Anatomy and Cell Biology 3309 Midterm Summary.docx

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Anatomy and Cell Biology
Anatomy and Cell Biology 3309
Graeme Taylor

3309 Summary: Lecture 1:Mammalian Histology - Introduction histology: microscopic anatomy - study of tissues at the light and e-microscope level Advantage Disadvantage - ability to visualize structures not normally - samples examined are 2D representations of seen with the naked eye the original tissue, you must “imagine” the 3D structure. - Tissues undergo chemical modification that can misrepresent the living tissue= artifact Microscopes Light Microscope E- microscope Fixation Formaldehde: 1 rxn’ group Glutaraldehyde: 2 rxn’ groups - good penetration - poor penetration Formalin - for proteins and carbs Osmium tetroxide - good penetration for lipids (like PM) Embeddin Dehydrate tissue then infiltrate with liquid embedding soln’ to harden and g subsequently section Sectioning - can be many sections – picture of cuts on a tube e.g. figure 8 is at a bend - Section tissue at 5um (wax)/ 5- - Section at 60nm (epoxy resin)/ 80nm 10um (paraffin) (plastic) - slice with a microtome - slice with an ultramicrotome/ diamond Staining - remove paraffin/ wax - salts of heavy metals absorb e-s - stain (e.g. H&E) - stain (e.g. lead citrate) Mounting - dehydrate and seal on glass slide - place on copper grid for e- to pass through Resolution 0.2um/200nm - 3nm * allows one to see PM (10um) ** - reveals the cell’s ultrasection (fine structures only visible with an e- microscope) Immunocytochemistry staining method: used formaling bc allows proties to react w/ Ab’s - use Ab’s to attach to fluorchromes (fluorescent dyes) which attach to antigens (proteins) - seen with a fluorescent microscope + UV light which activates the dye and emits the color Staining Stain What is stains What color it is Hematoxylin - General staining with eosin - blue - stains nucleic acids (DNA/RNA, rRNA [ribosomes]/ER) - stains –ve charged things - stains basophilic things Eosin - general staining with Hema - red/pink - stains +ve charged things - stains acidophilic things Osmium tetroxide - to retain membranes - black/brown structures (lipids) = heavy metal stain PAS (techinique) - acidic - stains magenta and collagen - stains mostly carbs and fibrespink proteoglycans - stains Basement membranes, mucous, reticular fibres and glycogen Toluiodine blue - mast cells - purple - see negative golgi image (no ribosomes, doesn’t pick up stain) Silver impregnation - rxn’ with sugar molecules - brown/black Chemical composition of Tissues: • Nucleic acids: DNA and RNA • Protiens: • Carbohydrates: storage of energy + structural support • Lipids: energy storage or structural support (cell membranes) Resolution: - minimum distance that 2 points can still be distinguished as distinct - defined by D= lambda/ 2NA • Lambda = wavelength • NA(numerical apperature)=nsin(alpha) • N= refractive index; medium that light is passing through To increase reolution, we want to decrease D! Thus the lower D via 1. decrease lambda/ wavelength (e.g. UV=10-8nm vs. red light 700nm) 2. increase NA, by increasing n (oil is higher than air) Lecture 2: The cell Resolution: Eye = 0.2mm Light Microscope = 0.2um/200nm; better to study the whole cell E-microscope = 3nm; better to study structures within the cell Cell membrane: - Made of Phospholipids = lipid bilayer • Phosphate group (hydrophilic head) facing outwards • Fatty acid chains (Hydrophobic tails) facing inwards Types of proteins: • Integral: have H2O (phobic and phallic) interact with central area of PM • Peripheral: sit on H2Ophillic groups of phospholipids • Transmembrane; span the entire thickness of PM (open to cytoplasm and ECM) Extracellular:covered with • Glycoprotiens: carbohydrates attached to proteins • Glycolipids: carbohydrates attached to lipids •  Glycoccalyx; all carbs on surface ** remember: they can only be seen with an e-microscope Cholesterol – helps with fluidity - Membrane is asyymetrial Protein functions: • Pumps: Na/K, Cl, Ca2+ • Channels: chemical (share metabolites) or electrical (myocyts for unison contraction • Receptors: lipoproteins; can be specific to for ligands • Linkers; integrins – link cells to collagen or ECM or other cells • Enzymes: ATPase, lipase • Structural: adhesion, linker Cytoplasm: - organelles and inclusions, the rest is cytosol Organelles and Inclusions: Membrane bound Free Organelle Inclusions organelle - energy requiring - storage of energy/ pigments - nucleus - ribosomes - stored food - golgi - cytoskeleton (MT/MF, IF) (glycogen/lipids) - ER (sER, rER) - pigement (endogenous/ - Lysosomes exogenous - Secretory granules - Mitochondria Protien synthesis: - mRNA production in nucleus – transcribed off DNA sequences - leaves via nuclear pores - enters cytoplasm - interacts with ribosomes – free floating/ ER - ribosomes are made in the nucleolus and are made of two subunits (large and small) - ribosomes translate mRNA *polysome – translating the same mRNA sequence – found free or membrane bound to ER The rER -membranous network of cisternae –empty spaces in the lumen - ribosomes – reside on the “spotted bands”; 20-30nm in diameter, have a large and small subunit, are assembled in the cytoplasm, consist of rRNA and protein, rRNA … basophilic staining (hemotoxylin stains it blue) - organelle membrane = 8nm Fxn: - proteins made @rER are packaged into transfer vesicles (smooth/made of clarathin) - bought in by a signal sequence which leads the peptide into the rER cistern (the signal sequence is then removed so that the protein does not go back out) - mRNA half life is the means of controlling translation  COPII goes to golgi (transfer vesicle that is either smooth or coated with clathrin)  COP I brings them back from the golgi Vs. SER: more tubular (rER is more shelflike/sheet like) - involved not in protein synthesis by lipid (+steroid)synthesis – found commonly in the liver for detox of alcohol and drugs - specialized in muscle Golgi - segregates and modifies proteins and lipids (glycosylation) - involved in the production of membranes, lysosome, and secratory products - membranes specific to rER and golgi are returned - normally adjacent to the nucleus - completely excluded of ribosomes - made of sacuoles (3-10 = 1 golgi network) - up to 5 golgi networks can exist in a cell - protein makes it’s way from the cis face to the trans face - can be sent to the lysosome via a lysosome vesicle - can be secreted from the cell via a secretory vesicle (contain glycoprotiens) - negative image in H&E sections, and toluiodine blue Condensing vacuole: contains water, and later condensed protein by expelling water – is a concentrated form of secretion found in secreatory vesicles Lysosome; 3 pathways Autophagy Pinocytosis receptor Phagocytosis mediated endocytosis – - old organelles are - engulf soluble specific - for larger materials surrounded by an material in a non- involving coated (e.g. pathogens like autophagy specific fashion pits lined with bacteria) membrane (from ~ clatherin Vesicle = phagosome sER) and digeseted - passively put into a - can be exocytosed to vesicke via form a lupofuscin endocytosis (pigment - vesicle = early yellow/brown) endosome  late endosome; responsible for sending receptors back up  fuses with lysosome Primary secondary Tertiary/residual bodies - nothing to degrade - uses acid hydrolyzase to - failure to break s/t down actively break something down - lives in the cell for as long as cell is alive - v. e-dense - seen as lighter and larger - responsible for residual (less e-dense pigments ** secondary lysosomes cannot be recycles back into primary ones, they are degraded directly after being used - membrane bound with acid hydrolyzses, pH 5.0 - degrade just about everything Mitochondria: • Crista: inner membrane responsible for oxidative phosphorylation  ATP - shelflike/ finger like, covered with elementary particles: connect e-transport to phosphorylation • Outer membrane|| inner membranous space|| inner membrane ** remember: 8nm - has x2 membranes • Intercristal space: mitochondrial matrix = has it’s own mitochondrial DNA, RNA, ribosomes (can’t make all the proteins mitochondria need!), enzymes for lipid and protein synthesis, and Kreb cycle enzymes • Mitochondrial granules: storehouse of divalent cations (ca2+ and PO4-) • Reproduces via fission (like bacteria) • O.2-2um in width, 2-7um in length If I was in a cell where the max # of mito in cell could hold, still wasn’t giving enough energy, what shape could the crista go into  like microvilli  finger-like projections + shelflike  number of mitochondira is related to energy requirements of the cell Inclusions • Stored food: - glycogen - free in cytoplasm (mostly in liver and muscles) - seen as e-dense in e-microscope - vs. seen as empty spaces in light b/c of paraffin • Fat: - adipocytes  show lipid (inclusion) under microscope as empty circles - nucleus found to the side, surrounded by thin ring of cytoplasm - metabolically very active! – for release and storage of energy - Vs. multilocular cell of brown fat: fat is in droplets bc strands of cytoplasm run through them with mitochondria - still breaks down glycogen for energy (ATP) but the e-chain is disrupted thus it generates a lot of heat - found in hibernating animals and children • Pigments: o Give an example of a pigment that the body makes: (Endogenous pigements) - Melanin: gives skin its color - tertiary lysosomes, which look like brown pigement in the cell aka. Microfusion granuoles - bruises: from breakdown of heme in hemoglobin; deep purple and blue are from hemoglobin itself hemosiderin, bilirunin, bliverdin - oxygentation and break down via bilyrubin o Vs. Exogenous pigements: - carotene: from vegetables – gives triglycerides (normally white) a yellow color because they are lipid soluble - carbon – from smoking or pollution - tattoos Lecture 3: Cytoskleton, Nucleus and Nucleolus MTs: 24nm, MF 6nm, IF 10nm Microtubules: Centrioles: - consist of 9 triplets of MT/s - 2 per cell (found 90 degrees to each other) - found within the centrosome when cell is undergoing cell division Centrosome ( MT organizing centre) - contains centrioles - pool of gamma tubilin rings from which MT are initiated - found in close proximity to the nucleus MT’s - originate at centrosome or MTOC - consist of a and b tubulins, and form dimmers - have polarized + and – ends (grows from + end!) - able to rapidly assemble/ dissemble - MAPS links MT to other structures Functions: - centrioles and basal bodies (@ base of cilia) - axoneme (core) of cilia and flagella for movement - mitotic spindle (elongates and shortens to bring centrosomes to poles) - maintenance of cell shape - cell movement and elongation - intracellular transport Cilia: - found at epithelial surfaces and arelittle haris that can move - have basal bodies (pre cursors of centrioles) at base - found in trachea and nose (not intestine) and fallopian tube of reproductive system Flagella: - help flagella in movement - have lots of mitochondria associated to help with movement MAPS: - kinesins: from – to + end – take things from the cell body to the periphery of the cell - dynein: from + to – end  take things from periphery back to the cell body Microfilaments/ Actin Filaments: - formed from actin - 6nm in diameter - free actin is referred to as G-actin/ globular actin - F actin = filamentous actin - has polarized +/- ends - has actin binding proteins - found on muscle, and associated with contraction Tropomyosin – covers myosin bindng areas Tropomodulin – capping protein on actin fibres (at –ve end) Alpha actinin Myosin (thick filaments) vs. actin = thin filaments Functions: - anchorage and movement of membrane proteins - core of microvilli - cell movement - cll adhesion - extension of cell process such as movement and migration Intermediate Filaments: - are 8-10nm in diameter - consist of a variety of classes depending on the cell type - nonpolar; thus very stable - have a mainly structural role - other structures are cross linked - role in Alzheimers – neurofibrillary tangles - monomers dimmers  tetramers  fibrils – associate/ cross link with other structures - given specific names depending on where they function Cell type Protien IF Epithelial (skin) prekeratin Tonofilaments Muscle Desmin IF Connective tissues Vimentin IF Neurons Neurofilament Neurofilament Astrocytes Glial fibrillary Acid Protien Glial filaments The nucleus: - variable size, shape and structure - LM: basophilic – very visible, nuclear envelope is usually visible because of the peripheral heterochromatin - EM: trilaminar structre (2 membranes) is visible separated by a25nm space - not static - contains: o Chromatin o Packaging: DNA  beads on a string (chromatin)  30nm chromatin fibril  chromatin with loops DNA strand is 3.5nm thick, coiled 2.5x around histone( 10nm thick)  forms nucleosomes (supercoiled nucleosomes) + other proteins = 30nm – visible in EM  looped domains form around axial scaffold Euchromatin = looser loops; less dense – transcriptionally active and facultative Heterochromatin = tighter loops; seen only when entering cell division; more dense – attracts more dye During mitosis  condenses o Nucleoli – dense staining, where ribosomal RNA is transcribed, and in s the initial stage of ribosomal formation. ~ transcient – when increase protein is needed/ made. There is more need for ribosomes, and thus a prominent nucleoli - types of RNA: rRNA, mRNA, tRNA, snRNA o Fibrillar center: contatins DNA loops of rRNA genes exposed for transcription (lighter) o Pars fibrosa: main activity of nucleolus where rRNA gens are transcribed (darker) o Pars granulose – subunits starting to be made – and more granular looking o Nucleolonema = collection of these trhee regions - tree formation of more than one RNA polymerase reasing per gene - protein + RNA =ribonucleoprotien found in ribosomes - large subunit found in nucleolus, small subunit goes to cytoplasm o Nuclear envelope – continuous with cisternae of ER o Nuceloplasm; material in the nucleus o Nuclear pores (70nm): allow entry / exit of substances – controlled by proteins Lecture 4:Epithelia and Glands 4 basic tissue types: epithelia connective tissue muscle nervous - covers surfaces - provides structural Contractile cells - receives, transmits - lines cavities/ lumen and functional support 3 types: and integrates (found in respiratory - carries nerves and - skeletal information to the and surrounding blood vessels - cardiac control activites of the blood vessels) - ECM – imp. Role - smooth body - forms glands - many diff. - includes neurons - polarized specialized types and supporting cells - non vascular (blood, bone, - CNS and PNS (2 cartilage, and immune types) system) Function of epithelia: 1. secretion (invaginate into glands that secrete things) 2. absorption 3. transport; materials into the intestine 4. protection; how? Skin has multiple layers, and protects, against wear and tear, retains moisture, protects against chemicals and pathogens 5. receptor: are modified epithelia (e.g. tastebuds are the joining of epithelial and nervous tissue) Cell Polarity: - apical vs. basolateral side - apical side is free to the lumen Apical side may have cell differentiations such as cilia, microvilli and stereocilia - the basolateral side is attached to other cells by e.g. tight junctions, and attached to the basement membrane - the basement membrane is made of collagen fibres and proteoglycans and is an additional layer between epithelial cells and connective tissue Classification of Epithelium - based on morphological characteristics 1. Number of cell layers 2. Shape of the cells 3. Presence of specializations – cilia, keratin, and goblet cells Simple squamous - special cases: Endothelium –when lining blood vessels Mesothelium – when lining organs - lines surfaces involved in passive transport of fluids or gases Simple cuiboidal - lines ducts and tubules Simple columnar: - typically found on absorptive surfaces Pseudostratified columnar epithelia - with or without goblet cells - all cells rest on the BM but not all may reach the surface. Stratified squamous epithelium (keratinized @skin, or nonkeratinized @ vagina) Transitional epithelium - found only in the urinary tract - accommodates stretch - withstands toxicity of urine - dome shaped surface cells - may contain 2 nuclei (no reason why) Basement Membrane - shows well with PAS staining – magenta line - stains with Hand E as well - serves as attachment site of cells to underlying CT (lamina fibroreticularis) - electron dense layer lying below cell is basal lamina (lamina densa) - has type 4 collagen, proteoglycans, laminin, fibronectin and entactin Lamina rara (lamina lucida) is between the basal membrane and the lamina densa and is 40nm - contains integrins that connect cell to extracellular matrix, namely fibronectin, collagen and laminin Functions: attachment, compartmentalization, filtration, polarity, induction, scaffolding Glands: Classes: 1. exocrine (duct to surface) 2. endocrine (hormones to blood stream) Mechanisms of secretion: - Merocrine (exocytosis of secretory product only) - Apocrine: plasma membrane, cytoplasm, secretion - Holocrine (secretion and entire cell) - exocrine glands are unicellular (goblet cells) or multicellular - multicellular glands are classified according to : 1. complexity of secretory or duct portion 2. shape of secretory cells - secretions are mucous (thick and slimy) or serous (watery) Lecture 5 – Cell Junctions and Surface Modifications: Apical Doman Lateral Domain Basal Surface - cilia, microvilli, and - zonula occludins, zonula - hemidesmosomes stereocilia adherins, macula adherens, gap junctions Types of Junctions: zónula (belt), fascia (band), macula (spot) Functions: occluding, anchoring, communication Terminal Bar: Type Tight/Occluding Adhering Junctions Gap Junctions Junctions Location: Epithelium, and Epithelium and cardiac muscle Most cells endothelium * imp. In cardiac cells – send electric impulse quickly Function: - seal off lumen @ - physical anchor: holds cells together - communication baso lateral surface - T/M, anchoring protein, cytoskeleton junction, found between many cells Example Zonula/fascia Zonula adherins Macula Adherens Hemidesmoso -- spot like Occludens (Desmosome) me Protiens Occludin (integral) E cadherin Desmocollin/desmoglein (t/m) -IF Connexions x2 = (w/Ca2+) (t/m) - intracellular attachme- intracellular associated: Claudin (t/m) Catenin plaque attachment channel Actin (IF) Vinculin -IF (diff names depending onplaque X2 channels = Actin (6nm) where it is) (10nm) - integrun - collagen 4 connexon - can close/open size 20nm 30nm Where? Lateral lateral lateral basal lateral Zonula – tight seal Fascia – permeable Cilia a. Microvilli b. Stereocillia - rich in MTs - lots of actin - v. long microvilli (actin) - mitochondira - mitochondria - not ciliated b/c no MTs - motile via passive mvmt - no mitochondira - axoneme (9MTs pairs) - axoneme (actin) - can be crosslinked (at actual - basal body (9 MT triplets) - tethered to microvillus stereocilia) MTs joined with dynein - terminal web = crosslinked actin and myosin - seen as brush border in LM - most easily seen with PAS (b/c of glycoprotiens) Kartagener’s syndrome - found in intestine - found in male reproductive - lack dynein arms system: sweeps sperm along - immotile cilia (=resp. - found in vestibular problems) apparatusl detects fluid = M: spermatozoa don’t work movement in ear – turns = F: may have more ectopic motion into an impulse pregnancies/ harder to concieve Lecture 6: Connective Tissue and their Products: What is connective tissue? - its function is to join support and provide structures for tissues and organs - it mediates exchange of nutrients, metabolites and waste products between tissues and the circulation Types of Connective Tissue Proper: - adipose (adipocyte) - bone, tendon (dense) + ligaments - loose (fibroblast), cartilage (chondroblast) - marrow stroma (bone marrow) - hemopoietic tissue (where new blood cells are formed) - lymphatic tissue - blood -embryonic CT including mesenchyme and mucous CT  all originate from mesenchymal stem cells (embryonic cells) CT Cells: • Fibroblasts • Endothelilial cells • Pericytes • Macrophage • Mast cells • Plasma cells • Adipocytes Fibroblasts: - synthesize and maintain ECM (ground substance + fibres) of CT What intracellular organelles would you expect to find in a fibroblast vs. a generic cell? - see a prominent nucleolus - large amounts of rER (b/c collagen is a secreted protein) - golgi Endothelial cells and Pericytes: - endothelial cells: line blood and lymphatic vessels - simple squamous epithelial lining that keeps blood in lumen and prevents leakage via tight occluding junctions (some capillaries (e.g like spleen) allow leakage - only the nucleus is visible in LM - fascia occludens junctions - some are fenestrated - pericyte: found in association with blood vessels and capillaries, is a potential source of fibroblasts and smooth muscle cells - mesenchymal precursor cells Mast cells: - oval to round nucles filled with metachromatic granules - receptors on surface for Fc portion of IgE – involved in allergic reactions - IfE on surface recognizes antigen, granules release contents. Histamine and SRSA vasodilate, heparin anticoagulares, eosinophil chemotactic factor brings in eosinophils which destroy the vasodilators and modulate the process Granules contain: - heparin - histamine – both are vasodilators (bring fluid) - slow reacting substance of anaphylaxis (SRSA) - eosinophil chemotactic factor (attracts eosinophils ~ type of blood cell) - sit in CT – part of the immune response e..g in skin if you come under something you’re allergic to, the cells will release their granuoles and cause: - vasoconstriction - fluid build up - recruit other cells of the immune system. Macrophage: - 12 um diameter - formed in hemopoietic tissues - derived from monocytes (formed in bone marrow) in bloodstream - migrate into tissue (diapedesis – process of cells passing through capillaries) and differentiate into macrophage - short lived in blood, long lived in tissue - phagocytic, involved in antigen presentation - become filled with residual bodies (aka. Tertiary lysosomes – engulf debris between cells) - different names in different tissues: (don’t memorize) • Histiocyte – connective tissue • Microglia – CNS • Kupffer cell – liver • Osteoclast – bone • Langerhans’ cell – epidermis Plasma Cells: - 15um diameter - antibody secreting cells derived from mature B lymphocytes - arrive in response to immune reaction - job: is to make Abs – against a foreign antigen - have an eccentric nucleus arrangement – wagonwheel/clock (with a central nucleolus) - b/c Abs are secreted proteins – have a golgi – often seen as a negative image in staining - PACKED with rER at EM level Adipocyte: - fill energy, store lipid and provide energy storage - highly vascularized – lots of blood vessles to fill/remove lipid – metabolically active - signet ring appearance: central fat droplet with thin sytoplasm. Groups of cells look like chicken wire. - surrounded by BM Vs. Brown fat: - multilocat fat - found in abundance in hibernating animals and newborns, remains in body for first decade of life and in adults around major organs - gneenrate heat by lipid oxidation whihch is uncoupled from ATP Fibroblasts 15um in size - mature cell is a fibrocyte - makes all the fibers and ground substance found in CT Components of CT: • Cells (relatively few) • ECM (lots) o Fibres - collagen; resist tensile forced - elastin; memory - reticular; provide a supportive net for cells in tissues o Ground substance (substance everything is suspended in – non-fibrous, and non-cellular) Amorphous Ground substance - main function is to hold fluid: need for material to easily diffuse in and out - consist of a number of different macromolecules including: • GAGs – b/c charged stain well basophilically (e.g. hyaluronic acid) • Sulfated GAGs – stain very basophillic • Proteoglycans – structure: “christmas tree look” – core protein (trunk) with GAG branches, and attached to a GAG base (hyaluronic acid) by a link protien • Glycoprotiens • Tissue fluid - highly hydrated - decreases with age - sulphated GAG’s form firmer gels found in cartilage - GAGs stain with basic dyes - NOT PAS positive though CT fibres: Collagen: 27 different types • Type 1: most abundant (fibrillar); mostly unbranched; bone • Type 2: cartilage (fibrillar) • Type 3: reticular fibres (fibrillar) ; high levels of glycosylation and branched • Type 4: basal lamina (not fibrillar) How it’s made: tiple helix of alpha proteins 300nm by 1.5mm - varying the composition of the protein subunits changes collagen type - has a very repetitive structure, every third aa is glycine - proline and lysine and hydroxylated leading to crosslinking of tropocollagen to increase strength - describe synthesis by fibroblasts, sectretion, self assembly - procollagen, registration peptides, self assembly, cleavage tropocollagen - collagen genes are coded:  protocollagen strand (alpha chain)with N&C terminal – lots of proline and glycine ..via modifications ** needs vitamin C otherwise can’t hydroxylate alpha chains (scurvy – lack of vitamin C --- improper formin collagen e.g. at gums)  Procollagen triple helix Via procollagen N&C proteinases N&C terminal telopeptidase  collagen microfibril (D=0.67) Via crosslinking (b/c of proline and glycine)  collagen fiber Terminology: Molecules Microfibrils (1-20nm)  fibrils (20-90nm)  fibres (mm) Ehlers Danlos Syndrome - cleaving step (procollagen protienases) don’t work = defective collagen = super stretchy skin Elastic Fibres: - made by fibroblasts - tropoelastin derived from pro-elastin. Assembles onto a microfibril scaffold consisting of the protein fibrillin - similar to collagen but not as hydrylated aa. And two unique aa. Called desomosine and iso- desmosine (cross-link elasin) - associated with: • Lysyl oxidase (also stabalizes tropocollagen) • Tropoelastin • Fibulin 4/5  all form a complex to stabalize microfibril - requires microfibrils of the glycoprotein fibrilin for proper organization - ** elastic fibres can be stretched up to 150% of their resting length Marfan Syndrome - deficiency in protein fibrillin 1 = defective elastin – get disorders with the aorta Embryonic – Mesenchymal - mesenchymal cells (undifferentiated) - few loose fibres (type 1 and 3 collagen) - gel-like consistency = glycoprotiens and GAGs - throughout embryo - mucous CT – found in umbilical cord Tupes of Tissues Loose CT - contains a number of different cell types and all three fiber types - suspends nerves and blood vessels - substantial ground substance and water supports diffusion - fewer fibres, abundant cells Dense Connective tissue Irregular: - abundant fibers running in random directions, few cells (mostly fibrocytes) Regular: - all fibres run in parallel to each other. They resist forces in a single direction - form tendons, ligaments and aponeuroses (flattened tendons) Connective Tissue II Type Major Component Function Embryonic- mesynchymal - reticular and collagen fibres - gives rise to all connective tissue types Loose Connective Tissue Areolar - collagen fibres predominate - provides protection, - elastic and reticular fibres suspension and support also present Adipose Adipocytes Energy storage, insulation, sushioning of major organs Reticular Reticular fibres - framework for hematopoietic and paraenchymal organs Dense CT Regular Collagen Strength in one direction Irregular Collagen Strength in multiple directions Elastic Elastic Elastic recoil Loose CT – Areolar: - many cell types may be present: fibroblasts, mesenchymal cells, mast cells, macrophages, adipocytes, plasma cells, leukocytes - Type 1 (delicate) and III (doesn’t stain well w/ H&E) col
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