Digestive System Flashcards

Question

Gastric Inhibitory Peptide (GIP) Origin

Answer 1

-Pancreas -Stomach -Apidose Tissue -Skeletal Muscle

Answer 2

-Stimulates release in insulin by pancreatic islets -Inhibits gastric secretion and motility -Stimulates lipid synthesis -Stimulates glucose use

Answer 3

Vagus nerve stimulation or arrival of food in the stomach. Arrival of chyme containing large quantities of undigested proteins.

Answer 4

Stomach Duodenum

Answer 5

-Stimulates production of acids and enzymes; increases mobility

Answer 6

Arrival of chyme in the duodenum

Answer 7

-Pancreas -Stomach -Liver

Answer 8

-Stimulus production of alkaline buffers -Inhibits gastric secretion and mobility -Increases rate of bile secretion

Answer 9

Arrival of chyme in the duodenum

Answer 10

-Duodenal glands -Stomach

Answer 11

Stimulates buffer secretion; inhibits acid production; dilates intestinal capillaries

Answer 12

* Analysis of food - sensory analysis of food * Mechanical digestion - through the actions of the teeth, tongue, and palatal surfaces; - includes mechanical processing and mastication * Lubrication - by mixing with mucus and saliva * Limited digestion - limited chemical digestion of carbohydrates and lipids

Answer 13

* Anatomically and functionally, the Oesophagus is the least complex section of the digestive tube. * The oesophagus begins as an extension of the pharynx in the back of the oral cavity: – It then courses down the neck behind the trachea, – through the thoracic cavity, – penetrates the diaphragm to connect with the stomach in the abdominal cavity

Answer 14

– to convey boluses of food from the pharynx to the stomach - Carries solids and liquids from the pharynx (mouth) to the stomach.

Answer 15

Distinctive features of the oesophageal wall include: – Non-keratinized, stratified squamous epithelium – Folded mucosa and submucosa – Mucous secretions by oesophageal glands – A muscularis with both smooth and skeletal muscle portions – Lacks serosa – Anchored by an adventitia

Answer 16

Muscular tube from pharynx to stomach: -Upper 1/3 ; Skeletal Muscle -Lower 2/3; Smooth Muscle Upper oesophageal sphincter: -Skeletal Muscle -Between pharynx and oesophagus Lower oesophageal sphincter: -Smooth Muscle -Between oesophagus and stomach

Answer 17

* 2400 times per day * every 40s ! * Voluntary & involuntary 1. Buccal phase 2. Pharyngeal phase 3. Oesophageal phase

Answer 18

* Voluntary * Compression of bolus (hard palate) * Tongue pushes bolus posteriorly * Soft palate lifts (nasopharanx) * Bolus enters oropharynx

Answer 19

* Involuntary/reflex * Pre-programmed all or none sequence * Bolus contacts palatal arches and uvula * Receptors relay afferents via trigeminal & glossopharyngeal nerves to swallowing centre in medulla. * Efferents to pharyngeal constrictor muscles move the bolus into the oesophagus by constricting the pharyngeal wall * Elevation of larynx, folding of epiglottis direct bolus past trachea * Respiration inhibited

Answer 20

* Involuntary/reflex * Primary peristaltic waves drives bolus down esophagus (10 s). * Secondary stronger peristaltic waves may be required. * Local stretch receptors detect distension and peristaltic contractions are modified (submucosal & myenteric plexus)

Answer 21

* Difficulty swallowing * Oropharyngeal / oesophageal – Genetic (cleft palate) – Obstructive (tumor) – Neurological (stroke) – Muscular (scleroderma) * Nasogastric tube * PEG (percutaneous endoscopic gastrostomy) tube

Answer 22

* Caused by adaptation to chronic acid exposure from reflux oesophagitis * Mucosa replaced by metaplastic columnar epithelium * Strong association with oesophageal cancer

Answer 23

* Stores ingested food * Mechanical breakdown * Secretes enzymes and acid to break chemical bonds of ingested food * Secretes intrinsic factor (IF)

Answer 24

* Located in the upper left abdomen, inferior to the diaphragm * The stomach is an expanded section of the digestive tract between the Oesophagus and Small intestine

Answer 25

* The most distal and narrow section of the stomach is termed the Pylorus * As food is liquefied in the stomach it passes through the pyloric canal into the small intestine * The wall of the stomach is structurally similar to other parts of the digestive tube * HOWEVER, the stomach has an extra, oblique layer of smooth muscle inside the circular layer * This aids in the performance of complex grinding motions

Answer 26

antrum and pyloric canal adjacent to the duodenum

Answer 27

superior, medial portion

Answer 28

portion superior to stomach- oesophageal junction

Answer 29

area between the fundus and the curve of the J

Answer 30

Guards exit from stomach

Answer 31

– Ridges and folds in relaxed stomach – In the empty state, the stomach is contracted and its mucosa and submucosa are thrown up into distinct folds called Rugae – when distended with food, the rugae are "ironed out" and flat

Answer 32

* Epithelial cells in the mucosa of the stomach are: Simple Columnar cells * A simple columnar epithelium is a single layer of columnar cells attached to the basement membrane, with oval-shaped nuclei located in the basal region. * Epithelium is towards the top of the mucosal layer of the stomach. * Mucosa of the stomach contains many other types of secretory cells.

Answer 33

1. Mucosa - Simple columnar epithelium 2. Submucosa 3. Muscularis externa - Oblique fibres - Circular fibres - Longitudinal fibres 4. Serosa

Answer 34

Mucous secretion containing several hormones

Answer 35

– Parietal cells – Chief cells -G Cells (Enteroendocrine cells)

Answer 36

Produce ghrelin; ghrelin increases before meals to initiate hunger, and decreases shortly after eating to curb hunger

Answer 37

G cells: Produce gastrin- stimulates secretion by parietal and chief cells, and contractions of the gastric wall that mix and stir the gastric contents

Answer 38

Secrete pepsinogen – inactive proenzyme; acid in gastric lumen converts pepsinogen to pepsin (protein digesting enzyme)

Answer 39

– Intrinsic factor (IF) and HCl – IF: secreted in stomach; glycoprotein that helps absorb vitamin B12 across intestinal lining – HCl – denatures proteins, breaks down cell walls, connective tissues, protection, activation of pepsin

Answer 40

–Alkaline Tide -Gastric juice pH 1.5 1. H+ produced in parietal cell by reduction of CO2 + H2O 2. H+ transported into gastric gland 3. HCO-3 diffuses into interstitial fluid via counter transport with Cl - 4. HCO-3 diffuses into circ, raising blood pH (alkaline tide) 5. Cl- diffuses into gastric gland via Cl- channels

Answer 41

The most abundant epithelial cells are mucous cells, which cover the entire lumenal surface –These cells secrete a bicarbonate-rich mucous that coats and lubricates the gastric surface –Protecting the epithelium from acid and other chemical insults

Answer 42

Hydrochloric acid is secreted from parietal cells into the lumen where it establishes an extremely acidic environment – Activates pepsinogen –Inactivation of ingested microorganisms such as bacteria

Answer 43

Pepsinogen, is secreted into gastric juice from both mucous cells and chief cells –Once secreted, pepsinogen is activated by stomach acid into the active protease pepsin, which is largely responsible for the stomach's ability to initiate digestion of proteins –In the young, chief cells also secrete chymosin (rennin) *a protease that coagulates milk protein allowing it to be retained more than briefly in the stomach

Answer 44

The principle hormone secreted from the gastric epithelium is Gastrin –A peptide that is important in control of acid secretion and gastric motility –Stimulates secretion by parietal and chief cells, and contractions of the gastric wall that mix the gastric contents

Answer 45

Cephalic phase Gastric phase Intestinal phase

Answer 46

* Prepares stomach to receive ingested material * Seeing, smelling and anticipating food perceived in the brain and the brain informs the stomach that it should prepare for receipt of a meal– directed by the central nervous system (CNS) * Parasympathetic nervous system sends a stimulus to the vagus nerve: –Resulting in release of acetylcholine (Ach) in the vicinity of G cells and parietal cells. –Binding of Ach to its receptor on G cells induces secretion of the hormone Gastrin (enteroendocrine) –Acetylcholine, histamine and Gastrin, stimulates parietal cells to secrete small amounts of acid * Additionally, a low level of gastric motility is induced

Answer 47

* Begins with the arrival of food in the stomach: – Stomach wall distension and mucosal irritation * Activation of the enteric nervous system and release of gastrin cause vigorous smooth muscle contractions. –The net result is that secretory and motor functions of the stomach are fully turned on –lots of acid and pepsinogen are secreted –pepsinogen is converted into pepsin –vigorous grinding and mixing contractions take place * However, there is a mechanism in place in the stomach to prevent excessive acid secretion - if lumenal pH drops low enough (less than about 2) –motility and secretion are temporarily suspended

Answer 48

* Controls the rate of gastric emptying * As food is liquefied in the stomach, it is emptied into the small intestine * The small intestine needs to be able to slow down gastric emptying, to allow it time to neutralize the acid and efficiently absorb incoming nutrients * Hence, this phase of gastric function is dominated by the small intestine sending inhibitory signals to the stomach to slow secretion and motility –Two types of signals are used: nervous (neural responses) and endocrine (hormonal responses). * Distension of the small intestine, as well as irritation of the mucosa leads to gastric-inhibitory impulses in the nervous system - this nervous pathway is called the enterogastric reflex. * Secondly, enteric hormones are released from cells in the small intestine and contribute to suppression of gastric activity.

Answer 49

* Brain alerts the stomach that it should expect arrival of a meal * Stomach comes out of its inter-digestive resting and begins low level motor and secretory activity (cephalic phase) * After a meal is consumed, the gastric motor and secretory activity is fully turned on (gastric phase) * If the meal is at all substantial, the gastric phase is periodically suppressed by signals from the small intestine (intestinal phase) * Eventually, the meal is fully liquefied and emptied, and the stomach falls back into a state of very low motor and secretory activity, where it remains until the next cephalic phase

Answer 50

* Ingested food reaches stomach- salivary amylase and lingual lipase continue the digestion of carbohydrates and lipids * Preliminary digestion of proteins –Pepsin: breaks down proteins into smaller peptide and polypeptide chains –Protein digestion not completed in the stomach * Carbohydrates, lipids, and proteins only partially broken down * Very little absorption of nutrients because: 1. the mucus covering the epithelial cells means that they are not directly exposed to chyme 2. the epithelial cells lack the specialized transport mechanisms of cells that line the small intestine 3. the gastric lining is somewhat impermeable to water 4. digestion has not been completed by the time chyme leaves the stomach * Some drugs (aspirin, anti inflammatory) are absorbed

Digestive System Flashcards

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