Anatomy and Physiology
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Where does the GI tract mainly lie on?
Viscera and pelvis
What’s another name for GI tract?
Alimentary canal
Describe the features of the alimentary tract:
• Alimentary canal • Continuous hollow tuve • Oesophagus to rectum approx 8 meters long
Function of the GI tract?
Breakdown the ingested food into small molecules which can be taken into body tissue
What are the two types of digestion?
• Chemical (secretion of enzymes = amylase CHO) - Mechanical (motility = mixing and grinding, mastication - chewing)
What is absorption in the GI tract?
Movement of small molecules across the gut wall and into the circulation
Components of the small intestine
The first part is called the duodenum. The jejunum is in the middle and the ileum is at the end
Components of the large intestine
The appendix, cecum, colon, and rectum
What chemical factors are used to break down food into smaller molecules?
Digestive juices, such as stomach acid, bile, and enzymes
Does the small intestine have villi?
Yes, only the small intestine does
What is the autonomic nervous system?
The nerves that are involved in controlling any of our functions beyond our conscience and awareness
What two branches are there for autonomic nervous system?
Parasympathetic and sympathetic
Concerning digestion what are parasympathetic nerves involved in?
Stimulating digestion
Concerning digestion what are sympathetic nerves involved in?
Inhibiting digestion
What is peristalsis?
The movement of organ walls in the gastrointestinal tract. Peristalsis moves food and liquid through the gastrointestinal tract and mixes the contents within each organs
Role of the oesophagus
• Delivers food to the stomach • Muscular tube = 25cm in length and 2cm in diameter • Pharynx to the stomach • Fast transport: peristalsis
Bolus direction is generally…
Mouth to anus = oral contraction to aboral relaxation
Role of the stomach
• Reservoir = stores food • Begins digestion (mechanical and chemical) • Satiety = stretching of the stomach wall produces a hormone that tells the brain you are starting to feel full
What substances are released during digestion?
• HCl • Pepsinogen • Mucus • Gastrin (hormone)
Gastric juice - HCl
• Low pH = 2 • Prevents bacterial growth • Catalyses cleavage of pepsinogens to pepsin
Gastric juice - pepsinogen
• Proenzyme (enzyme that is not yet activated) of pepsin - Digestion of proteins into peptides
Gastric juice - mucus
• Protects the gut mucosa from the HCl
Gastric juice - gastrin
• Acid production (hormone that tells gastric gland to make gastrin)
Role of the small intestine
• Digestion, absorption of food into the blood and movement of material • Most absorption takes place • Absorptive epithelium • Peristaltic movement