CHAPTER 7 STRUCTURAL ORGANISATION IN ANIMALS
Tissue
In multicellular organism a group of similar cells along with intercellular substances perform a specific function. Such organization is called tissue.
Epithelial Tissue
This tissue provides covering or lining for some part of the body. Cells are compactly packed without intercellular space.
Simple Epithelial:
Composed of single layer of cells & Functions as lining for body cavities, ducts and tubes.
Squamous Epithelium:
Single thin layer of flattened cells found in walls of blood vessels, air sacs of lungs.
Cuboidal Epithelium:
Single layer of cube like cells found in ducts of glands and tubular parts of nephron.
Columnar Epithelium:
Single layer of tall and slender cells & free surface may have microvilli & found in lining of stomach and intestine.
Ciliated Epithelium:
Columnar or cuboidal cells with cilia move particles or mucus in specific direction, in bronchioles, fallopian tubes.
Cell junctions
In nearly all animal tissues, specialized junction provide structural and functional links between its individual cells.
Three Types of Cell junctions:
Tight junctions:
Plasma membranes of adjacent cells are fused at intervals. They help to stop substances from leaking across a tissue.
Adhering junctions:
Perform cementing function to keep neighbouring cells together.
- Gap junction:
- Facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells for rapid transfer of ions, small molecules and sometimes big molecules.
Compound Epithelium
- Made of more than one layer of cells.
- Provide protection against chemical and mechanical stresses.
- Cover dry surface of skin, moist cavity, pharynx, inner lining of ducts of salivary glands and pancreatic ducts.
Glandular Epithelium
- Exocrine glands
- Endocrine glands
Exocrine glands
- Secrete mucus, saliva, oil, milk digestive enzymes.
- Products released through ducts.
Endocrine glands
- Secrete hormones.
- Secrete directly into the fluid bathing the gland.
Connective tissue
They are most abundant and widely distributed tissues which link and support the other tissues. All connective tissues except blood cells, secrete fibers of structural protein called collagen or elastin to provide elasticity and flexibility.
Loose Connective Tissue:
contain cells and fibers loosely arranged in semi-fluid ground substance. It includes areolar tissue and adipose tissue.
Areolar Tissue
- Present beneath the skin.
- Contains fibroblasts, macrophages and mast cells.
- Serves as a support framework for epithelium.
Adipose Tissue
- Located beneath the skin.
- Cells are specialized to store fats.
Dense connective Tissue:
Dense connective Tissue contains fibers and fibroblast compactly packed. The orientation of fibers may be regular or irregular pattern In dense regular connective tissues collagen fibers are present in rows between parallel bundles of fibers as in tendons and ligaments.
Tendon
- Tendon connects bones to skeletal muscles.
- It is made up of white fibrous tough tissue.
Ligament
- Ligament connects one bone to another bone.
- It is made up of yellow elastic tissue with collagen fibers.
Cartilage
- They are soft skeletal tissue.
- chondrocyte are enclosed in small cavities with matrix.
- They are present in tips of nose, outer ear, between vertebral bones.
Bone
- Bones are hard skeletal tissue.
- They are rich in Calcium salt and collagen fibers.
- They form the skeletal framework of vertebrates like limbs, legs, etc.
Blood
Blood is fluid connective tissue containing plasma, red blood cells, white blood cells and platelets. It helps in transportation of various substances between organs.
Muscle Tissue
Each muscle is made up of long cylindrical fibers arranged parallel to each other. Fibers are composed of fine fibrils called myofibrils. Muscle fibers contract and relax in response to stimulation.
Skeletal Muscle
- They are also known as striated, voluntary muscles.
- Multinucleated with light and dark bands.
- They are attached with bones.
- They are fibrous and un-branched, cylindrical in shape.
Smooth Muscle
- They are known as unstriated or involuntary muscles.
- They are uninucleate without bands.
- They are present in vessels, oesophagus.
- They are fibrous and un-branched, spindle shaped.
Cardiac Muscle
- They are known as heart muscles and involuntary in nature.
- Uninucleate with faint light and dark bands.
- They are present in wall of heart.
- They are fibrous and branched, cylindrical in shape.
Neural Tissue
- The unit of neural system is neuron. Neuroglial cell protects and supports the neuron.
- When neuron get stimulated, electrical impulses are generated that travel along the plasma membrane (axon).
Cockroach
Periplaneta americana (Phylum-Arthropoda, Class-Insecta)
Habitat:
Cockroach is a terrestrial, nocturnal, ominivorous, unisexual, oviparous insect. Body covered by a chitinous, hard exoskeleton of hard plates called sclerities.
Morphology
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Head:
- Triangular, formed by fusion of 6 segments. Bears a pair of antennae, compound eyes. Mouth parts consists of labrum (upper lip), a pair of mandibles, a pair of maxillae, labium (lower lip), hypharynx (acts as tongue).
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Thorax:
- 3 segments; prothorax, mesothorax and metathorax. Bears 2 pairs of wings
-
Forewings:
- tegmina (mesothoracic).
-
Hindwings:
- transparent, membranous (metathoracic) 3 pairs of legs in thoracic segments. (one pair in each thoracic segment.)
-
Abdomen:
- 10 segments. Bears a pair of long, segmented anal cerci in both sexes and a pair of short, unjoined anal styles in males only 7th segment is boat shaped. Also has anus and genital aperture at the hind end. Genital aperture surrounded by external genitalia called gonapophysis or phallomere.
Male Cockroach:
Abdomen long and narrow, All nine sterna visible & Anal style present.
Female Cockroach:
Abdomen short and broad, Seven sterna visible. (7th sternum fused with 8th and 9th sterna) & Anal style absent.
Alimentary canal:
Divided into foregut, midgut and hindgut. Mouth → Pharynx → Oesophagus → Crop (stores food) → Gizzard (grinding of food) → Hepaticcaecae (at junction of fore and midgut; secretes digestive juice) → Hindgut (ileum, colon, rectum) → Anus.
Blood vascular system:
Open type, visceral organs bathed in haemolymph (colourless plasma and haemocytes). Heart consists of enlongated muscular tube and differentiated into funnel shaped chambers with ostia on either side. Blood from sinuses enters heart through ostia and is pumped anteriorly to sinuses again. Blood is colorless (haemolymph).
Repiratory system:
Network of trachea which open through 10 pairs of spiracles. Spiracles regulated by sphincters. Oxygen delivered directly to cells.
Excretion and osmoregulation:
by malpighian tubules; uricotelic (Uric acid as excretory proudct).
Nervous system:
Consists of series of fused segmentally arranged ganglia joined by paired longitudinally connectives on the ventral side, three ganglia in thorax, six in abdomen. Brain represented by supraoesophageal ganglion. Each eye consist s of 200 hexagonal ommatidia.
Reproductive system
Male reproductive system:
Pair of testes (4th-6th segments) → vas deferens → ejaculatory duct → male gonophore. Glands–Seminal vesicle (stores sperms), mushroom shaped gland (6th-7th segment).
Female reproductive system:
A pair of ovaries (with 8 ovarian tubules) → Oviduct → Genital chamber. Sperms transferred through spermatophores female produces 9–10 Ootheca. Fertilized eggs encased in capsules called oothecae (contains 14-16 eggs on an average) development of P. americana paurometabolous incompleted metamorphosis). Nymph grows by moulting 13 times to reach adult form.
Interaction with man:
Pests as destroy food and contaminate it.
Can transmit a variety of bacterial diseases (Vector).