Organs of the alimentary canal and associated organs in relation to the processes Flashcards
What is the structure of mouth, buccal cavity and salivary glands
Ingestion: Food enters the body via the mouth which leads to the buccal cavity
The buccal cavity contains the muscular tongue and is supported by the fixed upper and movable lower jaws in which the teeth are set in sockets
Three pairs of salivary glands open into the buccal cavity via ducts
How does mouth, buccal cavity and salivary glands affect digestion
Digestion: In the mouth, solid food is broken up into small pieces by the grinding action of the teeth mechanically. Mastication reduces food to small particles, increasing the surface area on which enzymes act
The tongue rolls the food into boli (Mastication facilitates swallowing)
Food in the mouth stimulates salivary glands to secrete saliva
What are found in saliva
Mucus which helps to lubricate and soften the bolus for ease of swallowing
Salivary amylase which catalyses the hydrolysis of starch to maltose
Lysozyme which reduces bacterial contamination
Structure of oesophagus
The oesophagus is a straight, narrow, thick-walled muscular tube that leads from the pharynx to the stomach
The glands of submucosa secrete mucus into the lumen, lubricating the passage of the bolus
The bolus is propelled down the oesophagus towards the stomach by a wave of muscular contraction and relaxation (Peristalsis)
Structure of the stomach
The stomach is a distensible muscular bag with thick and well-developed muscular walls
It lies immediately beneath the diaphragm to the left side of the abdominal cavity.
The lining of the stomach has numerous pits, the walls of which are lined with gastric glands that produce gastric juice
The pyloric sphincter is a circular band of muscle at the lower end of the stomach which stops solid pieces of food from passing through
How does stomach affect digestion
The regular, peristaltic movements of the stomach, break up food particles and mix up the food and gastric juice into chyme. This is released in small quantities at a time to the duodenum when the pyloric sphincter relaxes and opens
Mucus-secreting cells in the gastric glands secretes mucus that protects the stomach lining and glands from self-digestion by pepsin (May lead to stomach ulcers)
Structure of the small intestine
Two main regions: Duodenum and ileum
Duodenum receives bile from the gall bladder and pancreatic juice from the pancreas
How does the small intestine affect digestion
The pancreas secretes pancreatic juice which passes through the pancreatic duct into the duodenum. Epithelial cells are slough off and replaced at a rapid rate. When epithelial cells are shed, the intracellular and brush border enzymes are released into the intestinal lumen
The gall bladder releases bile (A green and watery fluid made in the liver) which passes through the bile duct into the duodenum. The pancreatic juice, secretions from the intestinal glands and bile are alkaline, so they neutralise the acidic chyme and provides a suitable medium for the action of pancreatic and intestinal enzymes
How does bile help with digestion in the small intestine
The gall bladder releases bile (A green and watery fluid made in the liver) which passes through the bile duct into the duodenum.
Bile also contains bile salts which emulsify fats and break them up into small fat globules that greatly enlarge the surface area of fats to speed up their digestion by pancreatic lipase
Structure of the large intestine
It consists of ascending colon, horizontal transverse colon, the descending colon and the rectum.
The materials passing into the large intestine consists of water with undigested matter, largely cellulose and vegetable fibres, mucus and dead cells from the lining of the alimentary canal
What is the function of the large intestine
A major function of the large intestine is to absorb water and dissolved mineral salts
What is the function of the rectum
The undigested material is stored temporarily in the rectum before it is discharges as faeces through the anus (Egestion)
