Connective Tissue And Adipose Tissue Flashcards
What are the functions of connective tissue?
- Binding and storing
- Protecting - bones protecting vital organs
- Insulating (fat underlying skin)
- Transporting substances (blood and interstitium
- Storing fuel reserves and cells
- Separation of tissues (fascia and tendons and cartilage)
What are the different types of connective tissue?
- Loose connective tissue, also known as areola tissue, areola means little space e.g. lamina propria in mucosal membrane
- Dense connective tissue also known as fibrous collagenous tissue and it has two types
- regular - fibres running parallel to each other
Tendons and ligaments - irregular - fibres running in different directions
- fascia - a thin sheath that separates muscle from other tissues
- Aponeurosis - a thin sheath that connect muscle to muscle
Pg 41
What is the function of the loose connective tissue?
- holds vessels that supply fluid
- permits cell migration
- involved in inflammation pathways
- acts as packaging around organs
- Cushions and stabilises organs
What are the 4 main cells found in the loose connective tissue?
- fibroblast
- macrophages
- mast cells
- adipocytes
What is the function of fibroblasts?
- it synthesises and secretes fibres that are found in the ground substance (extracellular matrix)
- they are important in wound healing and are the cells responsible for formation of scar tissue.
Pg 14
What can fibroblast be converted to?
- Myofibroblast
- modified fibroblast that contains actin and myosin. They are responsible for wound contraction when tissues are lost.
What is the role of macrophages in loose connective tissue?
- Move into loose connective tissue, especially when there is local inflammation.
- They are phagocytic and can degrade foreign organisms and debris
- They are antigen presenting cells and they can present foreign materials to B and T lymphocytes of the immune system
Pg 15
What is found in the cytoplasm of mast cells in loose connective tissue?
Contains abundant granules
Histamines - increases blood vessel wall permeability
Heparin - anticoagulant
Cytokines - attracts basophils and eosinophils
Pg 16
How does the mast cell work?
- The cell becomes coated with IgE molecules which specifically bind allergens
- When allergens cross-link theses surface bound IgE molecules p, the contents of the granules are rapidly released.
Pg 16
What are the different types of adipocytes?
- Unilocular adipocytes
2. Multilocular adipocytes
Where are unilocular adipocytes (white adipose tissue) found and what are there structures and functions ?
- Most adipocytes in loose connective tissue is white/yellow (white adipocytes)
- normal number of mitochondria
- enormous droplet of lipid with the nucleus, cytoplasm and organelles squeezed to one side
- padding and shock absorber, insulating and energy reserve.
- in adults lipid breakdown is slow and generates heat through shivering reflex
Pg 17
What are multilocular adipocytes (brown adipose tissue) and what is its structure and function?
- Multiple small lipid droplets, with the nucleus, cytoplasm and organelles squeezed into the centre of the cell
- Increased mitochondria
- insulation and energy reserve
- very few found in adults
- found in neonates and infants, lipid breakdown is accelerated and oxidative phosphorylation is uncoupled to generate heat
What are the four different fibres?
- Collagen - multiple types, type 1 is the most important and common
- Elastin - made up of hydrophobic amino acids - most common in aorta, lungs and skin
- Reticulin - different type of collagen fibre, most common in lymphatic system
- Fibrillin - glycoproteins essential for the construction of elastin fibres (wherever elastin is found)
What are the four types of collagen.
- Type 1 - most widely distributed, fibrils aggregate into fibres and fibre bundles (e.g. tendons, capsule of organs and skin dermis)
- Type ll - fibrils do not form fibres (hyaline and elastic cartilage)
- Type lll - fibrils form fibres around muscle and nerve cells and within lymphatic tissues and lymphatic organs (e.g. spleen) and in tendons. It is called reticulin.
- Type lV - unique form present in basement membrane ( considered part of epithelial tissues)
What are the different roles of the fibres in connective tissue?
Collage - flexibility and high tensile strength
Elastin - allows tissue to recoil after stretch or distension
Reticular/rectulin - provides supporting framework/sponge ( not found in loose/areolar tissue, only found in lymphatic system).
What is found in ground substance that allows for its structure and function?
- it is viscous, clear and slippery feel ( has high water content
- Composed of proteoglycans ( large macromolecule consisting of a core protein with glycosaminoglycans covalently bound to ).
- Glycosaminoglycans (GAGs) are long chain polysaccharides and attract water to form hydrated gel
- A unique GAG is hyaluronic acid which is bound to proteoglycans by link protein to form a giant hydrophilic macromolecule.
What is important in the structure of proteoglycans
- Hyaluronate is key
- GAGs (chondroitin and keratan sulfate) are attached to the core protein
- In turn these are attached to hyaluronate.
- The sugar moieties attract water, but make the ground substance ‘sticky and slippery at the same time.
Pg 29
Where can dense irregular connective tissue be found?
- The superficial layer of the dermis
- the skin can resist forces in multiple directions, preventing tearing
- the elastic fibres allow for a degree of stretch and restoration to original shape after skin is bent and folded.
Pg 31-32
What is an example of dense regular connective tissue and what is its function?
- Tendons - connect muscle to bone
- the collagen bundles lie parallel, densely packed formation in line with the tensile force exerted by the muscle
- rows of elongated flattens fibroblast lie between the collagen bundles
What is the myotendious junction?
Pg 34
What is key in the tendon anatomy?
- forces can be transmitted along collagen bundles because they glide over each other
- mainly made up of water
The collagen is
70% collagen l
30% collage lll
What is another example of dense regular connective tissue?
- Ligaments
- Connects bone to bone
- Parallel collagen fibres
- Not straight but undulated (wavy)
- Wrapped in loose connective tissues - fascicles
Pg 37-38
What is the three types of Fascia?
Fascia is a connective tissue
- Superficial (on the surface)
- Deep (underneath something else)
- Visceral or parietal (right next to an organ or next to the skin)
What is the fascia made up of?
- Fascia is made up of fibrous connective tissue containing closely packed bundles of collagen fibres oriented in wavy pattern parallel to the direction of pull.
- Flexible
- Able to resist great unidirectional tension forces
What is the Aponeuroses?
- Pearly white fibrous tissue
- Attaches:
- flat muscles to muscles
- tendon to tendon
- tendon to ligament
Examples
- Head
- Abdomen
- Foot
- Hand
What is the need for vitamin C?
- It is required for the intracellular production of pro collagen, it is involved as a co-factor for the enzyme that hydroxylates proline and lysine. ( which helps to form procollagen which is packaged, released and modified into collagen outside of the cell)
- Fibroblast secretes procollagen that is converted to collagen molecules outside the cell and the collagen molecules aggregate to form final collagen fibrils.
What happens when there is no vitamin C?
- Collagen formation is disrupted
- Vitamin C deficiency leads to scurvy, a condition that includes
- poor wound healing
- impaired bone formation (strong collagen fibres is needed to make good bones
- it is the hydroxylation process that is damaged, lysine hydroxylase requires vitamin C as its co-factor. Pg45
What occurs to the collagen is Scurvy?
- The thin collagen fibrils aggregate in some areas to form thick collagen fibrils.
- The majority don’t aggregate and they remain as fibrils, it doesn’t come together and had no strength.
- The collagen triple helix cannot be formed.
What are the symptoms and signs of scurvy?
- Gum disease (weak gums that bleed)
- Bruising of the skin
- Bleeding
- Poor wound healing
What is marfan’s syndrome ?
- Autosomal dominant disorder in which expression of fibrillin 1 gene is affected such that elastic tissue is abnormal
What are the signs and symptoms of marfan’s syndrome?
- Individual is abnormally tall
- Exhibits arachnodactyly - fingers and toes are very long and spider like, long limbs (legs and arms) and normal sized aorta.
- Frequent joint dislocations
- Risk of catastrophic aortic rupture - haven’t got enough elastin in the aorta
What are the key concepts about elastic fibres?
- Elastin is a primary component of elastic fibres, but it enfolds and is surrounded by micro fibrils called fibrillin.
- fibrillin is layed out first and then elastin grows in and around it
Sites at which elastic fibres have an important role
- dermis
- artery walls
- lungs
- sites bearing elastic cartilage
What happens when you pull elastic fibres?
- They straighten out and the have cross links between them and the cross links hold them in that position until the force is take away
- When the force is taken away the elastin fibres spring back.
- If the fibres are degraded or broken down by an enzyme, it will destroy the link and the rebound capacity
- if you find amino acids desmosimes and isodesmosime in the urine that means the elastic fibres are broken down
What are the three layers of blood vessels?
- Tunica intima (in distinct endothelial cells) : epithelial layer next to the blood.
- Tunic media (elastin lamellae): have elastic fibres so when the blood comes through they expand to take your extra volume of the blood.
- Tunica adventitia (collagen): has a lot of smooth muscle and collagen on the outside and the collagen stops the vessel from getting too big and so it doesn’t burst
- it is the smooth muscle in the aorta that produces elastin, collagen and matrix not fibroblast
Pg 50-53
What is osteogenesis imperfecta?
- Encompasses a number of different genetic aetiologies.
- Mild to serve disease
- Due to mutated collagen, fibres that do not knot together or insufficient collagen produced or both
What are the signs and symptoms of osteogenesis imperfecta?
- Weakened bones
- short stature
- blue sclera
- Hearing loss
- poor teeth development
