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Anatomy 2 > Lect 8 GI tract > Flashcards

Lect 8 GI tract Flashcards

1
Q

Alimentary canal

A

oral cavity ->
pharynx - transport ->
esophagus - transport ->
Stomach - primarily chemical digestion; continued mechanical digestion ->
Small intestine- continued chemical digestion; absorption ->
Large intestine - absorption (h2o + electrolytes)

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2
Q

pharynx

A

provides communication bw nasal + oral cavities and larynx/esophagus
-serves as passage for air and food
-mostly stratified squamous non keratinized epi
-respiratory ares lined with pseduostratified respirator epi
3 regions: naso, oro and laryngopharynx

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3
Q

4 layers of alimentary wall

A

layers modified based on function

mucosa, submucosa, muscularis externa, serosa or adventitia

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4
Q

mucosa

A

lining epithelium - varies
lamina propria - loose CT
muscularis mucosae - smooth muscle

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5
Q

Submucosa

A

Dense irregular CT

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6
Q

Muscularis externa

A

smooth muscle - inner circular/outer longitudinal- all regions except upper 2/3 of esophagus, which is skeletal

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7
Q

serosa/adventitia

A

serosa - mesothelium and underlying CT

adventitia - CT

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8
Q

esophagus mucosa

A

lining epithelium: SSNKE
lamina propria - loose CT w. lymphatic nodules and diffues lymphatic tissue (MALT) scattered throughout; esophogeal cardiac glands
muscularis mucosae: smooth muscle, organizes in the esophagus

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9
Q

esophogeal cardiac glands

A

location: lamina propria of distal esophagus only
function: secrete mucus and protects esophagus from acidic gastric fluids that reflux into esophagus

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10
Q

esophagus submucosa

A

Dense irregular CT, w/ elastic fibers that allows for expansion for food bolus; esophageal glands proper, location of Meissner’s plexus

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11
Q

Esophageal glands proper

A

location: throughout length of the esophageal mucosa
function: mucus product lubricates the wall, offers protection and facilitates transport of food

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12
Q

Esophagus muscalaris externa

A

inner circular/outer longitudinal
skeletal muscle replaced such that swalling begins as controlled voluntary movement but ends in involuntary peristalis
Upper 1/3: skeletal
middle 1/3: mixed
Lower 1/3: smooth
Auerbachs plexus: between inner circular/ outer longitudinal layers

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13
Q

Esophagus adventitia/serosa

A

thoracic cavity: an adventitia binds esophagus to other structure within the thoracic cavity (trachea, aorta)
abdominal cavity: serosa covers the intra-abdominal portion of the esophagus

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14
Q

Gastroesophageal junction

A 
Features: 
abrupt change in the epithelium from Strat Squamous NKE to simple columnar epithelium
Gastroesophageal sphincter (physiologic sphincter) increased tone in the inner circular layer of the muscularis externa
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15
Q

Stomach regions

A

cardia, fundus, body, pylorus
(fundus & body are same histologically)
4 layers of wall
major function: physical and chemical digestion -> process food into chyme

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16
Q

stomach mucosa

A

Lining epithelium - simple columnar

covers the luminal surface, gastric pits, glands

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17
Q

Lining epithelium of stomach mucosa

A

Six cell types. 1. surface mucous cells 2. mucous neck cells 3. stem cells 4. enteroendocrine cells 5. Parietal cells 6. chief cells
(glands are lined by 3-5 cell types)

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18
Q

surface mucous cells

A

Location: luminal surface of stomach and gastric pits

structure: simple columnar cells; apical mucigen granules; basal nucleus
function: release mucin, which w/ water, forms a viscous alkaline mucus high in bicarbonate ion concentraion; buffers and coats the luminal surface and protects the epithelium from the acidic luminal contents

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19
Q

glands of the stomach mucosa

A

Gastric (fundic) - in body and fundus
contains mucous neck, stem, enteroendocrine, parietal and chief cells

Cardiac glands- in cardia
contains mucous neck, stem, enteroendocrine, may have some parietal cells

pyloric glands: in pylorus
contain mucous neck cells, stem cells, enteroendocrine cells

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20
Q

mucous neck cells

A

location: isthmus and neck of cardiac, pyloric and gastric glands (small clusters or individually)
structure: columnar cell; may appear less regular in shape because of compression by adjacent cell; apical mucigen granules, basal nucleus

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21
Q

Function of mucous neck cells

A

contribute to mucous blanket, produce a less alkaline mucus compared with surface mucous cells (although they look the same as mucous cells, their secretions are much different)
protect parietal cells

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22
Q

stem cells of stomach mucosa in glands

A

Location: isthmus and neck of cardiac, pyloric and gastric glands
Structure: columnar cells
Function: stem cell for all epithelial cell types in the stomach

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23
Q

enteroendocrine cells

A

location: primarily at base of cardiac pyloric and gastric glands
Structure: basally located secretory granu

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24
Q

function of enteroendocrine cells

A

basal secretion of various hormones into lamina propria (blood vessels)

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25
Parietal cells of the stomach glands
Location: scattered through out gastric glands (few in cardiac) Structure: large; triangular shape with intracellular canaliculi with microvilli Cytoplasm is eosinophilic due to abundant mitochondria, which are necessary to fuel ion pumps
26
function of parietal cells
produce hydrochloric acid | does not secrete HCl in its final form; H+ and Cl- secreted separately -> combine in the lumen
27
Chief cells
location: base of gastric glands structure: apical granules (zymogen granules) contain proenzyme pepsinogen Basal cytoplasm is basophilic due to presence of rER that synthesize protein for secretion
28
function of chief cells
secrete pepsinogen -once in contact with acidic environment, pepsinogen is converted to pepsin, a digestive enzyme secrete gastric lipase
29
Submucosa of the stomach
dense irregular CT contains neurovascular structures, including Meissner's nerve plexus (supplies local vessels & muscularis mucosae no glands
30
Muscularis externa of the stomach
3 layers: inner oblique, middle circular, outer longitudinal - auerbach's nerve plexus - between muscle layers provides innervation - mixes chyme and moves contents toward duodenum
31
serosa
covers entire stomach
32
pyloric sphincter
location: junction of pyloric stomach and duodenum | formed by a thickening of the middle circular layer of the muscularis externa
33
small intestine
3 regions: duodenum, jejunum, ileum | function: complete digestion, absorb nutrients
34
absorptive features of small intestine
plicae circulares - series of permanent circular folds; mucosa and submucosa villi- evaginations of mucosa - lined with simple columnar epi with a core of lamina propria microvilli - located at the apical aspect of enterocyte/absorptive cells (mucosa)
35
mucosa of the small intestine
lining epithelium - simple columnar epi covers villi and intestinal glands/crypts (of Lieberkuhn six cell types: Enterocytes, goblet cells, enteroendocrine cells, paneth cells, M-cells, stem cells
36
Enterocytes of lining epi of small intestine
location - line luminal surface with villi, migrate from crypt: become fully mature cells as they migrate out of the crypt
37
Function of enterocytes of small intestine
absorbtive role: specialized for transport of nutrients from lumen to the circulatory system Secretory role: glycoprotein enzymes in the glycocaylx are secreted by the enterocytes and have a digestive role - secrete water to maintain chyme consistency
38
Goblet cells
locations: line the luminal surface of villi and crypts, scattered among the enterocytes, increase in number from duodenum toward distal large intestine structure: characteristic 'goblet' shape with apical accumulation of mucigen granules
39
function of goblet cells
mucin is released apically, combines with water to form a mucous product which lubricates and protects the epithelium
40
enteroendocrine cells of the small intestine
location: scattered along villi and crypts structure: basally secretory granules function: release various hormones
41
paneth cells of the small intestine
Location: base of intestinal crypts Structure: apical eosinophilic granules that contain lysozyme Function: lysozyme digests the cell wall of certain microorganisms and bacteria
42
M cells of the small intestine
location: mainly overlie large lymphatic nodules structure: Apical- lack microvilli but have apical microfolds basal: large intracellular pockets; immune cells migrate here through the discontinuous basement membrane function: endocytose and transport antigens to underlying immune cells
43
stem cells of the small intestine
location: base of intestinal crypts function: replace all lining epithelial cell types
44
lamina propria of small intestine
loose CT extends into the core of each intestinal villus and surrounds intestinal crypts/glands contains fenestrated capillaries, lymphatic vessel (lacteal), smooth muscle fibers, diffues lymphatic tissue (MALT) and lymphatic nodules
45
Muscularis mucosae of small intestine
movement of villi
46
submucosa of the small intestine
dense irregular connective tissue includes meissner's nerve plexus as well as blood and lymph vessels regional differences exist in duodenum, jejunum and ileum
47
submucosa of the duodenum
large mucous glands (brunner glands) mucus neutralizes acidic chyme entering the duodenum and thereby 1) offers protection to the epithelium and 2) provides optimal pH for pancreatic enzymes
48
submucosa of the jejunum
no unique histological features | absence of brunners glands and peyers patches
49
submucosa of the ileum
large lymphoid nodules called Peyer patches; these extend into the lamina propria
50
muscularis externa of small intestine
inner circular and outer longitudinal layers | bw 2 muscle layers is auerbach's plexus which is important in peristalsis
51
serosa of small intestine
covers majority of small intestine
52
adventitia of small intestine
located where the duodenum is in contact with posterior abdominal wall
53
Large intestine structure
``` Ileocecal valve appendix colon (ascending, transverse, descending, sigmoid) Rectum anal canal 4 layer wall ```
54
large intestine function
absorption of water and Na+, indigestible material (feces) is formed and propelled by peristalsis through large instestine -> expelled
55
Ileocecal junction
ileocecal valve - thickened extension of the inner circular layer of the muscularis externa at the junciton between the ileum and cecum Transition in the lining epithelium from the small intestinal with villi to the large intestine without villi
56
appendix
extends from the cecum has the typical four layer wall similar to other regions in large intestine except: Greater density of lymphatic nodules the appendix has little or no absorptive function
57
mucosa of the cecum/colon
Lining epithelium: simple columnar, no villi but has numerous straight tubular glands/crypts (of Lieberkuhn) that extend into the lamina propria
58
mucosa of the cecum/colon cell types
``` 5 absorptive cells goblet cells enteroendocrine cells stem cells m cells ```
59
absorptive cells of large intestine
aka colonocytes/enterocytes Location: luminal surface and glands/crypts Structure: columnar, short microvilli Function: absorb water and Na+
60
Goblet cells of large intestine
Location: luminal surface and glands/crypts | Structure/function: goblet shaped; mucus lubricates and protects epithelium
61
Enteroendocrine cells of large intestine
Location: crypts/glands (primary base) | Structure/function: basal secretion - hormone
62
stem cells of large intestine
Location: crypts/glands | Structure/function: replace epithelial cell types
63
m cells of large intestine
location: overlie lymphatic nodules | Structure/function: apical microfolds, basal intracellular pockets; transport antigens to underlying immune cells
64
lamina propria of large intestine
loose CT with abundant immune cells (moreso than small intestine) serves to protect body from the vast bacterial population - numerous capillaries into which water and sodium are absorbed - no lymphatic vessels in LP; organize around muscularis mucosae (which may slow rate of metastasis)
65
Muscularis mucosae of large intestine
enhances the expulsion of mucus from glands
66
large intestine submucosa
dense irregular CT, meissner's nerve plexus as well as blood and lymph vessels lyphoid tissue seen extending from the lamina propria into the submucosa
67
Muscularis externa of large intestine
cecum and colon have the typical inner circular layer, but instead of uniform outer longitudinal layers, they have 3 equally spaced muscular bands, the TENAI COLI between these two muscle layers is Auerbach's nerve plexus , important for peristalsis
68
serosa of large intestine
covers the intraperitoneal portions of the large intestine
69
adventitia of the large intestine
located where the large intestine is in contact with the posterior abdominal wall
70
Rectum
large intestine dilated distal portion of the large intestine similar histology to the colon with variation that include: Crypts/glands are deeper with more abundant goblet cells typical inner circular/outer longitudinal layers of muscularis externa (no teniae coli) adventitia only
71
anal canal
upper 1/3: simple columnar epi middle 1/3: stratified cuboidal epi lower 1/3: stratified squamous non keratinized epi (transitions to stratified squamous keratinized at anus internal anal sphincter is formed by a thickening of inner circular layer of the muscularis externa external anal sphincter is skeletal muscle Adventitia only

Anatomy 2 (8 decks)

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