Cellular Adaptations

Question 1

____ involves gene activation, protein synthesis and production of organelles

Answer 1

hypertrophy involves gene activation, protein synthesis and production of organelles

Question 2

permanent tissues (e.g. ____) cannot make new cells and undergo ___ only

Answer 2

permanent tissues (e.g. cardiac muscle, neurons, skeletal muscle) cannot make new cells and undergo hypertrophy only

Question 3

describe the process of atrophy

Answer 3

• decrease in cell size occurs via ubiquitin-proteosome degradation of the cytoskeleton and autophagy of cellular components
  
  • in ubiquitin-proteosome degradation, intermediate filaments of the cytoskeleton are tagged with ubiquitin and destroyed by proteosomes
  • autophagy of cellular components involve generation of autophagic vacuoles
    
    • these vacuoles fuse with lysosomes whose hydrolytic enzymes breakdown cellular components

Question 4

describe 3 possible causes of atrophy

Answer 4

• decrease in size and function of cell due to:
  
  • decreased workload and/or blood supply
  • loss of innervation or aging
  • loss of trophic signals (loss of endocrine stimulation)

Question 5

name 3 potential causes of hyperplasia

Answer 5

• increase in the number of cells due to:
  
  • increased functional demand
  • hormonal stimulation
  • persistent injury

Question 6

describe metaplasia

Answer 6

• a change in stress of an organ leads to a change in cell type (by genetic reprogramming of stem cells)
  
  • most commonly involves change of one type of surface epithelium (squamous, columnar or urothelial) to another
  • metaplastic cells are better able to handle the new stress

Question 7

describe Barrett esophagus

Answer 7

• esophagus is normally lined by nonkeratinizing squamous epithelium (suited to handle friction of food bolus)
• acid reflux from the stomach causes metaplasia to nonciliated, mucin-producing columnar cells (better able to handle stress of acid)

Question 8

describe what is seen in the image

Answer 8

Question 9

metaplasia occurs via reprogramming of _____

Answer 9

metaplasia occurs via reprogramming of stem cells, which then produce the new cell type

Question 10

under persistent stress, metaplasia can progress to ____ and eventually result in ____

name an example and an exception

Answer 10

under persistent stress, metaplasia can progress to dysplasia and eventually result in cancer

• Barrett esophagus may progress to adenocarcinoma of the esophagus
• a notable exception is apocrine metaplasia of breast, which carries no increased risk for cancer

Question 11

____ deficiency can result in metaplasia

explain why

Answer 11

vit. A/retinoic acid deficiency can result in metaplasia

• vit. A is necessary for differentiation of specialized epithelial surfaces such as the conjunctiva covering the eye
• in vit. A deficiency, the thin squamous lining of the conjunctiva undergoes metaplasia into stratified keratinizing squamous epithelium
  
  • this change is called keratomalacia

Question 12

describe what is seen in the image

Answer 12

keratomalacia ; caused by vit. A deficiency, which results in an inability to maintain the highly specialized surface that covers the eye

Question 13

describe dysplasia

Answer 13

disordered cellular growth

• refers to the proliferation of precancerous cells
• enlarged, irregular, dark nuclei
• often arises from longstanding pathologic hyperplasia (endometrial hyperplasia) or metaplasia (Barrett esophagus)
• dysplasia is reversible with alleviation of inciting stress

Question 14

if stress persists, dysplasia progresses to ____ which is _____

Answer 14

if stress persists, dysplasia progresses to carcinoma which is irreversible

Question 15

describe aplasia and name an example

Answer 15

• aplasia is failure of cell production during embryogenesis (e.g. unilateral renal agenesis)

Question 16

describe hypoplasia

Answer 16

• hypoplasia is a decrease in cell production during embryogenesis, resulting in relatively small organs (e.g. streak ovary in Turner syndrome)