Connective Tissue Flashcards
Give some examples of the functions of connective tissue.
- provides substance and form to body/organs
- medium for diffusion of nutrients/waste products
- attaches muscle to bone (tendon) and bone to bone (ligaments)
- cushion between tissues/organs
- defence against infection
- aids injury repair
Define connective tissue.
Continuum throughout the body linking muscle, nerve, and epithelial tissue in a structural way whilst providing support in a metabolic and physiological way.
What are the components of connective tissue?
CELLS & EXTRACELLULAR MATRIX
Extracellular matrix = GROUND SUBSTANCE + FIBRES (collagen, reticular, or elastic)
What does ground substance do, and what is it composed of?
Provides route for communication/transport between cells (by diffusion).
GLYCOSAMINOGLYCAN + PROTEOGLYCAN MONOMERS
e.g. hyaluronate proteoglycan aggregate
Negative charges on GAGs attract water -> forms hydrated gel
What are some significant examples of highly modified ground substance?
PLASMA (blood): gs lacks stabilising macromolecules (free-flowing)
BONE: gs has been mineralised by calcium deposits (rigid)
CARTILAGE: gs more solid, but still resilient
What is the structure and function of collagen?
Triple alpha-helix (Gly-X-Y repeating sequence) with H-bonds between alpha chains, and cross-links between molecules to form fibrils, and between fibrils to form fibres.
Confers tensile strength to connective tissue
What is a fibrous capsule?
Fibrous connective tissue surrounding an organ/tissue acting as a barrier
e.g. capsule around lymph node prevents lymph diffusing out into the surrounding tissues, and also prevents lymph infections
What is the function of reticular fibres?
Reticular fibres (reticulin) = type of collagen that cross-links to form a delicate supporting framework for loose cells in soft tissues.
What is the function of elastic fibres?
Elastic fibres (elastin enfolding fibrillin molecules) = restores normal shape after distortion
What are the types of connective tissue and how do they differ?
LOOSE = few fibres, lots of ECF
DENSE IRREGULAR = lots of fibres orientated in multiple directions (resists forces in different directions, therefore prevents tearing)
DENSE REGULAR = lots of fibres running parallel (in line with tensile force exerted by muscle)
Give some examples of loose connective tissue.
Lamina propria (mucosa) Submucosa (COLON) Mesentery (serosa) Blood vessels Nerves
Give some examples of dense irregular connective tissue.
Dermis
Submucosa (?)
PERIOSTEUM = membrane covering bone surface
PERICHONDRIUM = membrane surrounding cartilage
Give some examples of dense regular connective tissue.
Tendons = join muscle to bone
Ligaments = join bone to bone
What is the function and location of fibroblasts?
Secretes fibres e.g. procollagen, reticulin, elastin, and ground substance.
Important for healing and scar formation.
Most common cell found in connective tissue.
What is a trabecula?
Column of connective tissue extending from capsule into tissue.
Divides glands into lobules
Explain how different types of connective tissue are of embryonic origin.
EMBRYONIC CONNECTIVE TISSUE = mucous connective tissue (umbilical cord) + MESENCHYME (multipotent cells of mesodermal origin).
The mesenchyme can differentiate to form cells involved in synthesising connective tissue (fundamentally fibroblasts, but also chondroblasts -> cartilage, osteoblasts -> bone, and lipoblasts -> adipose)
What is the function of macrophages?
Blood monocytes -> macrophages —> connective tissue (esp. during inflammation).
Phagocytic (degrades cell debris/foreign bodies by forming a phagolysosome)
Present foreign material to T lymphocytes e.g. bacteria (immune response activated).
What is the function of mast cells?
Abundant in cytoplasm as granules. Present in connective tissues near blood vessels (but ABSENT from CNS -> prevent oedema in brain).
Secrete heparin (anticoagulant), histamine (increase blood vessel wall permeability), and chemoattractants for eosinophils and neutrophils.
Allergen binding to IgE receptors on surface -> releases contents -> hypersensitivity -> allergy/anaphylaxis
Give some examples of specialised connective tissue.
- ADIPOSE TISSUE
- BLOOD = plasma + haemopoietic tissue (blood cellular components)
- CARTILAGE
- BONE
- LYMPHATIC TISSUE
Explain the differences in structure and function between types of adipose tissue.
ADIPOCYTES -> LIPOBLASTS -> lipid droplets in cytoplasm of fat cells.
Lipid droplets remain separate = brown adipose tissue (multilocular)
Lipid droplets combine = white adipose tissue (unilocular)
Both are fuel reserves, and act as insulators/shock absorbers.
Brown adipose is also involved in non-shivering thermogenesis (uncoupling of oxidative phosphorylation to release heat energy).
What are the clinical features of Marfan’s syndrome?
Autosomal dominant
Mutant fibrillin gene -> deformed elastin fibres
Arachnodactyly (long fingers), tall, wing span>height, high arched palate.
Mitral valve disorders.
Risk of aortic dissection.
What are the clinical features of Ehlers-Danlos syndrome?
Autosomal dominant Defect in collagen (type can determine severity) -> abnormal cross-linking between fibrils Hypermobile joints (frequent dislocations), fragile blood vessels, hyperelastic skin, heart valve problems.
