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Anatomy and Physiology > digestive > Flashcards

digestive Flashcards

1
Q

Digestive system process

A 
ingestion
digestion (mechanical and chemical)
absorption
secretion (into lumen, paracrine signaling, into blood (hormones))
motility (mixing and propulsion)
excretion
defense mechanisms
regulation - hormones and ANS
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2
Q

Digestive system= 2 groups of organs

A
  1. Alimentary canal (GI tract)
    - mouth to anus
    - digests food and absorbs fragments
    - mouth, pharynx, esophagus, stomach, small intestine, and large intestine
  2. Accessory digestive organs
    - teeth, tongue, gallbladder
    - digestive glands : salivary glands, liver, gallbladder, pancreas
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3
Q

Digestion (2 kinds) and objective

A

Mechanical: chewing, mixing, segmentation

Chemical - enzymes

  • carbs, prots, lipids, nucleic acids
  • dif enzymes are active in dif organs

Objective: breakdown of foodstuffs into smaller pieces that the cell can use

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4
Q

Absorption

A

movement of substances from lumen, across intestinal epithelium, into blood or lymph

can be active or passive

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5
Q

Secretion

A

release of substances from glandular epithelium of digestive tract and accessory organs into the lumen

release of hormones into the blood that affect target cells that regulate digestive functions

release of paracrines for local control

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6
Q

Motility

A

movement as a result of contraction of smooth muscle in walls of digestive organs

  • segmental = mixing
  • propulsion = peristalsis = forms bolus

mechanical digestion

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7
Q

Defense mechanisms

A
  • Important bc it’s open to outside world –> mucus membrane
  • mucus is secreted by epithelium
  • enzymes (lysozymes)
  • acidity of stomach
  • Lymphoid tissue (MALT) = collections of lymphocytes along digestive tract
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8
Q

Excretion

A

removal of wastes, unabsorbed and undigested products via defecation in form of feces

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9
Q

GI Regulation: mechanoreceptors and chemoreceptors

A

-Respond to stretch, changes in osmolarity and pH, and presence of substrate and end product of digestion

  • initial reflexes that either
    1. activate/inhibit digestive glands or
    2. stimulate smooth muscle to mix and move lumen contents
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10
Q

GI regulation: intrinsic and extrinsic controls

A

Short refleces = enteric nerve plexuses (gut brain) respond to stimuli in GI tract

Long relexes = respond to stimuli inside or outside GI tract –> involve CNS centers and autonomic nerves

Hormones from cells in stomach and small intestine stimulate target cells in same or dif organs to secrete or contract

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11
Q

Peritoneum and peritoneal cavity

A

Peritoneum = serous membrane of abdominal cavity

  • visceral peritoneum on external surface of most digestive organs
  • parietal peritoneum lines body wall

Peritoneal cavity

  • bt two peritoneums
  • fluid lubricates mobile organs

Mesentery = double layer of peritoneum

  • routes for blood vessels, lymphatics, and nerves
  • holds organs in place and stores fat

retroperitoneal organs are posterior to peritoneum

Intraperitoneal organs ARE surrounded by peritoneum

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12
Q

Blood supply: splanchnic circulation

A

Branches of aorta serving digestive organs

  • hepatic/splenic/left gastric arteries
  • inferior/superior mesenteric arteries

Hepatic portal circulation

  • drains nutrient-rich blood from digestive organs
  • delivers it to the liver for processing
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13
Q

Histology of alimentary canal

A

4 layers/tunics

Mucosa
submucosa
muscularis externa
serosa

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14
Q

Mucosa (func and layers)

A

lines the lumen

Functions: dif layers perform 1 or all 3

  • secretes mucus, digestive enzymes, and hormones
  • abdorbs end products of digestion
  • protects against infectious disease

3 sublayers: epithelium, lamina propria, and muscularis mucosae

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15
Q

Mucosa epithelium

A

simple columnar epithelium and mucus secreting cells (most of the tract)
-mucus protects digestive organs from enzymes and eases food passage

may secrete enzymes and hormones (e.g. stomach and small intestine)

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16
Q

Mucosa: lamina propria and muscularis mucosae

A

Loose areolar CT

  • capillaries for nourishment and absorption
  • lymphoid follicles (part of MALT) –> defend against microorganisms

Muscularis mucosae = smooth muscle –> local movements of mucosa

17
Q

submucosa

A

areolar CT

  • blood and lymphatic vessels
  • lymphoid follicles
  • submucosal nerve plexus
18
Q

Muscularis externa

A
  • responsible for segmentation and peristalsis
  • inner circular and outer longitudinal layers
  • circular layer thickens in some areas –> sphincters
  • myenteric nerve plexus b/t two muscle layers
19
Q

Serosa: (tissue and func)

A

Visceral peritoneum

  • areolar CT covered with mesothelium in most organs
  • replaced by fibrous adventitia in esophagus
  • retroperitoneal organs have both an adventitia and serosa

Func

  • secrete fluid - decrease friction
  • part of peritoneum –> binds organs to surrounding structures and body wall (visceral layer, peritoneal cavity, and parietal layer)
  • extensions provide support to abdominal organs, blood vessels, nerves
20
Q

Folds of serosa

A

Lesser omentum = bt stomach and liver
Falciform ligament = attach liver to abdominal wall
greater omentum = extends below stomach
mesentery proper = small intestine and pancreas to posterior wall
mesocolon = large intestine to posterior wall (also transverse and sigmoid mesocolon)

21
Q 
Enteric NS
definition
what it supplies
plexuses
how it's linked to NS
A
  • Intrinsic nerve supply of alimentary canal –> enteric neurons (more than spinal cord)
  • major nerve supply to GI tract wall: control motility and secretions
  • submucosal nerve plexus regulates glands and smooth muscle in mucosa
  • myenteric nerve plexus controls GI tract motility

Linked to CNS via afferent visceral fibers
Long ANS fibers synapse with enteric plexus
-sympathetic impulses inhibit digestive activities
-parasympathetic impulses stimulate digestive activities

22
Q

Mouth

A

oral (buccal) cavity

  • bounded by lips, cheek, palate (hard and soft), and tongue
  • oral orifice is anerior opening
  • lined with stratified squamous epithelium
  • begins posterior to teeth
23
Q

Lips and cheeks

A
  • contain orbicularis oris and buccinator muscles
  • oral vestibule = recess internal to lips (labia) and cheeks, external to teeth and gums
  • oral cavity proper lies within teeth and gums
  • labial frenulum = medun attachment of each lip to gum
24
Q

Palate

A

Hard palate = palatine bones and palatine processes of maxillae
-slightly corrugated to help create friction against tongue

Soft palate = fold fomed mosly of skeletal muscle

  • closes of nasopharynx during swallowing
  • uvula projects downward from its free edge
25
Q

tongue

A

skeletal muscle

Func:
-repositioning and mixing food during chewing
-form bolus
initiate swallowing, speech, and taste

intrinsic muscles change shape of tongue
extrinsic muscles alter tongues position
Lingual frenulum = attachment to floor of mouth

Lingual lipase

  • secreted by serous cells beneath foliate and vallate papillae
  • fat-digesting enzyme functional in stomach –> must be activated by acid in stomach
26
Q

Salivary glands

A

Major salivary glands:

  • produce saliva and lie outside oral cavity
  • parotid, submandibular, and sublingual

Minor salivary glands
-scattered thoughout oral cavity –> augment slightly

27
Q

Functions of saliva

A

cleanse mouth
dissolve food chems for taste
moistens food –> compacts into bolus
begins breakdown of starch with enzymes

28
Q

Submandibular gland and Sublingual gland

A

Submandibular

  • medial to body of mandible
  • duct opens at base of lingual frenulum
  • secretes mixture of enzyme and mucous saliva

Sublingual gland

  • anterior to submandibular gland uner tongue
  • opens via 10-12 ducts into floor of mouth
  • secretes a more mucous rich saliva
29
Q

Parotid gland

A
  • anterior to ear –> external to masseter muscle
  • parotid duct opens into oral vestibule next to second upper molar
  • mumps is inflammation of parotid glands
  • secretes a more watery, enzyme rich saliva
30
Q

Composition of saliva

A

97-99.5% water; slightly acidic

  • electrolytes = Na, K, Cl, PO4, HCO
  • salivary amylase and lingual lipase
  • mucin
  • metabolic wastes: urea and uric acid
  • lysozyme, IgA, defensins, and a cyanide compound protect against microorganisms
31
Q

control of saliva

A

1500 ml/day
-intrinsic glands continuously keep mouth moist

major salivary glands activated by parasympathetic nervous system when:

  • ingested food stimulates chemoreceptors and mechanoreceptors in mouth
  • salivatory nuclei in brain stem send impulses along parasympathetic fibers in cranial nerves VII and IX

Strong sympathetic stimulation inhibits salivation and results in dry mouth (xerostomia)

32
Q

Digestive processes that happen in the mouth

A 
ingestion
mechanical breakdown (chewing)
propulsion (deglutition = swallowing)
digestion (salivary amylase and lingual lipase)
NO ABSORPTION (except for a few drugs)
33
Q

Pharynx

A

food passes from moth to oropharynx to laryngopharynx

  • allows passage of foods, fluids, and air
  • stratified squamous epithelium lining; mucus producing glands
  • skeletal muscle layers: inner longitudinal and outer pharyngeal constrictors
Oropharynx = digestive and respiratory func
Laryngopharynx = digestive and respiratory func
Nasopharynx = just respiratory; no digestion
34
Q

Esophagus

A

Secretes mucus, transports food –> no enzymes and no absorption
Mucosa = protection against wear and tear: stratified squamous epithelium
Submucosa secretes mucous

Muscularis divided in thirds

  • Superior 1/3 = skeletal muscle
  • Middle 1/3 = skeletal and smooth muscle
  • Inferior 1/3 = smooth muscle
  • 2 sphyncters = upper esophageal (regulates movement into esophagus) and lower esophageal (regulates movement into stomach)

Adventitia - no serosa - attaches to surroundings

35
Q

Deglutition

A

involves tongue, soft palate, pharynx, and esophagus

  • requires coordination of 22 muscle groups
  • Buccal phase = voluntary contraction of tongue
  • Pharyngeal-esophageal phase = involuntary (primary vagus erve) –> control center in medulla and lower pons
36
Q

Actual steps of deglutition

A
  1. buccal phase: UES is contracted and tongue presses against hard palate, forcing food bolus into oropharynx
  2. pharyngeal-esophageal phase starts as uvula and larynx rise to prevent food from entering respiratory passageways–> tongue blocks moth and UES relaxes to let food into esophagus
  3. constrictor muscles of pharynx contract, forcing food through esophagus –> UES contracts after food has entered
  4. peristalsis moves food through esophagus to stomach
  5. LES, surrounding cardinal oriface opens and food enters stomach

Anatomy and Physiology (50 decks)

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