Gastrointestinal Tract Physiology Flashcards
(32 cards)
What is the The gastrointestinal tract (GIT)?
is a continuous tube extending from the oral cavity to the anus, about 5–7 meters long.
The tract consists of several hollow organs, supported by accessory digestive organs.
It is also called the alimentary canal
What are the primary roles of the GI tract?
•Ingestion
•Motility, mixing and Propulsion
•Digestion
•Absorption
•Excretion
How many Concentric layers has the Gi tract? And what are they?
4 layers
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa or Adventitia
What are the major organs of the alimentary canal in anatomical order?
- Mouth (oral cavity)
- Pharynx
- Esophagus
- Stomach
- Small intestine (duodenum, jejunum, ileum)
- Large intestine (cecum, colon, rectum)
- Anus
What are the components of the mucosa in the GI tract?
- Epithelium – varies (e.g., stratified squamous in esophagus, columnar in stomach/intestine)
- Lamina propria – loose connective tissue with immune cells
- Muscularis mucosae – smooth muscle aiding in local movement
What is the function of the submucosa?
• Contains dense connective tissue
• Houses blood vessels, lymphatics
• Submucosal (Meissner’s) plexus: regulates secretion and local blood flow
What is the function of the muscularis externa?
• Inner circular muscle: controls constriction
• Outer longitudinal muscle: controls shortening
• Myenteric (Auerbach’s) plexus: coordinates peristalsis and segmentation
What is the difference between serosa and adventitia in the GI tract?
•Serosa: Found in intraperitoneal organs (e.g., stomach, small intestine); visceral peritoneum
•Adventitia: Found in retroperitoneal organs (e.g., esophagus, pancreas); connective tissue
What are the structures of the oral cavity?
Lips, cheeks, tongue, teeth, salivary glands
What are the functions of the oral cavity?
Mechanical digestion: Mastication (chewing) breaks food into smaller pieces
• Chemical digestion: Salivary amylase starts carbohydrate breakdown
What structure is the pharynx?
The structure that Connects oral cavity to esophagus; shared with respiratory tract
What is the role of the esophagus in digestion?
• Transport: Moves bolus from the mouth to the stomach via peristalsis
• Lower esophageal sphincter (LES) prevents acid reflux
“It has no digestive function “
Characteristics of the esophagus
• 25–30 cm muscular tube
• Upper third: striated muscle
• Lower third: smooth muscle
What is the difference between hormones and enzymes?
•Hormones are chemical messengers released by endocrine glands into the blood to regulate functions in distant organs (e.g., insulin, gastrin).
• Enzymes are biological catalysts produced locally that speed up chemical reactions by acting on specific substrates (e.g., amylase, lipase).
What is Saliva?
Saliva is a hypotonic fluid secreted by the salivary glands into the oral cavity. It plays essential roles in digestion, protection, lubrication, and oral health.
Hiw many salivary glands do humans have?
Humans have three major pairs of salivary glands and numerous minor glands
What are the three major pairs of salivary glands ?
1.Parotid gland – serous, enzyme-rich
2. Submandibular gland – mixed (mostly serous)
3. Sublingual gland – mixed (mostly mucous)
What is the percentage of saliva produced by each salivary gland?
•Parotid gland-25% of saliva rich in amylase
•Submandibular gland-70% of saliva
•Sublingual gland-5% of saliva
What is the typical water content of saliva?
99% water, with 1% solutes including enzymes, electrolytes, and proteins.
Name two digestive enzymes found in saliva and their functions.
• Salivary amylase (ptyalin) – begins starch digestion
• Lingual lipase – starts lipid digestion, especially in infants
Which immunologic components are present in saliva?
•IgA
• Lysozyme
• Lactoferrin
What are the major functions of saliva?
• Digestion (starch and fat)
• Lubrication (mucins)
• Protection (antibacterial, buffering)
• Taste facilitation
• Oral health (cleansing, healing)
