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4 Tissue: The Living Fabric: Part A
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Hierarchy of the body CELLS: the smallest living building blocks in the body. TISSUES: groups of similar cells that join together for a particular function ORGANS: groups of tissues that join together for a particular function
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Cells are the living building blocks of the body
Cells come in many shapes and sizes Cells are ALIVE
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Cells group together to form TISSUES
Which two tissues are the same? Why?
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Cells + stuff the cells secrete
Tissues Cells or Cells + stuff the cells secrete cell Protein fiber fluid, gel, mineral outside cell
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Four major tissue categories by function
Nervous tissue Muscle tissue Epithelial tissue Connective tissue Figure 4.1
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24 specific tissue types, how many in each category?
MT= MUSCLE TISSUE ET= EPITHELIAL TISSUE CT= CONNECTIVE TISSUE *very uncommon, no images shown in class
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How does the body make all these tissues?
egg + You! As one cell! sperm THREE EMBRYONIC TISSUES Ectoderm (becomes NT, ET) Mesoderm (becomes MT, CT, ET) Endoderm (becomes ET) You divide and form many copies of one cell type Differentiation During your development, your cells change into three embryonic tissues
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Where did your adult tissues come from? Make a chart!
Mesoderm Endoderm 16-day-old embryo (dorsal surface view) Epithelial Tissue Nervous tissue (from ectoderm) Muscle and connective tissue (mostly from mesoderm) Ectoderm Where did your adult tissues come from? Make a chart! Major tissue type Derived from which embryonic tissue(s)? CT ET MT NT
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What are the three embryonic tissues?
What are the 4 main tissue groups? Name all the tissues! Just kidding, we’ll teach you those. In other words the first THREE tissues you had ….formed -the 4 tissue groups and all 24 tissues you have now.
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Sounds boring. Why should I know about tissues?
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Which is normal and which is pathological?
Fatty Liver Histology Normal Liver Histology You have to learn “normal” first
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SIX STEPS of TISSUE PREPARATION
1. Biopsy (remove) a small bit of tissue from the patient 2. Fix the tissue in a preservative so that it hardens, and does not rot 3. Section the skin into thin slices 4. Mount sections on glass slides Cervix biopsy Cervix biopsy 5. Stain the tissue sections to make it easier to see them under the microscope 6. Coverslip the tissue sections
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Familiar structures can look different when viewed as a single slice… An egg will not necessarily look like an egg.
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Characteristics of Epithelial Tissue
closely packed cells basal (bottom) surface sits on basement membrane of gooey glycoprotein held together by desmosome junctions (snap) and tight junctions (ziplock) avascular (no blood vessels) multiply rapidly apical (top) surface may have cilia or microvilli, depending on tissue ET is superficial to a connective tissue
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LOCATIONS OF EPITHELIAL TISSUES IN THE BODY
Some cover hollow organs (intestine, bladder, heart) Superficial ET covering of skin Line organs Lower layer of skin Some ET form glands Ex. these tissues secrete sweat, oil, milk, or hormones
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How do you name the Epithelial tissues?
1. How many layers does it have? Figure 4.2a Stratified Simple Apical surface Basal surface (a) Classification based on number of cell layers.
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How do you name the Epithelial tissues?
2. What are the shapes of the cells? Figure 4.2b Squamous Cuboidal Columnar (b) Classification based on cell shape.
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Put the two names together into Epithelial Tissues (8 kinds)
Simple squamous ET Simple cuboidal ET Simple columnar ET Pseudostratified columnar ET Stratified squamous ET Stratified cuboidal ET Stratified columnar ET Transitional ET Simple arrangement of cells Stratified arrangement of cells
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Overview of Epithelial Tissues
For each of the following types of epithelia, you must learn To recognize the tissue Full tissue name Cell names Locations in the body Functions in the body
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(a) Simple squamous epithelium
Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Air sacs of lung tissue Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae. Nuclei of squamous epithelial cells Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae). Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (125x). Figure 4.3a
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Simple Squamous Epithelial Tissue
Location here: lining air pockets in lungs Other places: lining blood vessels, covering organs Cells: squamous epithelial cells Function: a thin cell for gas diffusion, a slippery smooth surface LOOK FOR: a very thin layer of cells covering or lining something.
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Simple Squamous epithelial tissue…………..
is called Endothelium when found lining of blood vessels and heart is called Mesothelium when found lining the inside of the body wall
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(b) Simple cuboidal epithelium
Description: Single layer of cubelike cells with large, spherical central nuclei. Simple cuboidal epithelial cells Function: Secretion and absorption. Basement membrane Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface. Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (430x). Figure 4.3b
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Simple cuboidal epithelial tissue, covers thyroid gland follicle
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Simple Cuboidal Epithelial Tissue
Locations here: ducts in kidney and of follicles of thyroid. Cells: cuboidal epithelial cells Function: Absorbs and secretes fluids LOOK FOR: a single layer of cube shaped cells making up part of an organ.
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(c) Simple columnar epithelium
Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus- secreting unicellular glands (goblet cells). Simple columnar epithelial cell Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus. Basement membrane Photomicrograph: Simple columnar epithelium of the stomach mucosa (860X). Figure 4.3c
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Simple Columnar Epithelial Tissue
Location here: lines intestine Cells: columnar epithelial cells, goblet cells Function: absorbs nutrients Specializations: microvilli LOOK FOR: a single layer of column shaped cells on a wavy surface.
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(d) Pseudostratified columnar epithelium
Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus- secreting cells and bear cilia. Cilia Mucus of mucous cell Pseudo- stratified epithelial layer Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action. Location: Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract. Basement membrane Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (570x). Trachea Figure 4.3d
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Pseudostratified columnar epithelial tissue
Location: lines trachea (windpipe) Cells: columnar epithelial cells, goblet clles Function: moves mucous with cilia, makes mucous Cell specializations: cilia LOOK FOR: what looks like a double layer of column shaped cells with a fringed edge.
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(e) Stratified squamous epithelium
Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Stratified squamous epithelium Function: Protects underlying tissues in areas subjected to abrasion. Nuclei Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. Basement membrane Connective tissue Photomicrograph: Stratified squamous epithelium lining the esophagus (285x). Figure 4.3e
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Stratified Squamous Epithelial Tissue
Location here: lining esophagus Function: covering and lining entrances to body to resist pathogens and abrasion Cells: squamous epithelial cells Specializations: desmosomes, tight junctions, keratin LOOK FOR: many layers of cells
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Stratified Cuboidal Epithelial Tissue
Sweat gland Cuboidal epithelial cells 33
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Stratified Cuboidal Epithelial Tissue
Location here: forming sweat glands in skin Function: secretes sweat onto skin surface Cells: cuboidal epithelial cells (blue cubes) arranged in circle they become a sweat gland. (red circle) LOOK FOR: the round sweat glands with more than one layer of cube shaped cells.
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Stratified Columnar epithelial tissue
Cells: columnar epithelial cells Location: lining pharynx, male urethra NO IMAGE
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(f) Transitional epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch. Transitional epithelium Function: Stretches readily and permits distension of urinary organ by contained urine. Location: Lines the ureters, urinary bladder, and part of the urethra. Basement membrane Connective tissue Photomicrograph: Transitional epithelium lining the urinary bladder, relaxed state (360X); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine. Figure 4.3f
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Transitional Epithelial Tissue
Location here: lining bladder Function: allows stretching, cells slide over each other as bladder stretches, slide back as bladder empties Cells: transitional epithelial cells arranged in layers. Transitional “between, known shapes” ….kind of round. LOOK FOR: layers of roundish cells
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Compound duct structure
Other Epithelial cells make tissues that form glands! The glands are like small organs that release oil, milk, sweat, saliva. Don’t memorize, just marvel at the variability of gland structure. Figure 4.5 Compound duct structure (duct branches) Simple tubular Example Intestinal glands Simple branched tubular Stomach (gastric) glands Compound tubular Duodenal glands of small intestine Compound alveolar Mammary glands Simple alveolar No important example in humans Sebaceous (oil) Compound tubuloalveolar Salivary glands Tubular secretory structure Alveolar Surface epithelium Duct Secretory epithelium Simple duct structure (duct does not branch)
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ET cells that form Exocrine glands MAKE and RELEASE a product into a duct
Merocrine glands are a type of exocrine gland that use exocytosis to release their product into a duct EXOCRINE GLANDS Merocrine Glands examples: sweat or saliva Holocrine glands
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EXOCRINE GLANDS Merocrine glands Holocrine glands are a type of exocrine gland where the cells rupture, releasing secretions and dead cell fragments onto the skin surface. Holocrine Glands Example: oil (sebaceous) Secretory vesicles
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Microvilli Secretory vesicles containing mucin Rough ER Golgi
A single Goblet cell is an epithelial cell considered an exocrine gland, and uses exocytosis to release MUCIN + WATER = MUCOUS Microvilli Secretory vesicles containing mucin Rough ER Golgi apparatus Nucleus (a) (b) Figure 4.4
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Endocrine glands are also made of ET.
Endocrine gland cells release their product directly into the blood (adrenal glands, thyroid gland). That’s why you react to fear so quickly!
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Test your understanding:
A many-layered epithelium with cuboidal basal cells and flat cells at its surface would be classified as ________. A) simple cuboidal B) simple squamous C) transitional D) stratified squamous
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Test your understanding:
Select the correct statement regarding epithelia. A) Simple epithelia form impermeable barriers. B) Stratified epithelia are tall, narrow cells. C) Stratified epithelia are present where protection from abrasion is important. D) Pseudostratified epithelia consist of at least two layers of cells stacked on top of one another.
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Test your understanding:
Which of the following is true about epithelia? A) Simple epithelia are commonly found in areas of high abrasion. B) Stratified epithelia are associated with filtration. C) Endothelium provides a slick surface lining all hollow cardiovascular organs. D) Pseudostratified epithelia are commonly keratinized.
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