10 - Biology unit 3 Human Digestive System

ingestion

take in food

digestion

breaks food down into subunits our body can use

CHOs are digested into…

monosaccharides

Lipids are digested into…

glycerol and fatty acids

Proteins are digested into…

amino acids

Nucleic acids are digested into…

nucleotides

absorption

absorb subunits into our blood which acts as a “taxi” to carry them to all cells of the body

elimination

gets rid of indigestible materials

what are the 4 “steps” of the digestive system

1. ingestion

2. digestion

3. absorption

4. elimination

digestive tract (2)

• long tube (9m)

• food enters one end of the tube and waste (feces) leaves the other end of the tube

7 part of the digestive tract in order

mouth, pharynx, esophagus, stomach, small intestine, large intestine, & anus

Accessory digestive organs (3)

• add substances to the food to help digest it

• 4 “extra” parts of the digestive system

• salivary glands, liver, gallbladder, and pancreas

2 parts of the digestive system

1. digestive tract

2. accessory digestive organs

2 ways that food is digested

mechanically digested & enzymatically digested by diffrent digestive enzymes

define mechanically digested

broken down into small pieces by the teeth

define enzymatically digested

the digestive system produces at least one digestive enzyme to break down each of the 4 main types of organic molecules that food is made of

salivary glands

release saliva into the mouth

functions of saliva (2)

1. lubricates the food so it slides down the esophagus more easily

2. contains the digestive enzymes salivary amylase which breaks down polysaccharides into monosacs and disacs

What does salivary amylase do?

breaks down carbohydrates into monosacs and disacs

Peristalsis

wave-like contractions of the smooth muscle (that forms part of the wall of the digestive track) that pushes food forward

Epiglottis

during swallowing it covers the opening to the trachea so that food goes into the esophagus

Stomach (4)

• the inside surface of it is highly folded when empty

• 3 parts: cardiac sphincter, pyloric sphincter, & rugae

• the inner surface of it is lined with pits

• pits in it lead to gastric glands

what are the folds in the stomach called?

rugae

gastric glands secrete (3)

mucus, pepsinogen, & hydrochloric acid

function of:

a) mucus

b) pepsinogen

c) hydrochloric acid

a) coats the inside of the stomach and protects it from acid

b) a digestive enzyme that is activated to it's active form (pepsin) by acid

c) activates pepsin and kills microorganisms (e.g. bacteria) found in food

how is food moved through the digestive tract?

peristalsis, wave-like contractions of the smooth muscle (that forms part of the wall of the digestive tract) that pushes food forward

what prevents food from going down the wrong way?

the epiglottis

draw how an enzyme breaks down sucrose

Ulcer (3)

• a sore that develops in the stomach when there is not enough mucus to protect it's inner wall

• in the past it was believed that ulcers were caused by stress and by spicy foods

• it is now know that most ulcers are caused when a person is infected with a bacterium called Helicobacter pylori

How can Helicobacter pylori be killed

by taking antibiotics

Helicobacter pylori

a bacterium that can cause ulcers

Chyme

a soupy liquid that food becomes when the chewed food mixes with gastric juices in the stomach

non-digestive functions of the liver

it makes blood clotting proteins

what does -ogen indicate?

an inactive enzyme

3 digestive function of the liver

1. filters out extra sugar from the blood and stores it as glycogen

2. detoxifies chemicals that can harm the body (e.g. alcohol, certain drugs)

3. produce a liquid called bile

Bile

helps digest lipids by breaking down large fat droplets into tiny fat droplets

Gallbladder

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

Pancreas

produces digestive enzymes that mix with the chyme in the small intestine

4 digestive enzymes found in the pancreas and their use

1. Pancreatic amylase - breaks down CHOs onto monosacs

2. Trypsin - breaks down proteins into amino acids

3. Chymotrypsin - same as trypsin

4. Lipase - breaks down mono-, di-, and triglycerides into glycerol and fatty acids

Small intestine (2)

• most absorption of nutrients into the blood occurs through the wall of the small intestine

• to make absorption more efficient, the small intestine has evolved to have huge inner surface area

what increases the surface area of the small intestine? (4)

• it is very long (7 meters)

• it's inner surface is folded

• it's inner surface is lined with villi

• each villus has microvilli

Villus (4)

• the small intestine is lined with millions of villi

• each villi is 1mm long

  • an arterioles (small artery) carries blood into a villus

  • the arteriole branches to form capillaries (the smallest blood vessels)

How do organic molecules enter the villus?

• monosacs, amino acids, and nucleotides enter a villus by diffusing through it's epithelium into the capillaries and are carried to all cells of the body

• fatty acids and glycerol enter a lacteal and are then carries into the blood

Large intestine (2)

• aka the colon

• the last part of the digestive system

3 functions of the large intestine

1. excess water gets absorbed through the wall of the large intestine into the blood

• chyme is now feces

2. trillions of bacteria live in the LI

• some of those bacteria make vitamins that we need

3. undigestible things (e.g. cellulose) collect in the rectum (which is the last part of the LI)