6 - The Digestive System Flashcards
Functions
ingestion
Propulsion
mechanical and physical digestion
chemical digestion
Absorption
defecation
What is the function of the oesophagus
It transports food to the stomach using peristalsis, which involves smooth muscle contractions
What are the main functions of the stomach
Mechanical and chemical digestion; it turns food bolus into chyme
What are the parts of the small intestine, and what is its function
Duodenum, jejunum, ileum; it digests food and absorbs nutrients and water
What is the role of the large intestine
Absorbs water, synthesises certain vitamins, and eliminates faeces
What is peristalsis
A coordinated, involuntary muscle movement that propels food through the digestive system
How is swallowing controlled
It is automatic; the brain signals the oesophagus to begin peristalsis
What does the lower oesophageal sphincter do
It opens to allow food into the stomach and closes to prevent acid reflux
What is the mucosa layer of the stomach
The innermost layer with folds that aid in digestion, absorption, and secretion
What is the function of the submucosa
It supports the mucosa with connective tissue, blood vessels, lymphatics, and nerves
What are the muscle layers of the muscularis externa
Inner oblique, middle circular, and outer longitudinal muscles that churn food
What is the serosa
The outermost layer that secretes fluid to reduce friction
What do parietal cells secrete
Hydrochloric acid (HCl) and intrinsic factor for vitamin B12 absorption
What is the role of chief cells
They secrete pepsinogen, which is activated to pepsin and digests protein
What do enteroendocrine cells secrete
Hormones such as gastrin and ghrelin
What is the function of mucous cells
They secrete mucin to protect the stomach lining
Which stomach cells are exocrine and which are endocrine
Exocrine: parietal, chief, mucous
Endocrine: enteroendocrine cells (e.g. G-cells)
What is the function of the pyloric sphincter
It regulates the release of chyme from the stomach into the small intestine
What happens in the duodenum
Chyme mixes with bile and pancreatic juices to aid digestion
How does chyme move from small to large intestine
Via the ileocecal sphincter; peristalsis moves contents slowly into the cecum
What structures increase surface area in the small intestine
Circular folds, villi, and microvilli
What is the brush border
Microvilli-covered surface that aids in nutrient absorption
What happens if microvilli are lost
It can result in malabsorption and diarrhoea
What role do bacteria play in the large intestine
They break down substances through fermentation
What do goblet cells do in the large intestine
They secrete mucus to lubricate faeces
What type of epithelium lines the large intestine
Simple columnar epithelium
What is endocrine regulation in the GI tract
Hormones are released into the blood and influence distant organs
What is paracrine regulation
Local chemicals act on nearby cells via diffusion
What is neurocrine regulation
Nerves release neurotransmitters to regulate digestion
What is the extrinsic nervous system
It includes nerves from outside the gut that modulate function (e.g. sympathetic and parasympathetic)
What is the intrinsic nervous system
The enteric nervous system within the gut wall that can function independently
