1 Flashcards
(170 cards)
1
Q
How is calcium absorbed in the small intestine? How does calcium cross the basolateral membrane? And, which hormones regulate the absorption of calcium
A
2
Q
How is iron absorbed in the small intestines? How is iron stored or transported? And what is the plasma protein carrier called that it binds to?
A
- Iron is actively absorbed by the small intestine
- Can be stored in a granular form called ferritin or transported into the blood
- When transported in the blood, where it binds to transferrin (plasma protein carrier)
3
Q
How is the absroption of iron and calcium different from the absorption of vitamins & nutrients in the small intestines?
A
- The absorption of calcium and iron are regulated, unlike the absorption of nutrients and vitamins
4
Q
How is vitamin B12 absorbed?
A
- Absorbed only when bound to an intrinsic factor, which is a protein secreted by the gastric parietal cells.
5
Q
In the small intestine, what do water-soluble vitamins require to be absorbed?
A
- Requiring transport proteins on the apical & basolateral surfaces to be absorbed
6
Q
How are fat-soluble vitamins transported?And,
what mechanism of action do they use to be absorbed?
A
- Transported in micelles
- Absorbed passively by simple diffusion
7
Q
In the small intestines, how are fats absorbed as? What are the steps involved to create chylomicrons? And, how do chylomicrons cross the basolateral membrane and where do they enter after?
A
- Absorbed as monoglycerides and fatty acids
- Intracellularly, monoglycerides and fatty acids enter the SER and reform triglycerides, which are then sent to the Golgi apparatus for packaging into chylomicrons
- Chylomicrons are exocytosed across the basolateral membrane, entering the lympathic system
8
Q
In the small intestines, how are proteins absorbed as? What are the transport processes involved in the apical and basolateral surface in order to facilitate the absorption of carbohydrates?
A
- Are absorbed as either amino acids, dipeptides or tripeptides
- Across the apical surface, by either Na+ dependent secondary active transport proteins or by facilitated diffusion carrier proteins
- Across the basolateral surface, by facilitated diffusion carrier proteins
9
Q
In the small intestines, how are carbs absorbed as? What are the transport processes involved in the apical and basolateral surface in order to facilitate the absorption of carbohydrates?
A
- Carbs are absorbed as monosacchardies
- Across the apical surface, sodium-dependent secondary active transport proteins
- Across the basolateral surface, diffusion carrier proteins
10
Q
What has transport proteins that are specific for the absorption of key nutrients & minerals in the small intestines?
A
- the epithelial cells of the small intestines
11
Q
Which strucutres allow for the large surface areas of the small intestines, to promote maximal absorption capabilities?
A
- The presence of circular folds, villi, and microvilli
12
Q
Why is absorption in the small intestines not regulated?
A
- For maximal absorption allowance
13
Q
Where does most of the absorption of water, nutrients, and electrolytes in the small intestines occur? And what are the exceptions to that statement?
A
- In the duodenum & ileum
- Expect calcium and iron
14
Q
What is a brush-border enzymes called that is involved in the digestion of peptides?
A
- Aminopeptidases
15
Q
What is a brush-border enzymes called that is involved in the digestion of disaccharides?
A
- Disaccharidases
16
Q
What is the brush-border enzyme called that activates the pancreatic trypsinogen?
A
- Enterokinase
17
Q
What is the function of brush-border enzymes?
A
- Function in digestion in the small intestines, along side pancreatic and hepatic enzymes
18
Q
What are the plasma membrane enzymes called that are found on the apical surface of small-intestine epithelial cells?
A
- Brush-border enzymes
19
Q
In the small intestine, what is the aqueous salt & mucous secretion called? What is the function of said secretion? And, where is this solution secreted & absorbed?
A
- Succus entericus
- To lubricate and protect the small intestines
- It is secreted proximally in the duodenum and is absorbed distally in the ileum
20
Q
What is the secretion produced by the small intestines called?
A
- Succus entericus
21
Q
How is the relaxation of the ileocecal sphincter regulated?
A
- By gastrin and by the distension of the ileum, which triggers a short reflex pathway
22
Q
What serves to regulate the emptying of the small intestine contents into the large intestine and to prevent bacterial contamination of the small intestine from the large intestine ?
A
- The ileocecal sphincter and valve
23
Q
How is the migrating motility complex process of the small intestines regulated? What is the structure called that secretes said hormone? And, why it is secreted?
A
- By the hormone motilin, which is secreted by the endocrine cells of the small intestine in the absence of chyme.
24
Q
How is the segmentation process of the small intestines regulated?
A
- Regulated by distension of the duodenum, by the hormone gastrin, and by ANS innervation
25
How does the migrating motility complex process occur to provide motility for the small intestines? And, what is its function?
- Is a series of short-distance peristaltic waves that move from the duodenum to the ileum in between meals
- To move any remaining chyme left behind during segmentation toward the large intestine.
26
How does the process of segmentation occur to provide motility in the small intestines? And, what is the frequency of the basic electric rhythm?
- It involves alternating contractions and relaxation of the circular muscle initiated by the pacemaker cells of the small intestine
- Where the frequency of the basic electric rhythm (BER) decreases from the duodenum to the ileum
27
What processes in the small intestines does motility occur through?
- Segmentation & the migrating motility complex
28
Which digestive processes is the small intestines involved in? And, what is the primarily site of nutrient digestions and absorption in the digestive system?
- The small intestine is involved in all 4 digestive system processes
- The small intestines
29
What seals the exit of the small intestines?
- The Ileocecal sphincter and Valve
30
What seals the enterance to the small intestines?
- The pyloric sphincter
31
What are the 3 sections of the small intestines called?
- Duodenum, jejunum, and ileum
32
What are the hormones that regulate bile secretion called? And, how are the hormonal regulations of bile secretion stimulated?
- Secretin, secretion is stimulated by increased acid in the duodenum
- CCK, secretion is stimulated by protein digestion products and fat in the duodenum
33
List the 3 stimulants of bile secretion
- The return of bile salts through enterohepatic circulation stimulates secretion
- The increased activity of the parasympathetic vagus nerve (X) stimulates secretion
- The hormone secretin and cholecystokinin (CCK) stimulate secretion
34
What is the bile salt circulating path way called? And how does it flow/operate?
- Called the enterohepatic circulation
- Bile salts are released in the proximal part of the small intestine (duodenum) and are reabsorbed in the distal part of the small intestine (ileum)
- and are returned to the liver through the hepatic portal vein
- Upon returning to the liver, bile salts will be re-secreted in the bile
35
Why is the formation of micelles (micellar) by bile salts important?
- For the transport of monoglycerides & fatty acids, cholesterol, and fat-soluble vitamins
- Facilitating the process of absorption
36
Why is the emulsification of fat globules by bile salts important?
- To increase the surface area of the fat globule for digestion by lipases
- Also, increases the solubility of the fat globule in an aqueous environment
37
What are bile salts? And why are they important for the digestion & absorption of fats?
- Are amphipathic molecules (possessing hydrophobic & hydrophilic elements)
- Aids the digestion of fats through emulsification
- Aids the absorption of fats through micellar formation (micelles)
38
What is Bile?
- Is an aqueous, alkaline fluid that contains bile salts, cholesterol, lecithin, and bilirubin?
39
What are the organs that form the biliary system?
- The liver, gallbladder, and bile duct
40
Where is bile produced and stored? Where does it drain following its storage organ? And where does it release following the drainage phase?
- Bile is produced by the liver and is stored in the gallbladder
- From the gallbladder, it is drained into the bile duct
- From the bile duct it is released into the small intestines (duodenum)
41
How does the liver digest and absorb fats?
- Through it synthesis of bile
42
What Delivers the nutrients absorbed by the small and large intestine to the liver for processing; and returns blood and nutrients to the general venous circulation?
- the heptaic portal vein
43
What delivers oxygen (O2)-rich blood and metabolites to the liver for processing.
- The hepatic artery
44
What do the hepatic arteries and portal veins form in the liver's hepatocytes?
- Form sinusoids and bile ducts, which form bile canaliculi
45
What are the cells of the liver called, and what is contained inside each lobule?
- Called hepatocytes organized into lobules
| - Each lobule contains hepatic arteries & portal veins
46
List the liver functions
- The secretion of bile
- Nutrient processing & storage
- Detoxification
- Plasma protein synthesis
- Vitamin D activation
- Removal of cells & debris from plasma
- Excretion of cholesterol & bilirubin
47
What is the mechanism of action for pancreatic exocrine secretions, and how they are regulated?
- Acid in the duodenal lumen increases the release of secretin, which regulates the secretion of the aqueous alkaline solution by the pancreatic duct cells
- Fat and protein products in the duodenal lumen increase the release of cholecystokinin (CCK), which regulates the secretion of digestive enzymes by the pancreatic acinar cells
48
How are the pancreatic exocrine secretions regulated?
- Independently by secretin and Cholecystokinin (CCK)
49
How is the pancreatic enzyme proteases activated? What are the steps involved?
- Proteases is secreted in zymogen form, and is activated
- in order for it to be activated, trypsinogen must be converted to its active form by the brush border enzyme enterokinase
- Which converts trypsinogen into its active form trypsin
- Trypsin then converts other zymogens to their active forms, such as proteases
50
What are the pancreatic enzymes, such as amylase, lipase, and proteases important for?
- Amylase, is important for the digestion of carbs
- Lipase, is important for the digestion of fats (lipids)
- Proteases, is important for the digestion of proteins
51
What do the acinar & duct cells of the exocrine cells of the pancreas secrete?
- Acinar cells, secrete the pancreatic enzymes
| - Duct cells, secrete an aqueous alkaline solution into the pancreatic duct
52
How is the pancreas both an endocrine and an exocrine gland?
- Endocrine cells, of the pancreas form the islets of Langerhans, which are important to fuel metabolism, through the secretion of the hormones insulin and glucagon
- Exocrine cells, of the pancreas form acini and ducts (Acinar & duct cells)
53
Where are the secretions produced that chyme is mixed with upon entering the small intestines?
- the pancreas
54
How are the intestinal phase factors of gastric secretion regulated? And, what do they secrete as a result?
- Is An inhibitory mechanism, where increased osmolarity, increased concentrations of fats & acids, and increased distension in the small intestines
- Stimulate short-&-long- reflexes pathways
- That results in the secretion of cholecystokinin (CCK), secretin, and the gastric inhibitory polypeptide (GIP)
55
How is the gastric-phase control of gastric secretion regulated? And, what is its mechanism of action pathway?
- Is stimulated by proteins & protein digestion in the stomach, causing distention of the stomach
- Activating chemo-&-mechano-receptors & initiating short-&-long- reflexes
- Which alert parietal & chief cells to increase gastric acid and pepsinogen secretion
56
How is the cephalic-phase control of gastric secretion regulated?And, what is the pathway they take?
- Through the initial inputs of senses of sight, smell, and taste of food (chewing and swallowing)
- Which increases PNS activity
- Can either go through G cells or parietal & chief cells to increase the secretion of gastric acid and pepsinogen
57
What are gastric secretions reguated by?
- By cephalic, gastric, and intestinal phase factors
58
What is the function of the mucus secreted in the esophagus?
- functions to lubrication for the movement of the bolus through to the stomach
59
List the 5 steps involved in the esophageal stage of the swallowing reflex
1. stretching of the esophagus triggers a primary peristaltic wave
2. Peristalsis moves the bolus through the esophagus
3. The lower esophageal sphincter relaxes as its met by the bolus
4. Bolus moves into the stomach
5. If necessary, a secondary peristaltic wave is initiated, and the events above are repeated
60
What seals the exit of the esophagus?
- The lower esophageal (gastroesophageal) sphincter
61
What seals the enterance of the esophagus?
- The upper esophageal (pharyngoesophageal) sphincter
62
What is the function of the esophagus?
- It is a passagage way for the bolus, and is involved in motility through its participation in the esophageal stage of the swallowing reflex
63
What is function of mucus secretion in the pharynx?
- To provide lubrication for the movement of the bolus through to the esophagus
64
List the 6 steps involved in the swallowing reflex in the pharynx
1. Tongue moves bolus into the pharynx
2. Bolus descends on the epiglottis and covers it
3. Uvula elevates to close the nasal passages
4. Swallowing centre of the medulla inhibits the respiratory centre
5. Upper esophageal (pharyngoesophageal) sphincter relaxes
6. Bolus finally moves into the esophagus
65
What does the pharynx contain? Where does the food lead to next after the pharynx? What is the primarily function of the pharyn?
- Contains tonsils
- Food leads into the esophagus from the pharynx
- Functions in motility, through the oropharyngeal stage of the swallowing reflex
66
Where does the digestion of carbohydrates begin? Which enzyme is responsible for this digestion in this first location?Where is the majority of carbohydrates digested in? And what enzyme used in this circumstance?
- Begins in the mouth, utilizing salivary amalyse in the saliva
- Majority of carbs are digested in the small intestines, by pancreatic amaylse
67
What occurs in an increased innervation to the salivary glands by the SNS?
- They produce mucus-rich viscous saliva
68
What occurs in an increased innervation to the salivary glands by the PNS?
- They produce enzyme-rich, watery saliva
69
How is salivation regulated? What does salivation respond to? Where is the salivary centre located? And, which neural pathway initiates salivation?
- Is regulated by the innate reflex, which can be conditioned
- Responds to taste & texture of food in the mouth, mechanical stimulation of the mouth, or cerebral stimuli
- Salivary centre is located in the medulla, and initiates salivation via the ANS efferent neurons
70
How much saliva do the salvary glands produce per day? What is saliva composed of? What is the function of saliva? And, what is a bolus
- Produces 1 to 2 L per day of saliva
- 99.4% water, and salivary amylase, mucus, lysozyme, and bicarbonate
- Functions as a solvent for tastants, in movement of mouth, and in oral hygiene
- Bolus is food that is mixed with saliva
71
Where is saliva secreted? And, list the 3 pairs of salivary glands that it is produced by?
- Secreted in the mouth
| - Produced by the parotid, sublingual, and submandibular glands
72
How is the chewing reflex controlled? And what is its mechanism of action?
- Can be involuntary or voluntary
| - Works by relaxing and contracting the muscles of the jaw
73
How is motility in the mouth accomplished?
- Through the chew reflex, by mastication (chewing)
74
What is the mouth's primarly function?
- Motility and secretion primarily
| - Although it can contribute to digestion and absorption in a nonessential amount
75
What does the mouth consist of?
- Tongue, lips, teeth, palate, and uvula
76
Where is the efferent information sent out to coordinate the regulation of digestive function?
- Sent out to smooth muscle cells, endocrine cells, or exocrine cells
77
How is afferent information received and relayed to coordinate the regulation of digestive function?
- It is received by the chemo-mechano-osmo- receptors
| - And is relayed through a long reflex pathway to the CNS or a short reflex pathway to the ENS
78
Name the receptors that the walls of the digestive tract contain
- Chemoreceptors
- Mechanoreceptors
- Osmoreceptors
79
How is the regulation of the digestive function coordined?
- Through reflex pathways
80
What secretes the digestive hormones that regulate the digestive system? And, list individual secretants included
- Endocrine cells of the digestive tract
| - Including: Gastrin, cholecystokinin (CCK), secretin, and glucose-dependent peptide (GIP)
81
How is the PNS of the extrinsic innervations regulatory system mediated? And what do the postganglionic Parasympathetic nerve fibers form as well?
- Mediated by the Vagus nerve (X)
| - Forming a part of the ENS as well
82
How are the extrinsic innervations of the digestive system-mediated? And, how do these innervations affect the digestive system activity?
- They are mediated through the ANS
- increase in SNS = a decrease in digestive system activity
- increase in PNS = an increase in digestive system activity
83
What do the efferent neurons of the ENS innervate?
- They innervate smooth muscle cells, endocrine cells, and exocrine cells
84
What is the function of the ENS activity regulating mechanism? What is the ENS activity composed of? What do these neurons include?
- The ENS functions to coordinate digestive system activity independent of the CNS
- Composed of the submucosal plexus and myenteric plexus
- These plexuses include: afferent sensory neurons, interneurons, and efferent neurons.
85
What is the frequency of the slow-wave potentials, which varies in different regions of the digestive tract?
- Basic electric rhythm (BER)
86
Which factors are the degree of depolarization of the slow-wave potentials of the pacemaker cells dependent on?
- It is dependent on mechanical, neural, and hormonal factors.
87
What is the function of the pacemaker cells or interstitial cells of Cajal, in the autonomous smooth muscle function regulation mechanism?
- Function to generate slow-wave potentials. Upon reaching threshold, action potentials are generated from the slow-wave potentials, and smooth muscle contraction occurs
88
What does the autonomous smooth muscle function regulation mechanism contain?And, what is its function?
- It contains pacemaker cells or interstitial cells of Cajal
- Functions to generate slow-wave potentials. Upon reaching the threshold, action potentials are generated from the slow-wave potentials, and smooth muscle contraction occurs.
89
List the 4 mechanisms that regulation occurs by in the digestive system
- Autonomous smooth muscle function
- Enteric nervous system activity
- Extrinsic innervations
- Digestive hormones
90
What is regulated to optimize digestion and absorption in the digestive system?
- Motility and secretion
91
What is the description & function of Lipases? Which structures is it produced by? And what does it act on?
- It is an enzyme that digests fats
- It is produced by the salivary glands, stomach, and pancreas.
- It acts on triglycerides to break them down into monoglycerides and 2 fatty acids
92
How are fats absorbed?
- Fats are absorbed as monoglycerides and fatty acids
93
How are fats consumed? And how do they differ from carbs and proteins?
- Consumes as triglycerides
| - Differ in that they are not water solute and spontaneously aggregate in the aqueous lumen of the digestive tract
94
What is the function of Protease? And, what are the structures it is secreted from?
- An enzyme that digests protein
| - Secreted by the cells of the stomach and pancreas
95
How are proteins absorbed? (apical & basolateral)
- Occurs across the apical membrane as amino acids, dipeptides, or tripeptides.
- And across the basolateral membrane as only amino acids
96
Lis the 3 potential sources that protein can originate from
- From diet
- Secreted as enzymes from exocrine glands
- From sloughed-off cells in the digestive tract
97
What is the function of disaccharidases? What structure is it produced by? And what does it act on?
- Is an enzyme that digests carbs
- It is produced by the small intestine
- It acts on disaccharides to produce monosaccharides
98
What is the function of amylases? What structure is it produced by? And what does it act on?
- It is an enzyme that digests carbs
- It is produced by the salivary glands and the pancreas
- It acts on polysaccharides to form disaccharides
99
How are carbohydrates consumed as? List examples of carbs. And, in what form are carbohydrates absorbed?
- Carbs are consumed as disaccharides or polysaccharides.
- Ex. Cellulose, glycogen, sucrose, lactose, starch
- Carbs must be digested into monosaccharides to be absorbed
100
List the 3 energy-rich nutrient molecules that are consumed in the diet and must be processed by the digestive system
- Carbohydrates, proteins, and fats (lipids)
101
What is the serosa (outermost layer ) of the digestive tract composed of?
- It is composed of connective tissue and secrets serous fluid, which is important for the lubrication of the digestive organs and the surrounding viscera
102
What does the muscularis externa layer of the digestive tract contain?
- It contains an inner circular and an outer longitudinal muscle layer. Also contains the myenteric plexuses of the enteric nervous system
103
What does the submucosa layer of the digestive tract contain?
- It contains connective tissue, large blood & lymphatic vessels, and the submucosal plexus of the enteric nervous system
104
What is composed of smooth muscle cells in the mucosa layer?
- Muscularis mucosae
105
What is composed of connective and lymphoid tissue and also contains small blood, lymph vessels, and nerves?
- The lamina propria of the mucosa layer
106
What is an epithelial cell consisting of absorptive cells, exocrine cells, and endocrine cells?
- The mucous membrane of the mucosa layer
107
What is the mucosa layer of the digestive tract composed of?
- It is composed of a mucous membrane, the lamina propria, and the muscularis mucosae
108
Name the 4 layers of tissue in the digestive tract
- Mucosa, submucosa, muscularis externa, and serosa
109
Describe the digestive tract, and what makes it unique when compared to other compartments in the body (hint: luminal conditions)
- The digestive tract is a long, and hollow tube, that is continuous from the mouth to the anus.
- It has unique luminal conditions that serve the digestive processes well
- The luminal conditions / the lumen of the digestive tract has a high concentration of acid, enzymes, and microorganisms.
110
What are the components of the digestive system? And, list them per their category
- Includes the digestive gastrointestinal tract & the accessory organs
- Accessory organs include: The salivary glands, the pancreas, the gallbladder, and the liver.
111
Describe the digestive process of absorption
- Is the movement of digested nutrients, water, and electrolytes, from the digestive tract into the blood
112
Describe the digestive process of digestion
- Involves the biochemical breakdown of food molecules by hydrolysis, and is dependent on enzymes
113
Describe the digestive process of secretion
- Involves the secretion of digestive juices, which are secreted from exocrine glands and they facilitate the process of digestion
- It also involves the secretion of digestive hormones, which are secreted from endocrine glands and they regulate the digestive system function
114
Describe the digestive process of motility
- Involves digestive tract muscular contractions, in order to move and mix contents through the digestive tract
115
List the 4 processes involved in digestion
- Motility, secretion, digestion, and absorption
116
How is the digestive system regulated?
- Is regulated according to the mechanisms that maximize absorption of nutrients, water and electrolytes. Regardless of physiological needs
117
What are the functions of the digestive system?
- It is to transfer nutrients, water, and electrolytes to the blood to be used by the cells
118
How is the chewing reflex controlled? And what is its mechanism of action?
119
How is pepsingogen secretion regulation?
- By PNS acitvity and gastrin
120
What is the inactive form of pepsinogen called, how is it activated, and what is its activated form called?
- Pepsinogen is secreted as a zymogen (inactive) and must be activated by hydrochloric acid (HCl) before protein digestion can occur
- The active form of pepsingogen is called pepsin
121
Which structure secretes pepsingogen, and what is its function?
- Secreted by the chief cells, and functions to digest proteins
122
What are the components that make up the gastric mucosal barrier, to prevent hydrolicacid penetration?
- The luminal membranes are impermeable to hydrogen ions
- Cells are joined by tight junctions, impermeable to hydrogen ion
- mucus coating over gastric mucosa, protects it from hydrolicacid
123
How is the stomach protected from the acidic luminal environment?
- Protected by the gastric mucosal barrier and by rapid cell turnover.
124
Why is the gastric acidity important?
- important for molecular breakdown, protein denaturation, immunoprotection, and the activation of pepsinogen
125
What is the gastric acid secretion stimulated by? And what is it inhibited by?
- Stimulated by the PNS, histamine, and gastrin
| - It is inhibited by somatostatin
126
What are the functions of the gastric acid (HCI) secretions? And, which cells are they secreted by?
- Important for maintaining the acidic environment of the stomach and for the activation of pepsinogen
- Secreted by the parietal cells of the stomach
127
What is included in the gastric secretions in the stomach? And where are those secretory cells located?
- It includes gastric juices secreted by exocrine cells and, gastric hormones secreted by endocrine cells
- Located in the gastric pits
128
How is gastric motility regualted?
- Through cephalic, gastric, and intestinal phase factors
129
List the steps/events that involved in the gastric motility in the stomach
1. Filling, is mediated by receptive relaxation of smooth muscle layers of the stomach wall, regulated by the vagus nerve (X)
2. Mixing, occurs as a result of these peristalic contractions by the BER. Mixing occurs in the antrum primarily
3. Emptying, process involves small amounts of chyme being forced through the plyoric sphincter due to the strong antral peristaltic contractions
130
List the 3 stages that are involved in gastric motility in the stomach
1. Filling
2. Mixing
3. Emptying
131
Where does protein digestion begin, and what substance is it activated by?
- Begins in the stomach and is activated by pepsinogen
132
What makes it possible for the stomach to expand from 50mL to 1000 mL?
- The numerous rugae or stomach folds
133
What seals the exit of the stomach?
- The pyloric sphincter
134
What seals the entrance of the stomach?
- The lower esophageal (gastroesophageal) sphincter
135
Name the 3 parts that make up the stomach. Although there are no absorption of food, water, or electrolytes in the stomach, what are the 2 exceptions that get absorbed in the stomach?
- Fundus, body, and antrum
| - 2 exceptions are alcohol and acetylsalicylic acid (aspirin)
136
What is the function of the mucus secreted in the esophagus?
- functions to lubrication for the movement of the bolus through to the stomach
137
How is the pancreatic enzyme proteases activated? What are the steps involved?
- Proteases is secreted in zymogen form, and is activated
- in order for it to be activated, trypsinogen must be converted to its active form by the brush border enzyme enterokinase
138
How does the liver digest and absorb fats?
- Through it synthesis of bile
139
In newborns, Is the control of the external anal spinchter voluntary or involuntary? And, what comes as a result of this method of control?
- It is involuntary at birth, resulting in uncontrolled bowel movements
140
Why are acid reflux and regurgitation in newborns a common occurrence ?
- Due to immature control of the esophageal sphincter
141
What is the primary carbohydrate and energy source in breast-fed newborn?
- Lactose
142
At what stage of development can the digestive system take over the digestive functions?
- At birth (newborns)
143
In the developmental phase of the digestive system, what does the fetus experience?
- It experiences swallowing, gastric emptying, and intestinal propulsion
144
In the large intestines, how does chloride & water absorption occur?
- Following the absorption of Na+, both chloride (Cl-) and water follow passively down their electrochemical gradients
145
In the large intestines, how does sodium absorption occur?
- By transport proteins for sodium (Na+) and it's actively absorbed.
146
How does digestion occur in the large intestines, as there are no digestive enzymes present?
- Colonic bacteria present in the large intestines digest some material, such as cellulose
147
In the large intestine, how is alkaline secretion regulated?
- Regulated by short reflexes and PNS activity.
148
What is the secretion by the large intestines called? And, describe its property and functionality
- Alkaline secretant produced by the large intestine
- Property: A mucus fluid
- Functions: To lubricate the large intestine and to neutralize acids produced by colonic bacteria
149
Describe the defecation reflex mode of action
- This reflex is initiated by distension of the rectum, which stimulates stretch receptors
- Resulting in relaxation of the internal anal sphincter and in increased contraction of the sigmoid colon
- Finally, the voluntary relaxation of the external anal sphincter allows for defecation to occur
150
In the large intestines, which relfex mediates the exit of feces ?
- The defecation reflex
151
In the large intestines, describe the mode of action of mass movements. And, list the regulatory influences on mass movment
- Are large, peristaltic-like contractions that function to propel the feces toward the rectum.
- Regulated by the gastrocolic reflex, by gastrin, and by ANS activity.
152
In the large intestines, describe the mode of action of the haustral contractions
- Hautra is fomred by the contracted taeniae coli, which bulges from the large intestine
- Haustral contractions are responsible for the slow, segmentation-like mixing of the intestinal contents
153
In the large intestines, what are the 2 forms of motility called?
- Haustral contractions & mass movements
154
What are the primary functions of the large intestine?
- In the absorption of the remaining water, which serves to concentrate wastes into feces
- In the storage of feces until defecation.
155
List the digestive processes that the large intestine are involved in?
- Involved in all 4 digestive processes (motility, secretion, digestion, and absorption)
156
What is the structure called that is made up of 3 longitudinal bands of smooth muscle that extend the length of the large intestine?
- Taeniae coli
157
What seals the exit of the large intestines?
- The internal & external anal sphincters
158
What seals the entrance of the large intestine to the anus ?
- The ileocecal sphincter and valve
159
What are the divisions of the large intestines called?
- Cecum, appendix, colon (descending, transverese, ascending, sigmoid colons), and rectum
160
In the small intestines, how does water reabsorption occur?
- Water is absorbed passively
161
How is calcium absorbed in the small intestine? How does calcium cross the basolateral membrane? And, which hormones regulate the absorption of calcium?
- Calcium must bind to a brush-border calcium-binding protein, to be endocytosed into the small intestine
- Across the basolateral membrane, occurs by a Ca2+ -ATPase
- Ca2+ absorption is regulated by the hormone’s parathyroid hormone and calcitriol
162
In old age, what are some examples of markers that decrease nutritional intake?
- Diffculties with mastication, due to dental changes
- Decreases in olfaction
- Decreases in gustation
163
In old age, what leads to an increased incidence of cirrhosis in the liver?
- Cumulative damage to the liver
164
In old age, what leads to an increased incidence of cancer in the digestive system?
- cumulative damage
165
What can decreases in smooth muscle tone lead to?
- Leads to decreased motility throughout the digestive tract, weaker peristaltic contractions, and increased incidences of gastroesophageal reflux disease (GERD), and constipation
166
What are some examples that indicate a decrease in digestive function? In relation to old age
- Decreases in rate of epithelial stem cell division
| - Decreases in mucous secretion, and in smooth muscle tone
167
Which age group begins to experience an overall decrease in digestive system activity?
- Senior citizens
168
What period of lifetime does the digestive system become fully mature?
- During childhood
169
In the digestive system, list the anatomical changes that are brought about in the first year of life
- Widening of the villi, deepening of the crypts, and development of gut-associated lymphoid tissue (GALT)
- Also, colonic bacteria begin to establish themselves
170
In newborns, Is the control of the external anal spinchter voluntary or involuntary? And, what comes as a result of this method of control?
- It is involuntary at birth, resulting in uncontrolled bowel movements
