Session 6 part 1 Flashcards
What are the main cells in connective tissues? What are the main products?
cells: fibroblasts chondrocytes osteoclasts/ blasts/ cytes stem cells adipocytes
products:
fibres
ground substance
wax and gel like materials
Describe the structure of connective tissue
cells: mainly mature fibroblasts
fibres: collagen, elastin, reticular fibres
ground substance: proteoglycans
ground substance + fibres = extracellular matrix
What are the functions of connective tissue?
binding and supporting protective insulating storing fuel reserve and cells transporting substances separation of tissues
Describe the structure of loose connective tissue
cells: fibroblasts, macrophages, other WBCs, mast cells and adipocytes fibres: collagen and elastin ground substance: proteoglycans and hyaluronic acid
What are the functions of loose connective tissue?
holds vessels that supply fluids permits cell migration involved in inflammation pathways cushions and stabilises organs acts as packaging around organs holds everything in place
widely distributed under epithelial cell layers and around glands
surrounds capillaries, nerves and sinusoids
What are fibroblasts? What are myofibroblasts?
synthesise and secrete fibres that lie within ground substance
main function is the formation of scar tissue
myofibroblasts contain actin and myosin
responsible for wound contraction when tissue loss has occurred
What are macrophages?
derived from blood monocytes
move to connective tissue if there is local inflammation
they are phagocytic and can degrade foreign material
present forge in material to T and B lymphocytes
What are mast cells?
look like basophils but not derived from them
their cytoplasm contains abundant granules:
- Histamine, increases blood vessel wall permeability
- Heparin, anticoagulant stops blood clotting
- Cytokines, attract eosiniphils and neutrophils
cells are coated with immunoglobulin type E (IgE) which specifically bind to allergens
when bound the granules are all released from the cell
What are adipocytes (both types)?
unilocular
white adipocytes
single lipid droplet
nucleus, organelles, cytoplasm pushed to one side of cell
padding and shock absorber, insulation, energy reserve
multilocular brown adipocytes multiple lipid droplets nucleus, organelles, cytoplasm pushed to centre of cell insulation and energy reserve
Compare white and brown adipose tissue
white:
normal number of mitochondria
in adults, lipid breakdown slow and heat only generated after shivering reflex
brown:
increased number of mitochondria
in neonates and infants, lipid breakdown is accelerated, oxidative phosphorylation is uncoupled to generate heat
calories generated can double
What are the fibres in connective tissue? Describe them
collagen- flexible with high tensile strength
reticulin- in lymphatics, provide a supporting framework
elastin- made of hydrophobic amino acids, allow tissues to recoil after stretch
fibrillin- glycoprotein essential for construction of elastin fibres
What are the types of collagen?
collagen is the most common protein
type 1- fibrils aggregate into fibres and fibre bundles (skin dermis)
type 2- fibrils do not form fibres (hyaline cartilage)
type 3- fibrils form fibres around muscle, nerve cells, within lymphatic organs and tissues, and in tendons (reticulin)
type 4- unique form present in basement membrane
Summarise loose connective tissue, including examples of where it is located
located:
beneath epithelial cells to facilitate diffusion
epithelium of glands
around small blood vessel
these are all sites where pathogens can be destroyed by the immune system
when doing this, the connective tissue layer can swell considerably as it has the ability to expand and contract
What is ground substance?
viscous, clear substance
consists of proteoglycans and glycosaminoglycans
proteoglycans are large macromolecules that have a core protein that GAGs covalently bind to
GAGs attract water to form a hydrated gel; allows for rapid diffusion and resisting of compressions
a unique GAG is hyaluronic acid; binds to proteoglycans by a link protein to form giant hydrophilic macromolecules
Describe the structure of proteoglycans
GAGs attached to core proteins which then attach to hyaluronate
the sugar groups attract water, but makes the ground substance sticky and slippery at the same time
Describe dense irregular connective tissue, including examples of where it is located
fibres not arranged in parallel bundles
strengthen and support areas under stresses from many directions
eg dermis of the skin
contains elastic fibres to allow that degree of stretch
What is the myotendinous junction?
the junction where skeletal muscle fibres and tendon collagen bundles meet
provide tremendous physiological strength
the collagen bundles passes from the tendon to the muscle fibres where it interacts with the collagen fibres coating the muscle fibres
cross links form and create the mechanical strength
Describe tendons
stronger than muscles and as strong as bone
mainly made of water, 68%
70% type 1 collagen and 30% type 3 collagen (reticular fibres)
forces are transmissible along the collagen bundles as they can glide over each other
What are ligaments?
similar to tendons
connect bone to bone
dense regular connective tissue
surrounded by loose connective tissue in fascicles
What is fascia?
has three layers:
superficial, deep and visceral
made up of fibrous connective tissue, with collagen bundles arranged parallel to the direction of pull
flexible and can resist unidirectional forces
fibroblasts within the connective tissue make the collagen
What are aponeuroses?
early white fibrous tissue connects: muscle to muscle tendon to tendon tendon to ligament
examples:
abdomen, external oblique
hand, palmar
How does vitamin C produce collagen?
vitamin c is required for the intracellular production of procollagen, which hydroxylates lysine and proline
this helps procollagen to be packaged, released and modified outside of the cell into collagen
fibroblasts secrete procollagen that is converted to collagen outside of the cell, the collagen molecules aggregate into collagen fibrils
Describe scurvy
caused by major disruption to the hydroxylation of preprocollagen
the collagen fibrils can’t always form as there is insufficient collagen produced so the triple helical structure of collagen is not produced
causes: gum disease bleeding bruising of skin poor wound healing
Describe Marfan’s Syndrome
autosomal dominant disorder
affects the fibrillin 1 gene
abnormal elastic fibres
people affected have abnormally long limbs, arachnodactylyl, frequent joint dislocations and are at high risk for aortic rupture- 90% mortality rate
What are elastic fibres?
primarily made up of elastin, itself enfolds and is surrounded by microfibrils called fibrillin
occurs in most connective tissues but to massively varying degrees
present in; sites of elastic cartilage, artery walls, dermis and lungs
Describe osteogenesis imperfecta
brittle bone disease
most types are autosomal dominant
mild to severe
due to mutated collagen, fibres do not knit together or are insufficiently produced, or both
hearing loss short stature blue sclera arched feet, hypermobility frequent fractures poor teeth development
