L47, 50, 51, 53 GI tract Flashcards
1
Q
L47
What structures are found in the oral cavity?
A
Tongue (taste, food movement), teeth (mastication), and salivary glands (begin chemical digestion).
2
Q
L47
What cranial nerve provides sensory innervation to the oral cavity?
A
Trigeminal nerve (CN V).
Upper half: Maxillary branch (V2)
Lower half: Mandibular branch (V3)
3
Q
L47
How is the tongue innervated?
A
Anterior 2/3: Sensory - CN V3; Taste - CN VII (chorda tympani)
Posterior 1/3: Sensory and taste - CN IX
Very posterior tongue: Sensory and taste - CN X
Motor: CN XII (except palatoglossus - CN X)
4
Q
L47
What are the three major salivary glands and their innervations?
A
Parotid gland (~20%): CN IX
Submandibular gland (~60%): CN VII
Sublingual gland (~10%): CN VII
5
Q
L47
What are the main functions of saliva?
A
Lubrication, pH buffering, swallowing aid, oral cavity cleaning, and starting chemical digestion.
6
Q
L47
What prevents food from entering the nasal cavity during swallowing?
A
The uvula swings superiorly to close the pharyngeal isthmus.
7
Q
L47
How is aspiration of food into the trachea prevented?
A
Larynx elevates, epiglottis covers laryngeal inlet, and vocal cords close.
8
Q
L47
What are the three phases of swallowing?
A
Oral phase: Chewing and bolus formation (voluntary)
Pharyngeal phase: Bolus pushed backward, soft palate and laryngeal inlet close (involuntary)
Oesophageal phase: Peristaltic movements transport bolus.
9
Q
L47
Where are the four constriction sites of the oesophagus?
A
- Beginning of oesophagus
- Crossing aortic arch
- Crossing left main bronchus
- Oesophageal hiatus (diaphragm)
10
Q
L47
What structures are included in the foregut?
A
Oesophagus, stomach, liver, gallbladder, pancreas, spleen, and first half of duodenum.
11
Q
L47
What blood vessel supplies the foregut?
A
Coeliac trunk (branches into: common hepatic artery, splenic artery, and left gastric artery).
12
Q
L47
What is the role of the gastro-oesophageal junction and pyloric sphincter?
A
Gastro-oesophageal junction: Prevents acid reflux.
Pyloric sphincter: Controls chyme passage into the duodenum.
13
Q
L47
What are the main functions of the liver?
A
Metabolism, detoxification, bile production.
14
Q
L47
How does blood flow through the liver?
A
Venous blood enters via the hepatic portal vein.
Nutrients absorbed, toxins removed.
Blood exits to inferior vena cava via hepatic veins.
15
Q
What is the hepatobiliary tree?
A
Ducts transporting bile from the liver to the duodenum; includes bile duct and cystic duct.
16
Q
L47
What are the functions of the pancreas?
A
Exocrine: Digestive enzymes + bicarbonate secretion
Endocrine: Insulin and glucagon secretion
17
Q
L47
What is the spleen’s function?
A
Filters blood, removes dead RBCs, stores WBCs, immune response.
18
Q
L47
Where does the midgut start and end?
A
Major duodenal papilla (duodenum) to the first 2/3 of the transverse colon.
19
Q
L47
What is the main artery of the midgut?
A
Superior mesenteric artery.
20
Q
L47
What parts of the GIT are supplied by the superior mesenteric artery?
A
Pancreas, duodenum (3rd/4th parts), jejunum, ileum, caecum, ascending colon, 2/3 transverse colon.
21
Q
L47
Where is the ileocecal junction?
A
Between the ileum and caecum (right iliac fossa).
22
Q
L47
What is absorbed in the jejunum vs ileum?
A
Jejunum: General nutrient absorption.
Ileum: Vitamin B12 and bile salts absorption.
23
Q
L47
Where does the hindgut start and end?
A
Last 1/3 of transverse colon to upper anal canal.
24
Q
L47
What artery supplies the hindgut?
A
Inferior mesenteric artery.
25
# L47
What parts are supplied by the inferior mesenteric artery?
Last 1/3 transverse colon, descending colon, sigmoid colon, rectum.
26
# L47
What nerves provide parasympathetic innervation to the GIT?
Foregut and midgut: Vagus nerve
Hindgut: Pelvic splanchnic nerves
27
# L47
What nerves provide sympathetic innervation to the GIT?
Thoracic and lumbar splanchnic nerves.
28
# L47
What is the enteric nervous system?
Local, intrinsic network that controls GIT functions.
29
# L47
How is the rectum different from the colon?
Rectum has no taenia coli or omental appendices.
30
# L47
What controls the internal vs external anal sphincters?
Internal: Involuntary (autonomic)
External: Voluntary (somatic, pudendal nerve)
31
# L47
What happens during the defecation reflex?
1. Rectal stretch.
2. Sigmoid contraction.
3. Internal sphincter relaxes.
4. Diaphragm and abdominal muscles contract voluntarily.
32
# L47
How does venous drainage differ above and below the pectinate line?
Above: Drains to hepatic portal system.
Below: Drains to inferior vena cava.
33
# L47
What causes haemorrhoids?
Swelling of anal veins due to increased venous pressure (e.g., constipation, pregnancy).
34
# L47
What is the median sulcus of the tongue?
A longitudinal groove running down the midline of the tongue, dividing it into symmetrical halves.
35
# L47
How many muscles make up the tongue, and how are they grouped?
8 muscles total:
4 intrinsic (change shape of tongue)
4 extrinsic (move the tongue)
36
# L47
Which nerve innervates most tongue muscles, and what is the exception?
Hypoglossal nerve (CN XII) innervates all except palatoglossus (innervated by vagus nerve CN X).
37
# L47
What are the structural differences between submandibular gland lobes?
Deep lobe: Inside oral cavity
Superficial lobe: Outside oral cavity
38
# L47
Through which ganglion is the parotid gland innervated?
Otic ganglion (parasympathetic fibers from CN IX).
39
# L47
Through which ganglion are the submandibular and sublingual glands innervated?
Submandibular ganglion (parasympathetic fibers from CN VII).
40
# L47
What is the ‘stomach bed’?
The anatomical structures the stomach rests on, including pancreas, spleen, left kidney, left adrenal gland, transverse colon, and diaphragm.
41
# L47
What is the function of the lesser and greater omenta?
Lesser omentum: Connects lesser curvature of stomach to liver.
Greater omentum: Hangs from greater curvature; acts like a protective "apron" of fat over intestines.
42
# L47
Which structures pass through the porta hepatis?
Hepatic artery proper (in)
Hepatic portal vein (in)
Common hepatic duct (out)
43
# L47
Why are cancers of the body and tail of the pancreas detected later than those in the head?
Because body and tail tumors cause symptoms later (no early blockage of bile ducts), unlike head tumors which block bile flow causing early jaundice.
44
# L47
What are the five parts of the pancreas?
Uncinate process, head, neck, body, tail.
45
# L47
What is the main anatomical landmark distinguishing midgut from hindgut?
The last third of the transverse colon marks the transition from midgut to hindgut.
46
# L47
What are taeniae coli?
Three longitudinal bands of smooth muscle running along the large intestine.
47
# L47
What are omental appendices?
Fat-filled pouches attached to the colon's outer surface.
48
# L47
What is a prevertebral plexus?
A network of autonomic nerves around the aorta that supplies abdominal organs.
49
# L47
Which plexus innervates pelvic organs including the rectum and anal canal?
Inferior hypogastric plexus.
50
# L47
What muscles form the levator ani, and what are their roles?
Puborectalis: Forms a sling around the rectum, crucial for continence.
Pubococcygeus: Supports pelvic organs.
Iliococcygeus: Elevates pelvic floor.
51
# L47
What angle does the puborectalis muscle create, and why is it important?
Forms an acute anorectal angle (~80°) maintaining continence by preventing premature fecal passage.
52
# L47
What is the ano-cutaneous line (white line of Hilton)?
A visible line marking the transition between the internal (visceral) and external (somatic) zones of the anal canal.
53
# L47
What is the pectinate (dentate) line?
A landmark dividing the upper 2/3 (visceral) and lower 1/3 (somatic) anal canal regions, with different nerve and blood supplies.
54
# L47
Which cranial nerve provides sensory innervation to the upper half of the oral cavity?
A) Mandibular branch of CN V
B) Maxillary branch of CN V
C) Facial nerve (CN VII)
D) Vagus nerve (CN X)
Answer: B) Maxillary branch of CN V
55
# L47
The posterior 1/3 of the tongue is innervated for both sensation and taste by:
A) Facial nerve (CN VII)
B) Glossopharyngeal nerve (CN IX)
C) Vagus nerve (CN X)
D) Hypoglossal nerve (CN XII)
Glossopharyngeal nerve (CN IX)
56
# L47
The largest salivary gland is the:
A) Submandibular gland
B) Parotid gland
C) Sublingual gland
D) Lingual gland
B) Parotid gland
57
# L47
What structure prevents the bolus from entering the nasal cavity during swallowing?
A) Epiglottis
B) Soft palate and uvula
C) Laryngeal inlet
D) Tongue base
Soft palate and uvula
58
# L47
What innervates the parotid gland to stimulate saliva secretion?
A) Vagus nerve (CN X)
B) Facial nerve (CN VII)
C) Glossopharyngeal nerve (CN IX)
D) Hypoglossal nerve (CN XII)
Glossopharyngeal nerve (CN IX)
59
# L47
Which of the following is NOT a constriction site of the oesophagus?
A) Oesophageal hiatus
B) Crossing of the right bronchus
C) Beginning of the oesophagus
D) Crossing of the aortic arch
B) Crossing of the right bronchus
(It’s the left main bronchus)
60
# L47
Which artery is the primary supply to the foregut structures?
A) Superior mesenteric artery
B) Inferior mesenteric artery
C) Coeliac trunk
D) Hepatic portal vein
C) Coeliac trunk
61
# L47
What anatomical feature marks the transition between midgut and hindgut?
A) Hepatic flexure
B) Last third of the transverse colon
C) Major duodenal papilla
D) Rectum
Last third of the transverse colon
62
# L47
Which of the following statements about the pancreas is TRUE?
A) The pancreas lies anterior to the stomach
B) The tail of the pancreas extends toward the liver
C) Tumors in the head of the pancreas are detected earlier than tail tumors
D) Pancreatic ducts drain directly into the jejunum
C) Tumors in the head of the pancreas are detected earlier than tail tumors
63
# L47
The mesentery suspending the jejunum and ileum contains all EXCEPT:
A) Fat
B) Blood vessels
C) Lymph nodes (Peyer's patches)
D) Nerve plexuses
C) Lymph nodes (Peyer's patches)
(Peyer's patches are in the wall of the ileum, not the mesentery.)
64
# L47
The hepatic portal vein is formed mainly by which two veins?
A) Inferior mesenteric and renal vein
B) Splenic and superior mesenteric veins
C) Superior mesenteric and inferior vena cava
D) Splenic and renal veins
B) Splenic and superior mesenteric veins
65
# L47
Which part of the gastrointestinal tract contains taeniae coli and haustra?
A) Jejunum
B) Ileum
C) Colon (large intestine)
D) Rectum
C) Colon (large intestine)
66
# L47
Defecation involves all of the following EXCEPT:
A) Stretching of rectum
B) Relaxation of internal anal sphincter
C) Relaxation of external anal sphincter involuntarily
D) Contraction of abdominal muscles
C) Relaxation of external anal sphincter involuntarily
(External anal sphincter is voluntary!)
67
# L47
Which nerve controls voluntary contraction of the external anal sphincter?
A) Vagus nerve
B) Pudendal nerve
C) Pelvic splanchnic nerve
D) Thoracic splanchnic nerve
B) Pudendal nerve
68
# L47
Blood from the inferior rectum primarily drains into:
A) Hepatic portal vein
B) Inferior vena cava
C) Superior mesenteric vein
D) Splenic vein
B) Inferior vena cava
69
# L47
Which structure makes the anorectal angle important for continence?
A) Pubococcygeus
B) Puborectalis
C) Iliococcygeus
D) Levator ani
B) Puborectalis
70
# L47
The greater omentum:
A) Connects the liver to the lesser curvature of the stomach
B) Connects the stomach to the transverse colon
C) Hangs from the greater curvature and acts as a protective fat apron
D) Is part of the spleen's blood supply
C) Hangs from the greater curvature and acts as a protective fat apron
71
# L47
The midgut structures include all EXCEPT:
A) Caecum
B) Appendix
C) Descending colon
D) Jejunum
C) Descending colon
(It's hindgut.)
72
# L47
Which ganglion is associated with innervation of the submandibular gland?
A) Otic ganglion
B) Pterygopalatine ganglion
C) Submandibular ganglion
D) Celiac ganglion
C) Submandibular ganglion
73
# L47
In the foregut, bile and pancreatic juices empty into the duodenum at the:
A) Minor duodenal papilla
B) Major duodenal papilla
C) Ampulla of Vater
D) Both B and C
D) Both B and C
(The ampulla of Vater opens at the major duodenal papilla.)
74
# L51
What are the four layers of the GI tract (innermost to outermost)?
Mucosa (epithelium, lamina propria, muscularis mucosae)
Submucosa (blood vessels, glands, Meissner's plexus)
Muscularis externa (circular and longitudinal muscle, Auerbach's plexus)
Serosa (outermost covering)
75
# L51
Where is skeletal muscle found in the GI tract?
Upper oesophagus (swallowing)
External anal sphincter (defecation)
76
# L51
Where is smooth muscle found in the GI tract?
Throughout the GI tract walls (except areas with skeletal muscle).
Also found in hollow organs (blood vessels, uterus).
77
# L51
What are the two types of electrical activity in GI smooth muscle?
Slow waves: Spontaneous rhythmic changes in membrane potential.
Spike potentials: True action potentials triggering contractions.
78
# L51
What generates slow waves?
Interstitial Cells of Cajal (ICC), the pacemakers of the GI tract.
79
# L51
What triggers spike potentials?
Slow waves reaching threshold voltage → Ca²⁺ influx → muscle contraction.
80
# L51
What do more spike potentials cause?
Stronger contractions.
81
# L51
How are spike potentials propagated?
Via gap junctions for coordinated movement.
82
# L51
What is the role of calcium in smooth muscle contraction?
Spike potentials open Ca²⁺ channels.
Ca²⁺ influx activates contraction mechanisms in smooth muscle.
83
# L51
What is the ENS often called?
The "Second Brain."
84
# L51
What are the two plexuses of the ENS and their functions?
Myenteric (Auerbach's) Plexus: Controls motility (Movement).
Submucosal (Meissner's) Plexus: Controls secretion and absorption (Secretion).
85
# L51
What is the effect of the parasympathetic nervous system (PNS) on the GI tract?
Increases motility and secretion (via ACh).
86
# L51
What is the effect of the sympathetic nervous system (SNS) on the GI tract?
Decreases motility and secretion (via NE).
87
# L51
What are Intrinsic Primary Afferent Neurons (IPANs)?
Sensory neurons that monitor changes in the GI tract (e.g., pH, stretch) and activate reflexes.
88
# L51
Which neurotransmitters are used by IPANs?
Serotonin (5-HT), Substance P, Calcitonin Gene-Related Peptide (CGRP).
89
# L51
What is the Gastrocolic Reflex?
Eating stimulates colonic contractions → urge to defecate.
90
# L51
What is the Ileogastric Reflex?
Ileum distension inhibits gastric emptying.
91
# L51
What is the Enterogastric Reflex?
Duodenal distension inhibits stomach motility.
92
# L51
What are the three phases of gastric motility?
1. Cephalic phase (anticipatory): Sight/smell of food triggers acid secretion (via vagus nerve, ACh).
2. Gastric phase (digestive): Stomach distension & amino acids stimulate gastrin release → acid & motility.
3. Intestinal phase (inhibitory): Duodenum detects contents and releases hormones to inhibit stomach activity.
93
# L51
Which hormones are involved in the intestinal phase?
Secretin (low pH)
CCK (high fat)
Gastrin (amino acids)
GIP (carbohydrates)
94
# L51
What are the two types of small intestinal movements?
Segmental contractions: Mixing contents with mucosa (rhythmic, local).
Peristaltic contractions: Propelling food along intestines (slower transport).
95
# L51
What is pathological peristalsis?
Inflammation: Causes rapid peristalsis → diarrhea.
Reverse peristalsis: Leads to vomiting or slowed digestion.
96
# L51
What is the MMC and what hormone regulates it?
| MIGRATING MOTOR COMPLEX
A fasting-period cleaning wave that sweeps residual material through the intestines.
Regulated by motilin
97
# L51
What are the four phases of MMC?
Quiescence (rest)
Increased action potentials
Peak intense contractions
Declining activity → quiescence again
98
# L51
What stops MMC?
Feeding (via the vagus nerve).
99
# L51
What are the two types of colonic movements?
Rhythmic Phasic Contractions (RCPs)
Giant Migrating Contractions (GMCs)
100
# L51
What are RCPs and their types?
Rhythmic Phasic Contractions (RCPs)
Giant Migrating Contractions (GMCs)
101
# L51
What are RCPs and their types?
| rythmic phase contractions
Short-duration (2–3 sec): Mixing only.
Long-duration (15–20 sec): Short-distance propulsion.Short-duration (2–3 sec): Mixing only.
Long-duration (15–20 sec): Short-distance propulsion.
102
# L51
What are GMCs?
Large, powerful, lumen-occluding contractions.
Propel contents rapidly over large distances → Mass movement.
103
# L51
When do GMCs occur?
Randomly, 2–10 times/day, during fasting and post-meal states.
104
# L51
What are the core control systems of GI motility?
ENS (local control)
ANS (parasympathetic increases, sympathetic decreases motility)
Local reflexes (e.g., gastrocolic, ileogastric, enterogastric)
105
# L51
What are the two types of smooth muscle organization in the GI tract?
Single-unit smooth muscle: Most of the GI tract — electrically coupled by gap junctions for coordinated contraction.
Multi-unit smooth muscle: Less common — found in areas needing finer control (like the iris of the eye, not the gut, but conceptually important).
Extra note: In the GI tract, single-unit smooth muscle dominates for peristalsis and segmentation.
Extra note: In the GI tract, single-unit smooth muscle dominates for peristalsis and segmentation.
106
# L51
What factors can modulate (increase/decrease) slow waves?
Stretch of smooth muscle: ↑ Depolarization.
Parasympathetic stimulation (ACh): ↑ Slow wave depolarization.
Sympathetic stimulation (NE): ↓ Slow wave activity (hyperpolarization).
107
# L51
How do slow waves differ from spike potentials in terms of contraction?
Slow waves alone: Do NOT cause contractions.
Spike potentials: When superimposed on slow waves, trigger contractions by Ca²⁺ influx.
108
# L51
Which other important neurotransmitters besides ACh and NE modulate the ENS?
Serotonin (5-HT): Triggers local reflexes, important in motility and secretion.
Substance P: Excitatory — promotes motility.
VIP (Vasoactive Intestinal Peptide): Relaxes smooth muscle and stimulates secretion.
NO (Nitric Oxide): Causes relaxation of smooth muscle.
109
# L51
What defines an intrinsic reflex within the GI tract?
Reflexes that are mediated solely by the ENS, without involving the CNS.
Examples:
Peristaltic reflex (stretch → contraction upstream, relaxation downstream).
Secretion reflexes within intestinal segments.
110
# L51
How does gastric motility differ from intestinal and colonic motility?
Stomach: Stores and mixes food (strong propulsive contractions during emptying).
Small intestine: Mainly segmentation for mixing; some slow peristalsis for absorption.
Colon: Slow movement to solidify contents (with intermittent mass movements).
111
# L51
What are the two forms of reverse peristalsis?
Oesophageal reverse peristalsis: Precursor to vomiting.
Ileal reverse peristalsis: Extends time for absorption during digestion.
112
# L51
What happens if the MMC is impaired?
Leads to bacterial overgrowth (because debris is not cleared).
May contribute to bloating, malabsorption, and small intestinal bacterial overgrowth (SIBO).
113
# L51
Which muscle type is found in the external anal sphincter?
A) Smooth muscle
B) Cardiac muscle
C) Skeletal muscle
D) Visceral muscle
C) Skeletal muscle
114
# L51
What is the function of Interstitial Cells of Cajal (ICC)?
A) Secrete digestive enzymes
B) Act as GI tract pacemakers
C) Absorb nutrients
D) Release hormones like gastrin
B) Act as GI tract pacemakers
115
# L51
What type of GI smooth muscle activity is described as true action potentials?
A) Slow waves
B) Spike potentials
C) Segmental contractions
D) Peristaltic contractions
B) Spike potentials
116
# L51
Which neurotransmitter stimulates increased motility and secretion in the GI tract?
A) Noradrenaline (NE)
B) Acetylcholine (ACh)
C) Nitric Oxide (NO)
D) VIP (Vasoactive Intestinal Peptide)
B) Acetylcholine (ACh)
117
# L51
In which GI layer is the submucosal (Meissner's) plexus located?
A) Serosa
B) Submucosa
C) Muscularis externa
D) Mucosa
B) Submucosa
118
# L51
What happens when slow waves alone occur without spike potentials?
A) Strong smooth muscle contraction
B) Weak or no contraction
C) Immediate secretion of hormones
D) Reverse peristalsis
B) Weak or no contraction
119
# L51
Which of the following inhibits gastric motility during the intestinal phase?
A) Gastrin
B) Secretin
C) Histamine
D) Motilin
B) Secretin
120
# L51
Which phase of gastric motility is triggered by the sight or smell of food?
A) Gastric phase
B) Cephalic phase
C) Intestinal phase
D) Migrating Motor Complex phase
B) Cephalic phase
121
# L51
Which hormone is responsible for regulating the Migrating Motor Complex (MMC)?
A) Gastrin
B) Cholecystokinin (CCK)
C) Motilin
D) Secretin
C) Motilin
122
# L51
What type of GI movement is mainly responsible for mixing contents with the mucosa?
A) Peristaltic contraction
B) Segmental contraction
C) Reverse peristalsis
D) Giant Migrating Contraction
B) Segmental contraction
123
# L51
What type of peristalsis is involved in vomiting?
A) Rapid forward peristalsis
B) Giant migrating contractions
C) Reverse peristalsis
D) Segmental mixing
C) Reverse peristalsis
124
# L51
Which best describes short-duration rhythmic phasic contractions (RCPs) in the colon?
A) Strongly propelling feces over long distances
B) Mixing without significant propagation
C) Complete lumen occlusion
D) Rapid forward mass movement
B) Mixing without significant propagation
124
# L51
Which neurotransmitter is important for local reflexes and intestinal secretion?
A) Noradrenaline (NE)
B) Serotonin (5-HT)
C) Dopamine
D) Acetylcholine (ACh)
B) Serotonin (5-HT)
125
# L51
Giant Migrating Contractions (GMCs) in the colon are:
A) Short-lived, non-propagating contractions
B) Weak, slow contractions
C) Large, forceful contractions propelling feces over long distances
D) Inhibited completely during fasting
C) Large, forceful contractions propelling feces over long distances
126
# L51
What happens to the MMC when food is ingested?
A) It intensifies
B) It weakens slowly
C) It stops
D) It speeds up to aid digestion
C) It stops
127
# L51
Which reflex describes ileum distension inhibiting gastric emptying?
A) Gastrocolic reflex
B) Ileogastric reflex
C) Enterogastric reflex
D) Gastroileal reflex
B) Ileogastric reflex
128
# L51
What would sympathetic stimulation of the GI tract cause?
A) Increased peristalsis and secretion
B) Decreased motility and secretion
C) Spontaneous vomiting
D) Reverse segmental contractions
B) Decreased motility and secretion
129
# L51
What best defines an intrinsic GI reflex?
A) Reflex initiated by the CNS only
B) Reflex mediated completely by the ENS without CNS input
C) Voluntary control reflex
D) Hormone-controlled reflex
B) Reflex mediated completely by the ENS without CNS input
130
# L51
Which neurotransmitter promotes smooth muscle relaxation in the GI tract?
A) Acetylcholine (ACh)
B) Noradrenaline (NE)
C) Nitric Oxide (NO)
D) Substance P
C) Nitric Oxide (NO)
131
# L51
What is the correct order of MMC phases?
A) Increased activity → Quiescence → Peak activity → Decline
B) Quiescence → Increased activity → Peak contractions → Decline
C) Peak contractions → Increased activity → Quiescence → Decline
D) Increased activity → Peak contractions → Decline → Reverse contractions
B) Quiescence → Increased activity → Peak contractions → Decline
132
# L50
What is the function of mastication?
First step in digestion.
Mashes and crushes food into a bolus small enough to swallow.
Mixes food with saliva.
Increases surface area for enzymatic action.
133
# L50
What movements and structures are involved in mastication?
Mandible: moves up and down; incisors bite food.
Molars: grind food side-to-side, forming a bolus.
Tongue: manipulates food within the mouth.
134
# L50
Which muscles are responsible for jaw closing?
Temporalis
Masseter
Medial pterygoid (All innervated by the 5th cranial nerve – Trigeminal nerve.)
135
# L50
Which muscle is responsible for jaw opening?
Lateral pterygoid (also innervated by the Trigeminal nerve).
136
# L50
What is the Central Pattern Generator (CPG) in mastication?
A neural network in the brainstem controlling rhythmic jaw movements.
Generates automatic chewing rhythms without conscious input.
Contains a Rhythm Generator (basic rhythm) and a Burst Generator (adapts movement to food type).
137
# L50
How is mastication controlled beyond reflex actions?
Sensory feedback from dental and periodontal mechanoreceptors adjusts chewing force and movement.
Cortex provides voluntary control based on food texture (e.g., steak vs jelly).
138
# L50
How does sensory feedback protect teeth during mastication?
Mechanoreceptors detect excessive biting forces.
If biting force is too high, jaw-closing muscles are inhibited.
Prevents damage to teeth during chewing.
139
# L50
What is the role of periodontal mechanoreceptors?
Detect pressure and texture of food.
Provide tactile feedback to brainstem CPG.
Fine-tune jaw movement to optimise chewing.
140
What is deglutition?
Swallowing: process of moving food from the mouth to the stomach.
141
# L50
What are the three phases of deglutition?
Oral Phase: voluntary; bolus pushed to pharynx by tongue.
Pharyngeal Phase: involuntary; prevents entry of food into nasal cavity or airway.
Oesophageal Phase: involuntary; food propelled into stomach.
142
What controls deglutition?
Swallowing centre in the medulla oblongata.
Involves over 25 muscles.
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What happens during the pharyngeal phase?
Pressure receptors in palate/pharynx activate swallowing centre.
Soft palate lifts, sealing off nasal cavity.
Larynx raises and glottis closes (cannot breathe during this phase).
Upper oesophageal sphincter opens.
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How long does the pharyngeal phase last?
Approximately 1 second.
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What protects the respiratory tract during swallowing?
Epiglottis closes over the trachea.
Vocal cords close tightly.
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What structures are involved in the oesophageal phase?
Upper Oesophageal Sphincter (UOS): opens to allow food entry.
Lower Oesophageal Sphincter (LOS): opens to allow food into the stomach.
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What is oesophageal peristalsis?
Wave-like muscle contractions that push the bolus towards the stomach.
Independent of gravity (works even if upside down!).
Involves:
- Skeletal muscle (upper third).
- Mixed skeletal and smooth muscle (middle third).
- Smooth muscle (lower third).
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What controls oesophageal peristalsis?
Extrinsic vagal nerves (parasympathetic).
Intrinsic enteric nerves (enteric nervous system).
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How does the Central Pattern Generator (CPG) system coordinate with other functions?
The masticatory CPG interacts with:
- Respiratory CPG (breathing).
- Swallowing CPG (deglutition).
Ensures breathing and swallowing are properly coordinated to prevent aspiration.
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What are the phases of mastication control?
Basic Rhythm Generation: by brainstem CPG (does not need sensory feedback).
Adaptation/Modification: requires sensory feedback (e.g., food viscosity, size, texture).
Voluntary Control: initiated or altered by the motor cortex depending on food type.
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What is the role of cortical input in mastication?
Cortex can voluntarily initiate or modify chewing based on food properties.
For example: Hard crackers require more powerful bites; soft jelly needs lighter chewing.
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What did original theories suggest about chewing control?
Originally thought to be a simple sequence of:
Biting food → triggers jaw-opening reflex → stretches muscles → triggers jaw-closing reflex.
Now replaced by the CPG model, recognising fine-tuned sensory feedback and voluntary control.
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Why is it important that mastication adapts based on food type?
Prevents damage to teeth.
Ensures food is appropriately broken down for easier swallowing and digestion.
Maintains oral and dental health over a lifetime.
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How important is the periodontal ligament in mastication?
Houses highly sensitive mechanoreceptors.
Protects teeth by monitoring stress and strain during biting.
Vital for the "fine control" of bite force.
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What is Trigeminal Neuralgia and how does it relate to mastication?
Trigeminal Neuralgia: a chronic pain condition affecting the trigeminal nerve.
Causes episodes of sudden, severe, shock-like facial pain.
Can severely affect mastication due to pain during jaw movements.
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Why is swallowing described as an "all-or-none" reflex?
Once initiated, the swallowing reflex cannot be stopped voluntarily.
Ensures food is moved safely and quickly from mouth to oesophagus without aspiration.
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What is the timing of the oesophageal phase of swallowing?
Lasts 8 to 20 seconds depending on:
Size and consistency of the food bolus.
Strength of peristaltic waves.
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What happens if there is a failure of oesophageal peristalsis?
Bolus may remain stuck (dysphagia).
Can lead to regurgitation, aspiration, or discomfort.
Conditions like achalasia involve peristaltic failure and/or failure of LOS relaxation.
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What ensures that food enters the stomach even if upside down?
Peristaltic waves:
- Contract behind the bolus.
- Relax in front of the bolus.
Controlled by vagal and enteric nerves.
Gravity is not essential for food movement!
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What is the primary function of mastication?
A) To initiate salivary enzyme activation
B) To move food into the stomach
C) To crush and mix food, forming a bolus
D) To trigger the swallowing reflex
Answer: C – Mastication crushes and mixes food into a bolus.
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Which nerve innervates the muscles of mastication?
A) Facial nerve (VII)
B) Hypoglossal nerve (XII)
C) Trigeminal nerve (V)
D) Glossopharyngeal nerve (IX)
✅ Answer: C – All jaw-opening and jaw-closing muscles are innervated by the trigeminal nerve.
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What muscles are responsible for jaw closing during mastication?
A) Masseter, Temporalis, Medial pterygoid
B) Lateral pterygoid, Masseter
C) Buccinator, Lateral pterygoid, Masseter
D) Temporalis, Buccinator, Orbicularis oris
✅ Answer: A – Jaw closing involves masseter, temporalis, and medial pterygoid muscles.
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What is the role of the Central Pattern Generator (CPG) in mastication?
A) Stimulates saliva production
B) Coordinates rhythmic jaw movements
C) Controls taste perception
D) Initiates oesophageal peristalsis
✅ Answer: B – CPG in the brainstem generates rhythmic, repetitive jaw movements.
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Which structure provides sensory feedback to adjust bite force?
A) Soft palate receptors
B) Periodontal ligament mechanoreceptors
C) Laryngeal stretch receptors
D) Oesophageal stretch receptors
Answer: B – The periodontal ligament contains mechanoreceptors crucial for fine-tuning bite force.
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What best describes the pharyngeal phase of swallowing?
A) Voluntary; can be paused at will
B) Involuntary; prevents entry into nasal cavity and airway
C) Voluntary; contracts the stomach
D) Involuntary; relaxes the lower oesophageal sphincter
✅ Answer: B – Pharyngeal phase is involuntary and protects airway and nasal cavity.
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Which structure closes off the trachea during swallowing?
A) Soft palate
B) Glottis
C) Epiglottis
D) Vocal cords
Answer: C – The epiglottis folds down to close off the trachea.
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How long does the oesophageal phase of deglutition typically last?
A) 0.5–1 second
B) 2–5 seconds
C) 8–20 seconds
D) 30–40 seconds
Answer: C – The oesophageal phase usually lasts 8–20 seconds.
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Peristalsis in the oesophagus is primarily controlled by:
A) Only the vagus nerve
B) Only the enteric nervous system
C) Both vagus nerve and enteric nervous system
D) Voluntary motor cortex control
✅ Answer: C – Peristalsis is controlled by both extrinsic (vagal) and intrinsic (enteric) nerves.
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Why is swallowing considered an "all-or-none" reflex?
A) It can be paused mid-way if needed
B) Once initiated, it must be completed
C) It only involves skeletal muscles
D) It requires voluntary control at all stages
Answer: B – Once initiated, swallowing proceeds automatically and cannot be stopped.
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Which of the following statements is TRUE about mastication control?
A) Chewing pattern is completely reflexive and does not involve the cortex.
B) Central Pattern Generator modifies chewing based on respiratory rate.
C) Cortex can modify chewing movements depending on food type.
D) Mastication is controlled solely by the trigeminal nerve without any brainstem input.
Answer: C – The cortex can modify mastication based on sensory input (e.g., hardness of food).
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Which muscle is responsible for jaw opening during mastication?
A) Masseter
B) Temporalis
C) Medial pterygoid
D) Lateral pterygoid
Answer: D – Only the lateral pterygoid opens the jaw.
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During swallowing, what structure seals off the nasal cavity?
A) Epiglottis
B) Soft palate
C) Vocal cords
D) Larynx
Answer: B – The soft palate lifts up to close the nasal cavity.
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Which description of peristalsis is CORRECT?
A) Peristalsis relies purely on gravity to move food.
B) Peristalsis uses wave-like muscular contractions behind the bolus.
C) Peristalsis only occurs if the person is lying flat.
D) Peristalsis uses voluntary skeletal muscle throughout.
Answer: B – It is wave-like contraction pushing the bolus down, regardless of gravity.
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What controls fine-tuning of bite force during mastication?
A) Trigeminal nerve alone
B) Central Pattern Generator only
C) Sensory feedback from dental mechanoreceptors
D) Swallowing centre in the medulla
Answer: C – Periodontal sensory receptors fine-tune bite force.
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What would happen if the lower oesophageal sphincter (LOS) failed to open during swallowing?
A) Food would enter the trachea.
B) Food would be regurgitated back into the mouth.
C) Food would build up in the oesophagus.
D) Food would pass straight into the stomach unimpeded.
Answer: C – If the LOS doesn't open, food builds up in the oesophagus (dysphagia).
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How long does the pharyngeal phase of deglutition last?
A) Less than 1 second
B) 2–3 seconds
C) 8–20 seconds
D) 30–40 seconds
Answer: A – The pharyngeal phase is rapid, lasting about 1 second.
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What characteristic defines the "all-or-none" nature of the swallowing reflex?
A) It must be consciously controlled throughout.
B) It starts voluntarily but once triggered becomes automatic.
C) It can be paused in the pharyngeal phase if needed.
D) It is only present in infants.
Answer: B – Voluntarily initiated, but automatically completed once started.
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Which statement correctly describes the interaction of the mastication CPG?
A) It operates independently without any communication with breathing or swallowing centres.
B) It integrates with respiratory and swallowing CPGs for coordinated control.
C) It only functions during sleep.
D) It directly triggers peristalsis.
Answer: B – The masticatory CPG interacts with respiratory and swallowing centres.
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What is histology?
The study of the microanatomy of tissues and organs, involving structures not visible to the naked eye. It uses stains and dyes and is important for understanding function and diagnosing disease.
180
What are the main functions of epithelium?
Lining and protection of surfaces, secretion, and absorption.
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What supports the epithelial cell layer?
The basement membrane, which itself is supported by the lamina propria.
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How are epithelia classified?
By the number of layers, shape of the top layer of cells, and surface specialisations.
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Describe:
1. Simple cuboidal epithelium.
2. Simple columnar epithelium
3. Stratified squamous epithelium.
1. A single layer of column-shaped cells for secretion and absorption (e.g., small and large intestine).
2. A single layer of column-shaped cells for secretion and absorption (e.g., small and large intestine).
3. Multiple layers of flattened cells, mainly providing protection from abrasion (e.g., skin epidermis).
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How does epithelium protect the body?
By resisting friction, stretching (e.g., bladder), and secreting mucus to protect against toxins and pathogens.
185
What is selective absorption?
Absorption regulated based on molecule size, charge, and structure; facilitated by tight junctions.
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What surface specialisations increase absorption?
Villi and microvilli, by increasing the surface area.
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How do epithelia secrete substances?
Via glands specialised for synthesis, storage, and release (e.g., pancreatic enzymes, sebaceous glands).
188
What are goblet cells?
Mucous-secreting epithelial cells found within the gastrointestinal and respiratory tracts.
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Why are there no blood vessels in epithelium?
To protect vessels from abrasion; nutrients and gases diffuse from vessels in the lamina propria.
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List the four layers of the gastrointestinal tract wall.
Mucosa (epithelium + lamina propria + muscularis mucosae), Submucosa, Muscularis externa, Adventitia/Serosa.
191
What type of epithelium lines the oesophagus?
Stratified squamous epithelium, protecting from abrasion.
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Describe the transition at the gastro-oesophageal junction.
From stratified squamous epithelium (oesophagus) to simple columnar epithelium (stomach).
193
What are gastric pits and glands?
Invaginations where mucous cells, parietal cells, chief cells, and enteroendocrine cells secrete various substances.
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What do parietal cells secrete?
Hydrochloric acid (HCl) and intrinsic factor (GIF).
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What do chief cells secrete?
Pepsinogen and gastric lipase.
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What is Barrett's oesophagus?
Metaplastic change where oesophageal epithelium becomes more like stomach epithelium, often due to chronic gastro-oesophageal reflux disease (GERD).
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What are the key features of the small intestine?
Villi, crypts, simple columnar epithelium, lamina propria with lacteals and blood capillaries.
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What is the function of lacteals?
Absorb dietary fats and transport them via the lymphatic system.
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What is unique about the duodenum?
Presence of Brunner’s glands (neutralise stomach acid) and crypts containing stem cells.
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How does the jejunum differ from the duodenum?
Lacks Brunner’s glands but has prominent villi and folds (plicae circulares).
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What structures are characteristic of the ileum?
Shorter villi and Peyer's patches (aggregated lymphoid tissue).
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What is unique about the large intestine histology?
Lacks villi, has abundant crypts with mucous-secreting and stem cells.
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Describe the liver’s histological organisation.
Hexagonal lobules with a central vein and a portal triad (portal vein, hepatic artery, bile duct) at each corner.
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What are sinusoids in the liver?
Specialised capillaries with fenestrated endothelium, allowing blood exchange with hepatocytes.
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What is hepatic steatosis?
Fatty liver disease, characterised by accumulation of fat within hepatocytes.
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What are the two functional parts of the pancreas?
Exocrine (pancreatic acini secreting digestive enzymes)
Endocrine (Islets of Langerhans secreting hormones like insulin and glucagon).
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What do alpha and beta cells in the pancreas secrete?
Alpha cells secrete glucagon; beta cells secrete insulin.
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Name some key takeaways from GIT histology.
Epithelium protects, secretes, and absorbs.
GIT wall has four basic layers.
Specialised structures (e.g., Brunner’s glands, Peyer's patches) support digestion and immunity.
209
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How is epithelial cell polarity important for absorption in the GIT?
Polarity ensures directional transport of molecules: the apical surface interacts with the lumen contents, while the basolateral surface manages uptake into blood vessels.
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What is the brush border and what is its function?
The brush border is formed by densely packed microvilli on the apical surface of intestinal epithelial cells, maximising the surface area for nutrient absorption.
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What do mucous neck cells secrete?
Mucous neck cells secrete a thinner, acidic mucus different from the surface mucous cells, aiding in protection and enzyme activation.
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What does intrinsic factor (secreted by parietal cells) do?
It is essential for the absorption of vitamin B₁₂ in the ileum.
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What are Paneth cells and where are they located?
Paneth cells are found at the base of crypts in the small intestine and secrete antimicrobial peptides to maintain gut flora.
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What is the difference between serosa and adventitia in the GIT?
Serosa is connective tissue covered by mesothelium (in the abdomen); adventitia is connective tissue only (in areas like the oesophagus).
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Which type of epithelium lines the oesophagus?
A) Simple columnar epithelium
B) Stratified squamous epithelium
C) Pseudostratified columnar epithelium
D) Simple squamous epithelium
Answer: B — Stratified squamous epithelium.
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Which cells in the stomach secrete hydrochloric acid (HCl)?
A) Chief cells
B) Surface mucous cells
C) Parietal cells
D) Goblet cells
Answer: C — Parietal cells.
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The basement membrane supports which of the following?
A) Muscularis externa
B) Lamina propria
C) Epithelial cell layer
D) Adventitia
Answer: C — Epithelial cell layer.
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What is the correct order of the layers of the gastrointestinal tract wall, starting from the lumen?
A) Submucosa → Mucosa → Muscularis externa → Serosa
B) Mucosa → Submucosa → Muscularis externa → Adventitia/Serosa
C) Mucosa → Muscularis externa → Submucosa → Serosa
D) Adventitia → Submucosa → Muscularis externa → Mucosa
Answer: B — Mucosa → Submucosa → Muscularis externa → Adventitia/Serosa.
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Which specialisation increases the surface area of the small intestine for absorption?
A) Plicae circulares
B) Goblet cells
C) Peyer’s patches
D) Crypts of Lieberkühn
A — Plicae circulares (also villi and microvilli help).
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Brunner’s glands are characteristic of which part of the small intestine?
A) Jejunum
B) Ileum
C) Duodenum
D) Large intestine
Answer: C — Duodenum.
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In Barrett’s oesophagus, the normal epithelium of the oesophagus is replaced with: A) Simple squamous epithelium
B) Simple columnar epithelium with goblet cells
C) Stratified cuboidal epithelium
D) Transitional epithelium
Answer: B — Simple columnar epithelium with goblet cells.
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Which structure in the liver allows exchange between blood and hepatocytes?
A) Bile canaliculi
B) Hepatic artery
C) Sinusoids
D) Portal vein
Answer: C — Sinusoids.
223
Which of the following is NOT found in the portal triad of the liver?
A) Branch of the portal vein
B) Branch of the bile duct
C) Branch of the hepatic artery
D) Central vein
Answer: D — Central vein.
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What type of secretion is produced by the Islets of Langerhans?
A) Exocrine digestive enzymes
B) Endocrine hormones like insulin and glucagon
C) Bile salts
D) Mucous
Answer: B — Endocrine hormones like insulin and glucagon.
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Which feature is characteristic of the large intestine but not the small intestine?
A) Presence of crypts without villi
B) Abundant Brunner’s glands
C) Extensive Peyer’s patches
D) Tall villi
Answer: A — Presence of crypts without villi.
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Which cells are responsible for replenishing the epithelial lining of the small intestine?
A) Chief cells
B) Paneth cells
C) Stem cells in crypts
D) Goblet cells
Answer: C — Stem cells in crypts.
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In the stomach, what is the role of chief cells?
A) Secrete intrinsic factor
B) Produce pepsinogen and gastric lipase
C) Secrete hydrochloric acid
D) Secrete mucus
Answer: B — Produce pepsinogen and gastric lipase.
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What type of epithelium lines most of the stomach and intestines?
A) Stratified squamous
B) Simple cuboidal
C) Simple columnar
D) Transitional
Answer: C — Simple columnar.
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Which function is associated with goblet cells?
A) Secretion of digestive enzymes
B) Absorption of nutrients
C) Secretion of mucus
D) Secretion of bile
Answer: C — Secretion of mucus.
