Questions and Answers
What is the primary function of the gizzard in birds?
What is the term used for the dilation of the esophagus that holds food?
crop
The tongue of birds is highly muscular.
False
The large intestine terminates at the ______.
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Which part of the small intestine is known to have a significant amount of lymphoid tissue?
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What layer of tissue is the wall of the esophagus composed of?
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Match the following parts of the digestive system with their primary roles:
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What type of tissue forms the muscular layer of the proventriculus?
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Study Notes
Mouth and Esophagus
- Beak is utilized for prehension; palate exhibits an incomplete fusion known as the choanal cleft.
- The tongue is minimally muscular, primarily composed of the entoglossal bone, and covered by a thick cornified mucous membrane.
- The crop (or ingluvies) is a distensible dilation of the esophagus that temporarily stores food.
- Salivary glands in the mouth include:
- Maxillary glands (roof of the mouth)
- Palatine glands (sides of the nasal opening)
- Aphenopterygoid glands (roof of the pharynx)
- Anterior and posterior submandibular glands (junction of upper and lower beaks)
- Lingual glands (in the tongue)
- Crico-arytenoid glands (around the glottis)
- A small gland situated at the mouth's angle.
- The esophagus connects the mouth to the crop, which allows for meal consumption and continuous digestion.
- Composed of four layers: mucosa, submucosa, muscularis, and serosa.
Proventriculus
- Also known as the glandular stomach, it is small and tubular with a thick wall comprising five layers:
- Outer serous membrane
- Three muscular layers (two longitudinal, one thick circular)
- Areolar tissue layer for blood and lymph vessels
- Glandular tissue layer
- Submucosa and mucous membrane layer
- Simple tubular glands organized into lobules converge into a common duct for juice production, aiding digestion.
- Raised mucous membrane folds harbor numerous tubular glands which secrete hydrochloric acid and lymphoid tissue.
Gizzard
- Positioned after the proventriculus, it contains a thick outer tendinous layer and powerful red muscle masses.
- The inner mucosa, known as the koilin, is highly keratinized, forming a durable sheet to withstand grinding of food mixed with hard objects like grit.
- Composed of multiple tissue layers, the gizzard's primary function is the disintegration of food.
Small Intestine
- Begins at the gizzard's exit and ends at the ileo-caecal-colic junction, where it meets the caeca and colon.
- The duodenum is the only easily observable part, crucial for digestion and nutrient absorption, featuring villi for increased surface area.
- The pancreas is located between the duodenum's arms, contributing to digestive enzyme secretion.
- The jejunum and ileum together measure approximately 120 cm long, with no clear separation.
- The ileum is characterized by shorter villi and less lymphoid tissue, alongside Meckel’s Diverticulum, which is an embryonic remnant.
Large Intestine
- The large intestine is relatively short with notable ceca that facilitate water and electrolyte absorption.
- Each cecum is approximately 16-18 cm long, featuring three segments: a thick-walled base, a middle segment with thinner walls, and a wide blind apex.
- The ceca consist of a serous membrane, longitudinal and circular muscle layers, and mucosa.
Cloaca
- The large intestine culminates in the cloaca, a common cavity for the digestive and urogenital tracts.
- Composed of three chambers: coprodeum (continuation of the colon), urodeum (receives ureters and genital ducts), and proctodeum (opens to the vent).
- The Bursa of Fabricius is located above the cloaca in young birds and regresses by one year of age.
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Description
Test your knowledge on the digestive anatomy and physiology of poultry, focusing on the mouth and esophagus. Explore key features such as prehension, the choanal cleft, and the crop. This quiz covers essential concepts for students in animal science or veterinary studies.
