Lecture 3 cytology 1 gehan GOLGI & LYSOSOMES_organized.pdf

Golgi apparatus L/M: 1-By H&E: can not be stained, In basophilic cytoplasm of secretory cells, pale area usually appear close to the nucleus (negative Golgi image). 2-Silver: stained dark brown network. Site: * Around the nucleus in nerve cells (multiple). * Supranuclear in secretory cells. EM: 1-St...

Golgi apparatus L/M: 1-By H&E: can not be stained, In basophilic cytoplasm of secretory cells, pale area usually appear close to the nucleus (negative Golgi image). 2-Silver: stained dark brown network. Site: * Around the nucleus in nerve cells (multiple). * Supranuclear in secretory cells. EM: 1-Stacks: - consists of 3- 12 flattened saccules. - One surface towards the nucleus & RER : is convex and is called immature face. - The other surface towards cell membrane is concave and is called mature face. 2-Small vesicles (transfer vesicles): associated with the immature face. They originate from RER. 3-Large vesicles (secretory vesicles): arise from the mature face. Functions of Golgi apparatus: Condensation & concentration of proteins coming from RER. Formation of primary lysosomes. Lysosomes 1- Membranous organelles. 2- L/M: can be identified by using histochemical methods (enzymes). 3- By E.M.: rounded small membranous vesicles: a-Primary lysosomes: contain hydrolytic digestive enzymes, which are synthesized in RER, then transferred to Golgi, where lysosomes bud from. They are homogenous. b- Secondary lysosomes: are formed when primary lysosomes interact with other substance. They are heterogenous. Functions: 1- Digestion of certain substances which may be: a- Solid material that enter the cell by phagocytosis to form a phagocytic vesicle, which when interacts with a primary lysosome, it is called phagosome. b- Fluids that enter the cell by pinocytosis forming a pinocytotic vesicle, which when interacts with a primary lysosome, it is called multivesicular body. c- Dead organelles from inside the cell (dead mitochondria) forming an autophagic vesicle, which when interacts with a primary lysosome, it is called autophagosome. Phagosome, multivesicular body and autophagosome are called secondary lysosomes. The digested materials diffuse into the cytosol. The indigestible materials form residual bodies. 2Cell metabolism: breakdown of exrtacarbohydrates & lipids. 3- Primary lysosomes may release its enzymes by exocytosis (osteoclasts). Types of secondery lysosomes a)Solid material enter by phagocytosis phagosome. b)Fluid material enter by pinocytosis multivesicular body c) Dead organelles (from inside the cell ) as dead mitochondria autophagosome. (phagosome-multivesicular body-autophagosome)