and holding other tissues.
- Contains cells and extracellular matrix of fibers and ground substance
- Function: structural support, defense, repair, storage (water, electrolytes, proteins, fat)
acts as a medium for exchange of nutrients and wastes between the blood and tissues, protects against microorganisms, repairs damaged tissues, and stores fat.
Embryonic Connective Tissue
Mesenchymal tissue is found only in embryos.
It consists of a gel-like amorphous matrix, a few scattered reticular fibers, star-shaped (stellate) fibroplasts, pale-staining mesenchymal cells
Mucous tissue (Wharton jelly) is a loose CT located in umbilical cord
Areolar / Loose Connective Tissue
- More ground substance and cells with few fibers
- Flexible and well vascularized
- Little tensile strength, not resistant to stress
- Lamina propria in the digestive tract
- More abundant than dense connective tissue
- space filler of deep skin
Dense Regular Connective Tissue
- Abundant collegen fibers arranged in parallel bundles with few cells/ECM
- strong/resistant to stress
- skin thick deep layer of dermis
- Found in tendons, ligaments, aponeuroses
Elastic Connective Tissue
- More elastin-based proteins than collagen
- Found in large arteries
Specialized Connective Tissue: Adipose Tissue
- Unilocular or white fat
- secrete hormones/cytokines (eg. leptin and adiponeptin; multilocular or brown fat)
- Adipocytes contain numerous mitochondria for metabolic generation of heat
- Flattened nucleus found around the rim of cytoplasm
- RARELY divides
Connective Tissue Components: Permanent Residents
- Fibroblasts: synthesize fibers, secrete ground substance
- Macrophages: protection and immunity
- Mast cells: inflammation, allergy
- Adipocytes: lipid storage
Connective Tissue Components: Transient Cells
- Plasma cells
- Leukocytes/ Lymphocytes
- Neutrophils and Eosinophils
Fibroblast
- Most abundant cells, Spindle-shaped
- Synthesize fibers (collagen, elastic fibers)
- Secrete ground substance
- Normally non-mitotic but can replicate
- Makes protein: contains rough ER and large Golgi complex
Macrophage
- Derived from blood monocytes
- MIGRATE into CT and stay (histiocytes)
- Phagocytic: contains lysosomes and residual bodies
- Exist as Kupffer cells in liver
- Initiate immune responses (present antigens to lymphocytes); secretehydrolyticenzymes(eg.collagenase);
- Can replicate
Mast Cell
Contain basophilic cytoplasmic granules that obscure the nucleus
- Granules contain histamine and heparin (involved in allergic reactions)
Plasma Cells
- Derived from mitotic B-lymphocytes
-
Secrete anti-BODIES
- contains rough ER and prominent Golgi complex
- Eccentric nucleus with clock-face arrangement
- 10-20 day lifespan
- Involved in immune response
Lymphocytes
- Smallest free cell in CT (Nucleus occupies most of the cell)
- B cells and T cells
- Involved in infection, tissue inflammation and immunity
Extracellular Matrix is composed of…
- ground substance
- fibers
ECM provides a medium for the transfer of nutrients & waste between connective tissue cells ⇌ the blood stream
Ground Substance
-
colorless, transparent, gel-like material (contains fibers)
- glycosaminoglycans, proteoglycans, and glycoproteins
- Serves as a lubricant, helps to prevent invasion of tissues by foreign agents, and resists compression.
- in ECM
Fibers
- in ECM
- types: collagen, reticular, and elastic
Collagen Fibers
- most common: types I and III collagen
-
Fibroblasts synthesize alpha chain proteins → rER → procollagen → secreted out of cell:
- Procollagen → tropocollagen → collage → self-assembly takes place outside the cell
- great tensile strength
Type I Collagen Fibrils
banding pattern on the surface of collagen fibrils
Reticular Fibers
- extremely thin diameter
- composed type III collagen
- Stain black with silver salts (b/c high carbohydrate content)
- Arranged in a mesh pattern
- Found in small blood vessels, nerves, muscle cells.
- Present in wound healing and scar tissue
- Supporting stroma in lymphatic tissue (Reticulocytes)
- Provide early strength to newly synthesized ECM
- Gradually replaced* by *stronger Type I collagen
Elastic Fibers
- are coiled branching fibers that sometimes form loose networks.
- These fibers stretch up to 150% of their resting length.
- They consist of Elastin and thin microfibrils (fibrillin-1 which is bound to elastin)
Glycosaminoglycans (GAGs)
- Ground Substance
- large unbranchedpolysaccharide chains
- eg. hyaluronic acid, chondroitin sulfate
Proteoglycans
- Ground Substance
- core protein backbone to which GAGs are attached
- responsible for viscosity and gel-like consistency (binds to water and cations )
Adhesive Glycoproteins
- Ground Substance
- globular protein with short branched carbohydrates
- eg. fibronectin, laminin
Muscle Histology Overview
- sarco = flesh:
- sarcolemma = plasma membrane
- sarcoplasm = cytoplasm
- sarcoplasmic reticulum = endoplasmic reticulum
Non-Striated Muscle
- smooth, involuntary
- located in blood vessels, viscera; hair follicles
Striated Muscle
- skeletal (voluntary): attached to the skeleton
- cardiac (involuntary): heart, base of large veins
Smooth Muscle
- elongated fusiform shapes with tapered ends
- Connected by gap junctions
- Cytoplasm appears evenly eosinophilic in H&E light microscopy (pink)
- The nucleus.. appears elongated in longitudinal sections, and round in transverse sections
- contains myosin and actin filaments but NO SACROMERES
- contains intermediate fibers (desmin and vimentin)
- type III and type IV collagen
