Avian Digestive System Anatomy

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Questions and Answers

What type of cells line the sinusoids in the liver?

Columnar epithelial cells

Hepatocytes

Smooth muscle fibers

Endothelial cells and stellate macrophages (correct)

What is the functional unit of the liver that corresponds to the periphery of the classic lobules?

Classic Lobule

Liver Acinus Zone 3

Liver Acinus Zone 1 (correct)

Portal Lobule

What type of epithelium lines the gallbladder?

Cuboidal epithelium

Squamous epithelium

Tall columnar epithelium (correct)

Cuboidal epithelium

What is the main function of the exocrine part of the pancreas?

Producing enzymes such as amylase and lipase Signup and view all the answers

What type of muscle fibers are found in the tunica muscularis of the gallbladder?

Smooth muscle fibers Signup and view all the answers

What is the shape of the gallbladder?

Hollow pear-shaped Signup and view all the answers

What is the main difference between the histologic features of the liver, gallbladder, and exocrine pancreas in birds and mammals?

The features are not significantly different Signup and view all the answers

What is the structural organization of the liver that is divided into three zones based on the distance from the short axis?

Liver Acinus Signup and view all the answers

What is the characteristic of the tunica muscularis?

Thick layer of smooth muscle Signup and view all the answers

What type of glands predominate in the sublingual gland?

Mucous glands Signup and view all the answers

Where are the cecal tonsils located?

At the orifice of the cecum Signup and view all the answers

What is the function of the autonomic nervous system in salivary glands?

Regulates the amount of saliva produced Signup and view all the answers

What is the characteristic of the liver lobes?

Each lobe is covered by a thin layer of serosa Signup and view all the answers

What is the characteristic of the villi in the small intestine?

They are longest in the duodenum and gradually shorten and thicken caudally Signup and view all the answers

What is the name of the duct that drains the parotid gland?

Stensen's duct Signup and view all the answers

What is the characteristic of the submandibular gland?

It is predominantly serous Signup and view all the answers

What is the location of the sublingual gland?

Inferior to the tongue Signup and view all the answers

What is the characteristic of the interlobular connective tissue in the liver?

It is scant and difficult to see except in one place Signup and view all the answers

What is the characteristic of the lining epithelium in the oral cavity?

Keratinized stratified squamous Signup and view all the answers

Which of the following structures is found only on the base of the tongue and the floor of the oral cavity?

Bundles of skeletal muscles Signup and view all the answers

What is the characteristic of the lamina propria in the esophagus?

Loose CT with large mucous glands Signup and view all the answers

What is the characteristic of the tunica muscularis in the esophagus?

Thick inner circular and thin outer longitudinal Signup and view all the answers

What is the characteristic of the mucosa in the proventriculus?

Macroscopic papillae with numerous microscopic folds Signup and view all the answers

What is the characteristic of the proventricular glands in the proventriculus?

Adjacent cells are in direct contact only on their basal half Signup and view all the answers

What is the characteristic of the lining in the ventriculus?

A cuticle or koilin membrane Signup and view all the answers

What is the characteristic of the tunica submucosa in the proventriculus?

Contains lobules of compound tubular glands Signup and view all the answers

Study Notes

Oral Cavity

Lining epithelium: keratinized stratified squamous
Tongue: bundles of skeletal muscles, only found at the base of the tongue and floor of the oral cavity, with entoglossal bone

Esophagus

Lining epithelium: thick non-keratinized stratified squamous
Lamina propria: loose CT with large mucous glands
Muscularis mucosae: longitudinally arranged smooth muscle
Tunica submucosa: thin layer of loose CT
Tunica muscularis: thick inner circular, thin outer longitudinal

Crop

Sac-like diverticulum of esophagus, storage organ
Histologically similar to esophagus, except glands restricted to area near its junction to esophagus

Proventriculus

"Glandular stomach"
Mucosa: macroscopic papillae with numerous microscopic folds (plicae)
Proventricular glands present, adjacent cells in direct contact only on their basal half, only one cell type (oxynticopeptic cells) identifiable
Lamina propria: thin
Muscularis mucosae: interrupted by proventricular glands
Tunica submucosa: contains lobules of compound tubular glands
Tunica muscularis: typical
Tunica serosa: typical

Ventriculus (Gizzard)

"Muscular stomach"
Lining: cuticle or koilin membrane, not a stratum corneum
Lamina propria: loose CT
Tunica submucosa: loose CT, no submucosal glands
Tunica muscularis: thick layer of smooth muscle
Tunica serosa: typical

Small Intestine

Lamina propria and tunica submucosa: contain large amounts of diffuse and nodular lymphatic tissue
Submucosal glands of the duodenum are generally absent
Tunica muscularis: third layer of circular smooth muscle may be present
Villi are present throughout, longest in the duodenum, but gradually shorten and thicken caudally

Cecum (Ceca)

Two blind sacs attached to the junction of small intestine and large intestine
Villi: at the orifice, diminish and flatten towards the caudal end
Cecal tonsils (lymphatic nodule) present at the cecal orifice, infiltrate the lamina propria and submucosa

Cloaca

3 regions: coprodeum, urodeum, and proctodeum
All 3 parts have similar structures, with villi and simple columnar epithelium with a variable number of mucus-secreting cells

Glands Associated with the Digestive System

Salivary Glands

Made up of a series of secretory units
Controlled by the autonomic nervous system, sympathetic stimulation results in thick and decreased secretion, while parasympathetic stimulation results in a thin and increased secretion

Major Salivary Glands

Parotid: paired, located anterior and inferior to the external ear
Submandibular: paired, located inferior to the mandible in the floor of the mouth
Sublingual: aggregates of smaller glands located inferior to the tongue

Parotid Gland

Predominantly serous glands separated by thin connective tissue septa
Excretory duct: Stensen's duct

Mandibular (Submandibular/Maxillary) Gland

Well-defined capsule
Fairly prominent duct system
Most animals: predominantly serous type, carnivores: predominantly mucous
Excretory duct: Wharton's duct

Sublingual Gland

Ill-defined capsule, but has more prominent connective tissue septa
Mucous cells predominate
Striated and intercalated ducts: well-developed in horse, ruminants, and pigs, poorly developed in carnivores
Ducts: Bartholin duct (largest sublingual gland excretory duct) and Rivinus duct (minor sublingual duct)

Liver

Largest gland in the body
Capsule and stroma: each lobe covered by serosa (from peritoneum), connective tissue from the capsule extends into the liver lobes, forming interlobular connective tissue that surrounds individual liver lobules, supporting the vascular and bile duct systems
Hepatic cords: rows of hepatocytes
Sinusoids: lined by endothelial cells and stellate macrophage (Kupffer cells)

Liver Acinus

3 ways to describe in terms of the functional unit: classic lobule, portal lobule, and liver acinus
Zone 1: closest to the short axis and the blood supply from penetrating branches of the portal vein and hepatic artery, corresponds to the periphery of the classic lobules
Zone 2: in between 1 and 3, no sharp boundary
Zone 3: farthest from the short axis and closest to the terminal central vein

Gallbladder

Hollow pear-shaped organ attached to the liver of most animals
Epithelium: tall columnar
Lamina propria: blends with T.submucosa
Muscularis mucosae: absent
Tunica muscularis: circular bundles of smooth muscle fibers

Pancreas

Encapsulated, lobulated, compound tubuloacinar gland
Exocrine part: enzymes, e.g., amylase, lipase, trypsin
Endocrine part: mainly insulin and glucagon

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Description

This quiz covers the anatomy of the avian digestive system, including the oral cavity, tongue, esophagus, and other related structures.