• Phospholipids, cholesterol, proteins, oligosaccharide chains covalently linked to several phospholipid and protein molecules
• Selective barrier = regulates passage of materials
• Keeps constant ion content of cytoplasm
• Recognition and signalling functions = role in interacting with environment
• Integrin protein, liked to cytoskeleton and ECM = continuous exchange of influences in both directions
• 7.5 to 10nm thickness = visible only on electron microscope
• Membrane phospholipids are amphipathic = two non-polar/hydrophobic fatty acids linked to charged polar/hydrophilic head - phosphate group
  • Most stable in bilayer
• Cholesterol, sterol lipid, insert at varying densities in tails= restricts movement and regulates fluidity of membrane
• Red blood cells phosphatidylcholine and sphingomyelin = phospholipids more abundant in outer and phosphatidylserine and phosphatidylethanolamine are more concentrated in the inner layer
• Glycolipids = oligosaccharide chains that extend outward from cell surface and contribute to glycocalyx = cell surface coating
• TEM = cell membrane - trilaminar appearance after fixation with osmium tetroxide
  • Osmium binds polar heads of phospholipids and oligosaccharide chains - produced two dark outer lines = enclose light band of osmium-free fatty acids
• Integral proteins = directly within lipid bilayer
  • Can be extracted using only detergents to disrupt the lipids
  • Polypeptide chains span membrane, many times = multipass proteins
  • Hydrophobic interactions between bilayer and nonpolar amino acids
  • Freeze-fracture electron microscope; parts of many integral proteins produce from both outer or inner membrane surface
• Peripheral proteins = bound to one membrane surface, usually cytoplasmic side
  • Can be extracted with salt solutions
• Carbohydrate of glycoproteins project from external surface of plasma membrane and contribute to glycocalyx = receptors
  • Cell adhesion, recognition, response to hormones
• All membranes are asymmetric
• Many proteins not bound rigidly = able to move laterally
  • Often restricted by cytoskeletal attachments
  • Epithelial cells; tight junctions between cells - restrict lateral diffusion of unattached transmembrane proteins and outer layer lipids - different domains with cell membranes
  • Fluid mosaic model
• Proteins of large enzyme complexes are usually less mobile, esp those involved in the transduction of signals from outside cell
  • Located in specialised membrane patches = lipid rafts = higher conc of cholesterol and satu fatty acids = reduce lipid fluidity, presence of scaffold proteins - maintain spatial relationships between ezymes and signalling proteins = allows proteins to remain close = interact more efficiently

• Zygote = spermatzoon with an oocyte
  • First cellular divisions = blastomeres = all tissue types
• Inner cell mass = embryonic stem cells
• Differentiation = differently express sets of genes that mediate cytoplasmic activities = very efficient in specialised functions - change shape
  • muscle cell precursor elongate into fiber-like cells, large myosin and actin
  • specialised for using these proteins to convert chemical energy into forceful contractions
• specialised cells greatly expanded their capacity for one or more of these functions during differentiation
• changes in cells' microenvironments under normal and pathologic conditions can cause same cell type to have variable features and activities
• cells similar structure-wise often have different receptors for hormones and ECM = behaves differently
  • Breast fibroblasts and uterine smooth muscle cells = sensitive to f sex hormones

• Collapsible muscular tube = 25cm
• Posterior to trachea
• Inferior end of laryngopharynx
• inferior aspect of neck
• Mediastinum anterior to vertebral column
• Pierces diaphragm - oesophageal hiatus
• Superior of stomach = end
• Hiatus hernia = protrusion of section of stomach Histology
• Mucosa = nonkeratinized stratified squamous epithelium, lamina propria (areolar connective), muscularis mucosae (smooth muscle)
  • stratified squamous [lips, mouths, tongue, oropharynx, laryngopharynx and esophagus] = considerable protection against abrasion
  • submucosa; areolar connective, blood vessels, mucous glands
• muscularis of superior third = skeletal
• muscularis of intermed = skeletal + smooth
• muscularis of inferior = smooth
  • end of esophagus --

• Epithelium
  • nonkeratinzied stratified squamous epithelium
  • simple columnar epithelium
  • also have exocrine cells that secrete mucus and fluid = enteroendocrine cells - secrete hormones
• Laminae Propria
  • areolar connective tissue = blood, lymphatic vessels
  • supports epithelium - binds to muscularis mucosae
  • MALT = immune system cells
• Muscularis Mucosae
  • mucous membrane into small folds = increase SA
    1. Submucosa
       • aerolar connective tissue
       • extensive network of neurones = cosal plexus
       • glands and lymphatic tissue
    2. Muscularis
       • skeletal muscle = voluntary swallowing and defecation
       • smooth muscle - inner = circular - outer = longitudinal
       • second plexus of neurons = mycenteric plexus
    3. Serosa
       • serous membrane - areolar connective tissues and simple squamous epithelium
       • visceral peritoneum

Skeletal muscle covered with mucous membrane Symmetrical halves by a medium septum 1. extrinsic = insert into connective tissue move tongue side, in/out 2. intrinsic = insert into connective tissue within tongue<br /> alter shape, size for speech and swallowing

Lingual frenulum = fold of mucous membrane

Sockets of alveolar processes of mandible and maxillae Covered by gingivae Lined by periodental ligament = dense fibrous connective tissue - anchors teeth 1. Crown 2. Roots - 1-3 3. Neck Dentin forms majority = calcified connective tissue * Crown = enamel * Root = cementum Pulp cavity = within crown filled with pulp * Narrow extensions = root canals - apical foramen

• Non-volatile acid excreted in urine, most = H+ excreted as undissociated acid = buffers urinary pH between 5.5-7.0
  • acid secretion = inorganic acids e.g. phosphate and ammonium ions, uric acid, dicarboxylic acids, tricarboxylic acids e.g. citric
  • major source is H2SO4 = generated from sulphur containing compounds ingested in foods - amino acids cysteine and methionine
  • strong acid dissociated into H+ and SO42- in blood and urine
  • urinary excretion of H2PO4- removes acid
• Metabolic homeostasis = excrete equal phosphate as ingested
• NH4+ major contributors to buffering urinary pH
  • NH3 is base = combines with protons to produce NH4+ ions - pKa = 9.25
  • NH3 produced from amino acid catabolism or absorbed through intestine - toxic so kept at neural tissues

• PO43- and proteins = major buffers in maintaining constant pH of ICF
• H2PO42- = inorganic, dissociates to generate H+ and the conjugate base, HPO42- with pKa of 7.2
• Organic phosphate anions e.g. glucos-6-phosphate, ATP, also act as buffers
• ICF contains high content of proteins, histidine and other amino acids = accept protons in a similar way to Hb
• H+ out of cell maintains intracellular pH
• Metabolism = CO2 and other acids
• pKa for most metabolic carboxylic acids is below 5 = dissociates completely at pH of blood and cellular fluid
• Metabolic anions transported out of cell with H+.
  • Cell too acidic, more H+ out for Na+
  • Cell too alkaline, more bicarbonate out for Cl-

• TCA cycle = CO2 diffuses into intestinal fluid - blood plasma - rbcs
• rbcs contain high amount of carbonic anhydrase = CO2 rapidly converted to carbonic acid
• Carbonic acid dissociates = H+ released, buffered by certain amino acid side chains in Hb
  • Bicarbonate anion is transported out of rbc in exchange for Cl- = bicarbonate is relatively high in plasma
• rbc approaches lung = equilibrium reverses
  • CO2 is released from rbc = more H2CO3 dissociates into CO2 and H2O
  • H+ combine with bicarbonate
  • Hb loses some of its H+, allows it to bind to O more readily
• Bicarbonate and H2CO3 diffuse through capillary wall from blood into intestinal fluid = major buffer for plasma and intestinal fluid
• Protein content of blood is high e.g. albumin = contribute to buffering capacity through amino acid side chains = accept and release protons
  • Protein content of intestinal fluid is too low to serve as an effective buffer

• CO2 produced from fuel oxidation in TCA cycle
• Normal metabolic produces 13 moles of CO2
  • dissolves in water = H2CO3 - accelerated by carbonic anhydrase
  • weak acid - H+ and HCO3-
  • pKa = 3.8 - almost completely dissociated in blood
  • theoretically unable to buffer blood at 7.4
  • However CO2 replenished from body fluids and air
  • Conc of base increased, H+ removed, H2CO3 dissociates
  • Forces dissolved CO2 to react with H2O = H2CO3
  • Dissolved CO2 is in equilibrium with CO2 in air
  • CO2 availability adjusted through by rate of breath and expiration
• pKa for bicarb buffer system in the body combines with Kb with chemical pKa = 6.1
• Respiratory centre controlling rate of breath, hypothalamus, = sensitive to pH flux
  • pH falls individuals breathe more rapidly and expire more CO2
  • pH rises, they breathe more shallowly

• Weak acid and its conjugate base
• Resist changes in pH when H+ or OH- added
• Half of OH- added = Half of conjugate acid dissociated
  • [A-] = [HA] thus pKa
• More OH- more conjugate acid dissociate to H+ to combine with OH- = water = increase in pH
• Add H+ to buffer at pKa = conjugate base combine with H+ to form HA = no fall in pH
• Compensate for influx or removal of H+ within 1 pH of pKa
  • [A-]:HA changes from 1:1 to 1:10
  • More conc buffers are more effective

Caused due to dipole nature of water * two unshared electrons that form an electron-dense cloud around it * above and below plane * covalent bond between H and O * e- attracted to O = partial negative - more electronegative * H = partial positive * Form H bonds - hydrogen shells * Weak noncovalent interaction between H and the more electronegative atom of an acceptor molecule * O can from H bonds with two other acceptor molecules = each H2O bonded to 4 other in a fluid 3D lattice * anions surrounded by hydration shell arranged with their hydrogen atoms closes to the anion * O of H2O interacts with cations to surround * H bonds strong enough to dissolve polar molecules in H2O and separate charges * Weak enough to allow movement * Strength = 4kcal/mol

• concentration = 10-7 mol/L
• pH = 7
• dissociates = 55.5mol/L
• Kw = 10-14 mol/L2

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