Human Bio II Flashcards > Digestive System > Flashcards

Digestive System Flashcards

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1
Q

Learning outcomes

A
  • Describe the functions of the digestive system.
  • Describe the anatomy of the digestive system and identify the gross and microscopic anatomical features.
  • Describe the general arrangement of the layers of the gut
  • Describe the major processes of digestion.
  • Describe the structure of each part of the digestive tract and relate it to function.
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2
Q

Digestive system

A
  • General characteristics of digestive systems
  • Specialisations of the human digestive system
  • Organs
  • Accessory glands
  • Enzymes
  • Motility
  • Regulation
  • Circulation
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2
Q

Gastrovascular cavity

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  • Digestive compartment with a single opening (mouth)
  • Functions in both digestion &
    distribution of nutrients
    > Extracellular digestion of large
    food masses
    > Specialisation of cells lining the lumen of the cavity for forming digestive secretions & absorption
  • Enables an organism to ingest food much larger than any of its cells
    could take in directly
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2
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2
Q

Phylogeny of the digestive system

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Intracellular digestion:
* Protozoa & sponges
* Digestion is entirely intracellular (occurs within the cell)
* Food particle is enclosed within a food vacuole by phagocytosis
* Digestive enzymes added to vacuole (= compartmentalisation)
Limitations to intracellular digestion:
* Only particles small enough to be phagocytised can be ingested
* Every cell must be capable of secreting the necessary enzymes and
* Absorbing the products of digestion into its cytoplasm

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2
Q

Major regions of the alimentary canal

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  • Regionalisation and specialisation
  • Digestion occurs sequentially
  • Regions of the alimentary canal vary
  • Sphincters & valves control flow
  • Accessory organs and glands
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2
Q

Layers of the digestive tract wall

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2
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Digestive Function

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Stages of digestion
Restion: mlective intakerical reakdown of
food
* Absorption: uptake of nutrient molecules into
epithelial cells of digestive tract and then to blood
and lymph
* Compaction: absorption of water and consolidation
of the indigestible residue
* Defecation: elimination of waste

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2
Q
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3
Q

Alimentary canal

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Evolution of complete mouth to anus alimentary systems
: Vales et senties centrol mathg the di estive oves in one direction
* Extracellular digestion: digestion of large food particles
* Increasing regional specialisation: sequencing of processes

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4
Q

Major regions of the alimentary canal

A
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5
Q

Digestive processes

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Mechanical digestion: Physical breakdown of food
* Cutting and grinding: teeth
* Churning and mixing: stomach & SI
Chemical digestion: Enzymes (produced by glands associated with the digestive tract)
* Amylase: Carbohydrates (polysaccharides) → monosaccharides
* Pepsin, proteases & peptidases: Proteins (polypeptides) → amino acids
* Lipase: Fats → monoglycerides and fatty acids
Some nutrients can be absorbed without being digested
* E.g. vitamins, free amino acids, minerals, cholesterol, water

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6
Q

Motility

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7
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Arterial circulation

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7
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Serous Membranes

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7
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Peritoneum

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8
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8
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Neural control of the digestive tract

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8
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Hepatic portal circulation

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9
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10
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ANS control of the digestive system

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11
Q

Herbivore or carnivore?

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12
Q

Salivary Glands

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12
Q

Learning outcomes

A
  • For each organ & gland of the digestive tract:
  • Macroanatomy
    o Microanatomy
    o Relate structure to function
    o Digestive processes
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The Oral (Buccal) Cavity
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glands
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Tongue
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Lips & Cheeks
* Lined with stratified squamous epithelium. Hold & retain food and drink * Essential for suckling by infant mammals
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Saliva and the Salivary Glands
Salivation * Controlled by the brainstem * Stimuli = presence of food and odour, sight, or thought of food * ANS response: * Parasympathetics stimulate salivary glands to produce much thin, enzyme-rich saliva > Sympathetics stimulate salivary glands to produce less saliva but thicker mucus-rich saliva Saliva * Moistens and lubricates food * Contains water & - Salivary amylase: enzyme that begins carbohydrate digestion in the mouth - Lingual lipase: enzyme that begins fat digestion in the mouth and is further activated by stomach acid & continues to digest fat after food is swallowed - Mucus: binds & lubricates food & aids in swallowing - Lysozyme: enzyme that kills bacteria - Antibodies that inhibits bacterial growth - Electrolytes -ase = denoting an enzyme
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Summary: Digestion in the oral cavity
* Mechanical digestion of food * Salivary amylase begins digestion of carbohydrates (starch) (polysaccharides > oligosaccharides + maltose) * Lingual lipase begins digestion of fats poly-= many oligo-= few saccharon = sugar -ose = pertaining to sugar lipose = fat, grease
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Pharynx
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Swallowing (deglutition)
Swaroin oscurs inting peater in medulla oblongata > Buccal phase: under voluntary control * Pharyngoesophageal phase: involuntary
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Swallowing (deglutition) photo
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swallowing photo
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Esophagus
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Esophagus (oesophagus)
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Esophagus
MUCOSA * Nonkeratinised stratified squamous epithelia > For protection from abrasion from food bolus
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Stomach
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Esophagus
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Gastro-esophageal junction
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Stomach
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Gastric mucosa
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Pepsin
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Gastric Motility
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Summary: Digestion in the stomach
* Mechanical digestion of food (churning) * Pepsin partially digests proteins into shorter peptide chains * Gastric lipase & lingual lipase begin fat digestion * However, most digestion and absorption occurs after the food (chyme) leaves the stomach
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Gastroduodenal junction
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Small Intestine
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Accessory glands associated with the small intestine: Liver photo
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Accessory glands associated with the small intestine: Liver
LIVER : Sle aids in fat digestion & absorpkion by emulsifying fats GALLBLADDER * Stores & concentrates bile
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Accessory glands associated with the small intestine: Pancreas
* Secretes pancreatic enzymes into the SI *Pancreatic amylase: digests carbohydrates *Pancreatic lipase: digests fat * Secretes zymogens (digestive enzymes secreted as inactive proteins & converted to active enzymes) *= proteases & peptidases * digest proteins & small peptides * Secretes bicarbonate into the SI * Neutralizes stomach acids * Secretes insulin & glucagon into the blood * Maintains blood sugar levels
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Accessory glands associated with the small intestine: Pancreas photo
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Small intestine
PLICAE CIRCULARES * Circular folds of the mucosa & submucosa : Focur from the do dina ido the middle of the ileum * Cause chyme to flow in spiral path contact with mucosa * Slows passage of chime * Promotes more thorough mixing & nutrient absorption * increase surface area by a factor of 2 to 3 VILLI * Fingerlike projections * Are folds of the epithelia * increase surface area by a factor of 10
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Small intestine
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Intestinal villi
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Villus
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Carbohydrate digestion & absorption in SI
Carbohydrate (starch) → Oligosaccharides → maltose (disaccharide) → glucose Salivary amylase (mouth) hydrolyzes starch into oligosaccharides Salivary amylase stops working in stomach at pH less than 4.5
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Carbohydrate digestion & absorption in SI photo
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Protein digestion & absorption in SI
Pepsin (stomach) digests 10 - 15% of dietary protein into shorter peptides and some free amino acids. Pepsin is inactivated when it enters the duodenum
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Protein digestion & absorption in SI photo
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Other nutrients digested & absorbed in the Sl
* Nucleic acids * Nucleases - pancreas #DNA & RNA → nucleotides * Brush border enzymes nucleotides → phosphate ions, ribose or deoxyribose sugar, and nitrogenous bases * Vitamins Absorbed unchanged By absorbed poorly unless bound to Intrinsic Factor from the stomach * Minerals Absorbed along the entire length of the Si ・ Water * Most water is absorbed in the small intestine by osmosis ÷ (Some water absorbed in the large intestine) unit outline requirement being satisfied: What is the most important substance absorbed by the small intestine?
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Fat digestion & absorption in SI
Lipases-fat-digesting enzymes Lingual lipase is active in stomach Lingual lipase & gastric lipase digest 10 - 15% of lipids before reaching duodenum
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The Large Intestine photo
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Fat digestion & absorption in SI photo
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Large intestine
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Large intestine
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Large intestine
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Large intestine
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Anal canal
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Anorectal junction
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Neural Control of Defecation
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Human Bio II Flashcards
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