The Digestive System

Chapter 15

Mrs. Carter’s A&P Notes

*Copy these into your notes handouts, and

complete the SG given.

Digestive System Overview

• The oral cavity (mouth) contains the tongue and the teeth.

• Salivary glands produce saliva, a mixture of mucus and

enzyme (amylase), and empty into the oral cavity.

• Located behind the mouth is the throat

(pharynx).

The pharynx is divided into three

parts, and the two digestive components are the

(1) oral pharynx and the (2) laryngopharynx,

which function in swallowing and the passage of

food.

Digestive System Overview:

• Swallowing forces food into the esophagus, the tube that

descends from the pharynx to the stomach.

• The small intestine is a long twisted tube that extends

from the stomach to the large intestine.

– The duodenum receives a liquid mixture of food from the

stomach called chyme and secretions from the liver and the

pancreas.

– The liver produces bile which contains bile salts for the

emulsification of fats.

– The pancreas produces pancreatic juice which contains two

major components, (1) enzymes for digestion and (2)

bicarbonate ions for adjusting the acidic chyme toward

neutral.

– The ileocecal valve regulates the emptying of the small

intestine.

Digestive System Overview • The large intestine is divided into the:

(1) cecum, (2) appendix, (3) colon, (4) rectum, & (5) anal

canal.

– The sigmoid colon joins the rectum, which terminates

at the anal canal. The short anal canal terminates at

the opening to the outside called the anus.

• The wall of the alimentary canal is organized

from the esophagus to the anal canal into four

distinctive layers.

Located from the inside to the

outside, the layers of the wall are called the

– (1) mucosa,

– (2) submucosa,

– (3) muscularis

The Digestive System

Notes

A. The digestive system can be divided

into two major parts:

(1) the alimentary canal

(gastrointestinal, or digestive tract) and

(2) the accessory organs.

1. The digestive tract is the tube that extends from the mouth

to the anus, and it consists of the:

(1) mouth, (2) pharynx, (3) esophagus,

(4) stomach, (5) small intestine, and (6) large intestine.

2. The accessory organs include the (1) teeth,

(2) tongue, (3) salivary glands, (4) liver, (5) gallbladder, and

(6) pancreas.

15.1 Digestive System

1. Function: mechanical and

chemical breakdown of food

including:

***ingestion, digestion,

absorption, elimination,

propulsion, secretion***

2. Consists of alimentary

canal and accessory organs

Functions:

3. The movement of digestion products,

electrolytes, vitamins, and water across

the GI tract epithelium and into the

underlying blood and lymphatic vessels

is called absorption.

4. The main

function of the

small intestine is to

secrete chemicals

that break down

food and carry the

nutrients away in

the blood stream.

In one word:

ABSORPTION

Wall of the Alimentary Canal

5. Movements in the

small intestine that

churn the materials

being digested and

mix them with

intestinal secretions

are called

segmentation.

6. Peristalsis – term

that describes the

wave of muscular

contraction that moves

material through the GI

tract toward the

anus….. (a.k.a “pushes food down

the tube”)

7. Your stomach is a digestive organ

that mechanically and chemically

transforms a food bolus into chyme.

B. The order food through the digestive tract…

The digestive tract is the tube

that extends from the mouth to

the anus, and it consists of the:

1. Mouth

2. Tongue (salivary glands)

3. Esophagus

4. Stomach

5. (Liver and gallbladder help)

6. Small intestine

7. Large intestine (aka colon)

8. Rectum

9. Anus

C. Accessory Digestive Organs

1. The accessory organs include the

(1) teeth,

(2) tongue,

(3) salivary glands,

(4) liver,

(5) gallbladder,

(6) pancreas

Anatomy of the Mouth

Anatomy of a Tooth

2. Anatomy of a Tooth a. Dentin – Makes up the majority of the

inner surface of the tooth. It cannot

normally be seen except on x-rays.

*The mineralized matrix, that is similar

to bone, but harder, that forms the primary

mass of each tooth.

b. Enamel – Makes up the protective outer

surface of the crown of the tooth.

c. Pulp – the area in the center the tooth

that holds the nerves and blood vessels,

and is in both the crown and root.

d. Cementum –outer surface of the root of

the tooth. It is much softer than enamel.

3. Teeth (by shape):

a. Incisors – 4 front teeth,

responsible for cutting and

biting food; act like

scissors

b. Cuspid (canine) – one root

and conical with a pointed tip.

c. Premolars – 1 or 2 roots

and flat crowns with cusps

d. Molars – 3 or more roots

and large, broad, flat crowns.

Tooth Decay

METH

MOUTH

ROOT CANAL

4. Salivary Glands – 3 pairs of multicellular

glands that secrete into the oral cavity

a. Parotid –

ear, cheek

b. Submandibular -

below jaw

c. Sublingual -

under tongue

5. Digestive functions of the tongue include:

a. Manipulating and mixing ingested

materials during chewing.

b. Assisting in the swallowing

process.

c. Helping compress partially

digested food to form a bolus.

6. Three phases of swallowing process:

a. Voluntary

b. Pharyngeal

c. Esophageal

II. 15.2 Characteristics of the Canal A.** From deep to superficial, the tunics of the

intraperitoneal portions of the GI tract are:**

1. Mucosa - protects tissues and carries absorption

2. Submucosa - glands, blood vessels, nerves

3. Muscularis (Muscular Layer) - smooth muscle tissue,

inner circular layer and an outer longitudinal layer, with the

myenteric nerve plexus in between; this tunic pushes

food (PERISTALSIS)

4. Serosa (serous layer) - visceral perioneum, outer

covering of the tube, lubricates surfaces (serous fluid)

B. Layers of GI tract & it’s tissues…

1. Each layer is made

up of different types of

cells and tissues…

2. Within the

mucous

membrane of the

GI tract, the layer

of areolar

connective tissue

is called the

lamina propria.

Layers of GI tract & it’s tissues…

3. The

cecum,

colon, and

rectum all

are

composed

of simple

columnar

epithelium.

Pharynx:

3 parts include-

a. nasopharynx

b. oropharynx

c. laryngopharynx

C. Esophagus 1. The esophagus enters

the abdominal cavity

through the esophageal

hiatus is where it enters

the diaphragm, before

entering the stomach.

Esophagus - Anatomy

2. Histological features (tissue layers) of the

esophageal wall include an outer fibrous layer,

the adventitia, with no serosa.

D. Stomach

1. Regions from

Superior to Inferior

end of stomach:

a. Cardiac

b. Fundus

c. Body (greater

and lesser

curvature)

d. Pyloric

2. STOMACH MUSCLES:

Longitudinal, Circular, Oblique

3. Stomach Lining:

a. Gastric Juices contain acids that break down

food - secreted by gastric glands

b. PEPSIN - most important digestive enzyme

for breaking down food

c. Mucus prevents stomach

from digesting itself

4. Chyme - paste, after food has been broken down,

released then into the duodenum via the pyloric

sphincter valve

5. Rugae –

prominent folds

within the stomach

that nearly

disappear when

the stomach

expands.

6. Gastric Pits

contain glands to

make juices

E. PANCREAS - secretes

insulin which breaks down

sugars.

1. *Hormones:

Cholecystokinin and

Secretin stimulate the

production of pancreatic

juice and bicarbonate.

2. Pancreatic Juice also

breaks down fat.

F. Liver

1. 1 large right lobe | 1 smaller left lobe

2. Liver ducts and vessels

a. Hepatic duct --> to common bile duct

b. Hepatic portal vein - circulates blood

throughout liver

3. Liver Functions: a. blood glucose levels

b. breakdown of lipids and fats

c. protein metabolism

d. stores vitamins

e. destroys damaged RBCs

f. removes toxins

g. production of bile

Remember Bili Lights?

Using bili lights is a therapeutic procedure performed on newborn or

premature infants to reduce elevated levels of bilirubin. If blood levels

of bilirubin become too high, the bilirubin begins to dissolve in the body

tissues, producing the characteristic yellow eyes and skin of jaundice.

G. Gall Bladder:

a. under liver

b. cystic duct --> common bile duct

c. stores bile,

d. digests fat

e. *gallstones may form

H. Small Intestine

1. Starts at the pyloric

sphincter & 3 sections

(superior to inferior):

a. Duodenum

b. Jejunum

c. Ileum

2. *Mesentery = Membrane holds it

together, contains blood vessels

I. Greater Omentum a. "curtain-like" membrane, or the

mesentery, that covers most of the internal

organs, extending inferiorly like an apron from

the greater curvature of the stomach.

b. stores fat and lays like a drape

Greater Omentum

J. Villi – (found in small intestines) to

increase surface area for absorption of

nutrients, and secretion, connect to vessels.

K. Large Intestine:

1. Order from ileum

to anus:

a. Cecum

b. Colon

(4 parts in order of travel):

Ascending

Transverse

Descending

Sigmoid

c. Rectum

d. Anal canal

2. Function of Large Intestine

a. Secretes mucus, reabsorbs water, contains

bacteria to aid in digestion (intestinal flora)

b. Mass Movements (defecation) - removes

undigested food

c. The main job is

WATER

REABSORPTION...

3. Mucosa of Large Intestine:

Characterized by:

a. lack of intestinal villi

b. many lymphatic nodules and cells in the lamina

propria

c. numerous goblet cells and intestinal glands

http://youtube.com/v/dFdRqoVSZPE

LABEL THIS!

1. esophagus

2. liver

3. stomach

4. pyloric sphincter

5. duodenum

6. pancreas

7. jejunum

8. ileum

9. cecum

10. appendix

11. ascending colon

12. descending colon

13. sigmoid colong

14. anus

Nutrition

III. Disorders of the Digestive System

1. GERD

Gastroesophageal

reflux disease

Digestive System Aging:

2. Age-related changes in the

digestive system include:

a. diminished muscle tone

b. diminished GI tract mobility

c. decreased replacement of

epithelial cells

d. reduced secretion of mucin,

enzymes, and acid

3. Dysentery or Diarrhea

4. HEPATITIS A, B, C

Hepatitis A

i-s caused by eating food and drinking water infected with a virus

called HAV.

While it can cause swelling and inflammation in the liver, it doesn't

lead to chronic disease.

Almost everyone who gets hepatitis A has a full recovery, some may

need hospitalization.

Many people are recommended to receive hepatitis A vaccine,

including people at increased risk for exposure to hepatitis A virus

infection and people who are more likely to get seriously ill if infected

with the virus.

Hepatitis B is caused by the virus HBV.

It is spread by contact with an infected person's blood, semen,

or other body fluid. And, it is a sexually transmitted disease

(STD).

Some people never develop symptoms, others develop chronic

symptoms that stay with them their whole life.

Hepatitis C is caused by the virus HCV. It is spread the same

way as hepatitis B, through contact with an infected person's

blood, semen, or body fluid (see above).

Like hepatitis B, hepatitis C causes swelling of the liver and

can cause liver damage that can lead to cancer. Most people

who have hepatitis C develop a chronic infection. This may

lead to a scarring of the liver, called cirrhosis.

Blood banks test all

donated blood for

hepatitis C, greatly

reducing the risk for

getting the virus from

blood transfusions or

blood products.

5. Crohn’s Disease

6. IBS - Irritable Bowel Syndrome

7. STOMACH ULCERS

8. Lactose

Intolerance -

Inability to digest milk

or milk products, can

cause stomach upset

9. Appendicitis

10. Hernia -

intestines poke

through

abdominal

muscles

11. When people with celiac

disease eat foods or use

products containing gluten,

their immune system responds

by damaging or destroying villi

Without healthy villi, a person

becomes malnourished, no

matter how much food one

eats.

12. Gallstones (Cholelithiasis)

Gallstones are made from cholesterol and other

things found in the bile. They can be smaller than a

grain of sand or as large as a golf ball.

13. Gastric Bypass Surgery Gastric bypass surgery makes

the stomach smaller and causes food

to bypass part of the small intestine.

You will feel full more quickly than

when your stomach was its original

size. This reduces the amount of food

you can eat at one time. Bypassing

part of the intestine reduces how

much food and nutrients are

absorbed. This leads to weight loss.

http://www.hurtbyadoctor.com/Gastric

-Bypass-Surgery-Malpractice-

Lawsuits-Information-Home.htm

14. Colon Cancer

Colonoscopy is a screening technique to detect cancer.