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Questions and Answers
What characterizes Bufo regularis in terms of external morphology?
Which feature is associated with the tympanic membrane of Bufo regularis?
What is the primary function of the vocal sacs in male frogs?
Which structure connects the mouth to the respiratory system in Bufo regularis?
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What distinguishes the subgular area color between mature males and females of Bufo regularis?
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During dissection, how should the frog be positioned?
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How many digits does each forelimb of Bufo regularis have?
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What is the purpose of the Eustachian tube openings in the buccopharyngeal cavity?
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What is the primary function of the Wolffian duct in males?
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What structure connects each ovary to the opposite kidney in the female genital system?
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Which chambers of the heart are visible from a ventral view?
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Where do the two oviducts open into in the female genital system?
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What is the role of the fat-body associated with the testes in males?
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What comprises the structure of the nervous system as mentioned?
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What small structure lies between the two testes in males?
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How many visible chambers does the heart have?
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What is the first step in the skin dissection of a frog?
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Which structure is part of the digestive system of the frog?
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What must be done after making the incisions in the skin?
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What distinguishes the small intestine in a frog's digestive system?
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Where is the gall bladder located in relation to the liver?
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Which organ is responsible for storing blood in the frog's body?
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What describes the kidneys in the frog's urinary system?
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Which of the following correctly identifies a component of the frog's general viscera?
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Study Notes
Phylum Chordata - Subphylum Vertebrata - Class Amphibia - Bufo regularis
- The Egyptian Toad, also known as the African Common Toad, African Toad, and African Bouncing toad, belongs to the order Anura and family Bufonidae.
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External Morphology:
- No neck or tail
- Bulging eyes with two eyelids: an immobile upper eyelid and a semi-transparent movable lower eyelid
- Sub-gular area is black in mature males, whitish in females and immature males
- Two small nostrils near the anterior tip of the head
- A circular tympanic membrane found posterior to each eye
- A parotoid gland indicated by an elevated area of skin dorsal and posterior to each tympanic membrane
- Short forelimbs with four digits and two horny pads on the ventral surface of each hand
- Longer hind limbs with five digits on each foot and a prehallux or calcar (spur-like structure)
The Buccopharyngeal Cavity
- The mouth opens into the buccal cavity, which is edentulous (lacks teeth) and indistinct from the pharyngeal cavity, forming a single buccopharyngeal cavity.
- Internal nares or nostrils: Anterior openings for the entry or exit of air
- Esophagus: Tube connecting the mouth to the stomach
- Glottis: Opening from the mouth into the respiratory system
- Vocal sacs: Flexible membranes of skin possessed by male frogs
- Tongue: Muscular structure attached to the front of the mouth; extended to catch insects (its food)
- Eustachian tube openings: Openings in the mouth leading to tubes that connect to the middle ear to equalize air pressure.
Dissection Instructions
- Preparation: Place the toad on its dorsal side (back) in a dissecting pan, and secure its limbs to the pan using pins.
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Skin incision:
- Begin the first skin incision midway between the rear legs. Make a cut along the midline of the toad, bisecting it equally.
- Continue the incision all the way up the toad's body to the neck.
- Make horizontal incisions above the rear legs and between the front legs.
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Skin and muscle separation:
- Use forceps to lift the skin flap and a scalpel to separate the skin from the muscle below.
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Opening the abdominal cavity:
- Lift the abdominal muscles away from the body cavity using scissors.
- Cut along the midline of the body to the forelimbs.
- Make transverse cuts near the arms and legs.
- Lift the flaps of the body wall and pin back.
Digestive System
- The buccopharyngeal cavity leads to the esophagus, which opens into the stomach.
- Intestine: Long and differentiated into the small intestine (duodenum and ileum) and the large intestine (rectum).
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Accessory glands:
- Liver: Large, dark red, with two lobes connected by an isthmus; the left lobe is cleft and larger than the right.
- Gallbladder: Lies between the two lobes of the liver, posterior to the isthmus.
- Spleen: Lies dorsally behind the stomach (part of the circulatory system, stores blood).
- Pancreas: Lies between the stomach and the duodenum.
Urinogenital System
Urinary (Renal) System
- Two elongated, dark red kidneys.
- A broad, irregular yellow patch on the ventral surface of each kidney is the adrenal gland.
- The Wolffian duct extends backwards from the lateral edge of the kidney and opens on the dorsal side of the cloaca.
- The urinary bladder is a thin-walled bilobed sac on the ventral side of the cloaca.
Male Genital System
- Two elongated, yellowish-white testes.
- Each testis is connected to the median edge of the opposite kidney by a thin membrane called the mesorchium, where fine tubes lead from the testis to the kidney (vasa differentia).
- The Wolffian duct is largely swollen, forming the seminal vesicle (acts as both a urinary and genital duct).
- Each testis is connected anteriorly to a fat body.
- A small, pale brown body called the Bidder's organ lies between the two testes.
Female Genital System
- Two ovaries and two oviducts.
- The ovary is a large organ that occupies considerable space in the coelom, particularly during breeding season. It's granulated, lobulated, and connected to the opposite kidney by a thin membrane called the mesovarium.
- The oviduct is a long tube that opens into the body cavity near the base of the lung on its side. It continues backwards, becoming convoluted and swelling to form the ovisac opposite the posterior third of the kidney.
- The two ovisacs unite and open together into the dorsal side of the cloaca.
- Two fat-bodies and two Bidder's organs are present, having the same relationship with the ovary as with the testis.
Circulatory System (The Heart)
- The heart has five chambers; only four are visible on the ventral or dorsal side.
- Ventral view: ventricle, two auricles (right and left), and the truncus arteriosus.
- Dorsal view: ventricle, two auricles, and the sinus venosus.
- A girdle of fat is present between the auricles and the ventricle.
Nervous System (Spinal Nerves & Sympathetic Chain)
- Ten pairs of spinal nerves.
- The first spinal nerve (hypoglossal nerve) ends in the muscles ventral to the tongue.
- The second and third spinal nerves unite, forming the brachial plexus.
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Description
Explore the fascinating features of the Egyptian Toad, Bufo regularis, a member of the Amphibia class. This quiz covers its external morphology, buccopharyngeal cavity, and distinguishing characteristics specific to this species. Test your knowledge on this intriguing amphibian!
