Notes And Study Material for Exam Papers

The Pancreas lies ventral to the stomach and has both endocrime and exocrime function. Exocrime cells in the pancreas secrete digestive enzymes into pancreatic duct, which merges with hepatic duct from the liver to form common bile duct that enters the duodenum. Pancreatic enzymes complete the digestion of carbohydrates and proteins and initiate the digestion of lipids. Trypsin, carboxypeptidaze and chymotrypsin digest protein into smaller peptide and amino acids. Lipases convert triglycerides into smaller glycerol and free fatty acids. Amylase converts polysaccharides into disaccharides and monosaccharides. The pancreas also secretes bicarbonate (HCO-3) ions that help neutralize the acidic food residue coming from the stomach. Bicarbonate raises the pH from 2 to 7 for pancreatic enzymes to work. Liver and gall bladder: The liver, the largest organ in mammalian body is just under the diaphragm. In the liver millions of specialized cells called hepatocytes take up nutr...

Small intestine: Human small intestine is about 4 cm in diameter and 7 to 8 meter in length. It is intermediate in length between small intestines of typical carnivores and herbivores of similar size. It reflects the human’s omnivorous eating habits. The length of small intestine directly releases to the total surface area available for absorbing nutrients as determined by many circular folds and minute projections of the inner gut surface on the circular folds, thousands of finger like projections called villi project from each square centimetre of mucosa.  These minute projections are so dense that the inner wall of human small intestine has total surface area of approximately 300 mm 2 – the size of a tennis court. First part of small intestine called duodenum functions primarily in digestion. Next part is jejunum and the last part is ileum. Both function in nutrient absorption. The duodenum contains many digestive enzymes that intestinal glands in the duodenal mucosa se...

Oral cavity: A pair of lips projects the oral cavity (mouth). The lips are lightly vascularized, skeletal muscle tissue with an abundance of sensory nerve endings. Lips help retain food as it is being chewed and play a role in phonation (the modification of sound). The oral cavity contains tongue and teeth. Mammals can mechanically process a wide range of food because their teeth are covered with enamel (hardest material in the body) and because their jaws and teeth exert a strong force. The oral cavity is continuously bathed by saliva secreted by three pairs of salivary glands. Saliva moistens food, binds it with nucius (glycoproteins) and forms moist mass called bolus. Saliva also contains bicarbonate ions (HCO 3- ) which buffer chemicals in mouth and thiocynate ions (SCN - ) and the enzyme lysozyme, which kill micro-organisms. It also contributes enzyme (amylase) necessary for initiation of carbohydrate digestion. Pharynx and esophagus: Air and swallowed foods and liquids ...

Caeca: Macro-organisms attack the food of ruminants before gastric digestion but in the typical non ruminant herbivore, microbial action on cellulose occurs after digestion. Rabbits, horses and rats digest cellulose by maintaining a population of micro-organisms in their usually large caecum, adding to this efficiency, a few non ruminant herbivores such as mice and rabbits, eat some of their own faeces to process the remaining material in them like vitamins. Pancreas: Every vertebrate has Pancreas. In lampreys and lung fishes it is embedded in the wall of intestine and is not a visible organ. Both endocrime and exocrime tissues are present but the cell composition varies. Pancreatic fluid containing many enzymes empties into the small intestine viz the pancreatic duct. Intestines: The configuration and divisions of small and large intestine vary greatly among vertebrates. Intestines are closely related to animals’ type of food, body size and levels of activity e.g. cy...

Tongue: A tongue develops in the floor of oral cavity in many vertebrates e.g. lamprey has a prototractible tongue with horny teeth that rasp its prey flesh. Fishes may have a non-muscular tongue that bears teeth that help hold prey. Tetrapods have evolved mobile tongues for gathering food. Frogs and salamanders and some lizards can rapidly project part of their tongue from the mouth to capture an insect. A wood pecker has a long spiny tongue for gathering insects and grubs. Ant and termite eating mammals also gather food with long, sticky tongues, spiny papillae on the tongues of cats and other carnivores help these animals rasp flesh from a bone. Salivary glands: Most fishes lack salivary glands in the head region. Lampreys are an exception because they have a pair of glands that secrete an anticoagulant needed to keep their preys blood flowing as they feed. Modified salivary glands of some snakes produce venom that is injected through fangs to immobilize prey. In amphibi...

Intracellular digestion: In simple animals (protitsts and sponges) some cells take in whole food particles directly from the environment by diffusion, active transport and endocytosis and break them down with enzymes to obtain nutrients. It is called intracellular (within the cell) digestion. It circumstances the need for the mechanical breakdown of food or for a gut or other cavity in which to chemically digest food. It limits animal’s size and complexity only very small pieces of food can be used. It provides all or some of the nutrients in protozoa, sponges, cnidarians, platyheliminthes, rotifers, bivalve molluscs and primitive chordates. Extra cellular digestion: Larger animals have evolved structures and mechanisms for extra cellular digestion; the enzymatic breakdown of larger pieces of food into small molecules usually in special organ or cavity. Digested food then passes into body cells lining the organ or cavity and can take part in energy metabolism or biosynthesis....

Macronutrients: With a few exceptions, heterotrophs require organic molecules such as carbohydrates, lipids and proteins in their diets. Enzymes breakdown these molecules into components that can be used for energy production or as sources for the “binding blocks” of life. Carbohydrates: Carbon and energy from sugars and starches. The main dietary source of energy for heterotrophs is carbohydrates. Most carbohydrates come from plant sources. Various sugars (mosachharides) can meet this dietary need. Carbohydrates also are a major carbon source for use in organic compounds. Many plants also supply cellulose (polysaccharide) that human and other animals (except herbivores) cannot digest. Cellulose is called dietary fibre. It assists in the passage of food through the alimentary canal of mammals. Cellulose may also reduce the risk of cancer of the colon, because the mutogen and reduced if faecal elimination is more frequent. Lipids: Highly compact energy – storage nutrients. N...

Protozoa: Protozoa may be autotrophic, saprozoic or heterotrophic (ingest food pasticles). Ciliated Protozoa are good example for protests that utilize heterotrophic nutrition. Ciliary action directs food from the environment into the buccal cavity and cytostome. The cytostome opens into cytopharynx which enlarges as food enters and pinches off food containing vacuole. The detached food vacuole then moves through the cytoplasm. During this movement excess water is removed from the vacuole; the contents are acidified and then made alkaline and a lysosome adds digestive enzymes. The food particles are then digested within the vacuole and the nutrients are absorbed into the cytoplasm. The residual vacuole excretes its waste products via cytopyge. Bivalve Molluscs: Many bivalve molluscs feed and ingest small food particles. The digestive tract has a short oesophagus opening into stomach, midgut and hindgut. The stomach contains a crystalline style gastric shield and diverticulate...

Antigens: A recognition system allows the mammalian immune system to distinguish ‘self’ from ‘non self’. Prior to birth, the body inventories the proteins and various other large molecules present in the body (“self”) and inactivates most of the genetic programming for making antibodies to self molecules. The body can distinguish self molecules from foreign non self substances and lymphocytes can produce specific immunological reactions against the foreign material leading to its removal. Foreign (“non self”) substances to which lymphocytes respond are called antigens (antibody generator). Most antigens are large proteins or other complex molecules with a molecular weight generally greater than 10,000. Antibodies: Plasma cells manufacture antibodies (immunoglobulins) a group of recognition glycoproteins present in the blood and tissue fluids of birds and mammals. All antibody molecules have a basic Y structure composed of four chains of polypeptides connected by disulph...

It consists of paired lungs and air passage ways. Lungs lie in thoracic cavity walls of which are formed of intercostals muscles attached with bony cage formed by 12 pairs of ribs, vertebral column and sternum bone. Thoracic cavity is separated from abdomen by a muscular partition called diaphragm. Air enters into lungs by a pair of openings called external nares or nostrils which lead into pharynx. Pharynx leads air into larynx by opening called glottis guarded by flap of tissue called epiglottis. Larynx leads air into trachea. Trachea leads into two bronchi. Each bronchus leads into each lung and subdivides into bronchioles. Each bronchiole ends into alveoli or air sacs. Alveoli are respiratory surfaces of lungs. In alveoli exchange of gases takes place. Breathing: It is the process of taking in (inspiration or inhalation) air and giving out air (expiration or exhalation) from atmosphere. Inspiration (inhalation): Inspiration or process of taking in of air, in which...

Gas exchange through gills: Gas exchange across internal gill surfaces is extremely efficient. It occurs as blood and water move in opposite direction on either side of lamellar epithelium. For example the water that passes over a gill first encounters vessels that are transporting blood with low oxygen partial pressure into the body. Thus oxygen diffuses into the blood water than passes over the vessels carrying blood high in oxygen. More oxygen diffuses inward because this blood still has less oxygen than the surrounding water. Carbon dioxide also diffuses into water because its pressure is higher in the blood than in water. This counter current exchange mechanism provides efficient gas exchange by maintaining a concentration gradient between blood and water over the length of capillary bed. Respiratory organs of frog: Frog can live in water as well as on land. Its larval stages respire by gills, the adult has to develop some special respiratory organs adapted for ter...

Animal body is always exposed to the invasion of countless infectious microorganisms such as virus, bacteria. Due to the defense mechanisms evolved by the animals, such invasions in number of cases are overcome. The ability of the body to resist microorganisms, their toxins if any, foreign cells and abnormal cells of the body is termed as immunity. Immune system: Immunity is conferred to animals through the activities of the immune system which combats infectious agents. The study of functioning and disorders of the immune system is termed as immunology. Immune system is a collection of cells and proteins that work to protect the body from potentially harmful, infectious microorganisms. It also plays role in the control of cancer, allergy, hypersensitivity and rejection problems when organs or tissues are transplanted. The immune system can be divided into two functional divisions. (1) Innate immune system and (2) Adaptive immune system. (1) Innate immune system:...

lymphatic system: A system of blind vessels i.e. lymphatics that drains lymph from all over the body into the blood stream is called lymphatic system. In addition to lymphatics and lymph it consists of lymph nodes, splan, thymus, tonsils and some of the patches of tissues in vermiform appendix and small intestine. Lymph vascular system starts at capillary bed, where tissue fluid (intestinal fluid surrounding the cells of the tissues) enters the lymph capillaries which are closed towards the tissue sinuses. These are thin walled anastomosing microscopic vessels which form a network in every organ except the nervous system. The lymph capillaries merge into lymph vessels which have large diameter. These vessels contain smooth muscles in their walls as well as internal valves to prevent backward flow of lymph. The lymph circulates through the lymph vessels by the contraction of surrounding skeletal muscles in one direction, towards the heart. These vessels converge into collecting ...

Invertebrate Respiratory System: In single celled Protists such a Protozoa diffusion across the Plasma membrane moves gases into and out of the organism. In that worms all body cells are relatively close to the body surface or are thin walled and hallow. (e.g. Hydra). Again gases diffuse into and out of the animal. Forth worms live in moist environments and have capillary network just under their integument and they exchange gases with the air spaces among soil particles. Most aquatic invertebrates carry out gas exchange with gills e.g. sea stars. Marine and annelid worms have parapodia that are richly supplied with blood vessels and function as gills. Crustaceans and Molluscs have gills that are compact and protected with hard covering devices. Such gills divide into highly branched structures to minimize the gas exchange. Some terrestrial invertebrate like insects, centipedes and some mites, ticks and spiders have tracheal systems consisting of highly branched chitin lined tu...

Human heart moves blood into the body. It pumps its entire blood volume about five litres every minute; about 8000 litres of blood move through 96000 km; of blood vessels every day. The heart of average adult beats about 70 times per minute. Most of the human heart is composed of cardiac muscle tissue called myocardium (myo=muscle). Outer protective covering of heart is fibrous connective tissue called pericardium. Connective tissue and endothelium from the inside of the heart, the endocardium. Left and right halves of heart are two separate pumps each containing two chambers. In each half blood first flows into a thin walled atrium then into thick walled ventricle. Valves: Tricuspid valve is between right atrium and right ventricle. Bicuspid valve is between left atrium and left ventricle. They are collectively called Atrio-vascular values. Pulmonary semilunar valve is at the exit of right ventricle. The aortic semilunar valve is at the exit of left ventricle (collective...

Plasma: Plasma (any thing formed or molded) is the straw coloured liquid part of the blood. In mammals plasma is about 90 percent water and provides the solvent for dissolving and transporting nutrients. A group of proteins (albumen, fibrinogen and globulin) comprises another 7 percent of the plasma. The concentration of these plasma proteins influences the distribution of water between the blood and extra cellular fluid. Albumen is about 60 percent of the total plasma proteins and it plays important role with respect to water movement. Fibrinogen is necessary for blood coagulation (clotting). Globulins include immuno globulins and various metal binding proteins. Serum is plasma from which the protein involved in blood clotting has been removed. Gamma globulin portion functions in the immune response because it consists mostly of antibodies. Remaining 3 percent of plasma is composed of electrolytes, amino acids, glucose and other nutrients, various enzymes, hormones, meta...

Vertebrate Blood Vessels: Arteries: Arteries are elastic blood vessels that carry away blood from the heart to the organs and tissues of the body. Surrounding the lumen of an artery is a thick wall composed of three layers or tunicae or coverings. Outermost layer consists of connective tissue. The middle layer has elastic and smooth muscle tissue. Inner layer consists of single layer of smooth endothelial cells. Wall of artery is thicker than vein. Veins: Most veins are relatively inelastic, large vessels carry blood from the body tissues to the heart. The wall of a vein contains same three layers (tunicae) as arterial walls but the middle layer is much thinner and one or more valves are present. The valves permit blood flow in only one direction which is important in returning the blood to the heart. Capillaries: Arteries lead to terminal arterioles. The arterioles branch to form capillaries which connect to venules and the veins. Capillaries are generally composed o...

Transport in Cnidarians: Cnidarians such as Hydra have an internal fluid filled gastro vascular cavity. This cavity supplies nutrients for all body cells lining the cavity, provides oxygen from the water in the cavity and is a reservoir for carbon dioxide and other wastes. Simple body movement moves the fluid. Coelomic fluid: Some animals like Echinoderms, Annelids and Sipunculans are coelomic fluid as Supplementary or sole circulatory system. Coelomic fluid may be identified in composition to interstitial fluids or may differ particularly with respect to specific proteins and cells. Coelomic fluid transports gases, nutrients and waste products. It also functions in certain invertebrates like Annelids as a hydrostatic skeleton. Hemolymph: It is circulatory fluid of animals with an open circulatory system. Most Arthropods, Ascidians and many Molluscs have hemolymph. In these animals heart pumps hemolymph at low pressure through vessels to tissue spaces (hemocoel) and...

Birds: In birds pituitary gland secretes hormone prolactin. Prolactin stimulates production of “Pigeon’s milk” in pigeon’s crop. Prolactin also stimulates and regulates broodiness and certain other kinds of parental behaviour and along with estrogen stimulates full development of the brood pouch. Brood pouch helps to keep the eggs at temperature between 33 and 37°C. Birds thyroid gland produces hormone thyroxine. It regulates normal development of feathers and the molt cycle and plays a role in the onset of migratory behaviour.  In male birds the teats produce hormone testosterone. It controls the secondary sexual characters of male such as bright plumage colour, comb and spurs all of which strongly influence sexual behaviour. Below parathyroid glands are ultimobranchial glands which are small paired. They secrete hormone calcitonin involved in regulating blood calcium concentration. Bursa fabricuis is a sac that lies just dorsal to cloaca. Its tissues produce secretions...

Hormones of Neurohypophysis: It does not manufacture any hormones. Instead, neurosecretory cells of hypothalamus synthesize and secrete two hormones, antidivretic hormone and oxytocin, which move down nerve axons into neurohypophysis, where they are stored in the axon terminals until released. Diurectics stimulate urine excretion whereas antidiuretics decrease urine secretion. When a mammal begins to loose water and becomes dehydrated, antidiuretic hormone (A DH or vasopressin) is released in increased water absorption in the kidneys so that less urine is secreted, and water is retained. This negative feedback system thus restores water and solute homeostasis. Oxytocin stimulates smooth muscle contraction of the uterus to aid in the expulsion of the offspring and promotes the ejection of milk from the mammary glands to provide nourishment for new born. Both A Dh and oxytocin. Neurohypophysis is larger in animals that live in arid parts of the world where water conservat...