This ppt explains about general digestive system and nervous system of invertebrates by taking model organism as cockroach

1. Digestive System and Nervous
System of Invertebrate

2. Introduction to Cockroach
• Cockroach (P. americana) belongs to the class
Insecta of Phylum Arthropoda. It is a common
nocturnal omnivorous household animal
which acts as a scavenger. It prefers dark
warm corners of kitchens, underground drains
and places where food and humid atmosphere
are available.

3. Feeding and Digestion in Cockroach
• Cockroaches have adopted themselves to all
types and sizes of diet. To handle the various
types of food all the appendages of cockroach act
synchronously.
• Extracellular digestion is the characteristic like
other developed animals. Digestion starts from
the buccal cavity containing the mouth parts. The
food is then subjected to a variety of biochemical
reaction within a specialized digestive system.

5. Digestive System of Cockroach
• The digestive system, which is responsible for
digestion and absorption of food materials,
includes digestive canal or tract (also called
alimentary canal) and digestive glands.
• The tract is about 6.7 cm in length. It is
divisible into three distinct regions:
• (i) Fore Gut
• (ii) Mid Gut
• (iii) Hind Gut

6. Fore Gut
• It is also known as stomodaeum. It is lined
internally by cuticle and includes the mouth,
pharynx, oesophagus, crop and gizzard.
• The mouth denotes the beginning of the
alimentary canal. This aperture leads to a
small chamber called the buccal cavity
between the mandibles and maxillae on
either side. The labrum serves as upper lip
and labium acts as lower lip.

7. • A short tongue or hypo-pharynx is present on
the floor of the buccal cavity. The buccal cavity
opens into a short pharynx which is a small
tube. The salivary duct opens within the
pharynx near the base of hypo-pharynx. The
pharynx leads into the next part of the fore
gut, which is called the oesophagus

8. • The oesophagus extends up to the prothorax
and is followed by the crop. The dilated sac-
like crop constitutes the largest part of the
fore gut. The wall of the crop is composed of
epithelial layer, circular and longitudinal
muscle layers. The crop extends within the
abdominal cavity and acts as a temporary
reservoir of food, where ingested food may be
retained for two months.

9. • The crop leads into a short thick-walled gizzard, which
forms the last part of the fore gut. It is divided into an
anterior and a posterior part. The wall of the gizzard is
highly muscular and its anterior part contains in its
inner wall six chitinous teeth extending towards the
cavity of the gizzard.
• The posterior part of the gizzard possesses two circular
hairy cushions. The teeth are used for crushing the
food and the hairy cushions work as sieve to permit
only the finer particles of food to go inside the mid gut.

10. Mid Gut
• This undivided part of alimentary canal is also known
as mesenteron. It is a slender tube having an internal
lining of columnar epithelium. Near the junction of the
fore and mid gut, there are eight hollow slender tubes
called hepatic caeca or digestive diverticula.
• All the caeca opens within the mid gut and are believed
to produce digestive juices. In the inner wall, the
epithelial cells throw fine filaments within the lumen of
mid gut. The junction of the mid and hind gut is
marked externally by the presence of numerous
yellowish threads called Malpighian tubules which are
excretory organs and range between 100-150

11. Hind Gut
• It is divisible into following parts —ileum, colon, rectum
and anus. The ileum is the first part of the hind gut and has
small narrow lumen having epithelial lining. The ileum
leads to colon, which is broad and slightly coiled.
• The inner lining of colon is thrown into irregular folds and is
formed by slender epithelial cells having a chitinous
covering. The colon continues into a small sac-like rectum.
The inner wall of the rectum is raised in the form of
papillae.
• Special kinds of glands called rectal glands are present in
the rectal wall for absorbing water. Thus the rectum not
only stores the residual parts of the food but also helps in
osmoregulation. The rectum opens to the exterior through
an opening called the anus. The anus is provided with a
sphincter muscle.

12. Digestion Procedure in Cockroach
• Within the buccal cavity, the food comes in
contact with saliva and passes through the
oesophagus into the crop. Both peristalsis and
antiperistalsis take place in the crop. The passage
of food from the crop to the gizzard depends
upon the ingested fluid.
• From the crop, the food passes to the gizzard,
where the cuticular teeth crushes the food and
the hairy cushion permits only finer particles to
enter the mid gut.

13. • The lining of mid gut and hepatic caeca act both as
secretory and absorptive areas. Following enzymes are
present in the secretion of these regions—amylase,
maltase, invertase, lactase, β-glucosidase, protease and
lipase.
• The cellulase obtained in the mid gut is synthesised by the
micro-organisms residing there. Most of the digested foods
are absorbed only in the mid gut. Glucose is absorbed by
the caeca.
• After the absorption of digested food, the rest passes
within the hind gut, where water and salts are absorbed.
Residual matter is temporarily stored in the rectum and are
periodically rejected through the anusFood requires nearly
33 hours to travel the entire length of the alimentary canal.

15. Nervous System of Cockroach
• The cockroach nervous system consists of CNS, PNS
and sympathetic nervous system where CNS stands for
the central nervous system and PNS stands for the
peripheral nervous system. The cockroach nervous
system is a series of fused segment ganglia that is
connected to the ventral side with longitudinal
connectors.
• The nervous system of cockroaches spreads
throughout the body. Three ganglia in the thorax and
six ganglia in the abdominal segments. In the head, a
bit of the nervous system is present where the
remaining part is located on the ventral side or belly
side of the body.

16. Central nervous system
• The central nervous system consists of the supra-
oesophageal ganglion or brain, sub- oesophageal ganglion,
circum oesophageal commissure and the nerve cord.
• The supra-oesophageal ganglion or is a bilobed structure
situated in the head in front of oesophagus. It is formed by
the fusion of three pairs of ganglia. It represents the brain
and is concerned chiefly with sensory function.
• From the supra-oesophageal ganglia arise two
circumoesophageal connectives which encircle round the
oesophagus and meet below it with the sub-oesophageal
ganglion. The sub-oesophageal ganglion is also situated in
the head and formed by the fusion of 3 pairs of ganglia. The
sub-oesophageal ganglion is the principal motor centre and
controls the movements of muscles, mouth parts, wings
and legs.

17. • Thus, the supra-oesophageal ganglion,
circumoesophageal connectives and sub- oesophageal
ganglion together constitute the nerve ring round the
oesophagus in the head capsule.
• From the sub-oesophageal ganglion arises a double
nerve cord which travels through the thorax and
abdomen below the alimentary canal on the ventral
side up to the posterior end of the body. The nerve
cord has three large ganglia in the thorax, one each for
pro-, meso- and metathoracic segments, therefore,
they are called prothoracic, mesothoracic and
metathoracic ganglia.
• Further the nerve cord has six ganglia in the abdomen
which lie in the 1st, 2nd, 3rd, 4th, 5th and 7th
segments.

18. • Each ganglion of the nerve cord is formed by
the fusion of two ganglia except the ganglion
in the 7th segment. The ganglion in the 7th
abdominal segment is the largest of all the
abdominal ganglia and probably formed by
the fusion of 3 pairs of ganglia.
• Commissure – these are transverse fibers that
unite the pair of ganglia of the system.

19. Peripheral nervous system
• The nerves originating from the nerve ring and ventral
nerve cord to innervate different parts of the body
constitute the peripheral nervous system.
• Three pairs of nerves originate from the supra-
oesophageal ganglion—optic, antennary and
labrofrontal nerves. The first two innervate the eyes
and antennae but the third one divides into labral
nerve supplying to the labrum and the frontal nerve
which runs forwards to join the sympathetic nervous
system.
• Similarly, three pairs of nerves originate from the sub-
oesophageal ganglion—mandibular, maxillary and
labial to innervate the mandibles, maxillae and labium
respectively.

20. • Several pairs of nerves arise from each thoracic
ganglion to supply the different parts of their own
segment.
• A pair of nerves, however, from metathoracic ganglion
innervates the 1st abdominal segment. The nerves
originating from first five abdominal ganglia innervate
the 2nd, 3rd, 4th, 5th and 6th abdominal segments.
From the last abdominal ganglion three pairs of nerves
are given off to supply the 7th, 8th, and 9th segments.
It also gives a branch to innervate the cercus and other
associated structures.

21. Sympathetic nervous system
• The autonomic nervous system or sympathetic nervous
system or visceral nervous system consists of the same
ganglia and their connectives. It includes the frontal,
esophageal, occipital (hypo cerebral), visceral or ingluvial
and pre-ventricular ganglia. The nerves from these ganglia
are connected with the supra-oesophageal ganglion.
• The frontal ganglion is a small ganglion situated on the
oesophagus in front of the supra-oesophageal ganglion. A
pair of frontal connectives from the frontal ganglion is
connected with the supra-oesophageal ganglion
• A median recurrent nerve passes backward from it and
connects the occipital or hypo cerebral ganglion behind the
supra-oesophageal ganglion.
• Oesophageal ganglion located on the dorsal side of the
esophagus and a huge visceral ganglion on the dorsal
surface crop are present.
• Pre-ventricular ganglion is situated on the gizzard

23. Male reproductive system
• A well-developed reproductive system is present. The
male reproductive system consists of a pair of testes,
vas deferens, utricular gland, ejaculatory duct, and
phallic gland.
• Testis: A pair of trilobed testis present in the male
reproductive system which is inside of the fourth to
sixth abdominal segment. One in each.
• Vas-deferens: vas deferens arise from each testis and
pass down to connect seminal vesicles. This opens into
the ejaculatory duct.
• Seminal vesicles: A seminal vesicle is formed when the
vas-deferens dilates; it contains many white sacs,
which are used for storing sperms. Sperms are then
glued together to form spermatophores.

24. • Ejaculatory duct: Ejaculatory ducts arise from the two
seminal vesicles; during copulation or meeting,
spermatophores move down these ducts and open to
the outside through the genital pore situated ventral to
the anus.
• Phallic gland: It is a club shaped gland present below
ejaculatory duct and it secretes the outer layer of
spermatophore
• Mushroom gland/Utricular gland: The seminal vesicles
bear a number of finger-like projections forming
characteristic mushroom-shaped glands in the 6th to
7th abdominal segments, which nourish the sperms
with their secretions.

25. • Genital pouch: Genital pouch is located at the
end of the abdomen. It contains the genital
pore, dorsal anus, and gonapophysis.
• External genitalia: The external genitalia is
represented by an asymmetrical chitinous
structure called the male gonapophysis or
phallomere (right, left and ventral), which
surrounds the male gonophore (genital pore).

27. Female reproductive system
• The female reproductive system consists of the
following parts: a pair of ovaries, oviduct, genital
chamber, vagina, and colleterial glands, spermatheca,
and external genitalia.
• Ovaries – In females, the female reproductive system
consists of a pair of ovaries that are located between
the 2nd and 6th abdominal segments. Each ovary
contains a row of ova in various stages of development
within a group of ovarian tubules.
• Oviduct and vagina – An oviduct leads from the ovary
to the genital cavity. The right and left oviducts form a
single median oviduct, also called the vagina, which is
connected to the genital chamber.

28. • Spermatheca – A pair of spermatheca located in the
sixth segment opens into the genital chamber, and it
stores sperm. The left spermatheca is larger and
functional, and the right spermatheca is smaller and
non-functional.
• Genital pouch or chamber – A genital pouch is a boat-
shaped structure surrounded by three pairs of
chitinous plates supporting copulation and the
deposition of the egg. It is formed by the 7th, 8th, and
9th abdominal segments. It has two chambers. Genital
atrium smaller chamber opening for the collateral
gland, spermatheca, and opening of the common
oviduct. Vestibulum is known as the large posterior
part.

29. • Collateral gland – these glands are present on
either side of a genital chamber into which
they open. They help in the formation of egg
cases or ootheca. The ootheca is a dark
reddish to the blackish brown capsule which is
of 8mm size. They are dropped to a suitable
surface which is usually in a crevice nine to ten
ootheca are present each containing 14-16
eggs.