Digestion
What is the digestive process?
(1) Mouth: Food is chewed into smaller pieces. Adults have 32 specialized teeth - teeth that can grind, chew, and tear different kinds of food. The tongue is an organ consisting of skeletal muscles (voluntary muscles) that move the food around the mouth to allow for efficient mechanical digestion. Salivary glands beneath and in back of the tongue secrete the saliva that allows for easier swallowing of food and the beginning of chemical digestion
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(2) Pharynx: Swallowing forces the chewed food through a tubular entrance (pharynx) to the esophagus (food tube). As food is swallowed a flap-like valve, the epiglottis, closes over the trachea (windpipe) to prevent food entering the windpipe and causing choking.
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(3) Esophagus: the esophagus connects the pharynx with the stomach. Contractions of the esophagus push the food through a sphincter (a ring of smooth muscle that closes off an opening in the body) and into the stomach. NOTE: THE DIGESTIVE SYSTEM MOVES FOOD ALONG BY WAY OF PERISTALSIS, A WAVELIKE CONTRACTION OF SMOOTH (INVOLUNTARY) MUSCLE.
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(4) The stomach is a muscular and stretchable sac with three important functions: (a) it mixes and stores food until it can be further digested (b) it secretes chemicals that help break the food into more digestible forms and (c) it controls the passage of food into the small intestine. The stomach starts chemical digestion of protein. Secretions from the stomach lining consist of about two liters of hydrochloric acid (HCI), pepsin, and other fluids that make up gastric fluids each day. The fluid is extremely acidic and it helps kill bacteria and other pathogens that may have been ingested. Food stays in the stomach for approximately 3-4 hours and moves through another sphincter muscle to pass int othe small intestine
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(5) Small Intestine: Nearly 7 meters in length, the small intestine is folded and curled around a small area in the abdominal cavity. The inside surfaces of the intestine are covered with projections called villi. These finger-like structures are covered in smaller projections called microvillli and work to absorb food molecules that have been broken down by the processes of chemical digestion.
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(6) Large Intestine: The large intestine receives the material "left-over" from chemical digestion that is basically nutrient free. Only water, cellulose, and undigestible materials are left. The main job of the large intestine is to remove water from the undigested material. Water is quickly removed form the material through the villi and returns to the blood stream.
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(7) Rectum: the last part of the digestive tract is the rectum, a "holding area" for the undigested material. Waste leaves the body from this area.
6 Basic nutrients
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Why Chew food?
1. Increase surface area (larger area, easier to dissolve 2. Mix with saliva 3. So it's easier to swallow
What is the function of the following parts/organs of the digestive system?
1. mouth - houses teeth, salivary glands and tongue for mechanical and chemical digestion 2. teeth - chews, grinds, and tears food into smaller pieces 3. esophagus - food tube, leads form the pharynx to the stomach 4. stomach - churns food to mix with gastric enzymes and acid to continue mechanical and chemical digestion 5. sphincter - a ring of muscle around an opening or tube 6. duodenum - the first section of the small intestine; major chemical digestion of carbohydrates, lipids, and proteins occurs here 7. large intestine - digestive organ responsible for the reabsorption of water 8. rectum - hold solid wastes until elimination from the body 9. pancreas - digestive gland which secretes enzymes for digestion of carbohydrates, fats, and proteins; secretes insulin which regulates blood sugar 10. liver - digestive organ which secretes bile 11. gall bladder - stores bile
List 4 functions of the liver as they relate to digestion and nutrition
1. produces bile 2. glycose storage 3. plasma protein synthesis 4. blood detoxification
small intestine
10" duodenum
How many salivary glands
6 glands that produce 1500ml per day
Bile
Also reduces the acidity of food entering from the highly acidic stomach. THIS IS IMPORTANT BECAUSE DIGESTIVE ENZYMES THAT WORK IN THE DUODENUM NEED A NEUTRAL ENVIRONMENT.
villi
Because there are so many villi, they greatly increase the surface area for absorption. In fact, they make the inner surface of the small intestine as large as a tennis court.
In the duodenum
Bile breaks up large globules of lipids into smaller globules that are easier for enzymes to break down.
trace the route of bile, noting where it is produced, where it is stored, and how it functions in digestion
Bile is produced in the liver where it is then stored in the gall bladder. Bile emulsifies fat in the small intestine
cholecystokinin
CCK - hormone source: duodenum stimulus: chyme target: pancreas and gall bladder action: pancreas releases pancriatic juice. gall bladder releases bile
Chemical digestion
Changes the substance into an absorbable form
Mechanical digestion
Chewing and Churning
What makes up the digestive system?
Consists of one long tube and the organs that attach to it. The organs produce digestive chemicals (enzymes and acids) that break down the nutrients into simpler forms so that absorption through the intestinal wall and into the blood stream can occur.
Pancreas
Contributes to the neutral environment by secreting bicarbonate, a basis substance that neutralizes acid
gastric juice (kills most bacteria)
HCI - Hydrochloric acid (loosens fibers) Alkaline Mucus (lines stomach, protects it) Pepsinogen - enzyme precursor
Need for a digestive system
If human cells could use the food eaten in that form, there would be no need for a digestive system.
small intestine
Is the site of most chemical digestion and virtually all absorption.
Why a digestive system?
It changes the food into a form that can be used by the cells and that enables the nutrients to get into the blood so they can be transported throughout the body
make up of small intestine
It is made up of three parts: duodenum, jejunum, and ileum
Accessory Organs
Liver, Gall Bladder, Pancreas, Salivary Glands
explain how the structure of the small intestine is related to the function of absorption
MILAN'S ANSWER: if the food is smaller, the small intestine does not have to expand, allowing for quicker digestion and absorption of nutrients, If the food is larger,it has to expand, making the digestion process longer. ANSWER FROM ABOVE: Nearly 7 meters in length, the small intestine is folded and curled around a small area in the abdominal cavity. The inside surfaces of the intestine are covered with projections called villi. These finger-like structures are covered in smaller projections called microvillli and work to absorb food molecules that have been broken down by the processes of chemical digestion.
What are the two kinds of digestion?
Mechanical and Chemical
compare the process of chemical digestion with the process of mechanical digestion and list the organs involved in each
Mechanical: Chewing and Churning/Mouth and Stomach Digestion: Changes the substance into an absorbable form/Stomach, salivary glands, small intestine
Villi (singular: villus)
Millions of microscopic, fingerlike projections that cover the mucous membrane lining of the jejunum
Duodenum
Most chemical digestion takes place here and many digestive enzymes are active in the duodenum. Some are produced by the duodenum itself and others are produced by the pancreas and secreted into the duodenum
Jejunum
Most nutrients are absorbed into the blood in the jejunum.
Saliva
Mostly water, but also contains mucus and salivary amylase which begins starch digestion
name one structure involved in the mechanical phase of digestion and explain its function in mechanical digestion
Mouth (chewing) - it increase the foods surface area so it's easier to swallow and digest
Gastrointestinal Tract (GI)
Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anus
what type of digestion occur up through the esophagus?
Other than the chemical digestion of carbohydrates in the mouth, all digestion to through the step of the esophagus has been mechanical.
Liver
Produces a fluid called bile, which is secreted into the duodenum.
Jejunum
The second part of the small intestine
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The thick mucus also produced by the stomach lining usually keeps the acids from damaging the lining. If not enough mucus is produced or it too much acid is produced, peptic ulcers form. Heredity, stress, smoking, and excessive alcohol intake can make the ulcers worse. The condition can worsen and bleeding ulcers can result.
Ileum
The third part of the small intestine. A few remaining nutrients are absorbed here. Like the jejunum, the inner surface of the ileum is covered with villi that increase the surface area for absorption.
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Three parts of the small intestine: duodenum, jejunum, ileum. Each day, about 9 liters of fluid enters the duodenum. Most chemical digestion takes place in the duodenum by chemicals secreted by the liver, pancreas, and small intestine. The other two sections of the small intestine, the jejunum and the ileum, absorb food molecules by way of the villli directly int other blood stream.
Which of the 6 basic nutrients might a person need to restrict after an operation to remove the gallbladder? Explain
You need to restrict lipids as the bile works on fats which is stored in the gall bladder until secretion
small intestine
a narrow tube about 7 meters (23 ft) long in adults.
Enzyme
a protein that can catalyze certain biochemical reactions
gall bladder
a sac-like organ that stores and concentrates bile and then secretes it into the small intestine
Liver
an organ of both digestion and excretion
gastric pits
are the openings to the gastric glans which produce gastric juices
stomach
both mechanical and chemical digestion
pharynx
common passageway for both air and food
villi
contain may capillaries, and nutrients pass from the villi into the bloodstream through the capillaries.
Enzyme: Maltase
digest carbohydrates and made in duodenum
Enzyme: Amylase
digest carbohydrates and made in pancreas
Enzyme: Lipase
digest lipids and made in duodenum
Enzyme: Lipase
digest lipids and made in pancreas
Enzyme: Peptidase
digest proteins and made in duodenum
Enzyme: Trypsin
digest proteins and made in pancreas
Amylase
enzyme that begins the breakdown of carbohydrates.
Need to know for the stomach
esophagus goes into stomach. Stomach has mucous membrane and is made up of layers of muscle. Exiting the stomach is the pylorus sphincter then goes to the small intestine (first section is called the duodenum)
secretin
hormone (hormones travel in the blood) source: outside wall of the small intestine stimulus: chyme target: pancreas and liver action: pancreas releases bicarbonate ions (sodium bicarbonate) and liver releases bile (alkaline)
Chemical digestion
involves breaking down the food into simpler nutrients that can be used by the cells. Chemical digestion begins in the mouth when food mixes with saliva. Saliva contains an enzyme (amylase) that begins the breakdown of carbohydrates.
Mechanical digestion
involves physically breaking the food into smaller pieces. Mechanical digestion begins in the mouth as the food is chewed.
bile
is an alkaline
Esophagus
is connected to the stomach.
Bolus
lump of chewed (domesticated) food
acidic scale
neutral is a 7, acidic below 7 (to 0) and base above 7 (to 14)
esophagus
smooth muscle (involuntary) - peristalsis
Bile
some bile also goes into the gall blader
Pepsin
source: gastric glands stimulus: food in stomach target: proteins action: begins to break down proteins
Salivary amylase
source: salivary glands Stimulus: food in mouth or thought of food target: carbohydrates (starch) actions: begins carbohydrates digestion
Chyme
stomach contents after 2-4 hours
Duodenum
the first and shortest part of the small intestine.
Gall bladder
the gall bladder is a small, greenish organ located just under the liver. It stores bile produce by the liver until is it secreted directly into the first section of the small intestine
Some medical conditions make it necessary to remove portions of the large intestines. What consequences could this removal have on the digestive process?
the large intestine removes water for the undigested material. The fecal material left after nutrient absorption in the small intestine would have a high liquid content
Liver
the liver is a large organ located just above the stomach. The liver produces bile which helps digest lipids. Bile is stored in the gallbladder and flows from the gallbladder to the duodenum where it helps digest fats.
Pancreas
the pancreas has three improtant functions that help the digestive system change food into a form that can be used by the cells 1. it produces enzymes which help breakdown proteins, lipids, and carbohydrates 2. it produces the hormone, insulin, which helps regulate blood glucose levels 3. it produces sodium bicarbonate which helps to neutralize stomach acids
cardiac sphincter
the valve between the esophagus and the stomach. It keeps the stomach contents from leaking back up into the esophagus
Internal lining of the stomach
there is a mucus membrane composed of epithelial cells. The membrane is dotted with thousands of small openings called gastric pits.
what is the function of the digestive system?
to change ingested food into a form that can be used by the cells, to get the nutrients into the blood stream, to reabsorb water, and to eliminate waste
Pyloric sphincter
valve that allows food to enter the small intestine