Session 6 part 1

Question 1

What are the main cells in connective tissues? What are the main products?

Answer 1

cells:
fibroblasts
chondrocytes
osteoclasts/ blasts/ cytes
stem cells
adipocytes

products:
fibres
ground substance
wax and gel like materials

Question 2

Describe the structure of connective tissue

Answer 2

cells: mainly mature fibroblasts
fibres: collagen, elastin, reticular fibres
ground substance: proteoglycans

ground substance + fibres = extracellular matrix

Question 3

What are the functions of connective tissue?

Answer 3

binding and supporting
protective
insulating
storing fuel reserve and cells
transporting substances
separation of tissues

Question 4

Describe the structure of loose connective tissue

Answer 4

cells: 
fibroblasts, macrophages, other WBCs, mast cells and adipocytes
fibres:
collagen and elastin
ground substance:
proteoglycans and hyaluronic acid

Question 5

What are the functions of loose connective tissue?

Answer 5

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

Question 6

What are fibroblasts? What are myofibroblasts?

Answer 6

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

Question 7

What are macrophages?

Answer 7

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

Question 8

What are mast cells?

Answer 8

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

Question 9

What are adipocytes (both types)?

Answer 9

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

Question 10

Compare white and brown adipose tissue

Answer 10

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

Question 11

What are the fibres in connective tissue? Describe them

Answer 11

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

Question 12

What are the types of collagen?

Answer 12

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

Question 13

Summarise loose connective tissue, including examples of where it is located

Answer 13

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

Question 14

What is ground substance?

Answer 14

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

Question 15

Describe the structure of proteoglycans

Answer 15

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

Question 16

Describe dense irregular connective tissue, including examples of where it is located

Answer 16

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

Question 17

What is the myotendinous junction?

Answer 17

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

Question 18

Describe tendons

Answer 18

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

Question 19

What are ligaments?

Answer 19

similar to tendons
connect bone to bone
dense regular connective tissue
surrounded by loose connective tissue in fascicles

Question 20

What is fascia?

Answer 20

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

Question 21

What are aponeuroses?

Answer 21

early white fibrous tissue
connects:
muscle to muscle 
tendon to tendon
tendon to ligament

examples:
abdomen, external oblique
hand, palmar

Question 22

How does vitamin C produce collagen?

Answer 22

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

Question 23

Describe scurvy

Answer 23

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

Question 24

Describe Marfan’s Syndrome

Answer 24

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

Question 25

What are elastic fibres?

Answer 25

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

Question 26

Describe osteogenesis imperfecta

Answer 26

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