Download Digestive Lecture

Hamish Darby 9956 2721
Hamish.darby@durack.edu.au
HLTAP401A Confirm health status
ESOMEPRAZOLE (Nexium)
Proton pump inhibitor ▼ Gastric acid
Drug of the week
METOCHLOPRAMIDE (Maxalon)
Anti-nausea
(Possibly Required Now)
Functions Of The Digestive System
Ingestion
 voluntary process
Propulsion
 food movement
 peristalsis (a) &
segmentation (b)
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Functions
Mechanical digestion
 mixing & churning of food
Chemical digestion
 large food molecules broken down to simple units
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Chemical Digestion
 Enzymes break down food molecules into
their building blocks
 Each major food group uses different
enzymes
 Carbohydrates are broken to simple sugars
 Proteins are broken to amino acids
 Fats are broken to fatty acids and glycerol
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Functions (c’td.)
Absorption
 transport of digested products from GI tract to blood or
lymph
Defecation
 elimination of indigestible substances from the body
Processes of
the
Digestive
System
Figure 14.11
The Digestive
System
Alimentary Canal
 Continuous, hollow, muscular tube
 Open at both ends
 Organs of the alimentary canal are:
 Mouth
 Pharynx
 Oesophagus
 Stomach
 Small intestine
 Large intestine
Accessory Digestive Organs
These Include
Teeth
Salivary Glands
Liver
Gallbladder
Pancreas
Mouth
 Lips
 Cheeks
 Hard palate
 Soft palate
 Tongue
 Tonsils
Processes Occurring in the Mouth
 Mastication (chewing) of food
 Mixing masticated food with saliva
 Initiation of swallowing by the tongue
 Allowing for the sense of taste
Accessory Digestive Organs Found in
the Mouth
 Teeth
 Salivary glands
Teeth
 Main function is mastication
 2 sets of teeth
 permanent
 deciduous
 Teeth are classified
according to shape
and function
Saliva & Salivary Glands
 Intrinsic and extrinsic
 Production of saliva
 Functions
 Cleanses the mouth
 Dissolves food chemicals – taste
 Moistens food and aids in bolus formation
 Begins to digest starches in the mouth
Pharynx & Oesophagus
Pharynx
 Oropharynx
 Laryngopharynx
Oesophagus
 Extends from the pharynx
to the stomach
 25cm long
Function of the Pharynx
 Serves as a passageway for air and food
 Food is propelled to the esophagus by two muscle layers
 Longitudinal inner layer
 Circular outer layer
 Food movement is by alternating contractions of the muscle
layers (peristalsis)
Oesophagus
 Runs from pharynx to stomach through the diaphragm
 Conducts food by peristalsis
(slow rhythmic squeezing)
 Passageway for food only (respiratory system branches off
after the pharynx)
Layers of Alimentary Canal Organs
Stomach
 C-Shaped structure
 Cardio-oesophageal & Pyloric sphincter
 Contains a
 Fundus
 Body
 Pylorus
 Rugae
 Lesser & Greater curvatures
Stomach Anatomy
Digestion In The Stomach
 Acts as a storage tank for food
 Site of food breakdown – Mechanical & Chemical
 Chemical breakdown of protein begins
 Delivers chyme (processed food) to the small intestine
Propulsion in the Stomach
 Food must first be well mixed
 Rippling peristalsis occurs in the lower stomach
 The pylorus meters out chyme into the small intestine (30 ml at a time)
 The stomach empties in four to six hours
Figure 14.15
Specialized Mucosa of the Stomach
 Simple columnar epithelium
 Mucous neck cells – produce a sticky alkaline mucus
 Gastric glands – secrete gastric juice
 Chief cells – produce protein-digesting enzymes (pepsinogens)
 Parietal cells – produce hydrochloric acid
 Endocrine cells – produce gastrin
Structure of the Stomach Mucosa
Figure 14.4b–c
Small Intestine
 Extends from pyloric sphincter to the ileo-caecal valve
 Chemical & mechanical digestion of foods
 Most food absorption occurs in the small intestine
3 divisions
Duodenum
Jejunum
Ileum
Chemical Digestion in the Small
Intestine
 Source of enzymes that are mixed with chyme
 Intestinal cells
 Pancreas
 Bile enters from the gall bladder
Chemical Digestion in the Small
Intestine
Villi of the Small Intestine
 Fingerlike structures formed
by the mucosa
 Give the small intestine more
surface area
Figure 14.7a
Microvilli of the Small Intestine
 Small projections of the
plasma membrane
 Found on absorptive cells
Figure 14.7c
Structures Involved in Absorption of
Nutrients
 Absorptive cells
 Blood capillaries
 Lacteals (specialized
lymphatic capillaries)
Figure 14.7b
Folds of the Small Intestine
 Called circular folds or plicae circulares
 Deep folds of the mucosa and submucosa
 Do not disappear when filled with food
 The submucosa has Peyer’s patches (collections of lymphatic
tissue)
Accessory Digestive Organs Involved in
Chemical Digestion in the Small Intestine
 Pancreas
 Liver
 Gallbladder
The Pancreas (Exocrine)
 Produces pancreatic enzymes to aid digestion
 pancreatic amylase
 trypsin, chymotrypsin, carboxypeptidase
 lipase
 Nucleases
 Very alkaline, therefore neutralises acidic chyme in the
duodenum
http://commons.wikimedia.org/wiki/File:Gallbladder1.png
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Endocrine products of pancreas
 Insulin
 Glucagon
The Liver
 Largest gland in the body
 Located under the diaphragm, right side of the body
 4 lobes
 Suspended from the diaphragm by the falciform ligament
 Produces bile for digestive processes
 Connected to the gall bladder via the common hepatic duct
Metabolic roles
 Regulation of lipids
 Regulation of blood glucose level through:
 Glycogenesis (glucose  glycogen)
 Glycogenolysis (glycogen  glucose)
 Gluconeogenesis (fat / protein  glucose)
 Protein metabolism through the building of blood and
clotting proteins
 Detoxifying role
 Produces cholesterol
Bile
 Produced by cells in the liver
 Composition
 Bile salts
 Bile pigment (mostly bilirubin from the breakdown of
hemoglobin)
 Cholesterol
 Phospholipids
 Electrolytes
The Gallbladder
 Small sac that is found in a depression of the inferior wall of
the liver
 Concentrates and stores bile
 Bile released via cystic & bile ducts in the presence of fatty
foods to duodenum
Large Intestine
 Larger diameter than small intestine
 Extends from ileo-caecal valve to the anus
 Major function is to reabsorb water and eliminate indigestible residue
Can be divided into
Caecum
Appendix
Colon
Rectum
Anal Canal
Large Intestine
Figure 14.8
Modifications to the Muscularis Externa
in the Large Intestine
 Smooth muscle is reduced to three bands (teniae coli)
 Muscle bands have some degree of tone
 Walls form pockets called haustra
Functions of the Large Intestine
 Absorption of water
 Eliminates indigestible food from the body as feces
 Does not participate in digestion of food
 Goblet cells produce mucus to act as a lubricant
Defecation
 Is the elimination of indigestible substances from the body
 Defecation reflex
Common Disorders...
 Normal functioning may be impaired as a result of alterations
to
 Swallow
 Secretory function
 Motility
 Digestion
 Absorbtion
 Elimination
Common Disorders of the Digestive
System
 Cholecystitis
 Acute or chronic inflammation of the gallbladder.
 Impaction of gallstones in the cystic duct – causes duct to fill with
bile, pus and blood
 Cholelithiasis – presence of stones in the gallbladder
 Choledocholithiasis – presence of stones in the common bile duct.
 Manifestations
 Intense pain – R upper quadrant
 Nausea and vomiting
 jaundice
Common Disorders of the Digestive
System
 Gastroenteritis
 Inflammation of the stomach and the intestines
 Causes include the ingestion of bacteria, amoebae, parasites,
viruses, toxins, food allergens or from drug reactions.
 Manifestations
 Nausea and vomiting
 Diarrhoea
 Abdominal cramps
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Alcoholism ↓ thiamine
Next Session
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Complete Assessment
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Read Agosta & Pakiam
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Refer to other texts as neccesary
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Suggestions and comments to
hamish.darby@durack.edu.au