t18 digestion wrksht.ppt - clark university · 1/10/2013 1 topic 18: the digestive system how does...
TRANSCRIPT
1/10/2013
1
Topic 18: The Digestive System
� How does the gut develop?
� What are the parts of the digestive system?
� Tooth types, differentiation and diversity
� What are the modes of feeding and how do they
work?
� What are the functions of the digestive system and
how are the functions distributed among parts?
� Gut differentiation and specialization
How does the gut develop?
� _______________
� ______________
� Intraembryonic
� Foregut
� Midgut
� Hindgut
� Extraembryonic
� Yolk sac & allantois
� Umbilical cord
� Stomodeum
� Proctodeum
Liem et al. Fig. 16-1
What are the parts of the digestive system?
© Mader 1997
� Lips (mammals)
� Teeth
� Oral cavity
� Pharynx (oro, naso, laryngo)
� Esophagus
� Stomach
� Small intestine
� Colon
� Rectum
� Anus
� Cloaca
� Also salivary glands, liver, gall bladder, pancreas
Fore
gut
Mid
-
gut
Hin
dgut
What are the components of the foregut?
© doctorcaruana.org
� ______________� Suckling
� Keeping food in mouth
� ________� Prey prehension
� Prey mastication
� __________________� Initial breakdown of food
� ______________� Food manipulation
� Swallowing
� ______________� Nasopharynx
� Oropharynx
� Laryngopharynx (hypopharynx)
� ______________� Amylase – carbohydrate digestion
� Mucous – lubrication
1/10/2013
2
Functions of the foregut
� Prey processing
� _____________
� _____________
� _____________
� Formation of bolus
� _____________
� Tongue
� Esophagus
� What kind of muscles are involved?
L. Frolich
Teeth
� Primarily ___________
� _____________
� Erupted, chewing portion
� Capped with enamel
� _____________
� Portion in socket
� Lined with cement
� Molars
� Low-crowned: omnivores
� High-crowned: herbivores
Liem et al. Fig. 16-3, 16-9
Teeth
Liem et al. Fig. 16-4; Photos © save-our-sharks.org, KP Bergmann; PJB
Who else has a thecodont dentition?Teeth
� Homodont
� Can be variable in size
� Heterodont
� _______________
� Diphyodont
� Molars not replaced
� _______________
Liem et al. Fig. 16-5; Photos © wikipedia, N Jaquet, M Thompson, GF Maxwell
1/10/2013
1
Heterodont Teeth
� Occlusion for proper function
� Differentiation
� ________
� ________
� Formula is # of teeth in upper & lower jaw
� Human: I2/2, C1/1, P2/2, M3/3
� What is the formula for this insectivore?
� I:
� C:
� P:
� M:
Liem et al. Fig. 16-7
� ___________
� ___________
Tooth Diversity
� Tooth morphology depends on diet
� Raptorial vs. durophagous sharks
� What are some specializations we saw in lab?
Photos: Wikipedia
1/10/2013
1
Feeding Modes
� How is prey ingested?
� Aquatic modes rely on movement of water
� ____________ feeding
� Cilia move water through pharyngeal slits
� ____________ feeding
� Sudden opening of mouth
� Water rushes in
� ____________ feeding
� Swimming with mouth open
� Forces water with prey in
� ____________ feeding
� Relies on grasping of prey
� Independent of water movement© C Arenz, N Kley
Feeding Modes
� Terrestrial
� Generally grasping of prey
� Specializations� _________________
� Inertial feeding
� _________________
� Tearing of prey
Herpetology Fig. 11-28; wikipedia; SM Deban; H Chittenden
What is a feeding cycle?
� Mouth ____________
� Epibranchial m.
� m. coracomandibularis
� m. coracohyoideus
� m. levator hyomandibulae
� Mouth ____________
� Adductor mandibulae
� m. levator palatoquadrati
� m. intermandibularis
� m. interhyoideus
Liem et al. Fig. 16-11
What are the phases of the tetrapod feeding cycle?
� Tetrapods have four phases:
� ______ opening
� Preparatory
� ______ opening
� Strike
� ______ closing
� Grasp
� ______ closing
� Powerstroke
� Prehension & mastication
� Muscles very similar
between slow & fast phases
Liem et al. Fig. 16-15
1/10/2013
1
Feeding Mechanics
� How the jaw works influences lever arms and size of muscles
� Temporalis & masseter are the major jaw-closing muscles in mammals
Liem et al. Fig. 16-16
What is main degree of freedom? How big are the in-levers? How big are the muscles?
1/10/2013
1
Midgut: Stomach
� Fundus
� Body
� Pylorus
� Control of food movement
� Cardiac/esophageal sphincter
� Pyloric sphincter
� Function?
� ____________________
� ____________________
� 3 layers of smooth muscle
� ____________________
� Hydrochloric acid
� Pepsinogen � Pepsin
� ____________________
© WebMD.com
Midgut: Small Intestine
� _____________: Straight
� Digestion
� Products of liver
� Products of pancreas
� ___________: Convoluted
� Digestion & absorption
� ___________: Convoluted
� Absorption & digestion
© Mayo Foundation
Midgut: Small Intestine
� Digestion
� Liver produces bile
� Stored in gall bladder
� _________________
� Pancreas produces
� ________ – Carbohydrates
� ________ – Proteins
� Intestine produces
� Lipase – Fats
� Enterokinase – activates trypisn
wikispaces.org
Midgut: Small Intestine
� _____________� Villi with microvilli
� High Surface area for absorption
� _____________
� Glands
� Secrete digestive enzymes
� _____________
� Smooth muscle
� Moves material along
Liem et al. Fig. 17-1
Hindgut: Colon
� Functions
� Absorption
� Waste storage
� Caecum (appendix)
� Ascending colon
� Transverse colon
� Descending colon
� Rectum vs. Anus
wikispaces.org
Hindgut: Cloaca
� Mammals
� Lack a __________
� Separate openings for excretory,
digestive, and reproductivesystems
� Other tetrapods
� Everything opens into cloaca
� Turtle
Liem et al. Fig. 17-8
1/10/2013
1
Gut Evolution
� Esophagus
� Stomach
� Small Intestine
� Colon
� Cloaca/Anus
Liem et al. Fig. 17-2, 17-3, 17-4
LampreyShark
FrogTurtle
Cat
How have gut
proportions
evolved and why?
Gut Evolution in Response to Diet
� Which parts are longer in the koala?
� Which parts are longer in the coyote?
� Why?
Campbell, Fig. 37-17
1/10/2013
1
Gut Evolution in Response to Diet
� Tadpole vs. Adult frog
� How does the diet differ?
Source ??
Gut Evolution and Herbivory
� _____________________
� Subdivision of the stomach
� Rumen
� Reticulum
� Omasum
� Abomasum
� Typical stomach
� Pylorus
� Stomach may contain 300L of material!
� Bacteria and protistsproduce cellulase
Liem et al. Fig. 17-6
Gut Evolution and Herbivory
� Rumen
� Fermentation
� Regurgitation
� Rumination
� Swallowing
� Reticulum
� Absorption of starch
� Omasum, abomasum
� Protein digestion
� More absorption
Liem et al. Fig. 17-6
� ______________________� Elaboration of colon or caecum
� No repeated mastication
� 70% as efficient as foregut fermentation
� Horses, camels, antelopes
Gut Evolution and Herbivory
Liem et al. Fig. 17-7
Rhea Zebra Capibara