Cellular adaptations Flashcards
What is hypertrophy?
Increase in the size of cells that results in an increase in the size of the affected organ
What is Physiologic hypertrophy?
It is increased functional demand or stimulation by hormones and growth factor
What is Pathologic hypertrophy?
increased functional demand or stimulation secondary to pathological process
What is hyperplasia?
Increase in the number of cells in an organ or tissue in response to a stimulus
What is physiologic hyperplasia?
Action of hormones or growth factors when there is a need to increase
functional capacity of hormone sensitive organs, or when there is
need for compensatory increase after damage or resection
WHat is pathologic hyperplasia?
Most forms of pathologic hyperplasia are caused by excessive or inappropriate actions of hormones or growth factors acting on target cells
What are some examples of physiologic hyperplasia?
Hyperplasia of bone marrow cells
- Red blood cells: growth factor erythropoietin
• Lymphoid hyperplasia
- Inflammation or antigenic stimulation
• Regenerative hyperplasia
- Regeneration of tissues (liver or skin)
• Hyperplasia of breast tissue
- Puberty, pregnancy and lactation: several hormones
What are some examples of pathologic hyperplasia?
Thyroid Hyperplasia
- Increased thyroid-stimulating hormone: the anterior pituitary
• Endometrial hyperplasia
- Occurs in postmenopausal women with increased estrogen
- Predisposes to malignant tumors of the endometrium
• Prostatic hyperplasia
- Hyperplasia of the stromal & epithelial components of the prostate.
- Prostatic glands increase in size & have a nodular surface.
- Caused by an imbalance between androgens and estrogens
What is atrophy?
Reduction in the size of an organ or tissue due to a decrease in cell size and
number
What is physiologic atrophy?
-Embryonic structures – Notochord, thyro-glossal duct,
• Uterus post-partum
What is pathologic atrophy?
- Disuse atrophy • Denervation atrophy • Diminished blood supply • Inadequate nutrition • Loss of endocrine stimulation • Pressure
What are examples of physiologic atrophy?
Is common during normal development.
• Embryonic structures: notochord & thyroglossal duct
• Size of the uterus after parturition
• Thymus undergoes physiologic atrophy at puberty
• As one ages the organs & tissues decrease in size: senile atrophy
Why does disuse lead to atrophy?
Reduced functional activity
- Results in diminished demand for nutrition causing cell atrophy.
- E.g. an immobilized arm post-fracture.
- Usually reversible when activity is restored
Why does loss of innervation cause atrophy?
Loss of innervation (denervation atrophy)
- Destruction to nerves: paralysis and wasting atrophy
- Poliomyelitis
Why does diminished blood supply cause atrophy?
Diminished Blood Supply
- Reduction of the oxygen and nutrient supply to cells.
- A fall in cell activity occurs; cell shrinkage.
- Narrowing of coronary arteries; myocardial atrophy
Why does pressure cause atrophy?
Pressure atrophy- Interruption of the blood supply & interference with function
- A neoplasm pressing on surrounding structures
Why do infections cause atrophy?
Infections;
- Thymus atrophy before puberty due to infections
Why Loss of endocrine stimulation cause atrophy?
- Reduced metabolic activity in dependent tissues
- Pituitary deficiency: atrophy of the thyroid and adrenals
What happens during Cerebral atrophy?
• Gyri are narrowed and the
intervening sulci are widened
What is metaplasia?
Reversible change in which one differentiated cell type is replaced by another differentiated cell type
Metaplasia occurs in ?
Epithelia
Connective tissue
Epithelial metaplasia occurs in which occurs organs?
Epithelial
- Columnar to squamous epithelium – lung
- Squamous to columnar epithelium – Oesophagus
Squamous metaplasia
- Most common type of metaplasia.
* Important sites: bronchus, endocervix, and the urinary bladder
Squamous metaplasia bronchus
Lined by pseudostratified columnar ciliated epithelium.
• Squamous metaplasia occurs when there is chronic irritation by cigarette smoke or chronic inflammation caused by bronchitis.
• There is a loss of the protective mechanism against infection
