Digestive System

Digestion

• Introduction

• Physical Digestion

• Chemical Digestion

• Hepatic Portal System

Digestive System: Overview

Figure 24.1

Digestive Process

Figure 24.2

Figure 15.3

Essential Activities of Digestion

Figure 24.3a, b

Digestive Process

Figure 24.2

Mouth & Tongue

Figure 24.7a

Salivary Glands II

Figure 24.9a

Teeth

Figure 24.10.2

Digestive Processes in the Mouth

• Food is ingested

• Mechanical digestion begins mastication

• Propulsion is initiated by swallowing

• Salivary amylase

Deglutition (Swallowing)

Figure 24.13a-c

Thought Question

Esophagus

Figure 24.13d, e

Stomach

Figure 24.14a

Figure 15.17

Thought Question

Regulation of Gastric Secretion

• Stimulatory and inhibitory events occur in three phases– Cephalic (reflex) phase

– Gastric phase

– Intestinal phase

Cephalic Phase

• Excitatory events include:

• Inhibitory events include:

• Inputs come from olfactory receptors and taste buds hypothalamus vagal nuclei parasympathetic ganglion

Gastric Phase

• Excitatory events include:

• Inhibitory events include:

• Chemicals released– Gastrin

– Ach

– Histamine

Regulation and Mechanism of HCl Secretion

Figure 24.17

Gastric Contractile Activity

Figure 24.18

Intestinal Phase

• Excitatory phase

• Inhibitory phase

Regulation of Gastric Emptying

Figure 24.19

Microscopic Anatomy of the Small Intestine

Figure 24.21a-c

Figure 15.8

Figure 15.27

Figure 15.32

Figure 15.7

Large Intestine

Figure 24.29a

Chemical Digestion Carbohydrates

Figure 15.7

Chemical Digestion Protein

• Stomach– Pepsinogen Pepsin

• Small Intestine– Trypsin, Chymotrypsin, Carboxypeptidase– Brush Border Enzymes – Aminopeptidases– Carboxypeptidases

Thought Question

Figure 15.7

Chemical Digestion: Nucleic Acids

• Hydrolyzed to their nucleotide monomers by pancreatic nucleases present in pancreatic juice

• Absorption: active transport via membrane carriers– Absorbed in villi and transported to liver via hepatic

portal vein

• Enzymes used: pancreatic ribonucleases and deoxyribonuclease in the small intestines

Chemical Digestion of Fats

Figure 15.9

Figure 15.10

Figure 15.11

Fatty Acid Absorption

Figure 24.36

Pancreatic Enzymes

Hepatic Portal System

Thought Question

Summary

• Introduction

• Physical Digestion

• Chemical Digestion

• Hepatic Portal System