Learning Outcome 6 Digestive System Flashcards
(156 cards)
1
Q
What is the difference between the organs of the alimentary canal and the accessory digestive organs?
A
Alimentary Canal - Nourish the body: pharynx, esophagus, stomach, and small and large intestines
Accessory Digestive Organs - aids in the breakdown of food: mouth, teeth and tongue, salivary glands, gallbladder, liver, and pancreas, bile and enzyme
2
Q
Where does the alimentary canal begin and end?
A
Mouth and anus
3
Q
What are the layers of the alimentary canal from deep to superficial?
A
- Mucosa (Inner)
- Submucosa
- Muscularis
- Serosa
4
Q
What is the purpose of the smooth muscle found in the muscularis mucosa?
A
This thin layer of smooth muscle is in a constant state of tension, pulling the mucosa of the stomach and small intestine into undulating folds. These folds dramatically increase the surface area available for digestion and absorption.
5
Q
What types of tissue are found in the submucosa and the mucosa?`
A
Mucosa - Smooth muscle
Submucosa - Dense CT
6
Q
Where is the serosa found? Where is it not located? What is the function?
A
superficial to the muscularis. Present only in the region of the alimentary canal within the abdominal cavity,
Instead of serosa, the mouth, pharynx, and esophagus have a dense sheath of collagen fibers called the adventitia.
These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column.
7
Q
What effect does sympathetic and parasympathetic activation have on digestion?
A
sympathetic activation (the fight-or-flight response) restricts the activity of enteric neurons, thereby decreasing GI secretion and motility.
parasympathetic activation (the rest-and-digest response) increases GI secretion and motility by stimulating neurons of the enteric nervous system.
8
Q
What are the two functions of blood vessels serving the digestive system?
A
They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. Lipids are absorbed via lacteals, tiny structures of the lymphatic system.
Second function is to supply the organs of the alimentary canal with the nutrients and oxygen needed to drive their cellular processes.
9
Q
What purpose does the hepatic portal system, and the liver serve in blood supply to the digestive system?
A
The veins that collect nutrient-rich blood from the small intestine (where most absorption occurs) empty into the hepatic portal system. This venous network takes the blood into the liver where the nutrients are either processed or stored for later use.
10
Q
What does retroperitoneal mean?
A
the pancreas, and portions of the large intestine (the ascending and descending colon, and the rectum) remain completely or partially posterior to the peritoneum. Thus, the location of these organs is described as retroperitoneal.
11
Q
What are the five major peritoneal folds?
A
Fold Description
Greater omentum - Apron-like structure that lies superficial to the small intestine and transverse colon; a site of fat deposition in people who are overweight
Falciform ligament - Anchors the liver to the anterior abdominal wall and inferior border of the diaphragm
Lesser omentum - Suspends the stomach from the inferior border of the liver; provides a pathway for structures connecting to the liver
Mesentery - Vertical band of tissue anterior to the lumbar vertebrae and anchoring all of the small intestine except the initial portion (the duodenum)
Mesocolon - Attaches two portions of the large intestine (the transverse and sigmoid colon) to the posterior abdominal wall
12
Q
What is the difference between mechanical and chemical digestion? Give an example of a location that does each of these types of digestion
A
Mechanical Digestion – The physical breakdown of food into smaller pieces without altering its chemical structure.
Example Location: Mouth (chewing by teeth) and stomach (churning by muscular contractions).
Chemical Digestion – The breakdown of food into its chemical components by enzymes and digestive secretions.
Example Location: Stomach (pepsin breaking down proteins) and small intestine (pancreatic enzymes digesting carbohydrates, proteins, and fats).
13
Q
What are the six processes of digestion?
A
ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
14
Q
Where does ingestion occur?
A
Oral cavity
15
Q
How does peristalsis move food through the digestive tract?
A
Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along.
These waves also play a role in mixing food with digestive juices.
16
Q
Mastication and segmentation are examples of ________ digestion
A
Mechanical
17
Q
Enzymes assist with ________ digestion
A
Chemical
18
Q
Where does most of the absorption in the digestive tract occur?
A
Small intestine
19
Q
The digestive system is controlled both by ________ and ________ regulatory
mechanisms
A
Neural and Hormonal
20
Q
What do mechanoreceptors, chemoreceptors and osmoreceptors detect?
A
Mechanoreceptors detect stretch and pressure within the digestive tract, helping regulate motility and reflex responses.
Chemoreceptors detect changes in pH, nutrient composition, and chemical stimuli (e.g., the presence of fats, proteins, or acids) to regulate digestive secretions.
Osmoreceptors detect changes in osmolarity (solute concentration) in the digestive contents, helping to regulate water balance and secretion of digestive fluids.
21
Q
Extrinsic nerve plexuses stimulate ________ reflexes, and intrinsic nerve
plexuses stimulate ________ reflexes
A
Extrinsic nerve plexuses stimulate long reflexes, and intrinsic nerve
plexuses stimulate short reflexes
22
Q
What type of reflex is initiated when the sight or smell of food increases the
section of digestive juices?
A
Cephalic Relfex
23
Q
What is the main digestive hormone of the stomach?
A
Gastrin
24
Q
What organ secretes cholecystokinin (CCK) and secretin?
A
Small Intestine
25
The cheeks, tongue, and palate make up the ____________.
Oral Cavity (Mouth)
26
What attaches the inner surface of the lip to the gum?
labial frenulum
27
The maxillary and palatine bones make up the ________ palate, and skeletal muscles primarily make up the ________ palate.
The maxillary and palatine bones make up the hard palate, and skeletal muscles primarily make up the soft palate.
28
Identify at least three things the tongue does to help in digestion.
facilitating ingestion, mechanical digestion, chemical digestion (lingual lipase), sensation (of taste, texture, and temperature of food), swallowing, and vocalization.
29
How does the tongue aid in the swallowing of a bolus of food?
23.3 Textbook Reading
30
Lingual lipase helps to break down __________ in the stomach
triglycerides
31
The _____________ _______________ attaches the tongue to the floor of the mouth
Lingual Frenulum
32
What two cranial nerves are involved with detecting taste on the tongue?
Facial nerve (Cranial Nerve VII) – It carries taste sensations from the anterior two-thirds of the tongue.
Glossopharyngeal nerve (Cranial Nerve IX) – It carries taste sensations from the posterior one-third of the tongue.
33
Does saliva secretion increase or decrease when eating?
Increase
34
What are the three pairs of salivary glands? Which cranial nerves are involved for each
Submandibular glands, which are in the floor of the mouth, secrete saliva into the mouth through the submandibular ducts.
Sublingual glands, which lie below the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity.
Parotid glands lie between the skin and the masseter muscle, near the ears. They secrete saliva into the mouth through the parotid duct, which is located near the second upper molar tooth (and where are the different salivary glands located?
35
What is the major component of saliva?
Saliva is essentially (99.4 percent) water. The remaining 0.6 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products.
Salivary amylase (Digestive enzyme)
36
What is the role of immunoglobulin A and lysozyme in saliva?
Saliva contains immunoglobulin A, which prevents microbes from penetrating the epithelium, and lysozyme, which makes saliva antimicrobial.
37
What are the different types of teeth? What is the purpose of teeth?
- 8 Incisors
- 4 Cuspids (Canines)
- 8 Premolars (Bicuspids)
- 12 Molars
38
Which type of teeth are best suited for piercing tough food?
molars, which have several pointed cusps used to crush food
39
What surrounds the neck of a tooth?
Gingivae (commonly called the gums)
40
What is the top portion of a tooth above the gum line?
crown, which is the portion projecting above the gum line,
41
What type of tissue surrounds the pulp cavity?
dentin, a bone-like tissue.
42
What is cementum, and where is it located in relationship to enamel?
In the root of each tooth, the dentin is covered by a layer of modified bone called cementum.
In the crown of each tooth, the dentin is covered by an outer layer of enamel, the hardest substance in the body
43
The ________ receives food from the mouth? What are the three segments of the pharynx?
Pharynx
The most superior, the nasopharynx, is involved only in breathing and speech. The other two subdivisions, the oropharynx and the laryngopharynx, are used for both breathing and digestion.
44
What two structures does the esophagus connect?
The inferior border of the laryngopharynx connects to the esophagus, whereas
45
What happens when the upper esophageal sphincter relaxes?
Open
46
What is the purpose of the lower esophageal sphincter?
The lower esophageal sphincter relaxes to let food pass into the stomach, and then contracts to prevent stomach acids from backing up into the esophagus.
47
What are the three stages of deglutition?
voluntary phase - also known as the oral or buccal phase) is so called because you can control when you swallow food.
pharyngeal phase - stimulation of receptors in the oropharynx sends impulses to the deglutition center (a collection of neurons that controls swallowing) in the medulla oblongata. The laryngeal muscles also constrict to prevent aspiration of food into the trachea. Apnea phase
Esophageal Phase - The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis.
48
What does the tongue do in the voluntary phase?
The tongue moves upward and backward against the palate, pushing the bolus to the back of the oral cavity and into the oropharynx.
49
What is the role of peristalsis in the esophageal phase?
Peristalsis propels the bolus through the esophagus and toward the stomach.
50
What is the purpose of the mucous lining the esophagus?
During the esophageal phase, esophageal glands secrete mucus that lubricates the bolus and minimizes friction.
51
52
The stomach leads to the first part of the small intestine, the _____________
duodenum
53
What is absorbed in the stomach?
Little if any nutrient absorption occurs in the stomach, with the exception of the negligible amount of nutrients in alcohol.
54
What are the four main regions of the stomach? How many curvatures are there in the stomach?
The cardia, fundus, body, and pylorus. See 23.4
Two curvatures:
Greater curvature – The longer, convex lateral border of the stomach.
Lesser curvature – The shorter, concave medial border of the stomach.
55
What does the pyloric sphincter control?
pyloric sphincter is located at this latter point of connection and controls stomach emptying.
56
What are rugae and what purpose do they serve?
In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a ruga.
57
Why does the stomach have an additional layer of the muscularis?
In addition to the typical circular and longitudinal smooth muscle layers, the muscularis has an inner oblique smooth muscle layer. In addition to moving food through the canal, the stomach can vigorously churn food, mechanically breaking it down into smaller particles.
58
What are gastric pits and gastric glands?
The stomach mucosa’s epithelial lining consists only of surface mucus cells, which secrete a protective coat of alkaline mucus. A vast number of gastric pits dot the surface of the epithelium, giving it the appearance of a well-used pincushion, and mark the entry to each gastric gland, which secretes a complex digestive fluid referred to as gastric juice.
59
What hormone is secreted by the gastric glands?
gastrin
60
________ cells secrete hydrochloric acid (HCl) and intrinsic factor
Parietal Cells
61
Chief cells secrete ________, the inactive form of ________
pepsinogen, the inactive proenzyme form of pepsin.
62
Mucous neck cells secrete ______
secrete thin, acidic mucus
63
Enteroendocrine cells (G cells), secrete the hormone ________________
secrete various hormones into the interstitial fluid of the lamina propria. These include gastrin, which is released mainly by enteroendocrine G cells.
64
What phase occurs before food enters the stomach?
cephalic phase (reflex phase) of gastric secretion, which is relatively brief, takes place before food enters the stomach. The smell, taste, sight, or thought of food triggers this phase.
65
What are the three phases of gastric secretion? What occurs in each phase and how is the phase controlled?
cephalic phase (reflex phase) of gastric secretion, which is relatively brief, takes place before food enters the stomach. The smell, taste, sight, or thought of food triggers this phase.
The gastric phase of secretion lasts 3 to 4 hours, and is set in motion by local neural and hormonal mechanisms triggered by the entry of food into the stomach.
The intestinal phase of gastric secretion has both excitatory and inhibitory elements.
66
The gastric phase is initiated by the entry of _______ in the stomach
food
67
The _____________ phase initially stimulates stomach secretory activity, but
later inhibits it after chyme distends the _____________
Intestinal Phase
duodenum
68
Why does the stomach need a mucosal barrier?
The mucosa of the stomach is exposed to the highly corrosive acidity of gastric juice. Gastric enzymes that can digest protein can also digest the stomach itself.
69
How does bicarbonate help to prevent damage to the stomach?
This mucus forms a physical barrier, and its bicarbonate ions neutralize acid.
70
How does gastric emptying occur?
rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum.
71
What role does the fundus play in digestion?
it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme.
72
What is the difference between mechanical and chemical digestion in the stomach?
Mechanical digestion = Physical mixing and breakdown of food.
Chemical digestion = Breakdown of food molecules by acids and enzymes.
73
When is salivary amylase active and lingula lipase active?
the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme.
Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides.
74
What is the purpose of intrinsic factor?
Intrinsic factor is a glycoprotein secreted by parietal cells of the stomach. Its primary function is to bind to vitamin B12 in the small intestine (mainly the ileum) to facilitate its absorption.
75
Why is the small intestine the primary digestive organ?
Pimary organ for digestion and absorption
76
What is the sequence that chyme passes through the small intestine?
Duodenum – The first and shortest section; receives chyme from the stomach along with digestive enzymes from the pancreas and bile from the liver and gallbladder.
Jejunum – The middle section; primarily responsible for nutrient absorption.
Ileum – The final section; absorbs vitamin B12, bile salts, and any remaining nutrients before passing the chyme into the large intestine through the ileocecal valve.
77
The ________ duct and main pancreatic duct pass their contents into the duodenum and the _____________ _____________
The bile duct and main pancreatic duct pass their contents into the duodenum and the hepatopancreatic ampulla.
78
What sphincter regulates the flow of bile and pancreatic juice into the duodenum?
hepatopancreatic sphincter
79
The ileocecal sphincter is the junction between what two parts of the digestive tract.
junction between the ileum (the final part of the small intestine) and the cecum (the beginning of the large intestine).
This sphincter controls the flow of chyme from the ileum into the cecum and prevents backflow from the large intestine into the small intestine.
80
What artery supplies blood to the small intestines?
superior mesenteric artery
81
What are some ways the mucosa and submucosa are modified to increase the absorptive surface area?
Circular Folds (Plicae Circulares) – These deep, permanent folds in the mucosa and submucosa slow the movement of chyme, allowing more time for absorption.
Villi – Finger-like projections of the mucosa that contain capillaries and lacteals, increasing surface area and facilitating nutrient absorption.
Microvilli (Brush Border) – Tiny, hair-like extensions on the surface of epithelial cells that further increase surface area and contain enzymes for final digestion.
82
What is found within villi? What purpose do lacteals serve?
each villus contains a capillary bed composed of one arteriole and one venule, as well as a lymphatic capillary called a lacteal
83
Where is intestinal juice produced?
the mucosa between the villi is dotted with deep crevices that each lead into a tubular intestinal gland (small intestine)
84
What types of intestinal glands are there and what do each of them produce?
85
What layer of the intestines is MALT found?
The lamina propria of the small intestine mucosa is studded with quite a bit of MALT.
86
What is the purpose of segmentation in the small intestines?
combines the chyme with digestive juices and pushes food particles against the mucosa to be absorbed.
87
What is the gastroileal reflex?
First, digestive activity in the stomach provokes the gastroileal reflex, which increases the force of ileal segmentation.
88
Do lipids undergo any substantial digestion before entering the small intestines?
Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancreatic lipase.
89
Why is chyme delivered to the intestines in small amounts?
For optimal chemical digestion, chyme must be delivered from the stomach slowly and in small amounts. This is because chyme from the stomach is typically hypertonic, and if large quantities were forced all at once into the small intestine, the resulting osmotic water loss from the blood into the intestinal lumen would result in potentially life-threatening low blood volume. In addition, continued digestion requires an upward adjustment of the low pH of stomach chyme, along with rigorous mixing of the chyme with bile and pancreatic juices. Both processes take time, so the pumping action of the pylorus must be carefully controlled to prevent the duodenum from being overwhelmed with chyme.
90
What are the functions of the large intestine?
The primary function of this organ is to finish absorption of nutrients and water, synthesize certain vitamins, form feces, and eliminate feces from the body.
91
What is the appendix thought to do?
-a winding tube that attaches to the cecum.
-long appendix contains lymphoid tissue, suggesting an immunologic function, this organ is generally considered vestigial.
-In diarrheal illness, the appendix may serve as a bacterial reservoir to repopulate the enteric bacteria for those surviving the initial phases of the illness.
92
What is the pathway of food through the segments of the colon?
93
Large Intestine 4 Subdivisons
Cecum, the colon, the rectum, and the anus.
The ileocecal valve, located at the opening between the ileum and the large intestine, controls the flow of chyme from the small intestine to the large intestine.
94
What are the two sphincters of the anal canal? Which one is voluntary?
Internal anal sphincter is made of smooth muscle, and its contractions are involuntary.
External anal sphincter is made of skeletal muscle, which is under voluntary control. Except when defecating, both usually remain closed.
95
Order of the colon (Large Intestine)
Cecum – The first part of the large intestine, where the ileocecal valve connects the small intestine to the colon.
Ascending Colon – Travels upward on the right side of the abdomen.
Transverse Colon – Runs horizontally across the abdomen, from right to left.
Descending Colon – Travels downward on the left side of the abdomen.
Sigmoid Colon – An S-shaped section that connects to the rectum.
From the sigmoid colon, waste moves into the rectum and then exits through the anus.
96
Compared to the small intestines, what do the large intestines not have?
no circular folds or villi (Enzyme secreting cells)
97
What is absorbed by the enterocytes of the large intestine?
The enterocytes absorb water and salts as well as vitamins produced by your intestinal bacteria.
98
What is the difference between teniae coli and haustra?
teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Tonic contractions of the teniae coli bunch up the colon into a succession of pouches called haustra (singular = haustrum), which are responsible for the wrinkled appearance of the colon. Attached
99
What do the normal bacterial flora provide that is beneficial?
many facilitate chemical digestion and absorption, and some synthesize certain vitamins, mainly biotin, pantothenic acid, and vitamin K. Some are linked to increased immune response.
100
What is the difference between haustral contractions and mass movement?
The presence of food residues in the colon stimulates a slow-moving haustral contraction. This type of movement involves sluggish segmentation, primarily in the transverse and descending colons. When a haustrum is distended with chyme, its muscle contracts, pushing the residue into the next haustrum. These contractions occur about every 30 minutes, and each last about 1 minute. These movements also mix the food residue, which helps the large intestine absorb water.
The third type is a mass movement. These strong waves start midway through the transverse colon and quickly force the contents toward the rectum. Mass movements usually occur three or four times per day, either while you eat or immediately afterward.
101
What do the large intestines remove to convert liquid chyme into feces?
Remaining water that the small intestine hasnt absorbed
102
Why does the Valsalva maneuver aid in defecation? What part of the nervous system is involved with defecation?
Valsalva’s maneuver, in which you increase intra-abdominal pressure by contracting your diaphragm and abdominal wall muscles, and closing your glottis.
parasympathetic
103
Where is the liver located? What are the functional units of the liver?
upper right quadrant of the abdominal cavity, just below the diaphragm.
The functional units of the liver are called hepatic lobules
104
Chemical digestion in the small intestine relies on the activities of three accessory digestive organs
liver, pancreas, and gallbladder
105
Where do the hepatic artery and hepatic portal vein enter the liver?
The porta hepatis (“gate to the liver”)
106
What does the hepatic portal vein deliver to the liver?
delivers partially deoxygenated blood containing nutrients absorbed from the small intestine and actually supplies more oxygen to the liver
107
Plates of hepatocytes are found in each ______________ ________________.
Hepatic Lobule
108
Where does bile created by hepatocytes accumulate in?
bile canaliculus
109
What vessel is created by the joining of the common hepatic duct and the cystic duct?
common bile duct
110
What is a hepatic sinusoid? Hepatic sinusoids combine and send blood to a
central vein which then flows through the ______________ ______________ to
get to the inferior vena cava. Bile flows the opposite way towards the ducts.
A hepatic sinusoid is an open, porous blood space formed by fenestrated capillaries from nutrient-rich hepatic portal veins and oxygen-rich hepatic arteries.
Hepatic Veins
111
What is the role of reticuloendothelial cells in the liver?
The hepatic sinusoids also contain star-shaped reticuloendothelial cells (Kupffer cells), phagocytes that remove dead red and white blood cells, bacteria, and other foreign material that enter the sinusoids.
112
What are the three components of a portal triad?
a bile duct, a hepatic artery branch, and a hepatic portal vein branch.
113
Identify three metabolic functions of the liver.
Glycogen Storage and Gluconeogenesis
Detoxification
Lipid Metabolism
114
Identify four methods the liver regulates hematological functions.
23.6 Textbook
115
Bile emulsifies lipids. What is emulsification?
Bile is a mixture secreted by the liver to accomplish the emulsification of lipids in the small intestine.
large lipid globules must be broken down into smaller lipid globules, a process called emulsification.
116
Bile salts and phospholipids in bile increase the surface area available
for what to interact with the separated lipids?
Bile salts and phospholipids in bile increase the surface area available for lipase enzymes to interact with the separated lipids. This process, known as emulsification, helps break down large fat droplets into smaller micelles, making lipid digestion and absorption more efficient in the small intestine.
117
How is bilirubin produced in the body? How is it excreted from the body?
Bilirubin, the main bile pigment, is a waste product produced when the spleen removes old or damaged red blood cells from the circulation.
In the liver, proteins and iron are recycled, whereas bilirubin is excreted in the bile. It accounts for the green color of bile.
118
What are the exocrine and endocrine functions of the pancreas?
exocrine (secreting digestive enzymes)
endocrine (releasing hormones into the blood) functions
119
What do the acini produce?
The exocrine part of the pancreas arises as little grape-like cell clusters, each called an acinus, located at the terminal ends of pancreatic ducts.
These acinar cells secrete enzyme-rich pancreatic juice into tiny merging ducts that form two dominant ducts.
120
What do the enzymes in pancreatic juice help the body to digest?
carbohydrates, proteins, fats, and nucleic acids
121
What regulates pancreatic secretion?
Regulation of pancreatic secretion is the job of hormones and the parasympathetic nervous system.
122
What does the pancreas release to neutralize acidic chyme?
bicarbonate
123
What is the purpose of the gallbladder?
This muscular sac stores, concentrates, and, when stimulated, propels the bile into the duodenum via the common bile duct. (Which is produced by the liver)
124
Bile from the gallbladder leaves via the ____________ duct
Bile from the gallbladder leaves via the cystic duct.
The cystic duct joins the common hepatic duct from the liver to form the common bile duct, which then empties bile into the duodenum (first part of the small intestine) through the hepatopancreatic ampulla (Ampulla of Vater).
125
What are the functions of the gallbladder?
Storage of Bile – The gallbladder stores bile, which is produced by the liver. This allows bile to be released in larger amounts when needed for digestion.
Concentration of Bile – The gallbladder absorbs water and electrolytes from bile, making it more concentrated and effective in digesting fats.
Release of Bile – When fatty foods enter the small intestine, the hormone cholecystokinin (CCK) signals the gallbladder to contract and release bile into the duodenum through the common bile duct, aiding in fat digestion and absorption.
126
What three hormones regulate the activity of the accessory organs? What does each hormone do specifically?
Accessory Organs (liver, pancreas, and gallbladder)
1) Cholecystokinin (CCK)
- Stimulates the gallbladder to contract and release bile into the duodenum.
- Stimulates the pancreas to release digestive enzymes.
- Slows gastric emptying to allow for proper digestion.
2) Secretin
- Stimulates the pancreas to release bicarbonate-rich fluid to neutralize acidic chyme entering the duodenum.
- Inhibits gastric acid secretion in the stomach.
- Enhances bile production in the liver.
3) Gastrin
- Primarily stimulates the stomach to produce gastric acid.
- Indirectly promotes bile production and pancreatic enzyme secretion by enhancing digestion in the stomach.
127
Where does chemical digestion of CHOs (Carbohydrate) begin?
In the mouth
128
Pancreatic ____________ breaks down CHOs in the small intestines
pancreatic amylase
129
_______________ breaks down one glucose at a time
α-dextrin
130
Sucrose, lactose, and maltose are broken down by what three enzymes?
Sucrase → Breaks down sucrose into glucose and fructose.
Lactase → Breaks down lactose into glucose and galactose.
Maltase → Breaks down maltose into two glucose molecules.
131
What are the fates of glucose in the body?
Immediate Energy Production – Glucose is used in cellular respiration (glycolysis, Krebs cycle, and oxidative phosphorylation) to produce ATP for energy.
Glycogenesis (Storage as Glycogen) – Excess glucose is stored as glycogen in the liver and muscles for later use.
Lipogenesis (Conversion to Fat) – When glycogen stores are full, excess glucose is converted into fat and stored in adipose tissue.
Gluconeogenesis Substrate – In certain conditions, glucose can be used to produce other molecules like amino acids or serve as a precursor for metabolic processes.
Excretion (In Uncontrolled Diabetes) – If blood glucose levels are too high and cannot be stored or used properly, it may be excreted in urine (glucosuria), as seen in diabetes mellitus.
132
Where does protein digestion start in the digestive system?
Stomach
133
What enzymes are secreted by the brush border to help breakdown proteins?
aminopeptidase and dipeptidase
134
What are the end products of protein digestion?
This results in molecules small enough to enter the bloodstream
135
What are the fates of amino acids in the body? (How does the body use or process glucose?)
Immediate Energy Production – Glucose is used in cellular respiration (glycolysis, Krebs cycle, and oxidative phosphorylation) to produce ATP for energy.
Glycogenesis (Storage as Glycogen) – Excess glucose is stored as glycogen in the liver and muscles for later use.
Lipogenesis (Conversion to Fat) – When glycogen stores are full, excess glucose is converted into fat and stored in adipose tissue.
Gluconeogenesis Substrate – In certain conditions, glucose can be used to produce other molecules like amino acids or serve as a precursor for metabolic processes.
Excretion (In Uncontrolled Diabetes) – If blood glucose levels are too high and cannot be stored or used properly, it may be excreted in urine (glucosuria), as seen in diabetes mellitus.
136
Which lipase is the most important to digestion? What organ produces it?
pancreatic lipase.
produced by the pancreas and secreted into the small intestine
137
What are the end products of lipids?
fatty acids and glycerol
138
What are the fates of fatty acids and glycerol in the body?
Energy, Storage, Synthesise,, Ketones, Glugogenesiss
139
What are the two types of pancreatic nucleases? What do they digest?
deoxyribonuclease, which digests DNA
ribonuclease, which digests RNA
140
What are the five mechanisms used for absorption?
(1) active transport, (2) passive diffusion, (3) facilitated diffusion, (4) co-transport (or secondary active transport), and (5) endocytosis.
141
What is different about absorption of water-soluble vs lipid-soluble nutrients?
water-soluble nutrients must use transport molecules embedded in the membrane to enter cells.
nutrients, lipid-soluble nutrients can diffuse through the plasma membrane.
142
CHOs are broken down and absorbed in the form of ___________________
absorbed in the form of monosaccharides.
143
What happens to indigestible (insoluble) fiber?
does not get broken down by digestive enzymes in the stomach or small intestine. Instead, it passes through the digestive system largely intact
144
What is the pathway of monosaccharides into the body until they reach the
liver?
The monosaccharides enter the bloodstream through the intestines, are transported to the liver via the portal vein, and are then processed or stored in the liver for later use by the body.
145
Where are most proteins absorbed in the digestive tract?
Small Intestine
146
How long of amino acid chains are usually absorbed?
2 or 3 chains
147
Where are most lipids absorbed?
Small Intestine
148
What is a micelle?
bile salts and lecithin resolve this issue by enclosing them in a micelle, which is a tiny sphere with polar (hydrophilic) ends facing the watery environment and hydrophobic tails turned to the interior, creating a receptive environment for the long-chain fatty acids.
149
Chylomicrons are ___________-soluble and enter the lacteals after passing out
of the cel
Water soluble
150
_____________ ______________ breaks down the triglycerides of the
chylomicrons
lipoprotein lipase
151
What is the path of fatty acid and glycerol absorption from the intestines to the liver?
152
How are nucleic acids absorbed?
The products of nucleic acid digestion—pentose sugars, nitrogenous bases, and phosphate ions—are transported by carriers across the villus epithelium via active transport. These products then enter the bloodstream.
153
All ions except ________ and ________ are always absorbed in the intestines
even when not needed
Iron and calcium are exceptions
They are absorbed in the duodenum in amounts that meet the body’s current requirements,
154
What effect does parathyroid hormone (PTH) have on calcium absorption of
dietary calcium
When blood levels of ionic calcium drop, parathyroid hormone (PTH) secreted by the parathyroid glands stimulates the release of calcium ions from bone matrices and increases the reabsorption of calcium by the kidneys.
155
Where are fat soluble vitamins (A, D, E, and K) primarily absorbed?
Small Intestine
156
How is absorption of B12 different than other vitamins? Why is intrinsic factor
necessary for absorption?
vitamin B12, which is a very large molecule. Intrinsic factor secreted in the stomach binds to vitamin B12, preventing its digestion and creating a complex that binds to mucosal receptors in the terminal ileum, where it is taken up by endocytosis.
