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Digestive System (Mouth (Food is ingested (salvia (mixture of mucosa and…
Digestive System
Mouth
Propulsion
is initiated by swallowing
Mechanical
digestion begins
Food is ingested
salvia
mixture of mucosa and serous fluid
forms a food bolu
contains salivary amylase
Chemical
breakdown of starch begins
The
pharynx and oesophagus
is the passageway for food
Esophagus
4 layers within the wall
Peristalsis
Runs from pharynx to stomach
Large intestine
No digestive enzymes produced but bacteria digests remaining nutrients
Remaining materials are
eliminated
= feces
Propulsion:
Mass movements
Presence of faces
in the rectum causes a
defection reflex
Process
Absorption:
end products of digestion are absorbed into blood or lymph
Defecation:
elimination of indigestible substances as feces
Ingestion-
voluntary movement of food into mouth
Defecation process
Mass movements force feces into rectum and
stretch wall
to signal the
defecation relflex
Internal sphincter
relax (involuntary)
External sphincter-
remains closed (voluntary)
Rectum is typically empty
Digestive organs
Accessory digestive organs
Salivary glands
Tongue
Teeth
Pancreas
Liver
Gall bladder
GI tract/ Alimentary canal
Large intestine
Rectum
Small intestine
Anus
Stomach
Esophagus
Pharynx
Mouth
Structure
Submocosa
- blood supply and nerves
Musculares externa-
smooth muscle (circular and longitudinal)
Mucosa -
innermost and moist/mucus membrane
Serosa-
anchors organs
Stomach
Function
Food breaks down into smaller fragments-
chyme
Peristalsis
occurs -movement
Pylorus
lets out
chyme
into
small intestine
Anatomy
Rugae
- folds of the mucosa
Food empties into
small intestine
at the
pyloric sphincter
(3mls)
Food enters at the
cardioesophageal sphincter
Storage tank- Volume of 50ml to 4L
Mucosa
Mucus surface layer traps a
bicarbonate fluid
beneath it
Goblet cells
produce alkaline mucus
Gastric pits
Mucous neck cells-
secrete mucus
Parietal cells-
secrete HCl and intrinsic factor
Chief cells-
produce pepsinogen and is activated by HCl in the stomach
Digestion
Mechanical
Mastication/chewing- grinding and mixing of food in the
mouth
by teeth and tongue
Churning of food in the
stomach
Segmentation (mixing) in the
small intestine
Chemical
Enzyme break down food molecules into smaller units
Carbohydrates-
are broken down into simple sugars
Proteins-
broken to simple sugars
Fats-
broken to fatty acids and glycerol
Small intestine
Anatomy
Jejunum
Duodenum-
bile duct empties secretions into the small intestine
Ileum
Circular folds
- absorption and slow down passage of chyme
Villi-
larger SA for absorption and secretes brush border enzymes
Peristalsis
- moving of food
Segmentation
- mix of chyme and juices
Absorption-
Pancreas
Control
blood glucose levels
- insulin and glucagon
Produces
digestive enzymes
to break down food and secreted into duodenum
Liver
Largest gland
in the body
Produces bile-
emulsifies fat
to aid enzymatic breakdown