Explore how animals obtain and process food using mind maps. Learn about ingestion, digestion, and absorption in humans, from the mouth to the alimentary canal. Understand unique feeding methods, like rumination in cows and pseudopodia in Amoeba. See how diverse organisms meet their nutrition needs for survival.
Different Ways of Taking Food
- Bees and hummingbirds consume food by sucking nectar.
- Snakes like the python swallow their prey whole.
- Some aquatic animals filter tiny food particles for nutrition.
- In humans, the process of taking food into the body occurs through the mouth and is termed ingestion. After ingestion, the food is mechanically broken down into smaller pieces through chewing with the teeth.
Modes of Feeding in Different Animals
- Snail: Scraping, chewing
- Ant: Chewing
- Eagle: Capturing and swallowing
- Hummingbird: Sucking
- Lice: Sucking
- Mosquito: Sucking
- Butterfly: Siphoning
- House fly: Sponging
DIGESTION IN HUMANS
- Digestion in humans involves the intake, digestion, and utilization of food, with the unused parts being defecated. The process occurs in a continuous canal that starts at the buccal cavity and ends at the anus.
The Alimentary Canal
The alimentary canal, also known as the digestive tract, is divided into several compartments:
- The buccal cavity
- Foodpipe or oesophagus
- Stomach
- Small intestine
- Large intestine ending in the rectum
- The anus
- As food travels through these compartments, it is gradually digested. The inner walls of the stomach and small intestine, along with glands like the salivary glands, liver, and pancreas, secrete digestive juices. These juices convert complex food substances into simpler ones. Together, the digestive tract and associated glands form the digestive system.
Detailed Breakdown of the Digestive System
Mouth and Buccal Cavity
- Food is taken into the body through the mouth, a process called ingestion.
- The food is chewed and broken down mechanically into smaller pieces by the teeth.
- Types of Teeth: Teeth vary in appearance and function, with different types for biting, cutting, piercing, tearing, chewing, and grinding.
- Saliva: The mouth contains salivary glands that secrete saliva, which breaks down starch into sugars.
- Tongue: The tongue mixes saliva with the food during chewing and helps in swallowing. It also has taste buds to detect different tastes.
Foodpipe/Oesophagus
- Swallowed food passes into the oesophagus, which runs along the neck and chest.
- Food is pushed down by the walls of the foodpipe via a movement that occurs throughout the alimentary canal.
- Rejection of Food: At times, the stomach may not accept the food, leading to vomiting.
- Windpipe Protection: The windpipe, which carries air to the lungs, runs adjacent to the foodpipe. A flap-like valve closes the passage of the windpipe during swallowing to prevent food from entering it. If food particles enter the windpipe by accident, it can cause choking, hiccups, or coughing.
Stomach
- The stomach is a thick-walled bag that receives food from the oesophagus and opens into the small intestine.
- Secretions:
- Mucous: Protects the stomach lining.
- Hydrochloric acid: Kills bacteria and makes the medium acidic for digestive juices to act.
- Digestive juices: Break down proteins into simpler substances.
- Function: The stomach churns food and secretes fluids that digest it. The end of the stomach opens into the intestine only after the digestion of the food inside the stomach is completed.
- Historical Observation: The working of the stomach was discovered when a man named Alexis St. Martin was wounded, leaving a hole in his stomach. An army doctor, William Beaumont, used this opportunity to observe the inside of the stomach and its digestive processes.
Small Intestine
- The small intestine is highly coiled and about 7.5 meters long.
- Connections: It receives secretions from the liver and pancreas, and its walls also secrete juices.
- Secretions and Digestion:
- The liver secretes bile juice, stored in the gall bladder, which helps in the digestion of fats.
- The pancreas secretes pancreatic juice, which acts on carbohydrates, fats, and proteins, changing them into simpler forms.
- The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acids.
- Absorption:
- Digested food passes into blood vessels in the intestine walls through a process called absorption.
- The inner walls of the small intestine have villi, which increase the surface area for absorption.
- Absorbed substances are transported to different organs for building complex substances like proteins, a process called assimilation.
- Undigested Food: The food that remains undigested and unabsorbed enters into the large intestine.
Large Intestine
- The large intestine is wider and shorter than the small intestine, about 1.5 meters in length.
- Function: It absorbs water and some salts from undigested food.
- Waste Management: The remaining waste passes into the rectum as semi-solid faeces and is removed through the anus via egestion.
DIGESTION IN GRASS-EATING ANIMALS
- Grass-eating animals, such as cows and buffaloes, are known as ruminants. They exhibit a unique digestive process that allows them to efficiently break down cellulose-rich grass.
Process of Digestion in Ruminants
- Initial Ingestion: Ruminants quickly swallow grass during eating and store it in the rumen, a part of the stomach. They do not properly chew the food at this time.
- Partial Digestion in the Rumen: In the rumen, the food undergoes partial digestion and is then called cud.
- Rumination: Later, the cud returns to the mouth in small lumps, and the animal chews it. This process is called rumination.
- Cellulose Digestion: Grass is rich in cellulose, a type of carbohydrate. Ruminants possess bacteria in the rumen that aid in the digestion of cellulose.
- Caecum: Animals like horses and rabbits have a large sac-like structure called the caecum located between the oesophagus and the small intestine. The cellulose in the food is digested here by the action of certain bacteria which are not present in humans.
FEEDING AND DIGESTION IN AMOEBA
- Amoeba is a microscopic, single-celled organism commonly found in pond water. It lacks a mouth and a digestive system, yet it has a unique method of acquiring and digesting food.
Process of Feeding and Digestion in Amoeba
- Structure: Amoeba consists of a cell membrane, a rounded, dense nucleus, and many small bubble-like vacuoles in its cytoplasm. Amoeba constantly changes its shape and position.
- Pseudopodia: To move and capture food, Amoeba pushes out one or more finger-like projections called pseudopodia, also known as false feet.
- Food Capture: When Amoeba senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole.
- Digestion: Digestive juices are secreted into the food vacuole, where they act on the food and break it down into simpler substances.
- Absorption: Gradually, the digested food is absorbed.
- Assimilation: The absorbed substances are utilized for growth, maintenance, and multiplication.
- Egestion: The undigested residue of the food is expelled outside by the vacuole.
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