Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Death and Necrosis LECTURE FOUR 1 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Answer the following :Difference between & 2 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Contents Definition Death and Necrosis Macroscopic characteristic of death tissues Causes of Necrosis Types of necrosis Fate of necrotic tissues 3 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Definitions Necrosis: death of cells and tissues while the body is whole still living. After a cell dies, lysosomes rupture and their hydrolytic enzymes are released into the cell. The release and activation of these lysosomal enzymes are largely responsible for cell necrosis. 4 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Necrobiosis: The natural death of cells or tissues through aging, as distinguished from necrosis e.g. – Enterocytes – Kerotinocytes in the skin cells constantly dying and being replaced 5 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Autolysis: The destruction of tissues or cells by the action of enzymes, that are produced within the cells. Also called selfdigestion. Heterolysis: destruction of tissues or cells by the action of enzymes from outside of cells (neutrophils). 6 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Dead and Necrosis Death refer to the complete cessation of vital function of the cells and tissues and its include: 1- General (somatic) death 2- Local death which include: A- Physiological local death (Necrobiosis) e.g. RBCs and squamous cell after end of their life span. B- Necrosis. 7 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Macroscopic characteristic of death tissues Regardless of necrosis or somatic death, death tissue is characterized by the following: 1- loss of its normal color, necrotic tissue tends to be lighter in color (unless filled with blood, then darker); due to loss of cytochrome oxidases. 8 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 2- Loss of its elasticity, it become friable and tend to rupture with mild mechanical force. 3- Autolysis, the destruction of tissues or cells by the action of enzymes that are produced within the cells. 9 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 4- Putrefaction, due to invasion by saprophytic bacteria. 5- Presence of demarcation line between necrotic tissue and normal tissues (due to inflammation). 10 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 General causes of necrosis: Poisons and toxins: Chemical: Strong acids, alkalies, insecticides, mercury etc. Infectious agents: Bacteria (Salmonella, Staphylococcus), viruses, fungi, protozoa etc. Plant poisons- hepatotoxic alkaloids . Circulatory disturbance: Anemia, congestion and ischemia. Mechanical injuries: Cutting, crushing and rubbing types. Physical : Extreme temperature, electricity, free radical. 11 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Causes of Necrosis Loss of blood supply (ischemia) Loss of nerve supply Loss of endocrine stimulation Endotoxin Mechanical/thermal injury Chemical injury Pressure 12 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Gross appearance: Affected areas white, gray or yellow in colour. Have a cooked meat appearance. Sharply demarcated (by red zone) from healthy tissue. In case of gangrene the area is green, orange or black ( iron sulphide) 13 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 14 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 Nuclear changes: Occur due to hydrolysis of nucleoproteins: i. Pyknosis i.e. the nucleus becomes shrunken condensed and deeply stained. ii. Karyorrhexis: rupture of nuclear membrane with fragmentation of the nucleus. iii. Karyolysis: the nucleus dissolves and disappears. 15 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 16 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016 17 DR.ABDIAZIZ ABDI MOHAMED ABDI 3/10/2016