Question

1. Identify the four layers of the gastrointestinal tract and the tissues they are comprised of. 2. When anyone mentions cheeseburgers, I always start drooling. Why does this happen and what is the saliva used for? 3. How is your body designed to keep food out of your respiratory tracts?! tes)

Answer 1

Ans.1:- The GI tract contains four layers: the innermost layer is the mucosa, underneath this is the submucosa, followed by the muscularis propria and finally, the outermost layer ,the adventitia.

• The mucosa consists of epithelium, an underlying loose connective tissue layer called lamina propria, and a thin layer of smooth muscle called the muscularis mucosa
• The submucosa is a thick layer of loose connective tissue that surrounds the mucosa. This layer also contains blood vessels, lymphatic vessels, and nerves.

• Muscularis propria are usually two layers; the inner layer is circular, and the outer layer is longitudinal. These layers of smooth muscle are used for peristalsis (rhythmic waves of contraction), to move food down through the gut.

• Adventia layer (or serosa) is the outermost layer of loose connective tissue - covered by the visceral peritoneum. Contains blood vessels, lymphatics and nerves.

Ans.2:-  Our brains subconsciously react to the smell, sight and even thought of food with the increased secretion of saliva.This is because we need saliva to help teeth chew and prepare food to be digested.The nerves that control saliva production are part of a reflex system.They fire without you consciously thinking about it when you are eating. The smells, tastes and even the movement of your jaw muscles can activate this reflex.The part of the brain responsible for this salivary reflex is the medulla oblongata.On recieving these stimuli, the medulla oblongata sends neurotransmitters to the glands to produce the saliva.

Function of the saliva

• Chemical digestion: breaks down starch by the function of “salivary amylase”
• Helps chewing and swallowing.
• Lubricating effect: moisturizes the inside of the mouth and creates smoother speech.
• Solvent effect: dissolves food and allows the tongue to taste food.

Ans.3:- The opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway thus preventing it from entering the respiratory tracts.