Cell Junctions PDF

**Cell junctions** General Biology & Cytology 1. **Tight junction** 2. **Adherens junction** 3. **Gap junction** INTERCELLUAR JUNCTIONS ====================== +-----------------------------------+-----------------------------------+ | - **Site : below Zonula |...

**Cell junctions** General Biology & Cytology 1. **Tight junction** 2. **Adherens junction** 3. **Gap junction** INTERCELLUAR JUNCTIONS ====================== +-----------------------------------+-----------------------------------+ | - **Site : below Zonula | | | occludens.** | | | | | | - **Structure:** | | | | | | | | | | | | - **intercellular space is | | | narrow 15 nm ( an electron | | | dense binding substance.** | | | | | | - **On the cytoplasmic surface | | | of the opposed cell membrane | | | there is Plaque.** | | +-----------------------------------+-----------------------------------+ | | | +-----------------------------------+-----------------------------------+ | **Desmosomes** | | +-----------------------------------+-----------------------------------+ 1. **direct passage of ions between cells** 2. **rapid transmission of nerve impulse between cardiac ms cells so heart contract as one unit** Epithelial polarity - Cells have a top and a bottom and side modifications - So different activities take place at different places Cell polarity ------------- a. Apical modifications b. Basal modifications c. Lateral modifications formed of actin filaments **Apical modifications [Stereocilia]** Not true cilia but long microvilli. Non motile cilia ### Apical modifications [Cilia] ### Basal modifications Basal infolding #### Basement membrane membrane