GIT structure & function Flashcards
function of digestive system
also known as the gastrointestinal system
function : mechancial (teeth) and chemical (enzymatic) breakdown of food
–> break up food into simple, absorbable units
anatomy of digestive system
divided into 2 major components:
1) The gastrointestinal tract (GIT)
2) Accessory glands and organs
The gastrointestinal tract (GIT)
- 4.5 m tube running through out body with openings at
either end. - Consists of multiple organs joined in series
Accessory glands and organs
- Located outside the GIT. Secrete substances into the
lumen to aid digestion
The 4 layers of the GIT wall
- Mucosa- inner lining. Role in absorption
and secretion - Submucosa- middle layer with connective
tissue with blood and lymph vessels - Muscularis externa- outer wall
comprised of 2 (or 3 in stomach) layers
of smooth muscle: 1) circular and
2) longitudinal
–> plus 3) oblique in stomach - Serosa- a connective tissue
serosa role
a layer of the GIT wall
role : structure/support
–> ensure different regions of GIT are anchored in place to one another and also other regions of the body
submucosal plexus
part of the submucosa layer of the GIT wall
–> control secretion (because its close to the epithelial)
myenteric plexus role
in the muscularis externa
role: control muscle contraction
process of the GIT
- secretion
movement of material from cells into lumen or ECF - digestion
chemical and mechanical breakdown of food into absorbale units - absorption
movement of material from GI lumen to ECF - motility
movement of material through the GI tract as a result of muscle contraction
–> ensures digestion occurs in one direction
secretion in GIT
epithelial cells can secrete material into ECF, affect neighbouring cells or enter the blood
digestion in GIT
digesting food (chemical and mechanical) and breaking it into absorbale units in the lumen of the digestive tract
FOOD –> food + food + food
absorption in GIT
absorbable units from digestion in the lumen of the digestive tract is moved across the GIT wall, the interstitial fluid and into the blood
motility in GIT
muscle contractions so absorbale units from digestion can move through GIT tract
–> ensures digestion occurs in one direction
Oral digestion including salivation
Mastication (chewing) - mechanical digestion by lips, tongue,
teeth to generate a bolus that can be swallowednical digestion by lips, tongue, teeth to generate a bolus that can be swallowed
Salivation- soften and moisten food, taste, chemical digestion of carbohydrates, defense.
Phases of digestion ; cephalic
Three phases- cephalic, gastric and intestinal phases
Cephalic phase: Thinking, smelling, seeing, tasting food can stimulate parietal cells to produce gastric acid
o Prepares the stomach for the arrival of food
Vagus nerve innervates stomach wall