15 - 1

Chapter 25,26,27Digestion and Nutrition

15 - 2

General Characteristics of the Alimentary Canal

• Approximately 27 feet• Structure of the wall – 4

layers– Mucosa - protects– Submucosa- nourishes– Muscular – propel food – Serosa - secretes serous

fluid – lubrication• Movements of the tube

(peristalsis) – Mixing– Propelling

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 3

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Peristalsis

15 - 4

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Mouth - oral cavity• Cheeks and lips• Tongue – held down by frenulum• Palate

– Hard palate– Soft palate

• Teeth– Primary– Secondary– Incisors, cuspids, bucuspids, molars

15 - 5

teeth

15 - 6

Salivary Glands• Salivary secretions

– Serous cells– Amylase - digests carbohydrates– mucous

• Major salivary glands– Parotid– Submandibular– Sublingual

15 - 7

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Salivary glands

15 - 8

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

pharynx• Structure

– Nasopharynx– Oropharynx– Laryngopharynx

• Swallowing mechanism– Food mixed and forced into pharynx– Sensory receptors trigger swallowing reflex– peristalsis

15 - 9

Esophagus• Collapsible passageway leading to stomach

• Mucous glands

• Esophageal sphincter

15 - 10

The stomachCopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 11

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Stomach• Parts of the stomach

– Cardiac, fundic, body, pyloric– Pyloric sphincter

• Gastric secretions - mucus, pepsin, hydrochloric acids, intrinsic factor

• Regulation of gastric secretions– Parasympathetic impulses, gastrin (increases

secretions of gastric glands

• Gastric absorption• Mixing and emptying actions (chyme)

15 - 12

pancreas• Produces pancreatic juices which aid in

digestion

• Located in association with the small intestine

• Structure of the pancreas– Acinar cells – produce pancreatic juices.– Travel through Pancreatic duct– Controlled by Hepatopancreatic sphincter

15 - 13

• Pancreatic juice– Digest organic compounds– Amylase, lipase, chymotrypsin (trypsin),

carboxypeptidase, nucleases

• Regulation of pancreatic secretions– Secretin - stimulates release of pancreatic fluid– cholecystokinin

15 - 14

The PancreasCopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 15

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 16

The liver• Location

• Structure– Hepatic lobules, sinusoids– Hepatic portal vein– Kupfer cells

• Function - metabolism of glucose from noncarbohydrates, storage of vitamin D, filter blood, digestion

15 - 17

Bile• Functions of bile salts-emulsify fat• Made in liver• Gallbladder - stores bile • Composition of bile- water, bile salts, bile

pigments, cholesterol, electrolytes• Regulation of bile release -

cholecystokinin, hepatopancreatic sphincter

Small Intestine• Function

– Receives pancreas and liver secretion, completes digestion of nutrients, absorbs products of digestion, transports residues to large intestine.

• Parts of the small intestine– Duodenum, jejunum, ileum– Duodenum – shortest, fixed portion– Suspended by mesentery

• Small intestinal wall– Lined with villi – connective tissue and capillaries– 4 layers

• Secretions– Goblet cells – secrete mucous– Intestinal gland – watery fluid– Digestive enzymes

• Regulation of secretion – mechanical and chemical stimulation – release of mucous• Absorption of nutrients

– Monosacharides – facilitated diffusion– Amino acids – active transport– Fatty acids – encapsulated then absorbed

• Movement - peristalsis

15 - 19

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 20

Large intestine• Parts – ascending colon, transverse colon,

descending colon• Structure of wall

– 4 layers– No villi

• Functions - reabsorption of water from chyme• Movements accomplished by peristalsis• Feces – waste products

– Contain undigested material, mucous, water, bacteria– Color – bile salts– Smell – bacterial action

15 - 21

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 22

Nutrition and NutrientsA. Nutrition is the process by which the body

takes in and uses nutrients.

B. Essential nutrients are those that cannot be synthesized by human cells.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 - 23

Carbohydrates• Sources

• Utilization

• requirements

15 - 24

Lipids

• Sources

• Utilization

• Requirements

15 - 25

proteins• Sources

• requirements

15 - 26

vitamins• Fat soluble

• Water soluble

15 - 27

minerals• Characteristics

• Major minerals

• Trace elements