5. PERIPLANETA AMERICANA (COCKROACH)
Digestive system of Periplaneta
Alimentary canal Digestive glands
Alimentary canal
Foregut / Stomodaeum
Midgut /Mesenteron
Hind gut / Proctodaeum
7. PERIPLANETA AMERICANA (COCKROACH)
It is a long tube and is coiled at some places.
It extends between the mouth and the anus.
It is divided into three regions:
Foregut / Stomodaeum
Midgut /Mesenteron
Hind gut / Proctodaeum
Alimentary canal
9. PERIPLANETA AMERICANA (COCKROACH)
Helps in ingestion of food materials.
Then food enters the mouth from preoral cavity.
Food is crushed by mandibles and mixed with saliva.
mouth pharynx
MOUTH
Food enters
12. PERIPLANETA AMERICANA (COCKROACH)
The crop serves as a reservoir for storing food.
Crop
It is pear shaped.
The outer surface is covered by a network of
tracheae.
14. PERIPLANETA AMERICANA (COCKROACH)
Internal structure of gizzard
The chitinous inner lining of the gizzard has six powerful teeth, which
forms an efficient grinding apparatus.
Behind each tooth, there is a hairy pad, which bears backwardly directed
bristles.
Among these plates,
food is thoroughly
ground into fine
particles.
These food particles
are filtered by the
bristles.
15. PERIPLANETA AMERICANA (COCKROACH)
There is a membranous projection of the gizzard into the mesenteron in
the form of a funnel called stomodeal valve.
The gizzard acts as both grinding mill and as a sieve.
This valve prevents the entry (regurgitation) of food from the
mesenteron back into the gizzard.
16. PERIPLANETA AMERICANA (COCKROACH)
It is a short and narrow tube behind the gizzard.
Between the ventriculus and the gizzard there are six to eight finger
like diverticula called hepatic caecae present.
Midgut / Mesenteron / Ventriculus
The mesenteron is lined by the endodermal cells.
18. PERIPLANETA AMERICANA (COCKROACH)
It has many gland cells and secretes several
enzymes.
Secretory part (Anterior) Midgut
It (peritrophic membrane) is a network of chitin
fibrils in a glycoprotein matrix secreted by cells
in the anterior region of the midgut.
The bolus of food in the mesenteron is enveloped
by a chitinous and porous membrane called
peritrophic membrane.
19. PERIPLANETA AMERICANA (COCKROACH)
Secretory part (Anterior) Midgut
Digested food is absorbed into the blood through
the peritrophic membrane in the posterior
absorptive region of the ventriculus.
It protects the wall of the ventriculus from hard
particles of food.
20. PERIPLANETA AMERICANA (COCKROACH)
Digested food is absorbed into the blood by absorptive region of
midgut.
The opening of the ventriculus into the hindgut is controlled by a
sphincter muscle.
The function of sphincter muscle is prevention of entry of undigested
food and uric acid from the hindgut into the midgut.
Absorptive part (posterior) of midgut
21. PERIPLANETA AMERICANA (COCKROACH)
Hindgut / Proctodaeum
It is a long coiled tube.
It consists of three regions.
Ileum
Colon
Rectum
It is internally lined by chitinous cuticle.
22. PERIPLANETA AMERICANA (COCKROACH)
The ileum that lies behind the mesenteron is a short tube.
Six bundles of fine yellow blind tubules called Malpighian tubules.
23. PERIPLANETA AMERICANA (COCKROACH)
Malpighian tubules are excretory in function.
Ileum opens into a long coiled tube called colon.
Colon leads into a short and wide rectum, which
opens out through the anus.
Rectum bears on its inner side six longitudinal
folds called rectal papillae.
The function of rectal papillae is reabsorption of
water from the undigested food.
30. PERIPLANETA AMERICANA (COCKROACH)
Acini / lobules
Common salivary duct
Median salivary duct
Salivary receptacle
Receptacular duct / reservoir
duct
Efferent salivary duct
Salivary glands and other structures
31. PERIPLANETA AMERICANA (COCKROACH)
There is a pair of salivary glands attached to the ventro lateral sides of
crop, one on each side.
Salivary glands and other structures
Each salivary gland has two lobes.
Each lobe of salivary gland has many lobules called acini.
Each acinus is a group of secretory cells called zymogen cells with a
small ductule.
32. PERIPLANETA AMERICANA (COCKROACH)
The ductules of both the lobes of salivary gland unite to form a
common salivary duct on each side.
Salivary glands and other structures
The two common salivary ducts are jointed to form the median
salivary duct.
Between the lobes of salivary gland of each side is a sac called salivary
receptacle that stores saliva and leads into receptacular duct or
reservoir duct.
33. PERIPLANETA AMERICANA (COCKROACH)
The receptacular ducts of both sides are united to form a common
receptacular duct or common reservior duct.
Salivary glands and other structures
The median salivary duct opens into common receptacular duct .
Later these two form an efferent salivary duct that opens at the base
of hypopharynx.
The efferent salivary duct opens at the base of the hypopharynx.
Acinar cells secrete saliva which contains starch digesting enzymes such
as amylase.
34. PERIPLANETA AMERICANA (COCKROACH)
Acini Common salivary duct
Median salivary duct Salivary receptacle (stores saliva)
Receptucular duct
or
Common reservoir duct
Efferent salivary duct
PROCESS OF SECRETION AND FLOW OF SALIVA
35. PERIPLANETA AMERICANA (COCKROACH)
The hepatic caecae are also termed ‘midgut’ caecae. They contain
secretory and absorptive cells.
They secrete enzymes such as maltase, invertase, proteases and
lipase.
Hepatic caecae
Glandular cells of the mesenteron
40. PERIPLANETA AMERICANA (COCKROACH)
It locates the food by the olfactory sensillae of antennae, labial palps
and maxillary palps.
The food is seized with the help of forelegs, labrum and labium.
It is passed to the mandibles for biting and chewing.
The laciniae, galeae, glossae and paraglossae hold the food during
chewing.
Glossa
Paraglossa
2nd Maxilla
or labium
Mentum
Submentum
Labial palp
The labrum and labium prevent the food- from falling down.
Labrum
Labium
The food is mixed with saliva during mastication.
41. PERIPLANETA AMERICANA (COCKROACH)
Digestion
After swallowing, the food passes through
the pharynx and oesophagus and reaches
the crop.
In the crop, food is mixed with digestive
juices that are reguritated into it through
the grooves of the gizzard.
42. PERIPLANETA AMERICANA (COCKROACH)
Hence, most of the food is digested in the
crop.
The partly digested food is filtered by the
bristles of the gizzard and later it passes
through the stomodeal valve into the
ventriculus.
The enzyme amylase of the salivary juice
converts starches into disaccharides.
43. PERIPLANETA AMERICANA (COCKROACH)
Action of Enzymes on Food taken by Periplaneta americana
Invertase
Sucrose Glucose and
Fructose
or
Sucrase
Salivary Amylase
Disaccharides
Starch
45. PERIPLANETA AMERICANA (COCKROACH)
In the ventriculus, the digested food is
absorbed.
The undigested food is passed into ileum,
colon and then reaches the rectum, where
water is reabsorbed by rectal papillae.
Then, the remaining material is finally
defaecated as dry pellets through the
anus.
46. PERIPLANETA AMERICANA (COCKROACH)
The crop of Periplaneta
does not secrete any
digestive enzymes, but
most of the food is
digested in it. Explain how
is it possible ?
Though crop does not
secrete any digestive
enzymes,
partial digestion occurs in it
due to regurgitation of
midgut enzymes into the
crop through the grooves of
the gizzard.
