Transcript Frog dissection

Biology 1110
Lab # 5 – Review/Support Material
Frog Dissection
This presentation is not
intended to replace the
dissection lab exercise.
The purpose is to assist you if
you are dissecting on your
own, or to help review your
understanding, and prepare
for the lab practical.
Anatomical
Requirements of
the Dissection
The dissection will emphasize
the general anatomy of this
vertebrate.
The 26 required items are seen in
the diagram and listed in the
next slides.
Although there will be some
discussion regarding the
physiology (function) of
observed structures, physiology
is not intended to be emphasized
in this exercise.
EQUIPMENT REQUIRED.
PRESERVED FROG
This diagram
demonstrates the cuts
that are to be made in
order to open the body
cavity.
The cuts are made
twice, first through the
skin and then through
the entire body wall.
Frog Dissection
The initial cuts are
illustrated on this
frog.
When making any cuts
an upward pressure
prevents damage to
underlying structures.
The first cuts through the
skin have been made and
the skin has been pinned
back.
A close look at the skin
reveals the significant
vasculature (blood
vessels) in the skin.
The frog exchanges
respiratory gases utilizing
a pair of lungs and the
moist skin.
The second cuts are
made through the
abdominal wall and
thoracic (chest) wall.
The final cuts required
to open the body cavity
are animated.
The body cavities have
been successfully
opened.
You are now ready to
begin your observations.
Two dissected frogs will
be used to complete the
dissection requirements.

By clicking the forward ( ) and backward ( )
button you can jump from this requirement list to the
appropriate picture(s) and then back to the list. We
will not cover the requirements in the order
previously presented.
Liver – the largest organ in the abdominal cavity.
Heart and surrounding pericardium.
Lungs – a pair located in the thoracic (chest) cavity
Brachial nerve – a large nerve servicing the upper
extremities.
Gall Bladder and bile duct – check under the liver.
Stomach – In the abdominal cavity; C-shaped.
Pancreas – small strap of tissue within the stomach’s “C”
Intestine – trace from the stomach; small and large portion.
Peritoneum - the lining of the body cavity
Mesentery - abdominal tissue supporting numerous organs.
Spleen – lymphatic tissue found within the mesentery.
Kidneys - a pair of organs within the abdominal cavity.
Testes – primary sex organs of the male
Ovary – primary sex organ of the female
Oviduct – delivers the egg cell to the external environment.
Urinary Bladder – stores the urine produced by the kidneys.
Skeletal muscle - contraction moves the skeleton
Tendon/tendon of Achilles – tendons attach muscle to bone.
Long bone (femur) cut to demonstrate marrow cavity
Sciatic nerve - the largest nerve in the body.
The liver is a large, multi-lobed organ found within the
abdominal cavity. In addition to being a major detoxifying
organ, the liver produces most of the plasma proteins, & stores
valuable commodities. The liver also produces the bile that is
stored in the gall bladder, and used in the digestion of fats.
The amphibian heart is a three-chambered heart. Your heart
has four chambers. The heart resides within the pericardium,
a sac-like structure that contains lubricating pericardial fluid.
Both pictures clearly demonstrate the heart and pericardium.
The forceps in the right picture is holding the tissue of the
pericardium.
Additional pictures of a frog heart residing within the thoracic
(chest) cavity, and contained within the pericardium.
The pair of lungs is also located deep within the thoracic cavity.
Amphibian lungs are rather sac-like with much less surface area
than mammalian lungs. As a consequence the amphibian lung is
not as efficient.
Gas exchange through the skin helps make up for this
inefficiency. It also explains why almost all amphibians must
keep their skin moist.
Head
Head 
A brachial nerve can be seen entering each of the frog’s
forelimbs. The brachium is the upper area of each limb.
In both pictures the liver has been reflected back so as to reveal
the somewhat spherical, green gall bladder. The gall bladder
stores the bile produced by the liver. The bile is then delivered
via the bile duct to the small intestine. Bile functions in the
digestion of fats.
Liver
lobe
The stomach is a food storage organ and is involved in
the digestion of proteins. When stomach processing is
complete the material is released into the small intestine.
Stomach
The pancreas produces a variety of digestive enzymes that are
delivered into the small intestine.
The pancreas also produces a couple of hormones involved in
sugar metabolism. One of the hormones is insulin.
In the frog, the pancreas is a thin tissue strap located within the
“curve” of the stomach.
The small intestine is of considerable length and is involved in
the digestion of food and absorption of nutrients.
The larger portion of the intestinal tract is identified by the
probe in the picture on the right.
Intestinal tract
The peritoneum is the smooth, moist lining of the body
cavity. It composed of simple squamous epithelium (studied
earlier).
Peritoneum
The mesentery is made of the same tissue, and is connected to
the peritoneum. The mesentery is a double layer of this tissue
and invests many abdominal organs as seen in both pictures.
Lifting the digestive tract reveals the extensive nature of the
mesentery. This tissue has numerous functions.
When the digestive tract is lifted, and the mesentery
demonstrated, a structure within the mesentery becomes obvious.
The spleen is pointed out in both pictures.
The spleen is part of the lymphatic system. One important
function is in the breakdown and recycling of worn out red blood
cells.
The pair of kidneys, in the process of urine formation, remove
waste products, help maintain acid-base balance, electrolyte
balance and water balance.
The kidneys are located against the back body wall in the
abdominal cavity. In the pictures below they are the brown
structures identified.
Left kidney
Right kidney
The primary sex organ of this male frog are the testes. The
right testicle is pointed out in both pictures. The testes
produce the male gametes (sperm cells) that will fertilize the
female egg cells.
You can see their location close to the kidneys.
Right testicle
The female frog in the picture below demonstrates a condition
of reproductive inactivity. The ovary is the primary sex organ,
and produces the gametes (egg cells). The oviduct is also
demonstrated.
Ovary
Oviduct
The urinary bladder stores the urine produced by the kidney.
In the picture the forceps is demonstrating the urinary
bladder.
The frog’s right leg has been skinned in order to demonstrate
the large swimming and jumping muscles of the leg.
Tendons attach skeletal muscles to the bones of the skeleton.
When the muscle contracts the force is transferred through the
tendon to the bone, causing movement.
Tendon of Achilles is demonstrated
In the pictures we see that the femur has been cut. The
picture on the right demonstrates the presence of the
marrow cavity within the bone.
The largest nerve in your body is the sciatic nerve that services
the lower extremities. It is demonstrated in both photographs.
Click arrow to continue to
the frog model

The next couple of
slides will review
certain frog structures
previously seen in the
dissection.
Large Blood Vessels Above Heart
Heart
Lung
Gall Bladder
Liver
Stomach
Pancreas
Bile Duct
Spleen
Egg mass
Oviduct
Intestine
Kidneys
Urinary Bladder