Avian Anatomy and Physiology Flashcards
What is the purpose of the digestive system?
To keep the host nourished and healthy
How is the avian digestive system different than mammals?
It is faster and more efficient?
Why are the two reasons the avian digestive system is faster and more efficient than other vertebrates?
1.) Birds cannot afford to store heavy food materials in their bodies for long periods of time since they need to minimize weight for flight
2.) Because of flight, because they’re small (lose heat more rapidly), and because they’re warm blooded, they use a lot of energy, so digestion needs to act quickly to supply this
How long does it take a shrike to digest a mouse and a robin to digest fruit?
Shrike -> 3 hours
Robin -> 30 minutes
What is the most common activity done by birds during the day?
Eating and foraging
When is most foraging done?
Mornings and evenings
What type of feeders are birds?
Opportunistic feeders
What is another name for the gastrointestinal tract?
The alimentary canal
What is the gastrointestinal tract and what does it span in birds?
The entirety through which food passes
Spans beak to cloaca
What is the difference between a bill and a beak?
A beak is a curved bill
What are the main functions of the bill/beak?
Grabbing, tearing, crushing, holding, and swallowing food
How does the avian jaw differ between mammals and avians?
The avian jaw is somewhat mobile, meaning it can extend upward
What allows for the different positions and mobility of the jaw?
Lateral and longitudinal dexterity
The beak is able to do what with a big meal?
Hold or receive it
What are examples of when form and function are important?
Structure, dietary preferences, adaptation, and environment
What is the avian mouth made of?
A hard palate divided by a long narrow slit that acts as an opening to the nasal passage
What is the long narrow slit in the avian mouth called?
Choanal slit
The choanal slit, coupled with what, makes it impossible for birds to do what?
The choanal slit and the absence of a soft palate make it impossible for birds to create a vacuum to draw food or water into their mouths
.
They can’t use straws, so they need to draw water in by moving their head
What are characteristics of the avian tongue?
It is hard, short, narrow, and triangular
How does the number of taste buds in avians compare to mammals?
Avians have very few compared to mammals and they are situated mostly in the back of the mouth/throat for avians
What tastes can birds perceive?
Sweet, sour, and bitter
How do birds utilize flavor?
To learn which foods are more nutritious
In terms of food, what do birds prefer?
Texture over flavor
What do birds have on their tongue and palate and how do they use them?
A complex system of touch receptors that they use to make food-based decisions based on how something feels
What is the most under-developed sense in birds?
Smell
What is the esophagus?
A long, thin, tubular muscle that connects the mouth to the stomach
Why do most birds have well developed salivary glands?
To lubricate food entering the esophagus
What are under-developed or absent in aquatic birds?
Salivary glands
What is an enlargement of the esophagus that many birds have?
The crop
Where is the crop located?
Midpoint of the esophagus
What is the function of the crop?
It is a food and water storage organ
What type of mentality does the crop enable?
Dine and dash
What does the crop do besides storage?
Meters contents into the digestive tract
What type of digestion occurs in the crop?
A very small amount of salivary enzyme digestion
What is characteristic of a pendulus crop?
When it hangs and swings
If there is slow passage through the crop and food stays there longer than it should, what happens?
Micro-organisms begin to live there and create gas, which causes the crop to bloat
What do birds have a more efficient stomach than?
Reptilian ancestors
What type of stomach do birds have?
A complex two-part stomach
What are the two parts of the stomach?
Proventriculus and gizzard
What is characteristic of the proventriculus?
It is a soft-walled glandular tube
What do the epithelial mucosa in the proventriculus secrete?
HCl (lowers pH), digestive enzymes, and mucus
What does the proventriculus do?
Initiates the breakdown of food
What type of bird has a stomach with a pH below 0.1?
Carcass eaters, like vultures
What is another name for the gizzard?
Ventriculus
What is characteristic of the gizzard?
It is a hard/thick-walled organ that has a sand-paper like inner surface
What does the gizzard do?
Performs mastication (what chewing does)
Why do some birds swallow stones?
To help breakdown food in the stomach
What happens to the gizzard in birds that feed on easily digestible foods like fruits and berries?
It is reduced in size and function
When the gizzard is greatly reduced, what is the stomach almost completely comprised of?
Glandular proventriculus
Rank in decreasing order the diets that a chicken can be fed that would result in the greatest sized gizzard
Raw diet > pellet diet > mash diet
What happens in the small intestine?
Food is digested and absorbed
How does the small intestine vary among avians?
Varies in length and structure depending on preferred diet of the species
What type of birds have a shorter small intestine, and which type’s is larger?
Carnivorous birds have a shorter small intestine and omnivorous and herbivorous birds have a longer small intestine
How does the avian small intestine compare with the mammalian short intestine?
It is relatively featureless when compared to the mammalian SI consisting of the duodenum, jejunum, and ileum
What is the duodenum?
The intestinal loop around the pancreas
How are the liver and pancreas connected to the duodenum?
By ducts
How does the liver compare with mammals?
Liver is larger in birds
What does the liver do?
It stores fats and carbs and is the major site of protein synthesis
What receives the most nutrients from the small intestine before other body tissues?
Liver
What does the duodenum contribute?
Bile, pancreatic enzymes, and neutralization of gastric juices
What does bile do?
Emulsifies fats
What do pancreatic enzymes do?
Aide in digestion
What do the jejunum and ileum provide?
Peristalsis and absorption of nutrients
When nutrients are absorbed via the jejunum and ileum, where do they go?
They are absorbed into mesenteric veins and enter the portal hepatic system
What, specifically, is the jejunum?
The intestine located between the duodenum and Meckel’s diverticulum
What, specifically, is the ileum?
The intestine located between Meckel’s diverticulum and the ileocecal junction
What is Meckel’s diverticulum?
Vestigial remnant of the vitelline duct or yolk sac that is the junction between jejunum and ileum
What is the ileocecal junction?
Where the ileum and ceca meet
What are the ceca?
Two pouches located at the junction of the small and large intestine
What takes place at the ceca?
Water re-absorption and fermentation of remaining food materials
What does the ceca produce in chickens?
Several fatty acids and 8 B-vitamins
How do the ceca vary?
Vary in size and functionality depending on diet preference of bird species
Why is microflora present in the ceca?
Because of the presence of fiber and other undigested materials
Describe the GI tract of a red-tailed hawk and explain
Short small intestine with very small ceca
Short SI because carnivore, small ceca because not much fiber in carnivore diet)
Describe the GI tract of a hoatzin and explain
Large crop and foregut because herbivorous and a lot of fermentation ocurrs
Most birds have a very small large intestine, what bird has a long intestine?
Ostrich
In species with a relatively small ceca, what can help compensate this?
An expanded foregut, like in hoatzins, a larger midgut, like in emus, or a longer colon, like in ostriches
What are two other names for the large intestine?
Colon and rectum
What has the large intestine been reduced to in most birds?
A short, featureless connection between the small intestine and the cloaca
What happens at the large intestine?
Water reabsorption
What is the function of the cloaca?
It’s the final holding site of waste products
What is the urinary waste of birds?
Urates, not urine
What are the roles of the respiratory system?
1.) Absorption of CO2
2.) Release of CO2
3.) Vocalization
4.) Temperature regulations
5.) Helps with rapid adjustments to acid/base balance
What is the second most efficient respiratory system in the animal kingdom (and what’s first)?
Avians have the second most efficient respiratory system in the animal kingdom, second only to insects
What is the most common cause of death in poultry flocks?
Respiratory disease
What is another name for the larynx?
Glottis
What is the larynx?
An opening to the trachea/windpipe
In terms of the respiratory system, what does the choanal slit/cleft do?
Allows for breathing through the nostrils when the beak is closed
What does the choanal slit connect?
Trachea to the sinuses and nares
How does the choanal slit relate to the immune system?
It’s where the first exposure of food and water to the immune system takes place
How do the glottis and choanal slit relate when the mouth is closed?
The glottis fits into the choanal slit
What is another name for the trachea?
Windpipe
What is the trachea?
A hollow tube that provides airflow to/from the lungs for respiration