ND Sports and Exercise Science

Unit 12 – Nutrition Outcome 1b – The digestive

system

Outcomes

• To understand the basic functions of the digestive system

• To be able to name the organs involved in the digestive system

What is Digestion?

• A process by which nutrients and minerals are digested and passed through the body

• Divided in to two groups of organs• The digestive tract – from the mouth

to the anus• The accessory Organs – necessary for

the system to work but not on the tract

The digestive system – basics

Organs involved

• Buccal cavity – mouth • Oesophagus • Stomach• Duodenum• Small intestine• Pancreas• Liver• Gall bladder• Large intestine• Rectum • Anal canal

Task

• In pairs jot the functions of each organ in the digestive system on post it notes

• One post it note to each organ

Mouth and Oesophagus

• Digestion starts in the mouth (buccal cavity). Teeth and jaws grind food to mix it with saliva, which contains the enzyme amylase that begins the breakdown of starch.

• The food is swallowed, enters the oesophagus, which connects the mouth to the stomach, it is squeezed along the oesophagus by a process called peristalsis.

Peristalsis

• Muscular movement of food through the digestive tract

Stomach

• It takes around 3-6 seconds for food to travel from your mouth to your stomach

• Lining your stomach are cells that produce and release gastric juices containing enzymes and hydrochloric acid, which helps to break down the food and kill any bacteria in it.

• Food normally retains in your stomach for 1-4 hour but fluid will pass through more rapidly

Stomach• Serves as a storage

pouch, digestive organ and churn

• Stomach can stretch to hold 12 pints of liquid and food

• Cells produce gastric juices and acids that breaks food

• The mixed food and gastric juice leaves the stomach as chyme

• On to the small intestine

Duodenum and small intestine

• Stomach the chyme passes to your duodenum and then to your small intestine, a tube of about six metres length

• The duodenum is the start of the small intestine, and curves around the pancreas

• As the chyme enters your small intestine it is mixed with more digestive juices, from the pancreas.

• Pancreatic juices contains bile made by the liver as well as enzymes to further assist the breakdown of macronutrients.

Small Intestine• Longer in length

than the large intestine but is smaller in diameter than the large

• Lined with thousands of villi that absorb the digested food, water and minerals

Liver

• Manufactures bile• Stores glycogen• Modifies fats• Storage of vitamins

and iron• Detoxification of

harmful substances – alcohol and drugs!

Bile

• Main function of the liver is to produce bile

• Bile processes fats• Bile travels from the liver to the

gallbladder and then in to the duodenum

Pancreas• Produces enzymes that digests fat,

protein and carbohydrates• Produces insulin and glucagon that

regulate sugar metabolism• Released in to the blood

Gall Bladder

• Liver produces bile though out the day

• Body only needs it a few times a day

• Gall bladder stores it and provides when needed bile through the duodenum

Gall Bladder

• Stores and concentrates bile until it is required for digestion

• It is then released in to the digestive tract to emulsify fats and neutralise the acids in partly digested foods

• Peristalsis continues to move the chyme through your digestive system to your large intestine

Large intestine

• No food is digested here – some water is re-absorbed

• The undigested food is stored as faeces• Bacteria in your large intestine produces

vitamin k • The residue left behind is passed to the

rectum and anal canal and is excreted as faeces

Large Intestine

Function of the digestive system

• So, what are the main functions of the digestive system?

• Digestion• Absorption• Excretion

Digestion

• The first stage• Multi stage process• Mechanical and chemical elements• Enzymes in the gut breaking down

raw matter in to smaller compounds for your bodies to absorb

Absorption

• Movement of digested food from your stomach and small intestine into your body tissues and blood

• Happens in the villi that line the large intestine

• Each villus has a large network of capaliries to support this absorption

• Amino acids (from proteins) and glucose (from carbs) = blood stream directly

• Fatty acids and glycerol (both from fats) = lymphatic system

Excretion

• Removal of potentially poisonous end produce through urine and faeces

• Kidneys = urine is eliminated and passed to your bladder

• http://resources.schoolscience.co.uk/ABPI/kidneys/kid2.html

• Large intestine = passes solid matter

Task

• Using the cards and diagrams order the organs involved in the digestion process

• Label the blank diagram• Produce a table outlining the function

of each organ

References and resources

• http://www.sparknotes.com/health/digestion/quiz.html

• Memmler’s human body in health and disease, B. Cohen Lippincott, Williams and Wilkins 2005