Connective Tissue Histology (10/16c) [Biomedical]

Question 1

Functions of CT

Answer 1

Maintains/supports structure and communicates

Mediates exchange metabolic waste, nutrients, etc

Plays a role in immune response, inflammation and tissue repair

Question 2

Classifications of CT - Connective Tissue Proper

Answer 2

Loose (Areolar) CT

Dense CT

• Irregular
• Regular

Question 3

Classifications of CT - Specialized CT

Answer 3

Adipose — modified loose CT

Cartilage

Bone

Hematopoietic tissue (bone marrow)

Question 4

Components of CT

Answer 4

Extracellular Matrix

• ground substance
• fibers

Cells

• resident
• visiting

Question 5

Extracellular Matrix (ECM) Components

Answer 5

Ground Substance — largely proteoglycans, attract water to create a hydrated gel

Fibers — embedded throughout the ground substance

Question 6

ECM Function

Answer 6

Dictates:
- water in the CT

• types of fibers produced
• how much of the fibers are produced

Question 7

ECM - Ground Substance Components

Answer 7

Proteoglycan aggregates (proteins, GAGs, linked to hyaluronic acid)
- GAGs are long-chained polysaccharides with high negative charge that attract water

Structural Glycoproteins
- Fibronectin, fibrillin, etc are proteins that bind cells (fibroblasts) to fibers

Question 8

ECM - Fibrous Proteins

Answer 8

Collagen Fibers
- Types I-IV

Elastic Fibers
- Elastin and fibrillin

Question 9

ECM - Collagen Fiber Type I

Answer 9

Most common type

Bone, ligament, tendon, fascia, joint capsules, etc.

Bundled, cross-linked, highly organized structure makes it exceptionally strong and resilient to tensile forces

Several fibrils put together to form one collagen fiber, crosslinked by glycoproteins (fibronectin)

EX: looks like fettuccine

Question 10

ECM - Collagen Fiber Type II

Answer 10

Within hyaline and elastic cartilage

Not bundled, no highly regular appearance (more deformable)

Feathery looking

More cellular/more ground substance allows for recoil and bounce back of shape

Question 11

ECM - Collagen Fiber Type III

Answer 11

Reticular Fibers

Lymph tissue, bone marrow, blood vessels (BV’s), immature wound beds

Branched in a mesh-like appearance

Question 12

ECM - Collagen Fiber Type IV

Answer 12

Occurs in basal laminae (epithelial cell basement membrane)

Support of tissue layer and ability to filter

Question 13

ECM - Elastic Fibers

Answer 13

Made of elastin and fibrillin

Found in lungs, blood vessels, skin, ligaments
- Ligamentum nuchae and flavum in the spine, abundance of elastin)

Fibrillin is the protein that bind elastin fibers together

Can be relaxed or stretched, allows for elastic recoil

Wavy appearance, somewhat in parallel but not in bundles

Question 14

Resident Cells

Answer 14

Fibrocytes or fibroblasts (if active)
- Fibroblasts produce ground substance, fibers, and everything else in CT (“workhorse of the CT”)

Mesenchymal Cells (AKA stem cell or pericyte)
- immature or precursor fibroblast

Question 15

Visiting Cells

Answer 15

Produced in bone marrow and travel to the tissue

All involved in immune response within CT

Macrophage — phagocytic, antigen presenting and cytokines

Mast Cell — inflammatory mediator, produce/secrete vasoactive substances, heparin, histamines

Plasma Cells — B lymphocytes, antibody (immunoglobulin) production

Question 16

CT Proper — Loose CT (areolar)

Answer 16

Functions — vehicle by which blood vessels travel to transfer nutrients/waste with epidermal layer, packs the space between/around organs to absorb forces and provide protection

Characteristics — most abundant CT proper, sparse elastin and collagen fibers, increased cells and ground substance

Question 17

CT Proper — Dense Irregular CT

Answer 17

Functions – withstand tension from different directions but also somewhat flexible

Characteristics – densely packed with collagen (irregularly arranged), some elastic fibers as well

Found in the dermal layer, sheaths around tendons, bursa and nerves

Question 18

CT Proper — Dense Regular CT

Answer 18

Functions – to provide maximum tensile strength

Characteristics — collagen in dense parallel bundled arrangement

Found in the ligaments, musculotendinous units and aponeuroses

Question 19

Disorders of Elastin

Answer 19

Can be damaged by UV light (affects skin elasticity)

Loss of elastin in respiratory system causes emphysema

Question 20

Disorders of Collagen - Ehlers Danlos Syndrome

Answer 20

10 clinical/genetic variations

Autosomal dominant, recessive, x-linked recessive

Collagen defect– lacks tensile strength

Most common clinical symptoms – joint hypermobility, large joint dislocation, and skin hyperelasticity

Question 21

Disorders of Collagen - Osteogenesis Imperfecta

Answer 21

1/20,000 incidence — defect in Type I collagen

Autosomal dominant and spontaneous mutation

Wide range of clinical manifestations

Brittle bones is very common

Fracture incidence decreases after puberty