connective tissue Flashcards
9.2 Classify generalised connective tissue.
Forms of connective tissue:
- Generalised connective tissue (AKA: connective tissue proper)
- Ligaments / retinacula (thin membranous ligaments e.g. have it in knee) / fat / tendons - Specialised CT - Fluid
- Blood
- Lymph - Specialised CT - Supporting
- Cartilage
- Bone
9.1 Describe the structure, properties and functions of the three components of generalised connective tissue: cells, fibres and ground substance.
Components of connective tissue:
- Cells
- Fibres (elastin and collagen)
- Ground substance = extracellular matrix
Functions of connective tissue
- Supports other tissues (areolar and reticular CT)
- Protects organs (fat and areolar CT)
- Stores energy reserves (fat)
- Transports fluids and dissolved materials (fluid CT)
- Defends the body against invading microorganisms (fluid CT)
- Repairs damage during wound healing (fluid CT)
CLASSIFICATION OF CONNECTIVE TISSUE: Generalised CT
Connective tissue = generalised connective tissue (GCT) GCT loose --> cells + ground substance > fibres: - areolar tissue - adipose tissue - reticular tissue GCT dense --> fibres > cells + ground substance REGULAR: fibres lie in lines of stress: - ligament - tendon - aponeurosis/ fascia IRREGULAR: no pattern of fibres: - capsule - periosteum
CLASSIFICATION OF CONNECTIVE TISSUE: Specialised CT
connective tissue = specialised CT Fluid CT: - blood - lymph Supporting CT: - cartilage - bone
Cells of connective tissue: classification
Classification of cells:
- Fixed/permanent: provide long term maintenance of generalised connective tissue
- Free/transient: normally occurs in blood or bone marrow. Contribute to short term events e.g. response to injury or infection (acute inflammatory response)
Cells of connective tissue: types
Fibroblasts and fibrocytes (“fixed”)
Function:
- Produce and maintain extracellular matrix
- Promote wound contraction
Macrophages (“fixed” and “free”) = come in when body becomes ‘insulted’ e.g. injured
- Both permanent and mobile cells capable of phagocytosis (“eating” of pathogens and cell debris = so it doesn’t become an infection)
Function:
- Eliminate microorganisms and debris
- Contribute to immune reactions = stop infection
Adipose / fat cells (“fixed”)
- Contain large lipid droplet
Function: synthesise (make), store and release lipids
Mast cells (“free”)
Produce:
- Anticoagulant (similar to heparin) - having the effect of inhibiting the coagulation of the blood = prolong clotting
- Inflammatory substances (e.g. histamine, prostaglandin) which increases vascular permeability
Function: facilitate migration of cells from blood to connective tissue
- Vasodilation occurs as a response to mast cell activation
Plasma cells (“free”) White blood cells - neutrophils and lymphocytes produce antibodies to fight infection
Acute Inflammatory Response
- White blood cells (lymphocytes and monocytes) are attracted to site of injury/infection
- Mast cells release inflammatory substance → increase in permeability of blood vessel wall
- White blood cells pass into connective tissue from vessels
- Lymphocytes differentiate into plasma cells
- Monocytes differentiate into macrophages
- Swelling and bruising occur due to “leakage” of red blood cells and plasma
- Macrophages phagocytose debris
- Plasma cells immobilise infectious organisms - they produce antibodies
Extracellular matrix of generalised connective tissue
- Produced by fibroblasts
Consists of:
Fibres: provide strength and support- Collagen (very high tensile strength)
- Reticular (branched): reticular fibres are arranged in an interwoven framework that is tough and flexible called a stroma.
- Elastic (stretches easily)
Ground substance: acts as a diffusion medium and provides support - Extracellular fluid
- GAGs: glycosaminoglycans, which increase viscosity (thickness, jelly-like) of ground substance
Loose connective tissue - 1. Areolar
- Form the “packing materials” of the body: fill spaces between organs, muscles (think epi- , peri- & endomysium), nerves, blood vessels and under the skin
Areolar (loose) tissue - the only connective tissue that contains all cell types
- involved in acute inflammatory response
- present in tissue sections of almost all parts of the body
Loose connective tissue 2. Adipose
- fat cells predominate
2 types of adipose tissue: - white fat (more common): stores energy, insulate against heat loss, provide mechanical support
- brown fat: store «_space;release energy (thermogenesis = making heat)
- Adipose tissue provides padding and generates heat
- regional differences in how adipose tissue is distributed depend on age and gender
Loose connective tissue 3. Reticular
- forms a complex three-dimensional network for supportive fibres (provides supporting framework)
- functional cells (parenchyma eg lung liver cells – have a specialised function)
- reticular organs: Spleen, liver, lymph nodes, and bone marrow
- supports blood-producing cells and immune cells
Dense connective tissue: regular
- collagen fibres predominate
Regular
- found in ligaments and tendons
- very high tensile strength because:
- large number of collagen fibres
- all fibres oriented along the same lines of stressDense connective tissue: Irregular
Irregular:
- found in periosteum, some fascia
- contains collagen and elastic fibres
- function to protect and support organs incl. the skin
Specialised CT - Fluid - Blood
- Comprised of cell (red, white and platelets)
- ECM = plasma
