05.02H THE TISSUES OF THE DIGESTIVE SYSTEM

Mrs. Jessica Romito

SUMMARY, OBJECTIVES, AND STANDARDS

Review module

• 05.02H The Tissues of the Digestive System
• Structures and functions
• More details about accessory organs and the structures of the gastrointestinal tract

Review assessment

• 05.02H assignment submission

By the end of this class you will

1. Identify the tissues of the gastrointestinal tract
2. Explain the functions of the accessory organs in digestion
3. Successfully complete assessment submission for 05.02H

STANDARDS�SC.912.L.14.45: Describe the histology of the alimentary canal and its associated accessory organs.

SC.912.L.14.46: Describe the physiology of the digestive system, including mechanical digestion, chemical digestion, absorption and the neural and hormonal mechanisms of control.

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TISSUES OF THE GASTROINTESTINAL TRACT

The organs of the gastrointestinal tract have walls made of four distinct layers:

It is the outermost layer; it secretes fluids that keep the outer surfaces moist so organs can slide against one another during digestion and movement.

It contains two sub-layers called the circular muscle layer and the longitudinal muscle layer. When these muscles contract and relax, they move the chyme through the intestinal tract.

It contains blood vessels, lymphatic vessels, and nerves.

It is the innermost layer and consists of a thin layer of epithelial cells lying on top of a base of connective tissue and smooth muscle. It contain folds called plicae circulares. These folds have tiny projections called villi that increase the area for nutrient absorption.

THE STRUCTURES OF THE MUCOSA

The mucous membrane (mucosa) of the stomach and small intestines contain glands that secrete gastric or intestinal juices for digestion.

Nutrients move into the cells of the body using the blood capillaries and lacteals within the villi of the small intestine

The villi of the small intestine provide a large surface area for nutrient absorption.

ACCESSORY ORGANS

SALIVARY GLANDS

Acinar (exocrine) cells of salivary glands secrete a fluid that contains

• water, electrolytes, mucus, and enzymes, all of which flow into collecting ducts

There are three major pairs of salivary glands:

2. parotid glands – produce a watery secretion with digestive enzymes
3. submandibular glands – produce a mixture of enzymes and mucous secretions
4. sublingual glands – secrete a saliva that is mostly mucous

Specialized cells responsible for making digestive enzymes and secretions.

Have ducts to release their secretions into the gastrointestinal tract.

Some make hormones that regulate digestion and other body functions.

ACCESSORY ORGANS

PANCREAS

produces digestive enzymes using acinar cells.

• Are secreted into tiny ducts that feed into a main pancreatic duct.

A cluster of cells, called the Islets of Langerhans, secrete insulin and glucagon directly into a capillary network that also connects with the pancreatic duct.

• These are hormones that affect blood sugar levels.

ACCESSORY ORGANS

LIVER CELLS (HEPATOCYTES)

Responsible for the production of digestive bile.

Bile moves into the gallbladder, which stores it until it is released into the small intestine.

Also has Kupffer cells that assist in blood formation and the destruction of cellular debris.

ACCESSORY ORGANS

GALLBLADDER

Receives liver bile through the cystic duct.

Releases bile into the small intestine when the smooth muscles lining its epithelia receive a signal from the hormone cholecystokinin.

• If the gallbladder is removed, the liver would simply drain its bile directly into the small intestine.
• The purpose of the gallbladder is to create a store of bile to release when large amounts of fatty foods require digestion.

ASSIGNMENT 05.02H

There is a worksheet (it is a tool to help you with the assignment, not part of the assignment itself):

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ASSIGNMENT 05.02H

ANSWER THESE QUESTIONS FROM THE LESSON AND THE PANCREAS WORKSHEET: (20 POINTS)

�1. Describe the common tissues found in the organs of the intestinal tract. (4 points) see page 2 of the module                            ��2. Describe the common tissues and structures found in accessory organs. (4 points) see page 4 of the module                                                          ��3. Describe these structures and their function in the pancreas: (6 points) see page 4 of the module              

              �Acinar cells that secrete enzymes or bicarbonate see pancreas 4x

Islet cells that secrete insulin or glucagon

Blood vessel

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4. Describe these structures and their function in the small intestines: (6 points) see page 4 of the module      

Villi

Smooth muscle

Intestinal glands

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Contact Information

Mrs. Jessica Romito

Phone Number: +1 (301) 485-9114

(text/call/WhatsApp)

Email: jromito@laurelsprings.com

Mrs. Romito's iClassroom

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LSS Live Academic Help Room

Monday–Friday 8 am to 11 pm Eastern Time�5 am to 8 pm Pacific Time

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