Edison D. Ramos, RMT, MPHFaculty – College of Medical Technology

Manila Central University

OBJECTIVES:

1.List and describe the five basic activities of the digestive process2.Name the major and accessory organs of the digestive tract and their component anatomic parts3.Explain the major digestive enzymes and how they function4.Explain the function of liver5.Explain how absorption of nutrients occurs in the small intestine and how feces form in the large intestine6.Name and describe the functions of the organs of the digestive tract

INTRODUCTION

• Function: the break down food via hydrolysis into simpler substances or molecules that can be used by the body’s cell• Allows the body’s cell to convert food energy into high energy ATP molecules

Five Basic Activities:1.Ingestion2.Peristalsis3.Digestion4.Absorption5.Defecation or Elimination

Digestion: An Example of Hydrolysis

1.Complex carbohydrates + Amylase + water simple sugar2.Proteins + Proteases + water amino acids3.Fats + Lipases + water fatty acids and glycerol

General Organization

1.Gastro Intestinal Tract or Alimentary Canal – mouth to anus2.Accessory Structures – teeth, tongue, salivary gland, liver, gall bladder, pancreas

Digestive System

Structures

Accessory Organs Digestive TractDucts lead to

Liver, Gall Bladder

Secrete Bile

PancreasSecretes numerous enzymes, Na HCO3

Salivary Glands

Secrete Amylase

Oral cavity, Pharynx, Esophagus

Stomach

Lead to

Secretes acid and pepsinogen

Small Intestine Has numerous

secretions embedded in

intestinal mucosa

Large Intestine

Coats or Tunics of the Alimentary Canal

1.Tunica Mucosa – innermost lining of the canal and consists of a mucous membrane attached to a thin layer of visceral muscle2.Tunica Submucosa – consists of loose connective tissue that binds the tunica mucosa to the next layer3.Tunica Muscularis • Mouth, pharynx, and the first part of

esophagus consist of skeletal muscle that allows the voluntary act of swallowing

• The rest of the tract consist of smooth muscle4.Tunica Serosa – outermost layer, consist of serous membrane made up of connective and epithelial tissue. Also known as visceral peritoneum

THE MOUTH OR ORAL CAVITY

• Also called the Buccal Cavity• Its sides are formed by the cheeks, roof consists of the hard and soft palate and its floor is formed by the tongue• Function: taste, mechanical breakdown of food using the teeth and chemical digestion of carbohydrates using salivary enzyme amylase• Function of tongue: manipulation of food, taste and assistance is speech• Three pairs of salivary glands are the parotid, submandibular or submaxillary and the sublingual. Saliva lubricates the food, begins the digestion of complex carbohydrates and controls certain bacteria• Tooth is composed of crown, the neck or cervix and the root. Crown is covered with enamel. A tooth is made up of dentin

The Salivary Glands

• Saliva is 99.5% water, which provides a medium for dissolving foods. The remaining 0.5% consist of:

• Chloride – activates the salivary enzyme amylase• Amylase – initiates the breakdown of complex carbohydrates• Bicarbonate and phosphate – the buffer chemicals, keep the saliva at a slightly acidic pH of 6.35 – 6.85• Urea and uric acid – waste products• Mucin – forms mucus to lubricate food• Lysozyme – destroys bacteria

The Teeth

• Also known as DENTES• Breaks food by chewing (mastication)• 20 temporary of deciduous teeth that form in infants between the ages 6 mos. to 2 years• By the age of 13, 32 permanent teeth will develop to replace the deciduous • 8 front teeth – incisors – used to cut foods• 4 – canine teeth (cuspids) – used to tear food• Molar teeth – grind food• 8 premolars (biscuspid)• 12 molars (tricuspid)

THE PHARYNX

• Common passageway for food and air thus it functions as part of both the digestive and respiratory systems• Divided into nasopharynx, oropharynx and the laryngopharynx• Its function is to begin the process of swallowing or deglutition

THE ESOPHAGUS

• collapsible, muscular tube that is situated behind the trachea or windpipe• Function: to secrete mucus and transport food to the stomach through an opening in the diaphragm called the esophageal hiatus• Peristalsis, caused by smooth muscle contractions, pushes the food bolus into the stomach through the lower esophageal sphincter

THE STOMACH

• Enlargement of the GIT• Main function is to begin the chemical breakdown of proteins through the enzyme pepsin. It also breaks down food mechanically by churning its contents. It absorbs some water, salt, alcohol and certain drugs like aspirin• Parts of the stomach:• Cardia – surrounds the gastroesophageal sphincter• Fundus – rounded portion above and to the left of cardia• Body – large cenral portion below the fundus• Pylorus (antrum) – narrow inferior region that connects with the duodenum of small intestine via the pyloric sphincter

• Rugae – large folds in the stomach when it is empty

• Contains many pits or gastric glands that have three kinds of secreting cells:• Zymogenic or chief cells – secrete gastrin,

principal gastric enzyme pepsinogen• Parietal cell – secrete HCl which activates the

pepsinogen to become pepsin (enzyme that begins to break down proteins)

• Mucuos cells – secrete mucus

THE PANCREAS

• Soft, oblong gland about 6 inches long and 1 inch thick• Divided into:• Head – part that is closest to the duodenun• Body – main part• Tail

• Functions:• The acini secrete enzyme that continue the digestion of food in the small intestine• Alpha and beta cells secrete hormones glucagon and insulin which regulate and control blood sugar levels

THE LIVER

• One of the largest organ, weighs approximately 4 pounds• Lobules – functional unit of liver• 6 major functions:• Manufactures anticoagulant heparin and plasma protein (prothrombin and thrombin)• Kupffer cells of the liver phagocytose certain bacteria and old cells• Liver contains various enzymes• Liver stores excess glucose and other monosaccharides• Liver stores glycogen, copper, and iron as well as vitamin A,D, E, K• Liver produces bile salts that break down fats then it is sent to the duodenum for emulsification and absorption of fats

THE GALLBLADDER

• Pear-shaped sac about 3-4 inches long located in a depression of the surface of the liver• Function: store and concentrate the bile produce by the liver lobules until it is needed in the small intestine• The bile enters the duodenum through the common bile duct

THE SMALL INTESTINE

• It is where the major portion of absorption and digestion happens• Approximately 21 feet in length and 1 inch in diameter• Three portions:• Duodenum – first part, shortest part. Originates in pyloric sphincter• Jejunum – second portion about 8 feet long• Ileum – third part an measures 12 feet long. It joins the large intestine

• The intestinal glands or Crypts of Lieberkuhn secrete the intestinal digestive enzymes, the Brunner’s glands secrete an alkaline mucus• Chyme is the name of the digested content of the small intestine

THE LARGE INTESTINE

• Function: absorption of water, manufacturing and absorption of certain vitamins and formation and expulsion of feces• Approximately 5 feet in length and 2.5 inches in diameter• Also referred as the bowel• Four principal regions:• Cecum – pouch-like, first part• Colon – largest part• Ascending colon • Transverse colon• Descending colon• Sigmoid colon

• Rectum• Anal canal

• The opening of anal canal to the exterior is called the Anus. It is guarded by anal sphincter muscle (internal smooth muscle, external skeletal muscle)

• Absorption of water is an important function of large intestine.

• Bacteria in the colon manufacture three important vitamins: Vitamin K needed for clotting, Biotin needed for glucose metabolism and Vitamin B5 needed to make certain hormones and neurotransmitters