BMS2038 Wk 6 Gastrointestinal tract Part 1
learning outcomes
Lecture 1- digestive system
Why do we have a digestive system
- We need nutrients
- chemical energy
- building new body tissues
- repair damaged tissues
- Food needs to be broken down into smaller molecules to be absorbed by cells
- Digestive systems optimised for processing food
- extensive surface area
- in contact with the external environment- food coming in
- closely associated with the cardiovascular system- once food is broken down the
food is able to be able absorbed into bloodstream
Digestive system
- GI tract- start of with mouth passing through the
pharynx and down into oesophagus , (connects
mouth down into stomach) from stomach into the
small intestine into large intestine and lastly into
anal canal
- Teeth-mechanically breaking down food
- Tongue- manipulating food -moving side to side
- Salivary gland- first point where food is putting into
solution (enzymes)
- Liver- making bile and metabolism
- Gallbladder- where bile is stored
- Pancreas- source of enzymes
What is the gastrointestinal tract
- Continuous tubular system
, - Extends from the mouth to the anus (mouth, pharynx, oesophagus, stomach, small
intestine, large intestine, anus)
- 5-7 metres long
- Physiological barrier between the outside world and the body environment
- Egmental heterogeneity
- Different parts adapted for different function
6 processes of the digestive system
- Ingestion- taking food into mouth
- Secretion - enzymes mechanically breaking down food, mucous secretion- helps
food get along
- Motility- specialisations for food to be mixed, muscular actions to further break the
food to ensure its mixed up with the enzymatic juices
- Digestion- mechanical digestion physically breaking down. Chemical digestion action
of enzymes
- Absorption- where molecules are passed into the bloodstream and transported
wherever needed
- Defeation (→poo)- getting rid of all material not wanted or material that
has not been digested
GI tract: 4 layers
- Mucosa- faces into the lumen (directly adjacent to the food that's passing through)
- 3 layers: inner layer of epithelial cells, layer of lamina propria and muscularis layer-
important for resting folds and increasing surface area)
- Submucosa layer- glands, part of enteric nervous system
- Muscularis layer- circular muscle (longitudinal which are running parallel and work
together)
- Serosa- final layer that holds all of GI tract together
Mucosa– layer 1
- Mucous membrane
- 3 layers
1. Epithelial liar
, - Direct contact with contents of GI tract
- Simple columnar epithelium with tight junctions to restrict leakage
- Replaced every 5-7 days
- Exocrine cells- secrete mucus and fluid
- Enteroendrocrine cells- secrete hormone
2. Lamina propria
- Connective tissue
- Blood and lymphatic vessels- nutrient absorption
- Mucosa- associated lymphatic tissue (MALT)- part of immune systems sits
within the GI tract
3. Muscularis mucosae
- Smooth muscle fibres
- Created fold in the mucous membrane
Submucosal layer– layer 2
- Areolar connective tissue
- Blood and lymphatic vessels
- Neurons- part of nervou system sits within GI tract
Muscular layer– layer 3
- Smooth muscle
- Inner sheet of regular fibres and outer sheet of longitudinal fibres
- More neurons to stimulate the tone in the movements of the GI tract
Serosa layer- layer 4
- Serous membrane
- Areolar connective tissue and simple squamous epithelium
- Blood and lymph
Summery GI tract structure
learning outcomes
Lecture 1- digestive system
Why do we have a digestive system
- We need nutrients
- chemical energy
- building new body tissues
- repair damaged tissues
- Food needs to be broken down into smaller molecules to be absorbed by cells
- Digestive systems optimised for processing food
- extensive surface area
- in contact with the external environment- food coming in
- closely associated with the cardiovascular system- once food is broken down the
food is able to be able absorbed into bloodstream
Digestive system
- GI tract- start of with mouth passing through the
pharynx and down into oesophagus , (connects
mouth down into stomach) from stomach into the
small intestine into large intestine and lastly into
anal canal
- Teeth-mechanically breaking down food
- Tongue- manipulating food -moving side to side
- Salivary gland- first point where food is putting into
solution (enzymes)
- Liver- making bile and metabolism
- Gallbladder- where bile is stored
- Pancreas- source of enzymes
What is the gastrointestinal tract
- Continuous tubular system
, - Extends from the mouth to the anus (mouth, pharynx, oesophagus, stomach, small
intestine, large intestine, anus)
- 5-7 metres long
- Physiological barrier between the outside world and the body environment
- Egmental heterogeneity
- Different parts adapted for different function
6 processes of the digestive system
- Ingestion- taking food into mouth
- Secretion - enzymes mechanically breaking down food, mucous secretion- helps
food get along
- Motility- specialisations for food to be mixed, muscular actions to further break the
food to ensure its mixed up with the enzymatic juices
- Digestion- mechanical digestion physically breaking down. Chemical digestion action
of enzymes
- Absorption- where molecules are passed into the bloodstream and transported
wherever needed
- Defeation (→poo)- getting rid of all material not wanted or material that
has not been digested
GI tract: 4 layers
- Mucosa- faces into the lumen (directly adjacent to the food that's passing through)
- 3 layers: inner layer of epithelial cells, layer of lamina propria and muscularis layer-
important for resting folds and increasing surface area)
- Submucosa layer- glands, part of enteric nervous system
- Muscularis layer- circular muscle (longitudinal which are running parallel and work
together)
- Serosa- final layer that holds all of GI tract together
Mucosa– layer 1
- Mucous membrane
- 3 layers
1. Epithelial liar
, - Direct contact with contents of GI tract
- Simple columnar epithelium with tight junctions to restrict leakage
- Replaced every 5-7 days
- Exocrine cells- secrete mucus and fluid
- Enteroendrocrine cells- secrete hormone
2. Lamina propria
- Connective tissue
- Blood and lymphatic vessels- nutrient absorption
- Mucosa- associated lymphatic tissue (MALT)- part of immune systems sits
within the GI tract
3. Muscularis mucosae
- Smooth muscle fibres
- Created fold in the mucous membrane
Submucosal layer– layer 2
- Areolar connective tissue
- Blood and lymphatic vessels
- Neurons- part of nervou system sits within GI tract
Muscular layer– layer 3
- Smooth muscle
- Inner sheet of regular fibres and outer sheet of longitudinal fibres
- More neurons to stimulate the tone in the movements of the GI tract
Serosa layer- layer 4
- Serous membrane
- Areolar connective tissue and simple squamous epithelium
- Blood and lymph
Summery GI tract structure
