Human Digestive Tract Part 2 Flashcards
What are accessory organs?
organs that connect to the gastrointestinal tract but in which food does not enter
endocrine definition
secretion of hormones directly into bloodstream
exocrine definition
secretion of products from glands into ducts
The human pancreas contains both endocrine and exocrine areas
What are exocrine pancreatic cell examples? What do they secrete?
- acinar and duct cells
- make up 99% of pancreatic cells
- they secrete digestive enzymes and NAHCO3
How do the digestive enzymes and NaHDO3 get to the duodenum
through ducts
What are endocrine cells called?
Islets of Langerhans (alpha, beta, delta, F cells)
What do endocrine cells do? What percentage of pancreatic cells to they make up?
Endocrine cells secrete hormones directly into the bloodstream. They make up 1% of pancreatic cells
What is the shape of acinar cells?
truncated pyramid
How are acina cells arranged? How do they empty?
They are arranged in groups around a central duct. The central duct then empties into the pancreatic duct, which then empties into the duodenum.
What type digestive enzymes does the pancreas produce? What else does it produce?
enzymes that digest proteins, starches, and lipids. It also produces buffers that neutralize acid from the stomach
What enzymes does the pancreas produce that digest PROTEINS?
trypsin, chymotrypsin
What enzymes does the pancreas produce that digest STARCHES?
amylase
What enzymes does the pancreas produce that digest LIPIDS?
lipase
What do proteases do?
They degrade protein to amino acids
What do lipases do?
They degrade fats to fatty acids and glycerol
What do amylases do?
They degrade carbohydrates to glucose
What does the pancreatic duct do?
it carries pancreatic juice to duodenum of small intestine
What is a substrate?
a molecule that binds to an enzyme at the active site
What is an active site on an enzyme?
where an enzyme catalytic reaction occurs
Most enzymes are proteins. They all have a specific substrate. A catalyst is also component, it is not used up in the reaction.
What stimulate the pancreas to secrete enzymes?
hormones
What enzymes does the pancreas secrete?
secretin, cholecystokinin (CCK), acetylcholine
cholecystokinin is released from the duodenum by the presence of
dietary fat, amino acids, and hydrochloric acid
When is acetylcholine produced?
as a response to the sensory aspects of feeding and to the physical effects of chewing and swallowing
After the pepsin is diactivated by the hgiher pH in the duodenum, the proteins can be further digested by other proteases such as:
- trypsin
- chymotrypsin
- carboxypeptidase
- erapsin
What is a zymogen?
A zymogen is the inacter precursor of an enzyme. It requires activation for the enzyme to work.
What is the trypsin pathway?
- the pancreas secretes inactive trypsinogen
- Once in the duodenum, the enzyme is converted from trypsinogen to active trypsin
- the new trypsin further breaks down proteins.
- Lastly, the trypsin then activates other proteases and peptidases
What are the 5 functions of the liver?
- detoxification (alchohol and drugs)
- Bile production and drainage and the synthesis of blood protein
- Synthesis and storage of amino acids, proteins, vitamins and fats, glycogen
- blood glucose regulation
- blood circulation and filtration - removes toxic nitrogen group from amino acids and hemoglobin to form urea (pee)
BREAKS UP FATS?
What does the gall bladder do?
It only stores bile - that’s why you can have you gall bladder removed
What does the liver do in relation to the digestive system?
- it continually produces bile
- emulsifies fat in the small intestine
- physical digestion
- stored in gall bladder
How does the hormone Cholecystokinin (CCK) relate to the gallbladder?
CCK is carried by the blod to the gallbladder when food enters the smal intestine to release bile
Where is the gallbladder located?
underneath the liver
What does the bile duct do?
It carries bile from the gall bladder to duodenum
What is bile made from?
cholesterol and bile salts
What does bile do?
It acts like a dish detergent. It breakdowns fat by emulsifying it into smaller fat molecules. This allows for greater surface area for lipases to work
What are gallstones?
the crystallization of bile components which are bile salts and cholesterol. It hardens to form stones
What is the result of gallstones?
blocked bile duct and pain
What are the causes of gallstones?
- If the bile contains either too much cholesterol or bilirubin
- If the bile doesn’t contain enough salts
- If the bile duct doesn’t fully empty
- diet and body weight
What are the treatments for gallstones?
- surgery -> including laparoscopic cholecystectomy
- shock wave lithotripsy - blast gallstones into small pieces
how many litres of water are used everyday in digestive juices?
roughly 9
What ist he function of the large intestine?
It reabsorbs the water.
What would happen if the water was not reabsorbed?
you would die of dehydration?
How much of the water is reabsorbed?
more than 90%
What happens if not enough water is re-absorbed?
diarhea, which can be fatal
What can happen is too much water is absorbed?
constipation
How is the water reabsorbed?
by diffusion
What are the 5 sections of the Large intestine?
- Cecum
- appendix
- colon
-rectum - anus
What are the 4 parts of the colon?
ascending, transverse, descending, and sigmoid
What is the cecum?
The first part of the large intestine. It is the blind end, sac-like pouch
What is the ileocecal valve (sphincter?)
It seperates the cecum from the ileum. It stays close most of the time to prevent backflow of waste
The appendix is vestigial. It may have had a role in evolutionary past. It is believed to shelter beneficial bacteria for digestion?
What is the appendix?
It is a blind-end tube, suspended from cecum. It plays no role in digestion in modern humans.
What is appendicitis?
When the appendix gets infected?
What is the largest part?
the colon
What are the functions of the colon?
ot abosrobs water, salts, residual nutrients, minerals and vitamins. It also passes waste material from the body
What is one bacteria that lives in the large intestine?
Escherichia coli: E.coli
What does E.coli in the large intestine do?
- it digests cellulose (fibre?)
- produces vitamins
- generates gases
What vitamins to E.coli produce?
vitamin K, vitamin B12, Thiamine and Riboflavin
What gases do E.coli generate?
methane, hydrogen sulfide
What is Rectum? What does it do?
It is the last section of large intestines. It stores and eliminates feces.
What’s left over in the rectum?
undigested materials that consist of:
- mainly cellulose from plants called roughage or fibre
- masses of bacteria
What does fibre do?
it keeps everything moving & cleans out intestines
What egestion?
pooping
What is the process of egestion?
- stretch receptors trigger contractions when rectum is full
- forms peristaltic waves to expel feces through the anal canal and anus
- Anal sphincters allow body to control timing egestion
What are feces?
damp masses of indigestible material at the end of absorption
When does constipation occur?
When there is a slow movement of feces through the large intestine, the colon absorbs too much water. This results in an accumulation of dry, hard feces.
How many times should bowel movements occur?
3 or more times during a week
What are the causes of constipation?
- not enough water and fibre intake
- not enough exercise and mobility
- stress and depression
- certain medications have been shown to cause constipation
What are some constipation treatments?
diet and lifestyle changes - increase fibre in diet by consuming more fruit, vegetables and whole grain products and drink 8-10 cups of water daily
When does diarhea occur?
When a rapid movement of feces through large intestine, not enough water is absorbed. It is also a protective mechanism for the body to remove toxins and foreign substances. It can lead to a loss of mineral and fluid.
What is the usual cause of diarhea?
viral and bacterial infection
What are some treatments for diarhea?
- treat the symptoms: replacement saline, glucose solution
OR - infection: treat with antibiotics if bacterial
What kind of teeth do carnivores have?
sharp ripping teeth - canines
What kind of teeth do herbivores have?
wide grinding teeth - molars
What kind of teeth do omnivores have?
both canine and molars
Describe the digestive system of herbivores and omnivores.
- long digestive systems
- harder to digest cellulose -> bacteria in intestines help
Describe the digestive systems of carnivores
- short digestive systems
- protein easier to digest than cellulose