Explain the process of human digestive system for 0th
Answers
Answer:
Human digestive system consists of alimentary canal and associated glands.
Alimentary canal begin with anterior opening mouth and opens out posteriorly through anus. It comprises of following parts:--
➡️ Mouth- leads to oral cavity or buccal cavity which contains teeth and tongue.
Upper surface of tongue has small projections called papillae, some of which containtaste buds.Each teeth is embedded in socket of jaw bone (thecodont). Milk teeth is replaced by
permanent or adult teeth, this type of dentition is called diphyodont. Four different types of teeth (Heterodont) are incisors (I), canine (C), premolar (PM) and molar (M).
➡️ Pharynx – oral cavity opens into pharynx which acts as common passage for food and air.Cartilaginous flap called epiglottis prevents the entry of food into wind pipe (glottis)during swallowing.
➡️ Stomach- Oesophagus leads to stomach. The opening of stomach is guarded by asphincter (gastro-oesophageal). Stomach is divided into three parts- cardiac, fundic and pyloric.
➡️ Small intestine- is the longest part of alimentary canal divided into duodenum, jejunum and ileum. Pyloric sphincter is present between stomach and duodenum.
➡️ Large intestine- ileum opens into large intestine, which is divided into caecum, colon and rectum. Caecum is a blind sac which host microbes. Vermiform appendix arises from caecum. Rectum opens through anus.
Explanation:
process of Digestion of food :---
Carbohydrates, fats, proteins and nucleic acids occur in food in the form of large and complex insoluble macromolecules (polymers). These macromolecules are converted into small monomers by the action of enzyme.
➡️ In buccal cavity, teeth and tongue help in mastication and mixing of food.
➡️ Bolus is passed to pharynx and Oesophagus by swallowing or deglutition.
➡️ Chemical digestion of food starts in oral cavity by the action of enzyme salivary amylase and lysozyme.
Lysozyme acts as antibacterial agent in mouth to prevent infection.
Salivary amylase breaksdown starch into maltose
➡️ Mucosa of stomach have gastric glands having three types of cells- neck cells that secrete mucus, peptic or chief cells that secretes proenzyme pepsinogen and pariental or oxyntic cells that secretes HCl.
➡️ Food mixes with gastric juice due to churning action of muscular wall to form chyme.HCl activates the pepsinogen to pepsin to digest protein into peptones and proteoses
➡️ Mucus and bicarbonates present in gastric juice play important role in lubrication and protecting inner wall of stomach from the action of HCl. Renin is a proteolytic enzyme found in gastric juice of infants to digest milk protein.
➡️ The Bile, pancreatic juice and intestinal juice are released in small intestine. Pancreatic juice contain inactive trypsinogen, chymotrypsinogen,
procarboxypeptidases, amylases, lipases and nucleases.
➡️ Trypsinogen is activated by enzyme enterokinase in to trypsin, which further
activates the other enzyme of intestinal juice.
➡️ Bile contains bile pigments (bilirubin and bil-verdin), bile salts, cholesterol and
phospholipids which help in emulsification of fats.
➡️ Secretion of brush border cells of mucosa and goblet cells contain enzyme succusentericus, containing variety of enzymes to complete the process of digestion.