7. structural organisation in animals

Chapter-7
STRUCTURAL ORGANISATION IN ANIMALS
Presented by
B.Prabhakar
Principal
JNV. Panchmahal (Guj)

Earthworms have long cylindrical body.
Their body is divided into more than 100 short
segments which are similar.
Dorsal surface is marked by dark median mid dorsal
line.

The ventral surface shows the presence of genital openings.
Anterior end consists of mouth and a prostomium.
Prostomium is a lobe which serves as a covering for the
mouth
The prostomium is sensory in function.
The first segment of body is called peristomium which
contains the mouth.

In mature worms segments are
covered with a prominent dark band
of granular tissue called clitellum.
Thus, the body is divided into 3
regions -
1) Preclitellar
2) Clitellar
3) Postclitellar

Four pairs of spermathecal are located on
ventro-lateral sides of intersegmental grooves,
5th - 9th segment.
A single female genital pore is present on
14th segment.
A pair of male genital pore is present on 18th
segment

Nephridopores are the tiny pores which open
up on the surface of body.
In each segment except for first, last and
clitellum there are rows of 'S' shaped setae

Body wall is covered by an external cuticle
Below the cuticle is the:
Epidermis (single layer of columnar epithelium;
contains secretory gland cells)
Two muscle layers (circular and longitudinal)
Innermost coelomic epithelium

Digestive System of the Earthworm

Closed type of circulatory system
Contractions of blood vessels
keep the blood circulating in one
direction.
Smaller blood vessels supply
blood to the gut, nerve cord and
body wall.
The 4th, 5th and 6th segments have
blood-producing glands

Excretory system
• Nephridia
Segmentally
arranged nephridia
are the excretory
organs.
There are three
types of nephridia
septal,
integumentary and
pharyngeal.

Reproductive
systemEarthworm is
hermaphrodite or
bisexual .
Male reprodutive organs
•Testis
•Seminal vesicles
•Semimal funnels
•Vasa differentia
•Prostate glands

Female reproductive system
•Ovaries
•Oviduccal funnels
•Oviducts
•Spermatheca
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Head of cockroach is triangular in shape and lies anteriorly at right angles to the longitudinal body axis.
It is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck
(The head capsule bears a pair of compound eyes. A pair of thread like antennae arise from
membranous sockets lying in front of eyes. Antennae have sensory receptors that help in monitoring
the environment. Anterior end of the head bears appendages forming biting and chewing type of
mouth parts. The cockroach mouthparts consisting of a labrum (upper lip), a pair of mandibles, a pair
of maxillae and a labium (lower lip). A median flexible lobe, acting as tongue (hypopharynx), lies within
the cavity enclosed by the mouthparts (). Thorax consists of three parts – prothorax, mesothorax and
metathorax. The head is connected with thorax by a short extension of the prothorax known as the
neck. Each thoracic segment bears a pair of walking legs. The first pair of wings arises from mesothorax
and the second pair from metathorax. Forewings (mesothoracic) called tegmina are opaque dark and
leathery and cover the hind wings when at rest. The hind wings are transparent, membranous and are
used in flight.
The abdomen in both males and female cockroaches consists of 10 segments. In females, the
7th sternum is boat shaped and together with the 8th and 9th sterna forms a brood or genital pouch
whose anterior part contains female gonopore, spermathecal pores and collateral glands. In males,
genital pouch or chamber lies at the hind end of abdomen bounded dorsally by 9th and 10th terga and
ventrally by the 9th sternum. It contains dorsal anus, ventral male genital pore and gonapophysis. Males
bear a pair of short, threadlike anal styles which are absent in females. In both sexes, the 10th segment
bears a pair of jointed filamentous structures called anal cerci.

Give spot is a labium forms unpaired
structure called lower lip. It is made
up of three broad basal parts – a
broad basal plate the submentum, an
oval middle plate, the mentum, a
small prementum.The prementum
bears in front in pair of inner lobes
called glossae & a pair of outer lobes
called paraglossae.The prementum
also bears on the lateral sides a pair
of three jointed labial palps, each of
which is raised on a short projection
called palpiger.The labium prevents
the loss of food material from the
mandibles & pushes the masticated
food material in the mouth

These are mouth parts of cockroach
situated behind the mandible.
Each one consist of two basal segment –
cardo & stipe.
Stipe bears a five segmented maxillary
palp having sensory bristles.
From the inner side of stipes arise two
lobes, an outer galea & inner lacinia
.They are used for holding the food &
bringing it to the mandibles for
mastication.

THORAX OF
PERIPLANETA
1) Thorax is the second tegmata of the body
of cockroach.
2) It consists of three segments namely,
prothorax,mesothorax and metathorax.
3) Each segment is covered by four sclerites,
A dorsal- tergum,
A ventral – sternum and
Two lateral – pleura.
4) The dorsal sclerites or terga of the thorasic
segments are called pronotum, mesonotum
and metanotum respectively.
5) The pronotum is roughly triangular and is
the largest sclerite on the body of cockroach.
6) Mesonotum and metanotum are roughly
rectangular.
7) Thorax bears three pairs of jointed legs,
two pairs of wings and two pairs of large
spiracles

) Three pairs of legs are articulated with the pleura and
sterna of the thorasic segments.
2) Each leg is made upof five main podomeres.
3) The different podomeres from the base to the tip are
A. COXA-Is the first podomere. It is stout, broad and
muscular.
B. TROCHANTER- Is the second podomere.It is the smallest
podomere.Triangular in shaped and movably articulated to
the coxa.
C. FEMER – Is the third podomere.It bears immovable
bristles.
D. TIBIA – It is the fourth podomere. It also bears immovable
bristles .
TARSUS – Is the last podomere. It is made of five segments.
These segments of tarsus aie called tarsomeres. The last
tarsomere is called pretarsus.
The pretarsus bears a pair of claws .A chitinous spongy pad
called pulvillus or arolium is present between the claws.
Minute pads called plantulae present on the inner edges of
the first four tarsomeres.
4) Arolium and claws help in locomotion on rough surfaces.
5) Plantulae are useful in locomotion on smooth surfaces.
6) The striated muscles help the cockroach to move he legs.
WINGS:-

The alimentary canal is divided into:
Foregut
Midgut
Hindgut
Foregut:
Is lined by a cuticle
Consists of a mouth which opens into the tubular pharynx,
leading into the oesophagus, which further opens into a sac-like
crop that stores the food
The crop leads to a gizzard (proventriculus). The gizzard helps in
grinding food as it has an inner layer with six chitinous teeth.
The junction of the foregut and midgut has rings of 6 to 8 tubules
called hepatic or gastric caecae, which secrete digestive juices.
The hindgut is broader than the midgut, and consists of:
Ileum
Colon
Rectum (opens through the anus)

The digestive system of cockroach
consists of
an alimentary canal and
the associated glands.
The preoral cavity , surrounded by
the mouth parts, is present in front
of the mouth.The hypopharynx
divides the mouth in into two
chambers called
anterior – cibarum and
posterior – salivarium.

The alimentary cnal of cockroach is a long tube and
coiled at some places. It extends between the
mouth and the anus . It is divided in to three
regions, namely ,
Foregut or stomodaeum ,
Midgut or mesenteron , and
Hindgut or proctodaeum.
The foregut and the hindgut are internally lined by
ectoderm. The mesenteron is lined by the
endodermal cells.

FOREGUT OR STOMODAEUM :-
The foregut includes
Pharynx,
Oesophagus ,
Crop and
gizzard.
The foregut is internally lined by a chitinous cuticle.
Mouth opens in the pharynx, which in turn leads into a narrow tubular oesophagus.
The oesophagus opens behind into a thin walled distensible sac called crop.
The crop serves as a reservoir for storing food.Its outer surface is covered by a network
of tracheae.
A thick walled muscular gizzard or proventriculus is present behind the crop.
The chitinous inner lining of the gizzard has six powerful chitinous plates or teeth. A
hairy pad with backwardly directed bristles is present behind each teeth.
Among these teeth , food is thoroughly ground into fine particles. These fine food
particles are filtered with the bristles. Thus the gizzard acts both as a grinding mill and
also as a sieve.
A funnel ike membranous projection of the gizzard called stomodaeal valve is present
at the junction of gizzard and the midgut. This valve prevents the backward passage of
food from the mesenteron into the gizzard.

MIDGUT (MesenteronOr Ventriculus) :-
The midgut is a short and narrow tube behind the gizzard. It is also called mesenteron
or ventriculus.
Six to eight finger like projections called hepatic caecae are present between the
ventriculus and the gizzard, arising from ventriculus.
They are helpful in digestion and absorption of the digested food materials.
Ventriculus is divided into
an anterior –secretory part and
a posterior – absorptive part.
The secretory part of the midgut has many gland cells and it secrete several enzymes.
In the mesenteron the food bolus is enveloped by a chitinous and porus membrane
called peritrophic membrane. It is secreted by the stomodeal valve of the gizzard.
The peritrosphic membrane protects the wall of the the ventriculus from hard food
particles in the food.
Digested food is absorbed inro the blood through the peritrophic membrane in the
posterior absorptive region of the ventriculus.
The opening of the ventriculus into the hindgut is controlled by a sphincter muscle. It
prevents entry of undigested food and uric acid from the hindgut into the midgut.

HINDGUT ( PROCTODAEUM ):-
The hindgut isa long coiledtube.
It consists of three regions namely ileum,colon and rectum.
The midgutis internally lined by chitinous cuticle.
The ilium is a short tube, that lies behind the mesenteron.
Six bundles of fine yellowtubules called Malpighian tubules
open in to the ilium near the junction of mesenteron and ilium.
Ilium collects uric acid from Malpighian tubules and undigested
food from mesenteron.
The ilium opens behind into a long coiled tube called colon.
Colon leads behind into a shortand wide rectum.
Rectum bears six longitudinal chitinous folds called rectal
papillae on its inner surface.They are concern with the
reabsorption of water from the undigested food.
The rectum opens out through the anus.

Periplaneta has double mode of locomotion.
1. Running (Cursorial locomotion).
2. Flying.
RUNNING :-
1. Cockroach is a cursorial insect. It can run on the ground with the help of legs.
2. During cursorial locomotion , cockroach forms two tripods with its legs.
3. Each tripod is formed by foreleg and hind leg of one side and the middle leg of
the other side.
4. during locomotion , the three legs of one tripod are kept on the ground and the
other three legs of another tripod are carried forward.
5. In this process, the foreleg pull the body , the hind leg push the body while the
middle leg acts as a pivot.
6. Thus cockroach moves using the two tripods alternatively.
7. The animal does not slip back as plantulae, pulvilli and claws provide grip.
8. The claws and the arolium help in locomotion on rough surfaces
whereas plantulae areuseful on smooth surfaces.

FLYING :-
The cockroach can fly over short distances with the help of its wings.
While flying the first pair of wings is stretched out at right angles to the
body.
The second pair of wings is moved up and down during flight.
Wings are elevated by the contraction of dorsoventral muscles.
Contraction of the dorso-longitudinal muscles depresses the wings.

The blood of cockroach is colourless and it cannot carry oxygen to
different tissues due to the absence of respiratory pigment.
Therefore a tracheal system is developed to carry the air directly to
rhe tissues. The respiratory system of cockroach consists of
1.Stigmata
2. trachea and
3.tracheoles.
RESPIRATORY SYSTEM OF PERIPLANETA

1.STIGMATA or SPIRACLES:-
1. The tracheal system communicates with the
exterior by ten pairs of openings called
stigmata or spiracles.
2. the first two pairs of stigmata are present in
the thorasic segments, one pair in mesothorax
and one pair in the metathorax.
3. The remaining eight pairs of spiracles are
present in the first eight abdominal segments.
4. Spiracles are located in the pleura of
their respective segments.
5. The spiracles of cockroach are polyneustic
and holopneustic.
6.Allspiracles are valvular.
7.Each spiracle is surrounded by a chitinous
ring called peritreme.
8. Each spiracle bear small hair like structures
called trichomes. They filter the dust particles.
9. Each spirracle opens into a small chamber
called atrium.

From the atrium of each thoracic spiracle several tracheae run inside. They join with each
other in the thorax to form many tracheal trunks like dorsal cephalic, ventral cephalic trunks
and their branches.These branches enter all organs of the head.
From the atrium of each abdominal spiracles three tracheal tubes aise. They
are
A. Dorsal tracheal tube
B. Ventral tracheal tube
C. Lateral tracheal tube.
All these tracheal tubes of one side open into three separate longitudinal tracheal trunks. They
are
A. Dorsal longitudinal trunk
B. Ventral longitudinal tracheal trunk and
C. lateral longitudinal tracheal trunk.
The lateral longitudinal tracheal trunks are the longest tracheal trunks.
The three pairs of longitudinal trachealtrunks of both sides are interconnected by many
commissural tracheae.
Several branches are given out from all the tracheal trunks and they enter different organs.

STRUCTURE OF TRACHEA
The wall of the trachea is made of three
layers . They
are
A. an outer – basement
membrane
B. a middle – alayer
of epithelium
C. an inner – layer of cuticle.
The inner cuticle is called intima.
The intima produced in to spiral thickenings
called taenidia. The taenidia keep the
tracheae always open and prevent it from
collapsing.

3.TRACHEOLE:-
1. All the tracheal branches entering into
an organ end in a special cell called
tracheole.
2. The terminal cell has many intracellular
tubular branches called tracheoles.
3. Tracheoles are formed of a protein
called trachien. Tracheoles are devoid of
intima and taenidia.
4. Tracheolar fluid is present inside the
tracheoles. The level of the tracheolar fluid
varies with the metabolic activity of the
insect.
5. The level of the tracheaolar fluid is more
when the insect is inactive and it is less
when the insect is more active.
6. Tracheoles penetrate thecell and are
intimately associated with mitochondria to
supply oxygen to them.

MECHANISM OF RESPIRATION:-
Respiration includes two events, they are
I. Inspiration and
II. Expiration.
The dorsoventral muscles and ventro longitudinal
muscles helps in respiratory movements of
periplaneta . Dorsoventral muscles are the
principal muscles of respiration.

INSPIRATION:-Taking in of air is inspiration.
During inspiration the thoracic spiracles are kept open and the
abdominal spiracles are kept closed.
It is affected by the relaxation of dorsovenral muscles
and ventrolongitudinal muscles.
Due to the relaxation of dorsoventral muscles body tergum is
elevated and the volume of the body cavity increases.
Due the relaxation of ventrolongitudinal muscles, the telescoped
segments come to the normal position. So the volume of the
body cavity increases in the longitudinal axis.
Due to the relaxation of muscles this process is a passive
process.

EXPIRATION:- 1.Sending out of air from the body is called
expiration.
2.During expiration thoracic spiracles are closed and abdominal
spiracles are kept OPENED
3.It is affected by the contraction of dorsoventral muscles and ventro
longitudinal muscles.
4.On contraction of dorsoventral muscles depress the tergal plates.
Body cavity decreases in size and
pressure increases
5.Due to the contraction of the ventro longitudinal muscles , the
segments are telescoped and the volume of the body cavity decreases
in the longitudinal axis increasing the pressure
further.
6.As the process involves the contraction of muscles, expiration is
described as active process.

The exchange of gases depends on the metabolic rate and temperature.
2) When air enters the tracheoles, oxygen diffuses faster into the tissues due to
its high partial pressure.
3) At the same time the carbon dioxide of tissues, instead of passing into the
tracheal system,goes into the haemolymph.
4) Carbon dioxide is carried more quickly into the haemolymph due to its
greater solubility in it. This carbon dioxide accumulates near the spiracles and
diffuses in to the atrial chambers near the spiracles and goes out in bursts
through the abdmonial spiracles.
5) Cockroach and some other insets such as grasshoppers and beetles exhibit
the phenomenon of discontinuous ventilation. In this mode of respiration
continuous exchange of gases is interrupted by extended periods during which
spiracles remain closed . The expulsion of carbon dioxide from the body occurs in
bursts, when the spiracles are open.

The gonapophyses are small chitinous processes arising from the
ninth sternum in the males and eigth and ninth sterna in the
females.
Gonapophyses are the external genital organs
.
The males have three gonapophyses. These are formed from the
ninth sternum.They help in copulation.
In males gonapophyses are also called as phallomeres. The three
phallomeres are the ventral , left and right phallomeres.
Females have three pairs of gonapophyses.
The eighth sternum bears one pair called first basi volvulae. The
ninth sternum bears two pairs called valvifers and second
basivalvulae respectively.They guide the ova into ootheca . in
females they also called ovipositors.

NERVOUS SYSTEM OF PERIPLANETA
AMERICANA
The nervous system of periplaneta
consists of
•Central nervous
system
•Peripheral nervous
system
•Autonomous nervous
system.

CENTRAL NERVOUS SYSTEM:-
The central nervous system of
periplanata consists of a
• Nerve ring
•Double ventral nerve cord.

NERVE RING :-
The nerve ring is present around the oesophagus. It is formed by the brain , sub-
oesophageal ganglion and circum-oesophageal connectives.
Brain :-
Brain is the spra-oesophageal ganglion. It lies above the oesophagus.
Brain has three lobes. They are protocerebrum , deutocerebrum and
tritocerebrum.
The protocerebrum receives sensory impulses from the compound eyes
throughoptic nerves; Deutocerebrum receives sensory impulses from antennae
through antennal nerves; and tritocerebrum receives sensory impulses from the
labrum. Hence brain is principally sensory in nature.
Sub-oesophageal ganglion :-
Sub-oesophageal ganglion lies below the oesophagus.
It controls the movement of mouthparts, legs and wings. Hence it is the
principal motor center.
Circum-oesophageal connectives :-
A pair of circum-oesophageal connectives is present around the oesophagus,
connecting the tritocerebrum with the sub-oesophageal ganglion.

VENTRAL NERVE CORD :-
The two ventral nerve cords are solid and
ganglionated.
They arise from the sub-oesophageal ganglion and
extend upto the 7thabdominal segment.
Two nerve cords are connected by a ganglion in each
segment .
In periplaneta total nine ganglion are present on
ventral nerve cords.
Three are thoracic ganglion and six are abdominal
ganglion.
Three thoracic ganglia are present , one in each
thoracic segment.
The first to the fourth abdominal segments have one
abdominal ganglion each.
The fifth abdominal segment has no ganglion.
The serially 5th abdominal ganglion is present in the
sixth segment
the 6th abdominal ganglion is preent in the seventh
segment.
The last or the sixth abdominal ganglion is the
largest of all the abdominal ganglia. It is formed by
the fusion of the ganglion of the 7th, 8th , 9th and
10th abdominal segments.

PERIPHERAL NERVOUS SYSTEM:-
The peripheral nervous system consists of nerves that arise or go to different ganglia.
Brain is the chief sensory organ. It receives a pair of optic nerves, from the compound
eyes , a pair of antennal neves fron the antennae and a pair of labral nerves , from the
labrum.
Sub-oesophageal ganglion gives off motor nerves to the mandibles, maxillae, labium,
wings and legs. It is the principal motor centre in the body.
Thoracic ganglia supply nerves to the parts of their respective segments.
Meta thoracic ganglia send nerves to the first abdominal segment also.
Nerves from the first four abdominal gangia supply to the organs of the segments 2-6
serially.
The fifth ganglion present in the 6th abdominal segment innervates the organs of that
segments.
The sixth ganglion present in the 7th abdominal segment innervates the all organs
present in 7th – 10th abdominal segments. The organs include the reproductive organs ,
copulatory appendages besides anal cerci.

AUTONOMOUS NERVOUS SYSTEM :-
This system is also called stomogastric nervous system or visceral nervous
system.
It controls the visceral organs , particularly the muscles of the alimentary
canal and the heart.
The autonomous nervous system includes four ganglia, a frontal ganglion ,
a hypocerebral ganglion, a visceral ganglion and a proventricular ganglion.
A frontal gangli`on on the dorsal wallof the pharynx, in front of the brain.
Hypocerebral ganglion is above the oesophagus behind the brain. A visceral
ganglion is on the wall of the crop and a proventricular ganglion is on
thegizzard.
These ganglia contain the somata of the post ganglionic motor neurons.
Pregnglionic motor neurons of tritocerebrum go to the frontal ganglion as
labor-frontal andfrontal nerve.
Frontal ganglion is connected to the hypocerebral ganglion by a recurrent
nerve.
Hypocerebral ganglion is connected to the visceral ganglion and in turn the
visceral ganglion is connected to the proventricular ganglion.

In cockroach , various structures like antennae , labium , maxillary palps, labialpalps ,
compound eyes , simple eyes etc., are sensory in nature .
These structures contain various receptors like chemoreceptors, mechanoreceptors,
photoreceptors , thermoreceptors ,etc.
These receptors contain units like ommatidia , sensilla and scolopodia.
OMMATIDIA:- These are the units of photoreceptors like compound eyes.
SENSILLAE:- These are the units of cuticular receptors and chemoreceptors.
Each sensillum consists of a
1.trichogen cell with a movable hair like process ,
2.a tormogen cell that forms the socket around the base of the movable hair and
3.a sensory neuron which starts at the base of the hair and conducts impulses to the central
nervous system.
SCOLOPODIA:- These are the units of mechanoreceptors of chordo – tonal organs.
Scolopodium is present below the epidermis. It contains an 1.attachment -cell that attaches
the scolopodium to the epidermis ,
2.scolopale -cell that forms the cilium and a nerve cell.

FUNCTIONS:-
1.Mechanoreceptors are cuticular and subcuticular.
Cuticular mechanoreceptors are tactile receptors – sensitive to touch and
proprioceptors – precise position of the body parts. These are with units, sensillae.
Chordo-tonal organs contain subcuticular mechanoreceptors with scolopodia.
These are sensitive to ground vibrations .
Tympanal organs , which are sensitive to sound vibrations . These are present in anal
cerci.
Jhonston’s organs , which are sensitive to the movement of flagellum with respect to
the pedicels and flagella.
Sub-genual organs ,which are sensitive to movement of flagella of antennae.
2. Olfactory sensilla are a kind of chemoreceptors which are sensitive to smell.
These are distributed over the antennae, maxillary paips and labial palps.
3.Gustatory sensilla are also a kind of chemoreceptors , which are sensitive to taste.
They are located on theinner surface of the labrum and on the maxillary and labial
palps.
4.Thermo receptorsarea kind of machano receptors and are located on the first,
second and third segment of the tarsus of legs.

2. Olfactory sensilla are a kind of chemoreceptors which
are sensitive to smell. These are distributed over the
antennae, maxillary paips and labial palps.
3.Gustatory sensilla are also a kind of chemoreceptors ,
which are sensitive to taste. They are located on theinner
surface of the labrum and on the maxillary and labial
palps.
4.Thermo receptorsarea kind of machano receptors and
are located on the first, second and third segment of the
tarsus of legs.

OMPOUND EYE OF PERIPLANETA
A pair of dark kidney shaped compound
eyes is present on the dorsolateral sides of
the head, one on each side. Each compound
eye is composed of about 2000 functional
units called ommatidia, which are optically
independent. The outer surface of the
compound eye is divided into about 2000
hexagonal areas called facets. Each facet is
the outermost portion of a corresponding
ommatidium

) Genital aperture :- The genital
aperture in male is present just
below the anus on one of the
gonapophyses and in females it is
located on the eigth sternum.

1.Cornea:-
Cornea is the outer most part of an ommatidium .It
corresponds to a hexagonal facet of the compound eye. It is a
biconvex transparent part of the cuticle. It allows light rays to
pass through it.Cornea is the refractive region of ommatidium.
It is secreted by specialised cells of epidermis.
These are two transparent specialised epidermal cells.
They secrete cornea . These cells later become
withdrawn to the sides of the ommatidium and form
the primary pigment cells.
2. Caneagen cells or Lenticular cells
3. Vitrillae or cone cells ( Semper cells ) :-
These are the four transparent conical cells. They lie
below the corneagen cells. They surround the
transparent crystalline cone. Cryastalline cone is
secreted by the cone cells.

4.Crystalline cone :-
Crystalline cone is the transparent conical structure that secreted by
the vitrellae and is surrounded by them.
Light absorbing dark primary pigment cells called Iris
pigmented sheath surround the vitrellae.
The region containing the cornea and crystalline cone constitute the
dioptrical or focussing region of the ommatidium.
Crystalline cone focuses the light on to the next part of the
ommatidium.

1.Retinulae are innermost and elongated cells of an ommatidium.
2. Retinulae are three in number.These are the photoreceptor cells of ommatidium.
3. They rest on the basement membrane with their inner ends of the long axis.
4. Each retinular cell bears microvilli towards the inner surface of the cell. Microvilli of
each retinular cell collectively form a rhabdomere that contains
photoreceptor pigment.
5. These rhabdomeres fuse along the axis of the ommatidium to form the rhabdome in
the centre.
6. Retinulae are the nerve cells from which sensory nerve fibres leave as optic nerve to
reach the protocerebrum.
7.Rhabdome and retinulae form the retinal or receptor region.
8.Receptor region is surrounded by light absorbing seven secondary pigment cells calle
retinular pigmented cells .They serve to isolate each ommatidium
5. Retinulae and Rhabdome :-

The position of retinulae below the vitrillae orcone
cells is different in diurnal andnocturnal insects. The
manner in which the images of objects formed in
both the types ofinsects. The two typesof images
formed in ommatidia are
Apposition image,
Superposition image.

APPOSITION IMAGE
Apposition images are formed in diurnal insects like houseflies.
In these insects retinulae lie immediately below the vitrillae and
crystalline cone.
Retinulae are surrounded by secondary pigment sheath , which
absorb light rays and prevent them from passing to the adjoining
ommatidium.
Vitrillae are surrounded by primary pigment sheath.
Therefore, only light rays entering the cornea of ommatidium
converge on the rhabdome. Thus, a small separate image of a part of
the object is formed in each ommatidium.
The total image formed in the compound eye is a mosaic of several
small images. Such an image is called apposition image because it is
formed by the juxtaposition of small discrete images formed in each
of the ommatidia.
This type of vision is called mosaic vision.

SUPERPOSITION IMAGE
Super position images are formed in nocturnal insects like
cockroach.
In which the retinulae are present deep below the vitrillae and
crystalline cone.
Retinal sheath is absent.
Therefore , the rhabdome and retinulae of an ommatidium
receive not only light rays that enter through its own cornea but
also light rays that enter through the corneas of the adjoining
ommatidia.
This results in the overlapping of images. The image formed by
overlapping of images is called superposition image. It is a blurred
image.

REPRODUCTIVE SYSTEM OF PERIPLANETA
AMERICANA
Periplaneta is diecious, or unisexual .Both
the sexes have well developed reproductive
organs. They show sexual dimorphism both
externally and internally. The female is
different from the male in respective of
short and broad abdomen, presence of
brood pouches and absence of anal styles.

MALE REPRODUCTIVE
SYSTEM
1.The male reproductive system of
periplaneta consists of a pair of testes, a pair
of vasa deferentia, an ejaculatory duct, a pair
of seminal vesicles, a mush room shaped
gland and a phallic gland.
2.A pair of lobed and elongated testes are
present. They are located in the fourth to
sixth segments , one on each side . They are
embedded in the fat bodies.
3.A thin duct called vas deferens begins from
the posterior end of each testis.
4.The two vasa deferentia run backwards and
open into a wide median duct, the ductus
ejaculatorius in the seventh segment.
5.The ejaculatory duct is a muscular tube that
extends posteriorly and opens at the
gonopore or the male genital pore.

.The male genital pore is surrounded by chitinous and
asymmetrical structures called phallic organs or gonapophyses
or phallomeres . They help in copulation . These are the male
external genitalia.
These are the ventral , left and right phallomeres. The male
genital aperture is present at the base of the ventral
phallomere. The left phallomere bears a pseudo penis , a
titillator , a aspirate lobe and inner acculobolus lobe. The
phallic duct opens between acculobous and aspirate lobe. The
right phallomere bears a hook and a serrate lobe.

7.A mushroom shaped gland is present in the sixth and
seventh abdominal segments. It functions as an accessory
reproductive gland. This gland consists of two types of
tubules : They are
A.Long slender tubules, the utriculi majors or
peripheral tubules.Their secretions forms the inner layer of
the spermatophore.
B.Short tubules, the utriculi brevores. Their secretions
nourishes the sperms.
8. A phallic or the conglobate gland is also associated with
the male rproductive system of the periplaneta. Theduct of
this glnad opens near the gonopore. Its function is still not
known.`

FEMALE REPRODUCTIVE
SYSTEM
1.The female
reproductive system of
periplaneta consists of
apairofovaries ,
a pair of oviducts ,
vagina ,
spermathecae ,
spermathecal papilla and
collateral glands.

2.A pair of large ovaries lie laterally in 2-6 abdominal
segments.
They are light yellow in colour surrounded by
fatbodies.Each ovary consists of eight tubules called
ovarian tubules or ovarioles. Each ovariole consists
of a
Tapering anterior anterior filament called germarium
, and
A wide posterior end vitellarium.
The germarium contains various stages of
developing ova , and
The vitellarium contains mature ova with yolk.
The tapering ends of ovarioles of each ovary unite to
form a single thread which attaches to the dorsal
body wall.

the ovarioles , at their posterior end unite to form a short wide
oviduct.
3. The oviducts unite to form a very short median vagina.
4. Vagina opens into a large genital pouch on the eighth sternum
through a vertical opening called female genital pore.
5. Genital pouch is formed by 7th , 8th , and 9th abdominal sterna.
The sternum of the segment is boat shaped and forms the floor and
side walls of the genital pouch.
The sterna of the eighth and ninth segmants constitute the anterior
wall and the roof of the genital pouch , respectively.
The genital pouch has two chambers the anterior Gynatrium or
genital chamber , and the posterior Vestibullum or oothecal chamber.

6. A spermatheca or receptaculum seminis , is present in the
6th segment.It opens by a median aperture on a small
spermathecal papilla in the dorsal wall of the genital pouch on the
ninth sternum.
.
7.Three pairs of plate like chitinous structures called gonapophyses
are present around the female genital aperture. These
gonapophyses guide the ova into ootheca as ovipositors.These are
the female external genitalia.
The eighth sternum bears one pair of gonapophyses called first
basivalvulae. The ninth sternum bears two pairs called valvifers and
second basivalvulae respectively.
8. A pair of branched colleterial glands is present behind the
ovaries. These glands open in to the genital pouch separately , just
above the spermathecal aperture. Secretion of the two collaterial
glands forms a hard egg case called ootheca around the eggs .

7. structural organisation in animals

7. structural organisation in animals

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