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Questions and Answers
The ventral mesentery is absent in adult ______ except in the regions of the liver and the gall bladder.
The ventral mesentery is absent in adult ______ except in the regions of the liver and the gall bladder.
vertebrates
In mammals, the ______ of the stomach develops a special prolongation called the greater omentum.
In mammals, the ______ of the stomach develops a special prolongation called the greater omentum.
mesentery
Accessory organs include the ______, teeth, oral glands, pancreas, liver, and gall bladder.
Accessory organs include the ______, teeth, oral glands, pancreas, liver, and gall bladder.
tongue
Filter-feeding is the oldest ______ method of acquiring food.
Filter-feeding is the oldest ______ method of acquiring food.
The oral cavity begins at the ______ and ends at the pharynx.
The oral cavity begins at the ______ and ends at the pharynx.
The primary palate is the roof of the oral cavity of ______ and amphibians.
The primary palate is the roof of the oral cavity of ______ and amphibians.
Nasal passageways open into the ______ cavity in lobe-finned fishes.
Nasal passageways open into the ______ cavity in lobe-finned fishes.
The mouth is specialized to serve as a ______ and masticatory organ in mammals.
The mouth is specialized to serve as a ______ and masticatory organ in mammals.
The ______ is a distensible muscular tube connecting the pharynx and the stomach.
The ______ is a distensible muscular tube connecting the pharynx and the stomach.
In birds, the stomach is divided into the ______ and the ventriculus.
In birds, the stomach is divided into the ______ and the ventriculus.
The ______ are openings of auditory tubes in the pharynx.
The ______ are openings of auditory tubes in the pharynx.
The stomach of a ruminant serves mainly as a storage sac for large quantities of ______ matter.
The stomach of a ruminant serves mainly as a storage sac for large quantities of ______ matter.
The wall of the gut is composed of ______ layers caudad to the pharynx.
The wall of the gut is composed of ______ layers caudad to the pharynx.
In the absence of cellulase, little digestion takes place in the ______ intestine.
In the absence of cellulase, little digestion takes place in the ______ intestine.
The caecum houses a huge population of ______ that produce enzymes that convert cellulose to sugars.
The caecum houses a huge population of ______ that produce enzymes that convert cellulose to sugars.
In birds, the gizzard stones are lodged in the ______ stomach.
In birds, the gizzard stones are lodged in the ______ stomach.
The pharyngeal pouches may give rise to ______ in fishes.
The pharyngeal pouches may give rise to ______ in fishes.
Micromolecules are absorbed directly through the ______ of the caecum.
Micromolecules are absorbed directly through the ______ of the caecum.
The stomach is a muscular chamber that serves as a ______ and macerating site for ingested solids.
The stomach is a muscular chamber that serves as a ______ and macerating site for ingested solids.
The waste material is released into the ______ for disposal.
The waste material is released into the ______ for disposal.
Herbivores have modified the lower part of the esophagus and the ______ into 'four stomachs'.
Herbivores have modified the lower part of the esophagus and the ______ into 'four stomachs'.
The ______ is a muscular chamber that churns and grinds food against the stones in birds.
The ______ is a muscular chamber that churns and grinds food against the stones in birds.
The first compartment of a ruminant's stomach is the ______.
The first compartment of a ruminant's stomach is the ______.
Herbivorous birds have a ______ that is highly acidic.
Herbivorous birds have a ______ that is highly acidic.
The rumen is a ______ and fermentation vat.
The rumen is a ______ and fermentation vat.
The omasum is lined by ______ folds.
The omasum is lined by ______ folds.
The abomasum is a true ______ stomach.
The abomasum is a true ______ stomach.
Microbes provide ______ of cellulose to the ruminants.
Microbes provide ______ of cellulose to the ruminants.
Ruminants provide ______ with reliable heat to the microbes.
Ruminants provide ______ with reliable heat to the microbes.
Vertebrate intestines are differentiated into ______ and large intestines.
Vertebrate intestines are differentiated into ______ and large intestines.
Cartilaginous fishes have a ______ intestine with a spiral valve.
Cartilaginous fishes have a ______ intestine with a spiral valve.
Sharks are essentially ______ with their environment.
Sharks are essentially ______ with their environment.
In ______, the tract includes an expanded colon, cecum, or forestomach.
In ______, the tract includes an expanded colon, cecum, or forestomach.
In many ______, the hindgut includes a cecum, but neither the cecum nor colon are haustrated in most species.
In many ______, the hindgut includes a cecum, but neither the cecum nor colon are haustrated in most species.
The hindgut of ______ lacks a valvular separation from the midgut in some of these species.
The hindgut of ______ lacks a valvular separation from the midgut in some of these species.
The human ______ becomes well-developed during gestation.
The human ______ becomes well-developed during gestation.
The ______ is the principal site for microbial fermentation.
The ______ is the principal site for microbial fermentation.
The stomach is simple and ______ in OMNIVORES.
The stomach is simple and ______ in OMNIVORES.
Study Notes
Mesentery and Divisions of the Vertebrate Alimentary Canal
- Ventral mesentery is absent in adult vertebrates, except in the regions of the liver and gall bladder (falciform ligament)
- Special mesenteries for gonads and their ducts
- In mammals, the mesentery of the stomach develops a special prolongation called the greater omentum
- Accessory organs include the tongue, teeth, oral glands, pancreas, liver, and gall bladder
Anatomy of Vertebrate Digestive Tracts
- Differences in anatomy correlated with the nature and abundance of food
- Readily absorbed (e.g., hummingbirds) vs. requiring extensive enzymatic activity (e.g., carnivores)
- Constant food supply (e.g., herbivores) vs. scattered supply (e.g., carnivores)
- Filter-feeding is the oldest craniate method of acquiring food
- Still employed by lampreys, a few jawed fishes, and baleen whales
Oro-Pharyngeal Cavity
- Oral cavity begins at the mouth and ends at the pharynx
- Fishes have a very short oral cavity, while tetrapods typically have longer oral cavities
- Primary palate - roof of the oral cavity of fishes and amphibians; secondary palate in reptiles and mammals
Nasal Passageways and Oral Glands
- Nasal passageways open into the oropharyngeal cavity in lobe-finned fishes, and into the oral cavity in tetrapods with primary palate
- Multicellular oral glands open onto the roof, walls, and floor of the cavity
- May contain venom, saliva, including several enzymes, anticoagulant (lampreys, bats), nutrients in catfish, and mucus
- Oral glands are scarce in fishes
Mammals
- Mouth specialized to serve as a suckling and masticatory organ (with muscular cheeks)
- Oral vestibule separates the gums or alveolar ridges from the cheek and mouth
Pharynx
- Pharyngeal pouches may give rise to gill slits
- Fishes - gills and gill slits
- Tetrapods - includes glottis (slit leading into the larynx), openings of auditory (Eustachian) tubes, opening into esophagus, and location of tonsils in mammals
Esophagus
- Distensible muscular tube connecting the pharynx and the stomach
- Fishes - closes so the stomach doesn't become filled with respiratory water
- Birds - may have a diverticulum called the crop, which has digestive enzymes and allows hoarding of food
- Pigeon milk is an esophageal secretion in doves for nestlings
Stomach
- Muscular chamber(s) at the end of the esophagus that serves as storage and macerating site for ingested solids and secretes digestive enzymes
- Vertebrate stomachs:
- Cyclostomes - weakly developed; similar to esophagus
- Fish, amphibians, and reptiles - increasing specialization (more differentiated from the esophagus)
Birds
- Store large quantities of food temporarily in the crop, releasing it for digestion as needed
- Stomach is divided into:
- Proventriculus (glandular stomach)
- Ventriculus (muscular stomach, or gizzard)
- Lacking teeth, they swallow small stones which lodge in the muscular gizzard
- As the gizzard churns, the stones grind against the food like numerous tiny millstones
- Birds must constantly replace their gizzard stones by swallowing new gravel
Ruminant Stomach
- Serves mainly as a storage sac for large quantities of vegetable matter
- In the absence of cellulase, little digestion takes place in the small intestine, and food is diverted into a long dead-end side branch, the caecum
- The caecum houses a huge population of bacteria, some of which produce enzymes that convert cellulose to sugars, while others manufacture amino acids and other nutrients
- Micromolecules are absorbed directly through the epithelium of the caecum, and the waste material is released into the colon for disposal
Intestines
- Located between the stomach and the cloaca or anus
- Vertebrate intestines are differentiated to varying degrees into small and large intestines
- Cartilaginous fishes - have a short, thick, tapering intestine with a spiral valve where food passes slowly as it moves toward the colon
Herbivores
- The tract includes an expanded colon, cecum, or forestomach
- An enlarged colon is the principal site for microbial fermentation
- Haustrations extend over the cecum and the entire length of the colon of most species
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Description
Quiz about the anatomy and development of the vertebrate alimentary canal, including mesenteries, accessory organs, and digestive system components.
