IGCSE Biology - Unit 2 - Structures and Functions in Living Organisms

Three main duodenal secretions

- bile - pancreatic juice - duodenal enzymes

stomach functions

- digestion of protein - physical digestion - storage of food in duodenum for further digestion

How many teeth does a child have?

20

How many teeth does an adult have?

32

mucus function

Mucus protects the stomach lining from hydrochloric acid and pepsin

Name the two parts of the small intestine

duodenum and ileum

oesophageal wall muscles

longitudinal and circular

What is the function of the stomach?

main function is digestion. It does this by: Storing the food we eat. Breaking down the food into a liquidy mixture called chyme.

duodenal enzymes

- protease - lipase - maltase (breaks down maltose - glucose)

What four things are in gastric juices?

1. water 2. hydrochloric acid 3. mucus 4. pepsin

stomach

A muscular and elastic j-shaped sac. Usually holds around 2-3 litres, but can hold much more.

rectum

A short tube at the end of the large intestine where waste material (faeces) is compressed into a solid form and stored before being eliminated

bile

A substance produced by the liver that breaks up fat particles and neutralises chyme's acidity. Stored in the gall bladder and passed to duodenum through bile duct.

pancreas

An organ in the abdominal cavity - produces digestive enzymes and bicarbonate, which are delivered to the small intestine via the pancreatic duct. - secretes insulin and glucagon into the bloodstream to help regulate blood glucose levels.

gall bladder

An organ that stores bile and releases it as needed into the duodenum

digestion

Breakdown of food substances into simpler forms that can be absorbed and used

digestive system

Breaks down food into smaller molecules. Absorbs these nutrients into the body.

How is digested food absorbed in the small intestine?

Diffusion and active transport through the villi into the capillaries and lacteal.

peristalsis

Involuntary waves of muscle contraction and lengthening that keep food moving along in one direction through the digestive system

oesophagus

Muscular tube which moves ingested food to the stomach

villi

Small fingerlike projections on the walls of the small intestine that increase surface area. Wall of each villus is only 1 cell thick - diffusion is easier.

What is the function of pancreatic juice?

To produces 3 enzymes which catalyse the break down of starch, fats/oils and proteins.

Why is the inner surface of the ileum covered in villi?

To provide a large surface area and thin walls to better effect diffusion and absorption.

What is the main function of the large intestine?

To reabsorb useful material (water) and process undigestible material (mostly fibre) for excretion.

saliva contents

Water, salts, ions, and mucus - enzymes including amylase, which begins the digestion of complex carbohydrates - some white blood cells

bolus

a ball of food after it has been chewed and mixed with saliva

cardiac sphincter

a circular muscular valve located between the oesophagus and the stomach

rennin

a natural complex of enzymes produced in any mammalian stomach to clot milk protein so milk can be digested

protease enzymes

break down proteins into amino acids

duodenum function

digestion of the chyme from the stomach and secretions from the liver and pancreas

pancreatic juice contains

enzymes that digest -carbohydrates (pancreatic amylase - starch - maltose) -fats (lipase) -proteins (protease)

gastric glands

exocrine glands in the stomach wall that secrete gastric juice into the stomach

saliva

fluid which softens food in the mouth making it easier to swallow; helps break down food into simpler forms; secreted by glands in the mouth

pepsin

gastric enzyme that breaks down proteins into smaller polypeptide fragments

colon

large intestine

buccal cavity

mouth

pyloric sphincter

opening from the stomach into the duodenum

gastric enzymes

pepsin and gastric lipase; become active at low pH when mixed with stomach acid

colon function

reabsorbs fluids and processes waste products of undigestible foods (mostly fibre)

What's the function of the gall bladder?

stores bile

ileum

the lowest and longest portion of the small intestine; where digestion is completed

lacteal

the lymphatic vessels of the small intestine that absorb digested fats

pharynx

the membrane-lined cavity behind the nose and mouth, connecting them to the oesophagus

egest

to discharge or excrete from the body

ingest

to take food, drugs, etc. into your body, usually by swallowing

duodenum

upper part of the small intestine, horseshoe-shaped tube

gastric juice

water + digestive secretions of the stomach glands consisting chiefly of hydrochloric acid, mucus and enzymes

ileum wall

where blood capillaries and lacteal absorb digested nutrients through diffusion and active transport