The Digestive System Flashcards
What are the 6 processes of the digestive system?
- Ingestion
- Secretion
- Mixing and propulsion
- Digestion
- Absorption
- Defecation
What is ingestion
Taking food and liquids in through the mouth
What is secretion
the release of water, enzymes and acids into the lumen of the digestive tract
What is mixing and propulsion
the churning of food and its propulsion through the GI tract
what is digestion
the chemical and mechanical breakdown of food
what is absorption
products of digestion (vitamins, minerals, and water) cross the mucosa and enter the lymph or the blood
What is defecation
where undigested material is eliminated
What are the 4 layers of the GI tract:
- muscosa
- submucosa
- muscularis
- serosa
Describe the mucosa
inner lining of GI tract, mucous membrane
Describe the submucosa
Connective tissue binding the mucosa and muscularis (2nd innermost layer)
Describe the muscularis
smooth muscle layer, both circular and longitudinal (2nd outermost layer)
Describe the serosa
serous membrane, outermost layer
What is the peritoneum
The serous membrane that lines the abdominal cavity
What are the layers of the peritoneum
Parietal (superficial) layer
Visceral (deep) layer
What is the difference between the parietal and visceral peritoneum?
Parietal lines abdominal cavity
Visceral lines some organs within the cavity
What are 4 names for the folds of the peritoneum?
Greater + lesser omentum
mesentry
colon
What is the greater omentum?
A fatty apron which hangs over the transverse colon and small intestine
What does retroperitoneal mean?
The space behind the peritoneal cavity
Which organs are retroperitoneal? (3)
Kidneys
Pancreas
Ascending/descending colon
Composition of saliva? (4)
Mucin
salivary amylase
bicarbonate
lysozyme
What are the 6 organs on the digestive system?
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
What is the function of the pharynx?
- moves bolus from oropharynx to laropharynx
- closes air passageways
How does food path through the oesophagus?
- upper oesophageal sphincter relaxed - food enters
- peristalsis pushes bolus through oesophagus
- lower oesophageal sphincter relaxes and bolus enters stomach
What are the 4 regions of the stomach?
- Fundus
- Cardiac region
- Body
- Pyloric regions
What are the functions of the stomach (3)?
- food storage
- digestion
- regulation of delivery
Where are parietal cells found?
In fundus and body of stomach
What do parietal cells secrete?
Hydrochloric acid (break down food)
Intrinsic factors (needed to absorb B12)
Which cells secrete pepsinogen?
Gastric chief cells
What is the function of pepsinogen?
Breaks down proteins into peptides
What is chyme?
Acidic fluid which passes from stomach to small intestine
Functions of the small intestine
- Neutralises stomach acid
- Adds enzymes and bile
- Breaks molecules into absorbable materials
What does peristalsis in the small intestine do?
Mixes chyme and brings it into contact with mucosa
Moves it along intestinal tract
Regions of the small intestine (3)
Duodenum, jejunum, ileum
Adaptations of mucosa in the small intestine (2)
Villi containing blood
Lacteal capillaries
What are the movements of the large intestine? (3)
- haustral churning
- peristalsis
- mass peristalsis
What are the functions of the large intestine? (3)
- Bacteria breaking down proteins and amino acid
- Final absorption of water, vitamins and ions
- Forming faeces
What are the accessory organs to digestion? (3)
- Pancreas
- Liver
- Gallbladder
What is innervation?
the process of supplying nerves to an organ or part of the body
What is the enteric nervous system?
Neurons and supporting cells throughout the digestive tract
The ENS is the largest part of the ___
Autonomic nervous system
The enteric nervous system consists of which plexuses (2)
- Myenteric plexus
- Submucosal plexus
Function and structure of the myenteric plexus
Motor neurons located between longitudinal and circular muscle
Controls GI tract motility
Structure and function of submucosal plexus
Motor nerves control secretory cells
Contains sensory nerves (chemoreceptors and stretch receptors)
What is peristalsis?
- involuntary constriction and relaxation of intestinal muscles
- creating wave-like movements that push the contents of the canal forward
Early stages of gut microbiomes colonisation coincides with ____ development
Immune
What are the 3 phases of digestion?
- Cephalic phase
- Gastric phase
- intestinal phase
What is the cephalic phase of digestion?
- seeing, thinking about or tasting food
- stimulates salivary and gastric glands to secrete saliva and gastric juice
- prepares digestive system for influx of food
What is the gastric phase of digestion?
- regulated by neural (chemo and stretch receptors) and hormonal (gastrin) mechanisms
- promotes gastric secretion and motility
What is the intestinal phase of digestion?
- when food enters the small intestine
- regulated by neural (stretch) and hormonal (secretin and cholecystokinin) regulation
What are the 3 main hormones involved in the digestive process?
- gastrin
- secretin
- cholecystokinin
