9 - Connective and Adipose Tissue Flashcards
What are the main cells and products of connective tissue?
Cells - Osteocytes, osteoblasts, osteoclasts, Fibroblasts, Mesenchymal stem cells, chondrocytes, bone marrow, adipocytes, macrophages, mast cells
Products - Fibres, Ground substance, Wax and Gel like materials
What is the structure and function of connective tissue?
Structure:
- Cells, Extracellular matrix (Fibres and Ground stubstance)
Functions:
- Binding and supporting
- Insulation
- Shock absorption/Protection
- Store of fuel and cells (e.g bone marrow, adipose)
- Transport of substances (blood)
- Separation of tissues
What are the six type of connective tissues?
CT Proper: Loose Areolar, Fibrous (Dense Ir/regular)
Specialised: Bone, Cartilage, Bone Marrow, Blood, Adipose,
When looking at histological slides, what should you look for?
- White space: adipose, chondrocyte, artefact?
- Surface specialisations
- Type of epithelia, simple?compound?
- Type of muscle fibre
- Type of connective tissue
What types of connective tissue are loose?
- Reticular
- Blood
- Adipose
- Areolar
What is the general structure of loose areolar connective tissue?
- Few cells: Macrophages, Mast Cells, Fibroblasts, Other WBC’s
- Fibres: Lots of collagen, elastin and no reticular like other loose CT
- Large Gel Xcellular matrix: Glycosaminoglycans produced by fibroblasts
Where is loose areolar tissue found and what is it’s function?
- Where?
Under epithelia (hypodermis, submucosa, lamina propria)
Associated with epithelia of glands
Located around small blood vessels and nerves
Makes septa and trabeculae of organs
- Function?
Cushion and stabilise organs
Hold vessels that supply fluids
Inflammation response and kill pathogens that have breach epithelia
Permit cell migration
Separate organs (superficial fascia)
When is loose connective tissue first seen from embryo?
- Mesenchyme (mesodermal), made of MSC with fluid ground substance merged as ill-defined cell membranes
- Over time ground substance more mucoid so mucous connective tissue
Where is muscous connective tissue found?
- In the umbilical cord as Wharton’s jelly
- High amount of hyularonic acid contained within fine mesh of collagen I and III
- Large number of stellate fibroblasts and macrophages/lymphocytes
What is reticular connective tissue?
- Loose connective tissue with high amount of collagen III supported by collagen IV
- Fibroblasts secrete the collagen and they lay next to the fibroblasts
- Found in spleen, kidney and lymph nodes, producing a stroma for structural support
What happens when you have an alpha-anti trypsin 1 deficiency?
Elastin fibres in the lungs are destroyed by elastase enzymes secreted by neutrophils. Elastin cannot be remade.
What is the function of fibroblasts in connective tissue?
- Produce and secrete fibres that lay in ground substance
- Form scar tissue
- Myofibroblasts (contain actin and myosin) help wound contraction when tissue loss occured
What is a histiocyte?
Stationary macrophage in connective tissue
What is a macrophage’s function in connective tissue?
- Derived from blood monocytes and enter tissue when there is inflammation
- Phagocytic so destroy foreign bodies and act as antigen-presenting cells
What is the function of mast cells in connective tissue and what do they look like histologically?
- Close to collagen and blood vessels, look like basophils with lots of granules but not derived from them
- Not in CNS to prevent oedema
- Release histamine, cytokines, heparin and get coated in IgE
What are unilocular adipocytes?
- White adipose tissue, can be yellow
- Main adipocyte in loose CT
- Single lipid droplet with nucleus, organelles and cytoplasm pushed to periphery
- Provide padding, insulation, shock absorber and fuel reserve
What are multilocular adipocytes?
- In neonates around organs, only across shoulders and nape of neck in adults
- Multiple lipid droplets with nucleus pushed to centre
- Provide insulation and energy reserve
How are adipose cells generated?
From mesenchymal stem cells or fibroblasts
Compare and contrast white and brown fat.
Discuss the 4 main collagens
Discuss what property the three main fibres give to connective tissue
Collagen - Flexible with high tensile strength
Elastin - Allows tissues to stretch and recoil
Reticulin - Provide supportive framework (not in areolar)
Define connective tissue.
Tissue that connects, supports, binds or separates other tissues or organs
What is ground substance made up of?
- Clear slippery watery substance
- Proteoglycans, water, lipid
- Can become gelatin
What is the main structure, function and locations of dense connective tissue?
- Structure: Fewer cell types than loose, less ground substance, fibres closely packed
- Function: Mechanical support and transmit forces
- Location Irregular: Deep fascia, Periosteum, Dermis, Perichondrium, Capsules
- Location Regular: Tendons, Ligaments, Aponeuroses
What is the structure and histology of irregular dense connective tissue?
- Lots of fibres which cross-cross each other in multiple directions to resist forces in multiple directions and prevent tearing, mainly collagenous.
- Elastin allows degree of stretch or bend with skin
- Fibroblasts, Collagen I bundles
What is the structure and histology of dense regular connective tissue?
- Collagen bundles packes densley and parallel to provide maximum tensile strength against opposing forces
- Ligaments have more elastin than tendons
- Elongated flattened fibroblasts lay next to collagen
What is the structure of the myotendinous junction?
Cross links between collagen on tendon and collagen surrounding muscle fibres, results in very high mechanical strength
What is the structure of a tendon?
- Dense regular CT
- 30% collagen, 68% water, 2% elastin
- Stronger than muscle and as strong as bone
- 70% collagen I, 30% collagen III
What is the histology of a ligament?
- Dense regular CT
- Connect bone to bone
- Parallel collagen fibres, in fasicles of 3, surrounded by loose CT
What is fascia?
- Superficial, Deep, Visceral or Parietal depending on where it is found
- Way of separating muscle groups and organs
- Allow flexibility and resistance of unidirectional forces until fibres straightened out
What produces collagen in every connective tissue?
Fibroblasts, they secrete it as tropocollagen
What type of connective tissue is fascia?
Superficial - Loose areolar typically
Deep - Dense Regular typically, less stretch than superficial
What is scurvy caused by?
- Vitamin C deficiency (need about 75mg daily)
- Vit C needed to hydroxylate proline and lysine
- Without this cross links between alpha chains in collagen can’t form so weak connective tissue
What is Marfan’s caused by?
- Autosomal dominant
- Fibrillin 1 gene defective so abnormal elastic tissue as elastin and fibrillin needed together to form elastic
What does elastin and collagen fibres look like under an electron microscope?
What is the histological structure of the aorta?
What causes elastin to be lost and what is the issue with this?
- Smooth muscle cells produce elastin, once produce can’t be reformed
- Elastin destroyed by sunlight
- Elastin destroyed by smoking as neutrophils come to site and produce elastase
What is osteogenesis imperfecta caused by?
- Autosomal dominant
- Mutated collagen I fibres so either collagen doesn’t knit together or not enough produced or both
- Bones can break easily without falls, could be burping baby or changing diaper
