4.1 - Connective Tissue Flashcards
What are the 2 basic components of connective tissue?
- Cells
2. ECM
What are the 2 basic components of the ECM?
- Fibres (collagen, reticular, elastic)
2. Ground substance
Which type of tissue provides mechanical support to muscle, nerve, and epithelial tissue?
Connective tissue
Which type of tissue provides metabolic and physiological support to muscle, nerve, and epithelial tissue?
Connective tissue
What are the 2 types of connective tissue proper?
- Loose connective tissue
2. Dense connective tissue
What are the 2 types of embryonic connective tissue?
- Mesenchymal (location: mesoderm)
2. Mucus (location: umbilical cord)
Where would you find embryonic mucus connective tissue?
Umbilical cord
What is the function of fibroblasts?
Synthesize and maintain ECM
What are 2 substances synthesized by fibroblasts? (Hint: components of ECM.)
- Fibres (collagen, reticular, elastic)
2. Ground substance
What type of cells synthesize collagen fibres?
Fibroblasts
What type of cells synthesize reticular fibres?
Fibroblasts
What type of cells synthesize elastic fibres?
Fibroblasts
What type of cells synthesize ground substance?
Fibroblasts
What are fibrocytes?
Mature and less active fibroblasts
What are mesenchymal cells?
Stem cells originating from the mesenchyme
List 5 derivatives of mesenchymal cells
- Chondroblasts (cartilage)
- Lipoblasts (fat)
- Fibroblasts (supporting tissue)
- Osteoblasts (bone)
- Myoblasts (skeletal muscle)
What are macrophages?
Cells that ingest unwanted material
What white blood cell precursor do macrophages derive from?
Monocytes
What happens to monocytes in tissues?
Differentiate into macrophages or dendritic cells
Macrophages are antigen-presenting cells. What do antigen-presenting cells do?
Present antigens for recognition by T cells
What would you call macrophages of the liver?
Kuepfer cells
What would you call macrophages of the CNS?
Microglia
What would you call macrophages of the bone?
Osteoclasts
What are mast cells?
Granule-rich white blood cells that mediate allergy and immunity
3 components of mast cell granules.
- Heparin
- Histamine
- Cytokines
How does heparin in mast cells improve immune response?
Anti-coagulant; flow of white blood cells and antibodies to the area
How does histamine in mast cells improve immune response?
Increases vessel permeability; flow of white blood cells and antibodies to the area
How do cytokines in mast cells improve immune response?
Attract eosinophils and neutrophils
Describe the role of mast cells in type I hypersensitivity (i.e., allergic reaction).
B-cells produce IgE antbodies ->
Mast cells become coated with IgE ->
Upon exposure to the antigen, mast cells release inflammatory factors
What is anaphylaxis?
A severe allergic reaction that may cause death
What stain gives mast cells an intense purple color?
Giemsa
What is the primary function of the ECM?
Determine the morphology and function of the tissue
What is ground substance?
Gel-like matrix in which components of the ECM are embedded
List the 3 main components of ground substance.
- GAGs (glycosaminoglycans)
- Proteoglycans
- Glycoproteins
How do the components of ground substance (i.e., GAGs, proteoglycans, and glycoproteins) render it useful for resisting compressing and providing lubrication?
- Inflexible
2. Hydrophilic
Why would you inject hyaluronic acid (a GAG) into a joint to improve mobility?
Attaches to a proteoglycan to form hyaluronate proteoglycan aggregate, which resists compression and provides lubrication
What is the most common protein in the body?
Collagen
Which dye stains collagen bright red?
Picro-Sirius Red
What happens to irreversibly denatured collagens?
Form gelatin and glue
How many types of collagen have been identified to date?
28
Describe the molecular structure of a collagen molecule.
- 3 alpha chains
- Glycine every third residue
- Triple helix
Describe how fibrillar collagen is synthesized.
RER:
-Synthesis of α chains
-Vitamin C hydrolyses proline -and lysine residues
-Glycosylation of proline and lysine residues
-Assembly of triple helix to form procollagen
ECM:
-Non-helical terminal peptides cleaved
-Collagen molecules assemble into fibrils
What type of pattern would you see in a high-resolution image of a single collagen fibril?
Banding pattern
What is the most abundant type of collagen?
Type I (90%)
List 4 places where you would find type I collagen. (Hint: strongest.)
- Bone
- Tendons
- Ligaments
- Skin
What type of collagen would you find in bones, tendons, ligaments, and skin?
Type I
List 2 places where you would find type II collagen.
- Hyaline cartilage
- Elastic cartilage
Remember: carTWOlage
Describe the fibrillar structure of type I collagen.
Bundles of fibrils
What type of collagen would you find in hyaline and elastic cartilage?
Type II
Describe the fibrillar structure of type II collagen.
Fine mesh of fibrils
Where would you find type III collagen?
Reticular fibres
Remember: reTHREEcular fibres
Describe the fibrillar structure of type III collagen.
Branching fibrils
What type of collagen would you find in reticular fibres?
Type III
Where would you find type IV collagen?
Basal lamina
Remember: type FOUR is in the FLOOR
Describe the fibrillar structure of type IV collagen.
Sheet
Where would you find type VII collagen?
Anchoring basal lamina to reticular fibres
What type of collagen would you find anchoring basal lamina to reticular fibres?
Type VII
What are the 2 microfibrillar components of elastic fibres?
- Elastin
2. Fibrillin
Describe the structure of elastin.
Highly cross-linked; coiled in its relaxed form
What is the function of elastic fibres?
Allow tissues to stretch
What is the structure of reticular fibres?
Thin, branching fibrils of type III collagen
What is the function of reticular fibres?
Structural framework (visualize: skeleton)
What is the function of collagen in the ECM?
Structural support
What Is the structure of collagen in the ECM?
Bundles of varying thickness
How does systemic sclerosis affect connective tissue?
Excess accumulation of collagen leads to hardening and functional impairment
How does scurvy (i.e., vitamin C deficiency) affect connective tissue?
Defective collagen synthesis leads to hemorrhage and gum ulceration
What defect in collagen synthesis causes scurvy?
Vitamin C deficiency prevents hydroxylation of proline and lysine
How does Marfan syndrome affect connective tissue?
Defective chromosomes coding for fibrillin lead to undeveloped elastic fibres (visualize: stretched out sock)
What is the inheritance pattern for Marfan syndrome?
Autosomal dominant
List 4 symptoms of Marfan syndrome.
- Abnormally tall
- Abnormally long fingers and toes
- Frequent joint dislocation
- Risk of aortic rupture
What is arachnodactyly?
Abnormally long fingers and toes
Remember: “spider fingers”
How does Ehlers-Danlos syndrome affect connective tissue?
Defective collagen synthesis leads to tissue fragility (visualize: weak joints, stretchy skin, ruptured vessels)
How might type IV Ehlers-Danlos syndrome lead to aortic rupture?
Defective type III collagen synthesis weakens reticular fibres, which support the aorta
What are the 2 possible inheritance patterns for Ehlers-Danlos syndrome?
- Autosomal dominant
2. Autosomal recessive
How does Williams syndrome affect connective tissue?
Deletion from region of chromosome 7 includes ELN gene, which leads to learning and cardiovascular problems
Remember: drunk William is dumb and red
How does osteogenesis imperfecta affect connective tissue?
Defective type I collagen synthesis leads to spontaneous fractures
Which bone disease is characterised by blue-tinged sclera?
Osteogenesis imperfecta
Compare the structure of loose connective tissue and dense connective tissue.
Loose: more ground substance, loosely packed collagen and fibres
Dense: less ground substance, densely packed collagen and fibres
Compare the structure of regular connective tissue and irregular connective tissue.
Regular: parallel bundles of collagen
Irregular: criss-crossing bundles of collagen
What are the 3 layers of a blood vessel?
- Tunica intima (endothelium and connective tissue)
- Tunica media (elastic fibres and smooth muscle)
- Tunica adventitia (collagen)
Usually, fibroblasts produce ECM. However, what produces ECM in elastic arteries?
Smooth muscle
What are the 3 main functions of loose connective tissue?
- Metabolic support
- Immune support
- Physical support
What is the main function of dense connective tissue?
Physical support
Why is dense connective tissue slow to heal?
Poorly vascularized
Compare the function of tendons and ligaments.
Tendons: join muscle to bone or muscle to muscle
Ligaments: join bone to bone
What would you call a large, flattened tendon?
Aponeuroses
What is an aponeuroses?
Large, flattened tendon
List 6 purposes of connective tissue.
- ATTACH muscle to bone, muscle to muscle, and bone to bone (e.g., tendons and ligaments)
- STRUCTURE for tissues (e.g., collagen)
- CUSHION between tissues and organs (e.g., adipose tissue)
- MEDIUM of diffusion for nutrients and wastes (e.g, blood)
- DEFEND against infection (e.g., blood)
- REPAIR following injury (e.g., blood)
List 2 structures where you would find dense regular connective tissue.
- Tendons
2. Ligaments
Compare the histological appearance of tendons and ligaments.
Tendons: straight collagen bundles
Ligaments: wavy collagen bundles
List 4 structures where you would find dense irregular connective tissue.
- Dermis
- Glands
- Walls of tubular organs
- Tubular capsules
List 4 places where you would find loose connective tissue.
- Blood
- Adipose tissue
- Beneath epithelia
- Surrounding blood vessels, nerves, and lymph nodes
List 3 functions of adipose tissue.
- Fuel
- Thermogenesis
- Shock absorption
Compare the histological appearance of white adipose tissue and brown adipose tissue.
White: cells comprise of single large fat droplet, peripheral nuclei
Brown: cells comprise of many small fat droplets, central nuclei
List 2 traits that give brown fat its colour.
- Rich blood supply
2. Abundant mitochondria
Which tissue controls non-shivering thermogenesis (esp. in the upper chest and neck)?
Brown fat
Which 2 cell types secrete histamine?
- Basophils
2. Mast cells