Ch. 5 Connective Tissue Flashcards
Made of cells and extracellular matrix
What composes extracellular matrix?
- fibers
- ground substance
- tissue
- special proteins
What is Embryonic connective tissue?
- mesenchyme loosely organized
- mucous connective tiss-present in umbilical cord (Wharton’s jelly)
What are the Specialized Connective Tissue?
- Adipose tissue
- blood
- bone
- cartilage
- hemopoetic tissue
- lymp tiss
What composes the Connective Tissue Proper?
- Loose Connective tissue
- Dense connective tissue:
Describe Loose Connective
- Site of inflammation and immune response
- thin, sparse collagen fibers
- beneath epithelia that covers body surfaces and internal surfaces
Describe Dense connective
- Dense irregular: abundant fibers, few cells. mostly collagen fibers
- provides strenghth. -random organization, thick
- Spindle fibroblast
- Dense regular: ordered, densely packed arrays of fibers and cells
- tendons, ligaments, aponeurisis
what are the 3 types of Conn tiss fibers?
- Collagen fibers: flexible, high tensile strenghth, wavy structures
- collagen fibrils - Reticular fibers: Collagen fibrils of narrower diameter and Type III collagen, -meshlike pattern
3.Elastic fibers: thinner than collagen fibers. 3D branching pattern. interwoven w/ collagen, to prevent tearing, produced by smooth muscle cells and fibroblast
what is ground substance?
little shape/morphological structure
what is extracellular matrix?
fibrous proteins, proteoglycans, glycoproteins
What are connective tissue cells?
-fibroblasts -adipose cells -macrophage(langhan’scell) -adipose cells -myofibroblast -mast cells -basophils -adipose cell -undiff mesenchymal cells and pericytes -plasma cells -eosinphils,monocytes,&neutrophils
Collagen Fibers and Fibrils
- most abundant type
- flexible, high tensile strength-due to covalent bonds between adjacent rows
- Fibrils are the subunits
- have 68 nm banding pattern
- made of tropocollagen - Right-handed triple helix = alpha-chains
- hydroxyproline/hydroxylysine (w/sugar) + gycine+proline= glycoprotein
- 19 diffrt types of collagen:
- type 1: loose/dense connective tissue
- type2: hyaline & elastic cartilage
- type 4
- type 9
-
Collagen fiber formation
- Inside cell, in fibroblast:
- procollagen precursor - Outside cell
- Enzymatic activity to make collagen
Reticular Fibers:
*provide a supporting framework for the cellular constituents of various tissues and organs
- consists of collagen fibrils of type III collagen
- mesh-like pattern or network
- produced by reticular cell of fibroblasts and Schwann cells
- thread-like appearance in H&E stain
- found at boundary of connective tiss and epithelium
Elastic Fibers
- Allows tissues to respond to stretch and distension
- Thinner, branching pattern 3D
- interwoven w/ coll fibers to prevent tearing
- produced by fibroblast and smooth muscle cells, same process as collagen prod.
- contains desmosine&isodesmosine for covalent bonding
- is a major extracellular substance in in vertebral ligaments, larynx & elastic arteries
- interspersed w/ collagen fibers
- in arteries, is in form of fenestrated lamellae of smooth muscle cells
-can be distinguished from Collagen fibril when refracted in H&E stain
- Components:
- Elastin(center core), protein rich in proline and glycine
- Fibrilin(surrounding), glycoprotein forming fine microfibrils
- play an impt role in formation of elastin sheets or lamellae, like blood vessels.
-during growth, microfibrils become entrapped w/in newly deposited elastin
-
Ground substance
- occupies space between cells & fibers
- viscous, slippery, clear substance of high water content
- lost in H&E stain
- consists of proteoglycans and hyaluronic acid
- w/ Glycoaminoglycans, responsible for the physical properties of ground substances - permits diffusion of O2 and nutrients between the microvasulature and cellular components of tissue
Extracellular matrix
- a complex structural network that includes fibrous proteins, proteoglycans and several glycoproteins.
- Fibroblast attachment functions in cellular movement
What are the permanent residents of connective tissue cells?
- fibroblasts,
- myofibroblast
- macrophage
- adipose cells
- mast cells
- undiff mesenchymal cells
What are the wandering residents of connective tissue cells?
- lymphocytes
- plasma cells
- neutrophils
- eosinophils
- basophils
- monocytes
Fibroblast
- principle cell type of conn. tiss
- syn of collagen, elastic, reticular fibers, complex carbs of ground substance
- nearby to collagen fibers
- only nucleas visible in H&E stain
- elongated,disklike structure
- interact w/epithelium in normal renewal and differentiation
Myofibroblast
- displays like fibroblast and smooth muscle cells
- elongate, spindly conn. tiss. cell
- contain bundles of actin filament,rER, Golgi, and dense bodies
- lacks surrounding basal lamina
- exists as an isolated cell, with gap junctions
- respond to tissue damage and repair
Macrophage
- phagocytotic cells derived from monocytes
- aka Tissue Histiocytes
- indented kidney-shaped nucleus.
- exhibits numerous folds and finger-like projections
- contains Golgi ap, rER,sER, mito, secretory vesicles, lysosomes
- immune response, anaphylaxis, inflammation
- phagocytosis as defense and cleanup activity
- as an antigen-presenting cell, presents MHC II molecules to signal CD4+ T lymphocyte for immune response
*Foreign Body Giant Cells: when encounter larger foreigners, they may fuse to form a large cell with 100 nuclei that engulfs the foreigner
Mast cells and Basophils
- large, ovoid cells(20-30um diameter) with spherical nucleus, filled with large basophilic granules:
- histamine and slow-reacting substance of anaphylaxis
- Eosinophil chemotactic factor(ECF) and Neutrophil chemotactic facto (NCF)
-IMMEDIATE:hypersensitivity rxns, allergy, anaphylaxis
- exhibits numerous mictovilli and folds
- displays small amts of rER, mito, and Golgi ap.
- contain heparin
- release granules when stimulated by foreign antigen.
- plasma cells proliferate producing antibodies like immunoglobins, which then bind to receptors on mast cell. - synthesize leukotrienes and prostaglandin D
- numerous in conn. tiss of skin and mucous membranes but not in brain and spinal cord
*basophils have secretory granules. in certain immune rxns, they leave circulation and function in conn. tiss.
Adipose cells
- throughout loose conn. tiss as individ or groups called adipose tiss
- to store neutral fat
Pericytes
- aka adventitial cells or perivascular mesenchymal cell
- found wrapped around capillaries/venules
- may differentiate into muscle cells
- primary source of new cells in healing wounds
- with fibroblasts and endothelial cells, give rise to additional cells that form new connective tissue and blood vessels.
Lymphocytes:
3 functional cell types:
- smallest cells in conn. tiss
- thin rim cytoplasm
- found throughout, increase at sites of tiss inflammation
- most in lamina propia of respiratory and gastrointestinal tracts
- express cluster of differentiation (CD) proteins
- T lymphocytes by presence of CD2,3,7 and TCRs
- cell-mediated immunity
- B lymphocytes by CD9,19,20,24
- recognize antigens, antibody-mediated(humoral) immunity.
- Plasma cells-has hemochromatin for syn of large amts of protein
- recognize antigens, antibody-mediated(humoral) immunity.
- Natural killer lymphocytes expressing CD16,56,94
- destroy virus-infected cells and some tumor cells by cytotoxic mech
Eosinphils, monocytes, neutrophils
- rapidly migrate from blood in immune response to conn tiss.
- acute inflammatory response
Undiff mesenchymal cells
thought to give rise to differentiated cells that function in repair and form of new tiss as in wound healing
plasma cell
- prominent in loose conn
- normal component of salivary glands, lymph nodes, and hemopoetic tissue
- large, ovoid with lots of cytoplasm
- nucleus spherical and offset positioned and small
