TissuesTissues. No single cell… Although there are trillions of cells in the human body, there are...
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Transcript of TissuesTissues. No single cell… Although there are trillions of cells in the human body, there are...
![Page 1: TissuesTissues. No single cell… Although there are trillions of cells in the human body, there are only about 200 different types of cells Cells types.](https://reader035.fdocuments.in/reader035/viewer/2022062517/56649efc5503460f94c0f1c2/html5/thumbnails/1.jpg)
TissuesTissuesTissuesTissues
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No single cell…• Although there are trillions of cells in
the human body, there are only about 200 different types of cells
• Cells types combine to form tissues.– Collections of specialized cells and cell
products that perform a limited number of functions.
– Histology is the study of tissues
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4 basic tissue types• Epithelia
– Cover exposed surfaces – Line internal passages and chambers– Produce Glandular secretions
• Connective– Fill internal spaces– Provide structural support– Store Energy
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4 basic tissue types con’t.
• Muscle– Contracts to produce active
movement
• Neural– Conducts electrical impulses– Carries information
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From the outside in…• Epithelial tissue
– Epithelia (singular: epithelium) -- covers internal and external surfaces
– Glands – secreting cells derived from epithelia
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Key characteristics of Epithelia
• Bound closely together• A free (apical) surface is exposed to the
environment or internal space• Attached to other cells by basement
membrane• Avascular
– No blood vessels; cell must obtain nutrients across basement membrane
• Continually regenerated due to damage or loss
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Functions of Epithelia• Provide physical protection
– Against abrasion, dehydration or destructive agents
• Control permeability• Provide sensation
– Helps relay info to the nervous system
• Produce specialized secretions– Individual cells are called gland cells– Entire tissues are called glandular epithelium
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A note about secretions…
• If the secretions are discharged onto the surface of the epithelium, they are called exocrine– Ex. Milk, sweat, digestive enzymes
• If the secretions are released into the surrounding tissue fluid and blood, they are called endocrine– These are hormones; chemical
messengers
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Epithelial Surface• AKA Apical Surface• Can have specialized structures
– Microvilli• Small finger-like projections of the cell surface• Help increase surface area for absorption and
secretion of materials• Found in the digestive and urinary tracts
– Cilia• Short hair like structures• Found in the respiratory tract• Helps move mucus trapped irritants
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Classifying epithelia• Can be simple or stratified
– Simple = 1 layer of cells– Stratified = multiple layers
• 3 shapes– Squamous – flat like a fried egg– Cuboidal – like little hexagonol boxes– Columnar – like the cuboidal but taller
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Pictures of epithelia• Look at the hand outs of pages 94-
96 for the different types of epithelia, both simple and stratified.
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Connective TissuesConnective TissuesConnective TissuesConnective Tissues
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Connective Tissues• The most diverse tissues of the body• Made of 3 different components
– Specialized Cells– Protein Fibers– Fluid known as Ground Substance
• The protein fibers and ground substance combine to make up the matrix that surrounds the cells
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Connective Tissues• Never exposed to the outside
environment although they are throughout the body
• Highly vascularized• Contain receptors to pain,
pressure, temperature, and other sensations
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Special differences between epithelia and connective
tissues• Epithelial tissues are composed
mainly of cells• Connective tissues has a majority
of its volume consisting of the extra-cellular matrix
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Main uses of connective tissues
• Support & Protection– Help to establish a bony structural
framework
• Transport Materials– Fluid connective tissues are very
efficient at moving dissolved materials throughout the body
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Main uses of connective tissues
• Storage of Energy Reserves– Adipose cells store energy until
needed
• Defense of the Body– Respond to invaders of the body and
produce antibodies
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3 Major types of Connective Tissue
• Connective Tissue Proper– Ex. Tissue under the skin, fat,
tendons and ligaments– Has many types of cells and fibers in
a syrupy ground substance
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3 Major types of Connective Tissue
• Fluid Connective Tissue– Ex. Blood and Lymph– Has a distinctive cell population in a
watery ground substance with dissolved proteins
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3 Major types of Connective Tissue
• Supporting Connective Tissue– Ex. Cartilage and Bone– Less diverse cell population than CTP
but has a matrix of dense ground substance and closely packed fibers
– Bone is fiberous but calcified to provide rigidity and strength
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Lets look at the players…
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Connective Tissue Proper
• Major Cell Types– Fibroblasts– Macrophages– Fat cells (adipocytes)– Mast Cells
• Also can include stem cells and cells that produce antibodies
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Connective Tissue Proper
• Connective Tissue Fibers– Collagen – long, straight, and
unbranched strong and flexible– Elastic – Contain the protein elastin,
they are branched and wavy– Reticular – Least common and form a
woven branching framework
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Connective Tissue Proper
• Ground Substance– Should be clear and colorless– Consistency of maple syrup
• Density helps slow bacteria and makes it easier for macrophages to consume them
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Connective Tissue Proper
• Classified as either Loose or Dense• Loose
– Areolar• Least differentiated, contains all of the
cells of CTP• Forms a layer that separates skin from
underlying muscle– Why you can pinch skin without distorting the
muscle
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Connective Tissue Proper
• Loose con’t.– Adipose Tissue (Fat)
• Very similar to Areolar Tissue, just has a majority of adipocytes
• Found under the skin on the sides, buttocks and breasts
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Connective Tissue Proper
• Dense Connective Tissue– Mainly collagen fibers– Tendons – connect skeletal muscle to
bone– Ligaments – Connect bone to bone
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Fluid Connective Tissue• Blood
– Watery matrix called plasma– Mostly Red Blood Cells (RBC’s)– Some White Blood Cell– Platelets
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How Fluid Connective Tissues Work Together
• Plasma is in constant motion in the blood vessels due to contractions of the heart
• When it gets to capillaries, solutes will dissolve into interstitial fluid (fluid surrounding body cells)
• As interstitial fluid enters lymphatic vessels, lymph forms– Combines cells of the immune system to monitor the body
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Supporting Connective Tissue
• Cartilage– Firm gel matrix containing only
chondrocytes– Avascular – why it is difficult to repair– Separated from other tissues by the
perichondrium
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3 types of Cartilage• Hyaline
– Tough by flexible, connects ribs to sternum, covers bone surfaces in joints
• Elastic– Very resilient and flexible, found in the outer ear
flap and epiglottis
• Fibrocartilage– Very little ground substance, mostly collagen fibers– Found between vertebrae, connecting bones in the
pelvis
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• Bones will be covered in the skeletal unit!