Exercise 17: Digestive System

• Digestive system - Mechanically and chemically breaks down food into simpler molecules that can be absorbed and utilized by the cells in the body
• Food components that cannot be broken down into such state are excreted as fecal waste
• Incomplete digestive system - characterized by a digestive tract that ends blindly where undigested waste material is egested through the mouth
• What specimen of the flukeworm consist of two linear branches?

  Clonorchis sinensis
• Label the following in the Clonorchis sinensis flukeworm digestive system.

  A) Mouth

  B) Oral sucker

  C) Pharynx

  D) Esophagus

  E) Intestines

  
• Complete digestive system - characterized by having an additional orifice for the exit of undigested waste material.
• The orifice could be in the form of an anus or a cloaca
• What is the most prominent feature of the foregut of the cockroach?

  Crop
• What is found posterior to the crop of the cockroach?

  Gizzard
• What marks the anterior end of the midgut?

  Gastric ceca
• Label the following digestive parts of the cockroach.

  A) Foregut

  B) Midgut

  C) Hindgut

  D) Crop

  E) Esophagus

  F) Gizzard

  G) Gastric ceca

  H) Malpighian tubules

  I) Colon

  J) Rectum

  
• Toads have cloaca as well but in addition to being the exit for feces and urine, what else does it exit?

  Gametes
• Digestive tract - Where the food passes through
• Digestive glands - outgrowths which secrete enzymes towards the tract via ducts
• In the toad, the space within the mouth is referred to as what?

  Buccal cavity
• The maxillary teeth line what?

  Maxillary arch
• On the roof of the Buccal cavity, what are the paired openings found anteriorly?

  Internal nares
• What is found posterior to the internal nares that are lined with serrations?

  Vomerine teeth
• What collectively help in grasping prey in the toad's mouth?

  Vomerine teeth, maxillary teeth
• The glottis is surrounded by what specific kind of tissue?

  Cartilage
• Label the following in the Buccal cavity of the toad.

  A) Internal nares

  B) Vomerine teeth

  C) Maxillary teeth

  D) Esophagus

  E) Glottis

  F) Tongue

  
• Coelom - space containing the visceral organs
• Pleuro-peritoneal cavity - In toads where part of the coelom is located at the chest and the abdomen
• Pericardial cavity - contains the heart
• Peritoneum - surface of the pleuro-peritoneal cavity which is composed of squamous epithelia and supporting connective tissue
• The peritoneum that lines the inner body ball is the parietal peritoneum, while the visceral peritoneum forms the surface of the organs
• Mesenteries - continuations of the peritoneum that hold or suspend the organs in place which are double membranes and can attach from the dorsal or ventral body wall
• Omentum - double-membrane peritoneal derivative which serves to bridge or hold together certain visceral organs
• Label the following in the toad peritoneal cavity.

  A) Pleuro-peritoneal cavity

  B) Parietal peritoneum

  C) Visceral peritoneum

  D) Mesentery

  E) Omentum

  
• Esophagus - tubular organ that extends from the buccal cavity and it serves as the passageway of ingested food to a large, bean-shaped muscular organ, the stomach
• What marks the boundary of the stomach and the small intestine?

  Pyloric sphincter
• Mesogaster - dorsal mesentery that suspends the stomach at the cardiac end
• Small intestine - posterior to the stomach is coiled and tubular and is where most of the chemical digestion and absorption is completed
• Mesentery proper - Dorsal and highly vascularized mesentery that suspends the small intestine
• Lesser omentum - Translucent membrane stretching from the liver to the stomach and the duodenum
• Mesorectum - Dorsal mesentery that suspends the large intestine and spleen
• Spleen - Near the junction of the small and large intestine, one can see a small dark-colored ovoid organ suspended on a mesentery
• The spleen is part of what system?

  Lymphatic system
• Liver - large dark-colored organ composed of many lobes
• Gall bladder - round sac-like organ suspended between the right and left lobes of the liver