Animal Structural Org. (NEET)

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### Animal Tissues: An Overview - **Definition:** A group of similar cells having a specific function. - **Four Main Types:** 1. Epithelial Tissue 2. Connective Tissue 3. Muscular Tissue 4. Neural Tissue ### Epithelial Tissue - **Characteristics:** Cells are compactly packed with little intercellular matrix. Forms covering/lining for body parts. - **Functions:** Protection, secretion, absorption, filtration, diffusion. - **Types based on number of cell layers:** - **Simple Epithelium:** Single layer of cells. Functions in lining body cavities, ducts, and tubes. - **Squamous:** Flat, irregular boundaries. Found in blood vessels, air sacs of lungs (diffusion). - **Cuboidal:** Cube-like cells. Found in kidney tubules, ducts of glands (secretion & absorption). - **Columnar:** Tall, slender cells. Nuclei at base. Found in stomach, intestine (secretion & absorption). - **Ciliated Columnar/Cuboidal:** Cilia on free surface. Found in bronchioles, fallopian tubes (move particles). - **Glandular:** Specialized for secretion. - **Unicellular:** Goblet cells (alimentary canal). - **Multicellular:** Salivary glands. - **Exocrine:** Secrete into ducts (e.g., salivary, sweat). - **Endocrine:** Secrete hormones directly into blood (ductless glands). - **Compound Epithelium:** Two or more cell layers. - **Functions:** Protective function (skin surface, buccal cavity, pharynx, pancreatic ducts). - Limited role in secretion/absorption. - **Cell Junctions:** - **Tight Junctions:** Prevent leakage across tissue. - **Adhering Junctions:** Cement neighboring cells together. - **Gap Junctions:** Facilitate communication, rapid transfer of ions/molecules. ### Connective Tissue - **Characteristics:** Most abundant and widely distributed tissue. Links and supports other tissues/organs. - **Components:** Cells, fibers (collagen, elastin, reticular), ground substance (matrix). - **Functions:** Binding, support, protection, insulation, transport (blood). - **Types:** - **Loose Connective Tissue:** - **Areolar tissue:** Beneath skin, supports epithelia. Contains fibroblasts, macrophages, mast cells. - **Adipose tissue:** Stores fat. Found beneath skin, around organs. - **Dense Connective Tissue:** Fibers and fibroblasts are compactly packed. - **Dense Regular:** Collagen fibers in parallel rows. - **Tendons:** Connect muscle to bone. - **Ligaments:** Connect bone to bone. - **Dense Irregular:** Fibers irregularly arranged. Found in skin, around muscles. - **Specialized Connective Tissue:** - **Cartilage:** Solid, pliable matrix (chondroitin salts). Chondrocytes in lacunae. Found in nose tip, outer ear, between vertebrae, limb bones. - **Bone:** Hard, non-pliable matrix (calcium salts, collagen fibers). Osteocytes in lacunae. Supports, protects, stores calcium/phosphate. - **Haversian canals:** Present in compact bone (mammals). - **Blood:** Fluid connective tissue. Plasma (fluid matrix), Red Blood Cells (RBCs), White Blood Cells (WBCs), Platelets. - **Functions:** Transport of gases, nutrients, hormones, waste. Immunity. ### Muscular Tissue - **Characteristics:** Made of elongated cells called muscle fibers. Responsible for movement. - **Types:** - **Skeletal Muscle:** - **Structure:** Striated (striped), multinucleated, voluntary. - **Location:** Attached to bones. - **Function:** Locomotion, body movements. - **Smooth Muscle:** - **Structure:** Non-striated, spindle-shaped, uninucleate, involuntary. - **Location:** Walls of internal organs (e.g., stomach, intestine, blood vessels). - **Function:** Peristalsis, regulation of blood flow. - **Cardiac Muscle:** - **Structure:** Striated, branched, uninucleate, involuntary. Intercalated discs present (communication junctions). - **Location:** Heart wall. - **Function:** Rhythmic contraction and relaxation of the heart. ### Neural Tissue - **Characteristics:** Excitable cells (neurons) and supporting cells (neuroglia). - **Neuron:** Structural and functional unit. - **Components:** Cell body (cyton), dendrites, axon. - **Function:** Transmit electrical impulses (nerve impulses). - **Neuroglia:** Non-excitable supporting cells. Protect and support neurons. - **Location:** Brain, spinal cord, nerves. - **Function:** Control and coordination. ### Earthworm (Pheretima posthuma) - **Phylum:** Annelida - **Habitat:** Moist soil. Nocturnal. - **Body Plan:** Segmented (metameres, 100-120 segments). Clitellum (segments 14-16) for cocoon formation. - **Digestive System:** Complete. Mouth (1st segment) $\rightarrow$ Buccal cavity $\rightarrow$ Pharynx $\rightarrow$ Oesophagus $\rightarrow$ Gizzard (grinding) $\rightarrow$ Stomach $\rightarrow$ Intestine (typhlosole for increased absorption) $\rightarrow$ Anus. - **Circulatory System:** Closed type. Heart (lateral hearts in segments 7, 9, 12, 13). Blood glands in segments 4, 5, 6 produce blood cells and hemoglobin dissolved in plasma. - **Respiratory System:** Cutaneous respiration (moist skin). - **Excretory System:** Nephridia (segmentally arranged excretory organs). - **Septal nephridia:** Segments 15 to last. - **Integumentary nephridia:** Segments 3 to last. - **Pharyngeal nephridia:** Segments 4, 5, 6. - **Nervous System:** Ganglia, nerve ring, ventral nerve cord. - **Reproductive System:** Hermaphrodite (bisexual). - **Male:** Testes (10th, 11th segment), seminal vesicles, prostate glands (17th, 18th segment). Male genital pores (18th segment). - **Female:** Ovaries (13th segment), oviducts, spermathecae (6th-9th segments for sperm storage). Female genital pore (14th segment). - **Fertilization:** Cross-fertilization, cocoon formation. - **Economic Importance:** Farmers' friend (vermicomposting, increasing soil fertility). ### Cockroach (Periplaneta americana) - **Phylum:** Arthropoda, Class: Insecta. - **Habitat:** Damp places, nocturnal. Omnivorous. - **Body Plan:** Segmented, chitinous exoskeleton. Head, Thorax, Abdomen. - **Head:** Triangular, formed by fusion of 6 segments. Compound eyes, antennae, mouthparts (biting and chewing type). - **Thorax:** Prothorax, Mesothorax, Metathorax. Each bears a pair of legs. Forewings (tegmina) from mesothorax, hindwings from metathorax. - **Abdomen:** 10 segments. Anal cerci in both sexes (10th segment). Anal styles only in males (9th segment). - **Digestive System:** Complete. Mouth $\rightarrow$ Pharynx $\rightarrow$ Oesophagus $\rightarrow$ Crop (storage) $\rightarrow$ Gizzard (grinding) $\rightarrow$ Midgut (mesenteron) $\rightarrow$ Hindgut (ileum, colon, rectum) $\rightarrow$ Anus. - **Hepatic Caeca:** At junction of foregut and midgut (secrete digestive juice). - **Malpighian Tubules:** At junction of midgut and hindgut (excretion). - **Circulatory System:** Open type. Haemolymph in haemocoel. Heart is elongated, tubular, 13-chambered. - **Respiratory System:** Tracheal system (network of tracheae opening via spiracles). - **Excretory System:** Malpighian tubules (main excretory organs), also fat body, nephrocytes, uricose glands. Uricotelic. - **Nervous System:** Ganglia arranged segmentally, fused to form supra-oesophageal ganglion (brain). - **Reproductive System:** Dioecious (separate sexes). - **Male:** Pair of testes (4th-6th segment), vas deferens, ejaculatory duct, seminal vesicle, mushroom gland, phallic gland. Male gonopore. - **Female:** Pair of ovaries (2nd-6th segment), oviducts, vagina, spermatheca. Female gonopore. - **Fertilization:** Internal. Ootheca (egg capsule) formed, containing 14-16 eggs. - **Economic Importance:** Pests, vectors of diseases. ### Frog (Rana tigrina) - **Phylum:** Chordata, Class: Amphibia. - **Habitat:** Fresh water, moist land. Poikilothermic (cold-blooded). - **Body Plan:** Head and Trunk. Neck and tail absent. Skin moist, slippery. - **Digestive System:** Complete. Mouth $\rightarrow$ Buccal cavity $\rightarrow$ Pharynx $\rightarrow$ Oesophagus $\rightarrow$ Stomach $\rightarrow$ Intestine $\rightarrow$ Rectum $\rightarrow$ Cloaca. - **Tongue:** Bilobed, protrusible. - **Digestive Glands:** Liver (bile), Pancreas (pancreatic juice). - **Circulatory System:** Closed type. Three-chambered heart (two atria, one ventricle). Double circulation (incomplete). - **Portal Systems:** Hepatic portal system, Renal portal system. - **Respiratory System:** - **Cutaneous respiration:** Through moist skin (on land and water). - **Buccal respiration:** Through lining of buccal cavity. - **Pulmonary respiration:** Through lungs (on land). - **Excretory System:** Pair of kidneys (mesonephric). Ureters, cloaca. Ureotelic. - **Nervous System:** Well-developed. Brain (forebrain, midbrain, hindbrain), spinal cord, nerves. - **Reproductive System:** Dioecious. - **Male:** Pair of testes (yellowish, ovoid) attached to kidneys. Vasa efferentia, kidney, ureter (urinogenital duct). Cloaca. - **Female:** Pair of ovaries (near kidneys). Oviducts, cloaca. - **Fertilization:** External (in water). Development indirect (tadpole larva). - **Economic Importance:** Food source, insectivorous (beneficial to farmers).