Digestive system Flashcards
What are the mouth/throat functions (7)
- Taste
- Chew (masticate)
- Form bolus
- Swallow
- Begin breakdown of food.
- Regulate the oesophagus/trachea.
- Speak
What is the mouth/throat anatomy to know (11)
- Lips
- Teeth (Incisors, Canines, Pre-molars, Molars)
- Gums (Gingiva)
- Tongue > Papillae > Taste buds
- Cheeks
- Hard and soft palates
- Tonsils
- Epiglottis
- Oesophagus (Trachea)
- The throat is one long tube with changing functions and a sphincter.
- all taste sensations come from all regions of the tongue, although certain parts are more sensitive to certain taste
What are the mouth/throat anatomy functions (6)
- Highly vascular - Salivation, swallowing, secreting digestive enzymes (amylase, lipase), secreting IgA and lysozyme (immune), avoids hepatic 1st pass.
- Muscular - bite force of 100-160psi
- Tongue - Taste, help chew (masticate), swallow
- Teeth - Cut, tear and chew food (mechanical break up for swallowing and digestion)
- Tonsils and adenoids - immune surveillance and response
- Pharynx/larynx and epiglottis - speak and regulate the oesophagus and trachea.
What does a healthy mouth/tongue look like (7)
- Talking
- pink lips/gums
- all teeth
- no bleeding
- able to taste
- able to swallow
- no pain
What does the potential pathophysiology of mouth/tongue look like (9)
- Missing teeth (dentures, chips)
- change in speech
- discolouration
- swelling
- halitosis (bad breath)
- bleeding
- dysphagia
- pain
- aspiration
What is the oesophagus anatomy (2)
- Oesophagus - The long, smooth muscular tube that rhythmically pushes food bolus to the stomach (peristalsis). Not designed for prolonged exposure to food/acid
- Sphincter - Strong muscular ring between oesophagus/stomach preventing acid reflux to oesophagus
What are the oesophagus functions? (2)
- Transport bolus to stomach
- Prevent reflux
What does a healthy oesophagus look like (2)
- No swallowing issues
- No acid regurgitation
What does the potential pathophysiology of the oesophagus look like (5)
- Bad breath (halitosis)
- Heartburn
- Acid reflux
- Dysphagia
- Aspiration (lung infections?)
What are the stages of swallowing (4)
- Oral preparation stage
- Oral transit stage
- Pharyngeal stage
- Oesophageal stage
What happens during the oral preparation stage of swallowing (3)
- Mastication of food
- Chewing with teeth and tongue, mixing with saliva (amylase, lipase, IgA and lysozyme)
- Bolus formation
What happens during the oral transit stage of swallowing (3)
- The front of the tongue lifts
- back of tongue depresses
- soft palate raises to block the nasal passage
What happens during the pharyngeal stage of swallowing (3)
- The larynx raises and contracts, and the epiglottis flips down to cover the airway.
- The upper oesophageal (cricopharyngeus) sphincter opens to allow bolus to enter the oesophagus.
- The upper oesophageal (cricopharyngeus) sphincter closes.
What happens during the oesophageal stage of swallowing (1)
Peristalsis (rhythmic downward pushing of bolus)
What is peristalsis (4)
- Rhythmic downward pulsing of muscular contraction
- Happens throughout the GI tract
- Pushed everything through
- Is the “urge” you feel to defecate
What are the stomach functions (5)
- Protect from pathogens
- Digest - breakdown of food
- Absorb
- Storage (c. 1L)
- Secretion
What is the stomach anatomy (7)
- A large muscular sack can distend to hold around 1 L
- A sphincter at each end that controls movement (upper and pyloric sphincter)
- Secretes pepsin and lipase to break down food
- Parietal cells secrete H+ and Cl- ions to form hydrochloric acid.
- Very acidic (HCl) to kill bacteria.
- Goblet cells secrete mucous lining to protect tissue from acid.
- Some absorption
How does stomach acid production work (5)
- pH between 1-3
- Parietal cells secrete H+ and Cl-
- Degrades proteins for digestion and defence
- Stimulated by Vagus nerve, gastrin, histamine
- Goblet cells secrete protective mucous for the stomach lining.
How does the stomach digest and absorb (5)
- Pepsin - Breaks down proteins.
- Lipase - Breaks down triglycerides into free fatty acids.
- Secretes intrinsic factor - Binds to B12 to be absorbed later
- Some drug absorption (acidic) (E.g. aspirin, ibuprofen)
- Minor site of nutrient absorption
What are the small intestine functions (4)
- Digest
- Absorb nutrients
- Absorb water
- Continue excretion of waste.
What are the small intestine anatomy and properties (6)
- 6m long (will read up to 8m)
- Attached to the posterior (back) of the abdominal cavity by the mesentery
- The major site of digestion
- The major site of absorption
- Huge surface area 250 m² (tennis court)
- Highly vascular → Liver
What are the duodenum anatomy and properties (5)
- The first part after acidic stomach
- The widest part of the small intestine
- A short (25cm) C-shape
- Where gallbladder empties
- Neutralising stomach acid
What are the jejunum anatomy and properties? (2)
- 2.5 m long
- Absorption of sugars, amino acids and fatty acids
What are the Ileum anatomy and properties (2)
- 3 m long
- Absorbs Vitamin B12 and bile acids
Gall bladder and bile duct functions (7)
- The liver secretes bile, consisting of Salts, Phospholipids, Cholesterol, Conjugated bilirubin, Electrolytes and water.
- Bile is stored in the gallbladder.
- Bile is released through the bile duct and sphincter of Oddi.
- Bile neutralises stomach acid.
- Bile emulsifies fats for absorption (with fat-soluble vitamins A, D, E and K)
- Excretes waste (e.g. bilirubin)
- In the bile duct, it mixes with pancreatic lipase (needed for fat-soluble vitamins A, D, E and K), protease and amylase.
What are the large intestine functions (4)
- Absorb water, electrolytes and vitamins.
- Form stool
- Store stool
- Continue excretion of waste.
What are the large intestine anatomy and properties (5)
- 1-1.5 m long
- Wider than the small intestine
- More fixed by mesentery than the small intestine
- Have haustra (bulged sacks) along the length – most pronounced in the sigmoid colon.
- Highly vascular with blood → Liver
What is the rectum and anus function (1)
Temporarily store faeces control defecation.
What is the rectum anatomy and properties (4)
- Connected to but distinct from colon
- Around 12 cm long
- Stores faeces
- Blood supply goes directly into circulation (avoids hepatic 1st pass)
What are the anus’s anatomy and properties (2)
- Muscular sphincter
- Controls voluntary defecation
