Lecture 2- Connective Tissue Flashcards
Connective Tissue
-Most abundant tissue
-Provides supportive and connecting framework (stroma) connect, anchor, support
-Role in storage of metabolites, immune/inflammatory responses, tissue repair
Composition: -Cells and Exctracellular matrix (ECM) made of fibers and proteoglycans (ground substance)
-Cells widely scattered in matrix
-Matrix secreted by cells (is not living)
-Highly vascularized
Fibroblasts
- Star shaped w oval nucleus
- Most numerous
- Produce ECM by synthesizing/secreting mature proteoglycans, glycoproteins, precursor molecules of collagens/elastins
- Wound repair
Macrophages
- Phagocytic, derived from monocytes
- monocytes migrate from blood to tissue, then mature into macrophages (Kupffer cells-liver, Osteoclasts-bones, Microglial cells-CNS)
- very granular
- mobile
- have many lysosomes
Plasma Cells
- From differentiation of B lymphocytes
- Synthesize/secrete immunoglobulin (antibodies)
- Prominent cartwheel nucleus w well developed nucleolus
- Abundant rough ER and golgi
- Move throughout ECM
Mast Cells
- Mast cells/basophils have same progenitor in bone marrow
- Found around blood vessels
- Produce heparin (anticoagulant)
- Produce histamine (vasodilator)
Fat Cells (adipocytes)
- Storage of energy
- Protection
Pigment Cells (Melanocytes)
- Produce melanin
- Protection from UV
Extracellular Matrix
-Binds supports and surrounds cells and fibers
Fibers: -Collagen -Elastin -Reticular Fibers
Ground Substance
Collagen Fiber
- Protein collagen arranged in bundles
- Most abundant of fibers
- parallel rubbing fibrils for strength
- white/yellow
- soft/flexible/strong
- not elastic or extendable
- Vit C is cofactor for synthesis
- lack of collagen = scurvy = inadequate wound healing
Elastic Fiber
- protein elastin
- thin, yellow
- stretch and return to normal
- connect to one another
Reticular Fibers
- protein collagen and glycoproteins
- similar to collagen, thinnest/most delicate
- form reticular framework
Ground Substance
- Viscous material, holds cells together
- hyaluronic acid
- Mucopolysacharide
- Mucoproteins
Connective Tissue Classification
Embryonic CT
Adult CT: -Loose
-Dense: regular/irregular -Reticular -Elastic
Special CT: -Adipose: white/brown -Cartilage: hyaline/elastic/fibrocartilage -Bone: compact/woven/cancellous
Embryonic CT
- present in ebryo/umbilical cord
1. mesenchyme: found primarily in embryo, made of spindle shaped cells in contact w neigboring cells, mand reticular fibers w few collagen fibers
2. Mucous CT: in umbilical cord. Made of homogenous ground substance, jelly like, calld Whartons jelly
Adult CT: Loose & Dense Irregular CT
- Loose (areolar) irregular CT: -loosely arranged fibers and abundant cells
- beneath epithelia and lines internal surfaces of body
- site of inflammatory/immune responses - Dense irregular CT: -abundant fibers and few cells
- mainly collagen arranged in bundles oriented in various directions that can stand stress on organs
- In sub mucosa of intestinal tract, deeper layer of dermis
Adult CT: Dense Regular
- Ordered and densely packed arrays of fibers and cells and very little ECM
- fibers are arranged in parallel arrays and provide maximum strength
- Main functional component of tendons, ligaments, and aponeuroses
Adult CT: Reticular Tissue
-Reticular fibers provide a supporting framework for cellular constituents of various tissues and organs
Adult CT: Elastic Tissue
- Mainly composed of elastic fibers and capable of stretch and distension
- Fibers are Thinner than collagen, aranged in branching patterns
- Found in dermis, aorta, vertebral ligaments, larynx
Special CT: Adipose Tissue
-Important role in energy homeostasis
White: -predominant type in adults -serves to store energy, insulation, cushioning of vital organs, secretion of hormones -Unilocular cells w single large fat inclusion that pushes nucleus to side
Brown: -abundant in newborns ~5% of body weight, found in back by upper half of spine toward shoulders, very reduced in adults -multilocular, rich in mitochondria, surrounded by lots of blood vessels
Special CT: Hyaline Cartilage
- avascular
- surrounded by perichondrium (except in articular cartilage)
- made of chondrocytes surrounded by collagen matrix
- occurs in temporary skeleton of embryo, articular cartilage, cartilage of nose larynx trachea bronchi costal cartilages
Special CT: Elastic Cartilage
- avascular
- surrounded by perichondrium (except in articular cartilage)
- made of chondrocytes surrounded by matrix of elastic fibers and collagen fibers
- In external ear epiglottis and auditory tube
Special CT: Fibrocartilage
- Genrally avascular
- lacks perichondrium
- made of chondrocytes, fibroblasts, surrounded by collagen fibers and less rigid ECM
- Found in intervertebral discs, articular discs of knee, strenoclavicular joints, pubic symphysis
Special CT: Bone
Structure: 1.Compact/dense bone 2.Spongy/cancellous/trabecular bone based on collagen fiber organization 1. Lamellar bone (consists of lamellae made of bone matrix and osteocytes in lacuna w radiating canaliculi 2.woven/nonlamellar bone
Lamellae types:
1. Osteons/haversian system: concentric arranged lamellae around a longitudinal vascular channel
2. Interstitial lamellae: between osteons
3. Outer circumfrential lamellae: just under periosteum
4. Inner circumfrential lamellae: close to endostem
Vascular Channel Orientation:
1. Longitudinal capillaries and post capillary venules run in center of osteon called haversian canal
2. Transverse/oblique/Volkmann’s canals contain blood vessels from marrow/periosteum and connect haversian canals
Bone matrix: organic and inorganic components
Bone Cells: osteoblast and osteoclast lineage
Bone Repair After Fracture
- Neutrophils arrive to injury first, followed by macrophages that clear up injury site
- Fibroblasts and capillaires proliferate and grow into injury site
- Loos granulation tissue (scar) is formed and cartilage forms in parts of it, fibroblasts and periosteal cells contribute to this step
- Dense connective tissue and newly formed cartilage grow, covering bone at fracture site and producing soft callus. Callus helps stabilize/bind together fracture bone
- 6-12 week process
Dupuytren’s Disease
-Continued remodeling results in hypertrophic scar w excessive connective tissue contracture
