Accessory Digestive Organs Chapter 14 Accessory Digestive Organs Salivary glands Teeth Pancreas...
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Transcript of Accessory Digestive Organs Chapter 14 Accessory Digestive Organs Salivary glands Teeth Pancreas...
Chapter 14Accessory Digestive OrgansAccessory Digestive Organs
• Salivary glands
• Teeth
• Pancreas
• Liver
• Gall Bladder
1. Salivary Glands1. 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 - 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 ToothRegions of a ToothCrown – 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. Pancreas3. 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 & Bile4. 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 Bladder5. 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 SystemProcesses 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 ActivityControl 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
Deglutition (Swallowing)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 StomachFood 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 AbsorptionDigestion 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 IntestineDigestion 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 JuiceStimulation of Pancreatic Juice
Vagus nerve
Local hormones
- Secretin
- Cholecystokinin
Absorption in the Small IntestineAbsorption in the Small Intestine
Water is absorbed along the length of the small intestine
End products of digestion
- Most substances are absorbed by active transport through cell membranes
- Lipids are absorbed by diffusion
Substances are transported to the liver by the hepatic portal vein or lymph
Absorption in the Large IntestineAbsorption in the Large Intestine
No digestive enzymes are produced
Resident bacteria digest remaining nutrients
- Produce some vitamin K and B
- Release gases
Water and vitamins K and B are absorbed
Remaining materials are eliminated via feces
Propulsion in the Large IntestinePropulsion in the Large Intestine
Sluggish peristalsis
Mass movements
- Slow, powerful movements
- Occur three to four times per day
Presence of feces in the rectum causes a defecation reflex
- Internal anal sphincter is relaxed
- Defecation occurs with relaxation of the voluntary (external) anal sphincter