Page 6 - 86 human physiology part-2

The Gastrointestinal System

Enzyme Produced In Site of Release pH Level
Carbohydrate Digestion:
Salivary amylase Salivary glands Mouth Neutral
Pancreatic amylase Pancreas Small intestine Basic
Maltase Small intestine Small intestine Basic
Protein Digestion:
Pepsin Gastric glands Stomach Acidic
Trypsin Pancreas Small intestine Basic

Peptidases Small intestine Small intestine Basic
Nucleic Acid Digestion:
Nuclease Pancreas Small intestine Basic
Nucleosidases Pancreas Small intestine Basic
Fat Digestion:
Lipase Pancreas Small intestine Basic

Esophagus

The esophagus (also spelled oesophagus/esophagus) or gullet is the muscular tube in vertebrates
through which ingested food passes from the mouth area to the stomach. The esophagus is continuous
with the laryngeal part of the pharynx at the level of the C6 vertebra.

Food is passed through the esophagus by using the process of peristalsis. It connects the pharynx,
which is the body cavity that is common to both the digestive and respiratory systems behind the
mouth, with the stomach, where the second stage of digestion is initiated (the first stage is in the mouth
with teeth and tongue masticating food and mixing it with saliva).

Histology

The esophagus is lined with mucus membranes, and uses peristaltic action to move swallowed
food down to the stomach.

The esophagus is lined by a stratified squamous epithelium, which is rapidly turned over, and
serves a protective effect due to the high volume transit of food, saliva, and mucus into the stomach.
The lamina propria of the esophagus is sparse. The mucus secreting glands are located in the
submucosa, and are connective structures called papillae.

The muscularis propria of the esophagus consists of straited muscle in the upper third (superior)
part of the esophagus. The middle third consists of a combination of smooth muscle and straited
muscle, and the bottom (inferior) third is only smooth muscle. The distal end of the esophagus is
slightly narrowed because of the thickened circular muscles. This part of the esophagus is called the
lower esophageal sphincter. This aids in keeping food down and not being regurgitated.

The esophagus has a rich lymphatic drainage as well.

Wikibooks | 221