L1 - Mouth

Length of GI tract from mouth to anus in vivo

6-7m

The four processes carried out by the GI tract

digestion

secretion

absorption

motility

Where do contents of vomit come from

Chyme from small intestine & stomach

Digestive secretions mostly consist of what

water

How many ml of water is taken in per day

1200 ml

How many g of solids is ingested per day

800 g

ml of salivary secretions per day

1500ml

(3x my water bottle!!!)

ml of gastric secretions per day

2000ml

ml of bile secretions per day

500ml

ml of pancreatic secretions per day

1500ml

ml of intestinal secretions per day

1500ml (primarily small intestine)

How many ml are absorbed from the small intestine into the blood per day

6700ml

How many ml are absorbed from the large intestine into the blood per day

1400ml

Total fluid ml excreted per day

1500ml

How much of the total excretions per day (1500ml) are through faeces

100ml

How much solids are excreted per day

50g

Mechanical digestion in the mouth

Teeth and tongue

• Chewing action

  • Mechanical digestion

  • Reflex and Voluntary

• Tongue shapes food into bolus and pushes bolus towards pharynx

  • Motility

Pharynx

• Helps crush food digestion

• Closes nasal opening when swallowing motility

Functions of the saliva

1. Lubrication prior to swallowing

2. Digestion

• Digestive enzymes break down food

• Amylase, Lipase

3. Dissolve food

• For sensing of content

• Taste buds for the five tastes

4. Antibacterial actions (tooth decay prevention)

• Washing action

• Mucus coating of mouth

• Alkaline pH: buffers acids in food, from bacteria and gastric acids

• Bactericidal

• Antibodies

name the 4 salivary gland (3 proper & 1 isn’t really a gland)

Parotid

Submandibular

Sublingual glands

Buccal (not really a gland but secretes saliva)

Salivary flow rate

0.5ml/min to 4ml/min

What would cause saliva flow rate to increase

Mint/Lemon on tongue

Initial saliva (isotonic fluid) is produced by _________

acinar cells

Initial saliva(isotonic fluid) produced by acinar cells is modified by what

Ductal epithelial cells

Is initial saliva or secreted saliva more like plasma

Initial saliva is more like plasma as it is isotonic (not hypotonic (less water, higher solute) like secreted saliva) and has similar concentrations of Na⁺, Cl⁻, K⁺, and HCO₃⁻.

What happens to initial saliva as it passes through ductal cells

As the saliva passes through the ductal cells, it undergoes reabsorption and secretion of ions, making the final saliva hypotonic

Na⁺ and Cl⁻ are reabsorbed out of the saliva

K⁺ and HCO₃⁻ are secreted into the saliva

What regulates the process of saliva production

active transport mechanisms, including Na⁺/K⁺ ATPase pumps, which maintain ion gradients.

How do the concs of Na+, HCO3-, Cl- an K+ change with increased salivary flow rates

High Flow Rateleads to:

↑ Na⁺, ↑ Cl⁻ : less time for reabsorption of these ions out of saliva so more of it is secreted with saliva

↑ HCO₃⁻ : secretion is actively stimulated at higher flow rates. This helps buffer acidic pH, important during active digestion.

↓ K+ : not enough time to enter saliva as it is actively secreted into saliva.

What did Pavlov do

He proved that you could condition a reflex

What controls the production/secretion of saliva from acinar/ductal cells