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Unit 3 > GI Tract > Flashcards

GI Tract Flashcards

1
Q

Processes

A
  • Ingestion: to take in food
  • Mastication: chewing (mechanical breakdown of food)
  • Deglutition: swallowing
  • Digestion: chemical breakdown of food
  • Absorption: passage of food from the digestive tract lumen to the blood
  • Peristalsis: the “milking” action of smooth muscle; mainly propels food
  • Segmentation: “mixing” action of smooth muscle, separate muscle segments contract at the same time
  • Defecation: the formation and excretion
    of solid waste
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2
Q

Swallowing Mechanisms

A
  • Buccal phase
  • Pharyngeal phase
  • Esophageal phase
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3
Q

Layers of Digestive Tract Wall

A
  • Mucosa
  • Submucosa
  • Muscularis externa
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4
Q

Mucosa

A 
The absorptive layer, lines the lumen, folded to 600x its length in some areas 
(3 major components):
- Mucosal epithelium
- Lamina propria
- Muscularis mucosae
- Serosa
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5
Q

Mucosal Epithelium

A 
Columnar epithelium (stomach, intestines) or stratified squamous
– Crypts of Leiberkuhn: folds in the mucosa, source of new epithelial cells
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6
Q

Lamina Propria

A

Loose CT of the mucosa, with capillaries that receive absorbed nutrients
– lymphatic tissue: capillaries and lymphatic nodules involved in absorption of fat

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7
Q

Muscularis Mucosae

A

A thin layer of smooth muscle that keeps the folds of the mucosa folded

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8
Q

Submucosa

A

Tissue: dense irregular CT
– Peyer’s Patches: aggregates of lymph nodes, significant protection against intestinal infections
Meissner’s plexus: nerve supply to the muscularis mucosae
Brunner’s (intestinal) glands (duodenum only)

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9
Q

Muscularis Externa

A

Mainly a double layer of smooth muscle, propels and mixes digestive contents
– circular layer: thick inner layer, muscle fibers describe a circle
– longitudinal layer: thin outer layer, muscle fibers run along the length of the GI tract
– Auerbach’s (Myenteric) plexus: nerve supply to the muscularis externa

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10
Q

Serosa

A

Outer wall of the GI tract, visceral peritoneum, loose CT + simple squamous epithelium

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11
Q

Mouth and Pharynx

A
  • Tongue: a muscular soft organ, involved in moistening/mixing food, taste, speech
  • Lingual tonsils: aggregates of lymph nodes located on the posterior/superior aspect
  • Frenulum linguae: an inferior attachment of the tongue to the lower jaw
  • Papillae: microscopic folds in the tongue containing taste buds
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12
Q

Heterodont Dentition

A

Having “varied” teeth

  • Diphyodont: having 2 sets of teeth within 1 life time
  • Dental formulas (I - C - P - M in each quadrant)
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13
Q

Deciduous Teeth

A

2-1-0-2:

2 incisors, 1 canine, 0 premolar, and 2 molars in each quadrant

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14
Q

Permanent Teeth

A

2-1-2-3:

2 incisors, 1 canine, 2 premolars, 3 molars in each quadrant

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15
Q

Salivary Glands

A

Release water, lysozyme, digestive enzymes, mucus
• buccal: in cheeks
• parotid: largest, anterior to the ear (pure serous)
• submandibular (submaxillary) inferior and medial to mandible (contain serous/mucus cells)
• sublingual: inferior to the tongue (mostly mucus)

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16
Q

Esophagus

A

Function to move food to the stomach
• lining epithelium: stratified squamous epithelium
• muscle layer:
– 1st third: skeletal m.
– 2nd third: a mixture of skeletal and smooth m.
– 3rd third: smooth m.

17
Q

Stomach

A

A large, muscular distendible portion of the GI tract
• Epithelial lining = simple columnar epi
• 3 layers of smooth muscle: longitudinal, circular and oblique
• Where peristalsis continues and segmentation begins

18
Q

Rugae

A

Macroscopic folds in the stomach, luminal lining, flatten when the stomach is full. Also found in the gall bladder and urinary bladder

19
Q

Gastric Glands & Pits

A
  • Gastric glands: microscopic folds, secrete gastric juice

- Gastric pits: openings from gastric glands to gastric lumen

20
Q

5 Cell Types of Stomach

A

– chief (zymogenic) cells: secrete protein breaking enzymes
– parietal cells: secrete stomach acid
– mucus cells: secrete mucus

21
Q

Enteroendocrine Cells of Gastric Glands

A

– G-cells: secrete hormones to support stomach activity

– Argentaffin cells: secrete histamine and serotonin to support stomach activity

22
Q

Small Intestine

A 
~ 3 meters long, responsible for most digestion/absorption
3 histologically different regions:
- duodenum
- jejunum
- ileum
23
Q

Folds That Increase Intestinal Surface Area

A

– plicae circularis-macroscopic permanent folds (permanent until death) (increase 2 x)
– villi-fingerlike projections on plicae (increase 10 x)
– microvilli-submicroscopic folds on apical membranes of columnar cells (increase 20-30 x)

24
Q

Duodenum

A

25 cm, responsible for 95% of digestion and absorption
• mucous glands (not present in jejunum)
• ampullae-enlargements allowing for openings from pancreatic and bile ducts
– hepatopancreatic (sphincter of Oddi)
– accessory

25
Q

Jejunum

A

1 m long, histologically similar to duodenum, finishes what was started in the duodenum

26
Q

Ileum

A

2m long, mainly water, mineral, vitamin absorption

27
Q

Liver

A

Responsible for detoxifying nutrients, supplying bile to the duodenum, supplying vitamins, supplying hormones

  • Falciform ligament: suspends liver from diaphragm
  • Ligamentum teres hepatis: extends from falciform ligament to umbilicus (remnant of umbilical vein)
28
Q

Gallbladder

A

Stores bile

29
Q

Pancreas

A
  • acinar cells (exocrine): secrete most digestive enzymes and bicarbonate
  • pancreatic ducts: collect enzymes, bicarb, pass them onto the duodenum
  • pancreatic islets (Islets of Langerhans) (endocrine): secrete hormones (insulin)
30
Q

Endocrine Portion of the Pancreas

A
  • pancreatic islets (Islets of Langerhans):
  • approximately 1 million in the human pancreas
  • 2 major cell types alpha and beta
  • control blood sugar
31
Q

Large Intestine

A

• regions (7): cecum, ascending, transverse, descending, sigmoid, rectum, anus

  • lining epithelium
  • haustra
  • haustral churning
  • taenia coli
  • epiploic appendages
32
Q

Lining Epithelium

A

Mostly simple columnar, stratified squamous in the anal canal

33
Q

Haustra & Haustra Churning

A

Haustra: sacs or pouches seen along the length of the large intestine
Haustra Churning: contraction of the haustra, mixes feces, max absorption of water

34
Q

Taenia Coli

A

3 distinct bands of smooth muscle (longitudinal) running the length of the large intestine

35
Q

Rectum & Anus

A
  • rectum: stores feces until defecation

* anus: contains 2 sphincter muscles controlling passage of feces to the exterior

Unit 3 (6 decks)

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