Alimentary Canal: Esophagus to Stomach
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What is the length?
esophagus--> end of the intestines or anal canal
Wall of the alimentary canal.
Beginning with the luminal surface, it has the tunica mucosa, tunica submucosa, tunica muscularis, tunica adventitious (or serosa)
Explain the tunica mucosa.
mucous memrane that is epithelium (type depends on organism) contianing mucous cells, which help protect the walls from digestive enzymes in the tube; also forms the digestive glands, which lie int he tunica mucosa
CT layer that contains BVs, lymphatic vessels, and nerves, which are all part of the autonomic NS, which controls movement of the bolus through the tube (peristalsis)
layer through which absorption occurs; the food enters the mucosa and then the submucosa, where it enters the capillaries and gets absorbed into the lymphatic system
Made of smooth muscle.
- There are two orientations to that smooth muscle:
- - inner circular orientation and then an outer longitudinal layer
Movement of the tunica muscularis
The kind of movement that takes palce in the tube is a rhythmic movement called peristalsis, which moves the bolus down the tube
This is controlled by the ANS
Tunica Adventitious (or serosa)
Just a CT layer, which anchors the tube to the body wall and that is found in the esophageal region and the rectal/ anal canal area
- helps prevent friction
What is serosa?
It is a serous membrane which is CT and epithelium and is the peritoneum
It is a double walled membrane: outer is parietal peritoneum and inner is the visceral peritoneum
on the surface of the viscera, which allows it some movement, whereas the esophagus is a more fixed region of the tube
- connects the pharynx to the stomach
- It is in most vertebrates just a transport tube for food
- the only vertebrates whose esophagus secretes some digestive enzymes are amphibians-- the esophagus has digestive glands to secrete a particular enzyme. It does not function in the esophagus, but releases its products there
- No digestion
- In some vertebrates that swallow large amounts of food at once, the esophagus acts as a temporary storage
Vertebrate stomachs can have two shapes, depending on the animal's body: straight or J-shaped
In all vertebrate stomachs,...
- the mucosa is in irregular folds of mucous membrane called rugae
- - empty stomach: all of these fold in
- - filled stomach: mucosa distends
- Essentially, the function is to allow for distendability
At the end of the stomach?
is the pyloric sphincter, going around the tube to control passage to the next part of the tube
Two major functions of the stomach
1) churning: a movement in the alimentary canal where the bolus is thrown back and forth to break into small pieces; digestive enzymes are not gonna function properly in a solid mass of food; mix with gastric juice; chyme is the small bits of chewed food mixed with gastric juice; only in the stomach
Begins the digestion of proteins: pepsinogen is a zymogen and HCl cleaves it into pepsin`
Narrow region of the stomach is the __.
What is the pyloric valve made of?
pylorus--> smooth muscle that helps regulate flow of chyme from stomach to intestine
- fish, amphibians, and reptiles:
increses in specialization up the chain (becomes more differentiated/ specialized)
divided into proventriculus (gastric glands) and ventriculus (gizzard), the latter of which is a muscular compartment where grain is chopped up (mechanical digestion)
well developed, modified structure modified in (ruminants) that they display multiple chambers that help in the digestion of cellulose
- reticulum, omasum, abomasum, rumen
forms "Cud," a chamber that holds chewed material so it can be regurgitated--> chewed
chewed food mixed with water and salts
gastric glands and rugae (increase surface area) and is site of enzymatic activity
where digestion via bacteria occurs (site of cellulose digestion)
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