Exam 4: Atrophy Flashcards
What is atrophy?
A condition where the decrease in the size of normally developed cells, tissues, or organs occurs
Decrease in cell number or size
What is the response to an altered cell environment?
Atrophy
What are the 2 ways that an organ can shrink with atrophy?
Cell deletion-apoptosis
Cell shrinkage
What happens with cell deletion-apoptosis?
The most specialized cells removed first, leaving stroma
What is cell shrinkage?
Each cell must trim down excess
What must occur with cell shrinkage?
Proteolysis
What is autophagy?
A survival mechanism during ischemia or a response to hormones
How does autophagy occur?
Cells consume damaged organelles and recycle proteins and carbohydrates
An autophagosome is produced, containing dysfunctional organelles –> residual bodies –> may be retained
What are the protein removal control systems associated with atrophy?
Ubiquitin-proteasome
Chapeone mediated autophagy
Macroautophagy
What is atrophy caused by decreased use/function?
Inactivity or limited movement- promotes protein catabolism
What is physiologic atrophy?
Programmed cell death of certain tissues
What is atrophy caused by cachexia?
Diffuse muscle wasting- catabolism via the ubiquitin-proteasome pathway
Serous atrophy of fat- utilization
What is atrophy due to impaired bloodflow?
Chronic ischemia- prolonged partial inadequacy of blood
What is atrophy due to pressure?
Growing tumors cause local pressure in part due to reduced bloodflow. Constant local pressure stimulates osteoclasts- bone loss
What is atrophy due to duct occlusion?
Exocrine glands- pancreas, salivary glands lose secretory cells by apoptosis
KIdney- occlusion of ureter leads to hydronephrosis
What is atrophy due to hormones/endocrine?
Natural sexual cycles- ovary and testicles
Iatrogenic supply of hormone- the best way to atrophy an endocrine gland is with its own hormone
What is affected by atrophy due to age?
Reproductive organs, then muscles, bone, and nervous system
What is atrophy due to denervation?
Motor nerve- marked effects on skeletal muscle
Sensory nerve- skin atrophies, nails become brittle
Sympathetic- metabolic effects on arteries, salivary gland atrophy, perirenal fat metaplasia
What is atrophy due to inflammation?
Cytokines cause atrophy in organs
What is seen grossly with atrophy?
Reduction in the size of the organ or tissue
Normal shape and form are usually maintained
May be firmer in consistency
May be darker in color because the blood vessels will be closer together
What is seen microscopically with atrophy?
Cells are smaller
A given field may look more cellular due to smaller size and closer proximity of cells
Increased connective tissue from condensation or from replacement of tissues lost to ischemia or exhaustion
Lipochrome pigments may be present in the cytoplasm of atrophic heart and liver cells. May give these organs a brown appearance, termed brown atrophy
What may replace atrophied tissue in the pancreas and skeletal or heart muscle?
Fat
What are the 2 options available for an organ to shrink?
Loss of cells or reduction in cell size
How does cell deletion by programmed cell death (apoptosis) occur?
By heirarchy
In glands, the most specialized cells are removed before the ducts
The stroma however is spared, thus atrophied organs appear to contain too much connective tissue
What must a cell do in order to shrink?
It must lyse its proteins (proteolysis) through the autophagocytosis pathway or the proteasome pathway
How does obstruction cause atrophy in the kidney?
The obstructions causes pressure to build up in the kidney, and the pressure interferes with both the blood supply and with the lymph and blood drainage from the kidney. Catabolic products accumulate and cells are forced to decrease in size and number. The renal pelvis expands and the medullary and cortical tissues diminish
