Ch. 22 Digestive System

why is lipid absorption more complex than carbohydrate or protein absorption?

lipids are non polar and clump together

how do the muscularis externa and mucosa in the esophagus differ from the tissues in most of the alimentary canal?

they do not only consist of smooth muscle

what will happen to supplemental digestive enzymes in the stomach after they're ingested

they will probably be damaged and denatured by the acid in the stomach and pepsin will begin digesting them into smaller polypeptides

how does protein digestion occur in the small intestine

trypsin and brush border enzymes break down proteins into oligopeptides and free amino acids to be absorbed

steps of defecation reflex

1) stretch receptors transmit sensation of rectal distention to the spinal cord 2) parasympathetic neurons cause smooth muscle in the sigmoid colon and rectum to contract, and the internal anal sphincter to relax 3) impulses from the cerebral cortex trigger relaxation of the external anal sphincter and contraction of the levator ani muscle, allowing feces to pass out of the body

what are the primary triggers for bile release

CCK triggers contraction of smooth muscle in the wall of the gallbladder and causes it to release bile into the cystic duct

what hormones and neural stimuli trigger the gastric phase?

ENS and vagus nerve increase acid secretion

what do parietal cells produce

HCl and intrinsic factor

what do mucous neck cells produce

acidic mucus

which cells secrete pancreatic juice and what are its components

acinar cells; consists of water, bicarbonate, and digestive enzymes

where does protein digestion begin, and with which enzyme

begins in the stomach with pepsin

where is the peritoneal cavity located?

between the visceral and parietal peritoneum

what are the 3 phases of acid secretion in the stomach

cephalic phase, gastric phase, intestinal phase

which structures form the lateral, anterior, and superior walls of the oral cavity?

cheeks, lips, and hard/soft palate

segmentation

churning movement

what hormones and neural stimuli trigger the intestinal phase

chyme in duodenum stimulates acid secretion; enterogastric reflex decreases acid

what is the role of bile salts in lipid digestion

emulsification in the small intestine

what are the mineral and non mineral components of the tooth?

enamel, dentin and cementum are mineral

which branches of the nervous system supply the digestive organs?

enteric nervous system and 2 branches of autonomic nervous system

describe parasympathetic reflex arc that stimulated salivation

facial and glossopharyngeal nerves release ACh onto acinar cells which trigger release of saliva

how are amino acids absorbed across the apical and basal enterocyte membranes

facilitated diffusion

how do glucose, galactose, and fructose cross the apical enterocyte membrane

glucose and galactose - secondary active transport Na+/glucose cotransporter fructose - facilitated diffusion

what is a portal triad

hepatic arteriole, portal venule, and bile duct

where does the blood from the abdominal digestive organs drain?

hepatic portal vein to the liver (splanchnic circulation)

what do enteroendocrine cells produce

hormones for digestion (gastrin)

would bile salts be effective if they were polar molecules instead of amphiphilic molecules? what if they were non polar molecules?

if polar, they would be unable to interact with lipids. if non polar, they would be unable to interact with water

where does lipid digestion begin and with what enzyme?

in the stomach by gastric lipase

why is the internal surface of the small intestine arranged into progressively smaller folds

increases surface area for absorption (circular folds, villi, microvilli)

what are the 6 basic processes of the digestive system

ingestion, secretion, propulsion, digestion, absorption, and defection

how do the internal and external anal sphincters differ

internal is involuntary and external is voluntary

The weight loss drug orlistat, available OTC under the name All, blocks the activity of pancreatic lipase. Predict the effects of this drug. Why might it help a person lose weight?

it blocks chemical digestion of lipids and therefore their absorption, this decreases the amount of dietary fat the body absorbs; could lead to deficiency of fat-soluble vitamins

how do CCK and secretin affect pancreatic secretion

mediate pancreatic secretion during meals

motility of small intestine between meals

migrating motor complex

what would happen to the motility of the stomach if the vagus nerve were cut

motility would decrease; the migrating motor complex in the small intestine would still function but peristalsis and segmentation would diminish

where does carbohydrate digestion take place?

mouth and small intestine

in which parts of the alimentary canal does chemical digestion take place

mouth, stomach, and small intestine

what are the four main tissue layers of the alimentary canal?

mucosa, submucosa, muscular externa, and serosa

what are the primary cell types of the gastric glands?

mucous neck cells, parietal cells, chief cells, enteroendocrine cells

primary digestive function of the pharynx? which muscles carry out this function?

muscles contract during swallowing and propel the bolus inferiorly (pharyngeal constrictor muscles)

which enzymes catalyze reactions that digest nucleic acids?

nucleases and brush border enzymes

how is water absorbed in the small and large intestines

osmosis

what are the 3 types of paired salivary glands and where are they located

parotid glands (masseter muscle), submandibular glands, sublingual glands

what do chief cells produce

pepsinogen

where is the esophagus located and what are its major functions

posterior to the trachea; waves of peristalsis massage the food inferiorly

how do the primary dentition and secondary dentition differ?

primary - 20 teeth, 6 months to 24 months secondary - 32 teeth

how do accessory organs assist digestion

produce and secrete digestive enzymes

what functions are performed by normal flora in the colon

produce vitamins, metabolize undigested materials, deter the growth of harmful bacteria, stimulate the immune system

what are the main functions of the liver

production of bile (nutrient metabolism, detoxification, excretion, production of plasma proteins, and storage of nutrients)

peristalsis

propulsive movement

what are the main functions of the gallbladder

receives and stores bile

3 functions of gastric motility

receptive function, churning function, and emptying function

which type of epithelium makes up the mucosa from the stomach to the end of the large intestine?

regenerative epithelial cells

The treatment for pancreatic cancer may require removing the pancreas. Predict the consequences of this procedure for the body's digestive functions.

removal of the pancreas would severely impact chemical digestion; supplementary digestive enzymes would need to be administered

which enzymes are involved in digesting carbohydrates

salivary amylase, pancreatic amylase, lactase, maltase, and sucrase

how does the endocrine system regulate digestive processes?

secretion of hormones

what type of movements occur in the proximal large intestine

segmentation and mass movements

motility of small intestine during eating

segmentation and peristalsis

how is sodium ion absorption achieved

sodium is absorbed by cotransport with monosaccharides and amino acids

A patient needs a medication that is normally given at a dose of 500 mg by mouth every 8 hours. However, the patient has liver disease, and the pharmacist recommends giving the drug at a dose of 250 mg every 12 hours instead. Explain why the pharmacist made this recommendation.

the liver will metabolize the drug less efficiently, prolonging the life of the drug in the blood so a lower dose is needed

are supplemental digestive enzymes likely to be useful?

they are fairly useless as the enzymes will be rendered nonfunctional in the stomach

what hormones and neural stimuli trigger the cephalic phase?

vagus nerve stimulates parietal cells, histamine and gastrin are released and somatostatin is inhibited

what are the components of saliva and what are its functions

water, mucus, salivary amylase, lysozyme, and IgA; it moistens food and assists in mechanical and chemical digestion