Question

12. Describe the inflammatory and repair processes by which tissues recover from injury. 13. Briefly describe the changes that occur in tissues with age.

Answer 1

12. Tissue repair is the mechanism by which the skin heals itself after injury.

There are four stages of tissue repair: Homeostasis, inflammatory, Proliferative, and Remodeling.

Homeostasis: The first phase of tissue repair, when wounded, is concerned with maintaining homeostasis within the body. Most wounds, even shallow superficial wounds, cause damage to the circulatory system. To avoid blood loss and minimize the risk of spreading infection across the body, circulation platelets within the blood continue to form a fibrin clot that seals the wound site.

Inflammatory: Immune cells, like neutrophils and macrophages, are attracted and start to accumulate by factors released from the wound site, passing through the circulatory system. Such cells are responsible for removing debris and destroying bacteria that colonize the wound site easily and preparing the wound for the process of proliferation/remodeling.

Proliferative: The proliferative stage of wound healing is when the wound is replaced with new tissue composed of collagen and extracellular matrix. The wound contracts as new tissue is formed in the proliferative process.

Remodeling Phase: Remodeling can take place after the wound has been closed. The epidermis proliferates and returns to its natural character, the fibroblasts and immune cells that have been recruited at the site are degraded, and the temporary extracellular matrix that has been formed is reshaped into a stronger, more permanent structure.

13. Cells are the fundamental tissue building blocks. Upon aging, all cells undergo changes. They get larger and are less able to divide and multiply. There is also an increase in pigments and fatty substances inside the cell (lipids). Most cells are losing their ability to function or start behaving abnormally.

When aging progresses, the tissue builds up with waste materials. Much like other fatty compounds, a fatty brown pigment called lipofuscin forms in many tissues.

Changes in connective tissue, they become stiff and makes the organs, blood vessels, and airways more rigid. Cell membranes change, so many tissues find it more difficult to receive oxygen and nutrients and remove carbon dioxide and other waste.

Most of the tissues lose mass, which is called atrophy. Some tissues get lumpy (nodular) or stiffer.