Connective Tissue Histology Lecture Series
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Undergraduate – Graduate Connective Tissue Histology Lecture Series Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX 77843 Objectives • Learn how connective tissue is classified • Composition of the extracellular matrix • Recognize extracellular matrix components • Function of connective tissue cells • Recognize connective tissue cells Four basic types of tissues Epithelium (90% of tumors) Connective tissue Muscular tissue Nervous tissue Connect tissue in nerve Connective Tissue Function: The histological glue which binds the other tissues together to form organs, specializations include blood, cartilage, and bone. Function of Connective Tissue Mechanical support - stroma below epithelium, skeleton Metabolite exchange - vascular beds Energy storage - adipose tissue Inflammation - site of action for blood borne immune cells Plasma Fibrosis - wound healing-over-production of collagen cells skin Slide 109 140 Distinguishing features • Loose connective tissue – sparse collagen and elastic fibers, plentiful cells including fibroblasts, leukocytes • Dense connective tissue – concentrated collagen, few cells • Cartilage – avascular homogeneous matrix of collagen and protein- polysaccharides with few cells • Bone – calcified collagen matrix with few cells trapped in the caves of bone Cartilage Epithelium Bone Loose connective tissue Dense connective tissue Bone Cartilage Function of CT Mechanical support - stroma below epithelium Epithelium of the epidermis Stroma of the dermis Function of CT Metabolite exchange – vascular beds Function of CT Energy storage - adipose tissue fat cells skin human breast Function of CT Inflammation - site of action for blood borne immune cells Function of CT Fibrosis - wound healing - over- production of collagen CONNECTIVE TISSUE CLASSIFICATION CONNECTIVE TISSUE CLASSIFICATION mesoderm from the mesoderm CT derived from the bone marrow Classification of CT Ratio of cells to fibers – Loose (mostly cells) – Dense (mostly matrix) Loose (mostly cells) Dense (mostly matrix) Classification of CT Arrangement of fibers – Irregular in dermis and capsules – Regular in tendon Regular Irregular Regular Capsule of the testis Tendon Tendon Classification of CT Origin of cells – Fixed – Wandering Macrophage Mast cell Extracellular Matrix – Collagen (Type I) General characteristics – flexible with high tensile strength, Cross linking of fibril adds stability, and Resist collagenase .. ..digestion! Extracellular Matrix - Collagen Synthesis by fibroblasts Extracellular Matrix – collagen Synthesis is by fibroblasts as procollagen, procollagen peptidase cuts to make tropocollagen and assembles. Do the : Pulse – Chase experiment Look for the: Temporal Appearance of silver grains in the photographic emulsion over organelles of interest. Radioactive precursor is the source of radioactivity in final cellular product ----------------------------------- Product Precursor Protein general amino acids DNA thymidine RNA uridine Collagen (sp. protein) proline and lysine (sp. a.a.) Extra-cellular Matrix: Collagen Proline is repeated in the collagen to make it turn (its ring structure stabilizes the helical conformation of the triplet strands) Lysine cross links the strands Glysine has no side chains – good for collagen backbone as it is small and can fit into the crowded space of the triple helix Extra-cellular Matrix: Collagen Proline is repeated in the collagen to make it turn (its ring structure stabilizes the helical conformation of the triplet strands) Lysine cross links the strands Glysine has no side chains – good for collagen backbone as it is small and can fit into the crowded space of the triple helix Extra-cellular Matrix: Collagen Proline is repeated in the collagen to make it turn (its ring structure stabilizes the helical conformation of the triplet strands) Lysine cross links the strands Glysine has no side chains – good for collagen backbone as it is small and can fit into the crowded space of the triple helix Extracellular Matrix - Collagen Synthesis Polymerization staggered with caps - periodicity Extracellular Matrix – Type I Collagen (varies in thickness) Extracellular Matrix - Types of Collagen Fibrous types Type I - fiber forming Type IV - most CT Type II - fibril forming Hyaline cartilage and Vitreous body of eye Type III Type III - reticular network - branching Type I Type I Extracellular Matrix - Types of Collagen TYPE III - RETICULAR NETWORK Extracellular Matrix - Types of Collagen TYPE III - RETICULAR NETWORK Extracellular Matrix - Types of Collagen Aggregates Type IV - basement membrane Type V - vascular - most CT Type IV Extracellular Matrix - Elastin Low tensile strength Recovers original shape after stretched Slide 427 TUNICA ADVENTITIA TUNICA INTIMA Aorta (large elastic artery) Elastic laminae interspersed with smooth muscle cells TUNICA MEDIA Vasa vasorum TUNICA ADVENTITIA TUNICA MEDIA TUNICA ADVENTITIA 472 Fallopian tube Elastic muscular arteries laminae Muscular arteries Tunica media tunica intima Tunica adventitia Wrinkled lumen Extracellular Matrix - Ground Substance Proteoglycans - ground substances • Hyaluronic acid • Glycosaminoglycans Fibronectin - biological glue • (Glycoprotein) • Binds cells to extracellular • Matrix and to each other (fibronectin junctions) Extracellular Matrix - Ground Substance Proteoglycans - ground substances Hyaluronic acid Glycosaminoglycans Extracellular Matrix - Ground Substance Type II found in cartilage Extracellular Matrix - Ground Substance Extracellular Matrix – Ground Substance Fibronectin - biological glue – (Glycoprotein) – Binds cells to extracellular – Matrix and to each other (fibronectin junctions) Cells of CT Fibroblasts - extracellular matrix synthesis Mesenchymal cells - stem cells Adipose cells - energy storage Macrophage - monocyte linkage Fixed and Wandering Plasma cells - antibody production Mast cells - allergic response Others - lymphocytes, eosinophils Blood cells Cells of CT (all from mesoderm) mesoderm Fibroblasts Mesenchymal cells Adipose cells Macrophage Plasma cells Mast cells Others Cells of CT Fibroblasts - extracellular matrix synthesis Developing tendon Collagen Cells of CT Fibroblasts - extracellular matrix synthesis Developing tendon Collagen Small groups of fibers seen in narrow recesses of the cell Cells of CT Mesenchymal cells - stem cells Cells of CT Adipose cells - energy storage Cells of CT Adipose cells - energy storage BLOOD FAT CELL lipid Blood vessel Fat cell White fat Brown fat White fat Slide 195 Fetal jaw Fibroblasts Brown fat Slide HISTO039 Brown fat at work Cells of CT Cells of CT LIVER KUPFFER CELLS Macrophage - monocyte linkage • Fixed • Wandering Macrophages • Fixed • Wandering (free) Mononuclear Phagocyte System Stem Cell Committed Stem Cell Monoblasts Bone Marrow Promonocytes Monocytes Monocytes Peripheral Blood Macrophages Organs LIVER Cells of CT Macrophage – monocyte linkage ALVEOLAR MACROPHAGES Alveolus of lung Macrophages in the Normal State • Connective tissue (histiocytes) • Liver (Kupffer cell) • Lung (alveolar macrophage) • Lymph nodes (free and fixed macrophages; interdigitation with cell) • Spleen (free and fixed macrophages) • Bone marrow (fixed macrophage) Macrophages in lymph node Macrophages in the Normal State • Serous cavities (pleural and peritoneal macrophages) • Bone (osteoclasts) • Central nervous system (CSF macrophages; brain macrophages) • Skin (histiocyte ( tattoo ); Langerhans cell?) • Synovia (Type A cell) • Other organs (tissue macrophage) Which is/are the real tattoo(s)? Can you read “ USN ” for US Navy? Tattoo after 52 years Macrophage last for 40 years, but how old were your macrophages when you got your tattoo? Cells of CT Macrophage - monocyte linkage Cells of CT Cells of CT Cells of CT Others – T lymphocytes Cells of CT Plasma cells - antibody production Cells of CT Mast cells - allergic response Others - eosinophils Mast cell Induced Degranulation of Mast cells Cells of CT Mast cells - allergic response Others - eosinophils EOSINOPHILS Mast cell Fibroblasts Lymphocyte Adipose cell Formed Elements and Functions in Blood Cell Type Main Functions Erythrocytes CO2 and O2 Transport Neutrophils Phagocytosis Of Bacteria Eosinophils Parasitic Infections, Inflammatory Processes Basophils Release of Histamine and other Inflammation Mediators Monocytes Mononuclear-phagocyte system; Phagocytosis Formed Elements and Functions in Blood Cell Type Main Functions B Lymphocytes Generation of Antibody- producing Plasma Cells T Lymphocytes Killing of Virus-infected Cells Natural Killer Killing of some Tumor and (Cytotoxic T Cell) Virus-infected Cells Platelets Clotting of Blood Blood cells are connective tissue cells 32583 Bone marrow cells Blood cells https://www.youtube.com/watch?v=UTo4LnXonTk&list=PLQltfhuKi1sgtel3O9IpDsbgEWMY3JaX5&index=19 Mesenchymal Cells Endothelial cells Smooth muscle cells Fibroblasts Slide 109: Skin, hand, monkey Fibroblasts Bundles of collagen fibers Smooth muscle cells Muscular artery Venule Endothelial cells Summary of Connective Tissue In summary Blood cells Marrow cells Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources! • Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. • Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. • William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA.