GI System Part 1 Flashcards
What are the tissues that make up the wall of the GI tract?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
The Mucosa is composed of three layers, what are they?
- Mucous membrane: epithelial cells
- Lamina propria: connective tissue and vasculature
- Muscularis mucosae: thin smooth muscle
What are the three cell types in the mucous membrane of the Mucosa?
- Absorptive cells-absorbing nutrients
- Exocrine cells-secrete digestive fluids
- Endocrine cells
All of which are Entercyote
The Lamina propria contains connective tissue. What else make up this layer?
Small blood vessels, lymphatic vessels, nerves, and lymphoid tissues (i.e.-lymph nodules and Peyer’s patches)
Which layer of the Mucosa is a thin layer of smooth muscle with both longitudinal and circular fibers that mix the lumenal contents?
Muscularis mucosae
Which layer of the GI wall is comprised of a thick layer of connective tissue with large blood and lymphatic vessels? It also has one part of the Enteric Nervous System called Submucosal plexus (Meissner’s plexus).
Submucosa
Which layer of the GI wall is comprised of two layers of smooth muscle in which the inner layer is circular to change diameter and the outer layer is longitudinal to change length? It also contains one part of the Enteric Nervous System called Myenteric plexus (Auerbach’s plexus).
Muscularis externa
Which layer of the GI wall is comprised of an inner layer of connective tissue and an outer layer of epithelial tissue? It is continuous with the mesenteries.
Serosa
What are the major organs of the GI tract and what are their functions?
Mouth-food breakdown starts here
Pharynx-passageway for food
Esophagus-passageway for food
Stomach-food storage, secretes gastric juices
Small Intestine-digestion and absorption of nutrients
Colon-concentration of wastes into feces, water absorption, and storage of feces
Rectum-storage of feces
Anus-wastes exit
What are the two major divisions of the Enteric Nervous System and where are they located?
Submucosal-in the Submucosa
Myenteric-in the Muscularis externa
Describe the brush border. Where is it located and what is its function?
The brush border is a layer of microvilli on the absorptive cells located on the Villi in the Duodenum. It increases surface area of epithelial cells.
Where does the most digestion and absorption occur in the GI tract?
The small intestine.
The lining of the stomach contains gastric pits. What is their purpose?
Gastric pits secrete products to aid in digestion.
Name the products secreted from the Gastric Pits and describe them.
Pepsinogen: secreted by chief cells, precursor to pepsin, which digests protein.
Hydrogen ions: secreted by parietal cells and maintain the acidic environment of the stomach
Intrinsic factor: secreted by parietal cells, necessary for the absorption of B12.
Gastrin: secreted by G cells (hormone)
Mucous: secreted from neck cells
What environment is necessary to activate Pepsin?
an acidic environment, pH 2
What is the purpose of the pancreatic juices entering the duodenum?
To neutralize the pH of chyme to 7