Exam 4: Lecture 49: Avian Digestive Physiology

Question 1

How does digesta travel in avians from beak to vent?

Answer 1

1. Beak & oropharynx
2. Pre-crop esophagus
3. Crop
4. Post-crop esophagus
5. Proventriculus (glandular stomach)
6. Gizzard/Ventriculus (muscular stomach)
7. Duodenal loop
8. Small Intestine (jejunum & ileum)
9. Ceca
10. Large intestine (very short)
11. Cloaca
12. Vent

Question 2

What structure in the avian GIT do we associate with a monogastric stomach?

Answer 2

-Proventriculus (glandular stomach)

Question 3

What sits in the duodenal loop in avians?

Answer 3

-Pancreas

Question 4

What is the oropharynx of birds?

Answer 4

-Combined cavity of mouth & pharynx extending from beak to esophagus

Question 5

What is the purpose of the beak in birds physiologically?

Answer 5

-Decrease particle size by pecking (most important for free-ranging chickens
-Birds scoop water w/ their beak, then will lift their head so water is swallowed by gravity

Question 6

Where is the laryngeal mound and what is contained in it?

Answer 6

-Caudal to the base of the tongue
-Have median slit which is the glottis
-No epiglottis

Question 7

What structures are located in the oropharynx?

Answer 7

-Beak
-Laryngeal mound
-Taste buds throughout

Question 8

What is the purpose of saliva in birds?

Answer 8

-Need to lubricate the food
-Mostly mucus, some amylase secreted within the saliva

Question 9

What is present throughout the entire esophagus?

Answer 9

-Mucus glands

Question 10

What can the esophagus do in birds that is different from other species we have talked about previously?

Answer 10

-Esophagus has the ability to stretch (if you can fit something in the beak, you can eat it)

Question 11

Where is the pre-crop esophagus located?

Answer 11

-Cervical region

Question 12

Where is the crop located?

Answer 12

-Near the thoracic inlet

Question 13

What is the main function of the crop and what happens there digestively?

Answer 13

-Main function: store food (important for when they are rapidly eating)
-Small amount of fermentation (so bacteria present)
-Add mucus for lubrication
-Also important structure for birds that are prey (can eat & run & store that food)

Question 14

Where is the post-crop esophagus located?

Answer 14

-Thoracic region

Question 15

The post-crop esophagus is ____ compared to the pre-crop

Answer 15

short

Question 16

What is pepsin’s main job in digestion?

Answer 16

-Chop up protein
-Acid makes the protein unfold

Question 17

What are the components of the avian stomach?

Answer 17

-Proventriculus -> gastric chamber
-Gizzard (ventriculus) -> mechanical grinding

Question 18

What happens in the proventriculus?

Answer 18

-HCl secreted here
-Pepsinogen secreted -> once exposed to Hal it get converted into active Pepsin

Question 19

What happens in the Gizzard (ventriculus)?

Answer 19

-Muscular structure for grinding
-Very strong muscle
-Small stones & grit will accumulate here to help grind (important for birds that eat a lot of plant material & grain)
-Lined w/ a thick cuticle called “koilin” composed of solid secretions that are continually replaced (help protect from acid & pectin)

Question 20

What happens to the secretions produced in the gizzard (ventriculus)?

Answer 20

-They solidify after being exposed to acid (helps form lining)

Question 21

What is indicated by number 1?

Answer 21

-Gizzard (ventriculus)

Question 22

What is indicated by number 2?

Answer 22

-Proventriculus

Question 23

What is indicated by number 3?

Answer 23

-Duodenum

Question 24

What is indicated by number 4?

Answer 24

-Pancreas

Question 25

What is the main area for absorption of nutrients?

Answer 25

-Jejunum

Question 26

How is the small intestine of avians compared to other mammals?

Answer 26

-Much shorter compared other entire GIT

Question 27

Why is the avian small intestine much smaller compared to other mammals?

Answer 27

-To keep their body weight lower so they can fly

Question 28

What happens in the duodenal loop in avians?

Answer 28

-No lactase produces (lactase helps digest lactose_ -3 pancreatic ducts that drain into distal duodenum (right before getting into jejunum)

Question 29

What is the **meckel's diverticulum**

Answer 29

-Yolk stalk vestige- -Distinction between the jejunum & ileum

Question 30

There are _____ rhythmic gastroduodenal contractions

Answer 30

~3/min

Question 31

What is the sequence of gastroduodenal motility?

Answer 31

1. Contraction of thin ventricular muscles 2. 2-3 peristaltic waves through duodenum 3. Contraction of thick ventricular muscles 4. Peristaltic wave through ventriculus

Question 32

What is the function of the peristaltic waves through the duodenum?

Answer 32

-Help move digesta so it will flow into the duodenum & through

Question 33

What do the contraction of thick ventricular muscles in the gastroduodenum do?

Answer 33

-More for mixing & grinding -Will get some digesta that will reflux back into proventriculus

Question 34

About _____, digesta from the duodenum and upper jejunum refluxes into ventriculus

Answer 34

4 times/hour

Question 35

What is the role of ceca in the avian?

Answer 35

-Important for water reabsorption -Urine from cloaca refluxes into ceca via anti-peristalsis -Uric acid will provide Nitrogen for bacteria -Well- developed villi at the folds to help exclude large particles -> only allow liquids into ceca

Question 36

How are the paired ceca separated from the ileum?

Answer 36

-by ileocecal folds

Question 37

Paired ceca are not present in

Answer 37

hawks or songbirds

Question 38

Paired ceca are important in some wild fowl for

Answer 38

microbial fermentation of cellulose

Question 39

The large intestine in avians is primarily for

Answer 39

water reabsorption

Question 40

What is the cloaca?

Answer 40

-Common opening for digestive, reproductive, urinary systems -Excrete feces & urine together

Question 41

Urine in birds contains

Answer 41

uric acid (instead of urea)

Question 42

What is the vent?

Answer 42

-Opening to exterior

Question 43

What is the bursa of Fabricius?

Answer 43

-Structure that has some immune function

Question 44

What is indicated by the blue star?

Answer 44

-Bursa of fabricus

Question 45

What does antiperistalsis in the colon do?

Answer 45

-Moves urine from cloaca to ceca & colon -10-14 antiperistaltic contractions/minute -Ceases before defecation

Question 46

What do the major & minor cecal contractions do?

Answer 46

-Series of major contractions = cecal evacuation -One major contraction = defecation -Minor contractions = mixing

Question 47

How many lobes are in the avian liver?

Answer 47

-Bi-lobed

Question 48

What avian species have a gallbladder?

Answer 48

-Gallbladder in chickens, turkeys, ducks, geese -Not in pigeons

Question 49

What is in each lobe of the avian liver?

Answer 49

-Each lobe has a bile duct draining into duodenum near pancreatic ducts (3 pancreatic ducts)

Question 50

How do cecal droppings look?

Answer 50

-Chocolate brown color, homogeneous texture

Question 51

How many cecal droppings are there per day?

Answer 51

-1-2 cecal droppings per day

Question 52

What is associated with cecal evacuation? (cecal droppings)

Answer 52

-Series of major cecal contractions

Question 53

How do intestinal droppings look?

Answer 53

-Greenish, granular-texture

Question 54

How many intestinal droppings are there per day?

Answer 54

-25-50

Question 55

What is the white pasty material on intestinal droppings?

Answer 55

-Uric acid crystals

Question 56

What type of droppings are these?

Answer 56

-Cecal droppings

Question 57

What kind of droppings are these?

Answer 57

-Intestinal droppings

Question 58

What is the energy for developing avian embryo?

Answer 58

-Provided by lipids stored in yolk -Occurs by lipid transfer from yolk to blood

Question 59

How does lipid transfer from yolk to blood?

Answer 59

-Happens by endocytosis by endodermal cells in yolk membrane -Lipids packaged into lipoproteins then go into blood

Question 60

Yolk is ____ lipid

Answer 60

~50% (so a lot of energy in that egg yolk)

Question 61

What happens to the yolk material after hatching?

Answer 61

-Yolk material secrete through yolk stalk into SI for ~3 days after hatching -Peristalsis & antiperistalsis deliver material throughout SI and gizzard

Question 62

The yolk becomes the

Answer 62

merkel's diverticulum

Question 63

What is most efficient for commercial poultry based on digestive anatomy?

Answer 63

-Highly digestible starch & protein diets

Question 64

What diets will not be well-digested in poultry?

Answer 64

-High fiber diets will not be well-digested -However, free-ranging chickens will consume some fiber

Question 65

How can impacted crop (also known as crop binding, pendulous crop) occur?

Answer 65

-Can happen when they eat too much grass or fibrous tissue, if they go a long time w/out eating & then eat quickly -Food doesn't move (could be from too much fiber or too much food) -Can also have a lack of normal muscle contractions (can also be Marck's disease)

Question 66

What is sour crop?

Answer 66

-Overgrowth of yeast in crop -> disrupts normal bacteria -Can get dilation of crop or thickening of wall -Causes very bad breath

Question 67

Which structure in the avian GIT is analogous to the gastric stomach? A. Crop B. Proventriculus C. Gizzard (ventriculus) D. Post-crop esophagus

Answer 67

B. Proventriculus

Question 68

What compound do birds excrete to eliminate Nitrogen from the body?

Answer 68

-Uric acid