Human Anatomy Unit 6 Quiz 2

Where does digestion begin?

Digestive system begins at the mouth or oral cavity.

What is the mouth made up of?

Mouth is formed by cheeks, & the hard & soft palates.

Name the 3 different pairs of salivary glands

• Parotid

• Submandibular

• Sublingual 

3 parts of the mouth

Saliva, Tongue, Teeth

Salivary glands are in ____

pairs

What is the function of saliva? What does it contain?

Function: to begin chemical digestion & to lubricate food
Contains: water, mucus, enzymes that destroy bacteria, & some that start chemical digestion

Salivary amylase

enzyme that begins starch breakdown in the mouth

Lingual lipase

It begins fat breakdown. Released in mouth, but not activated until it hits the acid in the stomach.

When is lingual lipase released? When is it activated?

Released in mouth, but not activated until it hits acid in stomach

Tongue — what is it? what is it made of?

Forms the floor of the oral cavity. Has receptors for taste; composed of muscle & mucous membrane.

What is the tongue considered? Why?

accessory digestive organ because it is needed for digestion, but food does not pass through it

Tongue structure

• composed of muscle & mucous membrane

• There are extrinsic muscles of tongue which originate outside of tongue, but connect to it.  They move tongue from side to side & in & out.

• Intrinsic muscles originate & insert w/in tongue.  They alter size & shape of tongue.

Extrinsic vs intrinsic muscles of the tongue

Extrinsic: move tongue (positioning and mobility of the tongue)

Intrinsic: alter size and shape of tongue (for tasks like speaking, swallowing, and manipulating food)

Teeth

Accessory digestive organs located in sockets in the gingiva which covers the mandible & maxilla.

What happens when food enters the mouth?

As food enters mouth, mechanical digestion results from chewing or mastication.

What happens after mastication?

• A soft, flexible mass results which is called a bolus.  It can be easily swallowed.

• It passes from the mouth into the pharynx.

Order what happens after food is ingested

1. Mechanical digestion (chewing/mastication)

2. Bolus forms (easily swallowable mass of food)

3. Mouth —> Pharynx

Pharynx structure

Pharynx is made of muscle & lined by a mucous membrane; divided into 3 parts

3 parts of pharynx

1. Nasopharynx

2. Oropharynx

3. Laryngopharynx

(in order from position top to bottom as well)

What propels food into the esophagus?

Contractions propel food into esophagus.

What are the two stages of swallowing?

voluntary and involuntary

Voluntary swallowing

tongue pushes food backward against palate

Involuntary swallowing

once food goes into oropharynx, medulla oblongata is stimulated.

• Soft palate & uvula move up to prevent food entering nasopharynx

• Epiglottis closes, so that food doesn’t enter trachea.

• Esophageal sphincter relaxes. Food enters esophagus.

Both prevent food from entering somewhere. Soft palate & uvula is to ____ as epiglottis is to _____.

Soft palate is to nasopharynx

Epiglottis closes, so that food doesn’t enter trachea.

Esophagus (what it is, positioning, etc)

Esophagus is a muscular tube.  Lies posterior to trachea.  Travels through the mediastinum, anterior to vertebral column.  Pierces diaphragm & ends at the superior portion of the stomach.

How does food move down the esophagus?

• A wave-like motion of myo contractions called peristalsis, forces food down esophagus.

• When lower esophageal sphincter relaxes, food enters stomach.

• Takes 4-8 seconds from mouth to stomach.

Functions of the stomach

• Mixing

• Storage

• Chemical digestion

• Secretes the hormone gastrin

4 regions of the stomach

1. Cardia

2. Fundus

3. Body

4. Pylorus

Stomach structure

• It also has many ridges called rugae.

• Pyloric sphincter open up to the duodenum.

• The stomach contains the 4 basic cell layers discussed before.

• It has specialized secretory cells called gastric glands which line narrow channels called gastric pits.

Mucous neck cell

secretes mucus (protects lining of stomach; prevents self-degradation)

Parietal Cell

secretes gastric acid (HCl); needed for digestion

Chief cells

secretes pepsin and has gastric lipase

G cells

produce gastrin (hormone that starts secretion of gastric juice)

What do the secretions form?

All of these secretions form gastric juice (we make 2-3 qt/day).

What does gastric juice do?

• Gastric juice continues the chemical break down.

• Proteins are broken into smaller polypeptide chains, triglycerides into fatty acids and monoglycerides, etc.

• Food + gastric juices = chyme.

Chyme

Food + gastric juices = chyme

Mechanical digestion

While chemical digestion is occurring, mechanical digestion continues.

• Stomach has rhythmic contractions.

• Small amounts of chyme are passed into duodenum at regular intervals.

• Stomach takes 2-4 hours to empty.

• Very little absorption here—only water, small ions, certain drugs & alcohol.

True or False: there is very little absorption in the stomach

true