Definitions Relating to Poultry Incubation
and Embryology Projects
Classification | Anatomy
| Avian Egg | Incubation
Words about the classification of chickens
- Avian - Of, relating to, or characteristic of birds;
derived from birds.
- Bantam - A small miniature chicken, usually one-fourth
to one-fifth the size of regular chickens; frequently called "bantie."
Most, but not all, bantams are the likeness of a larger variety of domestic
- Breed - A group of chickens within a class having a
distinctive body shape and the same general features and weight.
- Broiler or fryer - A young meat-type chicken, usually
9 to 12 weeks of age, of either sex, that can be cooked tender by broiling
or frying, usually weighing between 2 1/2 and 3 1/2 pounds.
- Class - A group of chickens that has been developed
in a particular region of the world.
- Cock - A male chicken over one year of age; also called
cock bird and old rooster.
- Cockerel - A male chicken under one year of age; also
called young rooster.
- Crossbred - The offspring of parents of different varieties
- Gallus domesticus - The domestic chicken.
- Gallus gallus - The Red Jungle Fowl; also
called gallus bankiva.
- Genus - A group of closely related animals or plants
which differ from one another in only slight characteristics.
- Hen - A female chicken over one year or age.
- Inbred - The offspring of closely related parents;
resulting from inbreeding.
- Incrossbred - The offspring from crossing inbred parents
of the same or different breeds.
- Layers - Mature female chickens kept for egg production;
also called laying hens.
- Pullet - A female chicken under one year of age.
- Purebred - The offspring of purebred parents that are
of the same class, breed, and variety.
- Roaster - A young meat-type chicken, usually 3 to 5
months of age, of either sex, that can be cooked tender by roasting, and
usually weighing 4 pounds or over.
- Sexed chickens - Day-old chicks with the males and
- Started pullets - Female chickens that are partially
grown, usually to point of lay that is about 20 weeks of age, by specialized
growers for sale to egg farmers.
- Straight-run chicks - Day-old chicks that have not
been separated according to sexes.
- Strain - A group of birds within a variety that has
been bred by one person or firm for some time and has more or less uniform
characteristics and capabilities.
- Strain cross - The offspring of parents of two or more
different strains belonging to the same variety.
- Stewing chicken - A mature female chicken, usually
more than 10 months of age; that requires moist, pressurized, or extended
cooking; also called hen or fowl.
- Variety - A subdivision of a breed, distingushed by
color, color pattern, or kind of comb.
Words about the anatomy of chickens
- Beak - The bird's bill; the protruding mouthpart of
- Cloaca - The vent or common opening in birds through
which the intestinal, urinary, and reproductive tracts empty.
- Comb - The fleshy, red outgrowth on top of a chicken's
head; there are eight types of combs.
- Earlobes - The fleshy patch of bare skin below the
ears varying in size and shape with the color red, white, blue, or purple,
according to the breed.
- Gizzard - An internal organ of birds. It has thick
muscular walls and a tough lining. It crushes and grinds foods by muscular
action and with pebbles or grit.
- Infundibulum - The funnel end of the oviduct that picks
up the yolk when it is released from the ovary; the area in which fertilization
of the true egg takes place; also called funnel.
- Isthmus - The section of the oviduct next to the magnum
where the water and mineral salts are deposited and the inner and outer
shell membranes are formed.
- Magnum - The section of the oviduct next to the infundibulum;
the area in which the thick white is deposited and the shape is formed.
- Ovary - The organ of the female which holds the true
eggs and produces the yolks on which the true eggs are located.
- Oviduct - The organ of the female birds that puts the
albumen, shell membranes, and the shell of the avian egg around the yolk.
- Ovum - The female germ cell; plural form is ova.
- Pituitary gland - A small kidney-shaped gland located
at the base of the brain that produces hormones involved in sexual maturity,
the maturation and release of yolks, and egg laying.
- Uterus - The section of the oviduct next to the isthmus
where final portions of the white and minerals are deposited and shell
and shell pigment are added.
- Vagina - The section of the oviduct next to the uterus
in which the cuticle is deposited on the shell and the eggs are turned
completely around on its long axis so that the large end is laid first.
- Wattles - The fleshy, red growths that hang from the
side and base of the chicken's beak.
- Yolk sac - The follicle where an ovum and its surrounding
yolk are held until the yolk matures and is released.
Words about the avian egg
- Air cell - The air space between the two shell membranes,
usually at the large end of the egg, that can be plainly seen when an
egg is candled.
- Albumen - The white of an egg, consisting of outer
thin, firm, inner thin, and chalaziferous layers.
- Avian egg - The mass of material constituting the bird
egg - the shell, shell membranes, albumen, and yolk - that is designed
by nature to nourish and protect the true egg.
- Blastoderm - A fertilized true egg.
- Blastodisc - A true egg that was not fertilized.
- Chalazae - The two whitish cords on opposite sides
of the yolk that hold the yolk in the center of the albumen and serve
as a rotating axis to keep the germ cell on the top side of the yolk and
next to the heat of the hen's body.
- Cuticle - A secretion of the uterus consisting mainly
of protein that serves to partially seal the pores in the egg's shell
and acts as a lubricant when the egg is laid; commonly called the bloom.
- Egg - The microscopic cell of the female; the true
egg; the female germ cell.
- Fertile - An egg that is fertilized; the capability
of an egg to develop into a chick.
- Fertilization - The act or process of making or becoming
fertile; the union of a male cell with a female cell.
- Infertile - An egg that is not fertilized, will not
- Shell - The hard outer surface of an egg made up largely
of calcium carbonate; the shell has pores allowing loss of carbon dioxide
and moisture from the egg.
- Shell membranes - Two thin membranes next to the shell
and surrounding the albumen and yolk; known as inner and outer shell membranes;
they are one of the egg's chief defenses against bacterial invasion.
- Sperm - The microscopic cell of the male; the male
- Yolk - The round yellow mass upon which the true egg
is located and that provides nutrients for the developing embryo.
Words about incubation and embryology
Compiled by S. F. Ridlen, Poultry Extension Specialist, University of
Illinois at Urbana-Champaign
- Allantois - A sac connected to the emrbyo's abdomen
making respiration by the embryo possible; it also stores excretions,
absorbs albumen used for food by the embryo, and absorbs calcium from
the egg shell for the structural needs of the embryo.
- Amnion - A transparent sac, filled with colorless fluid,
surrounding the embryo; the amnion and amniotic fluid protect the developing
embryo from shock and permit it to exercise.
- Broody hen - A hen that through hormonal changes has
undergone marked changes in behavior and physiology, including cessation
of laying and development of the maternal instincts. A hen that wants
to sit on eggs to hatch them and to brood chicks.
- Chick tooth - A tiny, sharp, horny projection on the
end of the chick's beak used by the chick to peck holes in the shell.
Also known as egg tooth.
- Chorion - A membrane that surrounds both the yolk sac
and the amnion; it has no apparent initial function but later fuses with
the allantois to form the chorio- allantois membrane.
- Down - Soft, fine, hair-like feathers on young birds.
- Embryo - The developing chick within the egg.
- Embryology - The study of the formation and development
- Extra embryonic membranes - Membranes outside the embryo's
body that make respiration, nutrition, and secretion possible and provide
protection; they include the yolk sac, amnion, allantois, and chorion.
- Fertility - The quality or state of being fertile.
- Hatchability - The quality or state of being hatchable.
- Humidity - The amount of moisture in the air in the
incubator; 50 to 55 percent relative humidity is ideal the first 18 days
of incubation and about 65 percent the last three days.
- Incubation - The process of applying heat, either naturally
or artificially, to eggs to cause them to hatch.
- Incubator - An artificially heated container for hatching
eggs. In a still-air incubator the air is not circulated mechanically.
Forced-air incubators have a fan or fans to circulate the air.
- Pip - To break through or peck holes in the shell by
- Primitive streak - A vertical, opaque line where the
embryo begins to grow and develop.
- Set - To put eggs under a broody hen or in an incubator
to hatch them.
- Temperature - The level of heat in the incubator; can
vary from 99 degrees to 103 degrees F. 100.5 degrees F is optimum for
a still-air incubator.
- Turn - The act of changing the position of eggs being
incubated to prevent the embryos from sticking to the shell membranes.