What does the cell at the arrow secrete?

What does the cell at the arrow secrete?

• A. Histamine
• B. Collagen
• C. Antibody
• D. Heparin

Answer: (B)

Fibroblasts are the cells that make the extracellular matrix in connective tissue, and their main product is collagen. This protein forms the structural scaffolding that gives tissues tensile strength, so the cell shown is most likely releasing collagen into the surrounding matrix. The process starts in the rough endoplasmic reticulum, where collagen is assembled as procollagen triple helices, then is secreted out of the cell. Outside the cell, enzymes remove the propeptides to form tropocollagen, which then assembles into fibrils and becomes cross-linked to create strong collagen fibers that support tissues like skin, bone, and tendon. Other options don’t fit because histamine and heparin are stored and released by mast cells, not by fibroblasts; antibodies are produced by plasma cells derived from B cells; collagen is the classic product of fibroblasts in connective tissue.

Fibroblasts are the cells that make the extracellular matrix in connective tissue, and their main product is collagen. This protein forms the structural scaffolding that gives tissues tensile strength, so the cell shown is most likely releasing collagen into the surrounding matrix. The process starts in the rough endoplasmic reticulum, where collagen is assembled as procollagen triple helices, then is secreted out of the cell. Outside the cell, enzymes remove the propeptides to form tropocollagen, which then assembles into fibrils and becomes cross-linked to create strong collagen fibers that support tissues like skin, bone, and tendon.

Other options don’t fit because histamine and heparin are stored and released by mast cells, not by fibroblasts; antibodies are produced by plasma cells derived from B cells; collagen is the classic product of fibroblasts in connective tissue.