human digestive system 🥗

what are the four steps of digestion?

ingestion, digestion, absorption, elimination

what are the 2 parts of the digestive system?

the digestive tract and the accessory digestive organs

what are the 7 parts of the digestive tract in order?

1. Mouth
2. Pharynx
3. Esophagus
4. Stomach
5. Small intestine
6. Large intestine
7. Anus

what do accessory digestive organs do?

add substances to food that help digest it, but do not make contact with food

name the accessory digestive organs (4)

salivary glands, pancreas, gallbladder and liver

how long is the digestive tract?

9 metres

what happens in the digestive tract?

food enters one end of a tube and waste/feces exits the other end

what subunits does digestion break food into?

CHOs become monosaccharides, lipids become glycerol and fatty acids, nucleic acids become nucleotides, proteins become amino acids

label

what are the 2 types of digestion?

mechanical digestion and enzymatic digestion

what does mechanical digestion do?

breaks food down into small pieces using the teeth

what does enzymatic digestion do? (2)

\- digests food using different enzymes

\-there is at least one digestive enzyme produced by the digestive system for each of the four types of organic molecules

what are salivary glands/ what do they do (3)

\-release saliva into the mouth

\-lubricates food so that it slides down the esophagus more easily

\-produces salivary amylase

what is peristalsis?

smooth muscle forming part of the digestive system wall causes wave like contractions to push food forward

where is peristalsis found? (in order)

esophagus, stomach, small intestine and large intestine

what does the epiglottis do?

prevents food from entering the larynx and trachea by covering them when eating

what are the folds in the stomach called?

rugae

where are gastric glands found?

in pits on the inner surface of the stomach

what do gastric glands secrete (3)

mucus, pepsinogen/pepsin and hydrochloric acid

what does mucus do in the stomach?

coats the inside to protect it from acid

when is pepsinogen activated and what does it become?

activated by HCl in the stomach and becomes pepsin

what does HCl do in the stomach? (2)

activates pepsin, kills microorganisms in food

what does -ogen indicate?

an inactive protein/enzyme

what happens during:

a) ingestion

b) digestion

c) absorption

d) elimination

a) taking in food

b) food is broken into subunits we can use

c) subunits are absorbed into the blood which transports them throughout the body

d) get rid of indigestible materials

label

what is an ulcer?

a sore in the stomach that occurs when there isn’t enough mucus coating the inner wall

a) what did we previously think caused ulcers?

b) what actually causes ulcers?

a) stress and spicy food

b) a bacteria called __Helicobacter__ __pylori__

how are ulcers treated?

antibiotics

what is bolus?

a mass of chewed food mixed with saliva

what is chyme?

bolus that has mixed with gastric juice in the stomach

what happens to the pyloric sphincter after a meal?

it opens every few seconds to allow a small amount of chyme to enter the SI

what is a non digestive function of the liver?

to make blood clotting proteins

what are the digestive functions of the liver? (3)

1. filters extra sugar from the blood and stores it as glycogen
2. detoxifies harmful chemicals like alcohol and drugs
3. produces bile

what does bile do?

\-helps digest lipids by breaking large fat droplets into smaller ones

\-is NOT enzymatic

what is emulsification?

the process by which bile breaks down lipids

what does the gallbladder do?

stores bile until it is released into the duodenum via the bile duct

what is the function of the pancreas?

to produce digestive enzymes that mix with chyme in the SI

what digestive enzymes does the pancreas produce? (4)

pancreatic amylase, trypsin, chymotrypsin, lipase

where does most nutrient absorption occur?

the small intestine

in what ways does the small intestine increase its surface area?

1) 7m long

2) folded inner surface

3) lined with tiny, finger like projections called villi

4) each villus is covered in smaller finger like projections called microvilli

label

what is a hormone?

a substance secreted directly into the blood that has a specific effect on certain tissue

what stimulates the flow of gastric juices? (3)

1) thought/sight/smell/taste of food causes the brain to tell the gastric juices to secrete

2) food touching the stomach lining

3) the production of gastrin

what causes gastrin production? (4)

stretching of the stomach wall, proteins, caffeine, alcohol

how long does it take liquids to pass through the stomach?

20 minutes or less

how long after a meal is the stomach empty?

2-6 hours

what is the stomach’s capacity?

over 2L

what causes mechanical digestion in the stomach?

the stomach wall contracting

what causes heartburn?

the cardiac sphincter relaxes and HCl reaches the esophagus

how many pairs of salivary glands are there?

3

what are the 2 types of saliva?

1) thin and watery, wets the food

2) thick and mucus, acts as a lubricant and helps bolus form

what is another name for the disgestive tract?

alimentary canal

what are the two types of glands in the stomach and what do they secrete?

gastric-gastric juice

pyloric-mucus

what does gastric juice contain?

HCl and pepsin

where is gastrin secreted from?

the stomach lining

what are the three sections of the small intestine in order?

duodenum, jejunum and ileum

what is the shortest section of the SI?

the duodenum (25cm)

what is extracellular digestion and name an example

digestion that occurs outside of cells (ep salivary amylase in the mouth)

how long is a villus?

1mm

label (7)

how are monosaccharides, amino acids and nucleotides absorbed?

by diffusing through the epithelium of a villus into capillaries. they are then sent around the body through blood

how do fatty acids and glycerol enter the blood?

the lacteal

what is the LI also known as?

the colon

what are the three functions of the LI? (3)

1) absorbing excess water into the blood

2) some bacteria in the LI make vitamins we need

3) indigestible materials like cellulose collect in the rectum

name 3 sphincters

anus, pyloric sphincter and cardiac sphincter

what happens when the anus relaxes?

feces elimination

what are the 8 digestive enzymes?

salivary amylase, pepsin, trypsin, chymostrypsin, pancreatic amylase, peptidase, maltase and lipase

what does each digestive enzyme break down?

\-salivary amylase, maltase and pancreatic amylase-CHOs

\-lipase-lipids

\-pepsin, trypsin, chymotrypsin, peptidase-proteins

what are the effects of the SI’s constant movement? (4)

1) chyme is squeezed through the intestine

2) chyme is mixed with the digestive enzymes

3) food particles are broken down mechanically

4) absorption is sped up because the movement forces the chyme to make contact with the SI wall

what 2 hormones does the pancreas secrete and what do they do?

cholecystokinin and secretin stimulate the pancreas and gallbladder to release digestive enzymes/pancreatic juice/bile

what stimulates the release of bile from the gallbladder?

the hormone cholecystokinin

what is the point of emulsification?

it increases the surface area of lipids, making then easier to digest

what enzymes does the SI secrete?

maltase and peptidase

how long is the LI

1\.5m

what is appendicitis?

the appendix becomes inflamed and must be removed

which vitamins do LI bacteria produce?

vitamin K and some B vitamins

what is vitamin K essential for?

blood clotting

what does feces consist of? (5)

cellulose, bacteria, bile, mucus and worn out cells

what are the hormones? (3)

gastrin, cholecystokinin, secretin

what are proteases?

enzymes that break down proteins