1. Chapter 23 Anatomy of the Digestive System – Part 1

2. Overview
Organs:
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine

3. Overview Accessory Organs
Teeth, tongue, gallbladder,, salivary glands, liver, pancreas
Contribute to the breakdown of food

4. Imagine yourself taking a bite of food….

5. The Mouth AKA: oral cavity or buccal cavity Opening  oral orifice
Boundaries:
Lips anteriorly
Cheeks laterally
Palate superiorly
Tongue inferiorly
Continuous with oropharynx posteriorly

6. The Lips (Labia) and Cheeks
Lips – orbicularis oris
Very large! Extend from bottom of nose to bottom of chin
Red margin – lipstick or kisses
Cheeks – buccinators
Both help to keep food between the teeth when we chew
Also play a role in speech
Labial frenulum – median fold that joins the internal aspect of lips to the gum

7. The Palate Roof of the mouth Hard palate Soft palate
Palatine and maxillae bones
Rigid surface against which the tongue forces food during chewing
Soft palate
Posterior – arch shaped
Mobile fold formed mostly of skeletal muscle

8. Palate
Soft Palate
Uvula – projects down from the free edge of the soft palate
During swallowing both are drawn upwards closing off the nasopharynx and preventing foods/liquids from entering the nasal cavity
Try and breathe and swallow at the same time

9. Teeth Teeth break and rip apart food Increases surface area
Smaller pieces increases the surface area  enzymes in the saliva can get at the food easier  chemical breakdown of food takes place quicker

10. Teeth 2 sets of teeth Primary  baby teeth (20) Permanent  adult (32)
First teeth appear ~6 mo
Fall out b/t 6-12 years
Permanent  adult (32)
Absorb roots of baby teeth causing them to fall out
Usually all have erupted (except 3rd molars) by end of adolescence
Wisdom teeth (3rd molars)  erupt b/t years

11. Teeth - Types Incisors Canines (cuspids/eyeteeth)
Chisel-shaped
Cutting or nipping off pieces of food
Canines (cuspids/eyeteeth)
Conical or fanglike
Tear and pierce
Premolars (bicuspids)
Broad crowns and rounded cusps
Grinding or crushing
Molars

12. Teeth - Regions Crown Root Exposed part of the tooth
Covered in enamel  a cellular, brittle material that bears the force of chewing. Hardest substance in the body. Can’t repair itself!
Root
Portion embedded in the jaw

13. Teeth - Cavities
Result from a gradual demineralization of enamel and underlying dentin by bacteria
Dental plaque (film of sugar, bacteria, etc.) adheres to teeth  bacteria dissolve trapped sugars  those produce acids, which dissolve the enamel.

14. Salivary Glands
We see food or think of food  Mouth starts to water  saliva is released from the salivary glands

15. Salivary Glands Secrete saliva
Cleanses mouth
Dissolves food chemicals for tasting
Moistens food and aids in bolus formation
Contains enzymes that begin chemical breakdown of starchy foods
Three glands  parotid, submandibular, sublingual
Lie outside oral cavity and empty saliva into it

16. Composition of Saliva Water  97 – 99.5% Slightly acidic  pH 6.75-7.0
Digestive enzyme  salivary amylase
Proteins 
Mucin – dissolved in water forms a thick mucus that lubricates the oral cavity
Lysozyme – inhibits bacterial growth in the mouth
IgA – antibodies, protection against microorganisms
Metabolic wastes  urea and uric acid

17. Tongue
Occupies most of the floor of the mouth and fills most of the oral cavity when mouth is closed
Composed of interlacing bundles of skeletal muscle fibers  during chewing grips and repositions food between the teeth

18. Tongue Mixes food with saliva  forms bolus (“lump”)
Initiates swallowing  pushes bolus posteriorly
Helps to form consonants when we speak
Helps to keep food between the teeth by pushing the food against the hard palate

19. Tongue
Lingual frenulum – secures tongue to floor of mouth, limits posterior movements
Ankyloglossia (“fused tongue”) aka tongue-tied  when lingual frenulum is too short  limits movements of tongue so speech is distorted.

20. Tongue Filiform papillae Smallest and most numerous
Roughness that aids in licking foods and provides friction for manipulating foods in mouth
Aligned in parallel rows
Whitish appearance

21. Tongue Fungiform papillae Circumvallate (vallate) papillae
Mushroom-shaped
Scattered widely over the tongue surface
Have a reddish hue
House taste buds
Circumvallate (vallate) papillae
10-12, large, located in a V-shaped row at that back of the tongue

22. Tongue Foliate papillae Sulcus terminalis
Pleatlike, located on the lateral aspects of the posterior tongue
House taste buds (only in infancy and early childhood)
Sulcus terminalis
Posterior to circumvallate papillae
Groove that distinguishes anterior and posterior tongue

23. Taste
For a chemical to be tasted it must dissolve in saliva, diffuse into the taste pore, and contact the gustatory hair. This causes a reaction from the nervous system that allows us to “taste” our food

24. Taste Taste buds – sensory receptors for taste
Located mostly in the oral cavity ~10,000
Most are on tongue. Few on soft palate, inner surface of cheeks, pharynx, and epiglottis
Most are found in papillae
Tops of fungiform papillae, sides of foliate papillae and circumvallate papillae

25. Taste
Taste qualities: sweet, sour, salty, bitter, and umami (“delicious”)
Most taste buds respond to 2 or more taste qualities and many substances produce a mixture of the basic taste sensations

26. Taste
Taste maps, although common, are inaccurate (sweet tip, salty and sour  sides, bitter  back, umami  pharynx
In reality, there are only slight differences in the localization of specific taste receptors in different regions of the tongue, all types of taste can be elicited from all areas that contain taste buds

27. Taste Taste likes and dislikes have a homeostatic value
Umami guides intakes of proteins
A liking for sugar and salt helps satisfy the body’s need for carbohydrates and minerals.
Many sour, naturally acidic foods (lemons, tomatoes, oranges) are rich sources of vitamin C.
Many natural poisons and spoiled foods are bitter, our dislike for bitterness is protective.

28. Taste
Taste is 80% smell. When olfactory receptors are blocked, food is bland.
Mouth also contains thermoreceptors (temperature), mechanoreceptors (touch), and nociceptors (pain). The temperature and texture of foods can enhance or detract from their taste. Spicy or “hot” foods bring about their effects by activating the pain receptors in our mouth