Development of The Digestive Canal of the American Alligator Informative Summary


This scientific paper, published in 1910, details the developmental process of the digestive system in the American alligator. Starting with the very early embryo, the paper meticulously examines each stage, tracing the growth and changes of various organs including the pharynx, oesophagus, stomach, and intestines. It offers a detailed look at the formation of these structures, including the development of the trachea, bronchi, lungs, liver, pancreas, and the cloacal region.

The paper employs a visual approach, utilizing numerous drawings and diagrams to illustrate the intricate process of development. The author, Albert M. Reese, uses descriptive language to clarify the complex transformations occurring within the embryo. He meticulously identifies and labels specific organs, tissues, and structures, offering a comprehensive view of the alligator’s digestive system development.

Key Findings:

  • The paper details the stages of development in the American alligator’s digestive system, providing insights into the complex biological processes that shape this crucial organ system.
  • The research highlights the specific features and adaptations of the digestive system in alligators, demonstrating their evolutionary divergence from other reptilian species.
  • This detailed study contributes significantly to the understanding of the developmental biology of alligators, providing valuable data for researchers and students alike.


  • The formation of the enteron: The paper demonstrates the early formation of the enteron, the precursor to the digestive system, within the embryo. It shows how the enteron gradually develops, differentiates, and establishes the various organs of the digestive system.
  • The development of the pharynx: The paper details the evolution of the pharynx, the starting point of the digestive tract, and how it forms the gateway for food and air intake in the alligator. The research explains the formation of the velum palitum, a crucial adaptation allowing alligators to open their mouths underwater without ingesting water.
  • The specialization of the stomach: The study clarifies the development of the stomach, which evolves from a simple sac-like structure into a complex organ with distinct regions responsible for digestion. The paper notes the presence of a gizzard-like structure in the adult alligator, highlighting the specialized dietary adaptations of this species.

Historical Context:

The paper was published in 1910, a period of significant advancements in embryological research. The use of detailed drawings and diagrams reflects the burgeoning field of scientific illustration, employed to aid in understanding the intricate processes of development. The research also reflects the increasing interest in evolutionary biology, with the paper analyzing the adaptations and specialized features of the alligator’s digestive system.


  • The American alligator has a unique velum palitum, a fold in the pharynx that allows it to open its mouth underwater without ingesting water.
  • The alligator’s stomach has a gizzard-like structure, aiding in the grinding of food.
  • Alligators lack a distinct caecum, a structure common in many other reptiles, contributing to their specialized digestive system.
  • The alligator’s digestive system adapts to its diet, which consists mainly of fish, reptiles, birds, and mammals.
  • The alligator has a long and slender oesophagus that helps transport food to the stomach.
  • The alligator’s lungs are large and sacculated, enabling efficient oxygen uptake.
  • The trachea, which connects the lungs to the pharynx, is surrounded by cartilaginous rings for structural support.
  • The liver is a large organ in the alligator, playing a vital role in digestion and detoxification.
  • The pancreas secretes digestive enzymes into the duodenum, aiding in the breakdown of food.
  • The alligator’s bile duct connects the liver to the duodenum, transporting bile for fat digestion.
  • The alligator’s intestine is folded, increasing its surface area for efficient nutrient absorption.
  • The allantois, a structure involved in waste removal and gas exchange in the embryo, connects to the large intestine in the alligator.
  • The alligator’s cloaca is a chamber that receives waste products from the digestive, urinary, and reproductive systems.
  • Alligators possess a unique intromittent organ, a structure used for mating, that projects from the cloaca.
  • The alligator’s tail is long and powerful, providing propulsion and balance in water.
  • The alligator’s scales are tough and protective, offering resistance against predators and the elements.
  • The alligator’s teeth are sharp and pointed, aiding in the capture and consumption of prey.
  • The alligator’s sensory organs are adapted to its aquatic environment, allowing it to detect prey and navigate its surroundings.
  • The alligator’s eyes are situated on top of its head, providing a wide field of vision.
  • The alligator’s ears are protected by flaps of skin that close underwater.
  • The alligator’s nostrils are located on top of its snout, allowing it to breathe while submerged.


  • The embryo reaches a crown-rump length of 42mm by the time its enteron is fully developed.
  • The alligator hatchling is approximately 20cm in total length.
  • The alligator’s stomach can be up to 3 or 4mm in width.
  • The duodenum can expand to be the widest part of the intestine, with a diameter of approximately 10mm.
  • The pancreas can extend up to 10-15mm in length.
  • The large intestine is 10-15mm in length.
  • The intromittent organ can be up to 3mm in width.


  • Enteron: The primitive digestive tube that forms in an embryo.
  • Pharynx: The part of the digestive tract that connects the mouth to the oesophagus.
  • Oesophagus: The tube that connects the pharynx to the stomach.
  • Stomach: The organ responsible for the initial breakdown of food.
  • Intestine: The long tube that follows the stomach, responsible for further digestion and absorption of nutrients.
  • Trachea: The windpipe, connecting the pharynx to the lungs.
  • Bronchi: The tubes that branch from the trachea, leading to the lungs.
  • Lungs: The organs responsible for gas exchange.
  • Liver: The organ that produces bile, aiding in fat digestion.
  • Pancreas: The organ that secretes digestive enzymes.
  • Cloaca: A chamber that receives waste products from the digestive, urinary, and reproductive systems.
  • Allantois: A structure involved in waste removal and gas exchange in the embryo.
  • Intromittent organ: The reproductive organ of a male animal.


  • The paper describes the formation of the velum palitum in the pharynx, a crucial adaptation that allows the alligator to open its mouth underwater without ingesting water. This example showcases the intricate adaptations that allow alligators to thrive in their aquatic environment.
  • The paper details the development of the gizzard-like structure in the stomach, emphasizing the specialized dietary adaptations of the alligator. This example illustrates the evolutionary process that shapes the digestive system to meet the specific needs of the animal.
  • The paper discusses the formation of the bile duct connecting the liver to the duodenum, highlighting the critical role of bile in fat digestion. This example showcases the interconnectedness of organs within the digestive system and their collaborative function.
  • The paper describes the development of the lungs from simple sacs to more complex, sacculated structures. This example demonstrates the gradual progression of organ development from rudimentary to functional forms.
  • The paper illustrates the folding of the intestine to increase its surface area for nutrient absorption. This example exemplifies the intricate adaptations that enhance the efficiency of the digestive system.


This detailed examination of the developmental process of the American alligator’s digestive system provides valuable insight into the complex biological processes that shape this vital organ system. The paper highlights the intricate transformations occurring within the embryo, showcasing the remarkable adaptability and specialized features that define alligators as unique and successful species. From the formation of the pharynx and the specialization of the stomach to the development of the lungs and the complex structure of the intestine, the study provides a comprehensive understanding of the alligator’s digestive system development. This knowledge contributes significantly to our understanding of alligator biology, offering valuable information for researchers, students, and conservation efforts alike.

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