2.2 What happens in the cephalic stage? Firstly, food is taken into the mouth and then broken down into smaller pieces by ‘mechanical digestion’ (or the using the teeth to break down food). Saliva in the mouth is produced due to the neural reponses which come about from the stimulus of the eyes, head, smell etc. An enzyme in the saliva called amylase begins the chemical digestion by breaking down ‘complex carbohydrates into simple sugars’. When the food is ready to be swallowed, the food is now called a soft mass called a ‘bolus’.
CheckPoint: Human Digestion I am describing, the path food follows through the digestive system and how digestion occurs in each of the following parts of the digestive system. I am including in the description of other organs or components of the digestive system, including: * Large intestine * Mouth * Small intestine * Stomach After the food enters the mouth and after being moistens and chewed by the teeth, the food then converts into a Bolus. Bolus as mentioned refers to the softened mass of munched on food that passes through the digestive system. The bolus then exits the mouth and progresses into the pharynx. The bolus then moves down into the esophagus, which follows to the stomach.
The pancreas secretes trypsin and chymotripsin. The liver and gall bladder secrete bile, used for the emulsification of fats. The second section of the small intestine, the jejunum, is where the majority of food is absorbed into the bloodstream. The last section of the small intestine, the ileum, is where the remainder of nutrients is absorbed. What is not absorbed by the small intestine passes into the large intestine, which includes the colon and rectum.
Which substances, other than gastric acid, are secreted by the stomach? Describe their secreted and physiological roles. o Two main tubular glands are present in the stomach mucosa: • Oxyntic/gastric glands • Pyloric glands In addition, mucus-secreting cells line the entire surface of the stomach (surface mucous glands). These secrete large quantities of a very viscid mucus that coats the stomach mucosa with a gel layer of mucus, often more than 1mm thick. These glands provide a major shell of protection for the stomach wall and contribute to lubrication of food transport.
It coats the chewed food and transforms it into what is called a bolus. An enzyme called amylase found in the saliva breaks down the carbohydrates in the bolus into simpler sugars. By breaking down the food, the bolus becomes mushy, slippery and easy to swallow. The tongue also plays a big role in helping digest food in the mouth. It helps taste, transport and swallow food.
The small intestine is the principal site of digestion and absorption. Enzymes from the pancreas, liver, gallbladder, and the small intestine itself combine to break down nutrients so that they can be absorbed. The pancreas supplies enzymes to digest proteins, fats and carbohydrates. The live produces bile required for emulsification of fat, and the gallbladder stores the bile until it is needed. The absorption of nutrients in the small intestine is facilitated by tiny projections called villi, which provide more surface area for absorption.
The mouth receives food and begins digestion by mechanically reducing the size of the solid particles and mixing them with saliva. Pharynx – The pharynx is in both the respiratory system and digestive system. The pharynx is a muscular tube, at the back of your throat when the nose and mouth join. This serves as a passageway for food and air. The tube being so muscular helps an individual with swallowing.
In the exogenous path the Epithelial, cell lining also known as the small intestines, readily takes in lipids from the food. These lipids including phospholipids, cholesterol and triglycerides, merge with apolipoprotein B-48. In their circulation via the lymphatic vessels, the nascent chylomicrons pass the liver circulation and draining through the thoracic duct and into the bloodstream follows. In the bloodstream, High Density Lipid particles donate apolipoprotein E and apolipoprotein C-II to the nascent chylomicron that is now mature. Through apolipoprotein C-II, the mature chylomicrons activate lipoprotein lipase (LPL).
Plasma and red blood cells transport substances to or away from cell. White blood cells and platelets are parts of the immune system. Blood plasma is mostly made up of water which is from respiration and is absorbed from the large intestine. Water can also be reabsorbed from the kidney. This is very important as this allows osmosis occurs in our bodies.