Cell Growth and a\Adaptation Flashcards
Cell Growth and Adaptation
Cells confront chages throughout their lifespan that may require them to adapt
Dynamic changes during development
Increased need for function
Decreased need for function
Often occurs in the best interest of the animal (maintain Homeostasis)
Sometimes these changes are detrimental
Factors influencing cell growth and adaptation
Cell microenvironment
- Growth factors and other cytokines
- Properties of the extracellular matrix
- Abnormal or inappropriate cell stimuli
- Nutrients
Physical or mechanical stressors on tissues and organs
Genetic alteration of cells
Aplasia
A- no
Plasia - growth
This is characterized by the absence or partial absence of a tissue or organ
It results in congenital morphologic abnormalities
Hypoplasia
Hypo-Little/small
Plasia - Growth
Decreased gwoth of cells
Developmental problem leading to incomplete or partial formation of a tissue or organ
Results in congenital morphologic abnormalities
Cell Adaptation
Usually a response of cells to help maintain Homeostasis
Often a response to physiological events
Its a response to a changing cell/tissue environment
Some adaptations are a response to pathologic change
Some adaptations lead to pathological change
Cell Adaptation:
Hyperplasia
Hyper - increased
Plasia - growth
Increase in the number of cells
Physiological Hyperplasia
Cells increase in number to fulfill their functional responsibilities
- Endometrial hyperplasia during pregnancy
- Fibroblast hyperplasia during healing
- Mammary gladular hyperplasia during lactation
- Gastrointestinal epithelial hyperplasia to replace excessive mucosal loss
Pathological Hyperplasia
Increased cell numbers and activity are detrimental to the animal
- Excessive fibroblast proliferation during healing
- Bone loss secondary to parathyroid hyperplasia
- Thyroid hyperplasia causing tracheal compression
Cell Adaptation:
Hypertrophy
An increase in the size of a cell
Typically muscle cells
Pysiological Hypertrophy
Cells increase in size to fulfill their functinal responsibilities
- Uterine smooth muscle hypertrophy during pregnancy
- Cardiac Myocyte Hypertrophy during training
- Skeletal muscle hypertrophy due to increased demands
Pathological Hypertrophy
Many of the same stimuli that cause physiological hypertrophy become pathologic if they are excessive or inappropriate
Cardiac Myocyte hypertrophy in a failing heart
Small intestinal muscular hypertrophy causing intestinal stenosis
What tissue undergoes primary hypertrophy
As a primary change is restricted to muscle cells
Myocytes respond to increased demand by increasing size, not by increasing in number
Myocytes are post-mitotic cells that do NOT undergo replication
Hyperplasia and Hypertrophy
In many tissues they often occur concurrently
Increased demand for function by most cell types is met by both increased size and increased number of cells
Cell Adaptation:
Atrophy
The decreased size and or number of a cell
In most cases both decrease
Physiological Atrophy
- Occurs in response to a decreased demand for the function of the cell
- Examples:
- endometrial and myometrial atrophy following parturition
- Mammary glandular atrophy at the end of lactation
- Myocyte atrophy dur to decreased activity or training
Pathological Atrophy
- Inappropriate loss of stimuli or inhibitory stimuli
- Examples:
- Skeletal muscle atrophy following dennervation
- Bone loss (atrophy) due to mineral imbalance, such as occurs with renal failure
- Loss of stimulation of endocrine tissue
Physiological Metaplasia
- Often a response to irritation or an adverse environment
- Squamous metaplasia of airway mucous due to poor air quality/chronic irritation
- Squamous metaplasia of salivary and esophageal ducts/glands due to a Vitamin A deficiency in birds
Pathological Metaplasia
- Often contributes to pathologic change
- decreased pulmonary defense
- Decreased Glandular secretions
- Osseous changes in various tissues
Abnormal Changes:
Dysplasia - Tissue/Organ level
- This term is sometimes used as a reference to congenital or acquired gross abnormalities characterized by abnormal tissue or organ morphology
- Examples:
- Chondrodysplasia
- chondro - cartilage
- Retinal Dysplasia
- Hip Dysplasia
- acquired with a genetic basis
- Chondrodysplasia
Abnormal Changes:
Anaplasia
- Cells are pooly differentiated
- they lack morphologic features of the cell that they were derived from
- Nuclei and other cell structures often have abnormal morphology
- This is a common morphologic feature of neoplastic cells
- provides a morphologic criteriafor prediciting biological behavior of the neoplasm
- high degree of anaplasia are usually associated with a poorer prognosis
- provides a morphologic criteriafor prediciting biological behavior of the neoplasm
Abnormal Changes:
Neoplasia
- “New growth” of genetically abnormal cells
- mutations and lack of regulatory control
- Cell morphology can range from normal to dysplasia, to anaplasia
- Histologic, gross, and biological properties of neoplasms vary widely
