L21 - GI Tract Structure Flashcards
What is the GI system?
A network of organs and specialised cells - enable you to transform the food you eat into the energy and nutrients required for life
What are the different parts of the GI tract? (6)
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
- anus
What are the accessory organs in the GI tract? (4)
- salivary glands
- liver
- gallblader
- pancreas
What is the mesentery?
Membranous tissue that surround organs of the GI tract
What does the mesentery do? (2)
- holds intestines in place
- provides blood vessels and lymphatics
What are the different parts of the mouth? (4)
- teeth
- tongue
- mucous membranes
- pharynx and epiglottis
What is the main function of the mouth?
To chew food
What is the pharyn and epiglottis and their function?
Muscular flaps in the throat
- prevents food travelling to the lungs
What is the oesophagus?
Tube like structure
What does the oesophagus do?
Involuntary movement of food bolus
- transports food bolus to the stomach
What does the stomach do? (3)
- mixing
- protein digestion
- fat emulsification
What does the stomach contain? (2)
- HCl
- pepsin
What are the different layers of the stomach wall? (4)
- mucosa
- submucosa
- muscularis externa
- serosa
What are the different types of cell types in the stomach wall? And what do they secrete? (6)
- mucous neck cell - mucus, protects lining
- parietal cells - HCl, intrinsic factor
- enterchromaffin-like cell - histamine
- chief cells - pepsin(ogen), gastric lipase
- D cells - somatostatin, inhibits acid
- G cells - gastrin, stimulates acid
What is the small intestine? (2)
Longest part of the GI tract
- main site of absorption
- primary site of breakdown (CHO, proteins, fats)
What are the 3 section of the SI?
- duodenum
- jejunum
- illeum
What are the different cells in the SI? And what do they do? (4)
- absorptive cells - absorbs nutrients
- goblet cell - secretes mucus
- enteroendocrine cell - secretes hormones: secretinm chlolecystokinin)
- paneth cell - secretes lysozymes, capable of phagocytosis
What is the purpose of the villus? (2)
- increase SA
- absorption
What are the crypts of lieberkuhn?
Invaginations formed between the villi
What are the cells in the crypts of lieberkuhn and what are their function? (3)
- paneth cells - defensins, antimicrobial, lysosymes, phagocytic
- stem cells - regeneration
- goblet cells - mucous
What is the function of the large intestine? (4)
- water and ion conservation
- bulk movement of faeces
- storage
- defaecation
What are the purpose of the salivary glands? (3)
- lubrication - mucus
- protection - thiocyanate, lysosymes
- digestion - amylase, lipase
What are the different salivary glands? (3)
- parotid gland
- submandibular gland
- sublingual gland
What are the functions of the liver? (2)
- bile production
- excretion
What is the function of the gallblader? (2)
- concentrating reservoir for bile
- deliver bile to the deodenum in response to meals
What is the function of the pancreas? (2)
- makes enzymes to digest proteins, fats, and CHO
- produces the hormones insuling and glucagon
What are the functions of the GI system? (6)
- ingestion
- secretion
- movement
- digestion
- absorption
- excretion
What is ingestion?
The process of taking in food, drink, through the mouth
What is secretion?
The release of substances that contribute to digestion
What are the different types of movement? (2)
- segmentation
- peristalsis
What is digestion?
Breakdown of food into smaller component that can be absorbed into the bloodstream
What are the types of digestion? (2)
- mechanical digestion
- chemical digestion
What is mechanical digestion? (3)
Physically breaking down food substances into smaller particles
- mastication
- peristaltic contractions
- gastric acids
What is chemical digestion?
Use of enzymes to breakdown food
What are the products to the breakdown of these particles? (3)
- Fats -> FA and monoglycerides
- Nucleic acids -> nucleotides
- Polysaccharides, CHO sugars -> monosaccharides
- Proteins -> amino acids
What is absorption?
The process through which nutrients, water and electrolytes enter the blood
What is excretion?
The process by which metabolic waste is eliminated from the body
What is the role of the GI tract in immune function? (3)
- first line of defence against pathogens
- divers microbiome that contributes to immune regulation
- gut-resident immune cells
What does the microbiome prevent?
Overgrowth of harmful bacteria
What do cells secrete in terms of the immune function? (2)
- mucus
- antimicrobial peptides
