Chapter 13: Digestive System

Question 0

Tooth Anatomy

Answer 0

Crown
Root
Enamel
Dentine
Pulp cavity
Cement

Question 1

Teeth

Answer 1

Evolved from dermal scales
About 400 mya
Embryology: interaction of epidermis and dermis

Question 2

Tooth attachment

Answer 2

1. Collagen fibers to jaw (sharks)
2. Pleurodont = medial margin of jawbone (on side, amphibs)
3. Acrodont = summit of jawbone (reptiles)
4. Thecodont = teeth embedded in jawbone -> more stable (mammals)
   Thecodont means “deep socket tooth”

Question 3

Diphydont

Answer 3

2 sets of teeth

Mammals (baby/milk/deciduous then adult/permanent teeth)

Question 4

Polyphydont

Answer 4

Many sets of teeth

Sharks, some bony fish

Question 5

Homodont

Answer 5

Same shape

Not as good for chewing

Question 6

Heterodont

Answer 6

More than a single tooth shape

Ex: incisors, canines, molars for specialized hunting and feeding

Question 7

Edentate

Answer 7

Do not have teeth

Ant-eaters, birds, turtles

Question 8

Mammal teeth terms

Answer 8

Incisors= grab, cut
Canines= tear
Premolars/molars (cheek teeth) = chew on occlusal surface
Prisms (type 1 of occlusal surface)= ridges
Cusps (type 2)= bumps, grooves
Carnassials (type 3)= sheer past one another for cutting
Diastema= gap (rodents, rabbits, deer, horses)

Question 9

Agnathan teeth

Answer 9

No teeth (bumps that are tooth-like)
Ancestral: filter-feeder
Small mouth, no jaw
Larger pharynx

Question 10

Placoderm teeth

Answer 10

No teeth

Shearing plates - large

Question 11

Chondrichthyes teeth

Answer 11

Numerous teeth, homodont
Non-movable tongue -cartilaginous
Fibrous attachment with collagen -loose
Constantly growing new teeth (and losing them ->fossilize)

Question 12

Osteichthyes teeth

Answer 12

Up to 10,000 teeth 
Jaw, roof of mouth, tongue, gills, pharynx
Homodont
Acrodont
Non-movable tongue
Large oral cavity

Question 13

Amphibian teeth

Answer 13

Few, small, homodont
Pleurodont attachment
Movable tongue*
Old: Labyrinthodonts (bc of shape)

Question 14

Reptilian teeth

Answer 14

Mostly homodont
Thecodont attachment
Some synapsids heterodont
Turtles edentate

Question 15

Ave teeth

Answer 15

Edentate, mostly immobile tongue

Some primitive ones had teeth

Question 16

Mammalian teeth

Answer 16

Diverse
Heterodont
Homodont

Question 17

Oral glands in Tetrapods

Answer 17

Food lubrication (no longer feed in water)
Modifications:
1) poison; lizards, snakes, shrews
2) anticoagulant; vampire bat
3) salt excretion; “nasal glands” marine + desert birds and reptiles
*exocrine glands

Question 18

Alimentary canal: functions

Answer 18

Receive food
Store food
Reduce food physically and chemically (break down of food)
Absorb nutrients
Eliminate digestive waste *not excretion

Question 19

Storage areas

Answer 19

Stomach
Crop (birds) -> intended
-> first chamber

Question 20

Physical reduction

Answer 20

1) chewing or grinding
- teeth
- stomach with gravel = alligators, birds
2) moistening
- mouth, stomach, intestine
3) churning and mixing
- stomach
4) emulsification of fats
- liver produces bile

Question 21

Chemical reduction

Answer 21

• stomach and small intestine *

- enzymes (lining and pancreas)

Question 22

Fish stomachs

Answer 22

Stomach “N” or “J” shaped

Question 23

Amphibian stomach

Answer 23

Simple stomach

Question 24

Reptiles stomach

Answer 24

Simple stomach

Crocs, very muscular

Question 25

Birds stomach

Answer 25

Crop-> storage
Stomach
1. Proventriculus 
    -Contains enzymes
2. Ventriculus or gizzard
    -grinding, gravel

Question 26

Mammals stomach

Answer 26

1. Sac-like
   - humans, most carnivores, rodents
2. Complex, multi-chambered
   - herbivores
   - ruminants -> rumen= fermentation, symbionts, anaerobic
   - many marsupials

Question 27

Rumen

Answer 27

Ex: cows
Full up stomach as fast as they can with grass > let it sit > regurgitate > chew + swallow again until they need more. (Process it over a long period of time)
Called remasticate

Question 28

Intestines

Answer 28

1. Enzymes for breakdown
   - lining
   - pancreas
2. Surface area for absorption
   - long
   - folded
   - villi (entire lining)
   - microvilli (finger-like projections on each cell

Question 29

Fish intestines

Answer 29

Just “intestine”

Question 30

Tetrapods intestines

Answer 30

“Small” and “large”
Vitamin B synthesis in large
Cecum = blind sac between small and large
Large: in herbivores, symbionts
Small: duodenum -> jejunum -> ileum
*loops of intestine held in by mesentary to prevent everything getting tangled up

Question 31

Agnatha intestines

Answer 31

• eat blood and suck fluids -> no need for complexity

- straight intestine, gentle spiral

Question 32

Cartilage fish intestine

Answer 32

Spiral valve = surface area

Question 33

Bony fish intestine

Answer 33

Long, coiled

Question 34

Amphibians intestine

Answer 34

Tadpoles; long, coiled (eat algae, takes awhile to digest - herbivores)
-adults; shorter (eat more meat, carnivores)

Question 35

Reptiles intestines

Answer 35

Snakes; straight

Others; some coiling

Question 36

Birds intestines

Answer 36

Long
2 ceca
Bursa of Fabricius -> out pocketing near end
   -in young birds
   -antibody formation 
   *homologous to appendix

Question 37

Mammals intestines

Answer 37

Small intestine:
-duodenum >enzymes
-jejunum
-ileum >most distal, absorption
Cecum:
-large in hindgut fermenters (herbivores: horse, rabbit)
Con or large intestine:

Question 38

Liver

Answer 38

Large, vascular
Hepatic ducts -> drain bile from liver
Cystic duct to gall bladder -> for storage then sent to….
Common bile duct (nuclei around ring)

Question 39

Some liver functions

Answer 39

Produce bile for emulsifying fat and neutralizing acid
Vitamin manufacture
Detoxification
Yolk production
Storage for carbs and fat
Deamination of protein, interconversions (carbs -> lipids or proteins -> carbs)

Question 40

Gall bladder

Answer 40

Stores bile
Small sac
Important in episodic feeders (eat in episodes: 1 big meal and then nothing for a while)
Absent in some herbivores (deer, horses)

Question 41

Pancreas

Answer 41

Gland near duodenum and stomach 
-exocrine (97%)
   •ducts (empty into duodenum - converge with common bile duct)
   •secrete digestive enzymes 
-endocrine
   •hormones for sugar metabolism
    >insulin - decrease blood glucose 
    >glucagon - increase blood glucose

Question 42

Lining of body cavities

Answer 42

Colonic cavity
Lining from hypomere of mesoderm
Outside wall = parietal peritoneum/serosa
Inner layer on organs = visceral peritoneum
Dorsal mesentery
Omentum (fat storage) -sheet of mesentary that connects organ to organ
Ventral mesentery

all of these prevent torsion and hold in place but still allow movement

Question 43

Mesenteries

Answer 43

Keep organs in place -> prevent torsion
Ventral mesentery often degenerates
Ex: falciform ligament

Question 44

Coelomic divisions

Answer 44

Pericardial cavity = heart
Peritoneal cavity = abdominal organs
Pleuroperitoneal cavity = lungs + abdominal organs (shark, fish, amphibians)
Pleural cavities = lung

Question 45

Hagfish coelom

Answer 45

Partial separation of pericardial and abdominal cavities

Question 46

Lamprey, fish, amphibians Coelom

Answer 46

Full separation of pericardial and peritoneal cavities

Question 47

Reptiles and birds Coelom

Answer 47

Pericardial, 2 pleural (thoracic)

Peritoneal

Question 48

Mammals Coelom

Answer 48

Pericardial, 2 pleural, fully muscular diaphragm

Peritoneal