The digestive system includes the organs of the alimentary canal and accessory structures. The alimentary canal forms a continuous tube that is open to the outside environment at both ends. The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The accessory digestive structures include the teeth, tongue, salivary glands, liver, pancreas, and gallbladder. The wall of the alimentary canal is composed of four basic tissue layers: mucosa, submucosa, muscularis, and serosa. The enteric nervous system provides intrinsic innervation, and the autonomic nervous system provides extrinsic innervation.
accessory digestive organ
includes teeth, tongue, salivary glands, gallbladder, liver, and pancreas
alimentary canal
continuous muscular digestive tube that extends from the mouth to the anus
motility
movement of food through the GI tract
mucosa
innermost lining of the alimentary canal
muscularis
muscle (skeletal or smooth) layer of the alimentary canal wall
myenteric plexus
(plexus of Auerbach) major nerve supply to alimentary canal wall; controls motility
retroperitoneal
located posterior to the peritoneum
serosa
outermost layer of the alimentary canal wall present in regions within the abdominal cavity
submucosa
layer of dense connective tissue in the alimentary canal wall that binds the overlying mucosa to the underlying muscularis
submucosal plexus
(plexus of Meissner) nerve supply that regulates activity of glands and smooth muscle
By clicking on this link, you can watch a short video of what happens to the food you eat as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?
Answers may vary.
1. Which of these organs is not considered an accessory digestive structure?
A) mouth
B) salivary glands
C) pancreas
D) liver
A
2. Which of the following organs is supported by a layer of adventitia rather than serosa?
A) esophagus
B) stomach
C) small intestine
D) large intestine
A
3. Which of the following membranes covers the stomach?
A) falciform ligament
B) mesocolon
C) parietal peritoneum
D) visceral peritoneum
D
1. Explain how the enteric nervous system supports the digestive system. What might occur that could result in the autonomic nervous system having a negative impact on digestion?
The enteric nervous system helps regulate alimentary canal motility and the secretion of digestive juices, thus facilitating digestion. If a person becomes overly anxious, sympathetic innervation of the alimentary canal is stimulated, which can result in a slowing of digestive activity.
2. What layer of the alimentary canal tissue is capable of helping to protect the body against disease, and through what mechanism?
The lamina propria of the mucosa contains lymphoid tissue that makes up the MALT and responds to pathogens encountered in the alimentary canal.