Cell Growth and Adaptation

Question 1

What are the classifications of cell growth and adaptation?

Answer 1

• Congenital
  
  • Aplasia
  • Hypoplasia
• Acquired
  
  • Hyperplasia
  • Hypertrophy
  • Atrophy
  • Metaplasia
• Abnormal
  
  • Anaplasia
  • Dysplasia
  • Neoplasia

Question 2

Why do cells grow and adapt?

Answer 2

• Cells confront changes throughout lifespan
  
  • Dynamic changes during development
    
    • embryogenesis and postnatally
  • Increased need for function
    
    • high metabolic activity
  • Decreased need for function
    
    • aging
• Often occurs in the best interest of the animal
  
  • maintain homeostasis based on current need/demands
• Sometimes detrimental
  
  • responding to abnormal or adverse stimuli
  • Cells don’t grow or develop sufficiently

Question 3

What factors influence cell growth and adaptation?

Answer 3

• Cell microenvironment
• Physical / mechanical stressors on tissues and organs
• Genetic alterations of cells

Question 4

What is the cell microenvionment?

Answer 4

• Growth factors and other cytokines
• Properties of the extracellular matrix
• Abnormal or inappropriate cell stimuli
• Nutrients

Question 5

What is Aplasia?

Answer 5

• Cells do NOT grow
• Characterized by absence or partial absence of a tissue / organ
• Results in congenital morphologic abnormalities

Question 6

What is hypoplasia?

Answer 6

• Decreased cell growth
• A developmental problem leading to incomplete or partial formation of a tissue/organ
• Results in congenital morphologic abnormalities

Question 7

What is hyperplasia?

Answer 7

• An increase in the number of cells

Question 8

What is Physiological hyperplasia?

Answer 8

• Cells increase in number to fulfill their functional responsibilities
• Ex:
  
  • Endometrial hyperplasia during pregnancy
  • Fibroblast hyperplasia during healing
  • Mammary glandular hyperplasia during lactation
  • Gastrointestinal epithelial hyperplasia to replace excessive mucosal loss

Question 9

What is Pathological Hyperplasia?

Answer 9

• Increased cell numbers and activity are detrimental to the animal
• Ex:
  
  • Excessive fibroblast proliferation during healing (exuberant granulation tissue)
  • Bone loss secondary to parathyroid hyperplasia (see picture)
  • Thyroid hyperplasia causing tracheal compression

Question 10

What is hypertrophy?

Answer 10

an increase in the size of the cell

Question 11

What is physiological hypertrophy?

Answer 11

• Cells increase in size to fulfill their functional responsibilities
• Ex:
  
  • Uterine smooth muscle during pregnancy
  • Cardiac myocytes during training
  • Skeletal muscle due to increased demands

Question 12

What is pathological hypertrophy?

Answer 12

• Many of the same stimuli that cause physiological hypertrophy become pathologic if they are excessive or inappropriate
• Ex:
  
  • Cardiac myocyte hypertrophy in a failing heart
  • Small intestinal muscular hypertrophy causing intestinal stenosis

Question 13

What is primary hypertrophy?

Answer 13

• Hypertrophy as a primary change is restricted to muscle cells
  
  • Myocytes respond to increased demand by increasing in size, not number
  • Myocytes are post-mitotic cells that do NOT undergo replication

Question 14

Can Hyperplasia and Hypertrophy occur concurrently?

Answer 14

• Yes
• Increased demand for function by most cell types is met by both increased size and increased number of cells
  
  • Epithelial Cells:
    
    • Endocrine - parathyroid
    • Mucosa - Intestinal crypts
    • Parenchyma - Prostate

Question 15

What is atrophy?

Answer 15

• Decrease in size and/or number of cells
  
  • In most cases both size and number of cell decreases

Question 16

What is physiological atrophy

Answer 16

• Occurs in response to a decreased demand for function of the cell
• Ex:
  
  • Endometrial and myometrial atrophy following parturition
  • Mammary glandular atrophy at the end of lactation
  • Myocyte atrophy due to decreased activity or training

Question 17

What is pathological atrophy?

Answer 17

• Inappropriate loss of stimuli or inhibitory stimuli result in atrophy
• Ex:
  
  • Skeletal muscle atrophy following denervation
  • Bone loss due to mineral imbalance, such as occurs with renal failure
  • Loss of stimulation of endocrine tissues

Question 18

What is metaplasia?

Answer 18

• Cell adaptation
• Replacement of one mature cell type with another mature cell type

Question 19

What is physiological metaplasia?

Answer 19

• Often a response to irritation or an adverse environment
• Cells often return to previous type if the cause is removed
• Ex:
  
  • Squamous metaplasia of airway mucosa due to poor air quality/Chronic irritation
  • Squamous metaplasia of salivary and esophageal ducts/glands due to Vit A deficiency

Question 20

What is Pathological Metaplasia?

Answer 20

• Metaplasia often contributes to pathologic change
  
  • Decreased pulmonary defense
  • Decreased glandular secretions
  • Osseous changes in various tissues (See picture)

Question 21

What is cellular dysplasia?

Answer 21

• Abnormal cell morphology and growth
  
  • Size, shape, and appearance of cells is different than normal cells
  • Also typically increased in number
  • Larger nuclei, more organelles, more rapid mitosis
• Causes include chronic irritation or infection
• May represent a pre-neoplastic change

Question 22

What is tissue/organ dysplasia?

Answer 22

• Term sometimes used as a reference to congenital or acquired gross abnormalities characterized by abnormal tissue or organ morphology
• Ex:
  
  • Chondrodysplasia
  • Retinal dysplasia
  • Hip dysplasia

Question 23

What is anaplasia?

Answer 23

• Cells are poorly differentiated
  
  • Lack morphologic features of the cell they were derived from
  • Nuclei and other cell structures often have abnormal morphology
• Common morphologic feature of neoplastic cells
  
  • Provides a morphologic criteria for predicting biological behavior of the neoplasm
    
    • High degrees of anaplasia are usually associated with poorer prognosis

Question 24

What is neoplasia?

Answer 24

• “New growth” of genetically abnormal cells
• Cell morphology can range from normal, to dysplasia, to anaplasia
• Histologic, gross, and biological properties of neoplasms (“tumors”) vary widely