Connective tissue Flashcards
Where do connective tissue cells come from?
The mesoderm
Mesenchymal stem cells
What is the extracellular matrix composed of?
Ground substance
Structural glycoproteins
Fibres
What are the 5 types of connective tissue?
- Fibrocollagenous tissues
- Adipose tissue
- Cartilage
- Bone
- Blood
What is the ground substance composed of?
Glycosaminoglycans (GAGs) – long unbranched polysaccaride chains
- Proteoglycans – all GAGs except hyaluronic acid (hyuranan) link covalently to a protein core
- - proteoglycans can bind via a linker to hyaluronic acid to form even larger complexes (i.e. in cartilage)
What are the main properties of Glycosaminoglycans (GAGs) and Proteoglycans:
Negatively charged, open conformations; retain water and positive ions (mostly Na+)
forms a hydrated gel which allows selective passage of molecules (e.g. nutrient diffusion)
Describe the function of Structural glycoproteins, give examples
Functional molecules:
Many roles- linking, organising, catalysing processes
laminin, entactin, fibronectin (cell adhesion, part of basement membranes), fibrillin (elastic fibre formation); osteocalcin (bone mineralisation)
Name the two types of fibers found in connective tissue. What are they used for?
Collagen
Elastic fibers
used for mechanical properties
What is the precursor for collagen? Name the 4 different types and there properties
Precursor tropocollagen
Type I : thick bundles; very strong
Type II: thin, interwoven fibres- only in cartilage
Type III: delicate branching reticulin
Type IV: forms meshwork- basement membrane
What is the precursor for elastic fibers? Describe there formation?
Precursor- Tropoelastin
Elastin + fibrillin = Fibrils
Fibrils form sheets
Describe the cell(s), role and different types of Fibrocollagenous tissues
Cell: Fibroblast
Roles: Structural, supportive
Types:
A) Loose B) Dense (amount)
C) Reticular (type of loose, coll. III)
Describe the morphology of the ECM forLoose (areolar) connective tissue , what is it made up of? What cells will you find there? What is there role? Give an example
ECM- relatively few fibres; abundant viscous ground substance (hyaluronic acid)
Type- Type I collagen with reticular and elastic fibers
Cells- Fibroblasts; also stem cells, adipocytes, defense and immune cells (lymphocytes, resident macrophages, mast cells)
Role:
Physical, metabolic and defensive support
Example:
Lamina propria
Describe the morphology of the ECM for Dense connective tissue , what is it made up of? What cells will you find there? What is there role? Give an example
ECM- many fibres, little ground substance
Organisation-
random- dense irregular c.t.
structured- dense regular c.t.
Type- Type I collagen mainly +/- elastic fibers, reticulin
Cells:
Fibroblasts primarily
Role:
Mechanical support, tensile strength
Examples:
irregular- dermis,capsules
regular- tendon, ligament
Describe the morphology of the ECM for Reticular connective tissue , what is it made up of? What cells will you find there? What is there role? Give an example
ECM- few fibres, little ground substance
Organisation- fine network
Type- Type III collagen
Cells:
Mainly fibroblasts
Role:
Structural support for epithelia in some highly cellular tissues
Examples:
Lymph nodes, spleen, liver and other glands
What type of connective tissue does adipocytes contain? Name the two types
Contains supporting loose connective tissue (with fibroblasts)
white brown
What is the difference between white and brown adipocytes?
White Unilocular- one space for lipid Adult Widespread Energy store, shock absorber, insulator
Brown Multilocular- many spaces Newborn Restricted Heat source
Name the 3 types of cartilage and what they are made of?
Hyaline- type 2 collagen , Elastic- type 2 collagen and elastic fibers & Fibrocartilage- type 2 collagen and type 1
Describe the ground substance of cartilage
proteoglycans (aggrecan) containing chondroitin sulphate and keratan sulphate linked to hyaluronic acid– forming large complexes
and interacting with Type II collagen fibres
Name 2 cells you will find in cartilage and state there functions
Chondroblasts (form cartilage)
Chondrocytes (maintain cartilage)
Describe the ECM of bone? What is it called? What will you find there?
Ground substance called osteoid
Collagen type I fibres- layers (lamellae) in mature bone
Mineralised
List the cell types found in bone and state there function
Osteocytes- maintain bone
Osteoblasts- secrete osteoid, form bone
Osteoclasts- resorb bone
Describe the ECM in blood
Plasma fluid
Fibres: Fibrin of clots- made by liver as soluble fibrinogen
Which cells will you find in blood?
Circulating blood cells formed in bone marrow
What secretes fiber precursores
connective tissue cells
What is a hematoma?
A collection of blood, usually clotted, outside of a blood vessel that may occur because of an injury to the wall of a blood vessel
What is Ehlers-Danlos syndrome?
A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues.
How many types of Ehlers-Danlos syndrome is there?
(2017 classification) 13
Name features found in most Ehlers-Danlos syndrome types?
Hyperbomility, frequenct joint dislocations, soft velvety skin, very stretchy and elastic skim
Name the 2 different ways Ehlers-Danlos syndrome can be inherited?
Mainly Autosomal dominant can be recessive
What is the normal role of collagen type 5 in connective tissue?
It regulates the diameter of collagen type I fibrils
What type of joint is the shoulder joint?
Synovial ball and socket
What is the role of the Children and Family Court Advisory and Support Service in cases of suspected child abuse?
- To ensure that decisions are made in the child’s best interest.
- They get involved in the case and become known as the childs guardian
- The guardian is the independent voice of the child in court
Which is the tissue type of the epdermis? What is the major cell type?
Tissue type- stratifued squamous epithelial
Cell type- keratinocyte
Which is the tissue type of the dermis? What is the major cell type?
Tissue type- dense irregular connective tissue
Cell type- Fibroblast
How is classic EDS diagnosed?
3 symptoms from major criteria - Skin hyperextensibility -Widened atrophic scarring -Joint hypermobility -positive family history 1 from minor criteria -smooth velverty skin -easy bruising -Muscle hypotonia -complications of joint hypermobility and skin (dislocations) and tissue extensibility (hiatal hernia)
How many people with EDS are diagnosed?
5% (incidence may be higher than we assume)
Name other symptoms nor related to connective tissue that might suggest EDS
IBS, chronic pain, Fibromyalgia
Which mutation is responsible for EDS
A nonsense mutation in COL5A1 gene (substitution of glutamine causing a premature stop codon). (result- truncated protein)
How does a mutation in the COL5A1 gene lead to EDS?
A component of type V collagen called the pro-α1(V) chain is produced from the COL5A1 gene. Collagen is rope like made from 3 chains. 2 combinations of chains can be produced, three pro-α1(V) chains or two pro-α1(V) chains and one pro-α2(V) chain. The mutation reduces the amount of pro-α1(V) chains that cells produce. Fibrils containing type V and tyoe 1 callagen are disorganised and larger than usual. This weakens the connective tissue causing EDS.
Which laboratory tests are used to diagnose EDS?
A skin fibroblast biopsy can be taken and analysed in 2 ways
1- Assess the Electrophoretic pattern of the (pro)collagen type I, III and V (normal in PBL)
2. SDS-PAGE of collagen from dermal fibroblasts.Crude detection of protein
Different proteins have different weights and thus they can be separated on the gel by weight
(does not tell you if mutated or functional)
What leads to abnormal wound healing in EDS?
Collagen type 1 is looser with few bundles
Describe the wound healing stages.
- Haemostasis
Vascular constriction and clotting. - Inflammation
Release of cytokines and growth factors
WBC – remove dead cells and provide defence against microbes - Proliferation
Fibroblasts and kerantinocytes proliferate and start to make new ECM - Remodelling -scar formation
Which stage if wound healing is affected in EDS?
Stage 4 - remodelling
Due to mutation collagen synthesis is affected
collagen 3 is chnaged to 1
water is reabsorbed and fibers lie closer together
wound contracts so fibers do not gape
