Digestive System
Learning Targets 1-5
1.
2.
3.
4.
5.
Trace the path of food in the digestive tract & describe
the general structure & function of each organ
mentioned
Describe peristalsis & state its function.
Describe the wall of the small intestine & relate its
anatomy to nutrient absorption.
Name the hormones produced by the digestive tract
that help control digestive secretions.
Name the accessory organs of digestion & describe their
contributions to the digestive process.
Trace the path of food in the digestive
tract & describe the general structure &
function of each organ mentioned (LT#1)
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Rectum
• Anus
The mouth (oral cavity) (LT#1)
• Bounded by lips, cheeks, palate, and
tongue
• Continuous with the oropharynx
posteriorly
• pg 299
• Carbohydrate digestion starts here
when amylase is secreted by salivary
glands
Palates and their functions (LT#1)
1. Hard palate pg 299
– Assists the tongue in chewing
2. Soft palate
– Closes off the nasopharynx during
swallowing
– Uvula projects downward from its free
edge
Uvula plays role in voice – gutteral
and click consonants
Function of the tongue (LT#1)
• Gripping and repositioning food during
chewing
• Mixing food with saliva and forming the
bolus
• Initiation of swallowing, and speech
Pharynx (LT#1)
• Where swallowing occurs
• Nasopharynx is covered when soft
palate moves back – so food doesn’t go
up your nose
• Glottis is the opening to the larynx @
top of trachea
• Epiglottis covers the trachea during
swallowing – so food doesn’t get into
lungs
Esophagus (LT#1)
• Connects mouth to stomach
• 2 sphincters: one near pharynx =
pharyngoesophageal & one near the
stomach = gastroesophageal
• Swallowing pushes bolus (food ball)
into the esophagus & peristalsis carries
it to stomach (pg 300)
• Peristalsis w/o food = sensation of lump
in your throat
Stomach (LT#1)
• Thick walled, J-shaped, upper left
quadrant
• Esophagus superior
• Duodenum inferior
• 3 layers of muscle & rugae (deep folds)
• Gastric glands secrete gastric juice
containing pepsin (digests proteins)
Figure 14.2
Intestines (LT#1)
•
•
•
•
Small 3 parts
Duodenum – base of stomach
Jejunum – 1st portion
Ileum – final portion before large
intestine
• Suspended by mesentery (pg 302)
Figure 14.11
Small intestine function (LT#1)
• Where majority of digestion occurs
• Villi increase surface area for absorption
of nutrients (pg 303)
• Digestive hormones control secretions
(Table 15.2 pg 301)
Large intestine or colon (LT#1)pg 307
•
•
•
•
•
•
•
•
Cecum
Vermiform appendix
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus
Figure 14.12
Large intestine function (LT#1)
• Absorbs water & electrolytes from
chyme
• Prepares indigestible material for
excretion from anus (bile gives color, E.
coli gives odor)
6 essential activities of the digestive
process (LT#1 summary)
•
•
•
•
•
•
Ingestion
Propulsion
Mechanical digestion
Chemical digestion
Absorption
Defecation
Describe peristalsis & state its function
(LT#2) pg 300
Describe the wall of the small intestine & relate
its anatomy to nutrient absorption (LT#3) pg 302
Name the hormones produced by the digestive
tract that help control digestive secretions
(LT#4) pg 301-302
Accessory digestive organs & their
contribution to digestion (LT#5)
•
•
•
•
Salivary glands
Liver
Gallbladder
Pancreas
Figure 14.5
Salivary glands and their function (LT#5)
• Three pairs of glands – parotid,
submandibular, and sublingual
• Cleanses the mouth
• Moistens and dissolves food chemicals
• Aids in bolus formation
• Contains enzymes that break down
starch
• Primary function is to begin digestion by
breaking down starch to simple sugars
Figure 14.10
Liver
• Largest gland has 2 lobes
• Functional unit is the lobule (100,000)
• “triad” consists of
(1) branch of hepatic artery brings
oxygenated blood
(2) branch of hepatic portal vein brings
nutrients from intestines
(3) bile duct shuttles bile away from liver
http://www.hopkinsgi.org/GDL_Disease.aspx?CurrentUDV=31&GDL_Cat_ID=BB532D8A-43CB416C-9FD2-A07AC6426961&GDL_Disease_ID=C8BD9205-E51B-4186-B4E4B5087B21F9EA
Liver function (page 304)
• Removes toxins from blood brought in
from intestines
• Removes & stores fat soluble vitamins
A, D, E, & K
• Makes plasma proteins from amino
acids (urea is byproduct)
• Pancreas influences liver by insulin &
glucagon to maintain blood glucose
level
Liver function continued
• Excess glucose stored as glycogen
• Produces bile that contains pigments
bilirubin & biliverdin (from breakdown
of hemoglobin – rbc pigment)
Gall Bladder
• Pear-shaped muscular organ attached
to ventral side of liver
• Stores excess bile produced in liver
• Bile enters duodenum to emulsify fats
so they can be further broken down by
lipase from the pancreas
Pancreas
• Rests on posterior wall behind stomach
• Cells produce pancreatic juice
containing sodium bicarbonate to
neutralize pH of chyme
• Digestive enzyme pancreatic amylase
for carbs
• Trypsin & chemotrypsin to digest
protein aka protease
• Lipase to digest fat