Lecture 10 - Connective Tissue (proper) Flashcards
What is the definition of connective tissue?
Tissue that connects, supports, binds or separates other tissues or organs
What are the 3 components of the structure of connective tissue?
Cells
Fibres
Ground substance
What are the main cells of connective tissues?
Fibroblasts
Chondrocytes
Osteocytes/osteoblasts/osteoclasts
Stem cells/progenitor cells/bone marrow/blood/adipocytes
What are the main products produced by connective tissues?
Fibres
Ground substance
What 2 components of connective tissue make up the extracellular matrix (ECM)?
Fibres + Ground substance
What fibres are commonly found in connective tissues?
Collagens
Elastin
Reticular fibres
What is ground substance made of?
Proteoglycans like Hyaluronic acid (a type of glucosaminoglycan)
What is the function of connective tissue??
Binds and supports tissues
Protection (fat as shock absorber)
Insulation (bone marrow holding warm blood)
Storing reserve fuel and cells (bone marrow and fat)
Transporting substances
Separating tissues (fascia and tendons/cartilage)
What are the 2 types of Connective Tissue Proper?
Loose connective tissue
Dense connective tissue
What is the strucutre of loose connective tissue?
1.) Multiple cell types: Fibroblast, macrophages, other WBCs, mast cells and adipocytes
2.) 2 main fibres = collagen and elastin
3.) Lots of Gel like ground substance made of: proteoglycans, Hyaluronic acid…..
What is the name given to macrophages in connective tissues?
Histiocytes
What is the function of loose connective tissue?
Acts as packing around organs
Cushions and stabilises organs
Holds vessels and everything in place
Involved in inflammation pathways (mast cells)
Where is loose connective tissue found?
Under all epithelial layers (Called the Lamina propria)
Around glands, capillaries , nerves and sinusoids
What do the cells and fibres all lie in in connective tissue?
Ground substance
What are fibroblasts?
The cells that synthesis and secrete the fibres that lie within the ground substance
Why are fibroblasts important in wound healing?
Produce scar tissue
What are myofibroblasts and what is special about them?
Modified fibroblasts
Contain actin and myosin
Responsible for wound contraction
What type of cells are the hisitocytes/macrophages?
Dendritic cells
They present foreign material to the T lymphocytes
What is the function of mast cells?
Important in the immune response
What substances to Mast cells release when activated?
Histamine (inc blood vessel permeability)
Heparin (anticoagulant)
Cytokines (attract eosinophils and neutrophils)
When do mast cells become activated?
Infection by bacteria, parasites and allergens
Get coated by IgE
Where are Mast Cells not found an why?
CNS
avoid damaging effects of oedema
What are unilocular adipocytes called?
White adipocytes
What is the structure of a white adipocytes?
Single large lipid droplet
Nucleus, cytoplasm and organelles all squeezed to one side of cell (peripheral)
What is the function of white adipocytes?
Shock absorber
Insulation
Energy reserve
What are mulitlocular adipocytes called?
Brown adipocytes
What is the structure of brown adipocytes?
Lots of small lipids droplets
Nucleus, cytoplasm and organelles squeezed to CENTER of cell
What is the function of brown adipocytes?
Insuliton
Energy reserve
How does the number of mitochondria differ between white and brown adipose?
Brown has more mitochondria
In neonates, the ETC and ATP synthesis are uncoupled to generate lots of heat
How many types of collagen are there?
Type I
Type II
Type III
Type IV
What is the structure of Type 1 collagen?
Fibrils form Fibres
What is the structure of Type II collagen?
Fibrils do NOT FORM FIBRES
What is the structure of Type III collagen?
Fibrils form fibres around muscles, nerve cells and in lymphatic tissues and lymphatic organs and in tendons
What is Type III collagen also called?
(Collagen fibres around muscle and nerve cells….)
Reticulin (reticular fibres)
Reticular fibres are mainly made of Type III collagen
What is the structure of Type IV collagen?
Unique form present in only the BASEMENT MEMBRANE
What type of fibre is not found in Areolar/loose connective tissue?
Reticular fibres/Reticulin
What is the role of collagen?
Flexible with high tensile strength
What is the role of reticular fibres?
Provide supporting/spongy framework
What is the role of elastin?
Allows tissues to recoil after stretch or distension
Where is loose connective tissue found?
Beneath epithelia (facilitates diffusion)
Associated with epithelia of glands
Around small blood vessels
What is the important role of connective tissues?
To challenge pathogens that have breached the epithelia so they can be destroyed by the immune system
Give an example where loose connective tissue can be found:
Superficial layer of the dermis in the skin
Submucosa of colon
What is ground substance?
A viscous, clear substance with a high water content
What does ground substance contain?
Water
Proteoglycans
What are proteoglycans?
Large macromolecules
What is the structure of a Proteoglycan?
Has glycosaminoglycans covalently bound to a core protein
What is the name of a special Glycosaminoglycan found in the ground substance of cartilage?
Hyaluronic acid
What is the role of glycosaminoglcyans in ground substance?
Attract water to form hydrated gel which allows for rapid diffusion and compression resistance
What type of connective tissue is Mucoid connective tissue?
Loose connective tissue
What is the strucutre of mucoid connective tissue?
Thin collagen III fibres
Immature fibroblasts
Jelly like ground substance
Where is mucoid connective tissue found?
Umbilical cord
What are the 2 types of Dense connective tissue?
Regular
Irregular
How are the collagen fibres arranged in dense irregular connective tissue?
Irregularly orientated in all directions
What is the advantage of the collagen fibres being randomly orientated in the dense irregular connective tissue in the lower part of the dermis of the skin?
Skin can resist forces in multiple direction preventing tearing
Elastic fibres allow skin to stretch and restore back to shape
How are the collagen bundles arranged in Regular dense connective tissue?
Lie in parallel
What is an example of regular dense connective tissue?
Tendon
Lie in line with the tensile force exert by the muscle to move the bone
What is a myotendinous junction?
Area where skeletal muscle fibres connect with tendon collage bundles
What types of collagen are present in tendons?
Collagen I 70%
Collagen III (Reticulin) 30%
What are ligaments?
Regular dense connective tissue joining bone to bone
What is it called when collagen bundles of a ligament are surrounded by loose connective tissue?
Fascicle
What is fascia?
A connective tissue
What are the 3 types of fascia?
Superficial
Deep
Visceral or parietal
What is superficial fascia?
Fascia found directly under skin and above the adipose layers
What is deep fascia?
Fascia that surrounds bones, nerves, muscles and blood vessels
What is visceral fascia?
Fascia surrounding organs in cavities like the abdomen
What is Parietal fascia?
Tissues that surround the wall of cavities in the body just outside the parietal layer of serosa
What type of connective tissue is fascia?
Dense regular connective tissue
Can resist great unidirectional tensions
What causes Scurvy?
Vitamin C deficiency
How is vitamin C relevant to collagen?
Needed as a cofactor for an enzyme which hydroxylates proline and lysine
Needed so collagen fibrils can form lots of hydrogen bonds between each other so the collagen fibres are strong
What happens to the procollagen when vitamin C is deficient?
No Hydroxylation of proline and lysine so weak forces between collagen fibrils
Weak collagen
What are the signs and symptoms of scurvy?
Poor wound being
Impaired bone formation
Gum disease
Bleeding
Weakness and fatigue
What causes Marfan’s syndrome?
Mutation of Fibrillin 1 gene
(Autosomal dominant)
What is affected a a result of the mutation in the Fibrillin 1 gene in Marfan’s syndrome?
Elastic tissues
What are the signs of Marfan’s syndrome?
Abnormally tall
Arachnodactyly (long slender and curved fingers and very long arms)
Frequent joint dislocation
What are sufferers of Marfan’s syndrome at significant risk of?
Why?
Catastrophic aortic rupture
Less functional elastin in the tunica media, less ability to elastically recoil so aneurysm occurs, thin walls = more prone to rupture
Where are elastic fibres important?
Dermis
Artery walls
Lungs
Sites with elastic cartilage
Why are elastic fibres being broken bad?
Elastin is not replaced in an adult
What is Osteogenesis Imperfecta caused by?
Mutation in COL1A or COL2A gene
What is affected in Osteogenesis imperfecta?
Mutation of Collagen I or Collagen II fibres
What does osteogenesis imperfecta cause?
Weak brittle bones prone to fractures
Short stature
BLUE SCLERA
Poor teeth development
Hyper mobility (loos joints)
What is the normal function of Fibrillin 1?
Binds to elastin to allow for elastic recoil
