Lecture 21: Digestive

Question 1

Lis the various functions of the vertebrate gut tract

Answer 1

Transportation: peristalsis, reverse peristalsis

Physical treatment: chewing, propulsive peristalsis, intermittent constrictive contractions.

Chemical treatment: digestive enzymes, digestive acids, bile

Absorption: movement from lumen into blood/lymph.

Question 2

Describe some of the factors that have influenced the evo. Of the vertebrate digest tract

Answer 2

Pleuroperitoneal cavity:

• fishes
• amphibians
• many tetrapods

Peritoneal cavity:

• some reptiles
• birds
• mammals

Differ based on compartmentalization

Question 3

List and characterize in order the layers of the typical gut tube

Answer 3

Midgut: part containing yolk or to which yolk sac is attached.

Foregut: part anterior to midgut. Forms pharynx, esophagus, stomach, much of small intestine

Hindgut: part posterior to midgut. Forms remainder of intestine and cloaca.

Question 4

Describe the evolution of the tongue in vertebrates and explain why the tongue in higher vertebrates is innervated by three cranial nerves.

Answer 4

Primary tongue: elevation of floor in oropharyngeal cavity-amphibians, fishes, amphibinas w/ persistent gills

Primary w/ extension: glands w/ sticky substance- terrestrial salamanders

Tongue of reptiles/mammals: hyoid arch derivative.

Bird tongue: almost entirely devoid of intrinsic musculature.
It is derived from 3 different pharyngeal arches

Question 5

List in order and describe the layers of the generalized gut tube

Answer 5

Outer to inner:

• Serosa:outer layer CT. Simple squamous epithelium. Thin lubricating fluid.
• Longitudinal smooth muscle layer
• myenteric plexus (of auerbach)-controls smooth muscle
• circular smooth muscle layer
• meissner’s plexus (submucosal plexus)-GI secretion, absorption, and blood flow.
• submucosa: thick CT-arterioles
• mucosa: endoderm. Single cell layer.

–Myenteric and meissner’s plexuses: enteric NS. Operates autonomously via intrinsic regulation and sensory reflexes. Works w/ sympathietic and parasympathetic.

Question 6

Compare the anatomy of the gut tract in various vertebrates and describe the variations in the ways that vertebrates have increased the surface area for absorption.

Answer 6

More folds enlargements throughout the evo lineage-more complexity

Esophagus: crop in grain eating birds. Similar to gizzard development (grinding mill)

Development of the stomach.

Shark: agar like spiral structure.

Absorptive surfaces: most small intestine. Plicae- fold of mucosa. Crypt-villus system-deep fosa btw villi to increase SA.

Question 7

Describe the types of teeth found in the various vertebrate groups and be familiar w/ the nomenclature describing types of teeth.

Answer 7

Plankton (filter feeders)
Insects 
Shellfish
Flesh
Piscivorous (carniverous)
Vegetation (herbivores)
Omnivorous 

Slide 38

Question 8

Describe the early mammalian molar and explain how. It has been “squared up” in modern herbivores

Answer 8

Pedicellate tooth: amphibians and reptiles ;
Thecodont tooth(enamel only): crocodillian and mammals;
Heterodonty in mammals:
incisor-cutting
canine- piercing
premolar and molars-mastication

Trigonoid/talonoid (triangular shaped) became squared up by:

• addiing an additional cusp (hypocone) to upper molar
• eliminating a conoid (paraconid) from lower molar.

Question 9

Be familiar w/ the concept of dental formulas in various kinds of mammals.

Answer 9

Everyone has incisors, molars

Human have 32 teeth

Question 10

Be familiar w/ the terminology given in this lecture r..t descriptions of teeth and dental patterns

Answer 10

Homodont: teeth are all the same
Heterodont: teeth come in different shapes
Polyhydont: permanent replacement of teeth
Diphyodont: 2 sets of teeth
Monophyodont: one set of teeth
Bunodont: all teeth on single plain

Humans: heterodont, diphyodont,and bunodont