BL Connective Tissue Flashcards
What is connective tissue?
Tissue that supports, protects + connects other tissues and organs in the body
Made of cells, fibre + ground substance
What are the 3 components of connective tissue?
Cells
Fibres
Ground substance
What are the main cells in connective tissue?
Fibroblasts
Chondrocytes
Osteocytes/blasts/clasts
Stem cells
Adipocytes
Reticular cells - in lymphatic vessels
What are the 3 fibres in connective tissue?
Collagen
Elastin
Reticulin
What are the 3 groups of connective tissue?
Connective tissue proper
Fluid connective tissue
Supportive connecting tissue
What are types of connective tissue proper?
Loose
Dense
What are the types of fluid connective tissue?
Blood
Lymph
What are the types of supportive connecting tissue?
Cartilage
Bone
What is ground substance?
Gel containing protein glycoproteins, glycoaminoglycans, lipids + water
What is extracellular matrix?
Ground substance and fibres linked to form a complex network
Function of fibroblasts
Produce collagen + fibres of ground substance
Functions of connective tissue
- Binding + supporting
- Protection
- Insulating
- Storage - bone marrow + adipose
-
Transporting substances
Separation of tissue
What is the least specialised connective tissue in adults?
Loose/areolar connective tissue
What are the two types of dense connective tissue?
Describe each type
Irregular - fibres running in different direction
Regular - fibres running parallel to each other
Structure of loose connective tissue
- Cells - fibroblasts, macrophages, mast cells, adipocytes
- Fibres - collagenous + elastic
- Ground substance
Functions of loose connective tissue
- Holds vessels
- Permits cell migration
- Involved in inflammation pathways
- Packaging around organs
- Shock absorber
- Stabilises organs - surrounds all organs
What do mast cells contain?
Histamines - ^ blood vessel wall permeability
Heparin - anticoagulant
Cytokines - attract eosinophils and neutrophils
Function of histamines
Increase blood vessel wall permeability
What do mast cells look like?
Basophils
Many vesicles
What is a unilocular adipocytes?
A large single lipid droplet
Nucleus, cytoplasm + organelles all sequenced to one side of cell
Why do adipocytes appear white in H&E staining?
Xylene + toluene strip out the fats
Function of white adipose tissue
Padding
Shock absorber
Insulation
Energy reserve
What is a multilocular adipocyte?
Multiple small lipid drops
Nucleus, cytoplasm + organelle squeezed to centre of cell
Function of brown adipose tissue
Insulation
Energy reserve
Nucleus in white vs adipose tissue
- white: nucleus pushed to side
- brown: central nucleus
What type of adipose tissue has the most mitochondria?
Brown
What are adipose cells generated from?
Immature fibroblasts
Mesenchymal stem cells
Who is brown adipose tissue found in?
Neonates
Young children
Upper backs of adults
Lipid breakdown in white adipose tissue
Slow
Heat only generated after shivering reflex
Why do babies have brown adipose tissue?
Unable to shiver
How does brown adipose generate heat?
1- noradrenaline released in response to cold
2- noradrenaline activates lipase: TAG > fatty acids
3- fatty acids activate UCP1 (thermogenin)
4- UCP1 uncouples ETC
5- H+ transported back to mitochondria
6- energy released as extra heat
What does brown adipose tissue contain that allows heat generation?
Thermogenin (UCP1) - physiological uncoupler
What are the 4 types of collagen?
-
Type I - most common
- in tendons, skin dermis -
Type II - fibrils don’t form fibres
- in hyaline + elastic cartilage -
Type III - reticulin
- fibres around muscles + nerves
+ within lymphathic tissues
-Type IV - in basement membrane
What is the most common type of collagen?
Type I
What collagen is present in hyaline + elastic cartilage?
Type II
What type of collagen is reticulin?
Type III
What type of collagen is in the basement membrane?
IV
What fibre is absent in loose connective tissue?
Reticulin
Functions of the fibres in connective tissue
- collagen - flexible with high tensile strength
- reticulin supportive framework
- elastin - recoil after stretch
Where is loose connective tissue located?
Around small blood vessels
Beneath epithelia
Associated with epithelium of glands
What is proteoglycans?
Large macromolecule consisting of a core protein which glycoaminoglycans are covalent bound
What are glycoaminoglycans?
Example
Long chained polysaccharides
hyaluronic acids
Function of irregular dense tissue
- Prevents tearing - Irregular arrangement resists forces in multiple directions
- Stretch + recoil - due to elastic fibres
Structure of mucoid connective tissue
- Cells - immature fibroblasts
- Fibres - collagen II fibres
- Ground substance - hylauronic acid
Where is mucoid connective tissue found?
Umbilical cord
Vitreous humour of eye
Examples of locations dense irregular connective tissue
Deep layer of dermis
Submcosa of intestine
Examples of locations of dense regular connective tissue
Tendons
Ligaments
Aponeuroses
What type of collagen is in dense connective tissue?
Collagen I
Types of fascia
Superficial
Deep
Visceral or parietal
Structure of fascia
Sheet of fibrous connective tissue containing closely packed bundles of collagen fibres orientated in a wavy pattern parallel to direction of pul
What clinical conditions result due to connective tissue issues?
Scurvy
Marfan’s syndrome
Osteogenesis imperfecta
What is elastin surrounded by?
Fibrillin
Distinguish between the structure of loose and dense connective tissue
Loose - many cells
- sparse collagen fibres
- abundant ground substance
Dense - few cells (nearly all fibroblasts)
- many collagen fibres
- little ground substance
Where is connective tissue located?
At the sites where pathogens can be destroyed by cells of the immune system
2 examples of loose connective tissue
Superficial dermis of skin
Submucosa of colon
Describe the structure of ligaments
Collagen bundles densely packed in parallel arrangements
Are arranged in fascicles
What germ layer to most connective tissue cells originate from?
Mesoderm
Structure of collagen
- 3 alpha polypeptide chains
- repeating structure with glycine in every 3rd position
- glycine lie in middle of helix
What does abnormal collagen type I result in?
Osteogenesis imperfecta
What are the layers of the basement membrane?
Basal lamina
Reticular lamina