The Digestive System 2
Terms
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- viscera
- singula=viscus often used to designate the individual organs of digestion. However, the term is actually a general term for any organ of the abdominal or thoracic cavity.
- alimentary canal
- main part of the digestive system, also called the GI(gastrointestinal)tract. This is a generic term for the tube which extends from the lips to the anus.
- abdomen
- the part of the body from below the chest to the hips
- gut
- generally refers to the develping GI tract of an embryo
- lumen
- innermost part of the alimentary canal (plural=lumina). This is the actual cavity or hollow part of the tube. There are four layers which surround the lumen.
- mucosa
- layer of the alimentary canal that is immediately bordering the luminal cavity. It performs 3 functions: DISTENTION--state of being enlarged or allowing for an increased capacity ABSORPTION the process of absorbing or assimilating nutrients such as in the small intestine or water as in the colon SECRETION the glandular parts secrete digestive enzymes into the cavity to break down food such as takes place in the stomach
- submucosa
- second layer of the luminal cavity of the alimentary canal. This layer is highly vascular (containing many blood vessels) it is composed of elastic and collagen fibers and its function is to serve the mucosal layer.
- muscularis
- the third layer of the luminal cavity in the alimentary canal. In this layer, the contractions which move food and water through the canal occur. This process is called peristalsis and it is made possible by small circular inner muscles and larger longitudinal outer muscles. The muscularis also contains valves or sphincters which are especially thickened circular muscles which occur in strategic places within the canal to regulate food passage.
- peristalsis
- the process by which food and water are moved through the alimentary canal by contractions
- adventitia
- the fourth and final layer of the luminal cavity of the alimentary canal. This is the outer layer of the wall of the alimentary canal. It is covered by the serosa or visceral peritoneum.
- parietal peritoneum
- the lining of the coelomic cavity
- dorsal messentery
- long thin sheets of tissue which support the GI tract
- visceral peritoneum or serosa
- the covering of long thin sheets of tissue which support the GI tract continuing around the alimentary canal
- omentum
- when two organs are next to each other, these double folds of peritoneum called omentum pass between them to support and transmit vessels and nerves to and from the organs. The omentum is divided into two sections: the lesser omentum and the greater omentum.
- lesser omentum
- extends from the lesser curvature of the stomach to the underside of the liver
- greater omentum
- extends from the greater curvature of the stomach to the transverse colon.
- retroperitoneal
- organs which are positioned outside the coelomic cavity and are therefore not covered by peritoneum, they include the pancreas, kidneys, most of duodenum, and the abdominal aorta.
- buccal cavity
- another name for the oral cavity
- labium
- plural labia, means the lip
- lingual
- means "pertaining to the tongue."
- lingual frenulum
- this connects the tongue to the floor of the mouth.
- papillae
- many small elevations on the tongue
- pharynx
- serves as a common passageway for both the respiratory system and the digestive system.
- nasopharynx
- a posterior continuation of the nasal cavity and is not actually part of the digestive system
- uvula
- a small fleshy mass which hangs from the soft palate just above the tongue
- oropharynx
- extends from the soft palate within the mouth to the level of the hyoid bone
- epiglottis
- a lid-like structure composed of cartilage which hangs over the entrance to the larynx to prevent food from entering the larynx or trachea upon swallowing.
- esophagus
- the part of the alimentary canal which connects the pharynx to the stomach. It is a muscular tube that is 25 cm long. The muscular function of the esophagus is not voluntary.
- bolus
- a rounded mass of food
- stomach
- most distended portion of the alimentary canal. It serves primarily as storage for food before it passes into the intestines. Although some digestion occurs at this point, food is primarily converted into a pasty material.
- What are the four parts of the stomach?
- cardiac orifice, fundus, body of the stomach, and the pylorus
- cardiac orifice
- the juction between the esophagus and the stomach. This is also frequently referred to as the "GE junction" (gastroesophageal junction) the muscles are in constant state of contraction in order to prevent the stomach contents from flowing backward.
- fundus
- dome-shaped portion of the stomach which extends slightly above the cardiac orifice.
- body of the stomach
- the widest portion of the stomach and is located between the lesser and greater curvatures.
- pylorus
- the last area of the stomach just before the duodenum
- small intestine
- the lonogest portion of the slimentary canal. It measures apporximately 21 feet long and is 2.5 cm wide.
- What are the three regions of the small intestine?
- the duodenum, jejunum, and the ileum
- duodenum
- first region of the small intestine that receives secretions from the liver and the pancreas.
- jejunum
- the second region of the small intestine
- ileum
- the final portion of the small intestine. The small intestine makes the transition to the large intestine here through what is called the ileocecal valve.
- large intestine
- the distal-most portion of the alimentary canal. It is so named because at 6 cm in diameter, it is the widest portion of the canal.It is here that most water is absorbed and feces are formed.
- What are the four major regions of the large intestine?
- the cecum, colon, rectum, and anal canal/anus
- ileocecal valve
- makes the transition from the small to the large intestine
- cecum
- opens into the colon and has the appendix, a small finger-like projection which is attached to its medial portion.
- colon
- second portion of the large intestine. Different areas of the colon have specific terms asssigned to them.
- ascending colon
- part of the colon, arises from the cecum and goes in an upward direction (ascends)
- hepatic flexure
- part of the colon, where at approximately the liver the colon bends sharply.
- transverse colon
- part of the colon where it extends in a horizontal direction.
- splenic flexure
- part of the colon, at the left abdominal wall, where there is another sharp bend in the colon
- descending colon
- the portion of the large intestine which goes downward (descends)
- sigmoid colon
- the colon terminates in a S-shaped bend
- What are the six parts of the colon, which is in the large intestine?
- the ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and the sigmoid colon.
- rectum
- a tube in the large intestine approximately 15 cm long which is located between the sigmoid colon and the anal canal.
- anal canal/anus
- part of the large intestine where a muscular opening is formed in the muscles of the pelvic floor called the anus. the is surrounded by both involuntary and voluntary muscular sphincters.
- teniae coli
- three distince longitudinal muscles which run the length of the large intestine
- sacculations or haustra
- a series of bulges in the wall of the large intestine
- liver
- the largest gland in the body. It is made up of many liver lobules which produce bile which is continuously secreted into the intestines and is very important to digestion.
- gallbladder
- a sac-like organ which is attached to the undersurface of the liver. It stores and concentrates bile.
- pancreas
- it is involved in both the digestive and endocrine systems. For its role in digestion, it creates juices and secretes them into the duodenum for the breakdown of foods.