Animal tissue : There are four types of tissue found in higher animals. These are: (i) epithelial tissue, (ii) connective tissue, (iii) muscular tissue and
(iv) nervous tissue.
Epithelial tissue : Epithelial tissues are those tissues that form the covering of outer and inner surfaces of various organs of the body. These tissues generally serve as a protective covering both internally and externally. Since they cover the surface of the body or line the internal organs, they are also called ‘boundary tissues’. These are of several types—
Classification : (a) Simple epithelial tissue : This kind of epithelial tissue has a single layer of cells, which rest on a thin layer of connective tissue.
(i) Simple squamous epithelium.
(ii) Simple coboidal epithelium.
(iii) Simple columnar epithelium.
(iv) Ciliated epithelium.
(v) Glandular epithelium.
(b) Stratified epithelium : This kind of epithelial tissue contains many layers of cells.
Connective tissue: These tissues are the tissues responsible for connecting various tissues and organs of the body.
Classification : Connective tissues are classified in several types depending on the nature of the matrix, and type of fibres and cells, e.g., areolar tissue, adipose tissue, cartilage, bone and blood.
Areolar tissue : Areolar tissues are those connective tissue mainly composed of tissue cells, fibres and matrix, which binds different tissues and organs together.
These tissues are distributed almost all over the body. These tissues bind and support different tissues and organs.
Adipose tissue : Adipose tissues are those connective tissues consisting of fat filled round or oval shaped cells. They are found under the skin between the muscles and also around certain important organs like heart, kidney, etc. They work like a pad and protect the inner parts of the body from mechanical injury, heat and cold.
Cartilage : It is a elastic connective tissue with hard, rubbery matrix and consisting of chondrocyte cells. It is found in mammals in external pinna, tracheae and bronchii.
Bone : The hardest non-elastic connective tissue with calcium matrix and osteocyte cells (bone cells) is known as bone.
Blood : Blood is a fluid connective tissue. It consists of the liquid plasma with three types of cells : (a) red blood corpuscles or erythrocytes, (b) white blood corpuscles or leucocytes and
(c) platelets or thrombocytes.
Plasma : The plasma is a yellowish straw coloured fluid, which serves to carry food to cells of the body tissues. It also takes away various wastes that are formed by tissue cells.
Red blood corpuscles (RBC) : Each red blood corpuscle or erythrocyte is a thin, nucleated, biconvex oval disc shaped containing an iron bearing protein called haemoglobin.
White blood corpuscles (WBC) : White blood corpuscles are also nucleated but they are colourless, of irregular shape and lesser than the red blood corpuscles. White blood corpuscles are able to change shape and they protect the body by destroying bacteria and other foreign invaders.
Platelets : Platelets or thrombocytes are very minute spindle shaped bodies present in the plasma. Coagulation of blood is their main function.
Muscular tissue : Muscular tissue is found in multicellular animals whose contraction and relaxation result in the movement of different organs of the body or brings about locomotion of the whole body.
Classification : Muscular tissues are of three types : Classification depends on structure and function. These are
(i) skeletal or striated muscle, (ii) smooth or non-striated muscle, and (iii) cardiac muscle.
Striated muscle : The tissue which remains attached to the bones mainly is called striated muscle. The striated muscle is under voluntary control so it is also known as voluntary muscle.
Smooth muscle : This type of muscle tissue is distributed on the visceral organs, alimentary canal, blood vessels, muscles of the eye etc. It is neither cross-striated nor under voluntary control. So it is called non-striated or involuntary muscles.
Cardiac muscle : Cardiac or heart muscle is present in the wall of heart chambers.
Nervous tissue : This tissue receives and conveys electrochemical nerve impulse (stimulus) and controls and coordinates the activities of other tissues, is known an ‘nervous tissue’.
Synapse : The synapse is the junction between the axon of one neuron and the dendrite of the next.
Various systems of Human Body
(i) Digestive system
(ii) Respiratory system
(iii) Circulatory system
(iv) Excretory system
(v) Nervous system
(vi) Integumentary system
(vii) Endocrine system
(viii) Muscular system
(ix) Skeletal system
(x) Reproductive system.
Main organs of various systems
(i) Digestive system : Mouth, pharynx, tongue, salivary glands, oesophagus, stomach, small intestines, large intestine and annal opening are the organs of digestive system.
(ii) Respiratory system : Nostrils, nasal passages, nasopharynx, Iarynyx, trachea, bronchi, bornchioles, lungs are the organs of respiratory system.
(iii) Circulatory system : Pumping organ, the heart and arteries, veins and capillaries are the organs of circulatory system.
(iv) Excretory system : Kidneys, ureters, urinary bladder constitute excretory system.
(v) Endorcrine system : Pituitary gland, thyroid gland, parathyroid gland, adrenals, pancreas, pineal, thymus, testes, placenta, ovaries etc. are ductless glands.
(vi) Nervous system : Various nerves.
(vii) Reproductive system : In males pair of testes epididymis, vas deferens, seminal vesicles, prostrate glands, cowper’s gland, penis.
In females—Pair of ovaries, fallopian tubes, uterus, vagina, mammary glands are the organs of reproductive system.
(viii) Skeletal system : Skull, vertebral column, ribs, girdles and hyoid apparatus are the parts of skeletal system.
(ix) Muscular system : Various muscle fibres, (a) striated
(b) unstriated (c) cardiac. Internal organs and heart.
Gland : It is an organ of the body that is formed of spontaneous epithelial cells and it secretes some useful substances.
Types of glands
(i) Exocrine glands or ducted glands.
(ii) Endocrine glands or ductless glands.
Collagen : It is a kind of protein synthesised by fibroblasts. Collagen fibers are white, long, waxy, non-branching and are in bundles.
Elastin : A kind of protein synthesized by fibroblasts is elastic fibres. The elastic or yellow fibres are long, branching and are made up of elastin.
Cartilage : It is a semi-rigid and flexible connective tissue. It is formed of chondrocytes.
Blood : It is a fluid connective tissue. The volume of blood in an adult person is about 5 litres.
Plasma : It is a slightly alkaline, viscous, aqueous solution containing many organic and inorganic susbtances. It contains about 92% water and 8% solids.
Classes of Plasma proteins :
(i) Fibrogen
(ii) Serum albumin
(iii) Serum globulin.
Hematocrit value or packed cell volume : It is the relative volume of erythrocytes as a percentage of the total blood volume. It normally forms 40-45% of blood volume.
Haemoglobin : Red pigment containing iron, within vertebrate red blood cells, responsible for the transport of oxygen throughout the body.
Haemocyanin : It is a blue copper protein complex present in prawn and crab. It acts as an oxygen carrier in them.
Chlorocruorin : Found in some annelids, it is an oxygen carrying agent (pigment).
Erythrocyte sedimentation rate (Esr) : If a sample of oxalated blood is kept undisturbed in a long, narrow graduated tube, erythrocytes settle down slowly from blood due to gravity. The rate of such sedimentation is called ESR.
Blood Coagulation : Due to injury blood oozes out of a cut but soon it stops oozing out due to clotting. It is blood coagulation.
Neurons : The cells of nerve tissues are called neurouns.
Neuroglia Cells : The neurons are held together by supporting cells, called neuroglia cells.
Neuro Transmitters : Nerve impulses pass between neurons through the synapse by chemicals such as acetylcholine which are known as neuro-transmitters.
Perikaryon : The cell body of neurons is called perikaryon or soma.
Nissle’s Bodies : The soma or cell body has many small, conical angular or rhomboid and highly basophilic structures. These are called Nissle’s bodies.
Medulated Nerve fibres : Some nerve fibres are covered by lipid rich insulating layer known as myelin sheath. Such nerve fibres are called myelinate or medulated nerve fibres.
Non-Medulated Nerve Fibres : These nerve fibres are not covered by a myelin sheath.
Haemopoiesis or Haematopoiesis : This is the process of formation or development of blood cells in the body.
Lymphopoiesis : It is the process of formation of blood cells (only lymphocytes) in the lymphiod tissues of the body.
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