Digestive System

Chapter 15

Tongue Mostly muscle tissue

– What type of muscle would it be? Frenulum – connects the tongue to the

bottom of the mouth What is the purpose of the tongue? Papillae – rough projections that

contain taste buds– Why would these be rough?

Four types of taste buds – sweet, sour, salt, bitter

Palate 2 sections Hard Palate

– Also known as the maxilla– Anterior Portion

Soft Palate– Posterior Portion– This and the uvula are drawn up during

swallowing• Why is this important?

Blocks off the nasal passage during swallowing

Tonsils

Lingual – at the base of the tongue– Used as anchor, covered by lymphatic

tissue Palatine – Located on the side of the

tongue Which do you think is removed when

you have tonsillitis? Palatine – exposed to many pathogens

so they can easily become infected.

Teeth

2 sets Primary (baby) – 10 on each jaw

– What happens to these? They are lost

– The roots are resorbed and teeth are pushed out by secondary teeth

Secondary (permanent) – 16 on each jaw– Begin to appear around age six

Secondary Teeth Incisors – total of eight, front teeth

– Function? Tearing off bites Cuspids (Canine) – total of four,

sharper teeth (fangs)– Function?

Rip and Tear tough food.

Secondary Teeth

Bicuspids (premolar) – total of eight, behind cuspids, a bit flatter– Function?

Mash and grind, little bit of tearing Molars – total of 12, back teeth much

flatter (4 first, 4 Second, 4 Third)– Third also known as wisdom teeth– Function?

Mash and Grind Why do we need so many types of

teeth?

Tooth Structure Based on the name where do you think

each part is?– Crown –– Root –

Enamel – – Hardest substance in the body and cannot

be replaced– What problem does this pose?

Dentin – deep to the enamel and surrounds the pulp cavity (nutrient supply)

Salivary Glands

Main Secretions– Amylase – breaks down large starch

and glycogen molecules– Mucus –

• What is its purpose? Bind food particles and lubricate

alimentary canal What triggers secretions? Parasympathetic nervous system

Salivary Glands – 3 different glands

Paratid – Located anterior and inferior to the ear– Secretes saliva rich in amylase

Submandibular – Located where?– Secretes thicker saliva than paratid.

• Why thicker? Sublingual – Located where?

– Secretes primarily mucus

Pharynx

Connects nasal and oral cavities with the esophagus

Contains the epiglottis– What is this?

Flaplike structure used to seal off trachea during swallowing.

Has three sections- nasopharynx attaches nasal cavity- oropharynx attaches mouth- laryngopharynx attaches esophagus

Wall Structure

4 layers– Mucosa –

– Submucosa –

– Muscular layer -

– Serosa –

Esophagus

Connects pharynx to stomach– Function -

Ends at lower esophageal sphincter– What is a sphincter?– This one connects the stomach

and the esophagus, what will its function be?

Stomach

Location – Size is small when empty, yet it

can hold one liter. How? What happens in the stomach?

Stomach Regions of the stomach

• Cardiac - posterior to lower esophageal sphincter

– Function-

• Fundic – Most anterior portion– Function –

• Body – Main region– Function –

• Pyloric – most posterior region– Function –

Stomach ends at Pyloric Sphincter

Gastric Juice

4 Components Pepsin – Pepsinogen – Hydrochloric Acid –

• Mucus

Gastric Regulation

Produced regularly, but rate can vary What might cause it to vary?

Gastrin – What stimulates the release?

Gastric Mixing

How will the stomach perform its functions?

Chyme – Where does food go to exit stomach?

– How does the stomach move it there?

Pancreas

Located near posterior abdominal wall inferior to stomach

Secretes____ into the ___. Amylase Lipase Nuclease

What other important function?

Liver

Located… Lobed Multiple Functions

Blood –

Storage - Digestive functions

Metabolism of Carbohydrates, Lipids and Proteins Secretes ____ through the ___into the ____.

Bile

Consists of: 1.

Two types biliverdin and bilirubin

2. Only part of the bile that has digestive function Emulsification

3.

Storage area What does it store?

Reabsorbs water to concentrate __________.

Hormones stimulate sphincter to relax, open duct Causing what to happen?

Gallbladder

Questions If a person had a condition which limited their

ability to produce hydrochloric acid in the stomach, how might this affect digestion and why?

If someone lost control of their pyloric sphincter and was unable to contract it, how would this affect digestion?

Thinking about the contents of the stomach, what might happen to a person with a lower esophageal sphincter that does not contract completely?