3.4 Organising digestion

• Biology
• Middelbare school
• vwo
• Leerjaar 2

Organising digestion

3.4

Chapter 3: Break it down?

Learning goals of this lesson

• What are the organs and theri functions of the digestive system?
• What is peristalsis, digestion and emulsification?
• Which digestive juices does our body produce and what do they do?

Organs in your digestive system

mouth

oesophagus

stomach

duodenum

small intestines

large intestines 

rectum 

anus

In your mouth

Your teeth, tongue and chewing mussles are mixing the food, you ate with saliva -> amylase starts to digest the startch in your food.

The oesophagus moves the food towards your stomach. 

The mussles in the oesopagus using peristalsis to transport the food.

Oesophagus

No digestive juices

Peristalsis to move the food down

Longitudinal mussles push the food bolus further down

Circular mussles are closing and relaxing arround the food bolus.

What is peristalsis?

the Stomach

It is a muscular bag where food is churned by the mussles.

this is mechanical digestion. -> reason is to increase the surface area of the food.

But in the stomach also chemical digestion takes place.

The stomach produces HCl (hydrochloric acid) and Pepsinogen.

The pepsinogen turns in an acid environment into pepsin. And pepsin breaks down the fat in your food.

Protease breaks down the proteins in your food.

bolus - foodpart with saliva or other enzymes which is travelling through your digestive system

Pylorus

a circular muscle, which closes the stomach

It is between the stomach and the duodenum

the Duodenum

Latin for twelve fingers.

Digestion with two juices.

-> pancreatic juice

-> bile which is made in the liver.

Pancreatic juice

Made in the pancreas.

Mixture of different enzymes.

These enzymes break down carbohydrates, proteins and fats.

These juices appear in the duodenum.

Why is bile neccesary for you digestion?

Bile

Bile is produced in the liver.

Bile is stored in the galbladder.

What is the reason why from a patient where the galbladder is removed, may not eat so much fat anymore?

Small intestines

digestion is completed

enzymes in interstinal juices

break down of undigested carbohydrates and proteins

All end products of digestion are absorbed into the bloodstream

Small intestines

the lining isn't smooth

millions of small villi

The reason is to absorp as many nutrients as possible.

Network of capilaries

Hepatic portal vein -> straight to the liver

Large intestines

Indigestible waste

water from digested food

1,2 metre long tube

Solid waste is called faeces

rectum

Faeces are collected in  the rectum

Muscles control elimination

Faeces can be stored for up to three days. 

(sometimes more - constipation)

Bacteria

Bacteria are needed to break down undigested materials

Bacteria make vitamins like vitamin K and two kinds of vitamin B

Breakdown by bacteria also produces gas