Bio #9 Flashcards
1
Q
what are the two types of digestion in the body?
A
intracellular digestion and extracellular digestion
2
Q
intracellular digestion
A
part of metabolism, involves the oxidation of glucose and fatty acids for energy.
3
Q
extracellular digestion
A
occurs within the lumen of the alimentary canal (runs from the mouth to the anus and is sectioned off by sphincters, circular smooth muscles around the canal that can contract to allow compartmentalization of function).
Technically outside the body
4
Q
sphincters
A
circular smooth muscles around the canal that can contract to allow compartmentalization of function).
5
Q
alimentary canal
A
runs from the mouth to the anus
6
Q
what are the two roles of the human digestive tract?
A
digestion and absorption
7
Q
digestion
A
involved the breakdown of food into its constituent organic molecules: starches and other carbohydrates into monosaccharides, lipids (fats) into free fatty acids and glycerol, and proteins into amino acids.
Mechanical digestion: the physical breakdown of large food particles into smaller food particles but does not involve breaking chemical bonds.
Chemical digestion: the enzymatic cleavage of chemical bonds, such as the peptide bonds of proteins or the glyosidic bonds of starches.
8
Q
absorption
A
involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body’s tissues and cells.
9
Q
mechanical digestion
A
the physical breakdown of large food particles into smaller food particles but does not involve breaking chemical bonds.
10
Q
chemical digestion
A
the enzymatic cleavage of chemical bonds, such as the peptide bonds of proteins or the glycosidic bonds of starches.
11
Q
what are the steps of the digestive tract
A
o Begins with the oral cavity (mouth)
o Followed by the pharynx which is a shared pathway for food and air
o Food then enters the esophagus which transports it to the stomach.
o To small intestine and then large intestine.
o Waste products are stored in the rectum, until they are released.
12
Q
what are the accessory organs to the digestive tract?
A
o Salivary glands
o Pancreas
o Liver
o Gallbladder
13
Q
what is the enteric nervous system?
A
collection of neurons that govern the function of the GI system.
o Present in the walls of the digestive tract and trigger peristalsis, the rhythmic contractions of the gut tube, in order to move materials through the system.
o Can function independently of the brain and spinal cord but is influenced by the sympathetic and parasympathetic nervous systems.
Parasympathetic nervous system increases secretions from exocrine glands and promotes peristalsis.
14
Q
ADH and aldosterone trigger ____
A
thirst
15
Q
glucagon and ghrelin stimulate ____
A
hunger
16
Q
leptin and cholecystokinin stimulate _____
A
satiety
17
Q
the process of digestion spans ___
A
the oral cavity, esophagus, stomach, first part of the small intestine the duodenum
18
Q
oral cavity has what types of digestion?
A
mechanical and chemical digestion
19
Q
mechanical digestion in oral cavity
A
o Mechanical: teeth, tongue, and lips
Mastication: chewing
Increases the surface area to volume ratio of the food and reduces it in size so that it will not obstruct the beginning of the alimentary canal.
saliva ==> moistening food
20
Q
mastication
A
chewing
21
Q
chemical digestion in oral cavity
A
o Chemical digestion relies on the enzymes from saliva produced by the three pairs of salivary glands.
Saliva also aids mechanical digestion by moistening and lubricating the food.
Salivary glands are innervated by the parasympathetic NS when there is food in the oral cavity (also by sight and smell)
Saliva contains:
• Salivary amylase: hydrolyzes starch into smaller sugars (maltose and dextrins)
• Lipase: hydrolysis of lipids.
Does not occur for long because the food is swallowed
22
Q
salivary glands are innervated by the _____
A
parasympathetic NS
23
Q
saliva contains ______
A
salivary amylase and lipase
24
Q
salivary amylase
A
hydrolyzes starch into smaller sugars (maltose and dextrins)
Salivary amylase in the mouth has a higher specificity for rapidly soluble starches,
25
lipase
hydrolysis of lipids
26
Salivary amylase in the ____ has a higher specificity for ____, while pancreatic amylase (____) has a higher specificity for ______ starches.
mouth, rapidly soluble starches
| small intestine, less soluble, more nonpolar
27
bolus
formed by the tongue, forced into the pharynx and swallowed
28
pharynx
leads from the mouth and posterior nasal cavity to the esophagus.
o Can be divided into 3 parts:
Nasopharynx: behind the nasal cavity
Oropharynx: at the back of the mouth
Laryngopharynx: above the vocal cords
o Epiglottis: prevents food from entering the larynx.
29
epiglottis
prevents food from entering the larynx.
30
esophagus
: a muscular tube that connects the pharynx to the stomach.
o Top 1/3 is skeletal muscle, bottom is smooth muscle, and middle is a mix of both.
Top is under somatic control while the rest is autonomic control
31
peristalsis
rhythmic contraction of smooth muscle that propels food toward the stomach (or toward the mouth during vomiting?
32
what type of muscle is the esophagus made out of
o Top 1/3 is skeletal muscle, bottom is smooth muscle, and middle is a mix of both.
Top is under somatic control while the rest is autonomic control
33
emesis
vomiting (peristalsis toward the mouth rather than the stomach)
34
upper esophageal sphincter
o Swallowing is initiated in the muscles of the oropharynx
muscles of the oropharynx (at the back of the mouth)
35
lower esophageal sphincter
also known as cardiac sphincter
| : near the stomach, opens to allow food into the stomach.
36
esophagus and digestion
No digestion occurs in the esophagus other than what was initiated in the mouth (very little)
37
the stomach is highly _____
acidic/muscular
38
what are the 4 main divisions of the stomach?
Can be divided into 4 main divisions: the fundus and body, which contain gastric glands, and the antrum and pylorus, which contain pyloric glands.
39
gastric glands
stomach
Gastric glands: respond to signals from the vagus nerve of the parasympathetic system, which is activated by the brain in response to sight, taste, and smell of food. Have 3 different cell types:
• Mucous cells: produce the bicarbonate-rich mucous that protects the muscular wall from the harshly acidic (pH=2) and proteolytic environment of the stomach.
• Chief cells: secrete pepsinogen which is the inactive, zymogen form of pepsin, a proteolytic enzyme. Hydrogen ions do the cleavage.
o Pepsin: cleaves peptide bonds near aromatic amino acid, resulting in shorter peptide fragments. Operate best at low pH
• Parietal cells: releases hydrochloric acid, produces hydrogen ions
o Secrete intrinsic factor, a glycoprotein involved in proper absorption of vitamin B12.
• Gastric juice: a combination of secretions from chief cells and parietal cells.
• The stomach kills most harmful bacteria and the acidic environment helps to denature proteins.
40
pyloric glands
stomach
contain G-cells that secrete gastrin, a peptide hormone.
• Gastrin: induces parietal cells to secrete more HCl and causes the stomach to contract which mixes the contents.
• Chyme: semifluid mixture in the stomach as a result of digesting solid foods.
41
gastric glands are activated by the ____
vagus nerve of the parasympathetic system, which is activated by the brain in response to sight, taste, and smell of food. Have 3 different cell types:
42
mucous cells
stomach
gastric glands
: produce the bicarbonate-rich mucous that protects the muscular wall from the harshly acidic (pH=2) and proteolytic environment of the stomach.
43
chief cells
stomach
secrete pepsinogen which is the inactive, zymogen form of pepsin, a proteolytic enzyme. Hydrogen ions do the cleavage.
o Pepsin: cleaves peptide bonds near aromatic amino acid, resulting in shorter peptide fragments. Operate best at low pH
44
parietal cells
stomach
releases hydrochloric acid, produces hydrogen ions
o Secrete intrinsic factor, a glycoprotein involved in proper absorption of vitamin B12.
45
gastric juice
stomach
| a combination of secretions from chief cells and parietal cells.
46
what does the acidic environment of the stomach do?
• The stomach kills most harmful bacteria and the acidic environment helps to denature proteins.
47
gastrin
stomach
| induces parietal cells to secrete more HCl and causes the stomach to contract which mixes the contents.
48
chyme
semifluid mixture in the stomach as a result of digesting solid foods.
49
discuss the shape of the stomach
o Lesser curvature: inner curvature
o Greater curvature: outer curvature.
o Rugae: the folds in the lining of the stomach.
50
duodenum
part of the small intestine (can be up to 7 meters long) and is involved in digestion
51
pyloric sphincter
food goes from stomach to small intestine (duodenum)
52
brush-border enzymes
disaccharidases and dipeptidases: present on the luminal surface of cells lining the duodenum and break down dimers and trimers of biomolecules into absorbable monomers.
53
brush-border enzymes are released by presence of what
chyme
54
disaccharidases
duodenum
brush-border enzyme
digest disaccharides
55
maltase
duodenum
brush-border enzyme
digest maltose
56
isomaltose
duodenum
brush-border enzyme
digest isomaltose
57
lactase
duodenum
brush-border enzyme
digests lactose
58
sucrase
duodenum
brush-border enzyme
digests sucrose
59
peptidases
duodenum
brush-border enzyme
break down proteins or peptides
60
aminopeptidase
duodenum
brush-border enzyme
peptidase
peptidase secreted by glands in the duodenum that removes the N-terminal amino acid from a peptide.
61
dipeptidase
duodenum
brush-border enzyme
peptidase
cleave the peptide bonds of dipeptides to release free amino acids.
62
enteropeptidase (enterokinase)
duodenum
brush-border enzyme
peptidase
enzyme critical for the activation of trypsinogen, a pancreatic protease, to trypsin. Can also activate procarboxypeptidases A and B to their active forms.
63
secretin
duodenum
peptide hormone
peptide hormone that causes pancreatic enzymes to be released into the duodenum.
Regulates pH of digestive tract.
It is an enterogastrone: a hormone that slows motility through the digestive tract.
64
Cholecystokinin (CCK)
secreted in response to the entry of chyme (specifically amino acids and fat in chyme) into the duodenum.
Stimulates the release of bile and pancreatic juices and also acts in the brain where it promotes satiety.
65
bile
complex fluid composed of bile salts, pigments, and cholesterols.
66
bile salts
derived from cholesterol.
o Have both hydrophilic and hydrophobic parts
o Serve an important role in the mechanical digestion of fats and ultimately facilitate the chemical digestion of lipids.
o In the small intestine they emulsify fats and cholesterol into micelles.
Make them available to pancreatic lipase.
67
do bile salts do chemical or mechanical digestion?
they do mechanical digestion that allows further chemical digestion to occur via lipases
68
pancreatic juice
complex mixture of several enzymes in a bicarbonate-rich alkaline solution.
o Bicarbonate neutralizes acidic chyme and provides an ideal working environment for most enzymes.
o Contain enzymes that can digest all three types of nutrients: carbs, fats, and proteins.
69
go from ____ environment in the stomach to ____ environment in the duodenum
acidic
| basic
70
go from ____ environment in the stomach to ____ environment in the duodenum
acidic
| basic
71
pancreas 4 functions
1. release bicarbonate to neutralize the acidic chyme from the stomach
2. pancreatic amylase: break down starch into smaller sugars
3. pancreatic lipase: triglyceride breakdown to free fatty acids
4. proteolytic enzymes (trypsinogen and chymotrypsinogen)
72
gallbladder
stores bile until it needs to be released: hormone that causes it to leave is CCK
o Located just beneath the liver and both stores and concentrates bile.
o Release of CCK, contracts and pushes bile out into the biliary tree.
The bile duct system merges with the pancreatic duct before emptying into the duodenum.
o Pancreatitis is the result of stone formation that causes a blockage of the biliary tree and pancreatic duct.
73
biliary tree
route that bile travels
liver ==> common hepatic duct ==> cystic duct ==> gallbladder ==> cystic duct ==> common bile duct ==>
duodenum ==> digested
74
bile vs. bile salts
bile contains bile salts, pigments, and cholesterol
bile salts are responsible for emulsifying fats in the duodenum
75
cells in pancreas that releases endocrine vs. exocrine
endocrine: islets of langerhans cells
exocrine: acinar cells
76
pancreas endocrine function
release of insulin, glucagon, and somatostatin from cells residing in islets of Langerhans scattered throughout the organ.
77
what are the exocrine cells called in the pancreas
acinar cells that produce pancreatic juices.
78
pancreatic juices
Bicarbonate-rich alkaline secretions containing many digestive enzymes for all three classes of biomolecules.
Pancreatic amylase: breaks down large polysaccharides into small disaccharides (carbohydrate digestion)
The pancreatic peptidases trypsinogen, chymotrypsinogen, and carboxypeptidases A and B are released in their zymogen form and once activated assist with protein degradation.
• Enteropeptidase is the main switch that turns all of them on.
Pancreatic lipase: capable of breaking down fats into free fatty acids and glycerol.
79
how do pancreatic juices get to the duodenum?
via a duct system that runs along the middle of the pancreas.
80
what are the two systems the liver uses to communicate with the digestive system?
bile duct and hepatic portal vein
81
peptidases trypsinogen, chymotrypsinogen, and carboxypeptidases A and B are _____
peptidases
82
bile ducts
connect the liver with both the gallbladder and the small intestine.
83
hepatic portal vein
The liver receives blood draining from the abdominal portion of the digestive tract through the hepatic portal vein.
• This nutrient rich blood is processed by the liver before passing into the inferior vena cava.
84
roles of the liver in metabolism
The liver takes up excess sugar to create glycogen and stores fats as triacylglycerols. Can also produce glucose through glycogenolysis and gluconeogenesis and mobilize fats in lipoproteins.
85
bilirubin
major pigment in bile, which is a byproduct of the breakdown of hemoglobin.
• Travels to the liver where it is conjugated (attached to a protein) and secreted into the bile for excretion.
• Jaundice occurs when the liver is unable to process or excrete bilirubin.
86
albumin and the liver
These proteins include albumin, a protein that maintains plasma oncotic pressure and also serves as a carrier for many drugs and hormones, and clotting factors used during blood coagulation.
87
where does absorption occur?
• Absorption occurs in the jejunum and ileum of the small intestine and water is absorbed at the large intestine
88
villi
line the small intestine, small, fingerlike projections from the epithelial lining
Each one has microvilli, which drastically increase the surface area available for absorption.
In the middle of each villus there is a capillary bed for the absorption of water-soluble nutrients and a lacteal, a lymphatic channel that takes up fats for transport into the lymphatic system.
89
absorption of simple sugars such as glucose, fructose, and galactose and amino acids are absorbed by what processes
secondary active transport and facilitated diffusion
90
where do absorbed molecules in the small intestine go?
to the liver via the hepatic portal circulation
91
how do short chain fatty acids get into the intestinal capillaries?
o Short chain fatty acids will also diffuse directly into the intestinal capillaries.
Nonpolar, can traverse the membrane.
92
how do long chain fatty acids get into the intestinal capillaries?
Larger fats, glycerol, and cholesterol move separately into the intestinal cells but then reform triacyglycerides.
• Triacyglycerides and esterified cholesterol molecules are packaged into chylomicrons.
o These enter the lymphatic circulation via lacteals.
The lacteals converge and enter the venous circulation at the thoracic duct in the base of the neck.
93
what are the vitamins absorbed in the small intestine?
Fat soluble : A, D, E, K: dissolve directly into chylomicrons to enter lymphatic circulation
Water soluble: all other vitamins: taken up, along with water, amino acids, and carbohydrates, across the endothelial cells of the small intestine passing directly into the plasma.
94
what are the fat soluble vitamins?
A, D, E, K
95
what do the fat soluble vitamins have to do to get into the bloodstream?
dissolve directly into chylomicrons to enter lymphatic circulation
96
what do the water soluble vitamins have to do to get into the bloodstream?
all other vitamins: taken up, along with water, amino acids, and carbohydrates, across the endothelial cells of the small intestine passing directly into the plasma.
97
what are the 3 parts of the large intestine?
cecum, colon, rectum
98
cecum
large intestine
outpocketing that accepts fluid exiting the small intestine through the ileocecal valve and is site of attachment of the appendix.
• Appendix may be responsible for replenishing the flora of the large intestine after diarrhea.
99
colon
large intestine
divided into the ascending, transverse, descending, and sigmoid colons.
• main function is to absorb water and salts from undigested material left over by the small intestine.
• Concentrates the remaining material to form feces.
100
rectum
large intestine
storage site for feces, which consists of indigestible material, water, bacteria, and certain digestive secretions that are not reabsorbed (enzymes and some bile)
• Anus: opening through which wastes are eliminated
o 1. Internal anal sphincter: autonomic control
o 2. External anal sphincter: somatic control
101
valve that separates small intestine from large intestine?
ileocecal valve
102
o The presence of bacteria in the colon represents a _____ relationship
symbiotic
103
what hormones trigger thirst?
ADH and aldosterone
104
what hormone trigger hunger?
ghrelin (stomach) and glucagon (pancreas)
105
what hormones trigger satiety?
leptin and insulin
106
compare amylase in the mouth vs. small intestine
salivary amylase breaks down more readily soluble starches while pancreatic amylase is active in the small intestine and breaks down less soluble carbohydrates.
107
what are the 3 parts of the pharynx?
Nasopharynx: behind the nasal cavity
Oropharynx: at the back of the mouth
Laryngopharynx: above the vocal cords
108
what is a common reason for heartburn?
weakness in the lower esophageal sphincter
109
what is mucus in the stomach produced by mucosal cells of the gastric glands high in that allows it to protect the mucous walls from acid?
bicarbonate
110
pepsin
digests proteins by cleaving peptide bonds near aromatic amino acids.
111
what 6 products does the stomach secrete?
1. HCl: kills microbes, denatures proteins, converts pepsinogen to pepsin
2. pepsinogen: cleaved in the stomach to pepsin, an enzyme that partially digests proteins
3. mucus: protects mucosa
4. bicarbonate: protects mucosa
5. water (dissolves and dilutes ingested material)
6. intrinsic factor (required for normal absorption of vitamin B12)
112
what does mucus protein
mucosa
113
what are the 3 segments of the small intestine?
duodenum, jejunum, and ileum
114
discuss bile salts and lipases working together in the duodenum
Bile gets the fats into the solution and increases their surface area by placing them in micelles (mechanical digestion). Then, lipase can come in to hydrolyze the ester bonds holding the lipids together (chemical digestion).
115
the pancreas, liver, and gallbladder are all from which germ layer?
endoderm
116
what are all of the functions of the liver?
processing and synthesis of nutrients (glycogenesis and glycogenolysis, storage and mobilization of fats, gluconeogenesis), production of urea, detoxification of chemicals, production of bile, and synthesis of albumin and clotting factors
117
_____ occurs when the liver is unable to process or excrete bilirubin.
Jaundice
118
carboxypeptidase vs. aminopeptidase
carboxy: hydrolyzes terminal peptide bond at carboxy end (activated by enteropeptidase)
amino: hydrolyzes terminal peptide bond at amino end
119
compare the small intestine and the large intestine with respect to what they absorb
small: nutrients
large: water
120
in the small intestine, at the middle of each villus what is there?
there is a capillary bed for the absorption of water soluble molecules and a lymphatic channel that takes up fats for transport into the lymphatic system
121
what causes carbohydrates and amino acids to diffuse from epithelial cells to capillaries?
concentration gradient because blood is always flowing in the capillaries.
122
how do carbohydrates and amino acids get from the small intestine into epithelial cells?
secondary active transport and facilitated diffusion
123
describe water secretion into gastrointestinal tract and reabsorption
7 L of water secreted into tract so this must be retaken up. Follows absorbed solutes via osmosis in the small intestine and hydrostatic pressure at the capillaries puts it back into circulation through lymphatic system
124
transcellularly vs. paracellularly
trans: across the cell membrane
para: squeezing between cells
125
appendix
may be responsible for replenishing the flora of the large intestine after diarrhea.
attached to the cecum
126
is the internal or external sphincter of the anus under voluntary control?
internal
127
although the large intestine's main role is to absorb water, ____ water is absorbed in the small intestine
more
128
maltase breaks down maltose but it does not break down ____
starch
| maltase is brush border enzyme
129
once activated, trypsin can active ______
chymotrypsinogen
130
in an individual with a damaged parasympathetic nervous system, would we expect diarrhea or constipation?
constipation
131
can brush border enzymes breakdown starch?
no, just disaccharides. Starch must be broken down by salivary or pancreatic amylase
