Connective Tissue - Histology Flashcards
Connective Tissue is derived from…
Mesoderm
Special Connective Tissue
Adipose
Blood
Cartilage
Bone
Components of Connective Tissue
Cells - Fixed and transient
Extracellular Matrix (material between cells) - Fibers (resist tensile forces)
Ground Substance - Amorphous (reisist compressive forces)
Collagen
Resist Tensile Forces
Most abundant
White (tendons)
Formed by fibroblasts and non-connective tissue
28 types
DO NOT BRANCH
Collagen Formation
1) 3 PREPROCOLLAGEN (glycine, proline, hydroxyproline, and hydroxyglysine)
ALLIGN = PROCOLLAGEN MOLECULE = rope, soluble
2) At secretion = terminal protein removed by procollagen peptidases = TROPOCOLLAGEN
3) TROPOCOLLAGEN polymerizes in extracellular matrix = FIBRILS
4) FIBRILS polymerize = COLLAGEN FIBERS
Reticular Fibers
Type II Collagen
AGYROPHILLIC
BRANCHES (Lattice Network)
SILVER STAIN
Small (glycoprotein coat prevents enlargement)
Make up LCT and Reticular CT
Elastic Fibers
Elastin
NO HYDROXYLYSINE = stretch
4 lysine molecule with a desmosome link (elasticity)
Surrounded by microfinrils (fibrillin)
BRANCHES
Can form internal elastic membrane (DRCT) = sheath - cont around an artery
Elastic Fiber Formation
1) Elastin is deposited on the scaffold of microfibrils forming amorphous structures
2) initially fiber consists of fibrollin microfinrils secreted by fibroblasts and smooth muscle
3) Elastin accumulates = occupies most of electron-dense center of single elastin fiber and fibrillin microfibrils remain at the fiber surface
Elastin resists digestion by ———- but is hydrolyzed by———-
Proteases
Pancreatic Elastase
Elastin (unlike collagen) can form…
…a sheet = ELASTIC MEMBRANE or ELASTIC LAMINA
Prominent in arteries
Formed by fibroblasts and smooth muscle cells
Ground Substance
Stuff in between the cells and the fibers
Hydrated gel of complex sugars (glycosaminoglycans (GAGs), proteoglycans, and multiadhesive glycoproteins)
Resists forces of compression, lubricant, and barrier to the penetration of invaders
Glycosaminoglycans (GAGs)
Unbranched, negatively charged long chain of disaccharides
Attracts water = hydrated gel which resists compression
Repel each other = slippery texture that resists compression
EX = HYALURONIC ACID (common)
Proteoglycans
Made of test-tube brush proteins with GAGs attached
Negative
Attract water and repulse each other
Form hydrated gel
Act as diffusion barrier
Aggrecan = macromoleculs that allows for gel state and barrier for diffusion
Many bact secrete hyaluronidase = gel state ot sol state = rapid spread of bact
Multiadhesive Glycoproteins
1) Attachment to cells in ECM
2) Mediate interaction between cells
3) Has transient regulatory substances (interleukins, growth factors, hormones, plasma proteins, etc.)
EX = LAMININ (basal lamina of stratified epithelium and external lamina of nerves and muscle fibers) and FIBRONECTIN (ECM)
Movement of Fluids
Water leaves capillary and goes into ECM at arterial end of capillary = Hydrostatic P
Water is pulled back in at the venous end of the capillary = Plasma Colloid Osmotic P
Mix of nutrients, etc.
Connective Tissue is classified by….
….amount, direction, and tyoe
Dense Connective Tissue
1) DENSE REGULAR CONNECTIVE TISSUE
Elastin or collagen Tendons, ligaments, cornea Fibers on one direction Tensile strength One break = whole thing is weakened
2) DENSE IRREGULAR CONNECTIVE TISSUE
Elastic or collagen
Dermis, capsules of organs, and periosteum
Protective Coating
Multiple directions
Loose Connective Tissue
Areolar
Superficial fascia, lamina propria of intestines
Less fibers = more cells and open space (amorphous material)
Exchange
Reticular Connective Tissue
Spleen and lymph nodes
Basement membranes
Agyrophilic = silver
Cellular movement and nutritional exchange
1st sign of decrease in collagen
Teeth falling out
Connective Tissue Cells
1) Fixed Cells Fibroblast Fibrocyte Pericyte Adipocyte Mast Cell Myofibroblasts
2) Transient Cells Plasma Cell Neutrophil Eosinophil Lymphocyte Macrophage
Fibroblast
FIXED CELL IN CONNECTIVE TISSUE
Most numerous cell in connective tissue
Produces and maintains the ECM (with smooth muscle cells) = Fibers and Ground Substance
Metabolically active (open faced = euchromatin in nucleus)
Spindle shape
Cytoplasm not apparent
Tendinoctytes in tendon
Myofibroblasts
FIXED CELL IN CONNECTIVE TISSUE
Modified fibroblasts that demonstrate similar characteristics to fibroblasts (by creating massive amounts of ECM) and smooth muscle cells (by contracting)
Common in healing wounds = speed healing by contracting edge of wounds
Pericytes
FIXED CELL IN CONNECTIVE TISSUE
Immature mesenchymal cell
Wall of capillaries and venules
Cytoplasm with actin and myosin
Can differentiate into other cell types (myofibroblasts, smooth muscle cels, or endothelial cells)
FUNCTIONS:
Blood brain barrier
Blood flow regulator
Damage to = diabetic retinopathy
Too many in brain = Alzheimer’s Disease
Tumors cannot recruit = weakness and disorganization of tumor vasculature
When they die, they constrict
Adipocyte
FIXED CELL IN CONNECTIVE TISSUE
1) Unilocular/ White - single large lipid droplet Energy storage Prominent in SER Lipid metabolism Endocrine tissue Nucelus is pushed to the side
2) Multilocular/Brown Multiple lipid droplets Heat Production = non-shivering thermogenesis Abundant MITOCHONDRIA Neonatal/ hibernating animals
Lipid only present in vivo (removed due to processing)
Mast Cell
FIXED CELL IN CONNECTIVE TISSUE
W/in connective tissue of organs with orifices, skin, and serous membranes
Also prominent in LCT of blood vessels
Primary Mediators:
Chondrotin sulfate
HISTAMINE
Eosinophil chemotactic factor (ECF) = limit inflammatory response
Neutrophil chemotactic factor (NCF) = limit inflammatory response
Secondary Mediators
D2
leukotrienes C4 and D4
Basophilic granules can obscure nucleus BUT cytoplasm is easily identified
Mast Cell Tumors
Most common cutaneous tumor found in dogs
Affects heart rate, BP, etc.
Develop in dermis and subcutaneous
Found commonly on trunks
Leukocytes
TRANSIENT CELL IN CONNECTIVE TISSUE
WBC
1) Granulocyte - sp. granules; segmented/lobed nucleus
Neutrophil (PMN)
Eosinophil
Basophil
2) Agranulocyte:- NO sp. granules BUT contain primary granules; round nuclei and minimal cytoplasm
Common in CT of mucous membranes, spleen, thymus, lymph nodes, tonsils, etc.
Lymphocytes
Monocyte (can only ident. in a blood smear)
Macrophage
TRANSIENT CELL IN CONNECTIVE TISSUE
Agranuloctyes = from Monocyte (stays in blood; out of blood = macrophage)
Kidney bean shaped nucleus = open- faced
FUNCTIONS:
Ingest and destroy
Secretion of cytokines (messages)
Antigen Presentation
Cell shape is ueven due to filopodia projections
Eosinophil
TRANSIENT CELL IN CONNECTIVE TISSUE
Granulocyte
Elongated nuclei
Acidophilic cytoplasmic granules
FUNCTIONS:
Phagocytosis
PARASITES
Limit inflammation from mast cells
Specific or secondary granules are eosinophilic
Granules contain major basic protein, eosinophilic peroxidase, neurotoxins, and eosinphilic cationic portein
Azuric sp ganules
Neutrophil
TRANSIENT CELL IN CONNECTIVE TISSUE
Granulocyte
Most common leukocyte
Cytoplasmic granule present BUT not visible
FUNCTIONS:
Phagocytosis of BACTERIA
Limit inflammation by mast cells
Stained mildly by basophilic and eosinophilic dye = neutrophil
stores of glycogen
can survive in an anaerobic env = can fight bact in necrotic tissue
when die, neutrophils and bact become white/yellow pus
the more lobes of the nucleus = the older the neutrophil
Basophil
TRANSIENT CELL IN CONNECTIVE TISSUE
Granulocyte
Large cytoplasmic granules= obscure nucleus (bilobed)
Store and release histamine = SIMILAR TO MAST CELLS
Pasma Cell
TRANSIENT CELL IN CONNECTIVE TISSUE
Immunoglobulin
Abundant RER = basophilic cytoplasm
Clock-face nucleus (round with heterchromatin)
Lack of staining around nucleus = negative golgi
Derived from B lymphocyte
Exuberant Granulation Tissue = ?
Proud Flesh
Tendon
DRCT
Tendinocytes (fibroblasts)
Boxcar Effect - fibroblasts pushed together in a row
Basophilic Streaming - active fibroblast
What molecule stains evenly with eosin?
Plasma Protein
Granules of Neutrophils
Azurophillic primary granules contain:
1) Myeloperoxidase (MPO) - gnerates reactive oxygen sp. = superoxide, hydroxide
2) Lysozymes = degrades bact wall and structure
3) Defensins = small proteins which are inserted into bact wall = bact cannot control ion gradient = explode
Sp. or Secondary Granules
1) Do not stain
2) Contain chemokines to attract more WBCs
3) Lactoferrin = binds iron which bact need to live
Macrophages and mast cells attract ——– and —–
Eosiniphils and neutrophils
Jejunum
1) Epithelial layer
2) Basment Membrane
Lamina lucida = adhesion molecules (integrin, laminin)
Lamina Densa = type IV collagen and fibronectin
Lamina Reticularis = type I and III Collagen, types IV and VII collagen anchoring plaques and fibrils; made by fibroblasts
