1. Avian Anatomy

2. Skeletal System
Skeleton is very unique and specially adapted for flight
Very lightweight; yet strong
Most of the long bones are hollow but reinforced through a honeycombed structure
Flying species have a large keel
Keel - place on the sternum that the flight muscles attach

4. Respiratory System Different from mammals in many ways.
Bird respiration is much more efficient.
Birds do not have a diaphragm. In mammals this moves up and down to increase and decrease the chest cavity.
Birds push the sternum in and out to the same effect
Hummingbird breathes 143 times per minute while a turkey breathes 7 times per minute
Rate increases during flight.

5. Breathing Cycle
Bird lungs are very compact and take up much less space than mammal lungs
The air enters through the nostrils, down the trachea and into the lungs and air sacs
Thin-walled air sacs extend through the body cavity and even into the bones
Birds can keep a continuous flow of air through the lungs.

7. Digestion
Birds has special digestive tracts because they do not chew their food
First the food travels down the esophagus and into the crop.
The crop is an expanded section of the esophagus.
It is used as a holding tank for food before it can enter the proventriculus
The proventriculus produces acid and adds enzymes which aid in breaking down the food

8. The gizzard helps grind food like seeds
The gizzard is highly keratinized to make the surface rough
Turkey gizzard can crush walnuts and steel needles
Food then passes through the intestinal tract, where nutrients are absorbed
Waste is expelled through the cloaca, or vent.

9. Digestion

11. Reproductive Tract
The reproductive organs shrink whenever birds are not in breeding season
This decreases their weight
Males have 2 testes and females have 1 ovary
Eggs production:
The ovum is fertilized and passes through a long tube called the oviduct
Each section of the oviduct adds a different part to the egg, just like an assembly line

12. The egg assembly
In the infundibulum the egg stays 20 minutes before going to the magnum where the egg white is added
Next the egg goes to the isthmus, where inner and outer membranes are formed
This process takes about 1 hour
In the uterus the shell and all pigments are added (20 hrs)
The egg then passes out the cloaca