DIGESTIVE SYSTEM

a. mouthb. Larynxc. esophagusd. stomache. Small intestinef. Large intestineg. rectumh. anusi. Saliva glandsj. liverk. gallbladderl. pancreas

Digestive System■the organs and glands in the body that are

responsible for digestion.■Involve the breakdown of foods into simpler

nutrients to be absorbed by our body.■Responsible for the survival of the human

beings and animals.

TWO TYPES OF DIGESTIVE SYSTEM■ INCOMPLETE DIGESTIVE SYSTEM – common among

invertebrates, there is only a single opening for the ingestion of food.

(an anus is absent)

■ COMPLETE DIGESTIVE SYSTEM – common among nematodes, annelids, mollusks, echinoderms, and vertebrates, this type has digestive

tubes with two openings. (a mouth and an anus)

FOUR MAJOR FUNCTION OF DIGESTIVE SYSTEM1. Ingestion of food

- the intake of foods into the body.2. Digestion of food

- the process of mechanical and chemical breakdown where by

large food molecules are broken down into soluble and diffusible

molecules that can be absorbed into the body cell.

3. Absorption of nutrients- it is the process whereby digested food materials

are taken into the body cells and are converted into new protoplasm or used to provide energy.4. Eliminates of waste materials

- passing of digested materials out of the digestive tract.

Digestion of food follows two distinct processes;Physical or Mechanical digestion

-involves the breaking up of food into small pieces/particles, pushing the food down the food tube, and mixing with its digestive juices.Chemical Digestion

-is the breakdown of the complex molecules, such as proteins, starch, fats contained in foods into soluble molecules by the action of digestive enzymes.

HOW DIGESTION IS DONE?

It start from….

■ The intake of food starts from our MOUTH, which leads to our mouth cavity.

■ 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 food.2. CANINES – are pointed used for tearing.3. MOLARS & PREMOLARS – specialized for crushing

and grinding.

MECHANICAL PHASE OF DIGESTION IN THE MOUTH

THE HUMAN TEETH / MAN’S DENTAL SET

■Mucin- helps to soften the food, while chewing it helps to break down the foods into smaller pieces.

■Saliva also contains a chemical substance called ptyalin ( also called salivary amylase), the enzyme that chemically digest cooked starch into a disaccharide maltose.

What happens after you finished chewing the food?

■The bite food is then swallowed and is moved through the pharynx into the esophagus.Pharynx- common passage for food and air.- it is the part of the gut which leads from the mouth to the esophagus and to the trachea by way of the larynx or voice box.- the larynx bears a slitlike opening called glottis.- epiglottis a piece of flaplike cartilage, covers the larynx.

Esophagus- also called gullet.- a narrow muscular tube.- comes from the Greek word

meaning “to carry what is eaten”.- two layers of smooth muscles

cause rhythmic, wavelike contractions of the wall of the gut.This movements known as peristalsis.

MECHANICAL PHASE: THE PROCESS OF PERISTALSIS

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

STOMACH- J shaped organ, it lies beneath the diaphragm and partially covered by the liver.

- Gastric Juice is a dilute solution of hydrochloric acid and the enzyme pepsin, an active enzyme secreted by the chief cell of the gastric glands.

-The stomach secretes millions of gastric glands.■ THE PARIETAL CELLS

– in the gastric glands secrete hydrochloric acid and intrinsic factor, a substance needed for adequate absorption of vitamin B12.

■ THE CHIEF CELLS– secrete pepsinogen (an inactive enzyme precursor). When

pepsinogen comes in contact with the acidic gastric juice, it becomes pepsin (the main digestive enzyme of the stomach).

- pepsin breaks some complex proteins even further into simpler proteins.

■ The stomach joins the small intestine, through a muscular to valve called the pyloric sphincter.

■ After mixing the food inside of the stomach and then it became soft, watery substance forming chyme. This now ready to move slowly to the next part, which is the small intestine.

■ Digestion is completed in the small intestine and nutrients are absorbed through its wall.

■ The small intestine is about 5 to 6 meters (about 17ft.) in length and has three regions.

1. Duodenum- the U shape2. Jejunum3. Ileum- the much coiled

- Intestinal juice helps break down food arriving from your stomach. This juice does not work alone, it is helped by the juices that are produces by two organs which are the liver and pancreas.

How absorption of food nutrients is done?

■Protein are broken down individual amino acids.

■Carbohydrate are broken down into simpler sugar.

■Fats are broken down into fatty acids and glycerol.

■It’s inner lining is covered with a million of tiny fingerlike structures called villi (villus), projecting into the intestinal cavity.

Some Digestive Enzymes

Digestive Juice Source Digestive Enzymes Works on Change it to

Saliva Salivary glandsPtyalin (salivary amylase) and mucin

Starch Complex sugar

Gastric juice Gastric glands in the stomach pepsin proteins Simpler proteins

Pancreatic juice Pancreas

Pancreatic amylase Starch Complex sugar

Trypsin Proteins Simpler proteinsLipase Fats Fatty acids and

glycerol

Intestinal juice Intestinal glands in small intestine

Lactase, maltase, sucrase Complex sugar Simple sugar

Peptidase Simpler proteins Amino acids

Lipase Fats Fatty acids and glycerol

THE THREE REGIONS OF THE SMALL INTESTINE

THE LAYERS OF THE SMALL INTESTINE (Labelled)

LIVER ■ the largest internal organ of the body and also one of the most complex

organs which lies in the upper right abdomen just under the diaphragm.■ Its dark and color red.■ the liver secretes BILE.

BILE – greenish-yellow fluid secreted by the liver which emulsifies fats-bile is temporarily stored in gallbladder, greenish-yellow bag.- has three attached blood vessels1. hepatic portal vein2. hepatic vein3. hepatic artery

■ Other important functions of the liver.– Protein synthesis– Iron storage– Detoxification– Heat production

Pancreas- Is a soft triangular gland lying between the small intestine

and the stomach.- It is connected to the duodenum of the small intestine by

means of pancreatic duct. - It produces pancreatic juices, which is a mixture of

digestive enzymes.- This enzymes move to small intestine at the same time the

bile does and help to break down proteins, starches, and fats.

- The enzymes secreted by the pancreas are called TRYPSIN and CHYMOTRYPSIN.

- It also secretes INSULIN, which plays an important role in the control of the blood sugar level in the body and utilization of carbohydrates.

Absorption in the large intestine.■ Shorter but much broader than the small intestine.■ At the junction between the small intestine and the ascending colon

(part of the large intestine) is a small sac, called the caecum and the blindly ending appendix.

■ Is about 1.5 meters long consist of the following:1. Caecum and the appendix2. Ascending colon running upwards along the right side of the

abdominal cavity.3. Horizontal transverse colon4. Descending colon which runs downward to join the rectum5. Rectum (a short muscular tube)

FUNCTIONS OF LARGE INTESTINE;- to absorb water and mineral salt.

■ Most of the water that is contained in undigested food is absorbed.■ Helpful bacteria resides at the large intestine make certain vitamins,

such as vitamin K and B vitamins, that also needed by our body.

Elimination of waste materials;■Materials that are not absorbed in the large intestine is

called feces.– Made up of dead bacteria and some fat and protein.Undigested food roughage, dried out digested juices, mucus, and discarded intestinal cells, is stored temporarily in the rectum.When the rectum contracts, the feces is expelled through the opening called anus.The process of removing undigested matter from the body is called egestion, defecation, or vowel movement.

How long food stays in the digestive organsStructure Primary Function Time food stays in

the structure

Mouth Mechanical and chemical digestion 5-30 seconds

Esophagus Transport of food after swallowing 7- 10 seconds

StomachMechanical and chemical digestion of food

2-24 hours

Small intestineMechanical and chemical digestion of food

3-5 hours

Large intestine Water absorption 18 hours- 2 days