Download Ch 14 B Accessory Organs

Chapter 14
Accessory Digestive Organs
• Salivary glands
• Teeth
• Pancreas
• Liver
• Gall Bladder
1. Salivary Glands
 3 glands
- Parotid glands – located anterior to ears
- Submandibular glands
- Sublingual glands
 Saliva
- Mostly water
- Mixture of mucus and serous fluids
- Helps to form a food bolus
- Salivary amylase begins starch digestion
- Dissolves chemicals so they can be tasted
2. Teeth - Masticates (chews) food
- Deciduous (baby or milk) teeth; 20 teeth by age two
- Permanent teeth; between the ages of 6 to 12; full
set = 32 teeth
Regions of a Tooth
Crown – exposed part
 Outer enamel
 Dentin
 Pulp cavity
Neck
 Region in contact with gum
 Connects crown to root
Root
• Periodontal membrane
attached to bone
• Root canal carrying blood
vessels and nerves
3. Pancreas
 Makes digestive enzymes
that break down all types
of food
 Enzymes secreted into
duodenum
 Alkaline fluid added with
enzymes neutralizes
acidic chyme
 Endocrine products of
pancreas
- Insulin
- Glucagons
4. Liver & Bile
 Largest gland; right side under the diaphragm
 4 lobes suspended by falciform ligament
 Connected to the gall bladder via common
hepatic duct
 Bile made by liver cells
 Bile composition
- Bile salts
- Bile pigment (bilirubin - breakdown of hemoglobin)
- Cholesterol
- Phospholipids
- Electrolytes
5. Gall Bladder
 Sac found in
depression of liver
 Stores bile from the
liver by way of the
cystic duct
 Bile is introduced into
the duodenum in the
presence of fatty food
 Gallstones can cause
blockages
Processes of the Digestive System
1. Ingestion – into mouth
2. Propulsion – moving foods
3. Mechanical digestion - Mixing
food
a. mouth & tongue
b. stomach churning
c. segmentation in sm. int.
4. Chemical Digestion Enzymes break down food
5. Absorption - products into the
blood or lymph
6. Defecation - Elimination of
indigestible substances as
feces
Control of Digestive Activity
 Controlled by reflexes of parasympathetic
division
 Chemical & mechanical receptors are located in
organ walls that trigger reflexes
 Stimuli include:
- Stretch of the organ
- pH of the contents
- Presence of breakdown products
 Reflexes include:
- Activation or inhibition of glandular secretions
- Smooth muscle activity
Food Ingestion and Breakdown
A. Mechanical and chemical digestion begin.
- Chewing
- Salivary Amylase begins to break starch into
maltose. Food or anything placed in mouth will
stimulate saliva production. So will certain emotions
or the mere thought of certain foods
B. No food absorption occurs in the mouth.
C. The pharynx and esophagus have no digestive function;
they simple provide a passageway to the stomach.
Deglutition (Swallowing)
A. Buccal phase – Voluntary, in mouth, bolus made,
tongue pushes into pharynx
B. Pharyngeal-esophageal phase - Involuntary, Tongue
blocks mouth, Soft palate (uvula) blocks the
nasopharynx, Epiglottis blocks the larynx, Peristalsis
moves the bolus, cardioesophageal sphincter opens
with pressure
Food Breakdown in the Stomach
 Gastric juice - regulated by
nerves & hormones
 Presence of food or falling pH =
release of gastrin
 Gastrin causes stomach glands
to produce protein-digesting
enzymes
 Hydrocholoric acid makes
stomach very acidic
- Activates pepsinogen to pepsin for
protein digestion
- Provides a hostile environment for
microorganisms
Digestion and Absorption
 Protein digestion enzymes
- Pepsin – an active protein digesting enzyme
- Rennin – works on digesting milk protein
 The only absorption that occurs in the
stomach is of alcohol and aspirin
 Stomach empties in 4-6 hrs.
Digestion in the Small Intestine
 Enzymes from the brush border
- Break double sugars into simple sugars
- Complete some protein digestion
 Pancreatic enzymes
- Help complete digestion of starch (pancreatic
amylase)
- Carry out about half of all protein digestion (trypsin,
etc.)
- Responsible for fat digestion (lipase)
- Digest nucleic acids (nucleases)
- Alkaline content neutralizes acidic chyme
Stimulation of Pancreatic Juice
 Vagus nerve
 Local hormones
- Secretin
- Cholecystokinin
Absorption in the Small Intestine
 Water absorbed
 Nutrient absorption
- Mostly by active
transport
- Lipids absorbed by
diffusion
 Substances
transported to liver by
the hepatic portal
vein or lymph
Absorption in the Large Intestine
 No digestive enzymes
are produced
 Resident bacteria digest
remaining nutrients
- Produce vitamins K & B
- Release gases
 Water and vitamins K
and B are absorbed
 Remaining materials
are eliminated via feces
Propulsion in the Large Intestine
 Sluggish peristalsis
 Mass movements
- Slow, powerful movements
- Occur 3-4 times per day
 Presence of feces in rectum
causes defecation reflex
- Internal anal sphincter is
relaxed
- Defecation occurs with
relaxation of the voluntary
(external) anal sphincter