L3, Resp Histology - PDF

Histology - respiratory Respiratory system ( ) LECTURE (3) Respiratory system (3) Dr. M. Shalaby Histology - respiratory Respiratory system ( ) ARISE FROM:  Terminal bronchioles...

Histology - respiratory Respiratory system ( ) LECTURE (3) Respiratory system (3) Dr. M. Shalaby Histology - respiratory Respiratory system ( ) ARISE FROM:  Terminal bronchioles  Ciliated cubical cells LINED BY :  Non ciliated cubical in smaller respiratory bronchioles. SURROUNDED BY  CT contains elastic fibers & smooth muscle fibers. WALL IS  Alveoli which opens directly into lumen. INTERRUPTED BY DEFINITION  Narrow tubes where the alveoli opens in their wall.  Minute air spaces representing functional & structural unit of lung. DEF :  Each group of alveoli which open into a common central space are called Alveolar sac. ① Alveolar epithelium:  Type 1 pneumocytes. STRUCTURE:  Type 2 pneumocytes ② Interalveolar septum. ③ Alveolar pores. Dr. M. Shalaby Histology - respiratory Respiratory system ( ) TYPE 1 PNEUMOCYTES TYPE 2 PNEUMOCYTES NUMBER:  95% of lining epithelium  5 % of lining epithelium  Flat squamous cells less than 0.2  Cuboidal cells um thickness  Rounded central nuclei. LM:  With slightly thickened area  At angles of interalveolar septa. containing nucleus.  Attached to each other by  Attached to type 1 by occluding occluding(tight) junctions (tight) junctions  Have thin basal lamina.  Cytoplasm contains many EM:  Perinuclear cytoplasm contains mitochondria, rER, prominent small Golgi, few mitochondria & Golgi complex & electron dense rER while cytoplasm of thin lamellar bodies rich in portion devoid of organelles. phospholipids.  Provide very thin membrane  Act as progenitor cells for type 1 & FUNCTION: through which Gas exchange type 2 pneumocytes. occurs.  Secrete pulmonary surfactant. PULMONARY SURFACTANT DEF  a mixture of phospholipids which lines the inner aspect of alveoli. FUNCTION  decreases surface tension so, prevent alveolar collapse. TYPE 2 PNEUMOCYTES BY EM Dr. M. Shalaby Histology - respiratory Respiratory system ( ) DEF :  The wall separating air in alveoli from blood in capillaries. ① Type I alveolar cells. STRUCTURE: ② Fused basal laminae of alveolar & endothelial cells of capillaries. ③ The endothelial cells of capillaries.  The interalveolar septa are interrupted by holes called alveolar pores.  These pores are important for communication between the alveoli. Dr. M. Shalaby Histology - respiratory Respiratory system ( )  Mononuclear phagocytes of lungs which represent first line of DEF : defense.  Interalveolar septum. SITE :  On luminal surface of alveoli. ORIGIN:  blood monocytes. SHAPE:  Branched cells with pseudopodia. NUCLEUS:  Irregular. CYTOPLASM:  Vacuolated contains many lysosomes TYPES:  Phagocytose dust or coal particles. DUST CELLS:  In smokers, cytoplasm is crowded with large irregular heterogenous electron dense bodies. HEART  Phagocytose extravasated RBCs. FAILURE  In heart failure, cytoplasm contains many vacuoles with hemosiderin CELLS: granules.  Migrate to bronchi and carried by ciliary action through the upper FATE: airway to pharynx → swallowed or expelled in sputum. Dr. M. Shalaby Histology - respiratory Respiratory system ( ) ① Alveolar epithelium on either sides. ② Capillary network (pulmonary capillary bed). STRUCTURE ③ Supporting network of reticular & elastic fibers and C.T. cells (Septal cells, mast cells, lymphocytes & WBC). ④ Basement membranes of alveolar epithelium & capillary beds. IN CERTAIN The 2 membranes fuse → alveolar capillary membrane. SITES Dr. M. Shalaby