Lecture 3: Connective Tissues Flashcards
(21 cards)
What are the three layers in embryology and to what do they give rise to?
Ectoderm: Skin, CNS
Mesoderm: Connective tissue + Epithelia
Endoderm: Viscera
What are the three main functions of connective tissues?
Volume: Ground substance (complex carbohydrates and glycoproteins
Tensile strength: Provided by collagen (and reticulin, type 3).
Elasticity: Provided by elastin
What 2 classes can we break up CT in to?
Embryonic CT and CT proper
What are the two types of CT proper?
Loose (areolar) tissue. Acts as a wrapping material.
Dense tissue, which comprises robust capsules such as the spleen, kidney, and others such as tendon, ligament.
There are also specialised CT, which include bone, cartilage, fat, blood etc.
True or false? Fibres are made of protein and are NOT present relative to the specific tissue.
False. They are made of protein, but they ARE relative to the tissue they represent.
Describe collagen, describe it’s appearance under a LM, and name its precursor and the molecule it forms.
Collagen is the most abundant protein in the human body, with 28 different types. It is wavy under the LM and mainly used for tensile strength. Fibroblasts initially produce tropocollagen monomers, which are precursors to collagen. They then bind to form triple helix molecules/collagen fibrils.
What are collagen 1,2,3,4,7? Lack of collagen results in?
1: CT proper
2: Cartilage, discs etc.
3: Reticulin/reticular fibres
4: Basement membranes
7: Anchoring fibrils linking to basement membranes.
Scurvy.
True or false? Reticulin is easily viewed under a light microscope?
False. Often requires special staining such as silver staining as it is too thin to be viewed under a LM.
What is the precursor to elastin and by what cells is it made of? In which tissues would we commonly find elastin?
Tropoelastin, fibroblasts.
Lungs, heart, aorta, blood vessels.
What is Marfan Syndrome?
An inherited disease of fibrillin-1. Fibrillin-1 helps to maintain the stability of elastin. Without it, elastin isn’t able to function properly, compliance is compromised. Structures such as the aorta etc. then do not function properly.
Describe ground substance. List the components.
Clear viscous fluid with a mix of glycoproteins and complex carbohydrates. Helps to indirectly move molecules and cells through tissue.
Components include: GAGs and glycoproteins.
What kinds of GAGs are there?
GAGs, or glycosaminoglycans, are long unbranched polysaccharide chains. They are negatively charged, which attracts sodium (Na+), which ultimately attracts water.
There are 6 kinds of GAGs, with hyaluronic acid being the most common, not linked to proteins. It is predominantly found in loose CT.
What are the different glycoproteins? Briefly describe their roles.
Fibrillin, laminin, fibronectin. They mainly help to deposit fibres (e.g. fibrillin is important for the deposition of elastin as it acts as a template).
They form the link between cells and matrix.
What is the extracellular matrix predominantly made of and what cells control it?
Ground substance and fibres. Fibroblasts control it makes sense as the fibroblasts pretty much produce everything to do with connective tissues (with the exception of some such as basement membranes).
List some functions of the EM. How is it remodelled?
Regulate metabolism and cell growth+differentiation. Binds and stores growth factors. It is important in wound healing and chronic fibrosing diseases.
It is remodelled by matrix metalloproteinases and phagocytosis.
What are the roles and differences of fibroblasts and myofibroblasts?
They secrete, maintain and recycle matrix in most tissues. They are wavy in nature and have elongated nuclei. Myofibroblasts are activated fibroblasts with a contractile function.
True or false? White adipose tissues have one big fat droplet whereas brown adipose tissues have multiple fat droplets per cell.
True.
Describe cartilage with regards to collagen.
Predominance of proteoglycan ground substance, made of collagen type 2. Connective tissue cells are chondrocytes and the main type is hyaline, and it is avascular.
Diffusion is the main way in which nutrients get across.
What collagen type is bone?
Type 1. CT cells are called osteoblasts/cytes.
True or false. Basement membranes are produced by fibroblasts.
False. It is made by the tissue it supports.
List the layers of a basement membrane.
Extracellular matrix (collagen type 4). Heparan sulphate Structural glycoproteins such as laminin and fibronectins that help to link integrins of epithelial cells to the extracellular matrix.
