NUTR100 Lecture 3: Chapter 3
13 Jun 2018
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Chapter 3: Digestion, Absorption and Metabolism
- Cell is smallest unit of life, organized into tissue(muscle, nerve, epithelial, and
connective), forms organs
- Organ systems: Nervous, respiratory, urinary, reproductive, cardiovascular,
lymphatic/immune, muscular, skeletal, endocrine, integumary, digestive
- Digestion:
o Gastrointestinal tract: mouth, pharynx, esophagus, stomach, small intestine,
anus, (lumen)
o Tranist time: 72 hours
o Structure of Gut wall: mucosa)lines the lumen, direct contact with food, very
short lifespan,), connective tissue(surrounds mucosal layer, provides nerve
signals that control), smooth muscle( no voluntary control, surround connective
tissue, mixes food, propels through digestive tract), connective tissue(provides
support and protection)
o Secretions
▪ Enzymes: protein molecules that speed up chemical reactions
• *** be aware of all enzymes, table 3.2
▪ Mucus: protects intestinal tract, moistens, lubricates
▪ Hormones:
• Gastrin: stimulates secretion of HCl and pepsinogen by gastric
glans in the stomach and increases gastric motility
o Role in Immune system: limits the absorption of toxins and disease causing
organisms
▪ Phagocytes: target invader, engulf and destroy by breaking it up
▪ Lymphocytes: produce and secrete protein molecules called antibodies,
fights off one specific antigen, make pahgocytes easier to target.
• Some bind directly to affected cells and destroy them
o Flow of saliva stimulated by food in mouth, moistens food to easily taste and
swallow. Begins salivary amylase which helps break down carbohydrates into
smaller chains of glucose
▪ Lysozymes: inhibit the growth of bacteria that may increase tooth decay
o Tongue moves bolus of chewed food to the pharynx, , epiglottis closes off lung
o Parastalsis: rhythmic contractions of smooth muscle
o Stomach wall has three layers of smooth muscles
▪ One runs longtidinal, the other diagonally and one surrounding GI tract
▪ Lining of stomach covered with gastric pits, there are gastric glands that
produce gastric juice, also secrete hormones, makes HCl, also make
intrinsic factor
▪ Each vili
o Large intestine doesn’t participate in digestion, can absorb water and som
vitamins and minerals
o Intestinal Microflora: permanent, act on unabsorbed protions of food, producing
nutrients that the bacteria can use
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