DIGESTIVE
SYSTEM
Introduction
• concerned with the function of nutrition which
includes ingestion, digestion, absorption and egestion
• process of digestion involves the physical and
chemical breakdown of food to render it soluble and
ready for reabsorption
• tongue and teeth help in mechanical breakdown of
food
• chemical digestion occurs with help of digestive
juices containing enzymes secreted by the digestive
glands
• secretion of enzymes is basically under the control of
hormones
• passage of food along the digestive tract is aided by
gut motility controlled by nervous system
Incomplete Type
• when anus is absent, mouth serves for ingestion of
food and egestion of waste materials
Fasciola or Clonorchis
Parts:
• mouth
– anterior end
• oral sucker
– circular and muscular sucking
disc surrounding the mouth
• pharynx
– short muscle
• esophagus
– short tube from the pharynx
additional for Fasciola
• side branches or diverticula of the intestines are very
prominent and seem to fill the body
COMPLETE TYPE
• mouth and anus are present
• may be subdivided into the digestive
tract, the digestive glands, and the
accessory structures
Coelom, Peritoneum, and
Mesenteries
Coelom
• – cavity containg the visceral organs
divided into:
a. small pericardial cavity – contains the heart
b. larger pleuro-peritoneal cavity – which contains the
rest of the visceral organs
Peritoneum
– connective tissue membrane that lines the coelom
Types:
a. parietal peritoneum – lines the body wall
b. visceral peritoneum – covers most visceral organs
Coelom, Peritoneum, and
Mesenteries
Mesenteries
• two layers of the peritoneum that suspends viscera
from the dorsal body wall
• name of organ they suspend
Omentum
• double membrane continuous with the mesenteries
that connect the visceral organs with one another
• also named after organ they connect
Buccal Cavity
- large cavity exposed upon opening the mouth
Parts:
• maxillary teeth – in the upper jaw
• sticky tongue – located at the floor of the cavity which
captures food and passes it on the esophageal opening
• glottis – slit-like opening to the respiratory system and is
found at the region between the tongue and esophageal
opening
• vocal sacs – where pair of slits lead to ; slits are located
lateral to the glottis and near angle of jaw
• choanae or internal nares- pair of holes at the roof of the
buccal cavity
• vomerine teeth- pair of v-shaped formations at the root of
the mouth
• Eustachian tube – opening or recess near the angle
4
1. Vomerine Teeth
3. Opening to the Eustachian Tube
2. Internal Nares
4. Maxillary Teeth
Digestive Tube
1.
esophagus
– short tube connecting the oral cavity to the stomach
2. Stomach
– bag shaped muscle
Parts of stomach:
a. cardiac end – anterior portion continuous with the
esophagus
b. pyloric end – posterior portion continuous with the
small intestine
c. greater curvature – outer curvature
d. lesser curvature – inner curvature
e. rugae – lines of the inner wall of the stomach
3. pyloric sphincter
– constriction at the junction of the stomach and the
small intestine
Digestive Tube
4. Small Intestine
- digestive tube that has become the long coiled
structure from the pylorus
- where most chemical digestion and absorption
occurs
Has 2 regions:
a. duodenum – bends anteriorly from the pylorus and
runs parallel to the stomach
b. ileum – longer and posterior
5. Large Intestine
- where digestive tube enlarges
- further breakdown of undigested material by bacterial
action and the absorption of water occur here
Digestive Tube
6. Cloaca
– short narrow tube which opens to the outside through
the anus
- urine and gametes also pass through the cloaca and
anus
Mesenteries found in digestive system
• dorsal mesentery – digestive tube is suspended from the
dorsal body
• mesogaster – mesenteries in the stomach at its cardiac
end
• mesentery proper or mesenterium – suspends the ileum
• mesorectum – suspends rectum
7. Spleen
– dark lymphoid organ lying within the fold of the
mesorectum
Parts of the
Digestive System
3. Spleen
4. Liver
5. Stomach
6. Small Intestine
7. Large Intestine
RESPIRATORY
SYSTEM
Types of Respiratory Organs
1. gills
- aquatic animals
2. lungs
– evaginations (outpocketings )of the
digestive tube for terrestrial animals
3. tracheal system
– invaginations of the integument
(inpocketings)
TYPES OF
RESPIRATORY
SYSTEM
AQUATIC RESPIRATORY SYSTEMS
Gills of Fishes
-are delicate comb-like structures
a. Operculum – covers the gills
b. Gill chamber – part of the pharynx
c. Gill arches – bony structures where gills are arched
d. Gill filaments – arranged in parallel rows in rich in blood
capillaries, this also gives the dark red color of the gills in
live or fresh specimen
e. Pharyngeal clefts- wide slits between the gill arches which
serve for the passage of water from the pharynx to the gill
chamber
Breathing Movements of Fishes
•
water is taken in through the mouth and made to pass
through the gills then expelled out of the gill chamber
through the gill aperture
TERRESTIAL RESPIRATORY
SYSTEMS
Tracheal System of Insects
• respiratory organs consists of a
branching system of air tubes which
supplies oxygen directly to the tissues
Parts
• tracheal trunk – short segmental
branches that lead outside to spiracles
and in fine branches, the tracheoles,
connected directly to the tissues
• spiracles – where exchange of gases
occur
TERRESTIAL RESPIRATORY
SYSTEMS
Lung System of Vertebrates
Parts
• glottis – median slit, posterior to the tongue which
leads to the larynx
• arytenoids – pair of cartilages on both sides of the
glottis which is covered by mucous
• cricoid cartilage – ring shaped cartilage that borders
arytenoids
• vocal cords – a pair of elastic, thread-like bands
• lungs – pair of spongy sacs where larynx leads to
Excretory System
Frog’s Excretory System
Kidney
 flat, ovoid reddish organs lying in a space
 retroperitoneal
 adrenals maybe observed as the yellowish streaks on the
ventral surface
Cisterna Magna
 space between the muscles of the dorsal body wall and
the peritoneum
Mesonephric or Wollfian Duct
 thread like tubular structure on the lateral side of each
kidney
 continues posteriorly beyond the kidney and enters the
cloaca separately on its dorsal wall
Urinary Bladder
 connected to the ventral wall of the cloaca which serves
as storage of urine
Parts of the
Excretory System
8. Kidney
9. Urinary Bladder
Mammalian Kidney
Kidney substance is easily divisible into two regions:
• outer cortex
- contains the microscopic renal corpuscles and tubules
• inner medulla
- contains collecting tubules that open at the renal papilla
Renal Pelvis
- where renal papilla opens
- expanded beginning in the ureter or metanephric duct
Metanephric Duct
– leads tourinary bladder
Ureter
– closely associated with blood vessels
• * all are found in a concavity called the hilus
CIRCULATORY SYSTEM
Function of the Circulatory System
• Responsible for the transport of gases,
nutrients, metabolic wastes, hormones and
other substances in the different parts of the
body.
• It assists in maintaining constancy of the
internal environment (homeostasis) of the
organism
OPEN SYSTEM
• Heart
– Pericardial sinus  cavity where the heart lies; open at
the posterior end
– Dorsal Diaphragm  membrane forming the ventral
wall of the pericardial sinus
– Aorta  vessel from the anterior end of the heart,
which opens into the sinuses of the head
– Composed of a series of chambers
– Ostia: paired lateral openings at the posterior end of
each chamber which are guarded by valves
Path of Blood
•
Colorless blood from the pericardial sinus enters
each chamber thru these openings.
•
Blood is kept in circulation by the rhythmic
contraction of the chambers of the heart from the
posterior to the anterior chambers of the aorta
•
Blood then permeates into the different parts of the
body and finally returns to the pericardial sinus
through the posterior opening.
CLOSED SYSTEM
Blood Vascular System
Composed of:
a. Blood
b.
Heart
- pumping action of the heart
creates pressure that drives
- the blood to the different
parts of the body
c.
Arteries
- conveys blood from the
heart to the different parts
of the body
d.
Veins
- convey blood back to the
heart
e.
Capillaries
- connect arterioles with the
venules
Arterioles  small arteries
Venules  small veins
Lymphatic System
Composed of:
–
Lymph vessels
–
Lymph spaces
–
Lymph  circulating fluid
Where is it located?
Dorso-lateral subcutaneous connective tissue
 Tissue connecting the skin to the body wall
Dorsal subcutaneous lymph space
 space between the skin and the dorsal body wall
 where lymph is pumped into veins by lymph hearts
Lymph Hearts
 Contractile hearts found between the third vertebra and the
posterior corners of the suprascapula
Anterior Abdominal Vein
 underneath the linea alba
HEART
a. Pericardial cavity
 where the heart lies
 separated from the pleuroperitoneal cavity by
the transverse septum
b. Parietal pericardium (pericardial sac)
 lining of the heart which continues as the
visceral pericardium
c. Visceral pericardium
d. Transverse Septum
 Separates the pericardial cavity and the
pleuroperitoneal cavity
e. Pleuroperitoneal Cavity
 contains the visceral organs (minus the heart)
CHAMBERS OF THE HEART
Sinus venosus
 Dark colored triangular structure, connected to the ventral wall
of the right atrium
Left and Right atria
 anterior, thin walled
Ventricle
 posterior, thick walled
Conus arteriosus
 bulb like, lies obliquely on the dorsal wall of the right atrium
 base of all the arteries
arises from the antero-ventral side of the ventricle
* Contraction  Systole
* Relaxation  Diastole
Ventral Aspect
• Ventricle
• Right Atrium
• Left Atrium
• Conus Arteriosus
• Truncus Arteriosus
• Pulmocutaneous Artery
• Systemic Artery
• Common Carotid Artery
Dorsal Aspect
1. Ventricle
2. Right Atrium
3. Left Atrium
4. Sinus Venosus
5. Pulmonary Vein
6. Pulmocutaneous Arches
7. Systemic Arches
8. Common Carotid Arches
VENOUS SYSTEM
Principal Divisions
Systemic
 carry unoxygenated blood from the different parts
of the body directly to the right atrium
Portal
 carry unoxygenated blood through a system of
blood capillaries in the liver or kidney from where the
blood is recollected by systemic veins to be brought
back to the right atrium of the heart
Pulmonary
 carry oxygenated blood from the lungs directly to
the left atrium
VEINS
Left/Right Precaval veins
 a.k.a. anterior vena cava
 big blood vessels entering the Sinus venosus antero-lateral angles
Postcaval vein
 a.k.a. posterior vena cava
Veins connected to the Anterior vena cava
a. External jugular vein
 anterior
b. Innominate vein
c. Subclavian vein
 Brachial vein
 Musculocutaneous vein
PORTAL VEINS
Hepatic Portal System
Consist of the:
a. Hepatic portal vein
 drains blood from the following tributaries
gastric vein from the stomach
splenic vein from the spleen
pancreatic vein from the pancreas
intestinal veins from the small intestines
Ventral abdominal vein
 brings the drained blood to the liver
b. Hepatic vein
PORTAL VEINS
Renal Portal System
Consist of the:
a. Renal portal vein
 lies on the lateral margin of the kidney alongside the mesonephric
duct
b. Veins that drain from the dorsal body wall
c. Oviduct (for females)
d. Femoral vein
 anterior and dorsal sides of the thigh and the rest of the hindlimb
e. Pelvic vein
 medial branch of the femoral vein before joining the renal portal
vein
 course along the posterior abdominal wall, where they receive short
veins from the urinary bladder, and then
 unite ventrally to form the anterior abdominal vein
f. Sciatic vein
 posterior side of the thigh
Pulmonary Veins
 from the lungs they enter the left atrium
ARTERIAL SYSTEM
Arteries
 thick-walled, light colored, generally deeply
set in the body
 blood flow is pulsating or in spurts
 carry oxygenated blood (minus the
pulmonary artery)
ARTERIAL SYSTEM
Ventral Side of the Heart
Conus arteriosus
 arises from the right antero ventral side of the
ventricle
 serves as the base of all arteries
Truncus arteriosus
 anterior of the conus arteriosus
 immediately divides into the left and right trunks
Arteries connected to the Truncus
arteriosus
Common carotid artery
 anterior branch
 divides into two branches:
Internal carotid artery
carotid gland round yellowish gland located near the base
External carotid artery
Systemic artery



middle branch
arches dorsally and posteriorly
gives small branches to the:
Larynx, muscles of the jaw, dorsal side of the
esophagus, orbit, nose, vertebral column
Pulmocutaneous Artery
Branches of Systemic Artery
Subclavian artery
 supplies the shoulder and neighboring parts
 brachial artery: subclavian artery that continues to the forearm
Pulmocutaneous artery
 posterior
Dorsal Aorta
 posterior continuation of the unified left and right systemic
arches
Coeliaco-mesenteric artery
 arising ventrally at the junction of the systemic arches and dorsal
aorta
 divides into the:
coeliac artery
anterior mesenteric artery
Branches of Systemic Artery
Posterior mesenteric artery
 unpaired artery near the posterior end of the aorta, arising from
its ventral side
Left/Right common Iliac arteries
 the split of the posterior end of the aorta
Femoral artery
 small dorsally directed artery posterior to the common iliac
 supplies blood to the skin and muscles of the anterior part of the
thigh
Sciatic artery
 common iliac artery that proceeds to the rest of the hindlimb
Internal Structure of the Frog’s
Heart and It’s Branches
a. Right Atrium
 larger thin walled chamber of the heart
b. Left Atrium
 smaller thin-walled chamber of the heart
 has openings on its dorsal wall near interatrial septum for
pulmonary veins
c. Interatrial septum
 divides the left and right atrium
d. Sinoatrial aperture
 oval opening on the dorsal wall of the right atrium
 serves as the entrance of blood from the sinus venosus
Internal Structure of the Frog’s
Heart and It’s Branches
e. Ventricle
 large thick walled chamber
f. Muscular Pockets
 located at the inner wall of the ventricle
g. Atrioventricular apertures
 connects the atria and ventricle
 serves as entrance of blood to the ventricle
 guarded by valves which prevent back-flow of blood
h. Septa
 two longitudinal division within truncus arteriosus
divides truncus into three channels
Parts
1.Spiral valve
2. Right atrium
3. Left atrium
4. Ventricle
5. Truncus arteriosus
6. Pulmocutaneous arch
7. Systemic arch
8. Carotid
arch
Internal Anatomy of the
Mammalian Heart
a. ventricles
 constitute the bulk of the heart
 thick walled and highly muscular
b. apex
 posterior narrow portion
c. base
 broad anterior portion
d. atria
 anterior to the base
thin-walled and dark colored
right atrium- bigger
left atrium- smaller
 where pulmonary v. enters
Internal Anatomy of the
Mammalian Heart
e. Interatrial septum
 separates right from left atrium
f. Sinus venosus
 in adults is incorporated into this region as Sinoatrial node
(SA)
g. Interventricular septum
 completely partitions the ventricles
right ventricle
 is smaller and thinner walled
left ventricle
 includes the apex
bigger and thicker walled
Internal Anatomy of the
Mammalian Heart
h. right atrio-ventricular aperture
 opening between the right atrium and right ventricle
 guarded by three membranous flaps or TRICUSPID
VALVES
i. left atrio-ventricular aperture
 opening between the left atrium and left ventricle
 guarded by two membranous flaps or BICUSPID VALVES or
MITRAL VALVE
j. trabeculae carne
 muscular ridges that deeply cleave the inner walls of the
ventricles
k. papillary muscles
 pointed finger-like muscles
 project from the walls of the ventricles
Internal Anatomy of the
Mammalian Heart
l. chordae tendinae
 fine thread-like fibers connecting the free edges of the
tricuspid and bicuspid valves to the tip of the papillary
muscles
m. pulmonary artery
 opening in the right ventricles where the blood leaves
n. semilunar valves
 guards the exists of the right ventricle to the aorta
 guards the exists of the left ventricle to the pulmonary
arteries
NERVOUS SYSTEM AND
SENSORY ORGANS
Types of Nervous Systems
1. Diffuse type or nerve net


Simplest type of N.S.
Found in Coelenterates (Hydra)
–
–
–
–

Termed nerve net because it consists of a network of nerve
cells, each with a number of processes radiating from the cell
body in all directions
The processes of neighboring nerve cells connects to one
another to form a continuous network.
Called diffuse type because primitive nerve cells (neuries or
protoneurons)  non-polar; nerve impulses are conducted in all
directions from point of stimulation, no definite pathways
In higher types of nerve cells, nerve impulses travel in one
direction only (cell body  axon)
Main distinguishable characteristic: Lack of centralization
or absence of concentrations of nerve cell bodies at
certain areas of the body of the animal.
Types of Nervous Systems
2. Ladder type
 Dugesia (flatworm)
 Has cephalization  head region
Parts:
 Cerebral ganglia  primitive brain formed from
aggregation of nerve cells
 Longitudinal nerve cords  lie parallel to each other and
pass posteriorly along most of the entire length of the body
 Transverse nerves  rung-like structures of a ladder that
connect longitudinal nerves into a linear seriesn hence the
term ladder type of nervous system
 Lateral nerves  innervate the body wall and other
structures, arises from transverse nerves
Types of Nervous Systems
3. Ganglionic type

Found in Annelids and arthropods
Consists of:
A.
Dorsal Brain (Cerebral ganglia)

B.
located in the head
Ventral Nerve Cord


extends from the brain posteriorly along the length of the rest of
the body
Consists of a segmental series of paired, closely approximated
ganglia which are connected by two longitudinal nerves strands
C. Longitudinal nerve strands



 forms double chain of ganglia
Arthropods
N.S. is more centralized and has fewer ganglia due to migration and
fusion in the thorax and abdomen.
Longitudinal nerve strands tend to fuse into a single strand.
Types of Nervous Systems
 4. Tubular type
Found in vertebrates
Tubular: vertebrate brain and spinal cord are hollow.
Brain cavities, termed ventricles, are continued with the central
canal of the spinal cord.
Types of Nervous
System
Overall Organization of the
Vertebrate N.S.
composed of:
1. central nervous system
 includes the brain and the spinal cord
 serves as a central exchange or switchboard
2. peripheral nervous system
 consists of nerve cells and nerve fibers which connect to the
C.N.S. to all parts of the body
3. the sense organs
Peripheral Nervous System
subdivided into the:
Somatic N. S.
 innervates skeletal muscles, skin, and certain other body parts
 responsible for movement of various parts of the body thru reflex
actions and conscious control of will
Autonomic/Visceral N.S.
 innervates cardiac muscles, smooth muscles, and glands
 governs and controls the functions of the viscera (heart, digestive
tract, glands, etc…)
 carried out automatically and controlled at the unconscious level
 Includes the:
Sympathetic N.S.
Parasympathetic N.S.
*Both have antagonistic effects
Autonomic Nervous System
 It consists of the cranial nerves and spinal nerves from the
spinal cord.
Frog: 10 pairs
Man: 12 pairs
 Spinal nerves
consist of:
a. Sensory/Afferent
 Transmit impulses from the receptors to the C.N.S.
b. Motor efferent
 Transmit impulses from the C.N.S. to the effectors
Spinal Nerves



1st to 9th Spinal Nerve exit through the intervertebral
foramina
10th gets out through the lateral foramina at the anterior third
of the urostyle
Glands of Swammerdam or Periganglionic glands: masses of
white calcareous materials found at the sites of the exit of the
nerves.
Spinal Nerves
Spinal nerves
1st – connect with larger 2nd spinal nerve to form Brachial plexus
2nd – largest of the first three spinal nerves and connects with them to form
Brachial plexus
- main trunk extends to the forelimb as the brachial nerve
3rd - connect with the larger 2nd Spinal Nerve to form the Brachial Plexus.
*Plexus- a network of communicating nerve fibers
4th - extend postero-laterally do not form a plexus.
5th - extend postero-laterally do not form a plexus.
6th - extend postero-laterally do not form a plexus
7th - are sharply directed posteriorly and goes along with the 8th and 9th
spinal nerve to form the lumbo-sacral or sciatic plexus.
8th
- Joins with the 9th to form the Sciatic Nerve
9th
- Joins with the 8th to form the Sciatic Nerve
10th
- lies close to the side of the Urostyle (hard to see)
Autonomic Nervous System
 consists of 2 delicate chains of ganglia
 (Sympathetic Trunk) and several unpaired ganglia
a. Sympathetic Trunk
 originate from the cranial cavity
 lie alongside the systemic arch and dorsal aorta
b. Jugular foramina
 located lateral to the occipital condyles
c. Sympathetic ganglia
 node like structures found at varying intervals along the trunks
d. Rami communicantes or Visceral rami
 connected to the sympathetic ganglia
 * P.N.S. does not form an orderly chain of ganglia and need not be
dissected.
Central Nervous System
 The brain and the spinal cord are enveloped by two meninges or
membrane:
Outer pigmented Dura Matter
Pia Matter
*Both inseparately adhere to the nervous tissue.
 Subdural Space  in between the 2; filled with cerebrospinal
fluid
Parts of the Frog Brain
1. Telencephalon or cerebral hemispheres
 Enlarged elongated bodies separated medially by a groove, found
at the anterior part of the brain
 Found here are complex centers of consciousness and sensations
2. Olfactory bulbs
3. Telencephalon

where the first pair of cranial nerves, the olfactory nerves
originate.
4. Olfactory nerves – first pair of cranial nerves
5. Diencephalons (thalamencephalon or twixtbrain


depressed unpaired lobe posterior to the Telencephalon
The relay center for sensory impulses; centers of regulating body
temperature, water balance; carbohydrate and fat metabolism
6. Anterior Choroid Plexus

thin membrane that acts as the roof of dicencephalon
7. Pineal body or epiphysis


arising from the median dorsal surface of the diencephalon
has an endocrine function
Parts of the Frog Brain
8. Mesencephalon or optic lobes


a pair of rounded bodies posterior to the diencephalons
where visual and auditory reflex centers are located.
9. Metencephalon or cerebellum


the narrow fold posterior to the mesencepahlon
Responsible for muscle coordination and proprioception
10. Myelencephalon or medulla oblongata


Triangular portion posterior to the metencephalon. Its broad
anterior portion is partly covered dorsally by the metencephalon,
while its tapered portion is continuous with the spinal cord
Located in the various areas of the medulla oblongata are the
reflex centers that control respiration, heart rate, dilation and
constriction of blood vessels and swallowing.
11. Fourth ventricle
 The triangular cavity of the which is covered by a thin highly
vascular membrane
12. Posterior choroids plexus

thin highly vascular membrane covering fourth ventricle
Parts of the Frog Brain
12. Filum terminale


tapering posterior portion where the spinal cord extends from the
myelencephalon
occupies the cavity of the urostyle
13. dorsal median sulcus

groove that extends along the median region of the spinal cord
14. Ventral median fissure

the corresponding ventral groove of the Dorsal median sulcus
Parts of the Frog Brain
Ventral Aspect
15. Optic chiasma
 ventral side of the dicencephalon
 formed by the crossing of the fibers of the second pair of cranial
nerves
16. Optic nerves
 the second pair of cranial nerves
17. Infundibulum
 bilobed extension of the diencephalons, posterior to the optic
chiasma
18. Hypophysis or pituitary body
 a small round gland attached to the postero-ventral side of the
infundibulum, which lies on a depression on the floor of the skull
 The hypophysis has endocrine functions regulated by
neurosecretions produced in the diencephalons
19. Sella tursica
 depression on the floor of the skull
Parts of the Frog Brain
Ventricles of the brain
1. first and second lateral ventricles
 cavity of the cerebral hemispheres
 communicate with the cavity of the olfactory bulbs
2. rhincoeles
 cavity of the olfactory bulbs
3. third ventricle
 communicates with the lateral ventricles through narrow opening
foramen of Monro
4. Foramen of Monro
 narrow opening of the third ventricle
Parts of the Frog Brain
Ventricles of the brain
5. optic ventricles or opticoeles
 expanded cavities in the mesencecephalon
6. Iter or aqueduct of Sylvus
 narrow cannal where the third and optic ventricles connect with
forth ventricle
7. Fourth ventricle
 continous posteriorly with the cavity of the spinal cord
8. Central canal or canalis centralis
 cavity of the spinal cord
F
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B
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Sense Organs
The Eyes
1. Sclerotic coat
 the outermost coat of the eye
 Tough, opaque, protective structure that maintains the shape of the
eyeball.
2. Cornea
 anterior portion of the sclerotic coat
3. Conjuctiva
 thin, transparent membrane covering the outer surface of the
cornea and continuous with the inner surface of the eyelids
4. Optic Nerve
 White, thread-like structure that can be observed at the posterior
part of the eyeball.
5. Retractor bulbi
 muscles attached to the sclerotic coat around the optic nerve which
pulls the eye into the orbit
*Six other muscles are attached to the eyeball at different anges
are responsible for other eye movement.
Sense Organs
The Ear
 Sense organs of hearing and equilibrium
 Frog’s ear is composed of two parts:
Middle ear
1. external tympanic membrane
2. columella
 rod-like bone located inside the tympanic cavity
 extends across the tympanic cavity to the wall of the skull.
3. Eustachian tube
 where tympanic cavity connects with buccal cavity
Inner ear
Frog Ear