Epithelium (3) - Biomedical Sciences PDF

Introduction to Biomedical Sciences Epithelium (3) Prof. D. Dina Helmy Issue 1/ 2018 Code: SOM1-1 Issue 1/ Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018...

Introduction to Biomedical Sciences Epithelium (3) Prof. D. Dina Helmy Issue 1/ 2018 Code: SOM1-1 Issue 1/ Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018  Code of conduct Effective interaction Switch off mobile Mutual respect phones Smile Appreciate our Struggle to be on time differences Focus on topic Issue 1/ Code: SOM1-1 2018 Intended learning outcomes By the end of the lecture, the students will be able to: Define cell polarity Recognize types of lateral, apical and basal specialization. Describe the types of cell junctions and their Issue 1/ 1 Code: SOM1-1 2018  Contents Apical specializations Lateral specializations Basal specializations Issue 1/ 2 Code: SOM1-1 2018  Cell Polarity 1. Microvilli Apical specializations 1.Tight junction 2. Steriocili 2.Adherens jun. a 3.Desmosomes 3. Cilia 4.Gap junction. 4. Flagella 5.Lat. interdigitation s Lateral specializati 1. Hemidesmosomes. ons 2. Basement membrane 3. Basal infoldings Basal specializations Code: SOM1-1  I- Apical specializations 1- Microvilli Finger like projections. Non-motile. Shorter than cilia. LM: acidophilic brush border. Code: SOM1-1 EM: full of actin microfilaments attached to Actin terminal web & covered by cell membrane. Termin al web  Function: increase surface area for absorption 1 Code: SOM1-1  2- Stereocilia Long microvilli LM: acidophilic hair like projections (previously called non-motile cilia). EM: long microvilli with actin filaments. Function: increase surface area for absorption. Issue 1/ 2018 1 Code: SOM1-1  3- Cilia Long motile finger-like projections. LM: acidophilic hair-like projections. Function: Push fluids or particles in one direction. Issue 1/ 1 Code: SOM1-1 2018  EM: 1- Basal body: similar to centriole. 2- Shaft: (20 microtubules) - 2 central singlets - 9 peripheral doublets - covered by cell membrane Issue 1/ 1 Code: SOM1-1 2018  4- Flagella Single long cilium Help movement of sperms. Issue 1/ 1 Code: SOM1-1 2018  II- Lateral specializations i- Cell junctions 1- Tight (occluding) junction: Adjacent cell membranes fuse completely at certain point. Surround the cell like a belt. Issue 1/ 1 Code: SOM1-1 2018 2- Adherens junction (zonula adherens) : Adjacent cell membranes are separated by a wide space (20 nm) filled with transmembrane proteins + Ca. Actin is condensed on cytoplasmic side. Surrounds the cell like a belt. Adhere cells together. Issue 1/ 1 Code: SOM1-1 2018 3- Desmosomes (macula adherens): Adjacent cell membranes are separated by a wide space (30 nm) filled with adhesive material. Scattered like patches. Thickened cytoplasmic side (plaque) in which tonofilaments are attached. Strongest type of junction. Issue 1/ 1 Code: SOM1-1 2018 4- Gap junction 6 integral (nexus) : proteins Adjacent cell membranes are separated by a narrow gap (2 nm) and connected by channels. Each channel is formed of 2 connexons. Each connexon if formed of 6 integral proteins. Allow exchange of ions, nutrients & impulses between the cells. Issue 1/ 1 Code: SOM1-1 2018  Cell junctions Code: SOM1-1 19  ii- Lateral interdigitations Interlocking membrane folds of adjacent cell membranes joining the cells together. Issue 1/ 1 Code: SOM1-1 2018  III- Basal specializations 1- Hemidesmosomes Half a desmosome. : Attach the base of the cells to the basement membrane. Issue 1/ 1 Code: SOM1-1 2018  2- Basement membrane: Underneath epithelium between it and connective tissue. LM: PAS and Ag. EM: Formed of: a.Basal lamina: - Lamina lucida: glycoprotein + collagen IV - Lamina densa: dense collagen IV b. Reticular lamina: collagen III Issue 1/ 1 Code: SOM1-1 2018 Basement membrane BL RL Code: SOM1-1  3- Basal infoldings: Invaginations of basal cell membrane. Forming compartments containing mitochondria. In ion transporting cells. Issue 1/ 1 Code: SOM1-1 2018  Apical specializations: microvilli, stereocilia, cilia & flagella. Lateral specializations: tight, adherent & gap junction, desmosomes and lateral interdigitations. Basal specializations: hemidesmosomes, basement membrane, basal infoldings. Issue 1/ 5 Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018  Test your knowledge In the small intestine and in epidermis of skin: 1- what is the type of epithelium? 2- What is the most suitable junction/s for that epithelium? Why? Issue 1/ 6 Code: SOM1-1 2018 Which type of membrane specialization? Code: SOM1-1 28 Issue 1/ Code: SOM1-1 2018 References Junqueira’s Basic Histology Text & Atlas Wheater's Functional Histology: A Text and Colour Atlas. www.histology-world.com www.bluehistology.com Issue 1/ 1 Code: SOM1-1 2018 Issue 1/ Code: SOM1-1 2018