Digestion: Chewing

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Digestion Chewing Dissolving

• 11 - 23

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Differences between primary and permanent teeth
(11)

• Primary and permanent dentitions have formed by
  age 21
• Primary 20 deciduous teeth that erupt at
  intervals between 6 and 24 months
• Permanent enlarge and develop causing the root
  of deciduous teeth to be reabsorbed and fall out
  between the ages of 6 and 12 years

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All but the third molars have erupted by the end
of adolescenceThere are usually 32 permanent
teeth
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Functional structural differences between the
three different types of adult teeth (12)

• Incisors chisel-shaped teeth adapted for
  cutting or nipping
• Canines conical or fanglike teeth that tear or
  pierce
• Premolars (bicuspids) and molars have broad
  crowns with rounded tips and are best suited for
  grinding or crushing

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Parts function of the adult tooth (13)

• Two main regions crown and the root
• Crown exposed part of the tooth above the
  gingiva (gum)

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(crown, enamel, root, neck, cementum, dentin,
pulp cavity, pulp, root canal)

• The portion of the tooth embedded in the jawbone

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crown, enamel, root, neck, cementum, dentin, pulp
cavity, pulp, root canal

• Constriction where crown root come together

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crown, enamel, root, neck, cementum, dentin, pulp
cavity, pulp, root canal

• Calcified connective tissue it covers the root
  and attaches it to the peridontal ligament

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crown, enamel, root, neck, cementum, dentin, pulp
cavity, pulp, root canal

• Bonelike material deep to the enamel cap that
  forms the bulk of the tooth

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crown, enamel, root, neck, cementum, dentin, pulp
cavity, pulp, root canal

• Cavity surrounded by dentin that contains pulp
• Connective tissue, blood vessels, and nerves

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crown, enamel, root, neck, cementum, dentin, pulp
cavity, pulp, root canal

• Portion of the pulp cavity that extends into the
  root

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Dental caries and what causes them. (14)

• Gradual demineralization of enamel and dentin by
  bacterial action

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Causes

• Dental plaque, a film of sugar, bacteria, and
  mouth debris, adheres to teeth
• Acid produced by the bacteria in the plaque
  dissolves calcium salts
• Without these salts, organic matter is digested
  by proteolytic enzymes
• Daily flossing and brushing help prevent caries
  by removing forming plaque

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Gingivitis (15)

• As plaque accumulates, it calcifies and forms
  calculus, or tartar
• Disrupts the seal between the gingivae and the
  teeth
• Puts the gums at risk for infection

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Periodontitis (16)

• Serious gum disease resulting from an immune
  response
• Immune system attacks intruders as well as body
  tissues, carving pockets around the teeth and
  dissolving bone

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Digestion in the stomach type product (17)

• Chemical breakdown of proteins begins and food is
  converted to chyme
• Delivers chyme to the small intestine
• Enzymatically digests proteins with pepsin

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Function of goblet cells (18)

• Epithelial lining is composed of Goblet cells
  that produce a coat of alkaline mucus
• The mucous surface layer traps a bicarbonate-rich
  fluid beneath it

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Gastric Pits (18)

• Contain gastric glands that secrete gastric
  juice, mucus, and gastrin

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Cells their function in the stomach fundus and
body (19)

• Gastric glands of the fundus and body have a
  variety of secretory cells
• Mucus neck cells secrete acid mucus
• Parietal cells secrete HCl and intrinsic factor
  (Intrinsic factor is a glycoprotein necessary for
  the absorption of vitamin B12)
• Chief cells produce pepsinogen

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What is pepsinogen?

• Activated to pepsin by HCl in the stomach
• Pepsin (an enzyme) provides a positive feedback
  mechanism and functions to degrade food proteins
  to peptides (short polymers formed from the
  linking of amino acids)

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Chief cells of the stomach secrete the digestive
enzymes (pepsins) of the stomach
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The stomach does not digest itself! (20)

• The stomach produces a mucus lining secreted
  specialized cells which protects the stomach
  walls
• These cells are continuously replaced to maintain
  the protective coating
• Excessive secretions due to stress or smoking can
  form ulcers

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Stomach ulcer
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Major functions of the stomach (21)

• Holds ingested food
• Degrades this food both physically and chemically
• Delivers chyme to the small intestine
• Enzymatically digests proteins with pepsin

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Structural modification to increase surface area
in the small intestine (22)

• Plicae circulares - deep circular folds of the
  mucosa and submucosa of jejunum
• Villi - fingerlike extensions of the mucosa
• Microvilli - tiny projections of absorptive
  mucosal cells plasma membranes

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Plicae circulares - jejunum
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Intestinal villi small intestine throughout
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Microvilli brush borders of plasma membranes of
intestinal cells
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Small Intestine Histology of the Wall

• The mucosal epithelium is made up of
• Absorptive cells, goblet and other cells
• Cells of intestinal crypts secrete intestinal
  juice
• Peyers patches are found in the submucosa of
  ileum
• Brunners glands in the duodenum secrete alkaline
  mucus

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Intestinal crypts secretory glands in
epithelial lining of small intestine
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Peyers patches immune surveillance of ileum
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Brunners glands of duodenum

• Produce an alkaline secretion (containing
  bicarbonate) in order to
• protect the duodenum from the acidic content of
  chyme (which is introduced into the duodenum from
  the stomach)
• provide an alkaline condition for the intestinal
  enzymes to be active, thus enabling absorption to
  take place
• lubricate the intestinal walls.

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Brunners glands - duodenum
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Digestive juice composition function (23)

• Secreted by intestinal glands in response to
  distension or irritation of the mucosa
• Slightly alkaline and isotonic with blood plasma
• Largely water, enzyme-poor, but contains mucus

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