Download Digestion after the Stomach

Digestion after the Stomach
Small intestine:








Most digestion and nutrient absorption occurs in the ______________________________.
The small intestine is a long tube that is only about __________ in diameter and approximately
7 m long. Whereas the large intestine is around 7.6cm in diameter and ___________ in length.
Lipids, carbohydrates, and remaining proteins are digested in the small intestine.
It is made up of 3 sections:
o Duodenum, jejunum, and the ileum
_________________: the first 25 to 30 cm. where most enzymes are added and where digestion
in the small intestine begins.
_________________: digestion continues and some nutrients are absorbed.
_________________: where most nutrients are absorbed. Can be distinguished from the
jejunum based on shape and size of epithelial cells.
_________________: the inner surface of the small intestine is adapted to provide the
maximum amount of surface area for efficient nutrient absorption.
o Inner layer is folded into ridges and has many finger like projections called
_________________; singular villus.
o Each villus has even smaller, microscopic projections called ________________
o Each villus has a network of blood vessels called __________________
o All nutrients except digested__________, enter the blood stream through the capillaries
o Digested fats transfer through small vessels called ____________ and transported
through the________________ system
Chemical Digestion in the Small Intestine:





Chyme is slowly released into the small intestine at a pH of ___________.
Cholecytokinin (CCK): a hormone secreted by cells in the mucosa of the _________________
and is released into the blood stream.
 Signals the _____________to secrete substances to control pH and enzymes to
digest carbohydrates, lipids and proteins.
 Stimulates the release of _____________
 CCK signals the stomach to ______________digestion
PANCREAS: a long flat gland nestled between the stomach and the duodenum. It secretes
enzymes and hormones that are critical to the digestive process.
o ______________: excreted by the pancreas into the duodenum to break down
carbohydrates
o ______________: a hormone that controls glucose levels
o ______________: the pancreas also secretes these enzymes that break down fats.
Breaks down lipids into shorter chains and into individual fatty acid chains at the surface
of fat globules
o Trypsinogen-______________: the pancreas releases trypsinogen, which is the inactive
form of the protein digesting enzyme trypsin (further digests proteins broken down by
pepsin). Once in the duodenum, the enzyme called ______________ converts
trypsinogen into active trypsin.
Prosecretin-_________________:
o Prosecretin is secreted by the lining of the small intestine and is converted to secretin
when mixed with the acidic chyme.
o Secretin:_______________ form, which stimulates pancreatic (bicarbonate ions; HCO3-)
and bile secretions.
 The bicarbonate ions _______________ the hydrochloric acid to a pH of 9
 _____________ is inactivated in the basic pH
 Acts a digestive rate regulator and prevents more food from entering from the
stomach until digested
Carboxypeptidase and Erepsin: Both are made in the pancreas and erepsin is also made in cells
of the ileum. They are other protein digesting enzymes that help break down of small protein
chains into single amino acids
The Liver and Gall bladder – secrete into duodenum



The liver in its digestive functions is considered a gland because it produces and secretes
bile
o Bile ____________________ fats, breaking down large fat globules. This provides a
larger surface area for lipases to digest. This is physical digestion.
Bile is continuously made, but stored in the _________________. Fat entering the
duodenum stimulates the gall bladder to contract, squeeze.ing the bile through the bile
duct and into the duodenum
Blood passing through the capillaries of the intestines pass through the liver which also
filters toxins such as alcohol.
Absorption

_______________: the movement of materials across a cell membrane without any expenditure
of the cell’s energy
o
o
o

______________: the movement of molecules from an area of higher concentration to a
lower concentration ( move from the small intestines to capillaries, e.g. amino acids)
______________: the movement of water from an area of higher concentration to a
lower concentration across a selectively permeable membrane (some water content in
food is absorbed by osmosis in the stomach and small intestine)
______________: the diffusion of molecules across a cell membrane via a transport
protein. Each protein has a unique size and shape and only let specific molecules
through. (Many of the monosaccharide’s and disaccharide’s move to the capillaries via
facilitated diffusion)
____________________: materials are moved across a cell membrane from a lower
concentration to a higher concentration using energy provided by the cell. Special protein
carriers are embedded in the membrane to carry large molecules and ions across
Diffusion
Large Intestine


1.5m in length and 7.6cm diameter
Most of our food has been digested and absorbed except for indigestible material
like__________________. They provide bulk and help us maintain a full feeling for longer

________________ from the leftover matter is absorbed via osmosis as it passes through the
colon.
o After water is removed, feces, the undigested waste, is eliminated from the body
o The removal of too much water= ________________
o The removal of too little water= _________________
Vitamins B and K, sodium Na+, Cl-, are absorbed
Takes from 4hrs to ___________hrs for undigested material to move through the large intestine
There are more than ____________species of bacteria that inhabit the large intestine
o E.coli: produce vitamins K and B
o Bi-product of the bacteria is the production of gas (carbon dioxide, methane and
hydrogen sulphide



Composed of the CECUM, COLON, RECTUM, ANUS



______________: the end the large intestine below the opening to the small intestine. A “dead
end” that receives processed material from the small intestine. Also contains an opening to the
appendix
_____________: longest part of the large intestine and has four segments; the ASCENDING,
TRANSVERSE, _______________ and the ______________ colon.
_____________: the last 20cm of the large intestine. Holds waste products of digestion until
they are eliminate through the external opening, the anus.
o Nerves in the walls of the large intestine detect the movement of feces in the rectum
and this stimulates the __________________ reflex. We are in control of this reflex to a
certain degree.
o The internal( smooth muscle and ________________) and external(skeletal and
_____________________) anal sphincters control the process of defecation
Nausea, Vomiting and Diarrhea
_____________: unpleasant feeling associated with the urge to vomit. Your mouth may water, you may
break into a cold sweat, look pale and your stomach may feel upset.
____________(vomiting): a protective mechanism for removing toxins or foreign substances from the
body. The expulsion of stomach contents through the esophagus and mouth
o
o
o
Strong muscular contractions of the diaphragm and abdominal muscles, force the
contents (vomitus) of the stomach up
The gastroesophageal sphincter ____________________
Breathing _____________ as the larynx and epiglottis close the entrance to the trachea
Causes of vomiting:
o
o
o
o
_______________ of an underlying condition
Occurs in response to a signal from the stomach, intestines, bloodstream, inner ear, or
sensory organs
Examples:
 Inner ear: _______________________
 Drugs: _______________________, antibiotics, nicotine, alcohol
 Infections: bacterial (E. coli), viral (stomach flu)
 Brain: _________________, migraines, tumors
 Injury: concussion, hemorrhage
 Diseases: gall bladder disease, cancer, ___________________
Risks: dehydration, _____________ in respiratory tract causing asphyxiation or
infection, tears in the lining of the esophagus and/or strains in abdominal muscles
___________________: loose or watery feces as a result of inadequate absorption
o
o
o
Accompanied by upset stomach, stomach pains/cramps and intestinal gas
Causes: bacteria (salmonella, E.coli), viruses and parasites
E. coli infections can lead to internal ______________, severe dehydration, and in
severe cases _____________ failure (Walkerton water)
________________: is swelling (inflammation) of the large intestine (colon).
o
o
Causes: food poisoning, inflammatory disorders(ulcerative colitis and Crohn's colitis),
irritable bowel syndrome, lack of blood flow (ischemic colitis) or past radiation to the
large intestine
Symptoms can include: bloating, gas, bleeding, chills, constant urge to defecate,
diarrhea, dehydration, fever and abdominal pain
Feedback Loops
Hormones operate on positive or negative feedback loops:
Homeostasis – state of constancy / maintaining an internal steady state
Negative feedback – a change in a physiological variable triggers a response that
counteracts the initial change
Postive feedback – a change in a physiological variable triggers a response that amplifies
the change
Examples of Positive Feedback
1) Childbirth
 Pressure of baby’s head against sensors near opening of the uterus stimulates uterine
contractions
 Contractions cause greater pressure against the uterine opening which causes stronger
contractions
 Stronger contractions cause even greater pressure
 Eventually allows child to be born
2) Gastrin
 Impulses from brain (sight, smell, taste of food) stimulate stomach wall to produce
gastric juice which begins digestion of food in stomach
 Then the products of digestions (substances in the food) stimulate the stomach wall to
release the hormone gastrin into the circulatory system
 As gastrin recirculates in the bloodstream back to the stomach wall, the hormone
stimulates further release of gastric juice
 Therefore initial burst of gastric juice is followed by a sustained secretion that continues
to add gastric juice
Examples of Negative Feedback
1) Thermostat
 Set thermostat to 20 ºC (set point)
 If temperature falls below 20 ºC, the thermostat switches on the heater
 When thermometer detects that temperature is now above 20 ºC, the thermostat
switches the heater off
 Therefore, change in variable (temperature) triggers mechanism that counteracts the
change (cold) to prevent further change in the same direction (more cold)
2) Body Temperature (sweating)
 Brain detects rise in body temperature
 Sends nerve impulses to sweat glands to increase the production of sweat
 Sweating lowers body temperature by evaporative cooling
(H2O(l)  H2O(g) is an endothermic reaction)

When body temperature drops below set point then brain stops sending signals
3) Gastrin
 Gastric juice is very acidic (HCl)
 If the pH of the stomach becomes too acidic (too much gastric juice) the acid will inhibit
the release of gastrin
 This decreases the production of gastric juice helping the pH to return to normal levels
**Therefore Gastrin is an example of both a positive AND a negative feedback loop!
Homework:
1. Draw a flow chart diagram of how digestion works starting from when food enters the mouth to the point that
it exits. Include all major organs, and sphincters (be specific with the sections of the small and large intestines). –fill
in below
2. For each of the organs list any hormones/enzymes for chemical digestion and examples of physical digestion. –
fill in chart below
3. What does bile do? Is this physical or chemical digestion?
4. What is the overall purpose of the small intestine? Large intestine?
Enzyme
Amylase
Function/Location
Peptidases
and
Proteases
Lipases
Erepsin
TrypsinogenTrypsin
Hormone
Gastrin
ProsecretinSecretin
CCK
Function/ Location
Mouth