Chapter 13 Part 3

Question 1

Name the three venomous families of snakes

Answer 1

Colubridae
Elapidae
Viperidae

Question 2

Colubridae

Answer 2

• venomous snake family
  · Duvernoy’s gland of a colubrid snake (rear-fanged)
  · Arises from the embryonic tissue that also gives rise to the posterior pair of maxillary teeth
  · Fang at end of maxilla
  · Fang grooved
  · Duvernoy’s gland in this group produces toxic substances; arises from same tissues that produce posterior teeth

Question 3

Elapidae and Viperidae

Answer 3

• two groups of venomous snake family
  · Fang-bearing maxilla of front-fanged snakes represents the rear portion of the ancestral colubroid maxilla
  · Front fangs represent rear maxillary teeth that have been shifted forward by reduction of the anterior part of the maxilla
  · Fangs found on maxilla
  · Maxilla is shortened

Question 4

Describe the venom apparatus of elapidae and viperidae

Answer 4

oLarge hollow fangs (the only maxillary teeth)
o Venom gland muscles are not homologous
o Venom: proteolytic enzymes that break down capillaries and destroy local tissues
o Muscles: Group has short maxilla, only has one tooth; Fang can fold up into the roof of the mouth; When opening mouth, pulls on maxilla/muscles and rotates fang out

Question 5

Describe fang erection in viper

Answer 5

▪ Contraction of two palatal muscles (the protractor pterygoidei and levator pterygoidei) pulls the palatal bones forward, rotating the maxilla and prefrontal bones and erecting the fang.
▪ The retractor pterygoidei returns the fang to the resting position

Question 6

Specific structures only in Elapidae

Answer 6

· Hollow fangs with multiple maxillary teeth
· Relatively short fangs compared with the size of their heads, in vertical position
· Fangs remain in a vertical position
· Venom: short-chain polypeptides that interfere with neuromuscular transmission and immobilize prey; produce various kinds of neurotoxins

Question 7

Name an example of a specialized elapid

Answer 7

· Spitting cobra
· Defensive adaptation to spit venom!

Question 8

Venom gland of venom-conducting teeth of Gila monster

Answer 8

▪ Have venom glands derived from salivary glands in above groups(snakes and such)
▪ Large venom gland
▪ Tiny ducts open to teeth
▪ Teeth grooved
▪ The venom gland lies along the lateral surface of the mandible
▪ The grooves in the teeth (arrows) conduct venom into the wound

Question 9

Venom in vampire bats

Answer 9

▪ Draculin
▪ glycoprotein found in the saliva of vampire bats: functions as an anticoagulant
▪ when feeding, they make small wound to lap up blood

Question 10

What is the “outside-in” theory?

Answer 10

teeth arose phylogenetically from bony armor of primitive fishes, probably from surface denticles that rode inward as the invaginated stomodeum (ectoderm) moved inward to the buccal cavity with the newly developed jaws

Question 11

General structures seen often in teeth

Answer 11

• crown, root, enamel, dentin, cementum, pulp

Question 12

Crown

Answer 12

top area of tooth, includes enamel and dentin, often used in manipulation of food

Question 13

Root

Answer 13

unseen area of the tooth that sits within the gum

Includes pulp cavity dentin, cementum, root canal, and apical foramen

Question 14

Enamel

Answer 14

the most mineralized part of the body (97%); Main mineral component is crystalline calcium phosphate

Question 15

Dentin

Answer 15

not as hard and is essential for support of the enamel layer; Comprised of mineralized connective tissue and a collagenous matrix and forms a chamber filled with the dental pulp that includes stem cells, connective tissue, blood vessels and nerves; 75% mineral

Question 16

Cementum

Answer 16

comprised of hydroxyapatite and a collagenous matrix; Serves as a site of attachment for the periodontal ligaments, which provide tooth stability

Question 17

Pulp

Answer 17

living, vascular and well-innervated tissue

Question 18

What is the enamel organ?

Answer 18

• important in tooth development
  o Comes from epidermis
  o Releases cells into an area around dermal papilla to form cap/teeth; Dermal papilla comes from the dermis

Question 19

What is the function of ameloblasts and odontoblasts?

Answer 19

Ameloblasts: source of tooth enamel and form from the enamel organ

Odontoblasts: source of dentin and form from the dermal papilla

Question 20

Describe the development of a tooth

Answer 20

Bone appears and begins to delineate the socket in which the tooth will reside

Then primordium of permanent tooth appears

The deciduous tooth (baby tooth) erupts and is anchored in the socket by a well-established periodontal ligament. Temporary tooth

The enamel organ and dermal papilla of the permanent tooth primordium will not begin to form the tooth until shortly before the deciduous tooth is lost

Eventually tooth pokes out of oral cavity lining (note mammals have teeth anchored in bony socket)

Question 21

What is the function of the periodontal ligament?

Answer 21

• anchors teeth, absorbs shock, provides nutrients to teeth and surrounding tissue, have regenerative capacity