Flashcards in Chapter 23 - The Digestive System Deck (78)
General Anatomy of the Digestive Tract
A long tube to which a series of accessory glands are attached.
Regions of the Digestive Tract
There are 5 regions:
Mouth, esophagus, stomach, small intestine, large intestine.
Layers of the Digestive Tract
The membrane that lines the lumen. It contains stratified squamous epithelium and around the stomach changes to simple columnar epithelium. It has some areolar tissue and smooth muscle. Functions in secretions, absorption of food products into the blood, and protection against infections.
A thick layer of either dense or areolar connective tissue. Has a vascular network, blood vessels, lymphatics, nerves, and glands. Function to carry away absorbed nutrients.
A double layer or smooth muscle. The inner layer has fibers arranged in circles. The outer layer's fibers are arranged longitudinally. The circular layer sometimes forms a valve, a sphincter, to propel and mix food.
Connective tissue, called the visceral peritoneum. In the esophagus, it's called adventitia.
Intrinsic Nerve Plexuses
Nerve complexes found between the tunics.
The wall of the tract contains a large number of glands, there are three glands that lie outside the tract and dump their secretions into the tract via ducts.
3 pairs of glands. Produce saliva which enters the mouth. The parotids, the submandibular, and the sublinguals.
Parotid Salivary Glands
Largest of the pairs, located beneath the ears. If they become inflamed, it's called the mumps.
Submandibular Salivary Glands
Lie medial to the angle of the mandible
Sublingual Salivary Glands
On the floor of the mouth, beneath the tongue. Has 2 kinds of secretions: serous, or watery, and mucus secretions which are viscous due to mucin.
Large gland is located beneath the stomach. It produces pancreatic juice which contains many digestive enzymes, by the acini cells.
The largest organ in the body, it's divided into left and right lobes. It has cords and cells that radiate outward from the center. It has a capillary network of sinusoids. It has a falciform ligament that separates the right and left lobes.
The hepatocytes in the liver secrete bile into the hepatic duct.
Function of the liver
-production of albumin and other plasma proteins
-manufactures prothrombin and other blood clotting factors
-regulates carbs, proteins, and lipid metabolism
-synthesizes and stores glycogen
-produces waste products like urea and ketone bodies
-stores iron, vitamin A,D,K and E.
-detoxifies most materials toxic to body cells
plays a role in body defense
Stationary contractions along the digestive tract. They mix the food
Wave-like contractions to move material down the tract
Control of Flow
The directional movement of materials throughout the tract is regulated by a series of valves that are often referred to as sphincters.
Mouth and Pharynx
The mouth and oral cavity are the first parts of the tract. They extend from the lips to the oropharynx. The digestive activities include:
Analyze the food before it's swallowed
Chewing, breaking down into smaller sizes to provide a greater surface area for enzymes to work on.
Has glands that secrete an enzyme, lingual lipase, which breaks down lipids. Also has taste buds and papillae. Has intrinsic muscles which allow it to change it's shape, and extrinsic muscles which change the position of the tongue. It's held to the floor of the mouth via the lingual frenulum.
While chewing, saliva is produced.
Composition of Saliva
About 97% water. Has mucin, electrolytes, and salivary amylase.
The food bolus is forced into the pharynx by the tongue. Series of reflexes close off other opening into pharynx. Esophagus opens, food bolus is forced in, peristaltic waves move the bolus down the esophagus to the stomach.
A muscular tube that goe from the pharynx to the stomach. About 25cm long. The upper part has skeletal muscle which transitions into smooth muscle. The skeletal muscle helps in swallowing. Where the esophagus meets the stomach is called the cardiac orifice or z-line, and the epithelium changes from squamous to columnar.
Large, long folds that are present when the stomach is empty.