Transcript Digestive System

Digestive System
Fig 23.1
Digestive System
Organs of the digestive system
– GI Tract Organs- mouth, pharynx, esophagus,
stomach, small intestine, large intestine
GI tract also called the alimentary canal,
digestive tract or gut
– Accessory Digestive Organs- teeth, tongue,
salivary glands, gall bladder, liver, pancreas
Gastrointestinal Mucosa- moist covering and
lining membrane lining the inside of the GI tract
absorbs nutrients- aided by large surface area due to
villi and microvilli esp. in sm. intestine
secretes mucin —> mucous for lubrication,
protection
protects- mucosal immune functions (MALT)
gastric mucosa has specialized secretory cells
Figure
23.22
23.15 b and c
Digestive System
Gastrointestinal Tract Activities/Processes
1. Ingestion-intake of food
2. Propulsion-movement of food through the GI tract
Peristalsis-alternative contraction and relaxation of adjacent sections
of the alimentary tract resulting in food propulsion
3. Mechanical digestion-chewing,mixing, stomach churning,
segmentation
Segmentation-alternative contraction and relaxation of nonadjacent sections of the alimentary tract, resulting in mixing
of food
4. Chemical digestion-catabolic steps which break down complex
molecules to monomers or fragments which can be absorbed by the
GI tract
5. Absorption uptake of nutrients from the lumen of the GI tract into
blood or lymph via passive and active transport
6. Defecation- elimination of indigestible substances from the body
23.2
Overview of the functions of the
Gastrointestinal Tract
Table 23.2
Microscopic Anatomy of the stomach
*read pp
869 to 871
up to “Digestive Processes….”
Secretory cells of the gastric pits:
Know what Chief cells, Parietal cells and
Enteroendocrine cells of the stomach mucosa are
and their function(s)
23.15c
The small intestine duodenum, jejunum, ileum
• Digestion is completed and most absorption
occurs here
– Villi-fingerlike projections containing
underlying:
• Capillary bed- Absorbs most nutrients and water
soluble drugs and some lipophilic drugs
• Lymphatic capillary (lacteal)- Absorbs fats and
highly lipophilic drugs
Accessory Digestive Organs: Liver, Gall
Bladder, Pancreas
1. Liver-largest gland in the body located below the
diaphragm-has numerous functions
function in GI tract processes-production of bile, a
yellow-green alkaline fluid containing bile salts that is
released into the small intestine (duodenum) via the bile duct;
main function of bile →is to emulsify fats
Liver Functions
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carbohydrate metabolism/storage
detoxification
serum protein production
hormone inactivation
protein metabolism/urea production
lipid metabolism
iron recycling
cholesterol synthesis
Structure of the liverA. gross anatomy
4 lobes- left, right,caudate and quadrate
functional units- liver lobules
B. microscopic anatomy of liver lobuleshepatocytes- mature liver cells that perform most
of the liver functions
arranged in ‘plates’;
high regeneration capacity
B. microscopic anatomy of liver lobules
hepatocytesPerform main
Functions of the
Liver.
optional Fig 23.25
Fig. 23.25
B. microscopic anatomy of liver lobules
hepatocytes- mature liver cells that perform most of
the liver functions
arranged in ‘plates’;
high regeneration capacity
Fig. 23.25
Accessory Digestive Organs: Liver, Gall
Bladder, Pancreas
2. Gall Bladder-thin-walled muscular sac located below the
ventral portion of the liver that stores and concentrates
bile
bile transferred from liver to gall bladder via common
hepatic duct
3. Pancreas- digestive function-produces pancreatic juice
containing digestive enzymes (proenzymes) for release into
duodenum via the main and accessory ducts
Flowchart of chemical digestion and
absorption of foodstuffs
optional Fig. 23.32
Fig. 23.32
hepatic portal circulation