Salivary Secretions💧

What are the 5 primary roles of saliva?

1. Moistens and lubricates

2. pH neutralization

3. Reduces osmolarity of digesta

4. Antibacterial properties

5. MINOR contribution to enzymatic digestion in some species (NOT ruminants)

How does saliva act as a pH neutralizer?

Duct cells release bicarbonate

How does saliva reduce osmolarity of digesta?

Saliva reduces osmolarity by adding water to digesta

Why does saliva begin minor enzymatic digestion in certain species?

Saliva contains enzyme alpha-amylase to begin minor break down of starch

What are the 3 salivary glands?

1. Parotid

2. Sublingual

3. Submandibular

What are the 2 types of acinar cells in the salivary glands?

1. Mucus acinar cells

2. Serous cells

What is the role of duct cells in the salivary glands?

Duct cells:

• Reabsorb Na+ and Cl-

• Secrete K+ and HCO3-

What do mucus acinar cells secrete?

Mucus

What is in mucus and how does it help with swallowing?

• Mucus is a glycoprotein that holds water and gives lubrication properties

• Lubrication helps with swallowing movement down to GIT

What species have the most mucus/saliva?

Chickens

What do serous cells secrete?

A watery, protein-rich fluid that contains:

• Ions (Na+, Mg2+, Ca2+)

• Digestive enzymes (a-amylase in omnivores)

• Salivary lipase: Triglyceride digestion

• Lysozyme: Anti-bacterial properties (no digestion)

Salivary lipase in serous secretion is primarily seen in _______ mammals.

Suckling

How is regulation of saliva secretion affected by the endocrine system?

A decrease in pH of the GIT will increase secretin, which is released into the bloodstream. Secretin act on duct cells, increasing bicarbonate secretion.

How is regulation of saliva secretion affected by the nervous system?

Activated by the parasympathetic nervous system by:

• Anticipation of eating

• Sight/smell

• Activation of taste receptors

• Chewing

Which species has the highest quantity of bicarbonate in their saliva?

Non-ruminants have the highest level of bicarbonate in order to maintain pH levels in the rumen to neutralize VFA’s

What species DO NOT have a-amylase in their saliva?

Carnivores and ruminants

Salivary lipase helps with minor fat digestion, especially suckling animals. All animals contain salivary lipase except:

Birds have no lipase

Which species saliva does not contain lysozymes? Why?

Ruminants do not have lysozymes (anti-bacterial enzymes) because their rumen is filled with bacteria

What is the saliva composition in ruminants?

Ruminants: Mucus, Bicarbonate, Lipase

What is the saliva composition in non-ruminants?

Non-Ruminants: Mucus, Bicarbonate, a-amylase, Lipase, Lysozyme

What is the saliva composition in carnivores?

Carnivores: Mucus, Bicarbonate, Lipase, Lysozyme

What is the saliva composition in birds?

Birds: Mucus, Bicarbonate, a-amylase, Lysozyme