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Anat and Phys > Gastrointestinal tract > Flashcards

Gastrointestinal tract Flashcards

1
Q

The digestive system

A
  • take in food
  • break it down into nutrient molecules
  • absorb molecules into the bloodstream
  • rid body of any indigestible remains
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2
Q

Evolution of the digestive system

A
  • intracellular digestion in food vacuoles
  • simples of all digestive compartments
  • intracellular organelles filled with digestive enzymes (protozoa and sponges)
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3
Q

Evolution of single opening digestive systems

A
  • gastrovascular cavities with a single opening
  • functions in extracellular digestion plus distribution of nutrients
  • digestive compartment surrounded by cells
  • specialisation of cells
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4
Q

Evolution of two opening digestive systems

A
  • digestive tubes with two openings (mouth and anus)
  • alimentary canal
  • more specialised
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5
Q

Major regions of the alimnentary canal

A
  • compartmentalisation
  • regionalisation and specialisation
  • digestion occurs sequentially
  • sphinctors control flow
  • accessory organs and glands
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6
Q

The digestive system

A
  • organs of the digestive system fall into two groups
    1. alimentary canal: gastrointestinal tract = tube from mouth to anus
    2. accessory digestiv organs
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7
Q

Gastrointestinal tract

A
  • continuous muscular tube that runs from the mouth to anus
  • digests food: break down into smaller fragments
  • absorbs fragments through lining into blood
  • organs: mouth, pharynx, oesophagus, stomach, small intestine, large instestine, anus
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8
Q

Accessory digestive organs

A
  • teeth
  • tongue
  • salivary glands
  • gall bladder
  • digestive glands
  • liver
  • pancreas
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9
Q

Basic structure of the alimentary canal

A
  • mucosa
  • submucosa
  • muscularis
  • serosa
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10
Q

Functions of the specialised GIT

6 essential activities

A
  1. ingestion - uptake of food
  2. propulsion - including peristalsis
  3. digestion - mechanical and chemical
  4. absorption - uptake of nutrients
  5. compaction - absorption of water
  6. defactation/excretion - elimnation
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11
Q

Ingestion: mouth/oral/buccal cavity

A
  • bounded by lips anteriorly, cheeks laterally, palate superiorly and tongue inferiorly
  • oral orifice: anterior opening
  • ingestion, chewing, speech, respiration, digestion, swallowing
  • lined with stratified squamous epithelium
    Keratinised in areas subject to abrasion: gums and hard palate
  • no keratinised areas on floor, soft palate and insides of cheeks and lips
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12
Q

Lips and cheeks

A
  • lips important for suckling by infant mammals
  • cheeks: composed of buccinators muscles
  • stratified sqaumous epithelium
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13
Q

Main muscles for chewing

A
  • chewing: important for mechanical breakdown of food
  • buccinator muscles: important for chewing, whistling, smiling, suckling
  • masseter muscle: pulls the mandible upward
  • temporalis: pull the jaw dowan and up
  • medial and letal pterygoid - same as temporalis
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14
Q

teeth and dental formulas

A
  • incisors: anterior part of mouth: scraping or biting -> scoop chaped and smaller
  • canines: usually for ripping or tearing meat, long and pointed
  • premolars: posterior to the canines can be flat for grinding or sharp and serrated for tearing meat
  • molars: vary, depending on their use. Often for grinding food, but in meat eating animals may be serrates and have sharp edges for ripping and tearing meat
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15
Q

Teeth can help to identify animals

A
  • dental formulas: count one side of the maxilla and one side of mandible
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16
Q

extrinsic salivary glands

A
  • main extrinsic salivary glands: parotid, submandibular, sublingual
  • connect to oral cavity by ducts
  • secrete up to 1.5L saliva per day
17
Q

Saliva

A

97-99.5% water
proteins: mucin
enzymes: salivary amylase and lingual lipase
antibodies

18
Q

Intrinsic salivary glands

A
  • 3 mains: lingual, labial, buccal
  • over 600 minor glands
  • produce lingual lipas and lysozyme
  • secrete saliva at a fairly constant rate
19
Q

Salivary gland histology

A
  • salivary glands composed of two types of secretory cells
  • serous cells: produce watery secretion, enzymes, ions and mucin
  • mucous cells: produce
  • parotid and submandicular glands contains mostly serous cells, but sublinual glands consist molstly of mucous cells
20
Q

the tongue

A
  • gripping, repositioning and mixing food during chewing
  • composed of interlacing bundles of skeletal muscle
  • the tongue is covered with papillae, some papillae contain taste receptors
  • papillae make the tongue surface rough to help move food
21
Q

Histology of the tongue

A
  • the human tongue has 4 different types of papillae foliate, filiform, fungiform and circumvallate
22
Q

Propulsion: pharynx

A
  • food passes from mouth into oropharynx and then into laryngopharynx = larynx
  • allos passage of food, fluid and air
  • stratifies squamous epithelium lining with mucus- producing glands
  • external muscle layers consist of 2 skeletal muscle layers
23
Q

Swallowing

A
  • chewed food mixed with saliva = bolus
  • bolus pushed to the back of the tongue
  • tongue pushed against palate and food is propelled to the pharynx
  • soft palate blocks nasal cavity
  • food propelled down oesophagus
  • swallowing reflex takes over
  • epiglottis closes over larynx and trachea
  • food propelled down oesophagus
24
Q

Oesophagus

A
  • flat muscular tube that runs from laryngopharynx to stomach
  • oesophagus has all gour alimentary layers
  • oesophageal mucosa contains strstifed squamous epithelium
  • changes to simple columnar at stomach
  • oesphageal glands in submucosa secrete squamous epithelium
  • changes to simple columnar at stomach
  • oesophageal glands in submucosa secrete mucus to aid in bolus movement
  • muscularis externa: skeletal muscle superiorly, mixxed in middle, smooth muscle inferiorly
25
Q

Peristalsis

A

caused by coordinated contraction of the inner circular smooth muscle and outer longitudinal smooth muscle of the oesophagus

26
Q

Segmentation

A

Nonadjacent segments of the alimentary canal organs contract and relax
- alternate constriction of rings of smooth muscle

27
Q

Sphincters of oesohagus

A

Upper oesophageal sphincter

Lower oesophageal sphincter = cardiac sphincter

Anat and Phys (19 decks)

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