PGY 451 EXAM 3 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026

PGY 451 EXAM 3 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026 Digestive System 6 Basic FUnctions - Answers 1. motility 2. Secretion 3.Digestion 4.Absorption tp blood 5.Excretion 6.Protection- how to make sure inside shit is seperated from inside shit General Anatomy of GI System - Answers esophagus connects mouth to stomach esophageal sphincters regulate the movement of food to and from esophagus to stomach. stomach has the Pylorus that regulates the stomach shit to intestine Sphincter of Oddi is the opening to the small intestine which goes to colon through Ileocecal valve then to internal/external sphincter *liver and pancreas in charge of secretion and help in digestion General Organization of the layers composing of the GI walls - Answers inside to out *Villus- makes large surfaced area though folding *Epithelium- absorbs nutrients from digestion and single layer of cells *Muscular Mucosa- streaches and contracts to play with surface area and move shit *Lymphnodes- Protective gland secretion *Submucosa- contains muscle layer made of circular (inner) and longitudinal (outer) and Serosa in stomach List the sections of the small intestine and colon in order.. - Answers Small intestine: duodenum -- jejunum -- ileum Colon: Ascending -- transverse -- descending -- sigmoid -- rectum What controls GI physiology? regulation mechs - Answers Endocrine: hormones go through circulation then act on GI tract Neurocrine: tends to be more localized. The enteric nervous system controls the GI tract while the ANS/CNS tends to be more modulatory. info about food is sent to CNS and then CNS sends signals to ENS which acts on GI tract Paracrine: cells secrete particles that will act on adjacent cells, does not need to go into circulation. Gut Stimuli evoke what digestive responses - Answers Stimuli-- Sensors (Mech and Chem) can go to 2 paths 1)Brain and spinal cord to Enteric NS 2) can directly go to Enteric NS which sends signals -- Effectors (motility, Secretion, Blood Flow) Enteric NS is located within the wall of the GI tract What are the two important functions of GI motility? - Answers -The movement of food from the mouth to the anus -Mechanically mixing food to break it into smaller particles and to mix with digestive juices What muscles types are involved in GI motility and where are they found along the tract? - Answers -Muscles of mouth, pharynx, upper esophagus and external anus sphincter are striated and innervated by somatic motor neurons. -Muscles of the rest of the GI tract are smooth and innervated by autonomic neurons. What processes are involved in GI motility? - Answers Ingestions: taking food into the mouth Mastication: chewing the food and mixing it with saliva Deglutition: swallowing the food Peristalsis and segmentation: rhythmic wavelike contractions (peristalsis) and mixing contractions in different segments (segmentation) move food through the GI tract. Defecation: elimination of solid, semisolid and/or liquid waste from the GI tract via the anus What are some general characteristics of GI smooth muscle? - Answers It is involuntary non-striated muscle. It contracts spontaneously, driven by pacemakers. The cells are electrically connected by gap junctions. Different regions exhibit different types of contraction these can be Tonic contractions or Phasic Contractions. They have slow wave potentials What are tonic and phasic contractions? - Answers Tonic contractions- the muscle stays contracted for a long period of time Phasic contractions- the muscle contractions change Describe slow wave potentials and the intersitial cells of Cajal (ICC).. - Answers ICC's are modified cells where slow waves are initiated through electrical contacts with smooth muscle they effect the RMP of them. They're pace maker cells. slow wave in stomach 3-5 per min, in small intestine 12-20 per min and in colon 6-8 per min. Amplitude and frequency of the slow wave are modulated by extrinsic and intrinsic nerves and hormones (excite- ach, sub. p and inhibit- VIP, NO). Not all slow waves result in contraction. Contraction will occur when threshold is reached. Muscle contraction and ICC's... - Answers Muscle contractions in smooth muscles are being coordinated by basic electrical rhythm that us generated by ICC's. These cells are found in the interstitium but connect up to the smooth muscle. They're electrically active. They're giving that electrical signal to the smooth muscle and because smooth muscles are interconnected through gap junctions they all behave as if they were one. Describe contraction of smooth muscle.. - Answers An AP is elicited in the smooth muscle causing it to depolarize and open up calcium channels. Ca2+ comes in from outside the cell and from the sarcoplasmic reticulum. Ca2+ then binds to calmodulin (CaM) which puts it into its active state Ca2+-CaM then acts on and activates myosin light chain kinase (MLCK). MLCK then phosphorylates myosin, activating it. Active myosin will now interact with actin causing contraction.Once the phosphates are removed from myosin it will no longer interact with actin and the muscle will relax. What are the three motor patterns of the small intestine and describe them? - Answers Peristalsis, segmentation and migrating motor complex (MMC). peristalsis and segmentation are active during migration of a meal with MMC occurs after/ in between meals. Peristaltic contractions create forward movements and segmental contractions are responsible for mixing and have no net forward movement. MMC is a strong set of contractions that force whatever is left over in the small intestine out. This is why the small intestine does'nt have many bacteria. What does chewing serve to do? - Answers mis food with saliva to lubricate and facilitate swallowing. Reduces size of food particles to facilitate swallowing. Mixes ingested carbohydrates with salivary amylase to begin carbohydrate digestion. Is chewing and swallowing involuntary or voluntary? - Answers Chewing is largely an evoked reflex initiated by food in the mouth (mechanoreceptors sense food in the mouth relay the information to the brainstem which results in the orchestration of reflex oscillatory pattern of muscles involved in chewing) but it can be modified, we can speed up, slow down, start or stop. Swallowing you can start but cant stop it. Reflex portion is controlled by the swallowing center in the medulla evoked by presence of food in the mouth. Vagus and glossopharyngeal nerves provide both afferent and efferent pathways between sensory neurons, swallowing center and the striated muscle in the pharynx and upper esophagus. What are the three phases of swallowing describe the? - Answers -Oral, pharyngeal and esophageal. Oral phase: 1)muscles of mouth and tongue mix food with saliva and create a bolus of food to be swallowed. 2)skeletal muscles pushed food to back of oral cavity. Pharyngeal phase: 1) complex reflex involving nerve coordination of skeletal muscle. 2) Closes epiglottis, opens upper esophagus,and propels food into the esophagus Esophageal phase: 1) UES opens, bolus of food enters the esophagus UES closes. 2)Primary peristaltic contractions force the bolus of food down the esophagus. 3) LES opens by peptidergic fibers in the vagus nerve that release VIP. 4)Orad region of the stomach relaxes by receptive relaxation. The oropharyngeal (oral and pharyngeal) stage is the last voluntary act in processing food until the anal end of the GI tract. What is receptive relaxation? - Answers The stomach expands to adjust for the meal coming in. It swells up at constant pressure. What controls GI motility? - Answers GI hormones (CCK, Motilin) and Neural activity (extrinsic and intrinsic) Describe CCK in respect with motility.. - Answers CCK is released in response to chyme coming into the duodenum from the stomach. It is secreted by endocrine I-cells of the duodenum. Receptors for CCK are found throughout the GI tract. It inhibits gastric emptying (tells the pyloric valve to close and stop sending chyme in, eventually CCK stops being secreted and another bolus of chyme will be released starting the process over again) and stimulates intestinal and colonic motility. Describe motilin.. - Answers Motilin is secreted my endocrin M-cells found in the crypts of the small intestine. High levels are secreted between means. It stimulates MMC. Housekeeper of the gut Describe how neural activity controls GI motility.. - Answers -Intrinsic regulation is done by the myenteric plexus (ENS) when it releases Acetylcholine or substance P it excites but when it releases VIP or NO it inhibits. -Extrinsic regulation is done by the ANS. The parasympathetic branch tends to excite while the sympathetic branch tends to inhibit. What are the seven sphincters along the GI tract and where are they located? - Answers 1.Upper esophageal (striated muscle)-mouth to esophagus-voluntary control 2.Lower esophageal (smooth muscle)-esophagus to stomach 3.Pyloric (smooth)- stomach to small intestine 4.Illeoceceal (smooth)- small intestine to colon- squirts small amount into colon and opens door due to pressure 5.Internal anal (smooth)- colon to rectum 6.External anal (striated)- rectum to outside 7.Oddi (smooth)- pancreas, gallbladder, liver secretions to small intestine, duodenum after brunners gland. Movement from major sections to the next is inhibited/blocked by distinct control passages or sphincters. When ingesting a meal we will deal with what activities? - Answers Motility, secretion, digestion, and absorption Describe the cephalic phase of ingesting a meal.. - Answers It causes the activation of the GI tract to receive a meal (preparing or getting ready for a meal). Thinking, seeing, smelling of a meal can stimulate the beginnings of preparing the stomach to accept a meal. There is an increases excitatory parasympathetic outflow to the gut. Describe the oral phase of ingesting a meal.. - Answers The events that occur in response to food actually in the mouth. The physical presence of food generates specific signals sensed by mechanoreceptors and chemoreceptors (gustatory receptors and nociceptors). In this phase we activate the reflex of chewing (mechanical disruption that breaks the food into smaller particles and mixes food partibles with salivary secretions). General Properties of secretion of GI - Answers -secretion comes from Salivary glands, Pancreas, Liver, glands of the gut wall, and from intestinal mucosa -secretory products vary with function -most products contain water, electrolytes, Proteins, signaling molecules (hormones) -some mucosa can come directly from gut Describe a general exocrine gland.. - Answers It is a duct structure lined by a single layer of epithelial cells. These cells control movement from lumen to intercellular to interstitial areas. The cells in the blind end are called acinar cells while the cells in the narrow duct portion are call duct cells. These cells have an apical side facing the lumen and a basolateral side facing the interstitial area. Tubuloalveolar Gland - Answers Salitory gland that produces salivary amylase, RNase, DNase, Lysosomes(protective agents against bacteria), lingual lipase(attacks lipids) , IGA( protective function in saliva) What are the major salivary glands? - Answers The parotid, submandibular and sublingual. There are also many buccal glands found throughout the mouth that secrete the mucus associated with saliva. -Parotid is very large and makes most of the digestive products How is salivary secretion controlled? - Answers It is exclusively controlled by neural activity, no hormones involved. It is stimulated by both the parasympathetic (more dominant) and sympathetic branches of the ANS. *Para- Conditioning, food, nausea and smell will cause an excitatory outflow from the parasympathetic branch neurons will release more Ach onto muscarinic receptors of the acinar or ductal cells causes an increase in intercellular Ca2+ and IP3 and secretion will increase. - Dehydration, fear and sleep will cause an inhibitory outflow from the parasympathetic branch (releases less Ach -- less saliva secreted). *When the Sympathetic branch is stimulated it will release NE onto the acinar or ductal cells causing an increase in cAMP and an increase in salivary secretion. What are the components of salivary secretion? - Answers *Electrolytes (Na+, K+, HCO3-, Ca2+, Mg2+, Cl-) *mucin (the functional unit of mucus its a complex structure of glycoproteins, its what makes saliva slippery) *enzymes (amylase- breaks down carbohydrates, lipase- fat digestion) *protective substances (lysozyme- antibacterial function, *immunoglobin- has an immunoresponse, lactoferrin- binds up iron in a meal making it unavailable to bacteria) Very high flow rate in blood is needed because we can produce a lot of saliva very quickly General Characteristics of epithelial Transport - Answers *Half of cell pumping is done to keep the Na+ gradient low. Na+/K+ gradient work together to create majarity of energy to do work. *Epithelial cells are polarized by themselves- one side of cell will have different pumps than the other *Tight junction controls movement between each Epithelial cell. -junctions are generally tight/leaky in gut Describe the ion transport in the acinar cells of a salivary gland.. - Answers K+, HCO3- and Cl- are secreted out into the lumen on the apical side. Na+ travels through the paracellular pathway to reach the lumen as well. On the basolateral side there is the Na+, K+ ATPase, a K+ channel (lets K+ leave down its gradient), secondary active transporter that couples Na+ movement down its gradient into the cell pushing H+ out of the cell, Na+ 2Cl- and K+ also all diffuse in cell. The fluid in the lumen near the acinar cells is almost isotonic to plasma meaning it has the same osmotic properties even though the composition is differnt Describe ion transport in the ductal cells of a salivary gland.. - Answers On the apical side Na+ and Cl- are reabsorbed (HCO3- is pushed out while Cl+ is pushed in, K+ out while Na+ is pushed in). This adds to the HCO3- and K+ that are already in the lumen from the acinar cells but takes away the Na+ and Cl- that was put in the lumen from acinar cells. The solution in the lumen near the ductal cells becomes more dilute and hypotonic because of this.