Transcript Digestion: Chewing & Dissolving

Digestion: Chewing & Dissolving
11 - 23
Differences between primary and
permanent teeth (11)
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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
All but the third molars have erupted by
the end of adolescence
There are usually 32 permanent teeth
Functional & structural differences between
the three different types of adult teeth (12)
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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
Parts & function of the adult tooth (13)
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Two main regions – crown and the
root
Crown: exposed part of the tooth
above the gingiva (gum)
(crown, enamel, root, neck, cementum,
dentin, pulp cavity, pulp, root canal)
• The portion of the tooth embedded in
the jawbone
crown, enamel, root, neck, cementum,
dentin, pulp cavity, pulp, root canal
• Constriction where crown & root come
together
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
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
crown, enamel, root, neck, cementum,
dentin, pulp cavity, pulp, root canal
• Cavity
surrounded by
dentin that
contains pulp
• Connective
tissue, blood
vessels, and
nerves
crown, enamel, root, neck, cementum,
dentin, pulp cavity, pulp, root canal
• Portion of the
pulp cavity that
extends into the
root
Dental caries and what causes them. (14)
• Gradual
demineralization of
enamel and dentin
by bacterial action
Causes
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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
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
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
Digestion in the stomach: type & product
(17)
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Chemical
breakdown of
proteins begins
and food is
converted to
chyme
Delivers chyme to
the small intestine
Enzymatically
digests proteins
with pepsin
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
Gastric Pits (18)
• Contain gastric
glands that secrete
gastric juice, mucus,
and gastrin
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
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)
Chief cells of the stomach secrete the
digestive enzymes (pepsins) of the
stomach
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
Stomach ulcer
Major functions of the stomach (21)
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Holds ingested food
Degrades this food both physically and
chemically
Delivers chyme to the small intestine
Enzymatically digests proteins with
pepsin
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
Plicae circulares - jejunum
Intestinal villi – small intestine throughout
Microvilli – brush borders of plasma
membranes of intestinal cells
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
• Peyer’s patches are found in the
submucosa of ileum
• Brunner’s glands in the duodenum
secrete alkaline mucus
Intestinal crypts – secretory glands in
epithelial lining of small intestine
Peyer’s patches – immune surveillance of
ileum
Brunner’s 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.
Brunner’s glands - duodenum
Digestive juice – composition & function
(23)
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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