Wk3 L2 - Connective Tissue Flashcards
LO
- To understand and be able to recognise the main fibrous connective tissues: loose (areolar), dense irregular, dense regular
- To understand and be able to recognise the main connective tissue fibres: collagen, reticular, elastic
- To understand and be able to recognise the specialised connective
- tissues: blood, adipose, cartilage, bone
- To understand and be able to recognise the different types of cells found in connective tissues: fibroblasts, other cells eg. macrophages
CT
- Connects and supports other tissue types structurally and functionally (different types for different functions)
- Conatins blood and lymphatic vessels (exchange water, nutrients waste, etc)
- Consists of cells and ECM (cells spread apart and surrounded by ECM)
- ECM = protein fibres and ground substance
CT classification
CT proper:
- ECM contains CT fibres
- Classified based on relative abundance of cells and fibres
Specialised examples:
- Adipose
- Bone
- Blood
- Cartilage
CT proper
2 Subtypes based on abundance of cells, fibres and ground
Dense:
- Regular Vs Irregular
Loose:
Cells of CT proper
Resident:
* Fibroblast
* Adipocyte
* Mesenchymal stem cells
* Macrophage
* Mast cells
Transient:
Immune cells
* Lymphocytes
* Neutrophils
* Basophils
* Eosinophils
* Monocytes
* Plasma cells
Fibroblast
- Most common CT proper cell
- Produces Extracellular fibers (Collagen, elastin, reticular)
- Produce and maintain ground substance
- Active = secretion
- Inactive = Fibrocyte
Adipocyte
- Specialised CT cells, accumulates and stores fat in cytoplasm
- Resident
- Found in loose CT (can form large amounts = adipose tissue)
Under a LM:
- Large round cells
- Nucleus flattened and to side of cell
Mesenchymal Stem cells
- Reside in CT of many organs
- Multipotent
- Differentiate into cells for tissue repair
Exampels
- Fibroblast and endothelial cells
Macrophages
- Phagocytic cells
- Abundant lysosomes
- Immune defence
Mast cells
- Develop in bone marrow, differentiate in CT
- Granules contain inflammatory mediations (histamine)
- Immune defence
ECM of CT
- 3 types of fibres
Collagen, elastin and reticular fibres: - Made of protein
- Produced ny fibroblasts
- Provide strength, structure and elasticity (depending on tissue)
Ground Substance:
- Water, proteoglycans, glycoproteins, glycosaminoglycans
- Produced by fibroblasts
- Allows diffusion of ions and molecules
.
- ECM and cells vary, depending on the function of the tissue
Ground substance
Viscous, clear substance (lost during tissue preparation)
Glycosaminoglycans:
- negatively charged
- Rigid & strong
- Attract water, form hydrated gel
- Cushioning and strength
- Resists compression
- Allows diffusion
Proteoglycans:
- glycosaminoglycans attached to core protein
Multiadhesive glycoproteins:
- Stabilise the extracellular matrix and link it to the cell surface
eg. fibronectin, laminin, osteopontin
Collagen fibres
- Most abundant of the CT fibres
- Flexible, extremely high tensile strength
- Made up of bundles of individual collagen fibres
- Fibres are made up of fibrils
Under LM:
- Appears thick and wavy
Collagen
- Collagen fibrils are made up of collagen molecules
- 29 different types of collagen molecules
Reticular fibres
- Supporting framework for tissues in certain organs and adipose
- Mechanical stength
- Hard to see under LM without special stains (silver stain)
- Made up of collagen fibrils containing type 3 molecules
- Produced by reticular cells (specialised fibroblasts)
Elastic Fibres
Allows tissue to return to shape after stretching
Thin fibres in branching 3D network (Interspersed with collagen, limiting degree of stretching)
Made up of elastin molecules joined together (Natural tendency to coil, causing contraction of fiibre)
Tissue section Vs Spread preperation
Section:
- Cut through cells & tissue components
Spread:
- Tissue remains whole
- Can see the path of blood vessels & fibres
through the tissue
Sectioning = cutting thin slices of tissue so thin enough to see through
Spread preparation = if tissue thin enough already, spread whole tissue tight over slide
Mesentary
Thin layer of loose CT between 2 layers of simple squamous epithelium
Already thin enough for spread preperation
Loose CT
Highly cellular
Sparse collagen
Abundant ground substance (occupies more volume than fibres)
Provides medium for oxygen, CO2, waste, nutrients
Mainly found beneath epithelia.
Dense CT
- Mainly Collagen fibres, few cells, little ground substance
Categorised based on organisation of collagen fibres:
* Regular (parallel fibres)
* Irregular (Various directions)
Dense irregular CT
- Few cells, mostly fibroblasts . Little ground substance
- Lots of collagen fibres (provide strength)
- Fibres arranged in bundles & oriented in range of directions
- structural strength in multiple directions (prevent tearing)
9/10 on spot test
Dense Regular
- Few cells, mostly fibroblasts, little ground substance
- Mainly collagen fibres tightly packed parallel (maximum strength in one direction)
- Main component of tendons & ligaments
Blood
- Specialised CT
- Fluid CT that circulates through CV system
Cells and plasma:
- Erythrocytes
- Lymphocytes
- Platelets
Adipose
- Specialised CT
- Consists of accumulations of adipocytes (when dominant cell = adipose tissue)
Functions:
- Energy storage (lipid droplets)
- Thermal insulation
- Physical cushioning of organs
and tissues
- Hormone secretion
Cartilage
- Specialised tissue
- Consists of chondrocytes in a highly
- specialised extracellular matrix
- Avascular
- Solid and firm
- > 95% extracellular matrix (by volume)
3 Types:
* Hyaline
* Elastic
* Fibrous
All types produced by chondrocytes, sitting in lacunae
