Lecture 3.1: Introduction to Gut Function Flashcards
What are the 3 Main Processes of GI Tract?
- Digestion
- Absorption
- Excretion
What is the purpose of digestion?
Breaks down the things we eat into substances we
can utilise
Product of digestion is a solution which is…? (3)
- Sterile
- Neutral
- Isotonic
What is the purpose of absorption?
Removing needed molecules from within the gut lumen to the blood
What is the purpose of excretion?
Removal from the body:
* Ingested matter which is not needed
* Residues of matter produced by gut itself to aid
digestion and absorption
* Materials specifically excreted via liver to gut (bile)
What is Mastication?
It is the process by which food is crushed and ground by teeth
Characteristics of Saliva? (4)
- Wet
- Bacteriostatic
- Alkaline
- High calcium
Functions of Saliva? (3)
- Lubricates food for mastication and swallowing
- Protects mouth
- Starts digestion
How much saliva does a human produce per day?
1.5L
Which subprocess of digestion enables the slow release of ingested food into the gut?
Receptive relaxation of the stomach
Where in the digestive tract does ingestion and transport to storage take place?
Oesophagus
What happens during Swallowing? How long does the process take?
- Formation of bolus
- Rapid, controlled oesophageal transport
- Synchronided (peristaltic) contractions
- Approx 10sec to reach stomach
Where in the digestive tract does storage, initial disruption & disinfection take place?
The stomach
How does the stomach assist digestion?
- Relaxes to accommodate food
- Contracts rhythmically to mix and disrupt
- Secretes acid and proteolytic enzymes to break down
tissues and disinfect - Acid of acid, enzymes and agitation produces chyme
- Delivered slowly to duodenum
Where in the digestive tract does dilution and neutralisation of chyme take place? (2)
Duodenum and Jejunum
How does dilution and neutralisation of chyme occur?
- Water drawn in from ECF
- Add bile from liver
- Pancreatic secretions
- Pancreas and liver secrete alkali to neutralise acid
- Pancreas, liver and intestine secrete enzymes and bile
acids to complete digestion
Where in the digestive tract does absorption of nutrients and electrolytes take place?
Small intestine
How is the small intestine adapted for nutrient absorption? (4)
- Plicae circulares
- Villi
- Microvilli
- Long
Epithelial cells in small intestine absorb small molecules, which circulation do these go into?
They pass into hepatic portal circulation
Where in the digestive tract does final absorption of water and electrolytes take place?
Large intestine
Where does faeces accumulate? (2)
Descending and Sigmoid Colon
Motility and secretion need precise control, what mechanisms help with this control? (3)
- Neural
- Paracrine
- Endocrine
Neural Control: Somatic Motor System (what does it control)
Ingestion and Excretion
Neural Control: Autonomic Nervous System (what does it control)
- Digestion, Absorption & Excretion
- Parasympathetic control most significant
- Post ganglionic nerve cell bodies within muscle layers
of gut - These form plexuses to create the ‘gut nervous system’
- Coordinates both secretion and motility
- Range of neurotransmitters
