Digestive System or Alimentary System Canal
Type of Alimentary system
The alimentary system a collection of organs which perform the function of digestion of food in various animal, there are different type of alimentary in various animals
- 1. Alimentary canal in lower Animals
Planaria – Flat worm
The planaria are free living flat worms which feed on small microorganisms. They have a simple gut with a single opening leading to the outside i.e the mouth which is situated on the ventral side of the flat body . The mouth opens into a large muscular pharynx that can be averted suddenly to catch their prey . During feeding, the food is sucked into the gut by means of suctorial pharynx. The gut has three branches one leading toward the anterior and the other two towards the posterior. The three main branches give out many fine branches. Digestion is partly extracellular and partly intercellular. The branches gut makes the absorption and digestion efficient, the undigested food is thrown out of the anus.
Digestion in earthworm
The earthworm feed mainly on vegetable materials which it swallows as it burrows into the soil . The straight gut is a tube with mouth at the anterior end and anus at the posterior end . The mouth opens into a walled
Buccal cavity into which the food is moistened secrete mucus that by a thick muscular pharynx which secrete mucus that lubricates the food . The pharynx opens into a narrow thin crop in which food is stored for a short time . From the crop, the food is released into a walled muscular gizzard in which there are small stones which help to grind the food this is followed by a long straight intestine in which digestion take place . Digestion in earth worm is purely intracellular and the digested food diffuses through the intestinal wall into the surrounding blood capillaries . The blood them carries the soluble food to all parts of boy
ALIMENTARY CANAL OF INSECT
The alimentary canal of insect e.g cockroach consists of three main parts ,the fore gut, the mid gut and the hind gut .The Fore gut is made up of the mouth, buccal cavity ,pharynx, crop and gizzard. The mid gut or the stomach while the hind gut is composed of the intestine and annus. At the junction of the fore gut and mid gut is a finger- like projection called gastric caecum . These secrete digestive juice into the mid gut where digestion take place.
Absorption of digested food takes places in the anterior part of the hind gut. Between the mid gut and the hind gut are numerous tubules called Malpighian tubules which absorb waste material from the body fluid and deposit them in the hind gut. The hind gut consist of ileum, colon and rectum which absorbs water and mineral salt. The faeces are later passed out through the anus.
Alimentary canal of insect (cockroach)
ALIMENTARY CANAL OF A BIRD
The digestive system of bird include the beak, mouth, pharynx, oesophagus, crop, proventriculus, gizzard, intestine, caecum, rectum and anus or cloaca. The bird uses the beak to pick up food which passes through the mouth, oesophagus and the crop where the food is temporarily stored, moistened and fermented by some bacteria. The food is now passed down to the proventriculus where enzymes are secreted on the food,. proventriculus is often regarded as glandular stomach because it has glands which secrete digestive enzymes e.g pepsin, amylase e.t.c on the food.
From the proventriculus the food moves to the gizzard where the natural grinding of the food takes places with the aid of small stones or grift with which the food is ground by the gizzard. From the gizzard the food moves to the duodenum and the intestine where further digestion and absorption of the food take place. The undigested food particles are moved through the caecum to the rectum and finally to the anus.
Differences Between Alimentary Canal Of Bird And Cockroach
|I.||There is presence of tongue in the mouth.||Tongue is absent.|
|II.||Mouth is modified into beak.||Mouth is modified into mandible and maxillae for chewing and grinding.|
|III.||There is presence of duodenum.||Duodenum is not present.|
|IV.||It has long alimentary.||It has relatively short alimentary canal.|
|V.||The hind gut ends in cloaca.||Hind gut ends in anus distinct from the reproductive tract.|
|VI.||Malphighian tubules are absent.||Malphighian tubules are attached to aliment canal.|
|VII.||There is presence of pancreas.||Pancreas is absent.|
Similarities Between Alimentary Canal of A Bird And Cockroach
- Both have narrow esophagus.
- Crop is present in both organisms
- Muscular gizzard is present in both.
- There is the presence of a caecum in both
- Mid-gut is present in both organisms.
ALIMENTARY CANAL OF RABBIT.
The alimentary canal of rabbit consist of the teeth, mouth, salivary gland, oesophagus, stomach, small intestine, caecum, appendix and large intestine. Rabbit is a herbivorous animal, herbivores are adapted for cropping grasses and grinding plant matter to break down the cellulose cell wall.
The incisors of rabbit are long and chisel shaped. They bite against each other to chop of pieces of grasses. The incisors wears away fast but the teeth can grow continuously because of a good supply of blood into the pulp cavity. There are no canines in herbivores, instead between the incisors and premolar, there is a gap called diastema which help to push the food from the front of the mouth to the grinding teeth behind. The rabbit has a large caecum and appendixes which contain numerous bacteria capable of breaking down cellulose into sugar and the rest is absorbed by the herbivore.
ALIMENTARY CANAL OF MAN
The alimentary canal of man is a tube of varying diameter running form the mouth to the anus. The canal include mouth, esophagus, stomach, small intestine or ileum, caecum, large intestine or colon and anus. Along the length of the canal, there are sections adapted to deal with various stages of nutrition and egestion.
Ingestion is the taking in of solid food by the organism through the mouth. The mouth contains the teeth, salivary gland and tongue. The teeth are used to break and grind food mechanically into tiny particles while the tongues rolls the food into bolus. It allows mixing of food with saliva which contains enzyme ptyalin which breaks down starch into maltose which is later swallowed into the gullet in form of bolus. The esophagus connects the mouth to the stomach. The food swallowed is passed down through the esophagus by peristaltic movement into the stomach.
Digestion: It is defined as an enzymatic break down of food substances into simple and absorbable form. These commences in the stomach which store the food temporarily for few hours. The food is now released at regular interval by the opening of PYLORIC SPHINCTER In the stomach, The gastric gland secret gastric juice which contain two enzymes: rennin and pepsin. The renin acts on liquid protein e.g milk or it helps to curdle milk while the pepsin break down the protein to peptone. The gastric gland also secretes hydrochloric anus ( HCL) which creates acid medium for the enzymes to act and also to kill some bacteria contained in the food. The food is churned by muscular contraction of the stomach wall which enable the mixing of the food with digestive juice. The churning movement then convert the food into a semi- liquid state called chyme.The food ( CHYME) is passed down by peristalsis to the first part of small intestine called duodenum where the pancreas secrete pancreatic Juice that contain the following
- Amylase: This enzyme covert starch to maltose
- Lipase: it converts fat and oil to fatty and glycerol
- Trypsin: This enzyme converts protein and peptone to polypeptides
The pancreatic Juice is alkaline and provide the medium for the enzymes mentioned above to act. The digestion of fat and oil is carried out by the green pigment called bile produce in gall bladder which is situated in the liver. The bile is used for the emulsification of fact and oil i. e breaking down fat and oil molecules into tiny droplet before enzyme lipase acts on them
The small intestine or ileum is found between the duodenum and large intestine. The major event that take place there are:
- Completion of digestion
- Absorption of digested food
The intestinal wall of ileum secrete intestinal Juice which contain the following enzymes
- Enzyme lipase
The LIPASE converts fat and oil to fatty and glycerol, erepsin convert polypeptide to amino and , Maltase convert maltose to two units of glucose, sucrase convert sucrose to glucose and fructose, while lactase convert lactose sugar to glucose and galactose.
Absorption is define as the passage of soluble digested food substances into the blood stream or body fluid through the wall of the ileum called villi, : The end product of digestion such as amino acid , glucose , fatty and glycerol are absorbed in the small intestine by tiny finger- like structure called villi : A villus is made up of inner surface or epithelium ,. blood capillaries and lacteal .. The inner surface of each villus is thin which allows the absorption of the end products either by diffusion or active transport through it . The glucose and amino acid are absorbed by blood capillaries through the epithelium into the blood stream wile the fatty and glycerol enter the lacteal where they are carried to the lymph vessels which eventually empties their content in to the blood vessels near the heart
Caecum or appendix has no specific function but the caecum contain some bacteria which and mine digestive of cellulose. Some vitamins especially K&B complex are partially synthesized in this region egestion :it is the discharge of the insoluble absorbable and undigested food particles passes through the anus . the indigested food particles passes through the colon or large intestine and water is aborted back into the blood stream .the absorption of water concentration the waste product and make them into faces which are passes out through the aims
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