Connective And Adipose Tissue Flashcards
What are five functions of connective tissue?
Connects cells to form tissues
Provides a medium for transportation of nutrients/wastes
Protection between tissues and organs and insulation (adipose)
Storage (adipose)
Defence against infection - loose connective tissue (blood, lymph, fixed and wandering cells)
Wound healing - macrophages, fibroblasts
What is ground substance?
Clear, viscous substance with high water content. Composed of proteoglycans
What are proteoglycans?
Macromolecules consisting of core protein covalently bound to glycosaminoglcans (GAGs)
What are the function of GAGs?
Attract water to form a hydrated gel which resists compression and permits rapid diffusion
What is hyaluronic acid? And where is it present?
A unique GAG - binds to core protein by a link protein
Present in cartilage
What is extracellular matrix?
Ground substance + fibres
Where is loose connective tissue found?
Mainly located beneath epithelia (facilitate diffusion), associated with gland epithelium and around small blood vessels
What are the features of loose connective tissue? (4)
Many cells
Viscous, gel-like consistency
Sparse collagen fibres
Abundant ground substance
What are the feature of dense connective tissue? (3)
Few cells - mostly fibroblasts
Many collagen fibres
Little ground substance
Where is regular dense connective tissue found?
Tendons (connect muscle to bone)
Ligaments (connect bone to bone)
Aponeuroses
What is regular dense connective tissue?
Collagen fibres arranged in densely packed, parallel bundles (with fibroblast in between).
Designed to withstand stress in a single direction
Where is irregular dense connective tissue found?
The submucosa of the intestine and deep layer of dermis
What is irregular dense connective tissue?
Collagen arranged in bundles orientated in various directions (fibroblasts between bundles).
Designed to withstand pressure in multiple directions.
What is a fascicles?
Bundle of parallel collagen fibres
What are wandering cells?
Blood cells
What cells are present in connective tissue?
Fibroblasts Mast cells Macrophages Adipocytes Mesenchymal stem cells
What do fibroblasts do?
Synthesise and secrete ground substance and fibres (procollagen).
What are myofibroblasts?
Modified fibroblasts - contain actin - responsible for wound contraction when tissue loss has occurred
What are macrophages?
Derived from monocytes
Phagocytic - degrade foreign organisms/cell debris
Also act as APC for T lymphocytes
What are mast cells?
Abundant in granules containing histamine (increase blood vessel permeability), heparin (anticoagulant) and substances that attract neutrophils.
Mast cells are coated with IgE - binds allergens - causes release if granules - result in immediate hypersensitivity reactions
Elastic fibres consist of what?
Elastin, surrounded by microfibrils called fibrillin
Where are elastic fibres important in connective tissue?
Dermis, artery walls, lungs and sites bearing elastic cartilage
What is marfans syndrome?
An autosomal dominant disorder where there is abnormal expression of fibrillin - abnormal elastic tissue.
Sufferers are abnormally tall, exhibit arachnodactyly, frequent joint dislocation
What type of fat cells are more common?
White
What are white fat cells?
Cells filled almost completely with one lipid droplet - cytoplasm and nucleus displaced to the side of the cell.
Act as a fuel reserve, role in thermal insulation and shock absorption
What are brown fat cells?
Multilocular adipose cells - contain multiple lipid droplets and a central nucleus.
Brown colour due to rich vascular supply and abundant mitochondria.
High respiratory capacity for heat generation
Where are brown fat cells found?
Found close to the scapula, sternum and axillae (especially in newborns).
Also present in the upper chest and neck of adults
How is regular dense connective tissue arranged in ligaments?
Parallel collagen fibres densely packed but undulate and are arranged in fascicles which are separated by loose connective tissue
What are aponeuroses?
A flat sheet of regular dense connective tissue with bundles of collagen fibres in one layer arranged at 90degree angles to those in adjacent layers
What vitamin is needed for intracellular procollagen production?
Vitamin C
What disease can be caused by vitamin C deficiency?
Scurvy - vitamin c acts as a cofactor for hydroxylation of proline and lysine (use in collagen) results in poor wound healing and impaired bone formation
What type of collagen is present in reticular fibres? And where are these fibres seen?
Type 3 collagen
Present in lymph nodes - form irregular structure throughout node with lymphocytes densely packed in spaces between fibres (spongy)
pH is logarithmic, so 1 unit change equates to what?
A tenfold change in hydrogen ion concentration
What is the pH limit of survival?
6.8-7.8
At pH 7, what is the hydrogen ion concentration?
100 nM/L
