Animal Tissues & Frog Anatomy — Essential NEET Facts — Summary

Epithelial tissue is avascular; cells rest on a basement membrane; nourishment via underlying connective tissue.
Simple squamous epithelium: flat cells; location — alveoli, blood capillaries; function — diffusion and filtration.
Cuboidal epithelium: cube-shaped cells; kidney tubules and salivary ducts; secretion and absorption.
Ciliated epithelium: columnar cells with cilia; trachea (clears particles) and oviducts (moves ova).
Compound epithelium: multi-layered; skin, pharynx, buccal cavity; primarily protective.
Connective tissue is the most abundant tissue; defined by an extensive extracellular matrix.
Blood is a specialized connective tissue; plasma is the matrix; formed elements are RBCs, WBCs, platelets.
Tendon = muscle to bone (dense regular, parallel collagen). Ligament = bone to bone (collagen + elastin).
Cartilage: chondrocytes in lacunae; matrix = chondroitin sulfate. Three types: hyaline, elastic, fibrocartilage.
Bone: osteocytes in lacunae; concentric lamellae around Haversian canal = Haversian system; matrix = calcium phosphate.
Skeletal muscle: striated, voluntary, multinucleated, cylindrical, unbranched, fatigable.
Smooth muscle: non-striated, involuntary, uninucleated, spindle-shaped, slow sustained contraction.
Cardiac muscle: striated, involuntary, uni/binucleated, branched, intercalated discs, autorhythmic. Located exclusively in the heart wall.
Intercalated discs contain gap junctions that allow synchronized myocardial contraction.
Neuron structure: cyton (cell body) + dendrites (receive impulses) + axon (transmit impulses).
Neuroglia: Schwann cells (PNS myelin), astrocytes, oligodendrocytes (CNS myelin), microglia.
Frog heart: three chambers — two atria + one ventricle.
Frog respiration: three routes — cutaneous (skin, must be moist), buccopharyngeal, pulmonary.
Frog excretion: ureotelic; mesonephric kidneys; common exit = cloaca.
Frog nervous system: 10 pairs of cranial nerves.
Male frog: vocal sacs and nuptial pads; external fertilization.