Dissection of frog toad _updated notes

Dissection of frog/toad
By
Wodrick Philemon Bukuku
Dip. ED, BSc ED (Biol & Chem), MSc BC
Sunday, July 28, 2019 Msalato Girls Secondary School 1

Taxonomy

External features that distinguish
male and female frogs:
a)The male Frogs
 Males are smaller than females of the
same species.
 Males are more vocal than females,
especially during the mating season.
 The male cloaca is less visible to the
exterior than the female cloaca
 Males are usually brighter than
females in colourations

 The forelegs are thicker in males than
in females
 Males have nuptial pads
b) The female frogs
 The female cloaca is more visible to
the exterior than the male cloaca.
 The females frogs are less brighter
than males in colourations.
 The forelegs are thinner in females
than in males.
 The Male frogs have nuptial pads but
not the females.

Internal features that distinguish
male and female frogs:
a) In the male frogs
 presence of the male reproductive
system which consists of the
testicles in which sperms are
produced sperms

b) Female Frogs
 Presence of the ovaries and oviduct
 The external opening of the
reproductive system is the cloaca,
which can be easily observed at the
underside of the female.

Adaptation of the frogs in its
habitat
1. They have a double life i.e. live on
land (terrestrial) and water
 Frogs start their lives as aquatic
tadpoles with gills to breathe. As
tadpoles grow into frogs, lungs
replace the gills and allow frogs to
breathe on land
2. Frogs have webbed feet that allow
them to move through the water
more efficiently.Sunday, July 28, 2019 Msalato Girls Secondary School 7

3. Their strong hind legs help them to
swim and leap more efficiently.
4. They have excellent vision to allow
them to see in poor conditions, such
as muddy water and night time
5. A frog's skin is covered with
protective mucus to keep it from
drying out.
6. They undergo incomplete
metamorphosis, this help them to
avoid competition for resources with
other animal species

7. Their skin possess poisonous glands
to defend themselves against
predator
8. The female lay a large number of
eggs which are fertilized male’s
sperm during breeding seasons to
ensure their survival

INTERNAL ORGANS

Functions of the Internal
organs of a frog:
1. Stomach
 Stores food and mixes it with
enzymes to begin digestion.
2. Small Intestine
 This is the principal organ of digestion
and absorption of digested food.

Adaptation of the small
intestine
i. Has a secretory gland which secretes
enzymes to complete digestion of
food.
ii. Has Goblet cells which secrete mucus
that allows for smooth movement of
food and protect wall of ileum from
action of digestive enzymes
iii. Very long to provide large surface
area for absorption.

iv. Highly folded/coiled to slow
movement of food to allow more
time for digestion/absorption/ and to
increase surface area for absorption.
v. Have numerous villi which increase
surface area for absorption/microvilli
which further increase surface area
for absorption.
vi.Ileum wall/villi have thin epithelium
which is only one cell thick to reduce
distance over which digested food
has to diffuse.

iv. Villi are highly vascularised/have a
rich network of blood capillaries for
rapid transport from small intestines
and maintain a steep concentration
gradient for rapid absorption.
v. Villi have lacteals for absorption of
fatty acids and glycerol
vi.Cells of ileum wall have a large count
of mitochondria to release energy for
active uptake of some food
substances across the epithelium.

3. Duodenum;
 This is the anterior (front) part of the
small intestine into which food passes
from the stomach
4. Pancreas
 This is the gland which secretes
digestive enzymes into the
duodenum.
5. Gall Bladder: is the sac which stores
bile.

6. Large Intestine:This is the posterior
organ of the digestive system which
stores undigested food.
7. Liver - Secretes bile and processes
digested food molecules
8. Urinary Bladder - The organ that
collects and stores urine until
released.
9. Fat Bodies - Masses of fat in the body
cavities of frogs. Needed for
hibernating and mating

10.Spleen: Organ in the frog’s
circulatory system that makes,
stores, and destroys blood cells.
11. Cloaca: Organ through which the
products of the frogs digestive and
urogenital system pass when
discharged from the body
12. Oesophagus; Esophagus is the
tube that connects the mouth and the
stomach in a frog
13.The cloaca:This is the opening
through which undigested food,
urine, eggs, and sperm are passed

Urinogenital System
 The frog's reproductive and excretory
system is combined into one system
called the urogenital system.
Parts of excretory system
1. Ureters - Tubes in a frog that carry
urine from the kidneys to the bladder
2. Urinary Bladder - The organ that
collects and stores urine until
released.
3. Kidneys- urine formation

4. Adrenal gland – production of
hormone

Functions of parts of
reproductive System
1. Ova or Eggs - Female sex cell or
gametes
2. Fat Bodies - The fat bodies are
needed for hibernating,
metamorphosis and for mating.
 These are areas in the body
containing stored energy.

Functions of parts of the
female reproductive system
3. Ovaries - Organs of the female
reproductive system that produce the
eggs.
4. Oviducts - Tubes of a female frog’s
reproductive system that carry eggs
from the ovaries to the cloaca
5. Mesovarium is a thin layer of
peritoneum that envelope the ovary
6. Ovisac – It is a sac-like structure
used for temporary storage of eggsSunday, July 28, 2019 Msalato Girls Secondary School 21

Functions of parts of the
male reproductive system
1. Testes - Male sex organs that
produce sex cells (sperm).
2. Vesicula seminalis (Seminal Vesicles)
- Enlarged distal sections of the male
frog’s urinary ducts that collect
sperm prior to entry into the cloaca
3. Mesorchium is the capsule of the
testes in male frog that offer
protection

4. Vasa efferentia- The vasa efferentia
arise from each testis and enter the
kidney to open in the Bidder's Canal
NB:
 Bidder's canal is present inside kidney
of frog. It receives sperms from
testes via a number of vasa
efferentia.

Guideline for marking the
dissection work
 Display your dissection correctly
and leave it for assessment
 A drawing must be large covering
at least 75% of a page
a) Magnification
 The magnification for mouse and
frog/toad drawing must have the
following range X 1 ½ – X4

 Note that:
𝑀𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛
𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑟𝑎𝑤𝑖𝑛𝑔 𝑜𝑓 𝑎𝑛 𝑜𝑏𝑗𝑒𝑐𝑡
𝑎𝑐𝑡𝑢𝑎𝑙 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑒𝑎𝑙 𝑜𝑏𝑗𝑒𝑐𝑡

b) The drawing must be neat and well
labeled
c) There must be title
d) Neatness of your dissection work

The dissection display
Assignment
 Using dissection guide book draw a
large and well labelled diagram of the
following systems
1. Viscera general
2. Digestive system

2. Digestive system
 Male digestive system

 Female digestive system

3. Urinogenital system
 Male urinogenital system

 Female urinogenital system

Nervous system

Dissection of frog toad _updated notes

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Dissection of frog toad _updated notes