Animal Cell Biology, Body Systems Glossary

animal cell

The basic unit of animal tissues and organs

cell

The smallest unit of life. All living things are made of cells. Most cells are too small to see with the naked eye.

cell division

The splitting of a cell to form new cells. All cells come from pre-existing cells. Cell division allows organisms to grow and reproduce.

cell membrane

A thin layer that forms the boundary of a cell. The cell membrane holds the cell contents in and controls which substances pass in and out.

cell wall

A rigid structure that protects and strengthens some cells. Plant cells have cell walls around their cell membranes. Animal cells do not have cell walls.

chloroplast

An organelle that absorbs sunlight energy and stores it in sugars. Chloroplasts carry out photosynthesis in some plant cells. They are not found in animal cells.

cytosol

A jelly-like fluid that fills the space inside a cell. Small structures called organelles float in the cytosol.

mitochondrion

An organelle that breaks down sugars to supply energy. Mitochondria are a cell's 'power plants'.

multicellular organism

A living thing made up of two or more cells. Humans, insects, mushrooms and trees are examples of multicellular organisms.

neuron

A branched cell that sends signals in the brain or through nerves. Neurons have branching structures that help them send and receive signals.

nucleus

An organelle that controls a cell's activities. The nucleus stores DNA, which instructs how the cell grows and functions.

organ

A body part that performs a specific function. Organs are made up of tissues. Examples of organs include the brain, heart, lungs and stomach.

organelle

A structure in a cell that performs a particular function. Organelles, or 'little organs', carry out the processes needed to keep cells alive.

plant cell

The basic unit of plant tissues and organs. Unlike animal cells, plant cells have cell walls, large vacuoles and often chloroplasts.

red blood cell

A small, round cell that carries oxygen around the body. Red blood cells have disc shapes and contain haemoglobin to help them carry oxygen.

specialised cell

A cell with unique structures to perform certain functions in the body. The size, shape and features of a specialised cell are adapted to help it do its job.

tissue

A group of similar cells that work together. A group of tissues form an organ. Examples of tissues include muscle, bone, blood and skin.

unicellular organism

A living thing made up of a single cell. Bacteria and yeast are examples of unicellular organisms.

vacuole

An organelle that stores fluids, nutrients and wastes. A plant cell has a large vacuole to store water. Animal cells have many small vacuoles.

chemical digestion

The breakdown of food by saliva, stomach acid and other digestive juices.

digestion

The breakdown of food into simple nutrients the body can absorb.

digestive system

The group of organs that break food down into simple nutrients the body can absorb.

digestive tract

The connected organs that food passes through as it is broken down.

large intestine

A wide tube where water is absorbed and most good bacteria live.

liver

A large organ that produces bile to help digest fats.

oesophagus

The tube that connects the throat to the stomach.

peristalsis

Involuntary muscle contractions that push food through tubes.

physical digestion

The breakdown of food by mashing, grinding, churning or mixing.

small intestine

A long, narrow tube where most nutrients are absorbed by the body.

stomach

A muscular pouch that churns and squeezes food into liquid.

alveolus

A tiny air sac in a lung where gas exchange occurs.

breathing

The process used by animals to exchange gases with the atmosphere.

bronchiole

A tube that carries air through a lung.

cellular respiration

The process used by all living cells to release energy.

diaphragm

A large sheet of muscle that contracts to draw gas into the lungs.

diffusion

The movement of molecules from an area of high to low concentration.

gas exchange

The movement of oxygen into the blood and carbon dioxide out of it.

lung

An organ where gas exchange occurs between air and blood

respiratory system

A group of organs that allows an animal to exchange gases with its environment

trachea

The main airway between the throat and the lungs

artery

A tube that carries blood away from the heart

blood

The fluid pumped by the heart around the circulatory system

blood vessel

Any tube that blood flows through

capillary

A tiny blood vessel where substances pass to and from the blood

circulatory system

The body system that moves blood throughout the body

heart

A muscular organ that pumps blood around the body

left atrium

A heart chamber that receives blood from the lungs

left ventricle

A heart chamber with thick walls that pumps blood to the body

red blood cell

A blood component that transports oxygen

right atrium

A heart chamber that receives blood from the body

right ventricle

A heart chamber with thick walls that pumps blood to the lungs

vein

A tube that carries blood back to the heart

bladder

A muscular pouch that receives and stores urine

excretion

The removal of waste products from the body

excretory system

The body system that gets rid of waste products

kidney

An organ that filters blood and excretes urine

ureter

A long tube that carries urine to the bladder

urethra

The tube that carries urine out of the body