Unit 17: Digestive System

Welsh: 17, Saladin: ?

What are the 2 types of digestion?

• Mechanical: breaks large food → small, NO change in chemical composition

• Chemical: enzymes break food by changing them into simpler chemicals

What do the organs of the digestive system do? (5)

• Chemical/mechanical digestion

• Ingestion

• Propulsion

• Absorption

• Defecation

What does the digestive system consist of? (2)

• Alimentary canal

• Accessory organs

Alimentary canal:

• Description

• Organs

• Food passageway

• Organs that extend from mouth → anus: mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal

What are the accessory organs of the digestive system? (4)

• Salivary glands

• Liver

• Gallbladder

• Pancreas

What are the 4 layers of the alimentary canal?

• Mucosa: inner, mucous membrane

• Submucosa: CT

• Muscularis (externa): muscle tissue

• Serosa: outer w/ serous fluid

What is the mucosa layer of the alimentary canal? (5)

• Inner layer

• Mucous membrane

• Surrounds lumen (passageway)

• Folded in some areas to increase surface area

• Absorbs dietary nutrients, secretes mucus and enzymes

What is the submucosa layer of the alimentary canal? (4)

• Second innermost layer

• CT layer

• Contains blood and lymphatic vessels, nerves, and glands

• Nourishes cells and tps absorbed food molecules

What is the muscularis (externa) layer of the alimentary canal? (3)

• Second outermost layer

• Composed of muscle tissue w/ circular and longitudinal layers

• Moves tube and food materials

What is the serosa layer of the alimentary canal? (3)

• Outermost layer

• Contains serous fluid to eliminate friction

• Serves as visceral peritoneum of abdominal cavity organs

What are the 2 movement types of the alimentary canal?

• Mixing: muscle in small sections contract rhythmically, NOT in one direction

• Propelling: peristalsis; moves in one direction

What is peristalsis?

Contraction that propels food particles down in a wavelike motion

What innervates the alimentary canal?

Branches of the para/sympathetic divisions of the ANS

What 4 branches innervate the alimentary canal?

• Intrinsic:

  • Submucosal plexus: controls secretions

  • Myenteric plexus: controls GI motility

• Extrinsic:

  • Parasympathetic impulses: increase activities of digestive system (secretions and motility)

  • Sympathetic impulses: inhibit digestive actions (secretions and motility)

What are enterendocrine cells? Where are they found?

• Secrete chemical messengers to regulate GI organs/processes

• Stomach and SI

Which organ is the first part of the alimentary canal?

Mouth

What is mastication?

Mechanical breakdown of solid particles, mixing them with saliva

Cheeks

• Location

• Composition

• Lateral walls of mouth

• Inner lining of STSE

What are the lips a boundary between?

Skin and the mucous membrane inside the mouth

What is the lingual frenulum?

Connects tongue to floor or mouth

What are papillae (tongue)?

Projections that move food; contain taste buds

What are lingual tonsils?

Lymphatic tissue masses on root of tongue

What does the hard palate consist of?

Palatine processes of maxillae and palatine bones

What does the soft palate consist of?

Muscular arch that ends in the uvula

What are palatine tonsils?

Lymphatic masses on sides of tongue

What are pharyngeal tonsils (adenoids)?

Masses of lymphatic tissue in posterior wall of pharynx

What are the primary teeth called? How many are there?

Deciduous/baby teeth, 20

What are secondary teeth called? How many are there?

Permanent/adult teeth, 32

What are the 7 types of teeth?

• Central incisors

• Lateral incisors

• Canines (cuspids)

• First premolars (bicuspids)

• First molars

• Second molars

• Third molars

What are the different types of teeth used for?

• Incisors: biting

• Canines: grasping and tearing

• Pre/molars: grinding

What components do teeth consist of? (5)

• Crown and root: meet at neck

• Enamel: covers crown

• Dentin: makes up most of tooth; surrounds pulp cavity

• Periodontal ligament: holds root in place

• Cementum: anchors to jawbone

1

Incisors

2

Canine (cuspid)

3

Premolars (bicuspids)

4

Molars

5

Molars

6

Premolars (bicuspids)

7

Canine (cuspid)

8

Incisors

Type: Incisor (central)

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 4

2. 4

3. 6-8

Type: Incisor (lateral)

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 4

2. 4

3. 7-9

Type: Canine (cuspid)

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 4

2. 4

3. 9-12

Type: premolar (bicuspid (first))

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 0

2. 4

3. 10-12

Type: premolar (bicuspid (second))

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 0

2. 4

3. 10-12

Type: molar (first)

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 4

2. 4

3. 6-7

Type: molar (second)

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 4

2. 4

3. 11-3

Type: molar (third (wisdom tooth))

1. No. primary teeth:

2. No. secondary teeth:

3. Age of permanent tooth eruption:

1. 0

2. 4

3. 17-25

1

Enamel

2

Dentin

3

Pulp (in pulp cavity)

4

Root

5

Crown

6

Gingiva

7

Alveolar process

8

Periodontal ligament

9

Root canal

10

Cementum

What are dental caries?

• Cavities within enamel

• Formed when sticky foods lodge between teeth

• Bacteria on teeth metabolize sugars; prod acidic byproducts that destroy enamel and dentin

What does fluoride do to enamel?

Strengthen it

Why are sealants used in crevices?

Prevent acids from remaining in crevices and destroying enamel

Part: cheeks

1. Location

2. Function

1. Form lateral walls of mouth

2. Hold food in mouth; muscles chew food

Part: lips

1. Location

2. Function

1. Surround mouth opening

2. Contain sensory receptors that judge food characteristics

Part: tongue

1. Location

2. Function

1. Floor of mouth

2. Mixes food w/ saliva; move food → pharynx; contains taste receptors

Part: palate

1. Location

2. Function

1. Forms roof of mouth

2. Holds food in mouth; directs food → pharynx

Part: teeth

1. Location

2. Function

1. In sockets of mandible and maxillae

2. Break food particles into smaller pieces; mix food w/ saliva during chewing

What secretes saliva?

Salivary glands

What does saliva contain & what is their function?

• Enzymes: begin chem digestion of carbs

• Bicarbonate ions: keep pH favorable for enzyme activity; prot teeth from acidic foods

What are the 3 major salivary glands?

• Parotid glands: largest; secrete serous saliva w/ amylase

• Submandibular glands: floor of mouth; serous + mucous

• Sublingual glands: under tongue; mainly mucous

What are the 2 different secretory cells?

• Serous cells: prod watery fluid containing a digestive enzyme, salivary amylase

• Mucous cells: secrete mucus

What does amylase do?

Splits starch and glycogen into disaccharides

What does mucus do?

Binds food particles and lubricates food while swallowing

Gland: parotid glands

1. Location

2. Duct

3. Secretion

1. Between skin of cheeks by the ears

2. Pass through buccinator muscles and enter mouth opposite the upper second molars

3. Clear, watery serous fluid, rich in salivary amylase

Gland: submandibular glands

1. Location

2. Duct

3. Secretion

1. In floor of mouth on inside surface of mandible

2. Ducts open inferior to the tongue near the frenulum

3. Some serous fluid w/ some mucus; more viscous than parotid secretion

Gland: sublingual gland

1. Location

2. Duct

3. Secretion

1. In floor of mouth inferior to tongue

2. Many separate duct

3. Primarily thick, stringy mucus

1

Parotid duct

2

Parotid gland

3

Masseter muscle

4

Submandibular gland

5

Mandible

6

Sublingual gland

7

Submandibular duct

What role do the pharynx and esophagus play in food digestion?

They do not participate

1 (muscles of pharyngeal wall)

Mandible

2 (muscles of pharyngeal wall)

Superior constrictor muscles

3 (muscles of pharyngeal wall)

Middle constrictor muscles

4 (muscles of pharyngeal wall)

Inferior constrictor muscles

5 (muscles of pharyngeal wall)

Posterior surface of tongue

6 (muscles of pharyngeal wall)

Epiglottis

7 (muscles of pharyngeal wall)

Larynx

8 (muscles of pharyngeal wall)

Circular esophageal muscle

What are the 3 steps of swallowing divided into?

1. Voluntary stage; saliva mixed w/ chewed food forming bolus

2. Starts when food reaches oropharynx, stim sensory receptors, and triggers swallowing reflex

3. Peristalsis tp food in the esophagus to the stomach

What occurs during the second stage of swallowing? (6)

1. Soft palate and uvula rises to prot nasal cavity from food

2. Hyoid bone and larynx elevate

3. Epiglottis closes off top of larynx to prot trachea

4. Longitudinal muscles of pharynx contract

5. Inferior constrictor muscles relax and esophagus opens

6. Peristaltic waves force food into esophagus

What is the length of the esophagus?

25cm

What is the esophageal hiatus?

Where the esophagus penetrates the diaphragm

What gland(s) do/does the esophagus have?

Mucous glands in submucosa; moisten and lubricate lining of inner wall w/ mucus

What type of muscle is the muscularis composed of?

• Superior: 1/3 skeletal

• Middle: 1/3 skeletal + smooth

• Inferior: 1/3 smooth

What does the lower esophageal (cardiac) sphincter do?

Regulates food passage into stomach & prevent regurgitation

1

Esophagus

2

Diaphragm

3

Esophageal hiatus