DIGESTIVE SYSTEM Performs 3 tasks: Mechanical Digestion – No chemical reactions 2. Chemical Digestion – Chemical reactions 3. Absorbtion – Absorbing nutrients into blood system

Pg. 650 Fig. 15.01 Accessory Organs Alimentary Canal

Pg. 8 Packet

Fig. 15.02 Pg 651 8 meters (24 feet) from Mouth to Anus 186 square meters total surface area

Movements of the Tube 1.The motor functions of the alimentary canal are of two types— mixing movements and propelling movements. 2. Mixing movements occur when smooth muscles contract rhythmically in small sections of the tube. 3. Propelling movements include a wavelike motion called peristalsis, which is caused by contraction behind a mass of food as relaxation allows the mass to enter the next segment of the tube.

Pg. 653 Mixing Movement Propelling Movement Peristalsis

Fig. 15.06 Pg. 655

Fig. 15.05 Pg. 653

Pg. 655

Pg. 656

Fig. 15.09 Pg. 657

Pepsi 2.49 Gatorade 2.4 Vitamin Water 3-4 Grapefruit Juice 2.8 Red Bull 3.5 Milk 6.8 Coke 2.53 Snapple Tea 3.2 Orange Juice 3-4 V9Splash Berry 3.1 SoBe Tropical 2.5

Fig. 15.10 SALIVARY GLANDS Pg. 658 1. Amylase 3. 2. Amylase & Mucus Serous Cells 1. Amylase 3. Mucous Cells Serous & Mucous Cells 2. Amylase & Mucus

Swallowing Mechanism Swallowing reflexes can be divided into three stages. a. Food is mixed with saliva and voluntarily forced into the pharynx with the tongue. b. Sensory receptors in the pharynx sense food, which triggers swallowing reflexes. c. In the third stage of swallowing, peristalsis transports the food in the esophagus to the stomach.

Structure of the Wall 1.The wall of the alimentary canal consists of the same four layers throughout its length, with only slight variations according to the functions of specific sections of the canal.

4 Layers of Alimentary Canal Pg. 652 1. 2. 3. 4.

The inner layer is the mucosa, which is lined with epithelium attached to connective tissue; it protects tissues of the canal and carries on secretion and absorption. The next layer is the submucosa, which is made up of loose connective tissue housing blood and lymph vessels and nerves; it nourishes the surrounding layers of the canal. The muscular layer consists of inner circular fibers and outer longitudinal fibers that propel food through the canal. d. The outer layer, or serosa, is composed of visceral peritoneum that protects underlying tissues and secretes serous fluid to keep the canal from sticking to other tissues in the abdominal cavity.

STOMACH Pg. 662 Body Region

Gastric Secretions Gastric glands within the mucosa of the stomach open as gastric pits. Gastric glands generally contain three types of secretory cells. a. Mucous cells produce mucus that protects the stomach lining. b. Chief cells secrete pepsin (to digest protein) as inactive pepsinogen, which is activated when it comes in contact with hydrochloric acid. c. Parietal cells secrete hydrochloric acid. d. Other components of gastric juice include intrinsic factor, required for vitamin B12 absorption from the small intestine.

Pg. 664 a. b,. c.

Pg. 665

Gastric Absorption 1. The stomach absorbs only small quantities of water and certain salts, alcohol, and some lipid-soluble drugs.

Mixing and Emptying Actions Following a meal, mixing actions of the stomach turn the food into chyme and pass it toward the pyloric region using peristaltic waves. The rate at which the stomach empties depends on the fluidity of the chyme and the type of food. As chyme fills the duodenum, stretching of its wall triggers the enterogastric reflex, which inhibits peristalsis and slows the rate at which chyme enters the small intestine.

Regulation of Gastric Secretions SECRETIONS INCREASED: Gastric secretions are enhanced by parasympathetic impulses from vagus nerve and the hormone gastrin, which is released from gastric glands. Gastrin stimulates the release of gastric juices and the release of histamine, which stimulates the release of HCL. SECRETIONS DECREASED: As more food enters the small intestine, secretion of gastric juice from the stomach wall is inhibited. Sympathetic impulses aid in inhibition a. Presence of fats and proteins in the upper small intestine causes the release of the hormone cholecystokinin (CCK) from the intestinal wall, which also decreases gastric mobility.

PG 665

PANCREAS Fig. 15.14 Pg. 668

Pg. 669

Regulation of Pancreatic Secretion The nervous and endocrine systems regulate release of pancreatic juice. The hormone Secretin from the duodenum wall stimulates the release of pancreatic juice with a high bicarbonate ion concentration. Neutralizes acidic chyme. The hormone Cholecystokinin (CCK) also from the duodenum wall stimulates the release of pancreatic juice with a high concentration of digestive enzymes.

Pg. 669

PANCREAS Pancreatic Juice Pancreatic juice contains enzymes that digest carbohydrates, fats, proteins, and nucleic acids. Pancreatic enzymes include: pancreatic amylase (Carbs), pancreatic lipase (Lipids), trypsin, chymotrypsin, carboxypeptidase (Proteins) two nucleases (Nucleic Acids). 3. Protein-digesting enzymes are released in an inactive form and are activated upon reaching the small intestine.

Fig. 15.14 Pg. 668

Fig. 15.16a LIVER Pg. 671

Liver Structure The liver is divided into right and left lobes, and is enclosed by a fibrous capsule. Each lobe is separated into hepatic lobules consisting of hepatic cells radiating from a central vein. These are the livers functional units. Hepatic sinusoids (Vascular channels) separate groups of hepatic cells. Hepatic Lobule Bile Duct Pg. 671 Sinusoids Central Vein

4. Blood from the hepatic portal vein carries blood rich in nutrients to the liver. 5. Kupffer cells carry on phagocytosis in the liver. 6. Secretions from hepatic cells are collected in bile canals that converge to become hepatic ducts and finally form the common hepatic duct. Hepatic Cells Bile Duct Kupffer Cell Branch of Hepatic portal vein Pg. 672

Table. 15.03 Pg. 673

Liver Functions 1.The liver's main role in digestion is to secrete bile.

Composition of Bile Bile is a yellowish-green liquid that hepatic cells secrete; it includes water, bile salts, bile pigments, cholesterol, and electrolytes. Bile pigments are breakdown products from red blood cells. 3. Only the bile salts have a digestive function.

Functions of Bile Salts Bile salts emulsify fats into smaller droplets and aid in the absorption of fatty acids, cholesterol, certain vitamins.

If Bile is used right away goes from Hepatic (Bile) Duct, down the common bile duct into the small intestine. If Bile is not used right away it goes from Hepatic (Bile) Duct, into Cystic Duct and then stored in the Gallbladder Pg. 671

Pg. 668

Fig. 15.19 Regulation of Liver and Gallbladder secretion Pg. 675

SMALL INTESTINE

SMALL INTESTINE Fig. 15.21 Pg. 676

Fig. 15.22 Pg. 677

Structure of the Small Intestinal Wall The inner wall of the small intestine is lined with finger-like intestinal villi, which greatly increase the surface area available for absorption and aids in mixing actions. Each villus contains a core of connective tissue housing blood capillaries and a lymphatic capillary called a lacteal. 3. Between the bases of adjacent villi are tubular intestinal glands.

Pg. 652

Embedded in the epithelial cells of the villi are digestive enzymes that break food molecules down one last time before absorbtion: They include: SUCRASE, MALTASE AND LACTASE – Breakdown disaccharides to monosaccharide PEPTIDASES Breakdown peptides to amino acids INTESTINAL LIPASE Breakdown fats into fatty acids and glycerol

Fig. 15.24 Pg. 678 Lack digestive enzymes Abundant in digestive enzymes SUCRASE, MALTASE, LACTASE PEPTIDASES INTESTINAL LIPASE Pg. 678 Lack digestive enzymes

Fig. 15.25 Pg. 678 Epithelial cells are continually replaced New cells made in intestinal glands, migrate onto villus surface. When they reach the tip of villus they shed. Epithelial cells of small intestine replaced every 3-6 days.

Fig. 15.24 Pg. 678 Lack digestive enzymes Abundant in digestive enzymes SUCRASE, MALTASE, LACTASE PEPTIDASES INTESTINAL LIPASE Pg. 678 Lack digestive enzymes

Pg.682

PG 681 Fig. 15.26

Lipoproteins – Made up of phospholipid, protein, cholesterol and triglycerides. Types of Lipoproteins Chylomicrons – transport dietary fat to muscle and adipose cells. 2. VLDL – transport triglycerides to adipose cells 3. LDL – transports cholesterol to tissue cells 4. HDL – transports cholesterol from tissue cells to liver where it becomes part of the bile salts or is eliminated from intestine.

Pg. 675

Table. 15.05 Pg. 680

Structure of the Large Intestinal Wall The large intestinal wall has the same four layers found in other areas of the alimentary canal, but lacks many of the features of the small intestinal mucosa such as villi. 2. Fibers of longitudinal muscle are arranged in teniae coli that extend the entire length of the colon, creating a series of pouches (haustra).

Pg. 683 2. Transverse Colon 1. Ascending Colon 3. Decending Colon 4. Rectum 5. Anus

Fig. 15.28 Pg. 684

Functions of the Large Intestine The large intestine does not digest or absorb nutrients, but it does secrete mucus. The large intestine absorbs electrolytes and water. 3. The large intestine contains important bacteria which break down cellulose for energy and in return synthesize vitamins k, B12, thiamine and riboflavin.

Movements of the Large Intestine The movements of the large intestine are similar to those of the small intestine. Peristaltic waves happen only two or three times during the day. 3. Defecation is stimulated by a defecation reflex that forces feces into the rectum where they can be expelled.

Feces Feces are composed of undigested material, water, electrolytes, mucus, epithelial cells of the small intestine and bacteria. 2. Both the color of feces and its odor is due to the action of bacteria.

Pg. 684

Secretions of the Small Intestine Cells that secrete mucus in the small intestine include goblet cells, which are abundant throughout the mucosa, and mucus-secreting glands located in the submucosa of the duodenum. Intestinal glands at the bases of the villi secrete large amounts of watery fluid that carry digestive products into the villi. 3. Epithelial cells of the mucosa have embedded digestive enzymes on their microvilli, including peptidases, sucrase, maltase, and lactase, and intestinal lipase.

4. Fatty acids are absorbed and transported 4. Fatty acids are absorbed and transported differently than the other nutrients. a. Fatty acid molecules dissolve into the cell membranes of the villi. b. The endoplasmic reticula of the cells reconstruct the lipids. c. These lipids collect in clusters that become encased in protein (chylomicrons). d. Chylomicrons are carried away in lymphatic lacteals until they eventually join the bloodstream. 5. The intestinal villi also absorb water (by osmosis) and electrolytes (by active transport).

Liver Functions The liver carries on many diverse functions for the body. The liver is responsible for many metabolic activities, such as the metabolism of carbohydrates, lipids, and proteins. The liver also stores glycogen, vitamins A, D, and B12, iron, and blood. The liver filters the blood, removing damaged red blood cells and foreign substances, and removes toxins. 5. The liver's role in digestion is to secrete bile.