NAT 212: Module 1, The Digestive System

Foods undergo three processes in the body:

1. Digestion (which is both mechanical and chemical) 2. Absorption 3. Metabolism.

Types of teeth

1. Incisors 2. Canines 3. Premolars or bicuspids 4. Molars or tricuspids. There are 32 permanent teeth.

List the Five Stages of Digestion:

1. Ingestion 2. Movement 3. Digestion 4. Absorption 5. Elimination Note: Secretion is also a primary mechanism of the digestive system.

What are the three components of the Pharynx?

1. Nasopharynx 2. Oropharynx 3. laryngopharynx

What are the three pairs of the salivary glands?

1. Parotids 2. Submandibulars and 3. Sublinguals which secrete about 1 liter and most of the saliva produced one day in adults.

The digestive system has two major components:

1. The Alimentary Canal 2. The Accessory Organs

salivary amylase

An enzyme in the saliva that starts the process of digesting carbohydrates ~ it is completed in the small intestine.

Lipase

An enzyme that breaks down lipids or fats

Protease

An enzyme that breaks down protein nutrients

Sublingual Glands

Are the smallest of the main salivary glands. They lie in from of the submandibular glands on the floor of the mouth. Each opens via 10 to 15 ducts in the floor of the mouth. They produce ONLY mucous type saliva.

Deciduous Teeth

Baby teeth totaling 20. They usually come in between 6 and 30 months and fall out between 6 and 13 years old.

Segmentation

Back & Forth Action: Segmentation contractions occur in the large intestine and small intestine. Segmentation contractions move chyme in both directions, which allows greater mixing with the secretions of the intestines. Segmentation involves contractions of the circular muscles in the digestive tract. Unlike peristalsis, segmentation actually can slow progression of chyme through the system.

3B. Chemical Digestion

Breaks down large non-absorbable food molecules into smaller absorbable nutrient molecules chemical. That includes chemical reactions catalyzed by enzymes in salive, gastric juice, pancreatic juice and intestinal juice.

Describe what happens to food in the large intestines

By the time food and digestive juices reach your large intestine, most digestion and nutrient absorption has already taken place. The large intestine's major jobs are to absorb excess water and to prepare feces -- or undigested waste material -- for removal via the rectum and anus.

Pancreatic islets of Langerhans

Cells that secrete the hormones glucagon and insulin into the blood.

Divisions of a Tooth

Crown, Neck and root. The crown is the portion that is visible and covered in enamel, the hardest tissue in the body. The outer shell is covered by dentin and cementum. Under the enamel of the tool is dentin. At the root there is a thin layer of cementum with dentin underneath.

5. Elimination

Defecation of unabsorbed food, dead cells, and bacteria

Describe the First Stage of the Digestion process ~ Mouth

Digestion starts in the mouth with the teeth. The chewing process is aided by saliva from the three saliva glands which turns the food into a bolus or mass. Then the enzyme salivary amylase starts the process of digesting carbohydrates. The swallowed food goes via the pharynx, through the esophagus or gullet to get to the stomach. Food is then moved into the stomach, via the lower esophageal sphincter, by waves of esophageal smooth muscle contraction known as peristalsis.

Dental Carries

Disease of the enamel, dentin and cementum of teeth that results in cavities.

Mouth or Oral Cavity

Food is ingested into the mouth. It is lined with mucous membranes with typically line hollow organs. Mucus produced by the lining of the GI tract protects the epithelium from digestive juices and lubricates food passing through the lumen.

2. Movement or Motility

Food is moved along at the appropriate pace, controlled by contraction of smooth muscle including peristalsis and segmentation

Mucosa or Mucous Membrane

In the esophagus, the mucosa is composed of tough and stratified abrasion-resistant epithelium. The mucosa throughout the rest of the tract is a delicate layer or simple columnar epithelium deigned for absorption and secretion. The mucus from either type of epithelium coats the lining of the alimentary canal

In what form are carbohydrates absorbed into the bloodstream?

Monosaccharides, the most abundant being glucose.

Fat Digestion

Most fats are digested in the small intestine. They then go through emulsification by bile in the duodenum or fat droplets are broken into very small droplets. Then pancreatic lipase splits up the fat molecules into fatty acids and glycerin. The end products are fatty acids and glycerol.

Secretion

Release of digestive juices containing enzymes, acids, bases, mucus, bile or other products that facilitate digestion. Some digestive organs also secrete endocrine hormones that regular digestion or metabolism of nutrients.

Describe what happens to food in the small intestines

The duodenum is a segment of intestine between the stomach and the jejunum that is very active in digestion where many different enzymes mix from the stomach, liver, gallbladder and pancreas. The small intestine is the location in the body where the majority of the nutrients from ingested food are absorbed.

What are the main divisions of the stomach?

The fundus, body and pylorus.

What is the role of the gallbladder?

The gallbladder is a small storage organ located inferior and posterior to the liver. Though small in size, the gallbladder plays an important role in our digestion of food. The gallbladder holds bile produced in the liver until it is needed for digesting fatty foods in the duodenum of the small intestine.

Lumen

The hollow space within the digestive tube.

Parotid Glands

The larges of the Salivary glads. located just below and in front of each ear @ the angle of the jaw. They contain ONLY serous type secretory cells containing enzymes.

Liver

The liver fills the entire upper right section of the abdominal cavity. Its cell secrete a substance called bile into ducts and is considered an exocrine gland. It is the largest gland in the body

Mesentery (MEZ-EN-TAIR-EE)

The loops of the digestive tract are anchored to the posterior wall of the abdominal cavity by a large double fold of peritoneal tissue called the mesentary.

What is the role of the large intestine?

The major function of the large intestine is to absorb water from the remaining indigestible food matter and transmit the useless waste material from the body. Food enters through ileocecal valve; external opening called anus. The walls contain smooth muscle fibers that contract to produce churning peristalsis and defecation. The lining is mucous membrane.

Serosa

The outermost covering or coat of the digestive tube. Consists of two layers; Connective tissue layer and peritoneum. In the abdominal cavity the serosa called the visceral peritoneum.

How does a sphincter muscle help the stomach perform its function?

The pyloric sphincter muscle stays contracted and hold the food in the stomach until partial digestion has occurred.

Identify the accessory organs of digestion.

The salivary glands, teeth, liver, gallbladder, appendix and pancreas.

Bolus

The teeth, with the help of powerful muscles called masseters and saliva secreted by the three salivary glands, turn the food into a mass or "bolus"

Mucous-type Saliva

Thick and slippery and produced by mucous-type secretory cells. Serves the important function of lubricating food during mastication allowing it to pass with less friction through the esophagus and into the stomach.

Serous-type Saliva

Thin, watery and free of mucus which contain the digestive enzyme salivary amylase produced by serous-type secretory cells. Do not contain mucous unless combined with mucous type saliva.

Muscularis

Two layers of muscle tissue that play an important role in producing movement of the GI tract during the digestive process allowing peristalsis and segmentation. Consist of circular muscle layer and longitudinal muscle layer.

Does some saliva contain both serous and mucous?

Yes, it is a mixture of both

What is bile and where does it come from?

a bitter greenish-brown alkaline fluid that is secreted by the liver and stored in the gallbladder. It contains significant quantities of cholesterol and bile salts that act as detergents to mechanically break up or emulsify fats. It is also important for the elimination of cholesterol from the body.

Define digestion

a complex process that occurs in the alimentary canal consisting of both physical and chemical digestion that prepares food for absorption.

What is Diarrhea?

a condition in which feces are discharged from the bowels frequently and in a liquid form.

Periodontitis

a generalized and serious type of inflammation and infection of teeth. It is the leading cause of tooth loss among adults and in often an infection of untreated gingivitis.

What is Jaundice?

a medical condition with yellowing of the skin or whites of the eyes, arising from excess of the pigment bilirubin and typically caused by obstruction of the bile duct, by liver disease, or by excessive breakdown of red blood cells.

Amalyse

a pancreatic enzyme that starts carbohydrate digestion by breaking down polysaccharides such as starches into disaccharides or double sugars.

Pharnynx

a tubelike structure made of muscle and lined with mucous membrane. It functions as part of the respiratory and digestive system. Air passes through to the lungs and food passes on its way to the stomach.

What is GERD or Gastroesophageal relfux disease?

backward flow of stomach acid up into the esophagus which typically include burning and pressure behind the breastbone.

Hard Palate

bony structure in the anterior or front portion of the mouth formed by parts of the palatine and maxillary bones.

What is an ulcer?

crater-like lesions, which destroy areas of the stomach or intestinal lining, causing gnawing or burning pain and may result in hemorrhage, perforation, scarring and other serious medical complications.

Root of a Tooth

fits into the bony socket that surrounds the upper or lower jaw bone. A fibrous periodontal membrane lines each tooth socket and anchors the tooth to the bone.

3. Digestion

is the process of breaking down food into smaller components (individual nutrients) to allow for absorption within the digestive tract. It consists of; A. Mechanical Digestion & Chemical Digestion

What is Chyme?

is the semi-fluid mass of partly digested food that is expelled by the stomach into the duodenum and moves through the intestines during digestion. It is created by the food being mixed in the stomach's walls combined with being broken down my gastric juices.

Pancreas location

lies behind stomach

Soft Palate

located above and posterior or rear of the mouth. It mainly consists of muscle.

Lacteal

lymphatic vessel in each villus of the intestine that absorbs lipids from the chyme passing through

Tongue

made of skeletal muscle covered with mucous membrane. It is anchored to bones in the skull and to the hyoid bone in the neck.

Duodenum

most of the chemical digestion occurs in this first subdivision of the small intestine.

Plicae

multiple circular folds in the intestinal lining

Esophagus

muscular, mucus lines tube that connects the pharynx with the stomach. It works as a passageway for food, pushing it towards the stomach. Mucus by glands in its mucosal lining lubricates the tube and makes it easier for the food to move into the stomach.

Gallstones

solid clumps of material that are mainly cholesterol which form in the gallbladder.

Define Enzymes

specialized protein molecules that speed up specific chemical reactions without themselves being changed or consumed in the process. The names of enzymes all end with the suffix -ASE.

Pulp Cavity

the center of a tooth containing connective tissue, blood, lymphatic vessels and sensory nerves.

The Body of the Stomach

the central part of the stomach

The fundus (Stomach)

the enlarged portion to the left of and above the opening of the esophagus into the stomach.

The pylorus

the lower narrow section of the stomach which joins the first part of the small intestine.

Minor & major duodenal papillae

the middle third of the duodenum contains the openings of ducts that empty pancreatic digestive juice and bile from the liver to the small intestine. These are the two openings.

Neck of a Tooth

the narrow portion joining the crown to the root

4a. Nutrient Absorption

the process which molecules of amino acids glucose, fatty acids and glycerol go from the inside of the intestines into the circulating fluids of the body. The lives of cells depends on absorption of digested food and its transportation to them by the circulating blood.

Oropharynx

the section of the pharynx that is actively and most directly involved in the digestive process with its important role in a specialized and coordinated type of GI tract motility involved in swallowing.

Maltase, Sucrase & Lactase

three intestinal enzymes that digest disaccarides into monosaccharides or SIMPLE SUGARS. Maltase digests maltose or malt sugar. Sucrase digest sucrose or ordinary cane sugar. Lactase digest lactose or milk sugar. The end product is monosaccarides with the most abundant being glucose.

hydrolysis

when enzymes speed up reactions that add water to chemically break up of split larger molecules into smaller molecules.

philtrum

*the vertical groove between the base of the nose and the border of the upper lip. *the junction between the two halves of the upper lip or of an animal's nose.

Submandibular Glands

Also called mixed or compound salivary glands because they contain both serous and mucus producing secretory cells. Located just below the mandibular angle, the size of a walnut and irregular in form. The open on the inside of the mouth on either side of the frenulum.

What are the three sections of the small intestine?

1. Duodenum 2. Jejunum 3. Ileum

Submucosa

A connective tissue layer which lies just below the mucosa containing blood vessels and nerves.

Peritoneum

A large moist, slippery sheet of serous membrane that lines the abdominal cavity and covers the organs located in it, including most of the digestive organs.

Describe what happens to food in the esophagus

After passing through the pharynx, the food enters the esophagus, a muscular tube that connects the pharynx to the stomach. muscle contractions push the food through the esophagus and toward the stomach.

Define metabolism

All chemical reactions involved in maintaining the living state of the cells and the organism. Metabolism can be conveniently divided into two categories: 1. Catabolism - the breakdown of molecules to obtain energy 2. Anabolism - the synthesis of all compounds needed by the cells. Energy formation is one of the vital components of metabolism.

Uvula

Cone shaped structure hanging down the center of the soft palate. It prevents any food and liquid from entering the nasal cavities above the mouth.

Mastication

Chewing

List and describe the four layers of the wall of the alimentary canal; compare the lining layer in the esophagus, stomach, small intestine, and large intestine

From the inside out: 1. Mucosa or mucous membrane 2. Submucosa 3. Muscularis 4. Serosa.

Is the pancreas an exocrine gland or an endocrine gland?

It is both an exocrine gland that secretes pancreatic juice into ducts and an endocrine gland that secretes hormones into the blood.

Define and contrast mechanical and chemical digestion

Mechanical digestion is physically breaking down the food to smaller pieces. Chemical digestion is the breaking a part of molecules.

Malacclussion

Miss-alignment of teeth causing problems to the temporomandiblar joint.

Carbohydrate digestion

Mostly occurs in the small intestine then pancreatic and intestinal juice enzymes digest the starches and sugars. Enzymes include Amalyse, maltase, sucrase & lactase. See below...

4. Absorption

Movement of the small absorb-able nutrients into the body from the gastro-intestinal (GI) tract

Peristalsis

Moves food forward: Smooth muscle contraction that moves food to the stomach which predominates in the esophagus. Occurs in alternating sequence with segmentation. Peristalsis involves one-way motion in the caudal direction and involves rhythmic contractions of the longitudinal muscles in the GI tract.

What happens when gallstones block the major deuodenal papilla?

Pain, jaundice & digestive problems

What role does the pancreas play in digestion?

Pancreatic juice is the most important digestive juice containing enzymes that digest all three major kinds of foods. It also contains sodium bicarbonate an alkaline substance that neutralizes the hydrochloric acid in the gastric juice that enters the intestines.

Describe what happens to the food in the stomach

Partial digestion of the food takes place here. The churning action of the stomach muscles physically breaks down the food. The stomach releases acids and enzymes for the chemical breakdown of food.

3A. Mechanical Digestion

Physically breaks large chunks of food into smaller ones. It includes GI motility such as chewing (mastication) Swallowing (deglutition), peristalsis, segmentation or defecation.

Carbohydrates include the following:

Polysaccharides (starch), disaccharides (sugars), and monosaccharides (sugars e.g. sucrose - white table sugar). Polysaccharides and disaccharides must be split into monosaccharides before the cells absorb them.

Protein Digestion

Starts in the stomach. Pepsinogen part of gastric juice in converted into active pepsin by hydrochloric acid. In the intestine trypsin in the pancreatic juice and peptidases in the intestinal juice finish the job of protein digestion. The end product is amino acids or "the protein building blocks".

Enzymes

Substances that aid in digestion. There are different enzymes to digest the different macronutrients; Proteins, Carbohydrates and Fats

Deglutition

Swallowing food

1. Ingestion

Taking food and other nutrients (such as herbs and supplements) into the body

The Alimentary Canal ~ Also known as gastrointestinal tract (GI tract)

The alimentary canal starts at the mouth, follows through to the pharynx, esophagus, stomach, small intestine, large intestine, and finally ends at the anal canal. This is often described as a "tube within a tube," or a tube within the body. It can also be thought of like a hallway through a building. It is almost 30 feel long.

Frenulum

attaches the tongue to the floor of the mouth.