Anatomy Exam Histology of Connective Tissues 5 — Questions and Answers
Question 1: Which feature distinguishes a myofibroblast from a fibroblast histologically?
- Presence of lipid droplets
- Expression of alpha-smooth muscle actin (α-SMA) (Correct answer)
- Abundant rough ER and Golgi
- Large eccentric nucleus
Correct answer: Expression of alpha-smooth muscle actin (α-SMA)
Myofibroblasts express α-smooth muscle actin, assembling stress fibers that give them contractile properties absent in typical fibroblasts.
Question 2: Scurvy results from impaired collagen synthesis because vitamin C is required for:
- Glycosylation of procollagen
- Hydroxylation of proline and lysine residues (Correct answer)
- Signal peptide cleavage
- Formation of disulfide bonds in the C-propeptide
Correct answer: Hydroxylation of proline and lysine residues
Vitamin C (ascorbate) is an essential cofactor for prolyl and lysyl hydroxylases, enzymes that modify collagen precursors in the rER.
Question 3: Brown adipose tissue differs from white adipose tissue primarily in that it:
- Lacks a vascular supply
- Contains unilocular lipid droplets
- Has abundant mitochondria for thermogenesis (Correct answer)
- Is found only in adults
Correct answer: Has abundant mitochondria for thermogenesis
Brown adipose tissue contains numerous mitochondria with uncoupling protein-1 (UCP-1), enabling heat generation through non-shivering thermogenesis.
Question 4: Which connective tissue component is detected by Alcian blue staining?
- Collagen fibers
- Elastic fibers
- Glycosaminoglycans and proteoglycans (Correct answer)
- Reticular fibers
Correct answer: Glycosaminoglycans and proteoglycans
Alcian blue selectively stains acidic polysaccharides including glycosaminoglycans and proteoglycans in the extracellular matrix.
Question 5: Tendon is an example of which type of connective tissue?
- Loose areolar connective tissue
- Dense irregular connective tissue
- Dense regular connective tissue (Correct answer)
- Reticular connective tissue
Correct answer: Dense regular connective tissue
Tendons consist of dense regular connective tissue with parallel bundles of type I collagen aligned along the axis of tensile stress.
Question 6: During wound healing, granulation tissue is characterized by:
- Abundant elastic fibers and adipocytes
- New capillaries, fibroblasts, and macrophages in loose matrix (Correct answer)
- Dense type I collagen bundles
- Chondrocytes and proteoglycans
Correct answer: New capillaries, fibroblasts, and macrophages in loose matrix
Granulation tissue contains newly formed capillaries (angiogenesis), activated fibroblasts/myofibroblasts, and macrophages in a provisional loose ECM.
Question 7: The ground substance of connective tissue achieves its gel-like consistency primarily through:
- Covalent cross-links between collagen fibrils
- Water bound by negatively charged proteoglycan aggregates (Correct answer)
- Disulfide bonds in fibronectin
- Calcium phosphate crystal deposition
Correct answer: Water bound by negatively charged proteoglycan aggregates
Proteoglycan aggregates in the ECM bind enormous amounts of water via their negatively charged GAG chains, creating a hydrated gel.
Anatomy Exam Histology of Connective Tissues 5
Which feature distinguishes a myofibroblast from a fibroblast histologically?