Digestive system - Part 1 Flashcards
The organs of the digestive system are divided into two groups. These are?
Alimentary canal (GI tract/digestive tract)
Accessory digestive organs
What are the accessory digestive organs?
Teeth and tongue.
Salivary glands, gallbladder, liver, pancreas
What are the different digestive processes?
Ingestion Propulsion Mechanical digestion Chemical digestion Absorption Defecation
What is ingestion?
Taking of food into the mouth
What is propulsion?
Movement of food
Voluntary - swallowing
Involuntary - peristalsis - move food down the esophagus and SI
What is mechanical digestion?
Mechanical breakdown of food, preparation for chemical digestion.
Chewing, churning of stomach, segmentation
What is chemical digestion?
Where does it occur?
Chemical breakdown of complex molecules to simple components via enzymes secreted by digestive glands.
Mouth, stomach, pancreas, SI
What is absorption?
Transport of digested nutrients from GI tract into the blood/lymph
What is defecation?
Elimination of indigestible substances as feces
Describe peristalsis.
Major means of propulsion
Adjacent segments of the alimentary canal relax and contract
Involuntary
Controlled by smooth muscle
Describe segmentation.
Rhythmic local contractions of the intestine.
Mechanically breaks down food and mixes it with digestive juices.
(only in SI)
Gives maximum contact with digestive juices (chemical breakdown)
What are the four layers of the alimentary canal?
Mucosa
Submucosa
Muscularis externa
Serosa
What is the innermost layer of the alimentary canal wall?
What are the rest, in order?
Mucosa
Submucosa
Muscularis externa
Serosa
What does the mucosa consist of?
Epithelium - non-keratinized stratified squamous epithelium
- simple columnar epithelium
Lamina Propia - areolar CT
Muscularis mucosae
What does the submucosa contain?
What tissue type does it have?
Contains blood and lymphatic vessels, and nerve fibres
Moderately dense areolar CT containing elastic fibres
The GI tract is a ______ membrane. Why?
Mucous
Open to the outside
Why can the mucosal layer be two different tissue types?
In the mouth, esophagus, anus and rectum - will have non-keratinized stratified squamous epithelium - protect against abrasion
Simple columnar epithelium for the rest - more absorptive role and secretion of mucus
What is the CT tissue layer under the mucous membrane?
Lamina propria - areolar CT
What does the muscularis mucosa do?
Small layer of muscle.
If tiny fluid particles get lodged, can twitch to dislodge food lodged in the epithelium.
Which parts of the alimentary canal have skeletal muscle? Which have smooth?
Mouth, pharynx, majority of esophagys, external anal sphincter
The rest is smooth muscle in one of two layers.
What are the two layers of smooth muscle in the muscularis externa?
Circular muscularis
- inner layer - squeezes gut tube
Longitudinal muscularis
- outer layer, shortens gut tube
Describe the serosa.
Outermost layer
Visceral peritoneum
Mesothelium and areolar CT.
What is malt?
Immune cells - part of areolar CT
Smooth muscle:
Primarily found in walls of _______.
Fibres ________.
Have ___ ______-located nucleus.
Grouped into sheets:
- Longitudinal layer - ________ to long axis of organ
- circular layer - deeper layer, fibres run around the ________ of organ
Viscera elongated one centrally-located Parallel circumference