The cradle System

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If human cells could use the food eaten in the form, there would be no require for a digestive system. The digestive system alters the food right into a form that have the right to be used by the cells and also that permits the nutrient to acquire into the blood so they deserve to be transported transparent the body.

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The digestive system is composed of one lengthy tube and the guts that connect to it. The organs create digestive chemicals (enzymes and acids) that malfunction the nutrient into less complicated forms so that absorption v the intestinal wall and right into the blood stream deserve to occur.

Mechanical and also Chemical Digestion

There space two type of digestion: mechanical and also chemical. Mechanical digestion entails physically break the food into smaller pieces. Mechanical digestion begins in the mouth together the food is chewed. Chemical digestion requires breaking under the food into easier nutrients that deserve to be provided by the cells. Chemical digestion begins in the mouth once food mixes v saliva. Saliva has an enzyme (amylase) that starts the malfunction of carbohydrates. (An enzyme is a protein that have the right to catalyze details biochemical reactions).

The Digestive procedure


Food is chewed right into smaller pieces. Adults have 32 devoted teeth—teeth that have the right to grind, chew, and also tear different kinds of food. The tongue is an body organ consisting that skeletal muscles (voluntary muscles) that relocate the food roughly the mouth to enable for effective mechanical digestion. Salient glands beneath and in back of the tongue secrete the saliva that enables for simpler swallowing of food and the start of chemistry digestion.


Swallowing pressures the chewed food v a tubular enntrance gate (pharynx) come the esophagus (food tube). Together food is swallowed a flap-like valve, the epiglottis, closes end the trachea (windpipe) to protect against food beginning the windpipe and causing choking.


The stomach connects the pharynx v the stomach. Contractions of the esophagus press the food with a sphincter (a ring of smooth muscle the closes turn off an opening in the body) and into the stomach.

NOTE: The digestive system moves food along by means of peristalsis, a wavelike convulsion of smooth (involuntary) muscle.

Other than the chemistry digestion of carbohydrate in the mouth, every digestion come this point has been mechanical.




The stomach is a muscular and stretchable sac v three crucial functions:

1) that mixes and stores food until it deserve to be additional digested.

2) it secretes chemicals that assist break the food into more digestible forms.

3) that controls the passage of food into the small intestine.

The stomach starts chemical digestion that protein. Secretions from the stomach lining consist of of about two liters that hydrochloric mountain (HCl), pepsin, and other fluids that make up gastric fluids every day. The liquid is incredibly acidic and also it helps death bacteria and other pathogens that may have actually been ingested.

The thick mucus also produced through the stomach lining commonly keeps the acids from damaging the lining. If not enough mucus is produced or if too much acid is produced, peptic ulcers form. Heredity, stress, smoking, and also excessive alcohol intake have the right to make the ulcers worse. The condition can worsen and bleeding ulcers deserve to result.

Food remains in the stomach for about 3-4 hours and also moves through one more sphincter muscle to pass right into the tiny intestine.

Small intestine

Nearly 7 meters in length, the small intestine is folded and curled roughly a little area in the ab cavity. The inside surfaces of the intestine room covered through projections called villi. this finger-like structures room covered in smaller projections referred to as microvilli and also work to absorb food molecules that have been broken down by the processes of chemical digestion.

The tiny intestine has actually three distinctive parts: the duodenum, the jejunum, and the ileum. Each day, around 9 liters of liquid enters the duodenum. Most chemical cradle takes location in the duodenum by chemistry secreted through the liver, kidnize and tiny intestine. The other two sections of the little intestine, the jejunum and the ileum, absorb food molecule by means of the villi directly into the blood stream.

Large intestine

The big intestine receive the material “left-over” from chemistry digestion that is usually nutrient free. Only water, cellulose, and undigestible products are left. The main job that the big intestine is to eliminate water indigenous the undigested material. Water is easily removed native the material through villi and also returns come the blood stream.


The last part of the digestive tract is the rectum, a “holding area” because that the undigested material. Waste pipeline the human body from this area.

Accessory Organs


The liver is a big organ situated just above the stomach. The liver produce bile which help digest lipids. Bile is save in the gallbladder and also flows indigenous the gallbladder to the duodenum whereby it helps digest fats.

The photo at the left mirrors a person liver.

Gall bladder

The bile bladder is a small, greenish organ located simply under the liver. It stores bile developed by the liver until it is secreted directly into the an initial section of the little intestine.


The pancreas has actually three important functions that aid the cradle system change food right into a type that deserve to be supplied by the cells.

1) that produces enzymes which help failure proteins, lipids, and also carbohydrates.

2) the produces the hormone, insulin, i m sorry helps regulate blood glucose levels.

3) it produces sodium bicarbonate which help to neutralize stomach acids.

Checking for Understanding

1. What is the function of the cradle system?

To readjust ingested food right into a form that deserve to be provided by the cells, to acquire the nutrients right into the blood stream, come reabsorb water, and also to eliminate wastes.

2. What is the function of the complying with parts/organs that the cradle system?

a. mouthhouses teeth, salient glands and also tongue because that mechanical and also chemical digestion

b. teethchews, grinds, and tears food right into smaller pieces

c. esophagusfood tube; leads from the pharynx come the stomach

d. stomach

churns food come mix v gastric enzymes and acid to proceed mechanical and also chemical digestion

e. sphincter

a ring that muscle approximately an opening or tube

f. duodenumthe an initial section the the small intestine; significant chemical digestion of carbohydrates, lipids, and also protein occurs here

g. large intestinedigestive body organ responsible because that the reabsorption the water

h. rectum

holds hard wastes until elimination from the body

i. pancreasdigestive gland i m sorry secretes enzymes because that digestion the carbohydrates, fats, and also proteins; secretes insulin i beg your pardon regulates blood sugar

j. liver

digestive body organ which secretes bile

k. gall bladder

stores bile

3. What is the difference in between mechanical and also chemical digestion?

Mechanical cradle breaks down food into little pieces. Chemistry digestion chemically transforms the food right into a form that deserve to be provided by the cells.

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4. Some medical problems make it crucial to remove sections of the large intestine. What after-effects could this removal have on the digestive process?

The large intestine removes water indigenous the undigested material. The fecalmaterial left ~ nutrient absorption in the tiny intestine would have a high liquidcontent.