Epithelial Tissues
* Animal tissues are broadly classified into four types, namely epithelial connective, muscular and neural.
* Epithelial cells are compactly arranged with little intercellular matrix.
* The epithelium and other tissues have three types of specialised junctions, namely tight, adhering and gap junctions.
* Simple epithelium consists of a single layer of cells and serves as a lining for body cavities, ducts and tubes.
* Compound epithelium consists of two or more layers and its chief function is protection against mechanical and chemical stress.
* Simple epithelium is categorised into squamous, cuboidal and columnar.
* Some cuboidal and columnar cells have cilia on their free surface and therefore called ciliated epithelium.
* Some cuboidal and columnar cells are also specialised for secretion and are therefore called glandular epithelium.
* Glandular epithelium cells are of two types- unicellular and multi-cellular.
Connective Tissues
* Connective tissues are the most abundant and widely distributed tissues in animals.
* Connective tissues help to link and provide support to other tissues and organs throughout the body.
* Connective tissues are categorised into three types-loose connective, dense connective and specialised connective.
* In loose connective tissues, the cells and fibres are loosely arranged in a semi-fluid matrix.
* In dense connective tissue, the fibres and fibroblasts are compactly arranged.
* Specialised connective tissue consists of cartilage, bone and blood.
Muscular and Neural Tissues
* Each muscle consists of many long, cylindrical fibres arranged in parallel arrays called muscle fibres.
* There are three types of muscles, namely skeletal, smooth and cardiac.
* Skeletal muscles are striated and voluntary and constitute a major percentage of body mass.
* Smooth muscles are unstraiated and involuntary and are found in blood vessels. the stomach and intestine.
* The cardiac muscle is a contractile, involuntary muscle found only in the heart.
* Neural tissue consists of neurons and neuroglia that are concerned with the responsiveness of the body.
Morphology of an Earthworm
* Earthworms are cylindrical, segmented invertebrates found in the upper moist layers of soil.
* The dorsal surface has a dorsal blood vessel, while the ventral surface has four pairs of spermathecal aperture and genital openings.
* The anterior end of the earthworm consists of the mouth and the prostomium.
* Mature earthworms have a thick, dark band of glandular tissue called the clitellum.
* Earthworms move with the help of setae.
Anatomy of an Earthworm
* The body wall consists of a single layer of epidermis, two muscle layers- circular and longitudinal followed by the innermost coelomic epithelium.
* The alimentary canal is a straight tube that rune from the first to the last segment of the body.
* The circulatory system is of closed type and consists of blood vessels, capillaries and hearts.
* In earthworms, the excretory organs are nephridia, which are of three types, namely septal, integumentary and pharyngeal.
* The nervous system consists of ganglia, which are connected to a double ventral nerve cord.
* Earthworms possess light and touch sensitive receptors to help them recognise light intensities and ground vibrations.
* Although earthworms are hermaphrodites, each worm mates with another worm and exhibits direct development.
Morphology of a Cockroach
* The body of a cockroach is dorso-ventrally flattened and is covered in a hard, brown chitinous exoskeleton.
* The body is divided into the head, thorax and abdomen.
* The head of cockroach is triangular and bears a pair of compound eyes, a pair of slender antennae and mouth parts.
* The thorax consists of three segments – prothorax, mesothorax and metathorax.
* The abdomen of both male and female cockroaches consists of 10 segments.
* In males and females, the tenth segment bears a pair of jointed, filamentous anal cerci that function as sense organs.
* The males bear a pair of short anal styles, which are absent in females.
Anatomy of a Cockroach
* The alimentary canal is well-developed and divided into foregut, midgut and hindgut.
* Cockroaches have an open blood vascular system, which consists of poorly developed blood vessels that open into the haemocoel.
* The respiratory system consists of a network of trachea that opens to the exterior through 10 pairs of spiracles located on the lateral side of the body.
* Malpighian tubules situated at the junction of the midgut and hindgut serve as excretory organs.
* The nervous system consists of a series of ganglia in each segment, which is attached to a ventral nerve cord ad a brain.
* Sensory organs include antennae, eyes, maxillary palps, labial palps and anal cerci.
* Cockroaches are unisexual insects with well-developed male and female reproductive systems.
Morphology of Frog
* Frogs are tailless amphibians usually found in tropical regions.
* Frogs are cold-blooded and they undergo hibernation in winter and aestivation in summer.
* Frogs are also known to camouflage themselves according to their surroundings to hide from predators.
* The skin of a frog is smooth, slippery and moist, which helps in the diffusion of respiratory gases.
* The body is divided into two regions – head and trunk and there is no neck and tail.
* Male frogs possess two vocal sacs and a copulatory pad, which are absent in female frogs.
Anatomy of Frog
* The digestive system consists of the alimentary canal and digestive glands.
* In water, frogs respire through their skin, and on land, they respire through the buccal cavity, skin and lungs.
* Frogs have a well-developed blood vascular system and a lymphatic system.
* The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.
* The main endocrine glands in frogs are pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads.
* Frogs possess different sense organs such as sensory papillae, taste buds, nasal epithelium, eyes and tympanum with internal ears.
* Frogs are unisexual animals with well-developed male and female reproductive systems.