Untitled Quiz

Study Notes

Labile cells: Continuously proliferate throughout life to replace aging cells, like the stratified squamous epithelium of the skin, respiratory epithelium, GIT epithelium, and haemopoietic & lymphoid tissue
Stable cells: Do not proliferate under normal conditions, but proliferate when needed. Examples include:
- Parenchymatous stable cells: Liver, pancreas, and endocrine glands
- Mesenchymal stable cells: Fibroblasts, chondroblasts, and osteoblasts
Permanent cells: Cannot proliferate at all, like:
- Muscle cells: Damaged cells are replaced by fibrous tissue deposited by fibroblasts (fibrosis)
- Nerve cells: Damaged cells are replaced by glial cells deposited by astrocytes (gliosis)

Repair by regeneration: Replacement of damaged cells by new healthy cells of the same type due to multiplication of the surviving cells.
- This is often seen in the repair of GIT mucosa, liver, bones, and epidermis
- Occurs in tissues composed of labile or stable cells
Repair by fibrosis (organization): Repair of damaged tissue occurs through granulation tissue, composed of fibroblasts, collagen, and new capillaries.
- Granulation tissue is later replaced by fibrous tissue, forming a scar. This mechanism occurs in tissues with permanent cells like those of the CNS, cardiac, and skeletal muscles.

Severity and extent of tissue damage: A cut wound with minimal damage heals quickly, while lacerated wounds with significant loss take longer.
Types of damaged cells: Labile cells regenerate faster than stable cells.
Arterial blood supply: Sufficient blood supply is crucial for nutrient and oxygen delivery to the area, aiding cell division.
Presence or absence of bacterial infection: Clear surgical incisions heal rapidly, while infected wounds and inflammatory lesions have delayed repair.
Presence of foreign body: Foreign bodies may delay repair.

Age: Infants and children have faster repair rates than adults.
Vitamin deficiency:
- Vitamin C is essential for connective tissue ground substance and osteoid synthesis.
- Vitamin A is crucial for healthy epithelium.
- Vitamin D is essential for bone formation.
Protein deficiency: Specifically, amino acid deficiency can impair repair.
Hormones: Glucocorticoids delay healing, while growth hormone is necessary for repair.
Immobilization: Essential for healing bone fractures.

Chronic ulcer: Persistent loss of surface epithelium continuity.
Sinus: A blind-ended tract between the wound cavity and the skin surface.
Fistula: A tract between an abscess cavity and a hollow organ, or between two hollow organs.
Keloid: Large scar projecting above the surface, caused by excessive repair.
Contracture: Scar on a flexure that limits movement.
Infection: Delays healing.
Weak scar: Can lead to surgical hernias.
Dehiscence: Opening of a healing wound.
Implantation (epidermoid) cyst:
Malignant transformation: Squamous cell carcinoma.

1-Which of the following is an example of permanent cells?
- Nerve cells (C)
2-Stable cells are:
- Cells that multiply only when stimulated (B)
3-Labile cells are:
- Cells that regenerate continuously during adult life (C)
4-Cells which never regenerate are called:
- Permanent cells (C)
5-Organization means replacement of the damaged tissue by:
- Fibrous tissue (B)
6-A 70-year-old woman presents with acute chest pain and shortness of breath. Laboratory studies and investigations are consistent with acute myocardial infarction. Which of the following is the most likely mechanism of healing of the heart muscles?
- Repair by fibrosis (organization), as heart muscle tissue is composed of permanent cells.