Digestion in Humans:
The human digestive system contains alimentary canal and associated glands.
The human digestive system contains alimentary canal and associated glands. Digestive system of man consists of Mouth, Buccal Cavity, Oesophagus, Pharynx, Stomach Duodenum, Small Intestine, Large Intestine (colon), Rectum and Anus.Fig. Human digestive system
Salivary glands are present inside the Buccal Cavity.They secrete saliva. This saliva plays an important role in breaking down complex components like starch,which is further simplified into sugars.
The inner walls of the small intestine have millions of small finger like projections called the Villi. Due to their presence the surface area for digestion as well as absorption of digested food increases by eight times.
The undigested and unabsorbed food then enters the large intestine. The food then travels upward in the ascending colon of the large intestine. The function of the large intestine is to absorb the water and salts from the undigested food material. The undigested semi solid waste that passes into the Rectum is called faeces
It is then removed through the anus at intervals in a process called Egestion.
Digestion in Ruminants:
Cellulose is an important component in the diet of herbivorous animals. It is present in the cell wall of plant cells. Humans cannot digest cellulose. Grass eating animals like the cow, ox, buffalo and sheep swallow the food without chewing. After feeding, they bring the food from the stomach back into the mouth and chew it leisurely. This process is called rumination, and such animals are called ruminants. Fig. Digestive system in cow
Grass eating animals like cows, sheep, buffaloes and goats do not chew their food properly. Instead, they swallow it quickly and store it in the rumen. In the rumen, the digestive juices partially digest the food. The partially digested food in the rumen is called cud.
Partially chewed food is pushed down through the oesophagus into the rumen.
The cud is brought back to the mouth to be chewed properly. The process of chewing cud is called rumination. Rumination is also called second chewing.Animals that partially digest food in the rumen and bring it back to the mouth for additional chewing of the cud are called ruminants.
A large sac-like structure, called the caecum, lies between the small and large intestines.
Ruminants have green plants as their food. These plants contain a type of complex carbohydrate, called cellulose. In the caecum, a kind of symbiotic bacteria helps digest cellulose. In ruminants, a major part of all carbohydrates, including the complex carbohydrates such as cellulose and hemi-cellulose, is digested by bacterial action.
These symbiotic bacteria are not present in the human digestive system. That is why humans cannot digest cellulose.
Digestion in Amoeba:
The amoeba is a microscopic unicellular organism which belongs to the group protozoa. The name comes from the Greek word amoibe, meaning change. The habitat of the amoeba is fresh water. The amoeba contains jelly-like cytoplasm. Inside the cytoplasm are cell organelles like the nucleus, food vacuoles and contractile vacuole. An amoeba takes in oxygen gives off carbon dioxide through the cell membrane by a mechanism of diffusion. It takes in oxygen dissolved in water.An amoeba can move all directions and can change its shape with the help of pseudopodia as a locomotory organ.Fig. Steps involved in digestion in amoeba
An amoeba engulfs its prey along with a droplet of water with the help of pseudopodia, and then forms a food vacuole inside the cytoplasm. The prey can be killed and digested with the help of the digestive juice secreted by the food vacuole. The undigested food is thrown out by changing the shape of the body. Amoeba forms a cyst in unfavorable conditions.
The term amoeba is derived from the Greek word amoibe, meaning change.
The amoeba is one of the simplest, jelly-like animal . the ultimate shape shifter. An amoeba is so minute that it can be seen only under a microscope.
Amoebae are found at the bottom of fresh water bodies like ponds and lakes, even in a gutter or muddy water. Some of them are also found in damp soil and food.
The amoeba is a single-celled animal. The amoeba has a jelly-like substance, called the cytoplasm, inside a flexible boundary called the cell membrane. Floating in the cytoplasm are various structures like the nucleus, food vacuoles and contractile vacuoles.
An amoeba takes in dissolved oxygen from the surrounding water, and gives off carbon dioxide into the water through the cell membrane.
An amoeba can move in all directions using temporary feet-like structures, called pseudopodia. An amoeba, with the help of pseudopodia, captures and engulfs its prey along with a droplet of water.
In an amoeba, digestive juices convert food particles into simpler substances. The cytoplasm absorbs digested food directly, and uses it for growth, maintenance and multiplication.
In the amoeba, undigested remains of food are thrown out of the body. An amoeba roll into a tiny ball called cyst during unfavorable conditions.