TISSUES
TISSUES Collection of cells with similar structure and function the study of tissues is known as histology four types of tissue
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epithelial (covering) connective (support) muscle (movement) nervous (control)
EPITHELIAL TISSUE Covers the surface of the body; lines body cavities; constitutes the bulk of most glands
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Functions:
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– physical protection – secretion – sensory reception – absorption – filtration
EPITHELIAL TISSUE ●
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‘SHEETS’ OF CLOSE PACKED CELLS WITH LITTLE EXTRACELULAR MATERIAL AVASCULAR: (GETS NUTRIENTS THROUGH DIFFUSION FROM UNDERLYING CAPILLARIES) INNERVATED MAINTAINS THE CAPACITY TO EASILY REGENERATE (WHY IS THIS IMPORTANT?)
EPITHELIAL TISSUE ●
POLARITY: ●
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THE NUCLEUS AND ORGANELLES ARE USUALLY UNEVENLY DISTRIBUTED, SO THERE IS AN ‘UP’ AND ‘DOWN’ SIDE ‘UP’ SIDE IS ALWAYS A FREE SURFACE, AND IS CALLED THE APICAL SURFACE THE DOWN SIDE IS THE BASAL SURFACE
ALWAYS SUPPORTED BY A LAYER OF CONNECTIVE TISSUE AT IT’S BASAL SURFACE (BASEMENT MEMBRANE)
EPITHELIAL TISSUE ●
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May contain microvilli: (fingerlike extensions of plasma membrane which increase the surface area for increased absorption/ secretion) May contain cilia: (larger extensions used for propelling substances)
EPITHELIAL TISSUE CLASSIFICATION ●
CLASSIFIED BY # OF LAYERS AND SHAPE ●
LAYERS: – –
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SHAPE: – – –
SIMPLE (SINGLE LAYER) STRATIFIED (MULTIPLE LAYERS) SQUAMOUS CUBOIDAL COLUMNAR
SIMPLE EPITHELIUM ●
Simple squamous: ● ●
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thin, permeable exchange of substances alveoli in lungs; lines blood vessels (WHY?)
Simple Epithelium ●
Simple cuboidal: ●
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secretion and absorption glands/ ducts; part of kidney tubules
SIMPLE EPITHELIUM ●
Simple columnar: ●
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secretion and absorption lines digestive tract (stomach to rectum): contains microvilli (why?) lines trachea: contains cilia (why?)
SIMPLE EPITHELIUM ●
Pseudostratified epithelium: ● protection and secretion ● nuclei position and cell height are staggered so appears stratified ● all cells in contact with basement membrane ● contains cilia ● lines upper
STRATIFIED EPITHELIUM ●
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Stratified squamous: ● physical protection against abrasion; pathogens; and chemicals ● esophagus, mouth, vagina, epidermis Transitional: ● lines only urinary bladder, ureters, urethra ● able to stretch
GLANDULAR EPITHELIUM ●
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Gland = cell or organ that secretes something for use inside or outside of the body Two types – endocrine: ex. thyroid – exocrine: ex. sweat
EXOCRINE GLANDS ●
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Secrete into ducts which lead to the body surface, or a body cavity which is continuous with a surface Unicellular: – goblet cell: produces mucus (intestine, respiratory tract) Multicellular: ● merocrine ● holocrine
EXOCRINE GLANDS ●
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Merocrine: ● most common – secrete products via exocytosis ● secretory cells remain in tact ● ex. pancreas, sweat glands, salivary glands Holocrine: – cells rupture releasing their products and their selves ● cells are replaced by division of underlying cells ● sebaceous (oil) glands
ENDOCRINE GLANDS ●
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Send chemical messengers “hormones” directly into bloodstream to travel to and affect other cells Ductless thyroid, testes, ovaries, pituitary, adrenal, etc.
FOUR TISSUE TYPES ●
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Epithelial tissue Connective tissue
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Muscle tissue
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Nervous tissue
CONNECTIVE TISSUE (CT) ●
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The most abundant, widely distributed, and histologically variable of the 4 tissue types These tissues connect and fill, and their cells are loosely packed There are few cells, and these are generally widely separated by an extracellular material – ‘extracellular matrix’ (ecm)
CONNECTIVE TISSUE Functions:
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– binding of organs – support/ framework of body – physical protection – immune protection – storage (energy reserves, minerals) – insulation – transport
COMPONENTS OF CT ●
Ground substance: ●
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Fibers: ●
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collagen, elastic, or reticular
Cells: ●
filling material
fibroblasts, chondroblasts, osteoblasts, and white blood cells
Connective tissue
Connective Tissue Massage
Ground Substance ●
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Gellike noncellular component of CT Composed of water, glycosaminoglycans, proteoglycans, and glycoproteins Varies depending on the type of CT
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Collagen: ●
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thinner collagen fibers extensive branching to form frameworks for certain organs
Elastic: ●
thick fibers with great tensile strength interwoven strands of collagenous proteins
Reticular: ●
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FIBER TYPES
long thin fibers allowing for stretch and recoil
CELLS Naming:
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fibro; chondro; osteo blast (produce ecm) clast (destroy ecm) cyte (maintain ecm)
Other cells in CT
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adipose (fat) cells white blood cells macrophages, etc.
CATEGORIES OF CT ●
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1: Fibrous CT ●
AKA “connective tissue proper”
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Loose (3) and Dense (2)
2: Supporting ct ●
Cartilage (3) and bone
3: Fluid ct ●
blood and lymph
FIBROUS CT Loose CT
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– lots of ground substance and cells, few fibers ● areolar, reticular, adipose
Dense CT
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– many fibers, few cells, and little ground substance ● dense regular, and dense irregular
LOOSE AREOLAR TISSUE ● ●
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Loosely arranged Contains all three fiber types, fibroblasts, macrophages, wbc’s Surrounds blood vessels and small nerves
LOOSE AREOLAR TISSUE ● ●
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Underlies almost all epithelial tissue Serves as ‘packing material’ between tissues; allows for some movement, but keeps things in place Site of edema Reservoir of nutrient, water, salts, for surrounding tissues
LOOSE RETICULAR TISSUE Supports blood cells in lymphoid organs
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(reticular fibers act as scaffolding.)
found in spleen, liver, lymph nodes
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LOOSE ADIPOSE TISSUE ●
Filled with adipocytes ●
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adipocytes are filled with inclusion body (oil droplet)
Not much ecm Energy storage, thermal insulation, shock absorption Richly vascularized (why?) Found under skin; around highly active organs (heart, kidney)
DENSE REGULAR ● ● ● ● ●
Fibers: mainly collagen Cells: mainly fibroblasts Not much ground substance Poorly vascularized Collagen fibers run in parallel densely packed – gives much tensile strength in one direction ● very strong ●
DENSE REGULAR ●
Tendons: ●
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Aponeuroses: ● ●
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sheetlike muscle to muscle; or muscle to bone
Ligaments: ●
muscle to bone
bone to bone
DENSE IRREGULAR ●
Densly packed collagen running in many directions ●
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Poorly vascularized Locations: ●
durable, can withstand stresses in many/ unpredictable directions
deep dermis of skin; organ capsules; surrounding cartilage and bone
Supportive/Structural CT •
Cartilage – hyaline cartilage – fibrocartilage – elastic cartilage
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Bone
CARTILAGE ●
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Dense tissue of cells (chondrocytes) and collagen High ‘viscosity’/ firmness 80% water ●
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allows it to withstand compression
Good for tension and compression
CARTILAGE ●
No nerve or blood supply ●
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nutrients are obtained through diffusion from the surrounding ct
Chondroblasts slow down in their production of new matrix after the skeleton stops growing Injuries to cartilage are very difficult to heal Osteoarthritis
CARTILAGE (3 TYPES) ●
Hyaline cartilage: ● glassy appearance ● chondrocytes randomly oriented ● embryonic skeleton, articular cartilage, tip of nose, ribs to sternum
CARTILAGE TYPES ●
Fibrocartilage: ●
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chondrocytes in groups between collagenous fibers strong and compressable pubic symphysis; intervertebral discs
CARTILAGE TYPES ●
Elastic cartilage ●
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similar to hyaline with more elastic fibers has strength and flexibility ear; epiglottis
BONE ●
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Hard calcified matrix with many collagen fibers Well vascularized Cells: ●
osteoblasts, cytes, clasts
FLUID CT: BLOOD ● ● ● ●
Matrix: blood plasma Cells: rbc, wbc Fibers: in clotting Functions: ●
carry nutrients, wastes, respiratory gases, etc.
FOUR TISSUE TYPES
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EPITHELIAL
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CONNECTIVE
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NERVOUS
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MUSCLE
NERVOUS TISSUE ● ● ●
Excitable Cells: neurons; glia Functions: ●
communication, control
MUSCLE TISSUE
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Excitable Cells: muscle cells Function: movement Types: ●
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Skeletal – Voluntary movements Cardiac – In heart, involuntary Smooth – –
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important in digestive system found mainly in walls of hollow organs (except heart) involuntary control