Booklet 1

Question 1

What are the two sections of the digestive system?

Answer 1

Alimentary canal
(gastrointestinal tract)
Accessory organs

Question 2

What are the functions of the digestive system?

Answer 2

1. Ingestion- taking in food
2. Propulsion- movement of food
3. Digestion & absorption- breaking down food & taking in nutrients
4. Egestion- elimination of waste

Question 3

What is in the Alimentary Canal?

Answer 3

mouth
pharynx
esophagus
stomach
small intestine
large intestine

Question 4

What is in the Accessory organs?

Answer 4

teeth
tongue
salivary glands
liver
gall bladder
pancreas

Question 5

What are the layers of the alimentary canal from superficial to deep?

Answer 5

Serosa
(visceral peritoneum)
-membrane that secretes a slippery, watery fluid
-reduces friction as digestive organs contract and move

Muscularis
Layer of muscle extending in two directions:
-circular layer
-longitudinal layer

Submucosa
Contains glands, nerve fibers and blood vessels

Mucosa
-functions:
1. secreting mucus, digestive enzymes, & hormones
2. absorption of nutrients
3. protection from pathogens (lymphatic tissue)

Question 6

How do teeth aid in digestion?

Answer 6

Teeth are accessory digestive organs.
They are responsible for beginning the mechanical digestion process

Question 7

Anatomy of Teeth

Answer 7

Incisors: Used for cutting pieces of food

Canines (cuspids): tear and pierce

Premolars (bicuspids): used for crushing

Molars (tricuspids): used for grinding

Question 8

Anatomy of a tooth

Answer 8

Enamel: hard, protects tooth

Dentin: calcified connective tissue

Pulp cavity: contains blood vessels and nerves

Gingivae (gum): provides seal around tooth

Cementum- covers the dentin in the root

Bone of jaw

artery

vein

Question 9

How do child’s teeth differ from adult teeth?

Answer 9

Toddlers have only 20 teeth, compared to an adult’s 32.
The incisors come in first (6-8 months) followed by the canines and molars.
Even after these teeth are replaced with permanent teeth, molars come in during teens and early twenties.

Question 10

What other digestive structures are found in the mouth?

Answer 10

Salivary glands produce saliva:
99% water

Mucus (lubricates food for swallowing)
Amylase (breaks down starch)
Lysozymes (kills bacteria)
Antibodies (mark foreign invaders)
Hard palate: forms the bony roof of the mouth

Soft palate: forms the rest of the mouth
Uvula: prevents swallowed food from entering the nasal cavity

Tongue: helps to push food down towards the esophagus

Question 11

What happens during deglutition?

Answer 11

Deglutition (swallowing) has 2 major phases:
1. The buccal phase
2. The pharyngeal-esophageal phase

Question 12

What is the buccal phase?

Answer 12

After chewing (mastication) and being mixed with saliva, the food lump is called a bolus.
It is forced into the pharynx by the tongue.
This is a consciously-controlled process.

Question 13

What is the pharyngeal-esophageal phase

Answer 13

A thin flap of skin called the epiglottis blocks the larynx and the uvula blocks the nasal cavity.
This causes food to travel to your esophagus instead of into your respiratory system.
The bolus is propelled down the esophagus using waves of muscle contractions.
This process is called peristalsis.
Peristalsis is involuntary and caused by the parasympathetic nervous system rather than gravity.

Question 14

What is the anatomy of the stomach?

Answer 14

Stomach= muscular sac with thick walls
Continues the processes of mechanical and chemical digestion
4 main regions of stomach:
Cardiac region
Fundus
Body
Pyloric region
The digestive system has thick rings of muscle at certain points called sphincters. These serve as gatekeepers to allow food to enter and leave at appropriate times.
The stomach allows food to enter through the cardiac sphincter and leave through the pyloric sphincter.
Cardiac sphincter: separates esophagus from stomach
Pyloric sphincter: separates stomach from small intestine

Question 15

How does mechanical digestion occur in the stomach?

Answer 15

The stomach has a slippery outer layer of serosa, followed by 3 layers of muscle:
Longitudinal muscularis
Circular muscularis
Oblique muscularis
These muscles help to churn food and propel it towards the small intestine. The churning process is known as maceration.
The innermost layers of the stomach are made of the submucosa and mucosa.
The folds of the mucosa are called rugae (“wrinkles”) that stretch when the stomach is full.

Question 16

How does chemical digestion occur in the stomach?

Answer 16

The mucosa layer contains several specialized gastric gland cells:
1. Mucous cells- secrete mucus to protect stomach lining
2. Chief cells- secrete pepsinogen (inactive enzyme)
3. Parietal cells- secrete HCl to kill microbes in food and convert pepsinogen into the digestive enzyme pepsin, which breaks down food proteins.
The soupy mixture formed from the squeezing of the stomach and the addition of these gastric juices is known as chyme.

Question 17

What is the anatomy of the small intestine?

Answer 17

Small intestine is the location of most digestion and nutrient absorption

It is about 10 ft long in an adult.
The small intestine has 3 sections:
Duodenum
Jejunum
Ileum
After the ileum, it joins the large intestine at the ileocecal sphincter.

Question 18

What process occurs in the small intestine?

Answer 18

Many glands line the small intestine and secrete digestive hormones.
Alkaline mucus from mucous glands & duodenal glands- protects from pathogens
Secretin- inhibits the release of gastric juices when chyme is very acidic
Cholecystokinin (CCK)- causes gall bladder to release bile
Intestinal juice,
Maltase,
Sucrase,
Lactase, breaks down sugar
Peptidase,
Enterokinase, breaks down protein
Because the small intestine needs time to absorb nutrients, the chyme must be slowed down.
Circular muscles in the intestinal wall cause segmentation of the chyme.
This is in contrast to peristaltic contractions which involve longitudinal muscles.

Question 19

What is the anatomy of the large intestine?

Answer 19

After food leaves the small intestine, it enters the large intestine.

The large intestine has 3 major sections:
1. Cecum
2. Colon (broken into ascending colon, transverse colon, and descending colon)
3. Rectum

Question 20

What processes occur in the large intestine?

Answer 20

2 major functions of the large intestine:
Absorption of water back into the body
Removal of waste (feces) through the rectum and anus
Large amounts of bacteria (about 3 pounds worth!) are located in the large intestine that help to produce vitamins B and K.
Strong doses of antibiotics can disrupt these bacteria and cause vitamin deficiencies.

The haustra are the small pouches that give the large intestine its lumpy appearance.
Haustral contractions are slow, segmenting movements that last only about 30 minutes after food moves into the large intestine.
Mass movements, however, are slower and more powerful movements that push waste towards the rectum 3 or 4 times a day.

Question 21

What occurs in the rectum and anus?

Answer 21

The rectum collects and stores undigested waste and bacteria.

As the rectum fills, pressure is placed on the internal anal sphincter, causing it to relax.
The external anal sphincter, luckily, needs to be voluntarily relaxed to release the built up feces through the anus.