Lecturer name: Dr. Maha Arafah Lecture Date: 27-9-2011 (Foundation Block, Pathology)
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Transcript of Lecturer name: Dr. Maha Arafah Lecture Date: 27-9-2011 (Foundation Block, Pathology)
INTRACELLULAR ACCUMULATIONS and CALCIFICATION
Lecturer name: Dr. Maha ArafahLecture Date: 27-9-2011
(Foundation Block, Pathology)
Objectives Understand the pathological changes
leading to abnormal accumulations of pigments and other substances in cells.
List conditions and features of fatty change, haemosiderin, melanin and lipofuscin accumulations in cells.
Know the main types and causes of calcifications (dystrophic and metastatic).
Degeneration
Degeneration is used to describe pathological processes which result in deterioration (often with destruction) of tissues and organs.
Examples:1. Osteoarthritis : a degenerative joint disease in
which gradual destruction and deterioration of the bones and joint occurs.
2. Alzheimer's disease : a degenerative neurological disease where there is a progressive deterioration in brain function.
3. Solar elastosis: UV-induced degeneration of the connective tissue in skin.
Accumulation
Under some circumstances cells may accumulate abnormal amounts of various substances.
They may be harmless or associated with varying degrees of injury .
Cells may accumulate pigments or other substances as a result of a variety of different pathological or physiological processes.
Overview of Accumulation
May be found: in the cytoplasm within organelles (typically lysosomes) in the nucleus
The accumulations can be classified as endogenous or exogenous.
Came to the cell through: Synthesis by affected cells Produced elsewhere.
Fatty Change
Fatty change refers to any abnormal accumulation of triglycerides within parenchymal cells.
It is usually an early indicator of cell stress and reversible injury.
Site: liver, most common site which has a central role in
fat metabolism. it may also occur in heart: anaemia or starvation
(anorexia nervosa) Other sites: skeletal muscle, kidney and other
organs.
Causes of Fatty Change
Toxins (most importantly: Alcohol abuse)
diabetes mellitus Protein malnutrition (starvation) Obesity Anoxia
Hepatotoxins (e.g. alcohol) by disrupting mitochondria and SER ; anoxia
CCl4 and protein malnutrition
Starvation will increase this
•Defects in any of the steps of uptake, catabolism, or secretion can lead to lipid accumulation.
The significance of fatty change
Depends on the cause and severity of the accumulation. Mild it may have no effect on cellular function. Severe fatty change may transiently impair
cellular function
The iron is toxic to the tissues and leads to fibrosis of the liver (cirrhosis) and pancreas (leading to diabetes mellitus).
Light microscopy of fatty change
Early: small fat vacuoles in the cytoplasm around the nucleus.
Later stages: the vacuoles coalesce to create cleared spaces that displace the nucleus to the cell periphery
Occasionally contiguous cells rupture (fatty cysts)
Is Fatty liver reversible?
Fatty change is reversible except if some vital intracellular
process is irreversibly impaired (e.g., in CCl4 poisoning),
Prognosis of Fatty liver
Mild: benign natural history (approximately 3% will develop cirrhosis
Moderate to sever: inflammation, degeneration in hepatocytes, +/- fibrosis (30% develop cirrhosis)
5 to 10 year survival:67% and 59%
Other form of accumulation
Cholesteryl esters These give atherosclerotic plaques their characteristic yellow color and contribute to the pathogenesis of the lesion This is called atherosclerosis
Pigments are colored substances that are either: exogenous, coming from outside the
body, or endogenous, synthesized within the
body itself.
Exogenous pigment
Pigments and insoluble substances may enter the body from a variety of sources.
They may be toxic and produce inflammatory tissue reactions or they may be relatively inert.
Indian ink pigments produce effective tattoos because they are engulfed by dermal macrophages which become immobilized and permanently deposited.
Exogenous pigment
The most common is carbon When inhaled, it is phagocytosed by
alveolar macrophages and transported through lymphatic channels to the regional tracheobronchial lymph nodes.
Exogenous pigment
Aggregates of the pigment blacken the draining lymph nodes and pulmonary parenchyma (anthracosis).
Exogenous pigmentCarbon in Lung
Heavy accumulations may induce emphysema or a fibroblastic reaction that can result in a serious lung disease ( coal workers' pneumoconiosis)
Endogenous pigments
Endogenous pigments include certain derivatives of hemoglobin, melanin, and lipofuscin.
Hemosiderin ( iron)
is a hemoglobin-derived granular pigment that is golden yellow to brown and accumulates in tissues when there is a local or systemic excess of iron.
Hemosiderin pigments is composed of aggregates of partially degraded ferritin, which is protein-covered ferric oxide and phosphate.
It can be seen by light and electron microscopy
Hemosiderin ( iron)
Although hemosiderin accumulation is usually pathologic, small amounts of this pigment are normal.
Where? in the mononuclear phagocytes of the
bone marrow, spleen, and liver. Why?
there is extensive red cell breakdown.
Hemosiderin
Local excesses of iron, and consequently of hemosiderin, result from hemorrhage.
Bruise: The original red-blue color of hemoglobin is transformed to varying shades of green-blue by the local formation of biliverdin (green bile) and bilirubin (red bile) from the heme
HemosiderinThe iron ions of hemoglobin accumulate as golden-yellow hemosiderin.
The iron can be identified in tissue by the Prussian blue histochemical reaction
Hemosiderosis(systemic overload of iron)
is systemic overload of iron, hemosiderin is deposited in many organs and tissues
Site: liver, bone marrow, spleen, and lymph nodes
With progressive accumulation,
parenchymal cells throughout the body (principally the liver, pancreas, heart, and endocrine organs) will be affected
Hemosiderosis
Hemosiderosis occurs in the setting of:
1.increased absorption of dietary
iron 2.impaired utilization of iron3.hemolytic anemias4.transfusions (the transfused red
cells constitute an exogenous load of iron).
.
Effect of hemosiderosis
In most instances of systemic hemosiderosis, the iron pigment does not damage the parenchymal cells
However, more extensive accumulations of iron are seen in hereditary hemochromatosis with tissue injury including liver fibrosis, heart failure, and diabetes mellitus
Melanin
Melanin is the brown/black pigment which is normally present in the cytoplasm of cells at the basal cell layer of the epidermis, called melanocytes.
The function of melanin is to block
harmful UV rays from the epidermal nuclei.
Melanin: Causes of accumulation
Melanin may accumulate in excessive quantities in benign or malignant melanocytic neoplasms and its presence is a useful diagnostic feature melanocytic lesions.
In inflammatory skin lesions, post-inflammatory pigmentation of the skin.
Lipofuscin
"wear-and-tear pigment" is an insoluble brownish-yellow granular intracellular material that seen in a variety of tissues (the heart, liver, and brain) as a function of age or atrophy.
Brown atrophy
Pathologic calcification
is a common process in a wide variety of disease states
it implies the abnormal deposition of calcium salts with smaller amounts of iron, magnesium, and other minerals.
It has 2 types:
Types of Pathologic calcification
Dystrophic calcification: When the deposition occurs in dead or
dying tissues it occurs with normal serum levels of
calcium
Metastatic calcification: The deposition of calcium salts in normal
tissues It almost always reflects some
derangement in calcium metabolism (hypercalcemia)
Dystrophic calcification:
Dystrophic calcification is encountered in areas of necrosis of any type.
It is certain in the atheromas of advanced atherosclerosis, associated with intimal injury in the aorta and large arteries
Although dystrophic calcification may be an incidental finding indicating insignificant past cell injury, it may also be a cause of organ dysfunction.
For example, Dystrophic calcification of the aortic valves is
an important cause of aortic stenosis in the elderly
Morphology of Dystrophic calcification
calcium salts are grossly seen as fine white granules or clumps, often felt as gritty deposits.
Sometimes a tuberculous lymph node is essentially converted to radio-opaque stone.
Histologically, calcification appears as intracellular and/or extracellular basophilic deposits.
In time, heterotopic bone may be formed in the focus of calcification.
Metastatic calcification
Metastatic calcification can occur in normal tissues whenever there is hypercalcemia.
Metastatic calcificationMain causes:
1. increased secretion of parathyroid hormone
2. destruction of bone due to the effects of accelerated turnover (e.g., Paget disease), immobilization, or tumors (multiple myeloma, leukemia, or diffuse skeletal metastases)
3. vitamin D-related disorders including vitamin D intoxication
4. renal failure, in which phosphate retention leads to secondary hyperparathyroidism.
Morphology of Metastatic calcification
Metastatic calcification can occur widely throughout the body but principally affects the interstitial tissues of the vasculature, kidneys, lungs, and gastric mucosa.
The calcium deposits morphologically resemble those described in dystrophic calcification.
Effect of Metastatic calcification
Extensive calcifications in the lungs may produce remarkable respiratory deficits
Massive deposits in the kidney
(nephrocalcinosis) can cause renal damage.