Lecture 8 - Avian digestion

Question 1

Major proponents of the chicken digestive tract

Answer 1

Crop -> proventriculus -> gizzard -> pancreas -> SI -> LI (ceca) -> cloaca

Question 2

Oral/pharyngeal differences in birds

Answer 2

No teeth
Beak
Lots of saliva
No epiglottis
Few tastebuds

Question 3

How is the esophagus distinct?

Answer 3

Large in diameter

Question 4

What is the crop? Fxn

Answer 4

Esophageal pouch NOT stomach
Storage
Can have none, one, or two

Question 5

What is the proventriculus

Answer 5

Glandular stomach
Secrete mucus, pepsinogen, acid
Storage in some species

Question 6

What is the gizzard

Answer 6

Muscular stomach
Mechanical digestion
Use grit

Question 7

How is the gizzard protected

Answer 7

Lined with thick cuticle (koilin)

Question 8

What is koilin

Answer 8

CHO protein complex
Mucosal secretions solidify on surface when exposed to low pH
Protect against acid

Question 9

Left vs right hepatic (liver) ducts

Answer 9

Left drains into duodenum
Right leads to gallbladder, then bile duct and duodenum (not all have gallbladder)

Question 10

How does the SI differ

Answer 10

No lymphatic system; fat absorbed to blood capillaries (to liver)
Meckel’s diverticulum (yolk sac vestige)
Ileocaecal junction is circular muscle (not same as sphincter)

Question 11

Describe the LI

Answer 11

Paired ceca (small amount feed digested here 10%)
No separation among LI, colon, rectum
SHORT
Cloacal bursa

Question 12

How is glucose absorbed

Answer 12

Mostly in duodenum/jejunum, facilitated diffusion

Question 13

How are TG packed once absorbed

Answer 13

Portomicrons

Question 14

What happens in the cecum

Answer 14

Active absorption of glucose
Amino acids absorbed

Question 15

What fills first after eating food

Answer 15

Ventriculus

Question 16

What happens once the ventriculus is filled

Answer 16

Tonic contraction of crop relaxes
Contractions in ventriculus send back into proventriculus and into duodenum

Question 17

How do birds contraction cycles work

Answer 17

1. thin muscles of gizzard contract (2-3 peristaltic waves through duodenum)
2. thick muscles of gizzard contract (1 peristaltic wave passes through proventriculus)

Question 18

What is orad movement

Answer 18

Reflux of duodenal contents into the gizzard
Egest a pellet of bones and feather

Question 19

Migrating motor complex occur in what state

Answer 19

Fed and fasted (pig = just fasted)

Question 20

Anti-peristaltic contractions in birds

Answer 20

Arise from the cloaca 10-14 times/min
Not during defecation
Move urine from cloaca into colon and ceca to absorb water

Question 21

When do birds stop feeding

Answer 21

Response to distention of gizzard
Glucose receptors in crop/intestine
Amino acid receptors in intestine

Question 22

What can birds detect with regards to aa

Answer 22

Subtle differences in protein content and composition
e.g. methionine adequate vs excess/deficient

Question 23

Birds have mucous glands in

Answer 23

Esophagu

Question 24

Found in crop…

Answer 24

Bacterial fermentation
Free glucose

Question 25

Gastric secretions

Answer 25

Mucus, HCl, pepsinogen

Question 26

Differences in digestion

Answer 26

No lacteals (fat to liver w other nutrients)
Cecum transports aa/glucose
Water absorption major fxn of ceca (includes urine)