Digestive SystemLearning Targets 1-5

1. Trace the path of food in the digestive tract & describe the general structure & function of each organ mentioned

2. Describe peristalsis & state its function.3. Describe the wall of the small intestine & relate

its anatomy to nutrient absorption.4. Name the hormones produced by the digestive

tract that help control digestive secretions.5. 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

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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