9-1 Edexcel IGCSE Biology - Unit 2: Animal Physiology - Digestion, iGCSE edexcel Biology: Animal Anatomy and Physiology - 2-3 Breathing and Gas exchange

digestion

process by which food is broken down into smaller molecules that can be absorbed

enzyme

protein that acts as a biological catalyst

peristalsis

waves of muscular contraction that push food along the gut

duodenum

first part of the small intestine following the stomach

pancreas

gland discharging into the duodenum. Makes digestive enzymes and is also an endocrine organ, secreting the hormones insulin and glucagon

ileum

last part of the small intestine, where the products of digestion are absorbed into the blood

faeces

semi-solid indigestible waste that passes out of the gut via the anus

carbohydrase

enzyme that digests carbohydrates

protease

enzyme that digests protein

lipase

enzyme that digests lipids

saliva

digestive juice secreted into the mouth by the salivary glands. Contains the enzyme amylase

amylase

enzyme that digests starch into maltose

oesophagus

part of the alimentary canal between the mouth and the stomach

pepsin

protease enzyme made in the stomach

sphincter muscle

ring of muscle in the wall of an organ, which holds back its contents

liver

large organ in the abdomen that has many functions, including the storage of glycogen, manufacture of bile and breakdown of amino acids

bile

green liquid made by the liver and stored in the gall bladder. Causes lipids in the gut to form an emulsion, increasing their surface area for easier digestion by enzymes

gall bladder

organ that stores bile from the liver

bile duct

tube carrying bile from the gall bladder to the duodenum

microvilli

minute projections from the surface membrane of some cells, such as those on the surface of the villi of the ileum, where they increase the surface area for the absorption of the products of digestion

lacteal

structure in the middle of a villus, containing lymph and forming part of the lymphatic system. The lacteal absorbs products of lipid digestion

hepatic portal vein

blood vessel transporting products of digestion from the ileum to the liver

colon

first part of the large intestine, where water is absorbed from the waste material in the gut

rectum

last part of the large intestine, where faeces is stored

anus

outlet of the gut where faeces is expelled from the body

Lungs

two spongy organs, located in the thoracic cavity enclosed by the diaphragm and rib cage, responsible for respiration

Trachea

a large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes and conveying air to and from the lungs; the windpipe.

lung ventilation

movement of air into and out of the lungs

thorax

chest

Respiration

The process by which cells break down simple food molecules to release the energy they contain.

Diaphragm

a dome-shaped, muscular partition separating the thorax from the abdomen in mammals. It plays a major role in breathing, as its contraction increases the volume of the thorax and so inflates the lungs.

intercostal muscles

Muscles located in between the ribs that play a role in ventilation.

Bronchi

two short branches located at the lower end of the trachea that carry air into the lungs.

Bronchioles

smaller branches of the bronchi

Alveoli

tiny sacs of lung tissue specialized for the movement of gases between air and blood

cartilage rings of trachea

These stabilize the trachea.
They allow the trachea to expands and lengthen when the person breathes.

pleural membrane

double-layered serous membrane that encloses and protects each lung

pleural cavity

space between the folds of the pleura

pleural fluid

liquid that surrounds the lungs

mucus

A thick, slippery substance produced by the body

bronchitis

inflammation of the bronchi

Emphysema

a condition in which the air sacs of the lungs are damaged and enlarged, causing breathlessness.

Nicotine

a stimulating and highly addictive psychoactive drug in tobacco

Carcinogen

A cancer-causing substance

tumour

a mass of cells that continue to grow and divide without any obvious function in the body

Haemoglobin

Protein molecule in the blood responsible for carrying oxygen around the body

carbon monoxide

a colorless, odorless toxic flammable gas formed by incomplete combustion of carbon.

carboxyhaemoglobin

A compound formed when haemoglobin combines with carbon monoxide in preference to oxygen