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What happens to permanent cells when they are lost?
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What happens to permanent cells when they are lost?
Permanent cells cannot divide and replace lost cells by the same cell type. Instead, repair by fibrosis occurs.
What is atrophy?
Atrophy is a reduction in the mass of cells leading to a reduction in size of the tissue or organ.
What is the process of repair by fibrosis?
In this process, dead tissue is removed and scar tissues (collagen-rich fibrous tissue) fill the defect.
What are the two mechanisms involved in atrophy?
A reduction in the number of cells through apoptosis and a reduction in the size of cells.
What does the scar tissue provide to the damaged tissue?
The scar provides continuity and strength to the tissue but results in the loss of original function.
What is hypertrophy?
Hypertrophy is the increase in the size of cells.
What do cells and tissues need to maintain in order to function appropriately?
A steady state (homeostasis).
In what conditions does atrophy occur?
Atrophy occurs in physiological conditions, during normal growth and development, generally due to loss of endocrine stimulation.
When is repair rather than regeneration likely to occur?
Repair rather than regeneration is likely when labile or stable tissue shows extensive injury.
What is hyperplasia?
Hyperplasia is the increase in the number of cells.
What are cells capable of adapting to within defined limits?
A variety of stimuli which may upset normality.
What is regeneration in the context of normal cell growth?
Regeneration is the process where cells that are lost through death or injury are replaced.
How do hypertrophy and hyperplasia differ?
Hypertrophy involves an increase in cell size, while hyperplasia involves an increase in cell number.
What is cellular adaptation?
The state between a normal unstressed cell and the overstressed injured cell.
What are labile tissues?
Labile tissues are continuously changeable and have a short life span, such as bone marrow and gut epithelium.
What does normal growth of tissues depend on?
Normal growth of tissues depends on a balance between the number of cells actively dividing and the number of cells dying.
Is the adaptive process reversible?
Yes, the adaptive process is potentially reversible.
What are examples of labile tissues?
Bone marrow and gut epithelium.
What causes skeletal muscle hypertrophy in bodybuilders or athletes?
Physiological conditions.
What type of cells are capable of repeated mitotic activity in tissues?
Stem cells are capable of repeated mitotic activity in tissues.
What characterizes stable tissues?
Stable tissues have a slow turnover and long-lived differentiation, such as liver and kidney tissues.
What physiological changes occur in the myometrial smooth muscle during pregnancy?
Hypertrophy and hyperplasia causing enlargement of the pregnant uterus.
Can differentiated cells return to the cell cycle and divide?
Yes, sometimes differentiated cells can return to the cell cycle and divide to produce daughter cells.
What is denervation and how does it cause pathological atrophy?
Denervation is the wasting of muscle caused by lack of nerve stimulation, for example, Poliomyelitis.
What are the four main stages of the cell cycle?
M phase, G1 phase, S phase, G2 phase.
What are examples of stable tissues?
Liver and kidney tissues.
What happens to the breasts during lactation in terms of physiological changes?
Hypertrophy and hyperplasia.
What pathological condition is associated with cardiac muscle in hypertension?
Cardiac muscle hypertrophy.
What are the four main adaptive states in cellular adaptation?
Atrophy, Hypertrophy, Hyperplasia, and Metaplasia.
How does reduced blood supply lead to pathological atrophy?
Reduced blood supply, such as the shrinkage of the brain caused by atherosclerosis of carotid arteries, leads to pathological atrophy.
What occurs during the M phase of the cell cycle?
Mitosis, when the cell divides (about 1 hour).
What are permanent tissues?
Permanent tissues contain cells capable of division only in fetal life, and cell loss after birth cannot be replaced, such as neurons and cardiac muscle cells.
What compensatory changes occur in the remaining kidney after the other kidney is removed?
Hypertrophy and hyperplasia.
What is atrophy?
Shrinkage of an organ as a result of decrease in cell size and/or number.
What causes hyperplasia of the adrenal gland in pathological conditions?
Excess of ACTH hormone by a pituitary neoplasm.
What is the effect of inadequate nutrition on muscles and major organs?
Inadequate nutrition can cause the wasting of muscles and major organs, as seen in starvation.
What is metaplasia?
Metaplasia is the term used when one differentiated tissue is replaced by another. It is a potentially reversible change; if the cause of metaplasia is removed, the tissue may revert to normal.
What is the G1 phase of the cell cycle?
Gap 1, the preparation for S phase.
What are examples of permanent tissues?
Neurons and cardiac muscle cells.
What is hypertrophy?
Enlargement of an organ as a result of increased cell size.
What is the cause of hyperplasia of the prostate gland in pathological conditions?
An abnormal response of androgens.
How does loss of endocrine stimulation result in pathological atrophy?
Loss of endocrine stimulation, such as infarction of the pituitary, results in atrophy of the thyroid and adrenal glands.
What happens to bronchial epithelium in smokers?
Bronchial (pseudo-stratified ciliated columnar) epithelium changes to squamous epithelium in smokers.
What happens during the S phase of the cell cycle?
DNA synthesis.
What is hyperplasia?
Enlargement of an organ through an increase in cell number.
What are the two ways an organ or tissue can enlarge?
An organ or tissue can enlarge due to an increase in the number of constituent cells or an increase in the size of the cells.
What causes bladder smooth muscle hypertrophy and hyperplasia in pathological conditions?
Enlargement of the prostatic gland.
What is pressure atrophy and what causes it?
Pressure atrophy is caused by adjacent tumors or cysts.
What type of metaplasia occurs in the bladder due to stones and infection?
Transitional bladder epithelium changes to squamous epithelium in bladder stones and infection.
What occurs during the G2 phase of the cell cycle?
Gap 2, distribution of chromosomes takes place.
What is metaplasia?
Change in tissue type as a result of replacement of one differentiated cell type by another.
What is hypertrophy?
Hypertrophy is an increase in mass due to an increase in cell size.
What type of metaplasia occurs in the lower oesophagus in patients with gastro-oesophageal reflux?
Stratified squamous epithelium changes into glandular epithelium in the lower oesophagus in patients with gastro-oesophageal reflux.
What is the G0 phase in the cell cycle?
A non-proliferative or growth arrest phase.
What factors control the adaptive states of cells?
A complex web of genetic and environmental factors that control normal growth and development.
What is hyperplasia?
Hyperplasia is an increase in mass due to an increase in cell number.
Can cells in the G0 phase re-enter the cell cycle?
Yes, they may re-enter at G1 and regain the proliferative state.
Do hypertrophy and hyperplasia commonly occur together?
Yes, in practice hypertrophy and hyperplasia commonly occur together.
Are the adaptive states of cells reversible?
In general, they are potentially reversible.
What factors are important for cells in G0 to re-enter the cell cycle?
Growth factors.
What is required for hyperplasia to occur?
Hyperplasia requires that the cells be capable of division and can occur only in labile and stable cell populations.
What are the two main controls of the cell cycle?
Growth factors and cyclins.
Can permanent cell populations undergo hyperplasia?
No, permanent cell populations can only enlarge by hypertrophy.
Are hypertrophy and hyperplasia reversible conditions?
Yes, both hypertrophy and hyperplasia are reversible conditions. If the cause is removed, the tissue can return towards normal.