A&P II Unit 3 Respiratory and Digestive PDF

Respiratory System ● Respiration (4 separate processes) ○ Pulmonary ventilation (air in and out of lungs) ○ External respiration (gas exchange b/w lungs & blood) ○ Transport (transportation of O2 & CO2) ○ Internal respiration (gas exchange b/w blood & tissues) ● Organs involved: ○ nose, nasal cavity...

Respiratory System ● Respiration (4 separate processes) ○ Pulmonary ventilation (air in and out of lungs) ○ External respiration (gas exchange b/w lungs & blood) ○ Transport (transportation of O2 & CO2) ○ Internal respiration (gas exchange b/w blood & tissues) ● Organs involved: ○ nose, nasal cavity, paranasal sinuses, pharynx, larynx, trachea, bronchi, bronchioles, lungs and alveoli ● Muscles involved: ○ Diaphragm, external and internal intercostal muscles, smooth muscle ● Conducting zone -> nose to terminal bronchioles ○ 23 series of branching in bronchioles ● Respiratory zone -> surface area in lungs where gas exchange happens (respiratory bronchioles to alveoli) ● Nose ○ When we inhale, air moistens and warms. ○ External nares = nostrils ○ Houses nasal conchae (superior, middle and inferior) ■ Function: Deflect particulate to mucus surfaces ○ Houses nasal meatuses (grooves under each concha) ■ Function: increase turbulence and surface area ○ Nasopharynx ■ Pseudostratified ciliated columnar epithelium (respiratory mucosa) ● Used to move mucus ■ Also has some goblet cells ■ Cilia used to filter air and move contaminates to the back to be swallowed ■ Pharyngeal tonsil ● Pharynx ○ Includes the nasopharynx (nose area), Oropharynx (mouth area), and Laryngopharynx (lower throat area). Mucosal lining changes along the length of it. ○ Oropharynx (soft palate to epiglottis) ■ Stratified squamous epithelium ■ Palatine and Lingual tonsils ○ Laryngopharnex ■ Stratified squamous epithelium ■ Passageway for food and air ● Larynx (air passageway) ○ Produces vocal sounds via vocal folds/cords ○ The connection between the pharynx to the trachea ○ Upper half (superior) = Stratified squamous ○ Lower half (inferior) = pseudostratified ciliated columnar ○ Know 3 big cartilages for lab practical ● ● ● ● ■ Thyroid cartilage (adams apple), Epiglottis (tips when swallowing), Cricoid Trachea - descends into mediastinum ○ Pseudostratified ciliated columnar ○ Carina (on lab): marks the division of trachea -> 2 primary bronchi Bronchial Tree (know primary, secondary, tertiary, the bronchioles ->alveoli ○ Bronchi ■ Simple columnar epithelium ○ Bronchioles & terminal bronchioles ■ Simple cuboidal epithelium ■ Smooth muscle in bronchioles allows for widening when sympathetically stimulated and constricting under parasympathetic stimulation Lungs ○ Anatomy ■ Left has 2 lobes, right has 3 lobes ■ Cardiac notch -> heart ■ Pleurae ● Parietal pleura and visceral pleura ○ Respiratory bronchioles (between terminal bronchioles and alveolar ducts) ○ Alveolar sacs = clusters of alveoli ○ Alveoli ■ Respiratory membrane made up of alveolar and capillary walls + their basal lamina (alveolar epithelium ->fused basement membrane ->Capillary endothelium) ● Type 1 Cells: Simple Squamous ● Type 2 Cells: simple Cuboidal ○ Secrete a surfactant -> prevents attraction of liquid molecules/ reduces surface tension ■ Surrounded by elastic fibers ■ Have alveolar pores Pulmonary Ventilation -> physical air in and air out of lungs ○ Lung volume changes ^ during inspiration and v during exhalation ■ Causes pressure change which allows for gases to flow across membrane to equalize pressure ○ Inhalation (Inspiration) ■ Diaphragm and external intercostal muscles contract ■ Lung (intrapulmonary) volume increases ● Therefore intrapulmonary pressure decreases -1 mmHg to 758-759mmHg (see boyle's law) ● This causes air to flow into lungs down the pressure gradient until intrapulmonary pressure = atmospheric pressure (760mmHg) ○ Exhalation (expiration) ■ Muscles relax ■ Lung (intrapulmonary) volume decreases (see boye’s law) ● ● Therefore intrapulmonary pressure increases +1 mmHg to 761-762mmHg ● This causes air to flow out of lungs down the new pressure gradient until intrapulmonary pressure = atmospheric pressure (760mmHg) ○ BOYLE'S LAW (multiple questions on this) ■ (P1)(V1)=(P2)(V2) ■ Pressure and volume of gas is inversely proportional ● If pressure increases then volume must be decreasing ● If pressure decreases then volume must be increasing ■ Standard atmospheric pressure = 760mmHg ● When you inhale ->volume increases ->pressure decreases ->758mmHg ● When you exhale ->volume decreases ->pressure increases ->762mmHg ○ Intrapulmonary pressure: pressure within the alveoli (lungs) ● When equalized should be the same as atmospheric pressure (760mmHg) ○ Intrapleural pressure: pressure within the pleural sac (between the visceral and parietal pleura) ■ Usually slightly less than atmospheric pressure (756mmHg) ○ ^ why is this important? BECAUSE this allows for lungs to always stay expanded because there is a net 3-4mmHg difference. ■ If it was flipped and the pleural cavity had more pressure, our lungs would collapse. ■ Called the Transmural pressure gradient ○ Factors Influencing Ventilation ■ Friction -> like mucus when sick ● COPD (chronic Obstructive pulmonary disease decreases the flow of air) ■ Compliance -> lungs ability to stretch ■ Elastic recoil -> ability to return to resting volume after stretch ○ Alveolar surface tension ■ Type 2 (cuboidal) alveolar cells secrete substance that decreases alveolar surface tension to keep alveoli from collapsing Respiratory Cycle - single cycle of inhalation and exhalation ○ Tidal volume (TV) = amount of air moved in one cycle (regular breathing cycle) ○ Inspiratory reserve volume (IRV): air that can be forced in beyond the tidal volume ○ Expiratory reserve volume (ERV): air that can be evacuated from lungs after tidal expiration ○ Vital capacity (VC): total amount of exchangeable air (fullest breath in then out) or (TV+IRV +ERV) ○ ● Residual Volume (RV): the air left even after forcing as much air out after exhalation. The air when you get the “wind knocked out of you” ○ Total Lung Capacity: sum of all lung volumes or vital capacity + residual volume. External Respiration (gas exchange between lungs and environment) ■ Based on partial pressure gradients & gas solubility ■ Alveolar ventilation & pulmonary perfusion ■ Respiratory membrane structure ○ Dalton's Law: Total pressure exerted by a mixture of gases is the sum of the pressure of the individual gases ■ Partial pressure = the pressure of an individual gas from a mixture of gases ■ Air is 21% oxygen… soo ● 760mmHg x .21% = ~160 mmHg Partial pressure O2 ○ PO2 in alveoli = 100mmHg ○ PCO2 in alveoli = 40mmHg ■ Co2 higher in alveoli because cellular respiration and humidification of air by conducting passageways ○ Henry’s Law: The more pressure you exert on gas over a solution/liquid, the gas will dissolve proportionately into the liquid to its own partial pressure ■ The amount also depends on how soluble the gas is… ● CO2 is 20x more soluble than Oxygen ○ Fick’s Law: law of diffusion ■ Don’t need to know the equation, just know these following affect gas rate of diffusion: ● Tissue surface area ○ More area to diffuse across the more diffusion will happen ● Tissue thickness ○ The thicker the tissue the harder for diffusion to happen ● Diffusion coefficient of gas ● ΔP or the difference in partial pressure ○ Greater the pressure difference, the more diffusion wants to happen ○ Partial Pressure Gradients (External Respiration) ■ When pO2 returns to lungs from veins it's at 40mmHg, o2 then diffuses across the alveolar membrane into the bloodstream and re-ups to 100mHg to go towards body tissues. (be able to draw) ■ When pCO2 returns to lungs from veins it is at 46 mmHg, Co2 diffuses across the alveolar membrane into lungs and goes back down to 40mmHg and goes towards body tissues to pick up more CO2. (be able to draw) ○ Partial pressure Gradients (Internal Respiration) ■ When PO2 traveling to body tissues it’s at 100mmHg. Once it gets to the body tissues (which have pO2 of 40mmHg) the PO2 from blood diffuses ● into the body tissue re-upping it to 100mmHg and the remaining pO2 from blood (now 40mmHg) circulates back up to lungs. ■ When blood PCO2 is traveling to body tissues it’s at 40 mmHg. Once it gets to the body tissues (which have 46mmHg) the high PCO2 from body tissues diffuses into blood PCO2 raising it to 46mmHg and then travels back to lungs to off-load the +6mmHg. ○ Ventilation = amount of gas reaching alveoli (lungs) ○ Perfusion = the amount of blood flow reaching the alveoli (lungs) ■ If alveoli CO2 is high and O2 low -> vasoconstriction (slows blood flow ->perfusion) ■ If alveoli CO2 is low and O2 high -> vasodilation (speeds up blood flow ->perfusion O2 transportation in blood ○ Hemoglobin is 98% (never higher) if healthy ■ 2% is always dissolved in plasma ○ Males = 201 ml O2/Liter ○ Females = 174 ml O2/Liter ○ A saturated Hemoglobin = all 4 heme groups have an O2 molecule ■ Partially saturated = 1-3 heme groups have an o2 molecule ○ Rate at which hemoglobin binds and releases O2 ■ pO2 (partial pressure of O2) ■ pCO2 (partial pressure CO2) ■ Temperature ■ Blood pH (H+) ■ DPG ○ Hemoglobin saturation Curve ■ Normal Curve ● pO2 40mmHg = 75% saturation ○ Only 20-25% of bound o2 is unloaded in 1 total circulation pass ● pO2 100mmHg = 98% saturation ● Therefore pO2 has to reach sub 40mmHg before problems start happening (typically sub 75% saturation is used as reservoir incase increased metabolic activity -> like breaking into a sprint) ■ An increase in pCO2, Temperature, DPG and H+ decreases the affinity for O2 ● All the graphs will move to the right ○ CO2 Transport ■ Transported in blood via: ● Dissolved plasma - 7-10% ● When bound hemoglobin - 20% ● Bicarbonate in plasma (most - 70%) ■ FORMULA ● CO2 + H2O <-> H2CO3 <->H+ + HCO3- ■ ● Carbon dioxide diffuses into RBC’s and combines with water to form carbonic acid which dissociates to hydrogen and bicarbonate ions. ^ ● If H+ in blood increases, then excess is removed by combining with HCO3● If H+ decreases, carbonic acid dissociates and releases H+ ions ■ Chloride shift - tissue level (internal level) ● At tissue level, bicarbonate (product of H2O and CO2) quickly diffuses from the RBC and into the plasma. To balance the exodus of negative (bicarbonate) ions from the RBC, chloride ions move into the cell(RBC) for balance. ● Everything is moving from tissue cell into bloodstream into RBC ○ CO2 + H2O --> H2CO3 -->H+ + HCO3■ Chloride shift - lung level (external level) ● At lungs, process is reversed ● Bicarbonate moves into RBC to bind with the hydrogen ions and forms carbonic acid. ● Carbonic acid is then split into H2O and CO2 and then CO2 diffuses out of the cell/bloodstream and into the alveoli ■ Haldane effect ● Removing O2 from Hemoglobin increases the ability of hemoglobin to then go and pick up CO2 and CO2 generated H+ ■ Bohr Effect ● At the tissue level, as more CO2 enters blood, more O2 dissociated with hemoglobin ● Unloading of O2 allows more CO2 to combine with hemoglobin and thus more bicarbonate ions formed Control of Respiration: ■ Medullary Respiratory ● DRG (Dorsal Respiratory Group) ○ Sets basic breathing rate ○ Controls muscles of inspiration and stops neural impulses during exhalation ● VRG (Ventral respiratory group) ○ Involved in forced breathing (inspiration and expiration) ● DRG & VRG use phrenic and intercostal nerves to communicate actions (efferent pathway) ■ Pontine Respiratory Group ● No need to know in depth; just smoothes breathing ■ Input (other than medulla) to Respiratory Centers ● Signals form the cerebral motor cortex ○ Voluntary breathing, ex holding breath ● Hypothalamic controls via limbic system ○ Getting emotional, ex having anxiety & breathing more ● Body Temperature ● ○ ○ ○ ○ ○ Pulmonary irritant reflexes ○ Irritants promote reflexive constriction of airways Depth & Rate of breathing ● If both increased, cause increase in ventilation ● Inspiratory depth is dependent on how respiratory center stimulated muscle contraction (of breathing muscles) ● Rate of respiration dependent on how long inspiratory center is active Central Chemoreceptors ■ Chemoreceptors in medulla monitor levels of pCO2 in CNS ● It’s signal to make sure enough pH isn’t too much ■ Rise of pCo2 = the original stimulus, however the rate of breathing is actually dependent on the H+ ion concentration in the cerebrospinal fluid ● pCo2 levels ^ → diffuses into CSF → CO2 links up with H2O and kicks off the fancy formal resulting in H+ and HCO3○ So although the H+ in the bloodstream bounces back and stays there (because charged), H+ is still formed in CSF ● H+ and CO2 bind to the Central Chemoreceptor on the medulla (through the CSF) which then sends a signal to the Respiratory Control center ○ Drop in pH results in pulmonary respiration ● Respiratory control center signals to the body to increase ventilation. ● Simple version: ○ Increase arterial pCO2 → decrease in pH and increased pCO2 in CSF → signal on chemoreceptors in medulla → medulla signals to Respiratory centers → respiratory centers activate respiratory muscles → increase ventilation —> decrease in CO2 in body → arterial pCO2 and pH return to normal ■ Chemoreceptor for O2 doesn’t turn on till 60mmHg -> almost 50% out of O2.. aka its “lousy” Peripheral Chemoreceptors ■ Peripheral chemoreceptors (those outside the CNS) sense changes of pO2, pCO2, and pH (emphasis on pCO2 and pH -stronger signals) ■ Detect via glomus cells (located in carotid and aortic bodies) that kick off AP Hyperventilation = increased depth and rate of breathing ■ Assists in flushing CO2 ■ Occurs in response to respiratory acidosis ■ Doe NOT affect O2 levels, only rel Hypoventilation = slow and shallow breathing ■ Assists in retaining CO2 ■ Occurs in response to respiratory alkinosis ○ ○ ■ Decreases O2 levels and builds CO2 up Hypoxic drive = when pCO2 levels are chronically high, the chemoreceptors get desensitized and body relies on pO2 levels as respiratory stimulus… which is bag because they only turn on until 60mmHg Arterial pH (acidosis) ■ Changes in arterial pH can modify respiratory rate ■ As explained above, if pH is low -> Kicks off respiratory system controls to increase ventilation to increase pH ■ Caused by ● CO2 retention ● accumulation of lactic acid ● Excess fatty acids in diabetics ■ Alkinosis ● If pH is high, respiratory system controls will try to lower pH by decreasing ventilation (depth and rate of breathing) Digestive System ● Anatomy tidbits ○ Alimentary canal = GI tract ○ Organs ■ Oral cavity, pharynx, esophagus, stomach, small & large intestines, rectum, anal canal ○ Mucosa lines every hollow organ - including GI tract ■ epithelium -> lamina propria -> muscularis mucosa ● Inner to outer ○ Submucosa ■ dense CT with blood and lymph, innervated ○ Muscularis externa ■ Smooth muscle in circular and longitudinal layers ○ adventitia/serosa ■ Outer membrane of CT, collagen and/or elastin ○ Mesentery - double layer of peritoneum (serous membrane) ■ Fat storage & holds organs in place ■ Greater omentum & Lesser Omentum ○ Oral cavity ■ Hard & soft palates ■ Uvula triggers epiglottis ■ Salivary Glands ● Parotid, sublingual, and submandibular ● Saliva: watery solution including electrolytes, buffers, glycoproteins, antibodies and enzymes (ex. salivary amylase -> breaks down carbohydrates) ○ Pharynx ■ ○ ○ ○ ○ Includes oropharynx & laryngopharynx ● Stratified squamous epithelium ■ Common passageway for food & air ■ Pharyngeal constrictor muscles assist in swallowing Esophagus ■ Continuation of the pharynx and carries solids and liquids to stomach ■ Cardiac sphincter joins the esophagus to stomach ■ Stratified squamous epithelium Stomach ■ Cardia - upper part that is joined by cardiac sphincter ■ Fundus - upper most part (top curve) ■ Body - middle part ■ Pylorus - end of the stomach ■ Rugae - ridges & folds that let stomach expand when full ■ Micro-anatomy ● 3 layers of muscle ○ Oblique, circular, and longitudinal ● Simple columnar with gastric pits holding gastric glands ■ Gastric Pits of the stomach ● Mucous neck Cells ->mucus ● Parietal Cells -> HCL and intrinsic factor ● Chief cells -> pepsinogen ● Enteroendocrine cells -> gastrin, histamine, cholecystokinin Small Intestine ■ 3 subdivisions ● Duodenum ● Jejunum ● Ileum ■ Ileocecal sphincter: transition b/w small and large intestine ■ Microscopic Anatomy ● Plicae circulares (circular folds of the mucosa) ● Villi- fingerlike projections for mucosa (simple columnar epithelium) ● Microvilli - villi on each individual cell ● Lacteals - lymphatic vessel of the small intestine ● Cells ○ Absorptive cells: uptake nutrients ○ Goblet cells: secrete mucus for chyme ○ Enteroendocrine cells: secrete hormones ○ Intestinal crypts: secrete intestinal juice b.c of distension etc. Liver ■ 4 lobes ● Left, right, caudate, quadate ■ ● ● Organization ● Lobules made of hepatocytes all empty into bile ducts ->left and right hepatic ducts -> merge to form common hepatic duct ->common hepatic meets cystic duct to form common bile duct ○ Gallbladder ■ Under the liver ○ Large Intestine ■ 4 areas ● Ascending, transverse, descending, and sigmoid ■ Special features ● Teniae coli, haustra, cecum, vermiform appendix ■ Microscopic anatomy ● No villi ● Goblet cells for secretion ● Intestinal crypts - tubular glands ● Simple columnar epithelium until anal canal (stratified squamous) ○ Rectum ■ Inferior half of sacrum ○ Anal Canal ■ Last subdivision of Large intestine ■ 2 different sphincters ● Control over external but not internal sphincter Digestive Processes ○ ingestion -> food entering mouth ■ deglutition/swallowing ○ Propulsion -> movement of food through GI tract ■ Peristalsis -> major means of movement ○ Digestion - broken down into physical and chemical breakdown of food ■ Mechanical digestion -> movement oriented (chewing, segmentation etc) ■ Chemical digestion -> complex molecules broken down into chemical components ○ Absorption -> transport of nutrients into bloodstream ○ Defecation -> elimination of indigestible substances Motility ○ Movement of digestive materials dependent on smooth muscle contraction ○ Tonic contractions ■ Sustained & long lasting ○ Phasic contractions ■ Cycle b/w contraction and relaxation (few seconds long) ■ Initiated by pacemaker cells ● Create slow wave potentials based on temporal summation ■ Stomach and large intestine ○ Peristalsis - waves of contraction that move bolus/food forward ■ Moves forward ○ ● ● ● ● ● Segmentation - alternating contractions that churn and fragment a bolus ■ Mixed up, churning action Stomach Functions ○ Holds & receives food then delivers chyme to small intestine ○ Digests through chemical means (pepsin enzyme) and mechanical ○ Secretes intrinsic factor for B12 absorption Regulation of Gastric Secretion ○ Neural and hormonal mechanisms regulate release of gastric juice ■ Cephalic (reflex) phase: preparation for food entry ● P. symp nervous system (vagus) controls this ● (+) Sight, smell, taste or thought of good ● (-) depression, loss of appetite ■ Gastric Phase: once food enters - enhanced secretion ● (+) chemoreceptors ->peptides, caffeine, rising pH ● (+)Stomach distension-> stretch receptors ● (+) neural -> plexuses ● (+) hormonal -> secretion of gastrin ● (-) pH lower than 2 ● (-) emotional upset overriding p. Symp system ■ Intestinal phase: partially digested food enters duodenum (small intestine) ● Releases hormones that control rate of gastric emptying ● (+)presence of partially digested food ● (+) distension (stretching) of duodenum ● (-) low pH ● (-) presence of fatty, acidic or hypertonic chyme ● (-) irritants in the duodenum Regulation of HCL secretion ○ HCl is stimulated by ACh, histamine and gastrin through a GPLR 2nd-messenger system ■ HCL is low if only 1 ligand (ion/molecule) binds to parietal cells ■ HCL is high if all 3 ligands (ACh, histamin, & gastrin) bind to parietal cells Regulation of Gastric Emptying ○ Gastric emptying controlled by enterogastric reflex & enterogastrone (hormonal mechanism) ● Enterogastric reflex -> distension/stretching of duodenum actually inhibits gastric emptying ● Hormonal mechanisms (enterogastrone) -> hormone secreted by duodenum into the bloodstream to tell the stomach to stop gastric emptying ○ Carb-rich -> moves fast through duodenum ○ Fat rich -> digested more slowly in stomach Gastrointestinal Hormones (5-6 multiple choice Q’s on this) ○ Gastrin ■ Stimulated by protein ■ ● ● ● When gastrin is released, it functions to: ● Increase secretion of HCl and pepsinogen ● Enhance gastric motility ● Help maintain digestive tract lining ■ Inhibited by accumulation of acid ○ Secretin ■ Stimulated by presence of acid in duodenum, which then stimulated ■ When secretin is released, it function to: ● Stimulate pancreatic duct cells to produce NaHCO3 (neutralizer/buffer) ● Stimulates liver to produce NaCO3 rich bile ● Inhibits gastric emptying (stop stomach acid from entering duodenum) ● Inhibits gastric secretion (to reduce acid production) ● Trophic (feeds/nurtures) to the exocrine pancreatic glands ○ CCK (cholecystokinin) ■ Functions to: ● Inhibit gastric motility and secretion (like secretin) ● Stimulates pancreatic acinar cells (functional unit of the pancreas) to secrete pancreatic enzymes ● Contracts the gallbladder ○ GIP (Glucose-dependent Insulinotropic Peptide) ■ Functions to: ● Stimulate insulin from pancreas ● A Gastric inhibitory peptide ○ Aka also inhibits gastric activity like Secretin and CCK Digestion & Absorption in Stomach ○ Preliminary digestion of proteins (by pepsin) and carbohydrates ○ Very little nutrient absorption (other than lipid soluble drugs like alcohol) Small Intestine ○ Glands of duodenum function to: ■ Moisten chyme, buffer acids and maintain digestive material in solution ○ Hormones (all mentioned above - will summarize here) ■ Secretin: produce buffers (NaCO3), increases bile secretion from liver and buffer from pancreas ■ CCK: increases pancreatic enzymes, contracts gallbladder, reduces hunger ■ GIP: stimulates insulin release, inhibits gastric secretion and motility Liver ○ Composed of hepatocytes that: ■ Produce bile ■ Process blood-borne nutrients ■ Stores fat-soluble vitamins ■ Detoxify ○ ■ Bile ■ ■ ● ● ● ● Produce plasma proteins Yellow-green alkaline solution containing bile salts, bile pigments, cholesterol, neural fats, phospholipids and electrolytes ● Bile salts are cholesterol that emulsify fat and facilitate fat and cholesterol absorption Regulation of bile release ● Fatty & acidic chyme signals to duodenum to secrete CCK and secretin ● Secretin and bile salts stimulate liver ot produce more bile ● CCK stimulate vagus nerve causing gallbladder contraction ○ Hepatopancreatic sphincter relaxes ● Bile released into duodenum Gallbladder ○ Stores and concentrates bile by absorbing its water and ions ○ Releases bile via cystic duct -> bile duct Pancreas ○ Endocrine Functions: ■ Maintains blood glucose levels (BGL) ● Release insulin to bring BGL down ● Release glucagon to bring BGL up ○ Exocrine functions: ■ Digestion ● Secretes pancreatic juice ● Acini (secretory acinar cells) that have zymogen granules w/ digestive enzymes ● Juices enter duodenum ■ Regulation of Pancreatic Secretion ● Secretin and CCK released when fatty & acidic chyme enters duodenum ○ CCK helps pancreas secrete enzyme-rich pancreatic juice ○ Secretin helps pancreas secrete bicarbonate-rich pancreatic juice ○ Vagal stimulation helps release of pancreatic juice Digestion in Small Intestine ○ When chyme enters duodenum proteins and carbs partially digested and fat digestion hasn’t started yet ○ Mixing starts happening with combo of juices ○ All nutrient absorption takes place in small intestine Control of Motility ○ Enteric neurons of GI tract coordinate intestinal movements ○ Cholinergic neurons (from p. symp) cause ■ Contractions and distension ○ Gastroileal reflex and gastrin ● ● ● ● ■ Relax ileocecal sphincter allows chyme to move to large intestine Large Intestine ○ Barely any nutrients left at this stage (rest digested by bacteria) ○ Main functions: ■ Absorb water and electrolyte, compact remaining material to feces ■ Absorb vitamins produced by bacteria (B2, B7, B12) ■ Store feces Defecation ○ Distention in rectal walls stimulates contraction of rectal walls Regulation of Digestion ○ Intrinsic (short/local) ■ Autonomous smooth muscle pacesetter cells ■ Intrinsic nerve plexuses and sensory receptors ● Mechanoreceptors and chemoreceptors detect stimulus: ○ Stretch, osmolarity, pH, presence of substrate, end products ● Initiate reflexes that ○ Activate or inhibit digestive glands ○ Mix lumen contents (digestive material) and move it along ■ In summary for Intrinsic Control: ● Stimulus (food, stretch etc) ->receptors (chemo-mechano etc) ->local enteric nerve plexus->smooth muscle or glands create response -> response is contraction or secretion ■ Enteric Nervous System ● Largest and most complex unit of the peripheral nervous system containing the GI tract ● Composed of 2 major intrinsic nerve plexuses ○ Submucosal nerve plexus ■ Regulates gland and smooth muscle in mucosa ○ Myenteric nerve plexus ■ Controls GI tract motility ○ Segmentation and peristalsis largely autonomic and from local reflex arcs but also linked to CNS via long autonomic reflex arc ○ Extrinsic (influence, but not 100% run) ■ Arise from outside the GI tract like CNS ● Autonomic Nervous system (parasympathetic) ● GI hormones ■ In summary for Extrinsic Control: ● Stimulus (seeing/smelling food) ->CNS ->local nerve plexus -> smooth muscle or glands create response -> response is contraction or secretion Control of Digestive System ○ Local mechanisms respond to changes in pH, physical and chemical stimuli ○ ● Neural & hormonal coordinate glands ■ Hormonal enhance or inhibit smooth muscle Digestion & Absorption of nutrients ○ Macronutrients broken down via hydrolysis into monomers ○ Carbs breakdown ■ salivary amylase and pancreatic amylase catabolize (breakdown) into disaccharides then brush border enzymes catabolize to monosaccharides ■ Absorbed through intestine via cotransport (Na+) and diffusion ● Glucose pairs up with Na+ to cross intestinal membrane ■ Enters capillary bed and transported to liver via hepatic portal vein ○ Proteins breakdown ■ Low pH in stomach denatures proteins ■ Stomach enzyme pepsin, then pancreatic enzymes and brush border enzymes in small intestine continue to breakdown till amino acids ■ Absorbed through intestine via cotransport (Na+) ● Just like carbs ● Don’t think we need to know all the enzymes - maybe just know pepsin ■ Lipid breakdown ● Bile salts emulsify lipids turning them into micelles ● Micelles diffuse into intestinal epithelia ● Absorption: ○ Fatty acids and monoglycerides leave micelles after entering intestines via diffusion (don’t need cotransport because can cross lipid membrane) ○ Packaged with proteins (in golgi) and reformed into triglycerides in the cell -> forming chylomicrons ○ Vesicles containing chylomicrons make way to basal membrane and exit cell and enter lacteal ○ Lacteal transports chylomicrons away with lymph system ■ Nucleic Acids ● Don’t think we need to worry about this ● Catabolized by pancreatic ribonucleases and deoxyribonucleases in small intestine ● Absorbed through active transport via carrier proteins ○ Water ■ 95% of water that is ingested is reabsorbed OPEN ANSWER Q’s 1. List all the transitions of epithelial mucosa from the Nose to the alveoli (respiratory) a. Nasopharynx (pseudostratified ciliated columnar) b. Oropharynx & Laryngopharynx (stratified squamous) c. Larynx ( upper is stratified squamous lower is pseudostratified ciliated columnar) d. Trachea (pseudostratified ciliated columnar) e. Bronchi (simple columnar) f. Bronchioles to alveolar ducts (simple cuboidal) g. alveoli (Simple Squamous & scattered simple cuboidal) 2. External and Internal Respiration (draw this out) 3. O2/Hemoglobin Saturation Curve (explain and draw a line) a. Temp increases -> shifts to the right b. explain 4. CO2 transport - not completed yet a. Percentages b. Whats dissolved in plasma c. What's bound to hemoglobin d. Bicarbonate e. And write reaction: CO2 + H2O --> H2CO3 -->H+ + HCO3- 5. Nervous Control of the G.I. Tract a. Intrinsic: b. Stimulus (food, stretch etc) ->receptors (chemo-mechano etc) ->local enteric nerve plexus->smooth muscle or glands create response -> response is contraction or secretion c. Extrinsic - long i. Stimulus (seeing/smelling food) ->CNS ->local nerve plexus -> smooth muscle or glands create response -> response is contraction or secretion d. Just Draw this: might want to label which is long and which is short. 6. Dalton’s Law a. Definition b. pO2 160 in atmosphere and pO2=100 in lungs because CO2 in the lungs from cellular respiration 7. Gastric Phases a. Cephalic i. Excitatory stimulus: sight, smell, taste ii. inhibitory stimulus: depression b. Gastric i. Excitatory stimulus: stomach distension (stretching) ii. inhibitory stimulus: pH lower than 2 c. intestinal i. Excitatory stimulus: Presence of partially digested food ii. inhibitory stimulus: fatty, acidic, or hypertonic chyme 8. Steps for digesting Fat (lipid digestion) a. Bile introduced to small intestine b. Fats emulsified c. Diffuses into cell d. Packaged into chylomicrons e. Transported into basement membrane f. Sent to lacteal 9. Gastric Pits of the stomach a. Mucous neck Cells ->mucus b. Parietal Cells -> HCL and intrinsic factor c. Chief cells -> pepsinogen d. Enteroendocrine cells -> gastrin, histamine, cholecystokinin 10. Central Chemoreceptors a. High CO2 in capillary and H+ is bouncing off blood brain barrier because it is charged, but CO2 can cross b. CSF (co2 +h2o -> H2CO3 -> H+ + Co3- ) in CSF V c. Receptor in the medulla d. Medulla signals for increased ventilation Henley and boyles multiple control How glucose is abosorbed in the digestive tract Hormones & volumes multiple choice Lab practical - open for 24 hours after test - 30 minutes