The Egg Story
What do we know?
 EGGS
CHICKENS
Vocabulary – PICK 15
AND DEFINE
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lay
brood
fowl
class
hatch
embryo
poultry
breed
pip
egg
tooth
rooster
variety
egg development
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chicken
bantam
beak
fertilized
hen
comb
yolk
chick
down
shanks
white
Nest
feathers
wattles
Shell
clutch
wings
Activities – pick one with a partner and
complete
 Using the vocabulary you
just learned, make a collage
with pictures you find in
magazines or the internet
to describe the words.
 Using the vocabulary you
just learned, write a song,
poem or rap
Incubation
 Eggs have been incubated by artificial means for thousands of
years. Both the Chinese and the Egyptians are credited with
originating artificial incubation procedures. The Chinese
developed a method in which they burned charcoal to supply
the heat. They also used the hot-bed method in which
decomposing manure furnished the heat. The Egyptians
constructed large brick incubators which they heated with
fires right in the rooms where the eggs were incubated.
Incubation continued…
 Over the years incubators have been refined and developed
to the point where they are almost completely automatic.
The greatest development has occurred in the 20th
century.
 Modern commercial incubators are heated by electricity,
have automatic egg turning devices, and are equipped with
automatic controls to maintain the proper levels of heat,
humidity, and air exchange. Present-day commercial
incubators vary in capacity from a few thousand to many
thousands of eggs, and they have made possible the
development of modern hatcheries which produce almost
100 percent of all the chickens grown in this country.
What is an egg? vocabulary
 Shell
 porous
 membranes
 air cell
 albumen
 vitelline membrane
 yolk
 germinal disc or blastoderm
 chalaza
What is an egg?
Once you draw and label the
above drawing in your notes,
please go to the following
website: www.aeb.org
and click on the egg industry
link, watch the following
videos:
-The Egg
- The Hen
-Egg Farm
-Egg Processing
Also be sure to take notes
during each video!
Reproductive tract of a hen
The egg is formed by a reproductive system
composed of an ovary and an oviduct.
An ovary looks like a cluster of grapes and
may contain up to 4,000 small eggs or ova
(singular ovum) which can develop into yolks.
Each ovum is attached to the ovary by a thin
membrane sac or follicle.
The oviduct is a large, coiled tube located in
the left side of the hen’s abdomen. In this
oviduct all parts of the egg, except the yolk,
are formed.
It is divided into 5 distinct regions:
- infundibulum
- magnum
- isthmus
- uterus
- vagina
Chick development
Chick Development
DAY 1
 18 hours – the digestive system starts to appear
 20 hours – the vertebral column starts to appear
 21 hours – the nervous system and brain begin to
form
 22 hours – the head begins to form
 23 hours – the extraembryonic blood systems
begin to form
 24 hours – the eyes begin to form
DAY 2
 25 hours – the heart begins to form
 35 hours – the ear pits begin to form
 37 hours – the amnion starts to appear
 42 hours – the heart starts to beat
 46 hours – the throat begins to form
Extra Embryonic Blood System
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The yolk sac surrounds the yolk and draws food from it for the embryo. The amnion is a
transparent sac filled with a colorless fluid in which the embryo floats that protects it from shocks
and prevents it from drying out.
Respiration is made possible by the allantois. As it grows with the chick, the allantois is pressed
against the egg shell where it can easily absorb oxygen passing through the pores of the egg shell
in exchange for carbon dioxide. The allantois also stores waste, absorbs albumen used as food by
the embryo and absorbs calcium from the shell for bone construction. For the first 10 days the
chick can absorb a sufficient amount of calcium from the yolk but as the formation of bones begins
to accelerate the chick must take calcium from the egg shell.
There are two distinct extraembryonic blood systems: Blood vessels in the allantois called
allantoic vessels which bring oxygen to the embryo and take carbon dioxide away. The other
blood system made of vitelline vessels brings nutrients from the yolk to the embryo. During the
first 3 days of its life, the chick relies on the vitelline vessels to also absorb oxygen but by the 4th
day the chick needs more oxygen than can be supplied by only the vitelline system and begins to
rely on the allantois which will soon take over respiration.
Heart and Circulatory System
• average body temp. is 98.6 F
•4 chambers
• cardiac muscle
• valves
• higher metabolic rate
• average body temp. is 106 – 113 F
•Pulse rate 400 beats/minute
•Smoother chambers of the heart
Chick Development
DAY 3
 50 hours – the amnion begins to
form
 60 hours – the nose begins to form
 62 hours – the legs start to appear
 64 hours – the wings start to
appear
 70 hours – the allantois begins to
form
Day 4
•The tongue begins to form
•The tail appears
•The toes begin to form
•Extra-embryonic
circulation is fully
functional
DAY 5
- The crop begins to form
- The bones of the legs begin
to form
- The sex of the chick is
determined and its
reproductive organs begin to
form(ovary & oviduct for the
female as studied
in Part III)
Chick Development
 Day 6
 The beak and egg-tooth begin to
form
 The ribs start to appear
 The gizzard begins to form
 Voluntary movement begins
 Day 7
 The wings bend at the elbow
 and the leg at the knee
 The toes are visible
 The abdomen is bigger as
 the intestine starts to loop
Chick Development
 Day 8
 The feathers begin to form
 The eye lids begins to form
 Day 9
 The mouth opening
appears
 The claws begin to form
Chick Development
 Day 11
 The toe claws begin to curve
downwards
 The bottom of the feet become
padded
 The chick begins to take calcium
 from the eggshell
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Day 10
The beak starts to harden
The comb is visible
The flight feathers develop
Chick Development
 Day 12
 Scales appear on the lower legs
 The chick continues to grow and
move
 Day 13
 Body fairly well covered with
feathers
 The left and right collar bones join
 to form the wishbone
Chick Development
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Day 14
The embryo turns its head towards
the large end of the egg
The skull and ribs have begun to
ossify
 Day 15
 The scales, claws and beak are
becoming firm
Bones and the skeleton
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Bones are made of minerals, mostly calcium
and phosphate. There are 3 types of bone
cells: osteoblasts, osteocytes and
osteoclasts.
Osteoblasts are responsible for making
the structure and then laying in the minerals.
Osteocytes are responsible for feeding
the bone and osteoclasts help shape the
bones as they grow.
New bone is first created randomly and then
reshaped in concentric layers like the rings of a
tree. Bone can be either compact or spongy.
Compact bone on the outside provides
strength, support and protection.
Spongy bone on the inside allow the
bone to be lightweight and provide a space in
which bone marrow can grow.
Bone marrow makes blood cells.
Bones and the skeleton
 What is cartilage?
 Cartilage is a strong but flexible material like hard rubber.
In the embryo, most of the skeleton is first made of cartilage.
As the embryo grows, the cartilage is replaced by bone. This is called
ossification.
 How are bones different in birds?
 Bird bones contain air sacs and are said to be pneumatized.
When a bird takes off for flight the exaggerated movement of
the wings creates an air current which fills the air sacs within the
bones and makes the bird light enough to fly. The bones do not
become pneumatized until after the bird hatches.
Chick Development
 Day 16
 The chick is fully covered with
feathers
 The albumen is nearly gone and
the yolk
 is increasingly important as
nourishment
 Day 17
 The chick turns its beak towards
the air cell
 and begins preparation for
hatching
Chick Development
 Day 18
 The growth of the embryo is
nearly complete
 The amnion which protects
the chick
 begins to disappear
 Day 19
 The yolk sac begins to enter
the body
 The chick occupies all the
space in the egg
 except the air cell
Respiratory System
The lungs are not used for
respiration until just before the
chick hatches. In the meantime
we have seen that the chick uses
the allantois to breathe.
The amount of oxygen supplied
through the egg shell is enough
until the chick starts the
exhausting process of hatching.
During incubation, the water
which evaporates from the egg is
replaced by air which is stored in
the air cell. By the time the chick
begins to hatch, the air cell has
grown to fill about 25% of the
egg.
The chick’s first hatching movements are to break the shell membranes covering the air cell
and take its first breaths with its lungs. The oxygen stored in the air cell is enough to allow the
chick to break through the eggshell.
 The bird’s lungs are
How birds breathe
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relatively small in
proportion to its body
size compared to humans;
they are only half the
size.
Human lungs are made
up of millions of tiny
balloons called alveoli
which expand and
contract as we breathe.
A bird’s lungs are not
elastic, they do not
change in size when the
bird breathes.
Specialized elastic
structures called air sacs
are connected to the
lungs and draw air
through the lungs.
As air passes through the
lungs oxygen in the air is
exchanged for carbon
dioxide in the blood.
How Birds Breathe
 Birds have two sets of air sacs: - caudal air sacs - cranial air sacs
 The caudal air sacs include the abdominal and the caudal thoracic air sacs.
 The cranial air sacs include the cervical, clavicular and the cranial thoracic air sacs.
 As we know air sacs even extend into the bones. Air sacs inflate or deflate when the size of the
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bird’s chest changes. The bird controls this by moving its muscles. The largest of the air sacs, the
abdominal air sac surrounds the abdominal organs and is largely responsible for breathing while
the bird is at rest.
As a bird becomes more active, it needs more oxygen. Increased movement forces its chest to
expand and compress more which in turn inflates and deflates more of its air sacs. This forces
more air through the lungs and makes the bird less dense. When a bird flies all its air sacs are
filled including those in its bones and makes it light enough to fly.
A bird can also use its air sacs to sing by forcing air through its vocal organs like a bagpipe.
Some birds can sing while they fly because they are able to sing when they breathe in as well as
breathe out.
Constant airflow supplies birds with more oxygen than humans. This is necessary to maintain
their high metabolic rate and for flying.
The lungs of the chick begin to form early to be ready when it hatches. Air sacs continue to
develop long after the chick has hatched.
Chick Development
 Day 20
 Day 21
 The yolk sac is completely
 The neck begins to jerk
drawn into the body
 The beak breaks through
the inner shell membrane
 The lungs begin to function
and to use the air cell for
breathing
 The allantois ceases to
function and starts to dry
up
 The egg tooth pips through
the shell
 The chick hatches!
How the chick hatches
 Using its egg tooth (a tiny sharp horn on the top of its beak)
the chick pecks at the shell thousands of times. Finally it pips through
the shell and begins to breathe air directly from the outside. After it has
made a hole in the shell, the chick stops piping for a few hours and
rests while its lungs are getting used to the outside atmosphere.
 There is a high level of carbon dioxide in the egg compared with the
outside environment. This actually causes the neck muscles of the chick
to jerk and allow him to peck through the eggshell.
 After resting the chick continues to pip by beginning to turn slowly
inside the egg. As it turns, usually counter-clockwise, the egg tooth
continues to ship away. In about 5 hours, the chick has made about three
quarters of a turn inside the egg.
 As the chick moves around the shell it begins pushing on the egg cap.
Squirming and struggling the chick pushes the cap for about one hour.
Finally it breaks free from the shell,still wet and panting.
How the chick hatches
 When the chick is
completely out of the
shell it lies still.
 It is extremely tired.
After a rest it begins
to rise to its feet and
gain coordination.
 Within a few days the
egg tooth will
disappear.
Common Breeds of Chicken
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Ancona
Araucana
Australorp
Brahma
Bantam
Campine
Cochin
Frizzle
Houdan
Leghorn
Minorca
New Hampshire Red
 Orpington
 Plymouth Rock
 Polish
 Rhode Island Red
 Rosecomb
 Sicilian Buttercup
 Silkie
 Sultan
 Sumatra
 Sussex
 Transylvanian Naked Neck
 Wyandotte