Digestive System

Question 1

four processes carried out by the GI tract

Answer 1

digestion, secretion (sending things into the digestive tract from cells) , absorption (taking things from the digestive tract lumen and taking them up into the cells), motility, excretion (leaving the body)

Question 2

where does absorption of nutrients occur?

Answer 2

in the small intestine

Question 3

Functions of the stomach

Answer 3

HCl, pepsins, mucus (protects and lubricates epithelial surface)

Question 4

Functions of the pancreas

Answer 4

enzymes, bicarbonate (neutralizes HCl entering small intestine from stomach)

Question 5

Functions of the Liver

Answer 5

bile salts (solubilize insoluble water salts), bicarbonate, organic waste products

Question 6

Functions of the gallbladder

Answer 6

stores and secretes bile between meals

Question 7

Functions of the small intestine

Answer 7

enzymes, salt and water, mucus

Question 8

Functions of the large intestine

Answer 8

mucus (lubrication)

Question 9

Gut Wall organization

Answer 9

mucosa, submucosa, muscularis externa, serosa

• absorptive cells lining the lumen and neural and muscular components below
• blood and lymph vasculature is abundant to transport absorbed nutrients
• a lot of dents to increase surface area

Question 10

Purpose of microvilli [brush border]

Answer 10

helps to further increase surface area, mucosal cells are really busy so they have a short half-life

Question 11

what is the swallowing reflex coordinated by?

Answer 11

medulla oblongata, which stimulates the appropriate sequence of contraction and relaxation in the participating skeletal muscle, sphincters, and smooth muscle groups
-pH of saliva is fairly neutral, around 7.2 (going to be secreted by the parotid glands in the mouth)
-salivary amylase is in the saliva, breaks down carbs or starchy foods
-lingual lipase starts to work on fats and lipids
-when swallow food, want epiglottis to swing shut on trachea
-digestive tract is typically full of sphincters
-upper esophageal sphincter is typically closed, when swallow food, it will open and allow it to go down to the esophagus and then it won’t come up, except in babies
-

Question 12

Major functions of saliva

Answer 12

1) moistens and lubricates food
2) digestion of polysaccharides by amylase
3) dissolves food
4) antibacterial actions

Question 13

what is necessary to deliver swallowed food to the stomach?

Answer 13

the coordinated sequence of contraction and relaxation in the upper esophageal sphincter, esophagus, and the lower esophagea sphincter

Question 14

specialized cells in the stomach synthesize and secrete mucous fluid, enzyme precursors, HCl, and hormones

Answer 14

Body (secretes mucus, pepsinogen, and HCl)

Antrum (secretes mucus, pepsinogen, and gastrin)

Question 15

Cells of the stomach

Answer 15

1) mucous cells (goblet cells)-secrete mucous
2) Parietal cells (secretes HCl and intrinsic factor)/ intrinsic 3)factor helps with B-12 absorption
4) Chief cells (secrete pepsinogen), secrete gastric lipase
5) Enteroendocrine cells (G cells)- secrete gastrin, stimulates stomachache, gastrin triggers cell growth, allows food to enter stomach

Question 16

Ulcer

Answer 16

isn’t caused by stress, but stress can aggravate ulcers, about 70% of ulcers are caused by H. pylori, antibiotics help with this

Question 17

What does acid production by the parietal cells depend on?

Answer 17

• Depends on the generation of carbonic acid, subsequent movement of hydrogen ions into the gastric lumen results from primary active transport
• pump hydrogen in and exchange it for potassium, potassium going down concentration gradient from cell to lumen
• can help to buffer the blood to allow bicarbonate to enter and exchange it for chlorine ion
• ion going against concentration from blood to stomach cells (secondary active process)

Question 18

What converts pepsinogen to pepsin?

Answer 18

• the acidity in the gastric lumen
• subsequent conversions occur quickly as a result of pepsin’s protease activity
• pepsin=protein digester, enzymatic activity, pepsin=chemical digester, but HCl is not an enzyme

Question 19

Describe peristalsis

Answer 19

• waves of smooth muscle contraction mix and propel the ingested contents of the gastric lumen, but only a small amount of the material enters the small intestine (duodenum) as a result of each wave cycle)
• in addition to enzymes breaking down food, stomach will actually contract at regular intervals, churn/mix food, churning helps the enzymes to interact more effectively
• pyloric sphincter is opening and closing rhythmically in response to the pressure by food
• protein tends to stay longer in the stomach than watermelon
• alcohol and caffeine are absorbed in the bloodstream

Question 20

About how much of the cholesterol-based bile salts are “recycled” by reabsorption along the intestine?

Answer 20

• about 95%

- liver functions: helps to detoxify the blood, detoxifies drugs, urea, etc

Question 21

What does liver do to carbs?

Answer 21

• can store glycogen, if sugar is needed, can break glycogen down
• lipid metabolism: synthesizes cholesterol, can make other things as well, stores fat
• protein metabolism: synthesizes albumin, can detoxify ammonia
• bile or bile salts function, emulsification of fats, helps to increase surface area of the fats so that lipases can work more efficiently

Question 22

Bile Salts Functions

Answer 22

-non-polar surface helps emulsify fats, polar surface helps promote water solubility

Question 23

Fats and how they are distributed throughout the body

Answer 23

• start with big droplets of fat
• turn into small droplets of fat
• micelles
• fatty acids and chylomicrons
• chylomicron assembly

Question 24

What are digestive secretions mostly composed of?

Answer 24

• mostly water
• only 100 ml are excreted in feces, mechanisms for water absorption are efficient
• reasonable percentage of what is secreted each day: 1.6%

Question 25

Properties of Gastrin

Answer 25

- chemical class: peptide - site of production: antrum of stomach - stimulus for hormone release: amino acids, peptides in stomach, parasympathetic nerves - stimulates acid secretions, motility, and growth - stimulates growth of exocrine pancreas - stimulates ileum motility and small intestine growth

Question 26

Properties of CCK

Answer 26

- chemical class: peptide - site of production: small intestine - stimulus for hormone release: amino acids, fatty acids in small intestine - inhibits stomach acid secretions and motility - potentiates secretin's actions - stimulates gallbladder contractions, - relaxes sphincter of Oddi

Question 27

Properties of Secretin

Answer 27

- chemical class: peptide - site of production: small intestine - stimuli for hormone release: acid in small intestine - inhibits acid secretions and motility in the stomach - stimulates bicarbonate secretion, and growth of exocrine pancreas

Question 28

Properties of GIP

Answer 28

- chemical class: peptide - site of production: small intestine - stimuli for hormone release: glucose, fat in small intestine - GIP stimulates insulin secretion

Question 29

How are digestive secretions from the liver and pancreas delivered into the duodenum of the small intestine?

Answer 29

- through the sphincter of Oddi - Entrance to small intestine from gall bladder is guarded by the sphincter of Oddi (sphincter is guarded by pressure or gallbladder secretions) - bile produced in liver->bile ducts->merge into the common hepatic duct->common bile duct->cystic duct

Question 30

what will people without gallbladder experience?

Answer 30

- going to have hard time digesting fats, just can't store fats - causes of gallstones: risk factors: fertile women (20-30), older than 50

Question 31

What role do exocrine cells in the pancreas play?

Answer 31

- they play a central role in the production of digestive enzymes - exocrine (secrete enzymes for digesting) vs endocrine cells, endocrine cells (alpha and beta) beta secretes insulin (peptide based hormone secreted in response to high glucose levels) - alpha cells secrete glucagon (released when blood glucose is gone, in response to low glucose levels), glucose released from the liver - duct cells secrete a lot of bicarbonate - small intestine is lined with brush border and cells that secrete enzymes

Question 32

What would happen if digestive enzymes were synthesized in their active form?

Answer 32

- they would digest the very cells that make them | - Hence, inactive precursors (trypsinogen become activated (trypsin))

Question 33

Where are secretin's receptors found?

Answer 33

-the receptors respond with additional bicarbonate delivery, gastric motility and secretion are inhibited

Question 34

What happens when there is increased amount of acid from the stomach?

Answer 34

- increased amount of acid from stomach stimulates Secretin secretion from the small intestine - increase in plasma secretin - increase in Bicarbonate secretion from pancreas - increase in the flow of bicarbonate into small intestine - neutralization of intestinal acid in small intestine - CCK takes pancreas to send enzymes

Question 35

Where are CCK's receptors located?

Answer 35

- they are located in the pancreas, which responds with additional enzyme delivery - in the gallbladder contracts to deliver more Bile - in the sphincter of oddi, which relaxes to facilitate delivery of the enzymes and bile salts

Question 36

What happens with too much intestinal fatty acids and amino acids?

Answer 36

- increase in intestinal fatty acids and amino acids leads to increase in CCK secretion in the small intestine - increase in plasma CCK - increase in enzyme secretion from pancreas - increase in flow of enzymes into small intestine - increase in digestion of fats and proteins

Question 37

lactose intolerance

Answer 37

- inability to breakdown lactose, either don't have enough lactase or eating too much dairy -> become more lactose sensitive - Symptoms: lactose stuck in digestive tract as an osmotic solute, feces becomes more liquidy, if lactose stays in there for too long, it will become to ferment because different enzymes eat it and it becomes gaseous

Question 38

What does CCK stimulate?

Answer 38

-stimulates the gallbladder, responds by contracting and delivering more bile to the duodenum through the sphincter of oddi, which relaxes (opens) in response to CCK

Question 39

What happens when there is increase of fatty acids in duodenum?

Answer 39

- increase in CCK secretion - increase in plasma CCK - causes gallbladder to contract and that increases bile flow into the common bile duct - causes sphincter of oddi to relax and that causes increase of bile flow into duodenum.

Question 40

What are the primary activities in the large intestine?

Answer 40

-active transport of sodium coupled with osmotic absorption of water -microbes here are active in the production of vitamin K -ileocecal valve responds to pressure, but is keeping environment of small intestine from large intestine -e.coli from large intestine can cause sickness -function of large intestine: does a lot of absorbing, absorbing water, controlling water, uptake of sodium, water follows -bacteria living in large intestine are helpful in producing vitamins -

Question 41

Purpose of video endoscopy:

Answer 41

- helped to greatly enhance understanding of normal processes in the gut and reveals complications resulting from disease, such as colon cancer - colon is part of the digestive tract that is susceptible to cancerous growths or tumors - why is pancreatic cancer harder to treat than colon cancer? if pancreas breaks, going to have some trouble, not a lot of pancreatic transplants - lack of symptoms, but often caught accidentally at an earlier stage, not diagnosed until very late

Question 42

"Feasting" (insulin present)

Answer 42

1) synthesis 2) glucose 3) storage molecules food is in the digestive tract and insulin is present to to absorb glucose

Question 43

Fasting ( insulin absent)

Answer 43

1) catabolism 2)diverse fuels 3)gluconeogenesis fasting- there is no food in the digestive tract, "hungry"

Question 44

what happens when insulin becomes sensitive to increased glucose levels?

Answer 44

-increase in plasma glucose -causes increase in insulin secretion from pancreatic islet beta cells -increase in plasma insulin -can either cause increase in glucose uptake from adipocytes and muscle, cessation of glucose output, net glucose uptake -restoration of plasma glucose to normal (once glucose returns to normal, stop secreting insulin (negative feedback loop)

Question 45

what causes increased secretion of pancreatic islet beta cells?

Answer 45

- increased plasma glucose - increased plasma amino acids - glucose-dependent insulinotropic peptide (GIP) - parasympathetic activity - sympathetic secretion causes decreased stimulation of the beta cells - GIP acts on beta cells and tells beta cells to secrete insulin

Question 46

When is cholesterol synthesis by the liver upregulated?

Answer 46

- when dietary cholesterol is decreased and vice versa - most of the dietary cholesterol goes to GI tract and is excreted or goes to plasma cholesterol - synthesis of cholesterol from liver, GI tract, and other cells->plasma cholesterol in lipoproteins - leads to secretion of bile in the liver, catabolism to bile salts -> GI tract - plasma cholesterol (lipoproteins) leads to incorporation into membranes, steroid hormones

Question 47

What do fat cells secrete?

Answer 47

- Fat cells, also known as adipocytes, synthesize and secrete protein called leptin - leptin=putative hormone that acts on the central nervous system to reduce appetite in person with adequate energy reserves - energy intake->energy expenditure->increased fat deposition in adipose tissue->increase in leptin secretion->increase in plasma leptin concentration->causes altered activity of integrating centers from the hypothalamus-> causes decreases in energy intake->increase in metabolic rate

Question 48

How does hunger influence various functions in the body?

Answer 48

- palatability of food can increase hunger - stress can decrease or increase hunger - conditioned responses can increase or decrease hunger - increase in plasma glucose decreases hunger - increase in plasma insulin decreasses hunger - increase in blood glucagon decreases hunger - plasma GI hormones decreases hunger - increase in plasma leptin decreases hunger - increase in plasma ghrelin increases brain hunger - increase in body temperature decreases hunger - activation of stretch receptors and chemoreceptors in stomach and duodenum

Question 49

What is the circadian rhythm of body temperature?

Answer 49

-persists even among patients in a coma; in addition to this basic rhythm, fevers, exercise, and other activities can alter the body temperature