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2025 SEM 2 HUMAN HISTOLOGY (LEC) > digestive system > Flashcards

digestive system Flashcards

1
Q

digestive tract:
organs associated w digestive tract:

A

digestive tract:
Oral cavity
Esophagus
Stomach
Small intestine
Large intestine

organs associated w digestive tract:
Salivary glands
Pancreas
Liver
Biliary tract & Gallbladder

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2
Q

functions of digestive tract

A

ingestion [take food into mouth] & mastication [chew to break into smaller pieces]
- oral cavity (tongue, teeth, lips, palate, oral pharynx)

motility
- starts when u swallowing aka deglutition

secretion
- secretes enzymes

hormone release
- stimulate digestive progress

chemical digestion
- complex to basic molecules

absorption
- by S.I. and L.I. in a smaller scale

elimination
- main function of L.I.

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3
Q

path of digestive tract

A

esophagus to the anal canal

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4
Q

structural features are common to all parts of the GI tract

A

mucosa
- epithelial lining (depends on the part of the digestive tract)

submucosa
- loose or dense CT

muscularis
- smooth muscle fibers in most GI tract
[involuntary movement like peristalsis]
- striated muscle in lips and tongue
[need precise control for chewing and swallowing]

serosa/ adventitia
- mesothelium

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5
Q

the proximal portion of the alimentary canal

A

oral cavity
★ stratified sq ep

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6
Q

masticatory mucosa vs lining mucosa

A

masticatory mucosa:
- found on gingiva and hard plate
[areas that experience a lot of mechanical stress from chewing]

lining mucosa:
- found in soft palate, cheeks, floor of mouth and oral pharynx
[covers regions of the oral cavity that are less stressed but need to be moist for flexibility]

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7
Q

what type of muscle do lips contain

A

contain well-developed core of striated muscle (moves voluntarily)

has 3 differently covered surfaces:
1. Internal mucous surface
- inner portion
★ non-keratinized

  1. Vermilion zone
    - pinkinsh area of the lips
    transition btwn 2 lining (non-keratinized and keratinized)
  2. Peripheral outer surface
    - outer portion of lips
    - lines w skin epithelium
    ★ keratinized w hair w sweat glands
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8
Q

tongue is formed by?

A

forms as a mass of striated muscle covered by mucosa
- the irregular dorsal surface has hundreds of small protruding papillae of various types

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9
Q

it represent elevations of the mucous membrane that assume various forms and functions

A

lingual papillae:
- Filiform papillae
- Fungiform papillae
- Foliate papillae
- Circumvallate papillae

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10
Q

they are conical, elongated
projections of connective tissue.

A

filiform papillae
- gives the whitish appearance of tongue.

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11
Q

they are bulbous or mushroom-shaped, found interspersed among filiform papillae

A

fungiform papillae

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12
Q

it consist of several parallel ridges on each side of the togue

A

foliate papillae

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13
Q

they are large dome-shaped structures surrounded by a moat-like invagination.

A

circumvallate papillae

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14
Q

where are taste buds present in

A

present on
- fungiform
- foliate
- circumvallate

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15
Q

what are the 3 types of cells in the tongue

A

Neuroepithelial cells
- actual sensory nerve cells [responsible for taste]
- generates AP when exposes to taste chemicals

Supporting cells
- same role as glial cells from PNS
- supports pri nerve cells

Basal cells
- acts as a stem cells
[regenerate and replace the other cells when they get damaged or worn out]

*those 3 cells are also seen in olfactory bulb

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16
Q

true or false:
supporting cells in the tongue are similar to the supporting cells in the olfactory bulb

A

true - (responsible for smell)

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17
Q

what cells does covid 19 target

A

it targets the supporting cells
which leads to loss of taste - ageusia
supporting cells help in maintaining the function of sensory cells, their disruption can cause a temporary loss of taste during the infection.

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18
Q

it is a chemical sensation in which various chemicals elicit stimuli from neuroepithelial cells of taste buds.

A

taste

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19
Q

what are the three types of neuroepithelial cells that react to five basic stimuli

A

Type I neuroepithelial cells:
- react to salty taste.

Type II neuroepithelial cells:
- react to sweet, bitter, and umami tastes.
- mediated by G protein coupled receptors
- receptors:
BITTER - T2R
SWEET - T1R2 & T1R3
UMAMI - T1R1 & T1R3 (activated by monosodium glutamate, MSG/ soy sauce)

Type III neuroepithelial cells:
- react to sour taste

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20
Q

briefly explain the mechanism of each neuroepithelial cells

A

Type II Neuroepithelial Cells:
1. Activation:
-Phospholipase C (PLC) activates, leading to the production of inositol triphosphate (IP3).
- IP3 activates Na+ channels on the cell membrane.

  1. Depolarization:
    - As Na+ ions enter the cell, it becomes depolarized.
  2. Action Potential:
    - If depolarization continues, an action potential (AP) is generated.
    - This leads to the release of neurotransmitters to send the signal to the brain.

Type III Neuroepithelial Cells:
1. Activation:
- Hydrogen ions (H+) from acidic substances (like vinegar, lemon, or calamansi) activate Na+ channels.
*depolarization and action potential is the same

Type I Neuroepithelial Cells:
1. Activation:
- Na+ ions from table salt (NaCl) activate Na+ channels
*depolarization and action potential is the same

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21
Q

it is a major component of the oral cavity and are essential for initiating the digestive process

A

teeth
*digestive process: mastication

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22
Q

what type of several layers of specialized tissue of teeth

A

Enamel:
a hard, thin, translucent layer of acellular mineralized tissue.

Dentin:
lies deep to the enamel and is the most abundant dental tissue.

Cementum:
a thin, pale yellowish layer of bone-like calcified tissue.

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23
Q

it is the hardest substance in the body

A

enamel
- made up of hydroxyapatite crystals
[strongest and most mineralized tissue in the human body, much harder than bone]

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24
Q

what makes up the periodontium

A

cementum
periodontal ligaments
dental alveolus

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25
it is a hard, thin, translucent layer of acellular mineralized tissue
enamel
26
it lies deep to the enamel and is the most abundant dental tissue
dentin
27
it is a thin, pale yellowish layer of bone- like calcified tissue.
cementum
28
what innervates the digestive tract
primarily innervated by the autonomic nervous system (ANS) [innervated - supply with nerve signals to a particular organ or tissue]
29
what are the 2 important nerve plexus that are part of the enteric ervous system (a division of the ANS) which help coordinate the movements and secretions of digestive system
1. Submucosa - Meissner's Plexus - regulates secretions and blood flow [Found in the submucosa, the layer just beneath the mucosa (the innermost lining of the digestive tract)] 2. Muscularis - Auerbach's Plexus - regulates muscle contractions for peristalsis and motility - aka Myenteric Plexus [Located between the inner circular layer and the outer longitudinal layer of the muscularis externa (the muscle layer responsible for peristalsis)]
30
it courses through the neck and mediastinum
esophagus - w overall length of 25cm
31
what glands are present in the wall of the esophagus
Esophageal glands proper: - within the length of esophagus Esophageal cardiac glands: - end of esophagus *both have same role: mucus/ mucin production 1. protect mucosa lining from gastric juices 2. neutralize gastric juices
32
it is an expanded part of the digestive tube that lies beneath the diaphragm.
stomach
33
anatomic and histologic divisions of the stomach
Anatomic divisions: - cardia - fundus - body - pylorus (chyme from stomach empties to the duodenum) Histologic divisions: - Cardiac region - Fundic region - Pyloric region
34
a transition between the esophagus and the stomach
esophagogastric junction (see image)
35
lining of gastric mucosa
★ simple columnar ep - contain a no. of longitudinal folds or ridges called rugae
36
it is the gastric mucosa of the stomach contain a number of longitudinal folds or ridges
rugae - gastric folds/ stomach folds that disappear when full [stretch out and flatten] appear when empty [rugae help the stomach expand as food enters, allowing for increased surface area for the stomach's digestive processes]
37
what does the gastric mucosa consists of
gastric pits - aka foveolae - invaginations of gastric mucosa and secrete enzymes and proteins
38
what does the parietal cell secretes
HCI and intrinsic factor
39
briefly explain the secretion of HCI in parietal cell
CO2 from the blood diffuses into the parietal cells. The CO2 combines with water (H2O) to form carbonic acid (H2CO3). H2CO3 dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-). The H+ ions are transported into the stomach lumen (the space inside the stomach) via the proton pump, while Cl- ions are exchanged from the blood into the stomach lumen. H+ and Cl- combine in the stomach lumen to form HCl, the gastric acid. [Acidifies the stomach: Helps break down food and activates digestive enzymes like pepsin. Kills harmful microbes: Protects against infections by maintaining a low pH environment.]
40
briefly explain the intrinsic factor and the vitamin B12 absorption
Its main function is to bind with Vitamin B12, allowing for the absorption of Vitamin B12 in the ileum (part of the small intestine) Vitamin B12 Deficiency: - If intrinsic factor is destroyed through an autoimmune disorder, the body cannot properly absorb V.B12, leading to V.B12 deficiency. - Symptoms: The deficiency can cause pernicious anemia, characterized by: → Macrocytic hypochromic anemia: Larger-than-normal red blood cells (greater than 9 µm in diameter) with low hemoglobin content. → This results in poor oxygen transport and fatigue. Diphyllobothrium latum (Fish Tapeworm): - parasite can compete with Vitamin B12 for binding to intrinsic factor, leading to Vitamin B12 deficiency as well.
41
what parasite competed with Vitamin B12 for binding intrinsic factors
Diphyllobothrium latum (fish tapeworm) - lead to Vitamin B12 deficiency
42
what medications is used to inhibit the proton pump
omeprazole - PPIs block the H+/K+ ATPase proton pump in parietal cells, reducing the secretion of H+ and lowering stomach acidity.
43
it is specialized cells present in the mucosa of the digestive tract
enteroendocrine cells - account for <1% of all epithelial cells in the GI tract.
44
what are the hormones that are secreted by enteroendocrine cells (site of synthesis)
1. gastrin - stimulates gastric acid secretion in stomach (G cells in stomach) 2. ghrelin - satiety [ stimulates hunger (often called the "hunger hormone") and promotes satiety after eating] (Gr cells in stomach) 3. CCK, cholecystokinin (I cells in duodenum and jejunum) 4. secretin (S cells in duodenum) 5. GIP, gastric inhibitory peptide (K cells in duodenum and jejunum) 6. motilin (Mo cells in duodenum and jejunum)
45
briefly explain cardiac glands and pyloric glands in the gastric mucosa of stomach
cardiac glands: composed of mucus-secreting cells in cardiac region pyloric glands: similar to surface mucous cells help protect the pyloric mucosa in pyloric region
46
it is the principal site for the digestion of food and absorption of the products of digestion.
small intestine
47
the absorptive surface area of the small intestine is amplified by
tissue and cell specializations of the submucosa and mucosa
48
where is the majority digestive process in the small intestine
duodenum chyme + pancreatic enzymes + bile = degrade proteins and emulsify lipids - proteases [Break down proteins into amino acids and small peptides.] - saccharides [Pancreatic amylase and brush border enzymes break down carbohydrates into monosaccharides (glucose, fructose, etc.)]
49
what are the histological features of small intestine
1. Plicae Circulares (Valves of Kerckring) - permanent transverse folds that contain a core of submucosa. 2. Villi - unique, finger/leaf-like projections of the mucosa. 3. Microvilli - of the enterocytes provide major amplification of the luminal surface.
50
intestinal gland is aka
Crypts of Lieberkuhn
51
intestinal villi is lined by
★ simple columnar ep - absorb nutrients - enterocytes transports nutrients from lumen of the intestines into underlying structures
52
what is the lymphatic vessels called inside each villus
lacteal [secifically absorb lipid-soluble nutrients (fats), while blood vessels absorb other nutrients]
53
what are the 5 types of cells found in the intestinal mucosa
enterocytes - absorptive cells - absorption of nutrients goblet cells - secretes mucus paneth cells - maintain normal gut microbiota by secreting lysozyme - lysozyme (an enzyme that targets and breaks down bacterial cell walls, especially Gram-positive bacteria) enteroendocrine cells - secretes: CCK, cholecystokinin secretin gastric inhibitory peptide motilin M cells - located in epithelium overelying lymphatic vessels (like the Peyer's patches in the ileum)
54
it is has a big amt. of nodules in which is covered by M cells (has no microvili)
peyer's patches
55
lining of the submucosa of the SI
dense CT
56
what glands is found inn the duodenum
Brunner glands - secretes mucus/ mucin
57
the muscularis externa of S.I consists of
- inner layer of circularly arranged smooth muscle cells [muscles contract to narrow the intestine.] - outer layer of longitudinally arranged smooth muscle cells [muscles contract to shorten the intestine.] *tgt, these muscle layers work to create peristalsis
58
large intestine comprise of
cecum vermiform appendix colon rectum anal canal
59
what are the distinctive features at the gross level of L.I.
Teniae coli: - represent three narrows, thickened, equally spaced bands. - dorsal portion of the large intestine Haustra coli: - are visible sacculations btwn the teniae coli. - sausages like appearance Omental appendices: - are small, fatty projections of the serosa - fatty tissue that damages large intestine *these are found in the muscularis externa of large intestine
60
function of large intestine
reabsorption of water and electrolytes
61
true or false: mucosa of the large intestine consists of the same cell types as the small intestine
false - consists of the same cell types as the small intestine, except Paneth cells.
62
a cell in the large intestine have a similar appearance to the absorptive cells of the small intestine.
columnar absorptive cells - absorb water and electrocytes from undigested food
63
these cell is found throughout the mucosa of the large intestine
goblet cells - secrete mucus, which lubricates the intestines and helps in the smooth passage of waste.
64
true or false: Crypts of Lieberkuhn is present in small intestine and large intestine
true
65
it is the dilated distal portion of the alimentary canal.
rectum
66
how is the large intestine distinguished
its upper part is distinguished from the rest of the large intestine by the presence of transverse rectal folds
67
it is the most distal portion of the GI tract
anal canal
68
briefly explain the anal canal zone and its lining
colorectal zone: ★ simple columnar anal transitional zone: ★ simple columnar ★ non-keratinized stratified sq squamous zone: ★ non-keratinized stratified sq

2025 SEM 2 HUMAN HISTOLOGY (LEC) (11 decks)

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