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How are epithelial tissues classified and held together? 9/24 This lecture content will be on Test#2, not Mondays test #1 Chapter 5: 1) What is a tissue? 2) What is the embryonic pattern of development that creates different tissues? 3) How do we view the things we see with a microscope? 4) How are epithelial cells classified? 5) Four types lack stacking 1- Simple squamous ET characteristics 2- Simple cuboidal ET characteristics 3- Simple columnar ET characteristics 4- Pseudostartified ET characteristics 6) Four types have stacking Stacking gives a tissue special attributes Sign Up outside the AP lab for your special Lab Exam time for next Wed or Thur.only one time per person.

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How do we classify/describe the different cell types that make up tissues, organs, organ systems and the body? Tissue: a set of cells with similar appearance and function together in an organ. How do we consider tissues? 1) Embryonic Origin: what cells were the embryonic precursors? 2) Shape/Appearance: are cells round, flat or cube etc? 3) Things leaving cells: Secretion vs. Excretion: S: material has physiological function E: waste removal from cell/body 4) Activity: Do cells use contraction, exocytosis, endocytosis or phagocytosis? 5) Matrix: What extracellular material is observed around the cells? Collagen, Elastin, Cartillage, Interstitial Fluids These factors let us classify the tissue type! Tissues classification lets us understand the cause/effects of diseases.

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How does the angle of observation affect what we observe? Two dimensional interpretation of three dimensional objects can be very difficult. Terms used to describe orientation of tissue section: Longitudinal View vs. Cross Sectional View Oblique View: Mix of the two for cells/tissue Histological fixing and sectioning of tissue Object on Slide Histological Staining of tissue Colors on Slide Sometimes fixation removes a part of the original tissue and what is seen on the slide is the remnant of where the cell used to be. The color we observe on a slide is usually created by the stains the tissue was prepared with. Try to interpret what you see on a slide as what it was.

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What are our 3 Primary Germ Layers? Why are germ layers improtant? #1: Life begins as a fertilized egg (zygote; Week 1) that begins to divide. #2: Life progresses to a hollow ball of cells with a yolk sac underneath (blastoceol; Week 2) Outside surface=ectoderm Inside surface next to yolk sac= endoderm #3: Week2-3 The ball of cells forms a neural tube (CNS). Cells squeeze between the edges and migrate into the middle space between the yolk sac and the outside.

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How do the three primary germ layers create the four primary classes of tissue? 1) Ectoderm: Epithelial Tissues Becomes: epidermis, hair, glands of skin, nerves, brain, a few blood vessels, and spinal cord Basement membrane holds them to underlying base! 2) Endoderm: Epithelial Tissues Becomes lining of lungs and glands of the gut 3) Mesoderm: Middle Tissues Becomes: dermis of skin, muscle, blood and connective tissues Remember that cells can migrate in the body during embryonic development. These 3 germ layers create the 4 Primary Tissue Classes: 1) Epithelial 2) Connective 3) Nervous 4) Muscular

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The most fundamental way to organize epithelial cell classes is by layer and cellular shape (Know Table 5.2). Four types have a single epithelial cell layer: Simple Squamous Simple Cuboidal Simple Columnar Psuedostratified Columnar Four types have layered epithelial cells: Stratified Squamous 1)-with the protein keratin 2)-without the protein keratin 3)Stratified Cuboidal 4)Transitional Why is the basement membrane so important? This is cellular super-glue for all epithelial tissues! Why are underlying connective tissues required?

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Why is the shape of simple squamous epithelium important for its function? Where is SSE: alveoli, blood vessels, serous membrane of organs, glomerular capsule Key Characteristic: FLAT and THIN! Typical packing and desmosomes: Why do we need a smooth surface? Why do we need a thin barrier/membrane? Where does gas exchange occur? Why does filtration occur? SSE tissues lining all blood vessels consist of endothelial cells Additional Endothelial Functions: Hormonal functions- Contraction, inflammation and permeability- Clot Prevention-

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Simple cuboidal epithelium helps with: protection, secretion and reabsorption. Key characteristic: CUBE SHAPED! Tight packing: Desmosomes: Provides Glandular Functions (Secretions): ovary, salivary, thyroid, pancreas, and liver Kidney has dual functions: Absorption and Secretion-

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How do we protect cells and underlying tissues in places, such as the stomach? How do we prevent acids, abrasives, or pathogenic organisms from damaging underlying tissues? Simple Columnar Epithelium: Longer than they are wide to put nuclei by basement membrane for extra safety: Tough basement membrane: SCEs secrete digestive enzymes: SCEs help with nutrient absorption: Some have cilia (uterine tubes): Huge intestinal surface area with villi (cells) and microvilli (cell structures)= nutrient/water absorption Specialized Goblet cells make mucus to lubricate the passage of materials

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Pseudostratified Columnar Epithelium (PCE) has cilia that move materials embedded in mucus in a single direction. Why is it called pseudostratified? Nuclei are at several different levels in cell- All cells still reach basement membrane- It only appears multi-layered Goblet cells are important! Importance of cilia for the airways? Importance of cilia in male reproductive tract? Importance of basement membrane?

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Stratified Epithelial cells (Table 5.3) can be: 1) Squamous with keratin 2) Squamous without keratin, 3) Cuboidal or 4) Transitional. Callus on Sole of Foot: SSE-K...creates a nasty water insoluble place where bacteria cant live and water cant evaporate from the body!why? Mucosa of vagina, mouth, anus, esophogus are covered by: SSE-NoKwhy? Ovarian follicles and seminiferous tubules of the testes: SCEwhy? Transitional Epithelium: Lower urinary tract and part of umbilical cord- it stretches! Why transitional (partly rounded/partly flattened)? WHAT IS EPITHELIAL CELL EXFOLIATION? Do you treat the exfoliation on your scalp?

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The Eight Kinds of Epithelial Tissue: Describe the key features of each and where they are found in the body: Four Single Layer Epithelial Tissues: Simple Squamous Epithelial Simple Cuboidal Epithelial Simple Columnar Epithelial Pseudostratified Columnar Epithelial Four Layered Epithelial Tissues: Stratified Squamous Epithelium-Keratinized Stratified Squamous Epithelial-Nonkeratinized Stratified Cuboidal Epithelial Transitional Epithelial