Digestive system Flashcards
What is digestion?
Breakdown of food to a useful form that can be absorbed and used by cells.
This is used for:
- the creation of energy- catabolism which produces ATP.
- repair/ building- anabolism which produces ‘building blocks’
Alimentary canal/ GI tract =
The organs that food and liquids travel through when they are swallowed, digested, absorbed, and leave the body as feces. These organs include the mouth, pharynx (throat), esophagus, stomach, small intestine, large intestine, rectum, and anus.
Accessory organs=
Accessory organs of digestion are organs that secrete substances needed for the chemical digestion of food but through which food does not actually pass as it is digested.
The main accessory organs are: liver, gallbladder, pancreas and salivary gland.
They are situated outside the GI tract and they empty the secretions into the GI tract
What are the digestive system processes?
- Ingestion
- Propulsion
- Digestion (mechanical breakdown, chemical breakdown)
- Absorption
- Defecation
What are the four layers of the GI tract wall?
- Serosa
- Muscularis
- Submucosa
- Mucosa
Serosa layer =
- Is the outermost layer
- In abdomen
- Barrier to the spread of infection
- Anchors the GI tract
Muscularis layer=
- 2 layers of smooth muscle (circular & longitudinal)
- Provides peristalsis and mixing
- Onward movement by sphincters
Submucosa layer=
- Loose connective tissue
- Blood vessels
- Nerves
- Lymph vessels
- Lymphoid tissue
Mucosa layer=
Has:
1. Mucous membrane (protects, secretes, absorbs)
2. Lamina propria (blood vessels, lymphoid tissue)
3. Muscularis mucosa (provides infoldings)
Mesenteries and lymph nodes=
Mesenteries are double layers of a membrane called the peritoneum, which lines the abdominal cavity. They hold the digestive organs in place and provide a pathway for blood vessels, lymph vessels, and nerves.
The digestive system also has lymph nodes and lymph vessels that help with immunity and absorbing fats.
Peristalsis=
Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. Beginning in your throat when you swallow and continuing through your oesophagus, stomach and intestines while you digest.
What are the stages of swallowing?
the oral preparatory stage, the oral stage, pharyngeal stage and esophageal stage
Enteric nervous system=
The Enteric Nervous System (ENS) is a group of nerves in the walls of the digestive system that controls important functions like movement of food, release of digestive juices, and blood flow.
It is part of the autonomic nervous system and has two main parts:
1. Myenteric Plexus (Auerbach’s plexus): Controls how the muscles move food through the digestive system. It works with both “rest and digest” (parasympathetic) and “fight or flight” (sympathetic) systems.
2. Submucosal Plexus (Meissner’s plexus): Controls glands and cells that release digestive juices and regulates water and nutrient flow. It only works with the “rest and digest” (parasympathetic) system.
These two plexuses keep digestion running smoothly.
Oesophagus=
is a tubular, elongated organ of the digestive system which connects the pharynx to the stomach.
Lined with mucosa to reduce friction and has thick protective stratified squamous epithelium.
The passage of food in the oesophagus is facilitated by:
- Flattening of mucosal folds
- Mucous glands
- Loose and elastic submucosa (SM)
It has muscularis externa.
The stomach=
- Stores food for 2 hours and the goes through both mechanical and chemical breakdown.
- Has an extra layer in the muscularis: the oblique muscle which are a pair of muscles, one on each side of your rectus abdominis which help rotate the trunk.
- Has highly secretary mucosa essential for digestion and protection: HCL. pepsin, mucus
- Is lined with simple columnar epithelial cells (all mucous gland cells) and millions of gastric pits (leading to gastric glands.
