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x. Histology > L6: Digestive 1 > Flashcards

L6: Digestive 1 Flashcards

1
Q

Digestive system overview of function

A

responsible for processing, digestion, and absorption of food material

also elimination of wastes or indigestible residue

Epithelium lining of digestive tube and associated glands is derived from endoderm

gut lining secretes mucus which functions to aid passage of contents down the digestive tract, protect against corrosive HCL and protect against enzymatic degradation of epithelial lining

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2
Q

what are the 3 general sections of the digestive tract

A

oral cavity (mouth)

digestive tube (esophagus, stomach, small and large intestines)

digestive glands (pancreas and liver)

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3
Q

Tongue and oral cavity (epithelium, submucosa structure)

A

lined by stratified squamous epithelium (nonkeratinizing); except keratinized on gums, dorsal surface of tongue, and hard palate

epithelium (mucosa) underlain by submucosa of dense irregular CT with collagen and elastic fibers

  • contains small mucous and mucoserous glands (in submucosa). These glands secrete mucus and digestive enzymes (salivary amylase –> breaks down carbs)
  • underlying CT is immunologically active (tonsils=collections of lymphoid tissue in submucosa in pharynx region)
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4
Q

Muscles of the tongue

A

composed of skeletal muscle sheathed in a mucous membrane continuous with that of the oral cavit

muscle fibers are both intrinsic (confined to the tongue) and extrinsic (originate outside of tongue)

between muscle fibers are mucous glands (at base of tongue), serous glands (in the body of the tongue), and mixed acinar glands (at tip of tongue)

serous glands of the tongue are called von Ebner’s glands= act to wash taste buds free of stimulus molecules to allow new tasting

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5
Q

Von ebner’s glands

A

act to wash taste buds free of stimulus molecules to allow new tasting

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6
Q

Lingual papillae

A

projections of mucosal surface with submucosal core

anterior 2/3 of the tongue covered with these

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7
Q

filiform papillae

A

located over entire surface, slender and conical

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8
Q

fungiform

A

located singly among rows of filiform, more numerous towarsd tip.

mushroom shaped with secondary papillae of CT

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9
Q

circumvallate

A

only 10-14 in humans
located along central sulcus of tongue

surrounded by circular furrow

taste buds present in lateral walls

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10
Q

foliate papillae

A

leaf-like folds on posterolateral margins

taste buds occur in grooves between folds

rudimentary in humans

well developed in rabits

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11
Q

tongue muscle: dorsoventral intrinsic

A

move tip of tongue

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12
Q

tongue muscle: lateral intrinsic

A

move tongue sideways, cup tongue

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13
Q

tongue muscle: extrinsic

A

protrude tongue

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14
Q

taste buds

A

barrel-shaped neuroepithelium (taste receptor cells, sustentacular cells, basal cells); opens via taste pore

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15
Q

taste receptor cells

A

chemoreceptors, respond to dissolved molecules

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16
Q

salivary glands, general

A

compound exocrine glands, developed from epithelial lining

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17
Q

Parotid salivary gland

A

located below and anterior to ear in humans

ducts open to cheek opposite 2nd upper molar, ducts prominent

serous secretion (enzymes [amylase] and polysaccharides)

compound tubuloalveolar

enclosed by dense irregular CT capsule

secretory unit empties to intercalary duct –> secretory ducts (modify ionic composition) –> excretory ducts –> main duct

divided into lobes and lobules by septa (from capsule)

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18
Q

submandibular salivary gland

A

lies in floor of mouth beneath the body of the mandible (lower jaw)

duct opens below tip of tongue- ducts prominent

mixed secretion (mostly serous)

mucous secretory units often capped with cresent-shaped serous demilunes

compound alveolar or tubuloalveolar, encapsulated.

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19
Q

sublingual salivary gland

A

lies underneath tongue

multiple ducts open near submandibular ducts, fewer ducts within the gland.

mixed secretion (mucous predominates)

compound tubuloalveolar

CT capsule less well-developed

20
Q

4 regions of the digestive tube

A

Divided into 4 regions (organs) by sphincters
(muscular valves)…

  1. Esophagus
  2. Stomach
  3. Small Intestine
  4. Large Intestine (colon)
21
Q

4 layers of the digestive tube

A
  1. mucosa
  2. submucosa
  3. muscularis externa
  4. serosa (adventitia)

Although all regions of the digestive tract show common structural arrangement, each particular region is modified according to its function.

22
Q

Mucosa of the digestive tube

A

3 layers:
epithelial membrane- lubricated by mucus.
lamina propria,
muscularis mucosae,

23
Q

lamina propria (mucosa)

A

underlying loose CT layer (rich in BV and lympathics, lymphatics involved in fat transport)

tends to become lymphoid (with lymph nodules)

24
Q

Muscularis mucosae (mucosa)

A

thin layer of smooth muscle forming boundary

contractions cause folding of mucous membrane

25
Q

Mucosa of the small intestines

A

shows finger-like projections or folds into lumen termed villi- act to greatly increase surface area for absorption/digestion.

invaginations of epithelium form intestinal glands or “crypts” and gastric glands (stomach)

26
Q

submucosa

A

Loose CT between muscularis mucosae and
muscularis externa

• Supplied with blood vessels and lymphatics

• Often contains accumulation of lymphoid
tissue

• Contains nerve plexus of autonomic fibers
and ganglion cells = Meissner’s Plexus -
innervates muscularis mucosae

• Contains mucus secreting glands in
esophagus and duodenum of small intestine

27
Q

meissner’s plexus

A

innervates muscularis mucosae

28
Q

muscularis externa

A

Consists of ≥ 2 layers of smooth muscle, more
substantial than m. mucosae

• Striated muscle replaces smooth in upper
esophagus (associated with swallowing)

• Layers: generally inner circular (constricts
lumen), outer longitudinal (shortens gut, widens
lumen)

• Innermost oblique layer occurs in stomach

• M. externa responsible for peristalsis → moving
food along tract

• Between inner circular and outer longitudinal
layers lies Aeurbach’s Plexus = Autonomic nerve
fibers and ganglion cells - innervates m. externa,
mostly parasympathetic

29
Q

aeurbach’s plexus

A

autonomic nerve fibers and ganglion cells - innervate m externa, mostly parasympathetic

30
Q

serosa/adventitia

A

Outermost layer composed of somewhat
denser areolar CT with elastic fibers

• When lined by mesothelium = serosa,
when outside of body cavity
(retroperitoneal, portions of small intestine)
= adventitia

• Contains many blood vessels, lymphatics,
nerves

31
Q

Describe the esophagus

A

Relatively straight tube extending from oral cavity
to stomach, functions mainly in rapid transport of
food

• Mucosal epithelium is nonkeratinizing str.
squamous in humans; in herbivorous mammals
(swallow rough material) keratinized str.
squamous is usually present

• At upper and lower ends, mucosal glands
(cardiac glands) present in lamina propria
(secrete mucus)

• Submucosal mucous glands present throughout

32
Q

Muscularis externa of the esophagus

A

upper esophagus: composed of skeletal muscle.

middle esophagus: smooth begins replacing skeletal.

lower esophagus: smooth musclein inner circular-outer longitudinal arrangement

33
Q

Esophagus submucosa/mucosa empty vs full

A

empty: folds in these layers extending into lumen
full: distended

response is allowed by prominent elastic fibers in submucosa (similar to remainder of digestive tract)

34
Q

stomach: 3 regions, function.

A

Muscular-walled reservoir capable of
retaining food and digestion/absorption of
food

• Consists of 3 regions histologically:
– Cardiac (anterior)
– Fundic
– Pyloric (posterior)

• Food enters stomach as bolus of semisolid
material, exits as chyme = semifluid pulp-like
mass

Absorption limited to salts, water, glucose, alcohol
and some drugs

• Gastric Juice secreted by stomach contains HCl,
mucus, pepsin (a proteolytic enzyme), lipase (fat
catabolism), rennin (curdles milk)

• Submucosal/Mucosal folds into lumen

35
Q

Mucosal epithelium of the stomach: gastric glands, pits, and cardiac glands.

A

Mucosal epithelium = simple columnar, contains:

– Gastric Glands = simple tubular or branched tubular glands

– Gastric Pits = open to surface, 2 or 3 glands empty into one pit

– Cardiac Glands = only for short initial portion of cardium, mucus-secreting, gastric glands short, gastric pits long; glands coiled and dilated with large lumen

36
Q

Rugae

A

submucosal/mucosal folds into the stomach lumen when empty

37
Q

surface of the stomach is lined with..

A

mucous columnar cells

38
Q

mucous neck cells of the gastric glands

A

found in “neck” region of gland, mucussecreting
(acid mucopolysaccharides, proteoglycans, GAGs); basal cytoplasm basophilic, apical granules stain with PAS (contains carbohydrates)

39
Q

Parietal cells of gastric glands

A

scattered singly or in small groups throughout the length of gland

acidophilic or pale cytoplasms

secrete HCl

40
Q

chief cells in gastric glands

A

found at base of gland

basophilic cytoplasm due to high number of ribosomes, secrete pepsinogen (converted to pepsin by HCl), protein hydrolysis is the result.

Lipase–> lipid digestion

41
Q

Enteroendocrine cells

A 
= found at base of gland; usually with clear
unstained cytoplasm (stain with Ag2+, Cr2+; secrete serotonin, peptide hormones involved in digestion (secretin → stimulates pancreas
secretion, gastrin → stimulates HCl secretion, cholecystokinin → stimulates pancreatic enzyme secretion), endorphins;

release secretion to lamina propria

42
Q

Germinative zone of gastric glands

A

occurs at isthmus/neck junction

continuously replaces dead mucous columnar cells of pit and surface

43
Q

Cardiac glands (pit/gland lengths)

A

long dilated pits

short gastric glands

44
Q

Fundic glands (pit/gland length)

A

short pit

long gland

45
Q

Pyloric glands (pit/gland length)

A

long pits

medium glands

x. Histology (8 decks)

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