Title DIGESTION & ABSORPTION.pdf ✅

 Digital www.allendigital.in [ 3 ] 1. Introduction : • Food is one of the basic requirements of all living organisms. • The major components of our food are carbohydrates, proteins and fats. • Vitamins and minerals are also required in small quantities. • Food provides energy and organic materials for growth and repair of tissues. The water we take in plays an important role in metabolic processes and also prevents dehydration of the body. • Biomacromolecules in food cannot be utilised by our body in their original form. They have to be broken down and converted into simple substances in the digestive system. This process of conversion of complex food substances to simple absorbable forms is called digestion and is carried out by our digestive system by mechanical and biochemical methods. General Organisation of the Human Digestive System Oral cavity Mouth Submaxillary and sublingual glands Liver Gall bladder Duodenum Transverse colon Ascending colon Ileum Caecum Vermiform appendix Parotid gland Pharynx Oesophagus Stomach Pancreas Jejunum Descending colon Anus Rectum Sigmoid colon 01 Digestion and Absorption Fats (lipids) Minerals Water Carbohydrates Proteins Vitamins Food Nutrients Major Components Required in small quantity Prevents dehydration of the body
NEET : Biology [ 4 ] www.allendigital.in  Digital Origin of Alimentary Canal : • The alimentary canal is tubular structure which extends from mouth to anus. • It develops from ectoderm & endoderm. 2. Digestive System : (A) Alimentary canal : • The alimentary canal begins with an anterior opening – the mouth, and it opens out posteriorly through the anus. (1) Mouth and Buccopharyngeal Cavity : • Mouth is a horizontal transverse slit like aperture which is surrounded by upper and lower lip. • The mouth leads to the buccal cavity or oral cavity. (i) Buccal vestibule • The space between the gums and cheeks where the food is stored temporarily. (ii) Oral cavity • The oral cavity has a number of teeth, a muscular tongue and palate. • It is inner & central part which is surrounded by upper and lower jaw. • Lined by non-keratinized stratified squamous epithelium. • Upper Jaw is fixed and lower jaw is movable. Alimentary Canal Mouth Buccal Cavity Pharynx Oesophagus Stomach Small Intestine Anal Canal & Anus Human Digestive System Digestive Glands Gastric Glands Intestinal Glands Associated Glands Salivary Glands Liver Pancreas Large Intestine Ectoderm - upto hard palate Endoderm - from soft palate to rectum Ectoderm - from anal canal to Anus Ectodermal Endodermal Ectodermal Teeth Palate (Roof of oral cavity) Tongue
Digestion and Absorption  Digital www.allendigital.in [ 5 ] (iii) Palate - Roof of buccal cavity is called palate. • Palate is differentiated into two parts: (a) Hard Palate – • It is the anterior part of the palate. • It is made up of maxilla and palatine bone in human. • On the ventral surface of hard palate, some projections or transverse ridges are present which are called palatine rugae. • These rugae prevent slippage of the food from buccal cavity during mastication. • These rugae are well developed in carnivorous animals. (b) Soft Palate – • It is the posterior part of palate. • The posterior outgrowth of soft palate which hangs down in the form of finger like process called as Uvula or Velum palati. • On the dorsal side of uvula one pair internal nasal pores are present. • Uvula covers the opening of internal nasal pores during ingestion of food, so food particle cannot move inside nasal chamber. • One pair of large lymph node is present on the posterolateral surface of soft palate, called as Palatine tonsil or Tonsils. • Soft palate is situated in the pharynx and pharynx is divided into two parts. • Upper part of pharynx is called Nasopharynx which is related to the nasal chamber. • The lower part of pharynx is called Oropharynx which is related to the oral cavity. • One pair of openings of Eustachian tube is present in the nasopharynx. • This Eustachian tube is related to the middle ear : It maintain air pressure. • The oral cavity leads into a short pharynx which serves as a common passage for food and air. (2) Pharynx : • The oesophagus and the trachea (wind pipe) open into the pharynx. • A cartilaginous flap called epiglottis prevents the entry of food into the glottis – opening of the wind pipe – during swallowing. Posterior outgrowth of soft palate hangs down in the form of finger like process called as Uvula (Velum palati) One pair of large lymph nodes are present on the posterolateral surface of soft palate, called as Palatine tonsils. Soft Palate Eustachian tube Nasopharynx Upper part of pharynx Soft palate Uvula Oropharynx Hard palate Oral cavity Teeth Tongue • Related to the middle ear • maintain air pressure • Lower part of pharynx • Related to the oral cavity
NEET : Biology [ 6 ] www.allendigital.in  Digital (3) Tongue : • The tongue is a freely movable muscular organ attached to the floor of the oral cavity by the frenulum. • The upper surface of the tongue has small projections called papillae, some of which bear taste buds. (4) Teeth : • Teeth are ectomesodermal in origin. • In human beings three basic features of teeth are thecodont, diphyodont and heterodont. • Each tooth is embedded in a socket of jaw bone. This type of attachment is called thecodont. • Majority of mammals including human being forms two sets of teeth during their life, a set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont. • An adult human has 32 permanent teeth which are of four different types (Heterodont dentition), namely, incisors (I), canine (C), premolars (PM) and molars(M). • Four types of teeth found in mammals are – Incisors – These are long, chisel like teeth for gnawing the food. Eight in number. Canines – These are sharp pointed teeth meant for tearing and shredding the food. Canines are most developed in carnivorous animals. (Incisors and canines are called smiling teeth.) Pre molars – These teeth are meant for chewing and crushing of food. They are triangular in shape. Molars (Cheek teeth) – These are also meant for chewing & crushing of food. They are rectangular in shape. (Molars and premolars are called cheek teeth.) TONGUE Papilla Lingual Frenulum TONGUE Tooth Socket Anterior part of tongue is free Posterior part of tongue is connected to hyoid bone Incisor Canine Premolars Molars Socket of jaw