Chapter 7 : Structural Organisation In Animals

NCERT Notes For Class 11 Biology Download In PDF

POINTS TO REMEMBER

Tissue : A group of similar cells along with intercellular substances which perform a specific function.

Simple epithelium : is composed of a single layer of cells resting on a basement membrane.

Compound epithelium : consists of two or more cell layers and has protective function.

Areolar tissue : is a type of loose connective tissue present beneath the skin.

Adipose tissue : is a type of loose connective tissue which has cells specialised to store fats.

Neuroglia : A delicate connective tissue which supports and binds together the nerve tissue in the Central Nervous Tissue.

Malpighian tubules : Yellow coloured thin, filamentous tubules present at the junction of midgut and hindgut in cockroach; helps in excretion.

Uricotelic : Animals which excrete nitrogenous waste in the form of uric acid.

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

•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.

CONNECTIVE TISSUE

Loose Connective Tissue (has cells and fibres loosely arranged in semi-fluid ground substance)

(i) Areolar Tissue :
• present beneath the skin.
• contains fibroblasts, macrophages and mast cells.
• serves as a support framework for epithelium.

(ii) Adipase Tissue :
• located beneath the skin.
• cells are specialised to store fats. Dense Connective Tissue Fibres and fibroblasts are compactly packed.

(i) Dense Regular :
• Collagen fibres present in rows.
• Tendons attach skeletal muscle to bone.
• Ligaments attach bone to bone.

(ii) Dense Irregular :
• Has collagen fibres and fibroblasts oriented differently.
• This tissue is present in the skin. Specialised Connective Tissue

(i) Cartilage made up of chondrocytes and collegen fibres.
(ii) Bones Ground substance is rich in calcium salts and collegen fibres Osteocytes are present in lacunae
(iii) Blood Fluid connective tissue, consists of plasma and blood cells Muscle Tissue Consists of long, highly contractile cells called fibres; bring about move- ment and locomotion.

(i) Skeletal Muscle :
• Consists of long cylindrical, multinucleated fibres.
• Closely attached to skeletal bones.
• Striated.

(ii) Smooth Muscles :
• Consists of spindle like, uninucleated fibres.
• Do not show striations.
• Wall of internal organs such as blood vessels, stomach and intestine.

(iii) Cardiac Muscles :
• Short, cylindrical, uninucleated fibres.
• Occur in the heart wall.
• Intercalated discs for communication. Neural Tissue
• Neurons are the functional unit and are excitable cells.
• Neuroglia cells make up more than half the volume of neural tissue.

They protect and support neurons. Cockroach − Periplaneta americana is a terrestrial, nocturnal, omnivorous, unisexual, oviparous insect. Body covered by a chitinous, hard exoskeleton of hard plates called sclerites.

Head : Triangular, formed by fusion of 6 segments. Bears a pair of anten- nae, compound eyes. Mouth parts consists of labrum (upper lip), a pair of mandibles, a pair of maxillae, labium (lower lip), hypopharynx (acts as tongue).

Thorax : 3 segments; prothorax, mesothorax and metathorax.

Bears 2 pairs of wings : Forewings : tegmina (mesothoracic). Hindwings : transparent, membranous (metathoracic) and 3 pairs of legs in thoracic segments.

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. Also has anus and genital aperture at the hind end. Genital aperture sur- rounded by external genitalia called gonapophysis or phallomere.

Anatomy : Study of the morphology of internal organs. Alimentary canal : Divided into foregut, midgut and hindgut.
Mouth → Pharynx → Oesophagus → Crop (stores food) → Gizzard (grind- ing of food) → Hepatic caeca (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 mascular tube and differentiated into funnelshaped chambers with ostia on either side. Blood from sinuses enters heart through ostia and is pumped anteriorly to sinuses again. Blood colourless (haemolymph).

Repiratory system : Network of trachea which open through 10 spiracles. Spiracles regulated by sphincters. Oxygen delivered directly to cells. Excretion and osmoregulation by Malpighian tubules; uricotelic (Uric acid as excretory product).

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 supra-oesophageal ganglion.

Reproductive system : Male − 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 chamberSperms transferred through spermatophores. Fertilised eggs encased in cap- sules called oothecae; development of P. americana paurometabolous (incomplete 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).

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