Anatomy 25/26

Which of the following statements is true regarding the absorption of nutrients? -80% of the sugar absorbed is fructose. -Carbohydrates are absorbed as monosaccharides. -Proteins can only be absorbed as amino acids. -Proteins can be absorbed as disaccharides. -Micelles are required for lipid absorption.

Carbohydrates are absorbed as monosaccharides Micelles are required for lipid absorption

Intestinal phase of gastric secretion

Chyme in the duodenum with a pH less than 2 or containing fat digestion products (lipids) inhibits gastric secretions by three mechanism. Sensory vagal action potentials to the medulla oblongata inhibit motor action potentials from the medulla oblongata. (mechanism 1) Local reflexes inhibit gastric secretion. (mechanism 2) Secretin, GIP, and CCK produced by the duodenum inhibit gastric secretions in the stomach.(mechanism 3)

Gastric phase of gastric secretion

Distention of the stomach activates a parasympathetic reflex. Action potential are carried by the vagus nerves to the medulla oblongata. The medulla oblongata stims stomach secretion. Distention of the stomach also activates local reflexes that increase stomach secretions.

oxidation of NADH at enzyme complex 1 establishment of a chemiosmotic gradient in the intermembrane space ATP synthase activity

ETC

T/F The role of the liver in digestion is to produce digestive enzymes.

False, the liver produces bile for fat emulsion. It is the pancreas that produces digestive enzymes.

Where is gastrin secreted from?

G cells in the antrum, just before the pylorus, of the stomach and the duodenum. Secreted in response to ingestion of a meal, distention of stomach, and production of proteins, and gastrin releasing peptide which is released by nerves of the gastric mucosa during vagal stimulation

What is Glucose-dependent insulinotropic peptide more commonly known as?

Gastric inhibitory peptide (GIP)

In order to break down protein, pepsinogen needs to be activated by what?

HCl

CCK is secreted by

I cells in the mucosa of duodenum and jejunum mainly in response to digestive products of fat, fatty acids, and monoglycerides in the intestinal contents -also produced by neurons in the enteric nervous system and is abundant in the brain

Peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system. Mainly occurs in esophagus. Occurs by contraction of circular muscles. One way motion in caudal direction. Results in high-speed propagation of food.

Which macromolecule is the target of each digestive enzyme or compound? pancreatic lipase lingual lipase maltase gastric lipase sucrase salivary amylase carboxypeptidase pepsin chymotrypsin

pancreatic lipase - L lingual lipase - L maltase - C gastric lipase - L sucrase - C salivary amylase - C carboxypeptidase - P pepsin - P chymotrypsin - P

Secondary functions of gastrin

parietal cell maturation, fundal growth, pepsinogen secretion by chief cells, stimulating pancreatic secretions and gallbladder emptying

Glycolysis begins with _____________, a step that transfers an inorganic phosphate to glucose. The priming step rearranges ____ The __________ step includes the lysis of fructose 1,6-diphosphate into two 3-C molecules. In _________, H+ atoms are removed from PGAL. Then, dephosphorylation removes ___________ groups.

phosphorylation G6P cleavage oxidation phosphate

Place these steps of glycolysis in order. phosphorylation, oxidation, cleavage, priming, dephosphorylation

phosphorylation, priming, cleavage, oxidation, dephosphorylation

Cholecystokinin (CCK) Primary function

principle stimulus for delivery of bile and pancreatic enzymes into the small intestine which stimulates the digestion of fat and proteins

where is GIP secreted from?

produced by enteroendocrine K cells which are mainly located at the duodenum and proximal jejunum. Released into circulation in response to fatty acids and amino acids and to a lesser extent, carbs. -Only hormone released by all three major types of food (LCP)

Motilin primary function

released cyclically and stims waves of GI motility called 'migrating motor complexes' which move through the stomach and small intestine every 90 min in a fasted person -sweep the stomach and small intestine clear of undigested material

zymogen

requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme. -often end in -ogen like pepsinogen

receptive-relaxation response

resists stretching briefly, but relaxes to hold more food

4 lobes of the liver

right, left, caudate, quadrate

The substance that functions to moisten the mouth, clean the teeth, inhibit bacterial growth, and aid in swallowing by moistening food is called ______

saliva

Place the layers of the esophagus in order from superficial to deep. mucosa, submucosa, muscularis externa, serosa

serosa, muscularis externa, submucosa, mucosa

_______ reflexes are stimulated by stretching or chemical stimulation of the myenteric plexus, which can result in peristaltic contractions

short

Cephalic Phase of gastric secretion

sight/thought/tactile sensations of food in the mouth stimulate the medulla oblongata. Parasympathetic action potentials are carried by the vagus nerves to the stomach. Preganglionic parasympathetic vagus nerve fibers stim postganglionic neurons in the enteric plexus of the stomach. Postganglionic neurons stimulate secretion by parietal and chief cells and stim gastrin secretion by endocrine cells. Gastrin is carried through the circulation back to stomach where it stims secretion by parietal and chief cells.

CCK is secreted by________ and stimulates secretion of the __________

small intestine, gall bladder

What organ is this? nutrient and water absorption

small intestines

Secretin is secreted by

specialized enteroendocrine cells called S cells in the mucosa of the duodenum in response to acidic gastric juice emptying into the duodenum from the pylorus of the stomach -vagal-mediated secretory response

How does CCK mediate digestion in the small intestine?

stims the acinar cells of pancreas to release digestive enzymes and stims the secretion of a juice rich in pancreatic digestive enzymes

Gastric inhibitory peptide (GIP) primary function

stimulates insulin secretion in a glucose dependent manner and inhibits gastric acid secretion and motor activity of the stomach -clears an oral load of glucose from the blood quicker than an intravenous load

Primary action of gastrin

stimulation of gastric acid secretion

Deglutition

the act of swallowing

Where are water-soluble vitamins stored?

they are not stored in the body. They are found in plant and animal foods or dietary supplements and must be taken in daily.

The process of phosphorylating glucose to convert it to G6P requires the hydrolyzation of ATP T/F

true

Receptive-relaxation is mediated by _________________

vagal motor fibers

Myenteric plexus

The myenteric plexus is the major nerve supply to the gastrointestinal tract and controls GI tract motility. According to preclinical studies, 30% of myenteric plexus' neurons are enteric sensory neurons, thus Auerbach's plexus has also a sensory component. Located between the longitudinal muscle and circular muscle of intestinal wall

Difference between short and long reflexes

The short reflex involves the direct stimulation of a postganglionic fiber by the sensory neuron, whereas the long reflex involves integration in the spinal cord or brain. The difference between short and long reflexes is in the involvement of the CNS.

Sphincter of Oddi

The sphincter of Oddi is a muscular valve that controls the flow of digestive juices (bile and pancreatic juice) through ducts from the liver and pancreas into the first part of the small intestine (duodenum)

NAD is classified as what?

a coenzyme

Water soluble vitamins are stored in the body with water TF

false

How is CCK regulated?

feedback mechanism -digestion and absorption of the molecules that stimulate CCK secretion

The sac on the underside of the liver that serves to store and concentrate bile is called the ____________

gallbladder

What organ is this? Concentration and secretion of bile

gallbladder

Where does gastrin bind?

gastric receptors found on parietal cells (HCl) and enterochromaffin-like/ECL cells (Histamine) Histamine binding to H2 receptors on parietal cells is necessary for full-blown acid secretion.

hormonal secretions like _________ and secretin are released into the blood and stimulate relatively distant parts of the digestive tract

gastrin

Conversion of glucose to G6P (phosphorylation) Conversion of G6P to fructose 1,6-diphosphate (priming) Conversion of PGAL to pyruvic acid (dephosphorylation)

glycolysis

The mucus secreting cells in the epithelium of the intestine are called ____________

goblet cells

Microscopic subunits of the liver, each consisting of a central vein passing down its core, are called __________

hepatic lobules

paracrine secretions like ________ and _________ diffuse through the tissue fluids and stimulate nearby target cells

histamine, prostaglandins

Secretin primary function

in response to acid, stims the pancreas and bile ducts to release a flood of bicarbonate base which neutralizes the acid, and the secretion of secretin is turned off

secondary functions of CCK

increased production of hepatic bile and stimulates the contraction of the gall bladder and relaxation of the sphincter of oddi, resulting in the delivery of bile into the duodenum moderately inhibits stomach contraction--this slows the emptying of food from the stomach to give time for the fats to digest in the upper intestinal tract.

What organ is this? water absorption

large intestines

Bile is responsible for the digestion and absorption of?

lipids

What organ is this? secretion of bile

liver

The cephalic phase of gastric function is controlled by what reflex?

long (vasovagal)

_________ reflexes utilize the parasympathetic nervous system, specifically, the _______ nerve

long, vagus

protein digestion and absorption The act of protein digestion begins in the mouth with _________________ digestion. Once in the stomach, ___________ hydrolyzes peptide bonds. Then, in the small intestine, trypsin, chymotrypsin and ________ continue the breakdown of proteins. The ____________ of the small intestine will finish the breakdown and begin absorption.

mechanical pepsin carboxypeptidase brush border

GIP secondary functions

mild effect in decreasing motor activity of the stomach and therefore slows emptying of gastric contents into the duodenum when the upper small intestine is already overloaded with food products

secondary functions of secretin

mild effect on motility of the gastrointestinal tract and acts to promote pancreatic secretion of bicarbonate which neutralizes acid which enhances the action of intestinal digestive enzymes. Has a direct effect on both the acinar cells and the duct cells. Also, stims pepsinogen secretion from the stomach from chief cells called "nature's antacid"

Segmentation

movement in which stationary ringlike constrictions appear at several places along the intestine and then relax as new constriction form elsewhere. -most common type of intestinal contraction -To knead or churn the contents. -mainly occurs in the small and large intestine. -occurs due to rhythmic contractions of the longitudinal muscles. -Responsible for the movement in both directions, allowing a greater mixing. -Results in slow propagation of food

What 6 things is saliva composed of (other than water)?

mucus (binds and lubricates the food bolus -electrolytes -lysozyme (enzyme that kills bacteria) -immunoglobulin A [IgA] (an antibacterial antibody -salivary amylase (an enzyme that begins starch digestion in the mouth) -lingual lipase (an enzyme that begins fat digestion in the mouth, but mainly after food is swallowed)

Do we get energy from vitamins and minerals?

no

Enteric (intrinsic) nervous system

one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract.

In the digestive system, water is absorbed through the process of _____________, following the absorption of salts and organic nutrients.

osmosis

Which of the following molecules combines with Acetyl-CoA to begin the citric acid cycle?

oxaloacetic acid

The _______ is a spongy retroperitoneal gland posterior to the greater curvature of the stomach.

pancreas

What organ is this? secretion of sodium bicarbonate

pancreas

Which of the following statements are true about gastric motility? -The stomach uses the contraction of three layers of muscle to mix, churn, and propel its contents to the duodenum. -The stomach releases up to three liters of chyme to the duodenum at a time -A typical meal is emptied from the stomach in approximately one hour. -When the pyloric sphincter is relaxed, chyme moves from the stomach to the duodenum -The receptive-relaxation response of the stomach allows it to accommodate more food.

-The stomach uses the contraction of three layers of muscle to mix, churn, and propel its contents to the duodenum. -When the pyloric sphincter is relaxed, chyme moves from the stomach to the duodenum -The receptive-relaxation response of the stomach allows it to accommodate more food.

3 functions for the contractions of the small intestine

1) Mix chyme with intestinal juice, bile, and pancreatic juice, allowing these fluids to neutralize acid and digest nutrients more effectively 2) Churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption 3) Move residue toward the large intestine

At the end of glycolysis, how many ATP molecules are gained?

2

Ratio of NADH/FADH2 to ATP

3 ATP per one molecule

how much ATP comes from 1 glucose

32

during the entire process of glycolysis, how many ATP are created?

4

Prostaglandins

A group of bioactive, hormone-like chemicals derived from fatty acids that have a wide variety of biological effects including roles in inflammation, platelet aggregation, vascular smooth muscle dilation and constriction, cell growth, protection of from acid in the stomach, and many more.

Which of the following is achieved with small intestinal muscle contractions? An increased contact of chyme with the intestinal lining. The mechanical digestion of food The mixing of chyme with secretions An increased secretion rate The propelling of contents along the intestines

An increased contact of chyme with the intestinal lining. The mixing of chyme with secretions The propelling of contents along the intestines

Which of the molecules is involved in the initiation of anaerobic fermentation? PGAL O2 NADH Lactic acid

NADH

Chyme

Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach and passed to the small intestine

Extrinsic salivary glands

Produce most saliva Parotid, submandibular, and sublingual glands

Which are the effects of insulin? Decrease cellular uptake of glucose Stimulates glucose oxidation Inhibits gluconeogenesis Stimulates glycogenesis Inhibits lipogenesis

Stimulate glucose oxidation (insulin stims glycolysis and increases the utilization of glucose) Inhibit gluconeogenesis (insulin inhibits the synthesis of glucose from amino acids) stimulates glycogenesis (stims the synthesis of glycogen from glucose in liver) it stims lipogenesis and increase cellular uptake of glucose

brush border

Surface of a cell covered with microvilli. increases surface area of a cell for absorption

how is motilin secretion inhibited?

after ingestion of food by mechanisms not yet understood -at low pH it inhibits gastric motor activity whereas at high pH it has a stimulatory effect

which of the following is a function of the digestive system? ingestion absorption defecation

all of the above

Explaining Starch Digestion in the Small Intestine The entire process of starch digestion begins in the mouth with _________. Amylase digests starch first into _____________, then into disaccharides. Disaccharides are catabolized into ____________ , which is then converted to glucose. Glucose can then be absorbed by the ___________

amylase oligosaccharides maltose small intestine

Glycolysis is an example of what metabolic reaction?

catabolic

hormones

chemical messengers secreted into blood that modify the physiology of target cells

Conversion of acetyl-CoA to acetic acid Conversion of citric acid to isocitric acid Conversion of malic acid to oxaloacetic acid

citric acid cycle

What organ is this? temporary waste storage and water reabsorption

colon

The pancreas is responsible for

digestive enzymes, bile secretion, and gall bladder contraction

The pancreatic duct brings pancreatic juice into which part of the small intestine?

duodenum

In order to improve fat digestion, large fat globules must first be dispersed into smaller droplets in a process called ___.

emulsification

Motilin is secreted by

endocrine M cells in the duodenum and jejunum during fasting,

Acinar cells

exocrine (exo=outward) cells of the pancreas that produce and transport enzymes that are passed into the duodenum where they assist in the digestion of food.

Macronutrients are absorbed into the enterocytes by what type of diffusion?

facilitated diffusion