Internal Anatomy of Chicken Animal Science

1. Animal Science 1
(Introduction to
Animal Science)

2. Anatomy
of Chicken

3. Digestive
tract of
female
Chicken

4. Beak/Mouth
• A chicken obtains feed by
using its beak. Food
picked up by the beak
enters the mouth. Chickens
do not have teeth, so they
cannot chew their food.
• Mouth contains glands that
secrete saliva, which wets
the feed to make it easier
to swallow. Also, the
saliva contains enzymes,
such as amylase, that
start the digestion
process.
• The chicken uses
its tongue to push the
feed to the back of the

5. Crop
• The crop is an out-
pocketing of the
esophagus and is
located just outside
the body cavity in
the neck region.
• Swallowed feed and
water are stored in
the crop until they
are passed to the
rest of the
digestive tract.
• When the crop is
empty or nearly
empty, it sends

6. Esophagu
s
• The esophagus is a
flexible tube that
connects the mouth
with the rest of
the digestive
tract.
• It carries food
from the mouth to
the crop and from
the crop to the
proventriculus.

7. Proventricul
us
• The esophagus continues
past the crop, connecting
the crop to the
proventriculus.
• The proventriculus (also
known as the true stomach)
is the glandular stomach
where digestion primarily
begins. Hydrochloric acid
and digestive enzymes, such
as pepsin, are added to the
feed here and begin to
break it down more
significantly than the

8. Ventriculus
(Gizzard)
• The ventriculus, or
gizzard, is a part of the
digestive tract of birds,
reptiles, earthworms, and
fish.
• The gizzard is made up of
two sets of strong
muscles that act as the
bird’s teeth and has a
thick lining that
protects those muscles.
• Consumed feed and the
digestive juices from the
salivary glands and
proventriculus pass into

9. Pancreas
• Pancreas creates
natural juices
called pancreatic
enzymes to break
down foods.
• These juices travel
through your
pancreas via ducts.
• The upper part of
your small intestine
called the
duodenum.

10. Spleen
• The spleen is the
largest peripheral
lymphoid organ in
chickens, and it
plays a significant
role in
both antibacterial
and antiviral immune
responses against
acquired antigens.

11. Gall
bladder
• The gall bladder,
which stores the bile,
is a thin-walled
muscular green sac found
on the ventral surface
of liver.
• The liver is the source
of the bile which plays
an important role in the
emulsification of
dietary fats, an
essential step in fat
digestion and
absorption.

12. Small
Intestine
• The small intestine is made
up of the duodenum (also
referred to as the duodenal
loop) and the lower small
intestine.
• The remainder of the
digestion occurs in the
duodenum, and the released
nutrients are absorbed
mainly in the lower small
intestine.
• The duodenum receives
digestive enzymes and
bicarbonate (to counter the
hydrochloric acid from the
proventriculus) from the

13. Large Intestine
(Colon)
• The large
intestine is
actually shorter
than the small
intestine.
• The large
intestine is where
the last of the
water reabsorption
occurs.

14. Ceca
• The ceca (plural form
of cecum) are two blind
pouches located where the
small and large intestines
join.
• Important function of the
ceca is the fermentation
of any remaining coarse
materials.
• During this fermentation,
the ceca produce several
fatty acids as well as the
eight B vitamins
(thiamine, riboflavin,

15. Cloaca
• In the cloaca, the
digestive wastes mix with
wastes from the urinary
system (urates).
• Chickens usually void fecal
material as digestive waste
with uric acid crystals on
the outer surface.
• The color and texture of
chicken fecal material can
indicate the health status
of the chicken’s digestive
tract: the white, pasty
material coating chicken
fecal material is uric
acid, the avian form of

16. Reproductive
tract of Hen

17. Ovary
• Organ in which
yolk formation
occurs: yolk is
formed in the
follicular sac
ovarian follicle
by the
deposition of
continuous
layers of yolk
material.

18. Oviduct
• The egg moves through the
oviduct for about 22
hours. It undergoes a
number of modification.
• First a thickened outer
layer is applied to the
vitelline membrane, which
has two cord-like
extensions, chalazae,
which anchor the yolk in
center of the egg and
stabilize.

19. Infundibulum
• Also called funnel;
the first section of
the oviduct that
quickly engulfs the
yolk with its thin,
funnel-like lips.

20. Magnum
• After passing the
infundibulum the yolk
quickly enters the magnum
section.
• The albumen is applied to
the outer surface of the
egg providing water,
nutrients, and antibiotic
agents.
• The magnum is separated
from the isthmus by a
narrow, translucent ring
w/out glands.

21. Isthmus
• Is smaller in diameter
than the magnum. It is
here the two shell
membranes are added.
• The membranes touch each
other throughout the egg,
except at the blunt end
of the egg, where the air
cell is formed later
because the egg content
cools down and contracts
after laying.

22. Uterus
• Also called shell gland.
• The calcite crystals are
deposited in and over the
out shell membrane layer
to form the eggshell.

23. Vagina
• A thin, protein coating
called “bloom” is applied
to the shell to keep
harmful bacteria or duct
from entering the egg shell
pores.
• The egg is turned
horizontally (the process
called oviposition) just
before laying so that egg
will exit blunt end first.

24. Thank
you!!!

25. References:
National Institute of Food and
Agriculture. U.S. Department of
Agriculture. (2023). Dr. Jacquie
Jacob, University of Kentucky.