Biology: The Digestive System

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Questions and Answers

What is the function of the ruminal papillae in the rumen?

To increase the absorbing surface, protection, and metabolism.

What type of epithelium is present in the mucosa of the rumen?

Keratinized stratified squamous epithelium.

What is the composition of the lamina propria in the rumen?

An irregular dense connective tissue (CT).

What is the characteristic feature of the reticulum?

Permanent interconnecting folds, the reticular crests, giving a honeycomb appearance. Signup and view all the answers

What type of epithelium is present in the mucosa of the reticulum?

Keratinized stratified squamous epithelium. Signup and view all the answers

What are the conical reticular papillae that project into the lumen of the reticulum?

Small protrusions of the mucosal surface. Signup and view all the answers

What is the characteristic feature of the omasum?

Approximately 100 longitudinal folds, the laminae, that arise from the internal surface. Signup and view all the answers

What is the function of the omasum?

Not mentioned in the text. Signup and view all the answers

What is the definition of the digestive system?

The digestive system is a system associated with the reception, breakdown of food particles, absorption of nutrients, and expulsion of unabsorbed materials. Signup and view all the answers

What are the two types of stomach found in different animals?

Simple stomach and Compound stomach Signup and view all the answers

What are the four layers of the wall of the digestive tract?

Mucosa, Submucosa, Muscularis externa, and Serosa/Adventitia Signup and view all the answers

What are the three components of the mucosa layer?

Lamina epithelium, Lamina propria, and Lamina muscularis mucosa Signup and view all the answers

What is the function of the Meissner's plexus in the submucosa layer?

It is a nerve plexus that innervates the digestive tract. Signup and view all the answers

What is the difference between the stomach of ruminant animals and non-ruminant animals?

Ruminant animals have a compound stomach with four chambers, while non-ruminant animals have a simple stomach. Signup and view all the answers

What is the role of the accessory digestive organs in the digestive system?

They aid in the breakdown and absorption of nutrients. Signup and view all the answers

What are the additional parts of the digestive system found in birds?

Crop, Proventriculus, and Gizzard Signup and view all the answers

What type of cells are the main constituent of the mucosa?

Light cells (pale cytoplasm) and a small proportion of dark cells (dark cytoplasm) Signup and view all the answers

What is the characteristic feature of the epithelial cells in the mucosa?

Microvilli, similar to absorptive cells in the intestine Signup and view all the answers

What is the composition of the propria-submucosa?

Loose connective tissue Signup and view all the answers

What is the orientation of the smooth muscle cells in the muscularis externa?

Circular direction Signup and view all the answers

What is the term for the outer layer of mesothelium and loose connective tissue?

Serosa Signup and view all the answers

What is the structural type of the pancreas?

Compound tubuloalveolar gland Signup and view all the answers

What are the two parts of the pancreas lobule?

Endocrine part (islets of Langerhans) and exocrine part (pancreatic acinus) Signup and view all the answers

What is the characteristic feature of the pyramidal cells in the pancreatic acinus?

Round basal nucleus with peripheral chromatin condensation, surrounded by rough surfaced endoplasmic reticulum Signup and view all the answers

What is the main function of the microvilli on the surface of the villi in the small intestine?

To increase the absorptive surface of the small intestine Signup and view all the answers

What type of cells are the most abundant in the simple columnar epithelium of the small intestine?

Enterocytes or absorptive cells Signup and view all the answers

What is the function of the goblet cells in the small intestine?

To produce mucin, a protein polysaccharide, which forms mucous when mixed with water Signup and view all the answers

What type of cells are occasionally found in the surface epithelium of the small intestine and secrete bradykinin?

Argentaffin cells (EE cells/Enterochromaffin cells) Signup and view all the answers

What is the composition of the lamina propria in the small intestine?

Loose CT with some elastic fibers Signup and view all the answers

What are the lacteals in the lamina propria of the small intestine?

Lymphatic capillaries Signup and view all the answers

What is the function of the intestinal glands or crypts of Lieberkuhn in the small intestine?

To open onto the luminal surface at the bases of the villi Signup and view all the answers

What is the importance of the diffuse lymphatic tissue and solitary lymphatic nodules in the lamina propria of the small intestine?

They are an important component of GALT (Gut-Associated Lymphoid Tissue) Signup and view all the answers

What are the two triangular areas that make up the liver acinus?

Two adjacent classical lobules Signup and view all the answers

What is the portal fissure, and what structures pass through it?

The portal fissure is the area on the visceral surface of the liver through which vessels, nerves, and ducts pass, including the portal vein, hepatic artery, hepatic vein, bile duct, lymphatic, and nerve. Signup and view all the answers

What is the function of the hepatic artery, and what type of blood does it contain?

The hepatic artery contains pure blood, and it brings oxygen and nutrients to the liver. Signup and view all the answers

What is the function of bile canaliculi, and where are they located?

Bile canaliculi are spaces between the plasma membranes of adjacent liver cells where bile is secreted by liver cells, and they are located between adjacent hepatic cells. Signup and view all the answers

What is the role of the interlobular hepatic ducts, and what type of epithelium do they have?

The interlobular hepatic ducts are responsible for collecting bile from the intralobular ductules, and they are lined by cuboidal epithelium. Signup and view all the answers

What is the structure of the gallbladder mucosa when it is empty, and how does it change when it fills with bile?

When the gallbladder is empty, its mucosa is thrown into numerous folds, and when it fills with bile, these folds flatten, resulting in a smoother mucosal surface. Signup and view all the answers

What is the pathway of bile secretion from the liver cells to the bile duct?

Bile is secreted by liver cells into bile canaliculi, which then connect to intralobular bile ducts or Canal's of Herring, and finally, these ducts empty into interlobular hepatic ducts, which are part of the bile duct. Signup and view all the answers

What is the role of the portal vein, and what type of blood does it contain?

The portal vein contains impure blood and nutrients, and it brings blood from the digestive system to the liver. Signup and view all the answers

Study Notes

Digestive System

Definition: Reception, breakdown of food particles, absorption of nutrients, and expulsion of unabsorbed materials

Parts of Digestive System

Mouth
Pharynx
Esophagus
Stomach
Intestine

Types of Stomach

Simple stomach: Found in dogs, cats, and tigers
Compound stomach: Found in ruminant animals, consisting of rumen, reticulum, omasum, and abomasum

Accessory Digestive Organs

Teeth
Tongue
Liver
Pancreas
Salivary glands (parotid, submandibular, and sublingual)

Digestive System in Birds

Mouth
Pharynx
Esophagus
Crop
Proventriculus
Gizzard
Intestine

General Structure of Digestive Tract

Wall of digestive tract consists of four layers: mucosa, submucosa, muscularis externa, and serosa

Mucosa

Composed of lamina epithelium, lamina propria, and lamina muscularis mucosa
Functions: production of protective mucus and gastrin

Submucosa

Consists of loose connective tissue
Contains blood vessels and nerves
May contain Meissner's plexus (nerve)

Compound Stomach

Rumen: characterized by small tongue-shaped ruminal papillae, which increase absorbing surface, protect, and aid in metabolism
Reticulum: has a mucosa with permanent interconnecting folds, giving a honeycomb appearance
Omasum: nearly filled with longitudinal folds, laminae, which increase absorbing surface
Abomasum: similar in structure to simple stomach or true stomach of horse

Omasum

Laminae: extensions of the lamina propria, which increase absorbing surface
Villi: projections of the mucosa, which increase absorbing surface
Simple columnar epithelium: lines the villi, with microvilli, which increase absorbing surface

Intestine

Villi: increase absorbing surface
Microvilli: increase absorbing surface
Enterocytes (absorptive cells): most abundant epithelial cell type
Goblet cells: mucus-secreting cells, present in intraepithelial position
Argentaffin cells (EE cells): secrete bradykinin, possible role in controlling motor activity of intestinal tract

Liver

Portal fissure: area on the visceral surface of liver through which vessels, nerves, and ducts pass
Structures in the portal fissure: portal vein, hepatic artery, hepatic vein, bile duct, lymphatic, and nerve
Liver acinus: functional unit of the liver, composed of two triangular areas in two adjacent classical lobules
Bile canaliculi: spaces between adjacent liver cells, which receive bile secreted by liver cells

Gall Bladder

Mucosa: lined by simple columnar epithelium, with microvilli, and goblet cells
Propria-submucosa: composed of loose connective tissue
Muscularis externa: thin bundles of smooth muscle cells, mainly circular in direction
Serosa: outer layer of mesothelium and loose connective tissue

Pancreas

Accessory digestive gland
Compound tubuloalveolar gland
Structurally divided into lobes and lobules by connective tissue capsule
Endocrine part: islets of Langerhans, produce insulin and glucagon
Exocrine part: pancreatic acinus, produces digestive enzymes

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Description

Learn about the different parts of the digestive system, including the mouth, pharynx, esophagus, stomach, and intestine, and understand the differences between simple and compound stomachs.