PHYSIOLOGY OF THE DIGESTIVE

SYSTEMRhenier S. Ilado, RN

SPECIALIZED REGIONS WHERE DIGESTION TAKES PLACE

MOUTH

PHARYNX

ESOPHAGUS

STOMACHSMALL

INTESTINELARGE

INTESTINEANUS

DIGESTIVE SYSTEM WITH OTHER ASSISTING ORGANS

The human digestive tract is a long, coiled, muscular tube that stretches from the mouth to the anus.

From mouth to the anus, the human food tube or the digestive tract is about nine meters long.

THE HUMAN DIGESTIVE TRACT

9meters

THE HUMAN DIGESTIVE TRACT MEASUREMENT

SPECIALIZED REGIONS WHERE DIGESTION TAKES PLACE

1. Food processing begins in the mouth.

2. The bite food is then swallowed and is moved through the pharynx into the esophagus.3. Then, food is mechanically and enzymatically digested in the stomach.

4. Most enzymatic digestion takes place in the small intestine.5. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

WHERE DIGESTION TAKES PLACE WITH ASSISTING ORGANS

1. Food processing begins in the mouth.

2. The bite food is then swallowed and is moved through the pharynx into the esophagus.

3. Then, food is mechanically and enzymatically digested in the stomach.

4. The liver secretes bile.

5. The pancreas secretes digestive enzymes.

WHERE DIGESTION TAKES PLACE WITH ASSISTING ORGANS

6. Most enzymatic digestion takes place in the small intestine.

7. Nutrients are then digested as they move the digestive tract.

8. Nerves and hormones regulate digestion.

9. Absorption takes place mainly through the villi of the small intestine.10. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

MOUTH Digestion starts in the mouth Mechanical Digestion occurs through

mastication (chewing) Chemical digestion occurs through the action

of salivary amylase which breakdown starches to maltose

Deglutition (swallowing) occurs, once the food is broken down into small pieces and well mixed with saliva (food bolus)

Tongue mixes food with saliva and roll it to be come BOLUS

SALIVA contains – water, mucus and salivary enzyme (amylase)

MOUTH

MECHANICAL DIGESTION starts in the mouth (Mastication) where four kinds of teeth tear the food into pieces:

Four kinds of teeth: 1. INCISORS – thin-edged for

cutting food2. CANINES – are pointed

used for tearing3. MOLARS & PREMOLARS –

specialized for crushing and grinding

MECHANICAL PHASE OF DIGESTION IN THE MOUTH

THE HUMAN TEETH / MAN’S DENTAL SET

Our mouth has salivary glands that secrete saliva. This saliva contains the enzyme called salivary amylase.

This salivary amylase and the enzyme called maltase (catalyzes maltose into glucose) enables the chemical digestion of the mouth to occur.

CHEMICAL DIGESTION IN THE MOUTH

THE HUMAN SALIVARY GLANDS

These salivary glands secrete salivary amylase.

CARBOHYDRATES

I. STARCH Maltose

II. MALTOSEGlucose

SALIVARY AMYLASE

(a double sugar)

MALTASE

(a simple sugar)

HOW MOUTH’S CHEMICAL DIGESTION IS DONE?

EsophagusApproximately 10” longFunctions:• Serve as a passage for food

bolus from mouth to stomach• Moves food from the throat to

the stomach using muscle movement called peristalsis

• Contain sphincter which prevents reflux of gastric contents back to esophagus

MECHANICAL PHASE: THE PROCESS OF PERISTALSIS

STOMACH• J-shaped muscular bag that

stores the food you eat, breaks it down into tiny pieces.

• Mixes food with digestive juices that contain enzymes to break down proteins and lipids.

• Acid in the stomach kills bacteria.

• Food found in the stomach is called chyme.

THE STRUCTURE OF THE STOMACH

FUNCTIONS OF THE STOMACH Mechanical Digestion Storage, mixing and

liquefaction of bolus of food into semisolid mixture called chyme

The rugae liquefy solid particles through grinding motion

FUNCTIONS OF THE STOMACH Secretion 1,500 to 3,000 mls of gastric juice is

secreted by the glands in the gastric mucosa

Gastric juice is composed of mucus, HCL (hydrochloric acid), pepsinogen and water

Gastrin (a hormone) is secreted to stimulate gastric glands to produce gastric juice

FUNCTIONS OF THE STOMACH

Chemical digestion Digestion of protein starts

in the stomach through the action of PEPSIN, which chemically breaks protein into smaller molecules

FUNCTIONS OF THE STOMACH Protection The acid medium is

also responsible for the reduced activity of harmful bacteria that may have been taken in with food

Mucus-secreting glands in the stomach protects the stomach lining from acidity by producing mucus

FUNCTIONS OF THE STOMACH Controls passage of chyme into

duodenum Through peristaltic waves,

carbohydrates are emptied within 1 to 2 hours

Protein within 3-4 hours Fats within 4-6 hours

SMALL INTESTINE• 3 segments of the small

intestine are: DUODENUM, JEJUNUM, ILEUM

• Small intestines are roughly 6 meters long

FUNCTIONS OF SMALL INTESTINE Chemical digestions Final digestive process of chyme

is facilitated by secretion of enzymes from the PANCREAS

Pancreas secretes 3 enzymes: Pancreatic AMYLASE, LIPASE and TRYPSIN

AMYLASE completes digestion of carbohydrates

LIPASE complete digestion of fats

TRYPSIN complete digestion of protein

Fats are emulsified by BILE secreted from the GALLBLADDER

FUNCTIONS OF SMALL INTESTINE Nutrient absorption Lining of intestine walls has

finger-like projections called villi, responsible for absorption of nutrients

The villi are covered in microvilli which further increases surface area for absorption.

SMALL INTESTINE

• The majority of digestive process is completed in the duodenum.

• This section also contains an opening from the bile duct and pancreatic duct through which bile and pancreatic enzymes enter the small intestine

Large intestine• Approximately 1.5 meters (5-

6 feet) long• Divided into the following

parts: Cecum Colon Rectum Anus

• Colon is divided into: Ascending Transverse Descending sigmoid

FUNCTIONS OF LARGE INTESTINE Absorption of water, sodium and

minerals Normal flora in the colon synthesize

vitamin vitamins e.g. Vit. K, B1, B2 Formation of feces (undigested and

unabsorbed substances from the small intestine)

Defecation – act of expelling of feces through peristalsis

Accessory Organs

• Salivary gland• Liver• gall bladder• pancreas

Salivary glands – produces saliva

parotid glands

submaxillary

sublingual glands

Liver

The liver is a large accessory organ of the digestive system that is constantly producing a fluid known as bile.

Bile is stored in the gall bladder until it is needed in the small intestine.

Liver and Gall Bladder

Gall bladder stores and concentrate BILE produced by the liver

The presence of lipids in the small intestine trigger the release of the hormone cholecystokinin (CCK) which triggers the release of bile from the gall bladder.

Bile contains bile salts that emulsifies fats which means it breaks them into smaller droplets so they can be digested

Pancreas

The pancreas is an accessory organ of the digestive system.

It releases enzymes (amylase, lipase, trypsin) to aid in digestion

Secretin will stimulate the pancreas to release a solution containing bicarbonate ion into the small intestine where it will neutralize the acidic chyme

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