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Chapter 5 Care of the Patient with aGastrointestinal Disorder

Chapter 5 Care of the Patient with aGastrointestinal Disorder

Function and Design ofFunction and Design ofthe Digestive Systemthe Digestive System

Chief functions• Digestion• Absorption• Elimination

• Organs• Digestive tract – mouth, pharynx, esophagus,

small intestine, large intestine, and rectum• Accessory organs – salivary glands, gallbladder,

liver, and pancreas

Wall of the digestive tract. The mucous membrane of the small intestine shown here has numerous projections called villi.  Zooming InWhat type of tissue is between the submucosa and the serous membrane in the digestive tract wall?

The Peritoneum

Membranes that line the abdominopelvic cavity:

• *Parietal peritoneum• *Visceral peritoneum• Mesentery• Mesocolon• Greater omentum• Lesser omentum

Parietal peritoneum -- the membrane lining the abdominal cavity (as opposed to the visceral peritoneum that envelops the abdominal organs).

The abdominopelvic cavity. Subdivisions of the peritoneum fold over, supporting and separating individual organs.  Zooming InWhat part of the peritoneum is around the small intestine?

THE DIGESTIVE TRACT

• The digestive tract, or alimentary canal, is a musculo-membranous tube that extends about 30 feet from the mouth to the anus.

• It consists of the mouth, pharynx, esophagus, stomach small intestine, and large intestine.

• Food moves through this canal by means of peristalsis, a series of contractions that are rhythmic and coordinated. Peristalsis also moves bile through the bile duct, and urine through the ureters.

• Accessory organs aid in the digestive process, but are not considered a physical part of the digestive tract.

Overview of Anatomy and Physiology

• Digestive system– Organs and their functions

• Mouth: beginning of digestion– Teeth: bite, crush, and grind food

– Salivary glands: secrete saliva

• Pharynx: transfers food bolus to esophagus

• Esophagus: moves food from mouth to stomach

• Stomach: churn and mix contents with gastric juices

• Small intestine: most digestion occurs here

• Large intestine: forms and expels feces

• Rectum: expels feces

THE MOUTH

The Teeth• Deciduous teeth (baby teeth)

• 20 teeth• Adult permanent teeth

• 32 teeth• Incisors• Cuspids (canines or eyeteeth)• Molars

• Structure• Dentin• Blood vessels • Nerves• Gingiva• Crown• Enamel• Roots• Cementum

Tongue & Pharynx

The Pharynx

Also called the throat• Oropharynx• Palatine tonsils• Nasopharynx• Laryngeal pharynx• Soft palate• Uvula• Epiglottis

THE ESOPHAGUS• It is a 10 inch muscular, collapsible tube.

• No digestion occurs here.

• Peristalsis moves the food down into the stomach in about 5-6 seconds.

PERISTALSIS

Figure 5-1

Location of digestive organs.

The Order of Digestion

• The mouth is the entrance to the digestive system. The tongue is at the floor of the mouth (a muscular appendage that is involved in chewing, speaking, and swallowing). Tiny elevations, called papillae, contain the taste buds. In the mouth, the teeth shred and grind the food. Enzymes (Salivary Amylase or Ptyalin) begin the chemical breakdown of carbohydrates.

THE STOMACH• It is in the left upper quadrant (LUQ) of the

abdomen.• The entrance is the cardiac sphincter (also

called the Lower Esophageal Sphincter {LES}).

• The exit is the pyloric sphincter.• As food leaves the esophagus through the

relaxed cardiac sphincter, it then enters the stomach when the sphincter contracts. This prevents food from refluxing back into the esophagus. Reflux can be irritating.

THE STOMACH, cont.

• Once the food has entered the stomach, the muscular layers churn and contract to mix and compress the contents with gastric juices and water. The gastric juices are secretions that are released by the gastric glands.

• Protein digestion begins in the stomach. Hydrochloric acid softens the connective tissue of meats, kills bacteria, and activates pepsin (the chief enzyme of gastric juices that converts proteins into proteases and peptones)

THE STOMACH, cont.

• Mucin is released to protect the stomach lining.• Intrinsic factor (a substance secreted by the

gastric mucosa) is produced to allow absorption of vitamin B12.

• After the stomach is finished, the food is broken down into a viscous, semi-liquid substance called chyme. The chyme is then sent through the pyloric sphincter to the duodenum.

CHYME

SMALL INTESTINE

– It is about 20-25 feet long and one inch in diameter.

– It begins at the pyloric sphincter and ends at then ileocecal valve.

– There are 3 sections: duodenum, jejunum, and the ileum.

– Most digestion occurs here; about 90%.– Bile and pancreatic juices enter the

duodenum. – Bile breaks fat molecules into smaller

droplets, which enables the digestive juices to complete their process (emulsify).

SMALL INTESTINE, cont.

• Pancreatic juices contain water, inorganic salts, proteins, and enzymes.– They break down proteins to amino

acids; reduce dietary fats to glycerol and fatty acids; convert starches to simple sugars.

• The inner surface of the small intestine contains villi (these are tiny, fingerlike projections which are clustered over the entire surface). Villi absorb the products of digestion into the bloodstream.

THE SMALL INTESTINE

duodenum

jejunum

ileum

THE LARGE INTESTINE

• When the small intestine has completed its tasks, the ileocecal valve opens and releases the contents into the large intestine.

• This tube is 2 inches in diameter, but shorter than the small intestine (about 5 feet long).

• It is composed of the cecum, appendix, ascending, transverse, and descending, and sigmoid colons; rectum, and anus.

CECUM AND APPENDIX

LARGE INTESTINE

THE LARGE INTESTINE, cont.

• The rest of the digestion is completed here in the terminal portion of the digestive tract.

• The large intestine has 4 major functions:

1. completion of the absorption

2. manufacture of certain vitamins

3. formation of feces

4. expulsion of feces

• The cecum is a blind pouch (2-3 inches long).• A worm-like tubular structure dangles from the

cecum. This is the appendix. There is no known function for this structure.

• The open end of the cecum connects to the ascending colon, then proceeds to become the different sections of the large intestine.

• Bacteria change the chyme into fecal material by releasing the remaining nutrients. The bacteria are also responsible for the synthesis of vitamin K, and the production of some of the B-complex vitamins.

THE ACCESSORY ORGANS

• Teeth and gums (Books differ on this)• Tongue• Liver • Gallbladder• Pancreas• Salivary glands (parotid, submandibular,

and sublingual). There are 3 pairs of these glands. They secrete saliva, which is 99% water with enzymes and mucus.

Overview of Anatomy and Physiology of the Accessory

Organs• Accessory organs of digestion: These organs

are not considered part of the digestive tract, but rather aid in the process.– Organs and their functions

• Liver: produces bile; stores it in the gallbladder• Pancreas: produces pancreatic juice• Salivary Glands: begin digestion of carbohydrates

• Regulation of food intake– Hypothalamus

• One center stimulates eating and another signals to stop eating

SALIVARY GLANDS

• Once food enters the mouth, the glands secrete enough saliva to lubricate and dissolve the food, and to begin the chemical process of digestion.

• PTYALIN (or amylase) is the major salivary enzyme. It is responsible for the metabolism of carbohydrates.

• Another enzyme, lysozyme, destroys bacteria, which protects the teeth from decay, and protects the mucous membrane from infection.

• The salivary glands continue to secrete saliva even after the food has been ingested. It cleanses the mouth.

SALIVARY GLANDS

THE LIVER

• The liver is the largest glandular organ in the body. In the adult, it weighs 3 lbs. It covers most of the right upper quadrant and extends into the left epigastrium. It has 2 lobes. Approximately 1500 mL of blood is delivered to the liver every minute by the portal vein and the hepatic artery.

• The cells of the liver produce a product called bile, a yellow-brown liquid. Bile is needed for the metabolism of fats. The liver releases 500-1000 mL of bile per day. Bile travels to the gallbladder through hepatic ducts.

THE LIVER

GALLBLADDER

• The gallbladder is a sac (3-4 inches long) located on the right inferior surface of the liver. Here bile is stored until needed for fat digestion.

THE LIVER AND GALLBLADDER, cont.

• Besides producing bile, the liver has many other functions: 1. Managing blood coagulation

2. Manufacturing cholesterol 3. Filtering out old RBCs and bacteria 4. Manufacturing albumin to maintain normal blood

volume 5. Detoxifying poisons (alcohol, nicotine, drugs, etc.), 6 Stores glycogen

7. Breaking down nitrogenous waste from protein metabolism to urea which the kidneys can excrete as waste from the body

8. Converting ammonia to urea

THE PANCREAS

• This is an elongated gland that lies posterior to the stomach.

• It is involved in both endocrine and exocrine duties.

• The pancreas produces 1000-1500mL of pancreatic juices to help in digestion.

THE PANCREAS, cont.

• The pancreatic juices contain the digestive enzymes protease (trypsin), lipase (steapsin), and amylase (amylopsin), which are important because of their ability to digest the three major components of chyme: fats, protein, and carbohydrates.

• These enzymes are transported through an excretory duct to the duodenum.

• The pancreatic duct connects to the common bile duct from the liver and gallbladder, and empties through a small orifice in the duodenum called the major duodenal papilla or papilla of Vater.

• The pancreas contains an alkaline substance, sodium bicarbonate, that has the ability to neutralize HCl acid in the gastric juices that enter the small intestine from the stomach.

THE PAPILLA OF VATER

THE REGULATION OF FOOD INTAKE

• The hypothalamus (portion of the brain) contains two centers that have an effect on eating.

• One center stimulates the individual to eat; the other center signals the individual to stop.

• These centers work together to balance eating habits.

• There are other factors that affect eating: distention decreases appetite, lifestyle habits, emotions, and genetics.

EATING FACTORS