Download Frog Dissection Pre-lab

Name: ______________________________________ Block: __________ Date: _________________
Frog Dissection Pre-lab: Introduction to Frog Organ Systems
Circulatory System
The amphibian heart has three chambers. One
chamber (the ventricle - C) pumps blood away from
the heart, and the blood then divides into two
pathways of vessels. One pathway delivers blood to
the lungs and skin for gas exchange with the
environment. The other pathway transports blood to
the rest of the body. The remaining two chambers
(the right – B1 and left atria – B2) collect blood that is
returning to the heart—one atrium for each
circulatory path. This two-circuit circulation makes it
possible for oxygen-rich blood to be more efficiently
transported to the brain, muscles, and other organs.
What are the two respiratory organs of the frog?
(1) ________________________________
(2) _________________________________
What are the two gases that are being exchanged between the frog and the
environment?
(1) ________________________________
(2) _________________________________
What do you think the non-labeled structures are? _____________________________________
_______________________________________________________________________________________
What is the function of the:
o Ventricle: _______________________________________________________________________
o Atria: ___________________________________________________________________________
Why is a two-circuit circulation beneficial to the amphibian?
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Digestive System
The digestive system of the frog includes the alimentary canal from buccal cavity (mouth)
to cloaca and related glands (liver, gall bladder, and pancreas). The frog is primarily
carnivorous (worms, spiders, small insects, and so forth). It swallows its food whole.
As you are reading, stop and locate each structure in Diagram 1 provided with this
worksheet.
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The buccal cavity (mouth, oral cavity) is surrounded by the upper and lower jaws. The
edge of the upper jaw bears small maxillary teeth (B); the lower jaw has none. The roof of
the mouth is contains a pair of internal nostrils (C) which allows air into the mouth from the
external nostrils. Between these are the vomerine teeth (B’), which are used for holding
prey. At the angle of the jaws are the auditory orifices (D) leading to the middle-ear
cavity. The muscular tongue fills the floor of the oral cavity This tongue is projectile and
sticky and is used for catching prey.
The short, muscular esophagus (G) conducts food from the oral cavity to the stomach (H).
Some digestion of protein occurs here. The stomach narrows to become the small
intestine (I) which immediately turns upward. Lying within this loop is the pancreas (Q). The
small intestine merges into the shorter large intestine or colon (J). The large intestine,
responsible mainly for absorbing water and packaging fecal material, opens into the
cloaca (K) which is a chamber shared with urinary and excretory ducts.
The three-lobed liver (L) is the largest gland in the body. It receives all absorbed nutrients
from the intestine via the hepatic portal vein. It alters and stores metabolic products of
digestion and releases them into the circulatory system when needed for utilization by the
body tissues and organs. The liver also produces bile, which breaks up fats making them
more soluble in water and therefore subject to digestion by enzymes. Bile is transported
out of the liver by the hepatic ducts (N). These, and the cystic ducts (O) of the gall
bladder (which concentrates and stores bile received from the hepatic ducts), form the
common bile duct (P). The common bile duct passes through the pancreas, receives its
duct, and terminates by entering the first part of the small intestine. The enzymes from the
pancreas assist in chemical digestion of fats, protein, and sugars.
The spleen (R) (an organ of the lymphatic system) breaks down aged red blood cells. It is
also involved in the production of red blood cells.
How many sets of teeth does the frog have? What are they called and where are they
located? ______________________________________________________________________________
_______________________________________________________________________________________
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Do you think that the frog uses these teeth for chewing? Explain.
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Complete the following chart:
Organ/Cavity
Function (Role in the Digestive Process)
Buccal Cavity
Esophagus
Stomach
Small Intestine
Large Intestine
Cloaca
Pancreas
Liver
Bile:
o Where is it made? _______________________________________________________________
o Where is it stored? _______________________________________________________________
o Where is it used? ________________________________________________________________
o What is it used for? ______________________________________________________________
_________________________________________________________________________________
Respiratory System
As above, while reading, stop and locate the related structures of the respiratory system in
Diagram 1.
Air passes into the oral cavity through the nostrils (C), which then close. The floor of the
mouth rises forcing air into the glottis (F) located between the tongue (A) and the
esophagus (G). The glottis opens into the larynx (S), a chamber supported by and
containing two muscular vocal cords. Sound is created by movement of air passing
between vibrating vocal cords. Air passes through the larynx into the right and left
bronchus (T). One bronchus passes into each lung and breaks up into progressively
smaller ducts. These ducts ultimately open into sacs of air cells (alveoli) surrounded by
capillaries. It is between these alveoli and the blood capillaries that exchange of oxygen
and carbon dioxide occurs.
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What is the role of the mouth in breathing? _____________________________________________
_______________________________________________________________________________________
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How does the frog make sounds? ______________________________________________________
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What are alveoli? _____________________________________________________________________
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The exchange of oxygen and carbon dioxide occurs between the alveoli and blood
capillaries. In which direction is each gas moving?
_______________________________________________________________________________________
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Urogential System
The gonads (testes [D] and ovaries [H]) and the kidneys [A] arise embryologically as
neighboring masses on the dorsal (back) wall of the body cavity. In the male frog, the
testes and the kidney tubules share a common archinephric duct [B]. In the female, the
oviducts [I] separate from the archinephric duct [B]. The archinephric duct releases its
contents into the cloaca [G] for discharge.
Locate the structures of the reproductive and urinary systems in both sexes in Diagram 2.
Continue reading below.
The kidneys [A] are dark, reddish, elongated bodies on the dorsal body wall. They are
covered over by connective tissue lining the body cavity. Each kidney [A] consists, in part,
of thousands of tubules (nephrons). These tubules filter fluid and various molecules from
the blood. They also deliver urine into collecting ducts that open into the larger
archinephric duct [B]. This archinephric duct [B] opens into the cloaca [G]. The bladder
[C], located ventral to the ducts, stores urine arriving at the cloaca [G] from the paired
archinephric ducts [B] and releases its contents back into the cloaca [G] for discharge.
The paired testes [D] are rounded bodies lying immediately ventral to the upper (anterior)
poles of the kidneys [A]. They (and the ovaries in the female) are the site of origin for the
fat bodies, which may be quite extensively distributed in the body cavity. Each testis [D]
consists of numerous sperm-producing tubules. These tubules come together to form a
number of ducts conducting sperm cells to the kidney tubules. Sperm and filtrate from the
blood pass through the kidney tubules into the archinephric duct [B]and are conveyed to
the cloaca [G]. At their posterior ends, the ducts expand to form seminal vesicles [F],
which discharge stored sperm during copulation.
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What is a nephron? ___________________________________________________________________
_______________________________________________________________________________________
State two functions of the kidneys.
(1) ______________________________________________________________________________
(2) ______________________________________________________________________________
What does the bladder do? ___________________________________________________________
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From where do the fat bodies in a frog come?
_______________________________________________________________________________________
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Using your knowledge of lipids as a molecule, what do you think the purpose of these fat
bodies is? _____________________________________________________________________________
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Materials from what three systems pass through the cloaca?
(1) _________________________________________
(2) _________________________________________
(3) _________________________________________
The ovaries [H] are paired, highly lobulated, often massive organs (when filled with eggs)
ventral to the kidneys. During breeding season, egg-filled ovaries may fill the entire body
cavity. These immature eggs are ultimately discharged into the body cavity and, with the
aid of cilia, move to the openings of the paired oviducts [I]. The eggs pass through the
highly convoluted oviduct [I]into the dilated uterus [J] where they are stored. During
copulation, the eggs are discharged from the uterus to the cloaca, then to the outside,
where they are fertilized by the sperm ejected from the cloaca of the male, who is
mounted on the back of the female.
For what does a female frog use her uterus?
_______________________________________________________________________________________
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Where does fertilization and development of the frog embryo take place?
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Diagram 1
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Diagram 2
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