ANA LEC - LE 1 01 - The Cell, Epithelium, and Glands PDF

ANATOMY | TRANS 1 LE The Cell, Epithelium, and Glands...

ANATOMY | TRANS 1 LE The Cell, Epithelium, and Glands MELISSA C. CALILAO, MD, DPPS, DPSA | 08/14/2023 01 OUTLINE → Contains organelles that are essential to its maintenance I. The Cell A. General Overview V. General Classification of Epithelia → Each type of cell can be specialized to form specific functions but share many common organizational features 📋 II. B. Cell Division The Epithelium A. Lining Epithelia B. Secretory Epithelia out a specific function forms a tissue → Cytology is the study of cells 📖 → A group of similar cells and their extracellular matrix that carry A. Overview of Epithelial VI. Histogenesis of the → Histology is the study of tissues Tissue Epithelium → Organology is the study of organs - a group of tissues with B. Functions of Epithelial VII. Epithelial Cell Renewal specific function Tissue VIII. Review Questions ▪ organs may form part of the systems in the body to perform C. Characteristics of IX. References complex tasks Epithelial Cells X. Appendix → Electron and optical or light microscopy - two most frequently III. Junctional Complexes used methods in the study of cells and tissues A. Cell-to-Cell Adhesions B. Cell-to-Extracellular Matrix Junction IV. Apical Surface Modifications A. Flagella B. Cilia C. Stereocilia D. Microvilli ❗️ Must know 💬 Lecturer 📖 Book 📋 Previous Trans SUMMARY OF ABBREVIATIONS ECM Extracellular matrix G1 Gap 1 G2 Gap 2 M-phase Mitotic phase S-phase Synthesis phase LEARNING OBJECTIVES ✔ To demonstrate knowledge and understanding of the cell by identifying and correlating cell organelles with their functions in Figure 2. A side-by-side comparison of electron micrograph and both light microscopy and in electron micrographs what is seen during light microscopy [Indiana University Virtual Microscopy Library] ✔ To be able to identify the specific type of epithelial tissue by its characteristics, morphology, and function → Staining is important in both types of microscopy - in optical ✔ To demonstrate knowledge of the different surface modifications microscopy especially, stains enhance visualization of the cell of epithelial tissue or certain cellular components To demonstrate ability to distinguish between types of covering 📋 ✔ → Aside from colouration, the following observation should be epithelial tissue by identifying its morphology and functions made in examining a variety of cell types) ✔ To enumerate and distinguish the different types of glandular ▪ Shape of the cell epithelia based on morphology, mechanism of the product of ▪ Size of the cell release and type of secretion ▪ Shape, size, and position of the nucleus I. THE CELL ▪ Identification of nucleolus if present in the nucleus A. GENERAL OVERVIEW OF THE CELL → Certain organelles may also be useful in the characterization of Cell samples being viewed → Basic unit of life B. THE CELL CYCLE A series of stages in which the cell divides and produces daughter cells. It is divided into two main phases, the growth and DNA replication phase (interphase) followed by the M-phase, a collective term for both the division of the nucleus (mitosis) and cytoplasm (cytokinesis) → The interphase isn’t readily visible through light microscopy but it lasts longer than the M-phase and is mostly made up of three substages: ▪ S-phase - the period where nuclear material is synthesized ▪ G1 - the gap between M-phase and S-phase when the cell grows physically and increases the volume of both protein and organelles. ▪ G2 - the gap between S-phase and M-phase when the cell gets ready for cell division → The M-phase is the freely observable part of the cell cycle and Figure 1. A composite general illustration of the cell showing is made up of two stages organelles [Eroschenko & DiFiore] LE 1 TG 24 | M. Abcede, K. Acharon, G. Advincula, F. Batol, TE | M. Abcede, G. Advincula AVPAA | B. Alcid. C. PAGE 1 of 16 TRANS 1 J. Bauzon, J. Bertillo, C. Bisa, G. Buenaventura Cabuyao, C. Cambas ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA ▪ Mitosis refers to the division of nuclear material particularly DNA II. THE EPITHELIUM ▪ Cytokinesis refers to the division of the cytoplasm A. OVERVIEW OF EPITHELIAL TISSUE CASE SCENARIO A 58 y/o female came in for consultation due to multiple, painful skin erosions all over the body of 2 months duration. She also noted blisters of the oral mucosa which started 5 months prior to consultation. On physical examination, there was a note of blisters and painful erosions over the back, left arm and chest areas. → Ruptured painful blisters: back area, skin, portion of lower lip Figure 3. A diagrammatic illustration and in vivo view of the mitotic stages [NCBI] → Possible complication arises: infection, a route for microorganisms to invade skin that is left untreated.💬 Tissue in Histology - group of cells that perform specific function → Phases of mitosis: Basic Types of Tissues: ▪ Prophase is the stage of mitosis during which the → Epithelium: lining of body surface (outer & inner) or cavities; chromosomes become visible, the cell nucleus starts to lose glandular secretion its identity, the spindle apparatus appears, and the ▪ Made up of aggregated polyhedral cells centrioles migrate toward opposite poles ▪ Has small amount of extracellular matrix (ECM) ▪ Metaphase is the stage of mitosis at which chromosomes → Muscle are firmly attached to the mitotic spindle at its equator but ▪ Strong contraction; body movements have not yet segregated toward opposite poles ▪ Moderate amount of ECM ▪ Anaphase is the stage of mitosis during which the two sets ▪ Elongated contractile cells of chromosomes separate and move away from each other → Nervous − It is composed of anaphase A (chromosomes move ▪ Transmission of nerve impulses toward the two spindle poles) and anaphase B (spindle ▪ Very small amount of (ECM) poles move apart) ▪ Elongated cells with extremely fine processes ▪ Telophase is the stage in mitosis in which two daughter → Connective nuclei are formed, the cytoplasm completes division, and ▪ Support and protection of tissues/organs the chromosomes lose their distinctness and are ▪ Abundant amount of (ECM) transformed into chromatin threads → Meiosis is a type of cell division that results in haploid daughter cells and occurs mainly in the germ cells as opposed to somatic cells which undergoes mitosis Table 2. Comparison of Mitosis and Meiosis TYPE MITOSIS MEIOSIS Function Growth; cellular Sexual proliferation reproduction Cell types Somatic cells Germ cells involved Number of 1 cell division 2 cell divisions divisions (Meiosis I & II) Synapsis or Absent Present Figure 4. Diagrammatic Image Showing Typical Epithelium [Junqueira] pairing of (occurs during homologous prophase I) chromosomes Crossing over or Absent Present chiasma formation Number of 2 daughter cells 4 daughter cells daughter cells produced Identicalness or Daughter cells are Daughter cells are comparison completely identical not identical between daughter cells Chromosome Diploid (2n=46) Haploid (n=23) number of Figure 5. Photomicrograph of the Lining of the Small Intestine daughter cells Under HPO [Dr. Calilao’s Lecture Slides] LE 1 The Cell, Epithelium, and Glands PAGE 2 of 16 TRANS 1 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA B. FUNCTIONS OF THE EPITHELIAL TISSUE Protection and Barrier → E.g., skin, oral mucosa Absorption → E.g., small intestine absorbs nutrients & water Secretion → E.g., digestive enzymes (intestinal epithelium), mucus (respiratory epithelium) Lubrication: prevents friction → E.g., small amounts of tissue fluid secreted by the mesothelium (outermost covering of abdominal organs) Reproduction → E.g., linings of male & female reproductive tracts Transport 📋 → E.g., allows small molecules & ions to pass through in → either direction C. CHARACTERISTICS OF THE EPITHELIAL TISSUE Avascular → No blood vessels Figure 7. Section of the Kidney (Glomerulus). Basement membrane → Nutrients and oxygen are acquired via diffusion from the (Black arrow) neighboring blood vessels located in ECM & connective tissue Exhibits polarity (several domains with specific, varying characteristics) → Apical pole: Faces the opposite space (usually lumen) → Basal pole: In contact with ECM and connective tissue → Lateral pole/surface: In contact with adjacent cells Figure 8. Basal and reticular laminae of basement membranes Basal Lamina is different from Basal Membrane Basal Lamina is a component of basement membrane and can only be seen ultrastructurally Basement Membrane can be seen via simple or light microscopy Presence of Junctional Complexes or Cell Junctions → Main intermediate filament : KERATIN Figure 6. Special Characteristics of Epithelium 💬 III. JUNCTIONAL COMPLEXES A. CELL-TO-CELL JUNCTIONS OCCLUDING OR TIGHT JUNCTION Presence of basement membrane → Thin extracellular sheet of macromolecules Also known as Zonula Occludens → All epithelia (basal portions) lie on a basement membrane “Zonula” means encircle the entire cell → All nutrients and oxygen need to pass through the basement Transmembrane proteins: Claudin and Occludin membrane Found in the most apical portion of the cell → Functions: Importance of tight junctions: Molecules that cross the epithelium ▪ Acts as a filter (e.g., renal glomeruli) would pass the cell via transcellular pathway (vs. paracellular ▪ Epithelial repair and regeneration (e.g., stem cells); acts as pathway) the scaffolding to rebuild on after injury) * Zonula “Occludin/Oclaudin” (Mnemonic) ▪ Important in maintaining cellular functions (e..g endocytosis, signal transduction, cell-to-cell interactions, polarity, etc.) MEDICAL CORRELATION ▪ Provides structural support for epithelial cells Bacterial food poisoning by Clostridium perfringens ▪ Attach epithelia to underlying connective tissue → Elaborates an enterotoxin that binds to claudin → Made up of two components: → When Clostridium perfringens enterotoxin binds to claudin, ▪ Basal lamina: Electron-dense, closest to the basal portion causing faulty junctions, which result to leaks that pass via of the cell, made-up of Type IV collagen paracellular pathway ▪ Reticular lamina: More diffuse, fibrous, made-up of Type III Gastric ulcers by Helicobacter pylori collagen → Binds the extracellular domains of tight-junction proteins in 📋 cells of the stomach and inserts a protein into these cells, disrupting the signaling from the junction LE 1 The Cell, Epithelium, and Glands PAGE 3 of 16 TRANS 1 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA ANCHORING JUNCTIONS → Importance of Hemidesmosome: anchor cells at the basal ADHERENS JUNCTION portion Also known as Zonula Adherens → Transmembrane proteins: Cadherin and Catenin MEDICAL CORRELATION: EPIDERMOLYSIS BULLOSA ▪ Cadherin is calcium requiring Rare condition → Located below the tight junctions Causes blisters even with minimal friction → Importance of anchoring junctions: it anchors the cell closely to Usually results in severe pain due to exposure of raw areas the neighboring cells (skin) Patients are prone to having infections * Zonula (C)Adherens (For easier memorization) FOCAL ADHESIONS DESMOSOME Transmembrane proteins: Integrin Also known as Macula Adherens (Macula: adhering spot) → Integrin form cross-links with actin filaments → Transmembrane proteins: Desmoglein and Desmocollins More numerous and smaller than hemidesmosome → No “Zonula” in the name = it does not form a band around the Importance of Focal adhesion: anchor cells at basal portion cell, but appears as spot-weld → Focal adhesion kinase: signaling molecule (protein) that → Disc shaped structures that are located in one cell and is initiates intracellular protein phosphorylation affecting cell matched together with a similar structure on the lateral surface of the adjacent cell → Importance: provides stability to cells that are subjected to to laminin (or other specific proteins) 📋 division, mobility, and gene expression upon binding of integrin shearing stress IV. APICAL SURFACE MODIFICATIONS → Faulty desmosome function is correlated with various blistering skin conditions A. FLAGELLA * Desmo- “(Collin)/(Glein)” (sounds-alike) Long, whip-like, singular membrane extension supported by microtubule related to sperm cells MEDICAL CORRELATION: PEMPHIGUS VULGARIS It is mainly made up of microtubules with a similar cross-sectional Faulty desmosome function can cause blistering of the skin and structure as the cilia the oral mucosa. This dysfunction is caused by autoimmune Function: propulsion for the sperm cell during the fertilization reactions against specific desmogleins in the desmosome. process GAP/COMMUNICATING JUNCTIONS Also known as Nexus Transmembrane protein: Connexin → 6 connexin = 1 connexon The gaps (channels) are formed by paired connexons (in between cells) Appear as openings Allows small molecules and nutrients to pass selectively between cells → Uses selective diffusion (molecules must be Striated Ducts -> Intralobular ** -> Interlobular Ducts → **Some books state that the secretions travel from the striated duct then into the intralobular duct, others state that Figure 29. Myoepithelial Cells it goes into the interlobular directly → Cells increase in height and complexity as it reaches the Mixed Mucous/Serous surface (s. cuboidal -> columnar -> pseudostratified → Mixed, can be predominantly mucous or serous columnar -> stratified columnar) LE 1 The Cell, Epithelium, and Glands PAGE 9 of 16 TRANS 1 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA Figure 31. Mixed Gland Figure 35. Overview of the Structural Classes of Simple Glands → Simple Tubular ▪ Elongated secretory portion + short/absent duct ▪ Examples: mucous glands of the colon, intestinal glands/ Crypts of Lieberkuhn Figure 32. Intercalated and Striated Ducts Pink arrow: Mucous cells Black arrow: Intercalated duct Yellow circle: Striated duct Green circle: Acinus (composed of serous cells) Figure 36. Simple Tubular Gland Purple arrow: Granular and basophilic cytoplasm → Simple Branched Tubular ▪ Several long secretory parts joining to drain into 1 duct ▪ Example: Glands in stomach and uterus Figure 33. Interlobular Duct Interlobular ducts (lined by pseudostratified columnar epithelium on the left) are surrounded by connective tissues Figure 37. Simple Branched Tubular Gland → Simple Coiled Tubular ▪ 1 duct + very long and coiled secretory portion ▪ Example: Sweat glands Figure 34. Parotid Gland Based on type of secretion: Purely Serous Gland White/Clear areas: adipose tissue BASED ON MORPHOLOGY Figure 38. Simple Coiled Tubular Gland Simple glands: ducts that do not branch; one duct (e.g., sweat glands) → Simple Acinar/Alveolar ▪ 1 duct + rounded, saclike secretory portion LE 1 The Cell, Epithelium, and Glands PAGE 10 of TRANS 1 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA ▪ Example: Small mucous glands along the urethra BASED ON MECHANISM OF PRODUCT RELEASE OR → Simple Branched Acinar GLAND-CELL PARTICIPATION ▪ 1 duct + multiple sac-like secretory portion ▪ Example: Sebaceous gland Compound Figure 42. Different Types of Glands Merocrine (Eccrine) gland Figure 39. Overview of the Structural Classes of Compound Glands → The most common type of glands (based on gland-cell participation) → Compound Tubular → Secretions are released or brought to the duct via exocytosis ▪ Several ducts + several elongated tube-like secretory (through the secretory vesicles) portions → Example: Salivary gland ▪ Example: Submucosal glands (of Brunner) in the duodenum → Compound Acinar/Alveolar ▪ Several rounded, sac-like secretory portions converge into a smaller duct and would drain into a large duct ▪ Example: Exocrine pancreas, mammary gland Figure 43. Merocrine Sweat Gland Holocrine Gland → Secretory portions become part of the secretion (sacrificed and Figure 40. Compound Acinar Gland formed part of the secretion) → Undergoes apoptosis (i.e. cell death) → Compound Tubuloacinar → Example: Sebaceous glands ▪ The secretory portions both have acinar and tubular units ▪ Several tubular and sac-like secretory portions + several ducts ▪ Example: Salivary glands Figure 41. Compound Tubuloacinar Glands Figure 44. Sebaceous Gland Apocrine Gland → Part of the apical surface of the cell is pinched or released with the secretion of the gland → Example: Mammary gland LE 1 The Cell, Epithelium, and Glands PAGE 11 of TRANS 1 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA b. Pseudostratified c. Simple squamous d. Transitional 3. Which of the following special structures can be found in the basal surface of epithelial tissue? a. Microvilli b. Desmosomes c. Hemidesmosomes 4. In observing epithelial cells under a microscope, the cells are arranged in a single layer and look tall and narrow, and the nucleus is located close to the basal side of the cell. The specimen is what type of epithelial tissue? a. Transitional epithelium b. Columnar epithelium c. Squamous epithelium Figure 45. Mammary Gland 5. The ________ exocrine gland stores its secretion until the glandular cell ruptures, whereas the ________ gland releases Paracrine Gland → Effect of secretion is on the neighboring cells 📋 its apical region and reforms. a. Eccrine; endocrine b. Eccrine; apocrine VI. HISTOGENESIS OF EPITHELIUM c. Apocrine; holocrine Table 3. Histogenesis of Epithelium d. Holocrine; apocrine HISTOGENESIS OF THE EPITHELIUM Ectodermal Epidermis 6. Which of the following proteins is found in the zonula Derivatives Cornea, lens epithelia adherens? Components of the inner ear a. Cadherin and Catenin Adenohypophysis b. Desmoglein and Desmocollins Mesodermal Epithelium of kidney and glands c. Claudin and Occludin Derivatives Mesothelium d. Connexin Endothelium Adrenal cortex 7. An epithelial tissue having thin flat and closely packed cells Seminiferous and genital duct epithelium that are arranged edge to edge is found in Endodermal Respiratory system epithelium a. the inner lining of cheeks Derivatives Alimentary canal epithelium b. the inner lining of the small intestine Extramural digestive gland epithelium c. the inner lining of the fallopian tube Thyroid, parathyroid, and thymus glands epithelial components 8. Identify pointed structure/s Lining epithelium of the tympanic cavity and eustachian tube VII. EPITHELIAL CELL RENEWAL As the epithelium is living tissue, it is constantly exposed to harmful and potentially damaging conditions: → The cells need to self-renew continuously through mitosis and stem cell populations → The epithelium is highly-regenerative; capable of rapid repair and replacement of damaged/worn out cells The rate of renewal varies: → Small intestine (simple columnar epithelium): 4-6 days ▪ Faster rate of renewal in the simple columnar epithelium (lesser number of layers) 9. Classify pointed tissue. Be specific. → Epidermis (stratified squamous keratinized epithelium): 28 days ▪ In stratified epithelial tissues, stem cells and mitosis occur only within the basal layer in contact with the basal lamina More layers = More time needed for the renewal of cells and vice-versa ↑ number of layer = ↓ rate of renewal (slower) VIII. REVIEW QUESTIONS 1. Which of the following is not a characteristic of epithelial tissue? a. Avascularity b. Polarity c. Excitability 2. Which of the following is the epithelial tissue that lines the interior of blood vessels? a. Columnar LE 1 The Cell, Epithelium, and Glands PAGE 12 of TRANS 1 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA 10. Classify bracketed tissue completely. 15. Classify according to morphology 11. Classify bracketed tissue. ANS: 1. The answer is C since all types of epithelia are supplied through diffusion rather than blood vessels. Epithelia are also polar with definitive poles (apical, lateral, and basal poles). Excitability is a characteristic of both muscular and nervous tissues 2. The answer is C since simple squamous epithelium provides a smooth surface for the blood to "slide past." The tunica intima layer is continuous with the endocardium, makes up the capillaries, and is collectively referred to as the endothelium. Additionally, this type of epithelium allows the easy passage of fluid and migratory white blood cells into and out of the vessel 3. The answer is C since microvilli can only be found on the apical surface while desmosomes can only be found on the lateral surface. 4. The answer is B since only columnar epithelium fits the description of ‘tall, narrow, and the nucleus is located at the basal portion’ 5. The answer is D. 6. The answer is A since desmoglein and desmocollin are both found in the 12. Classify bracketed tissue. macula adherens, claudin and occludin in the zonula occludens, and connexin is found in the gap junctions. 7. The answer is A since for all the other options to be true, the question must’ve mentioned the presence of specialized structures like cilia or microvilli in the apical surface of the cells indicated. since the only indication given is ‘thin flat and closely packed cells’, then only option A fits the description. 8. Blue arrow: cilia; Yellow arrow: basement membrane 9. Simple squamous epithelium 10. Pseudostratified ciliated epithelium with goblet cells 11. Transitional epithelium (relaxed) 12. Stratified squamous epithelium wet type/non-keratinized 13. Stratified squamous epithelium dry type/keratinized 14. Simple cuboidal epithelium with microvilli/brush border/striated border 15. Simple tubular gland 13. Classify bracketed tissue IX. REFERENCES 2025 (2021). The Cell, Epithelium & Glands. [Transcription] Calilao, M.C. (2021). The Cell, Epithelium & Glands. [Asynchronous Lecture] Eroschenko V. P. & Fiore M. S. H. di. (2013). Di fiore's atlas of histology with functional correlations (12th ed.). Wolters Kluwer / Lippincott Williams & Wilkins. Mescher A. L. (2013). Junqueira's basic histology : text and atlas (Thirteenth). McGraw Hill Medical. Ovalle W. K. Nahirney P. C. & Netter F. H. (2008). Netter's essential histology. Saunders/Elsevier. Young, B., Woodford, P., & O’Dowd, G. (2013). Wheater’s functional histology (6th ed.). Churchill Livingstone. Indiana State University Virtual Microscopy Laboratory 14. Classify bracketed tissue https://vmicro.iusm.iu.edu/hs_vm/docs/stn5b.htm Asynchronous Recordings: LE 1 The Cell, Epithelium, and Glands PAGE 13 of TRANS 1 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA X. APPENDIX APPENDIX **lines the ducts of glands or organs LE 1 TG 24 | M. Abcede, K. Acharon, G. Advincula, F. Batol, TE | M. Abcede, G. Advincula AVPAA | B. Alcid. C. PAGE 14 of TRANS 1 J. Bauzon, J. Bertillo, C. Bisa, G. Buenaventura Cabuyao, C. Cambas 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA LE 1 The Cell, Epithelium, and Glands PAGE 15 of TRANS 1 16 ANATOMY | LE 1 The Cell, Epithelium, and Glands | Melissa C. Calilao, MD, DPPS, DPSA LE 1 The Cell, Epithelium, and Glands PAGE 16 of TRANS 1 16