1
Q
digestive system is composed of?
A
- digestive tract
- associated glands
2
Q
Parts of the digestive tract
A
- oral cavity
- esophagus
- stomach
- small
- large intestines
- anus
3
Q
Parts of associated glands
A
- salivary glands
- liver
- pancreas
4
Q
Digestive system is also called?
A
gastrointestinal (GI) tract or alimentary canal
5
Q
its function is to obtain molecules from the ingested food that are necessary for the maintenance, growth, and energy needs of the body
A
Digestive system
6
Q
During digestion proteins, complex carbohydrates, nucleic acids, and fats are broken down into their small molecule subunits that are easily absorbed through the?
A
small intestine lining
7
Q
Most water and electrolytes are absorbed in the?
A
large intestine
8
Q
The inner layer of the entire digestive tract forms an important protective barrier between the content of the ___________ and _________ of the body’s connective tissue and vasculature
A
tract’s lumen and the internal milieu
9
Q
Structures within the digestive tract allow the following:
A
- Ingestion 5. Hormone release
- Mastication 6. Chemical digestion
- Motility 7. Absorption
- Secretion 8. Elimination
10
Q
introduction of food and liquid into the oral cavity
A
ingestion
11
Q
chewing, which divides solid food into digestible pieces
A
mastication
12
Q
muscular movements of materials through the tract
A
motility
13
Q
lubricating and protective mucus, digestive enzymes, acidic and alkaline fluids, and bile
A
secretion
14
Q
for local control of motility and secretion
A
hormone release
15
Q
or enzymatic degradation of large macromolecules in food to smaller molecules and their sub units
A
chemical digestion
16
Q
of the small molecules and water into the blood and lymph
A
abosorption
17
Q
indigestible, unabsorbed components of food
A
elimination
18
Q
a hollow tube with a lumen of vari-able diameter and a wall made up of four main layers: the mucosa, submucosa, muscularis, and serosa.
A
Gastrointestinal tract
19
Q
The innermost layer, also called the mucous
membrane.
A
Mucosa
20
Q
Components of mucosa
A
- Epithelial Lining
- Lamina Propria
21
Q
The protective barrier
A
Epithelial lining
22
Q
(Middle layer): Underlying loose connective tissue. Rich in blood vessels, lymphatics, lymphocytes (for immune defense), and small glands.
A
Lamina propria
23
Q
(bottom layer of the mucosa)
• A thin layer of smooth muscle.
• Separates mucosa from submucosa.
• Allows for local movements of the mucos
A
Muscularis Mucosae
24
Q
A layer of denser connective tissue.
• Sits right underneath the innermost layer (the mucosa)
• Contains larger blood and lymph vessels.
• May contain glands and significant lymphoid tissue.
A
Submucosa
25
A network of autonomic nerves in the submucosa
Submucosal (Meissner) Plexus
26
Responsible for mixing and propelling luminal contents.
Thick Muscularis (Muscularis Externa)
27
Composed of smooth muscle cells organized into two main sublayers:
1. Internal Sublayer
2. External Sublayer
28
Generally circular fiber orientation (closer to the lumen).
Internal sublayer
29
Generally longitudinal fiber orientation
External Sublayer
30
• Located between the two muscle sublayers.
• Aggregated into small ganglia.
• Coordinates the muscle contractions.
• Part of the Enteric Nervous System (along with the Submucosal Plexus)
Myenteric (Auerbach) Nerve Plexus
31
(Within the abdominal cavity):
• Outermost layer.
• Thin sheet of loose connective tissue covered by a simple squamous epithelium (mesothelium).
• Continuous with the mesentery and the peritoneum (lining the abdominal cavity)
Serosa
32
(In regions like the esophagus)
• A thick layer of connective tissue lacking a serosa.
• Binds the digestive tract directly to surrounding structures
Adventitia
33
1st (Innermost)
Absorption & Protection (The barrier that touches food)
Mucosa
34
2nd layer
Support & Supply ( The service layer for blood vessels and nerves
Submucosa
35
3rd layer
Motility (The muscle layers that push food along)
Muscularis externa
36
4th (Outermost)
Protection (The outer wrapper and anchor)
Serosa/Adventitia
37
lining that consists of stratified squamous epithelium, which may be keratinized, partially keratinized, or nonkeratinized depending on the exact location.
Oral cavity
38
it is where keratinized cell layers resist most damage from abrasion.
Masticary mucosa
39
overlies a thick submucosa containing diffuse lymphoid tissue and many minor salivary glands, which secrete continuously to keep the mucosal surface wet.
Lining mucosa
40
known as the posterior region of the oral cavity leading to the esophagus
oral pharynx
41
makes the structures highly mobile for ingestion, speech, and other forms of communication
Lips and labia
42
forms as a mass of striated muscle covered by mucosa, which can manipulate ingested material during mastication and swallowing
tongue
43
occur in two bilaterally symmetric arches in the maxillary and mandibular bones.
Permanent teeth
44
Each quadrant of permanent teeth has eight
teeth:
two incisors, one canine, two premolars, and three permanent molars
45
hardest, outermost layer of the tooth's crown, protecting the dentin.
Enamel
46
gums, which are the soft tissues surrounding the teeth and covering the jawbone.
Gingiva
47
yellowish, calcified tissue underlying the enamel and cementum, making up the bulk of the tooth
Dentin
48
central chamber within the crown that contains the dental pulp (nerves and blood vessels).
Pulp cavity
49
passageway extending from the pulp cavity down through the root of the tooth
Root canal
50
bonelike tissue covering the tooth root, providing an attachment surface for the periodontal ligaments
Cementum
51
fibrous connective tissues that anchor the cementum of the tooth root to the alveolar bone.
Periodontal ligaments
52
sockets or depressions within the jawbone where the roots of the teeth are held.
Dental alveoli
53
visible part of the tooth projecting above the gingiva.
Crown
54
narrow junction where the crown meets the root, near the gum line.
Neck
55
part of the tooth embedded within the dental alveoli, below the gum line
Root
56
is a calcified tissue harder than bone, consisting of 70% hydroxyapatite.
Dentin
57
its is where organic matrix contains type I collagen and proteoglycans secreted from the apical ends and where tall cells derived from the cranial neural crest, which form a lining of the pulp cavity
Odontoblasts
58
the hardest component of the human body
Enamel
59
Enamel is composed of?
- 96% calcium hydroxyapatite
- 2%-3% organic material
- few proteins
- no collagen.
60
Enamel is consists of uniform, interlocking columns called _________ , each about 5 um in diameter and surrounded by a thinner layer of other enamel.
enamel rods (or prisms)
61
Each rod extends through the entire thickness of the enamel layer, which averages?
2 mm
62
comprises the structures responsible for maintaining the teeth in the maxillary and mandibular bones, and includes the cementum, the periodontal ligament, and the alveolar bone with the associated gingiva.
Periodontium
63
covers the dentin of the root and resembles bone, but is avascular.
Cementum
64
represents connective tissue with short bundles of collagen fibers, binding the cementum and the alveolar bone
Periodontal ligaments
65
A muscular tube about 25 cm long in adults
Esophagus
66
Esophagus connects the _______ to the ________
pharynx to the stomach
67
transports swallowed food and liquids by peristalsis
Esophagus
68
Layers of the Esophagus:
The four layers of the GI tract are clearly seen in
the esophagus:
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Adventitia/Serosa
69
lined with nonkeratinized stratified squamous epithelium for protection against friction
Mucosa
70
contains esophageal glands that secrete mucus to lubricate and protect
Submucosa
71
composed of muscle layers that help move food downward the lining
Muscularis externa
72
outermost layer providing structural support
Adventitia/Serosa
73
Secrete mucus to keep the inner lining moist and slippery
Esophageal glands (in submucosa)
74
(near the stomach): Secrete additional mucus to protect the lower esophagus from stomach acid
Esophageal cardiac glands
75
• Mucus in the esophagus offers limited protection against stomach acid
Heartburn and GERD
76
Acid reflux occurs when stomach acid flows back into the esophagus
heartburn or reflux esophagitis
77
Incompetent inferior esophageal sphincter may cause chronic heartburn, leading to
GERD (Gastroesophageal Reflux Disease)
78
Untreated GERD can cause erosion of the?
esophageal mucosa
79
Long-term irritation may lead to?
Barrett esophagus
80
A condition where the normal squamous epithelium changes to another type due to acid damage
- Increases risk of esophageal cancer
metaplasia
81
(deglutition) starts with voluntary action and ends with involuntary peristalsis
Swallowing
82
food pushed from mouth to pharynx by the tongue
Voluntary phase
83
wave-like peristaltic contractions move food down the esophagus to the stomac
Involuntary phase
84
The muscularis layer changes along the length of the esophagus:
1. Upper one-third
2. Middle one-third
3. Lower one-third
85
made of skeletal (voluntary) muscle – allows conscious control at the start of swallowing
Upper one-third
86
contains both skeletal and smooth muscle fibers – transition zone for coordinated movement
Middle one-third
87
composed entirely of smooth (involuntary) muscle – controlled automatically during peristalsis
Lower one-third
88
Outer Covering of the Esophagus
• Most of the esophagus is surrounded by ______
⚬ A loose connective tissue layer that blends with nearby structures
adventitia
89
Distal 1–2 cm (in the peritoneal cavity): covered by _______, a thin smooth membrane
⚬ Helps reduce friction as the esophagus contacts other abdominal
organs
serosa
90
greatly dilated part of the digestive tract.
Stomach
91
• It continues **carbohydrate digestion** started by salivary amylase.
Stomach
92
stomach adds acidic fluid and mixes food into a viscous mass called?
chyme
93
Stomach begins triglyceride digestion using?
lipase
94
Stomach starts protein digestion with the enzyme?
pepsin
95
The stomach has four major regions:
1. cardia
2. fundus
3. body
4. pylorus
96
a narrow zone (1.5–3 cm) between the
esophagus and stomach.
cardia
97
is a funnel-shaped region that opens into the small intestine.
pylorus
98
Both the _______ and ______ mainly produce mucus and are histologically similar.
cardia and pylorus
99
identical in structure and contain gastric glands that release acidic gastric juice.
fundus and body
100
The mucosa and submucosa have large folds called _____, which flatten when the stomach fills
rugae
101
In the mucosa, this connect to long, branched, tubular glands that extendthrough the entire lamina propria.
Gastric pits
102
Stem cells for the epithelium of the glands, pits, and stomach lumen are located in the?
isthmus between the pit and gland.
103
These ______ stem cells divide asymmetrically to produce progenitor cells for all epithelial cell types.
pluripotent
104
Some ______ cells migrate upward to replace surface mucous cells.
progenitor cells
105
Surface mucous cells have a turnover time of?
4-7 days
106
around the gastric pits and glands is well vascularized (has many blood vessels).
lamina propria
107
It contains smooth muscle fibers, lymphoid cells, capillaries, and lymphatics.
Mucosa
108
a layer of smooth muscle, separates the mucosa from the submucosa
muscularis mucosae
109
In the _____ and ______the gastric glands occupy most of the mucosa, branching from each gastric pit and containing specialized secretory cells that produce substances essential for the stomach’s functions
fundus and body
110
Four Major Types of Glands in stomach
1. Mucous neck cells
2. Parietal (oxyntic) cells
3. Chief (zymogenic) cells
4. enteroendocrine cells
111
are mainly found in clusters, but can also appear singly in the necks of gastric glands.
Mucous neck cells
112
They often appear distorted by nearby cells and have round nuclei with apical secretory granules.
• Their mucus secretion is less alkaline than that of surface epithelial mucous cells.
Mucous neck cells
113
• They include many progenitor and immature surface mucous cells.
• These cells are less columnar than the surface mucous cells lining the gastric pits.
Mucous neck cells
114
Parietal (oxyntic) cells produce?
hydrochloric acid (HCl) and intrinsic factor
115
They are located among mucous neck cells and in the deeper parts of the gastric glands.
• These cells are large, rounded or pyramidal, with one or two central round nuclei.
Parietal (oxyntic) cells
116
Parietal cells’ cytoplasm is intensely ______ due to numerous mitochondria.
eosinophilic
117
Active parietal cells have an _______ formed by deep invaginations of the apical membrane lined with many microvilli
intracellular canaliculus
118
Carbonic anhydrase converts water and CO₂ into?
HCO₃⁻ (bicarbonate) and H⁺ (hydrogen ions).
119
HCO₃⁻ exits the cell at the?
basal side
120
while H⁺ is pumped out apically along with Cl⁻ ions, forming _____ in the lumen.
HCl
121
The gastric secretion is highly acidic, but the mucosa stays near neutral pH due to ____ release into the lamina propria.
bicarbonate
122
The many mitochondria provide energy for the ion pumps that drive?
acid secretion
123
also secrete intrinsic factor, which is needed for vitamin B₁₂ absorption in the small intestine,
Parietal cells
124
activity of parietal cells is stimulated by?
1. parasympathetic signals
2. histamine
3. gastrin released from
enteroendocrine cells
125
are located mainly in the lower parts of the
gastric glands.
Chief (zymogenic) cells
126
They have abundant rough endoplasmic reticulum (RER) and many secretory granules, showing active protein secretion
Chief (zymogenic) cells
127
The granules contain _______, which become active pepsins in the stomach’s acidic environment.
pepsinogens
128
Pepsins begin the digestion of proteins and work best at a pH of?
1.8–3.5.
129
Chief cells also produce ______, an enzyme that digests fats
gastric lipase
130
When stimulated, ________ release hormones that act (paracrine) or through the blood (endocrine).
enteroendocrine cells
131
DNES cells are classified as?
closed or open types.
132
have their tops covered by nearby epithelial cells.
Closed-type cells
133
touch the lumen and have chemoreceptors that sense what’s inside the digestive tract.
Open-type cells
134
The hormones that Enteroendocrine cells release help control?
1. peristalsis
2. regulate secretions
3. balance water and electrolytes
4. signal fullness after eating
135
The cardia and pylorus regions of the stomach contain ________ with long pits.
tubular glands
136
These glands branch into coiled secretory portions called.?
cardiac glands and pyloric glands
137
They lack parietal and chief cells.
• Their main function is to secrete large amounts of mucus
cardiac glands and pyloric glands.
138
• Main site for completion of digestion and nutrient absorption.
• Approximately 5 meters long.
Small intestine
139
Small intestine is composed of three segments:
galing!!!
140
receives chyme, bile, and pancreatic secretions
Duodenum
141
main site of nutrient absorption
Jejunum
142
contains Peyer’s patches for immune defense
Ileum
143
• **Completes digestion** of carbohydrates, proteins, and fats.
• **Absorbs nutrients** (monosaccharides, amino acids, fatty acids, vitamins, water).
Small intestine
144
• Moves chyme by peristalsis.
• Plays a key role in immune defense (via
Peyer’s patches and M cells)
Small intestine
145
Benign tumors from smooth muscle cells.
• Most common type of tumor in the stomach and small intestine.
• May grow large but are non-cancerous.
• Found in up to 50% of people over 50 years old.
• Arise in the muscularis layer
Leiomyomas
146
Mucosa and submucosa form permanent circular folds called?
plicae circulares
147
Plicae circulares is Covered with ______ (0.5–1.5 mm long), which project into the lumen.
villi
148
Villi are covered by simple columnar epithelium with?
enterocytes and goblet cells.
149
Each villus contains:
⚬ Lamina propria
⚬ Capillaries
⚬ Lacteal
⚬ Smooth muscle fibers
150
with fibroblasts, immune cells
Lamina propria
151
absorbs nutrients
capillaries
152
absorbs lipids
lacteal
153
aiding movement and absorption
Smooth muscle fibers
154
• Autoimmune reaction to gluten (in wheat, barley, rye).
• Causes inflammation and destruction of villi.
Celiac Disease
155
Leads to malabsorption and nutrient deficiencies.
• Symptoms: Diarrhea, fatigue, weight loss, anemia.
• Treatment: Gluten-free diet
Celiac Disease
156
In small intestine
- found between villi, opening into the lumen.
Intestinal Glands (Crypts of Lieberkühn)
157
Lined by pluripotent stem cells → replace epithelial cells every 4–6 days.
Intestinal Glands (Crypts of Lieberkühn)
158
Intestinal Glands (Crypts of Lieberkühn) Contain several specialized cell types:
1. Enterocytes (absorptive)
2. Goblet cells (mucus)
3. Paneth cells (defense)
4. Enteroendocrine cells (hormones)
5. M cells (immune sampling)
159
• Tall columnar cells with basal nuclei.
• Have a brush border made of ~3000 microvilli per cell.
Enterocytes (Absorptive Cells)
160
Microvilli of emterocyte is covered by ______, containing enzymes (disaccharidases, peptidases).
glycocalyx
161
Vastly increase surface area in enterocytes:
⚬ Plicae ×3
⚬ Villi ×10
⚬ Microvilli ×20 → total area ≈ 200 m²
162
Enterocytes Absorb nutrients by?
active transport and diffusion
163
_______ → monosaccharides → capillaries.
carbohydrates
164
_______ → amino acids → capillaries.
Proteins
165
Lipids: _______ break fats → glycerol, monoglycerides, fatty acids.
Lipase
166
combined with bile salts
micelles
167
Enter enterocytes → reformed into?
triglycerides
168
absorbed by lacteals
chylomicrons
169
• Scattered among enterocytes.
• Functions:
⚬ Protects epithelium from acid and enzymes.
⚬ Lubricates intestinal contents.
⚬ Number increases toward the ileum.
Goblet Cells
170
Goblet cells Secrete _______ → form mucus when hydrated.
glycoprotein mucins
171
• Found at the base of intestinal crypts.
• Contain large eosinophilic granules.
Paneth cells
172
Paneth cells release antimicrobial substances:
1. Lysozyme
2. phospholipase A₂
3. defensins.
173
Functions:
⚬ Innate immunity (kills bacteria).
⚬ Maintain healthy environment for
stem cells
Paneth cells
174
Found throughout the intestinal epithelium.
Enteroendocrine Cells
175
cells with apical ends detecting nutrients
Open type cells
176
Secrete hormones regulating digestion:
1. Secretin
2. Cholecystokinin
3. Motilin, GIP
177
stimulates bicarbonate from pancreas.
secretin
178
stimulates bile & pancreatic enzymes.
cholecystokinin
179
control motility and insulin release.
Motilin, GIP
180
Coordinate digestion and absorption
Enteroendocrine Cells
181
Loose connective tissue with blood & lymph vessels, smooth muscle, and immune cells.
Lamina propria
182
Contains larger vessels and submucosal (Meissner) plexus.
Submucosa
183
– has Brunner’s glands (alkaline mucus to neutralize acid).
Duodenum
184
2 layers of Muscularis externa:
Inner circular
Outer longitudinal
185
controls peristalsis
Myenteric (Auerbach) plexus
186
are vital parts of the digestive system responsible for nutrient absorption and waste formation.
Together, they ensure the body receives nutrients and maintains fluid balance
small and large intestines
187
completes digestion and absorbs nutrients.
small intestine
188
absorbs water and electrolytes, forms feces.
large intestine
189
Structure of the Large Intestine
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa
190
Simple columnar epithelium with many goblet cells and intestinal glands.
Mucosa
191
Contains blood vessels and lymphatic tissue (MALT).
Submucosa
192
Has inner circular and outer longitudinal muscle
layers forming teniae coli.
Muscularis externa
193
Outermost layer covered with connective tissue and peritoneum.
Serosa
194
Mucosa of large intestine
⚬ Contains tubular intestinal glands (crypts) lined by:
1. Goblet cells
2. Absorptive cells (colonocytes)
3. Few enteroendocrine cells
195
secrete mucus for lubrication
goblet cells
196
absorb water and electrolytes
absorptive cells
197
regulate secretion and motility
Few enteroendocrine cells
198
Stem cells found at base of glands for renewal
Mucosa
199
rich in lymphoid tissue (MALT) — protects against bacteria
lamina propria
200
⚬ Inner circular layer
⚬ Outer longitudinal layer forms three bands — the teniae coli
Muscularis externa
201
The ________ (bowel) absorbs water and electrolytes and forms feces from
indigestible materials.
large intestine
202
Regions of large intestine
1. Cecum with the ileocecal valve and appendix
2. Colon
3. Rectum
203
ascending, transverse, descending, sigmoid
colon
204
stores feces before evacuation
rectum
205
Shorter than the small intestine but wider (6–7 cm diameter)
large intestine
206
Wall forms large pouches called ?
haustra
207
Secrete mucus to lubricate feces and protect mucosa.
goblet cells
208
Absorb water and electrolytes.
Enterocytes (absorptive cells)
209
Contains lymphoid nodules for immune defense.
Lamina propria
210
Form haustra (pouch-like segments) that help move and compact feces.
Muscular layers
211
Three thick longitudinal muscle bands that help in segmentation and peristalsis
Teniae coli
212
The _______ and _______ are rich in blood vessels for nutrient and water absorption.
submucosa and lamina propria
213
They provide defense against intestinal bacteria.
Lymphatic nodules and MALT
214
are present mainly in the mucosa to drain absorbed fat and fluids.
lacteals
215
Stores feces temporarily before elimination.
rectum
216
Lined with anal columns and sinuses that help passage of feces.
anal canal
217
Smooth muscle, involuntary.
Internal anal sphincter
218
Skeletal muscle, voluntary control.
External anal sphincter
219
Usually develops from adenomatous polyps in mucosal epithelium.
colorectal cancesr
220
Swelling of rectal veins caused by straining or low-fiber diet.
Hemorrhoids
221
Formation of pouches (diverticula) due to pressure on weak spots of the colon wall.
Diverticulosis
222
Early detection through ________ blood test is essential
colonoscopy or fecal occult
223
• Absorbs water and electrolytes.
• Forms and stores feces.
• Contains goblet cells and glands for lubrication.
large intestine
224
• Has teniae coli and haustra aiding movement.
• It ensures proper waste elimination and fluid
balance, completing the digestive process
Large intestine
225
one for goodluck
matsalove sah
Histology
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