Atrophy is defined as the shrinkage of cell size due to loss of cell substance, which can affect entire tissues or organs without causing cell death. It can be classified as physiologic, such as uterine shrinkage post-childbirth, or pathologic, caused by factors including decreased workload and inadequate nutrition. The underlying mechanisms of atrophy involve decreased protein synthesis, increased protein degradation via the ubiquitin-proteasome pathway, and autophagy, which allows cells to survive by consuming their own organelles.

1. ATROPHY
Presented by:
TALHA SHAHID
Third proff pharm D
SBBU PHARMACY DEPARTMENT

2. DEFINITION
• Atrophy is shrinkage in the size of cells by the loss of cell
substance.

3. • When a sufficient number of cells are involved, the entire tissue
or organ is reduced in size, or atrophic .
• Although atrophic cells may have diminished function, they are
not dead.

4. TYPES
ATROPHY
PHYSIOLOGIC PATHOLOGIC

5. PHYSIOLOGIC ATROPHY
• Uterus following childbirth
• Post menopausal endometrium----- vaginal atrophy
• Shrinkage of mammary glands after lactation.

7. CAUSES OF PATHOLOGIC ATROPHY
1. Decreased workload
2. Decreased blood supply
3. Inadequate nutrition
4. Inadequate innervation (neuropathic)
5. Loss of endocrine stimulation
6. Pressure

8. • Both types of causes lead to the smaller cell size at which
survival is still possible; a new equilibrium is achieved between cell
size and diminished blood supply and nutrition.

11. Atrophic Brain Normal Brain

13. UNDERLYING MECHANISM
• Cellular atrophy results from a combination of decreased
protein synthesis and increased protein degradation.
1. Protein synthesis decreases because of reduced metabolic
activity.

14. 2-PROTEOSOME PATHWAY
• The degradation of cellular proteins occurs mainly by the
ubiquitin-proteasome pathway.
• Nutrient deficiency may activate ubiquitin ligases, which attach
multiple copies of the small peptide ubiquitin to cellular proteins
and target them for degradation in proteasomes----- increased
proteolysis.

15. 3- AUTOPHAGY
• Atrophy also is associated with autophagy, with resulting increases
in the number of autophagic vacuoles.
• Autophagy is the process in which the starved cell eats its own
organelles in an attempt to survive.
• Atrophy can be reversible