avian digestion and nutrition

Question 1

what is important to consider when dosing birds

Answer 1

have higher metabolic rate

Question 2

outline the pathway of the digestive system of birds

Answer 2

1. crop
2. pro ventriculus
3. gizzard
4. small intestine
5. large intestin

Question 3

discuss the beak

Answer 3

• instead of lips and teeth bird have beaks consisting of bone, vascular dermis with a modified keratinised germinal layer
• covered with leathery keratin
• high density of mechanoreceptors
• epithelium has thick stratum corneum to give hardness to beak
• upper jaw is rigid block made up of the premaxillary and nasal bones and a small maxilla.
• the articulation of the upper jaw and cranium is an elastic zone, though in larger birds it is a synovial joint
• newly hatched chicks have an egg tooth
• size and shape varies by functon

Question 4

discuss the avian oropharynx

Answer 4

• no soft palate, oral cavity or pharynx. just oropharynx
• connection between nasal cavity and oropharynx, midline of the hard palate - choana
• caudal to choana, infundibular cleft (common opening for the pharyngotympanic tubes = avian eustachian tubes)
• hyoid supports keratinised tongue
• tubular salivary glands release mucin and in some species amylase

Question 5

how do birds swallow

Answer 5

• papillae present in oropharynx directed caudally move food in conjunction with tongue and gravity (tip heads back)
• no peristalsis

Question 6

discuss the avian esophagus

Answer 6

• dilates to accommodate unmasticated food
• lies to the right side of the neck nd is under vagal control

Question 7

discuss the crop

Answer 7

• varies from small pouch to large structure with basic sphincter
• lies cranial to thoracic inlet
• histologically similar to the esophagus except for the scarcity of mucus glnds
• food storage
• degradation of starch and fermemtation in the grop (candida spp)

Question 8

what is sour crop

Answer 8

overgrowth of candida spp whith swollen mucus membranes and impacted feed

Question 9

discuss teh mechanics of the crop

Answer 9

• there is a peristaltic movement in the esophagus to crop
• emptying of the proventriculus stimulates crop to move food caudally
• ## motility regulated by vagus

Question 10

whic parts of the avian GIT are glandular and non-glandular

Answer 10

proventriculus = glandular
gizzard = muscular = grinds food

Question 11

discuss the proventriculus and gizzard

Answer 11

• both sections are similar in carnivorous birds
• lies to the left in the craniodorsal body cavity.
• no esophageal sphincter
• between proventriculus and gizzard is the isthmus (thin walled and non-glandular)
• seed eaters need a muscular gizzard for grinding
• proventriculus produces HCl and pepsinogen from oxynticopeptic cells for chem digest

Question 12

describe the anatomical position of the gizzard

Answer 12

• left of midline
• caudal to sternum
• protein digestion
• mechanical food breakdown
• smooth muscle

Question 13

what is kiolin

Answer 13

• tough lining of the gizzard
• protects mucosa
• formed from mucosal cell secretions
• composed of protein and carbohydrate
• stained tellow with bile reflux from the duodenum

Question 14

discuss how egestion occurs

Answer 14

• small particles move on to duodenum
• large particles stay in gizzard or are regurgitated
• during reflux gastric motility is inhibited and pellet expelled through mouth by esophageal antiperistalsis

Question 15

what is merkels diverticulum

Answer 15

a vestige of the yolk sac marks the boundary between ileum and jejunum