Connective Tissue Flashcards
What are the main functions of connective tissue?
- Join to underlying tissues and provide support
- Protect underlying organs
- Defend against infection
- Provide a medium for diffusion
What tissue is the most abundant and widespread in the body?
-Connective tissue
What three general features make up connective tissue?
- Cellular components
- Ground substance
- Fibres
What is ground substance?
- amorphous ECM consisting of linear aggregates of hyaluronic acid with many proteoglycan monomers (glycoaminoglycans attached to a core protein)
- Link proteins attach the proteoglycan monomers to the hyaluronic acid molecules
Why does ground substance form a hydrated gel?
-The high density of gags gives the ground substance a high negative charge which attracts water
What type of fibres can be found in connective tissue?
- Collagen
- Reticular
- Elastic
What protein is the most abundant in the body?
-Collagen (specifically Type 1)
What secretes collagen?
-Fibroblasts secrete procollagen which are then arranged into fibres
What is type 3 collagen and where is it found?
- Reticulin
- Lymphatic tissues
What do reticular fibres look like?
- Messy network of fibres
- Thin
- Branched
Where is type 4 collagen found?
-Basal lamina in basement membrane
What is type 2 collagen?
-Elastic and hyaline
Name the two types of embryonic connective tissue?
- Mesenchyme
- Mucous
Where is mucous connective tissue found? Describe its features
- Wharton’s jelly of the umbilical cord
- Gelatin-like ground substance
- Large intercellular spaces
- Spindle-shaped cells
Where is mesenchyme derived from?
-Mesoderm
Describe mesenchymal cells
- Pluripoent
- Tapered/spindle appearance due to cytoplasmic processes
What 5 things are derived from mesenchyme?
- Bone
- Fibroblasts->ligaments/tendons/supporting tissues
- Adipocytes
- Cartilage
- Skeletal muscle
What are the types of connective tissue proper?
- Loose
- Dense->regular/irregular
What are the specialised types of connective tissue?
- Bone
- Blood
- Cartilage
- Fibrocartilage
- Adipose tissue
- Lymphatics
- Haematopoetic tissue
Why does mesenchyme persist in the adult?
-To give rise to new connective tissue during healing
Where would you find elastic fibres?
- Dermis
- Artery walls
- Elastic cartilage
Describe the structure of elastic fibres, and it’s appearance under a TEM
- Primarily elastin surrounded by a microfibril protein called fibrillin
- Elastin is less electron dense than fibrillin ->lighter on the inside with surrounding darker area
Name the three layers of arterial walls and what do they consist of?
- Tunica intima -> epithelia
- Tunica media -> elastic lamella capable of being stretched, smooth muscle, collagen and ECM
- Tunica adventitia -> collagen
What is the inheritance pattern of marfans syndrome?
-Autosomal dominant
What is special about the smooth muscle of the aorta wall?
-Secretes elastic, collagen and matrix
What do elastic fibres look like?
- Thin
- Usually black
- Branched network (not as messy as reticular)
What causes marfans syndrome?
-Abnormal fibrillin gene leading to abnormal elastic tissue
What is the clinical picture of marfans syndrome?
- Abnormall tall
- Arachnodactyly
- Frequent joint dislocations
- Abormally stretchy skin
- Risk of aortic rupture
Describe the connective tissue of the mammory gland
- loose connective tissue with wispy collagen and many fibroblasts surrounds the glandular epithelium
- Dense irregular connective tissue lies further away from the glandular epithelium with thick and abundant collagen and few fibroblasts
What is the main function of loose connective tissue?
- Attach epithelium to underlying tissues
- Allow diffusion of nutrients to cells
Which layer of epithelial tissue is normally loose connective tissue?
-Submucosa (eg, in colon)
What type of fibres does loose connective tissue contain?
-Collagen and elastic
What is a specialised loose connective tissue?
-Blood
What type of connective tissue are organ capsules?
-Loose or dense irregular depending on anatomical location
What is the purpose of organ capsules?
-To provide protection
What are the main purposes of dense irregular connective tissue?
- Withstand tension
- Provide structural support
What type of connective tissue is the dermis?
-Dense irrgular
What is the general organisation of dense irregular connective tissue? How does its structure relate to its function?
- Collagen bundles which are densely packed but irregularly arranged
- The different orientations of the fibres allows the connective tissue to resist force in multiple directions and prevents tearing
What is the function of the elastic fibres in the dermis?
-Allows a degree of stretch and restoration
What are the colours of the dermis with silverstain?
- Collagen bundles - pink
- Elastic fibres - dark red
What is the main function of dense regular connective tissue?
-To have high tensile strength to resist high force in one direction
Where is dense regular connective tissue found?
- Tendon
- Ligaments
What is the structure of tendons and how does this relate to its function?
- Very dense collagen bundles tightly packed arranged in parallel lines to the direction of the exerting force
- Rows of elongated flattened fibroblasts between bundles
- Provides high tensile strength of the tendon which is needed to attach muscle to bone
What is the function of ligaments?
-Attach bone to bone
How does the structure of ligaments differ from tendons?
-Arranged in fascicles of dense connective tissue separated by loose connective tissue
What 4 cell types are found in connective tissue?
- Fibroblasts
- Macrophages
- Mast cell
- Adipocyte
What is the most common cell type in connective tissue?
-Fibroblasts
What are the function of fibroblasts?
- Provide and maintain ECM
- Synthesise and secrete collagen, elastin, proteoglycans and gags
Describe the appearance of a fibroblast?
- Slightly spindle nuclei
- Tapered cytoplasm
- Abundant rER
What other function are fibroblasts important in?
-Wound healing
In what connective tissue are macrophages found?
-Loose
What are the functions of the macrophages in connective tissue?
- Degrade foreign organisms
- Remove cell debris and dead cells
Where are mast cells found in connective tissue?
-Near blood vessels, absent from CNS
What are mast cells involved in?
- Hypersensitivity
- Anaphylaxis
What causes mast cells to release their granules?
- Become coated in IgE
- Bind allergen
- Release granules
What do the granules contain?
- Histamine
- Heparin
- Chemoattractants
What are the two types of adipocytes?
-Brown and white
Describe the features of a white adipocyte
- Numerous lipid droplets merge to form one large droplet
- Displaces all other cell contents to the side
Describe the features of a brown adipocyte
- Lipid droplets remain separate
- Central nucleus
- Abundant mitochondria (non-shivering thermogenesis)
Why do adipocytes look empty when stained with H and E?
-Preparation with toluene and xylene dissolves the lipid
Where is brown adipose tissue found?
-Scapula, sternum, axillae
