Chapter-7
Structural Organisation In Animals
Points to Remember
- Cell Junction : In nearly all animal tissues, specialised junction provide structural and functional links between its individual cells.
Three Types of Cell Junction :-
- 1. Tight junction : Plasma memebranes of adjacent cells are fused at intervals. They help to stop substances from leaking across a tissue.
- 2. Adhering junction : Perform cementing function to keep neighbouring cells together.
- 3. 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.
Types of Fundamental Animal Tissues
Epithelial Tissue
(A) Simple :- Composed of single layer of cells.
- Functions as lining for body cavities, ducts and tubes.
- Single thin layer of flatted cells.
- Found in walls of blood vessels, ait sacs of lungs.
- Single layer of cube like cells.
- Found in ducts of glands and tubular parts of mephron.
- Single layer of tall and slender cells.
- Free Surface may have microvilli.
- Found in lining of stomach and intestine.
- Columnar or Cuboidal cells with cilia.
- Move particles or mucus in specific direction, in bronchioles, fallopian tubes.
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1. Squamous :
- Made up of more than one layer of cells.
- Provide protection aganist chemical and mechanical stresses.
- Cover dry surface of skin, moist, cavity, pharyx, inner lining of ducts of salivary glands and pancreatic ducts.
Loose Connective Tissue
- Present beneath the skin.
- Contains fibroblasts, macrophages and mast cells.
- Serves as support framework for epithelium
- Located beneath the skin.
- Cells are specialised to store fats.
(Has cells and fibres loosely arranged in semi-fluid ground substances)
(i) Areolar Tissue :(ii) Adipose Tissue :
Dense Connective Tissue
- Collagen fibres present in rows.
- Tendons attach skeletal muscle to bone.
- Ligaments attach bone to bone.
- Has Collagen fibres and fibroblasts oriented differently.
- This tissue is present in the skin.
Fibres and fibroblasts are compactly packed.
(i) Dense Regular :(ii) Dense Irregular :
Specialised Connective Tissue
- (i) Cartilage : Made up of chondrocytes and collagen fibres; inter cellular material is solid and resists compression. Present in tip of nose outer ear joints, etc.
- (ii) Bones : Ground substances is rich in calcium salts and collagen fibres Ostecoytes are present in lacunae. Bones support and protect softer tissue and organs. They interact with skeletal muscles to bring about movements. Bone marrow in some bones is the site of blood cell formation.
- (iii) Blood : Fluid connective tissue, consists of plasma and blood cells.
Neural Tissue
- Neurons are the functional unit and are excitable cells.
- Neurogila cells make up more than half the volume of neural tissue.
They protect and support neurons.
- Cockroach -- Periplaneta americana (Phylum-Arthropoda, Class-Insecta)
- Habitat : Cockroach is a terrestrial, nocturnal, ominivorous, unisexual, oviparous insect. Body convererd by a chitinous, hard exoskeleton of hard plates called scelritis.
- Morphology :
- Head : Triangular, formed by fusion of 6 segments. Bears a pair of antennae, compound eyes. Mouth parts consits 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 paris of wings:
Forewings : Tegmina (mesothoracic).
Hindwings : Transparent, memebranous (matathoracic)
3 pairs of legs in thoracic segments. (one pair in each thoracic segment.)
- Abdomen : 10 segment, 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 bind end. Gential aperture surrouonded by extternal genitalia called gonapophysis or phallomere.
| Male Cockroach | Female Cockroach |
|---|---|
|
1. Abdomen long and narrow
2. All time sterna visible 3. Anal style present |
1. Abdomen short and broad
2. Seven sterna visible. (7th sternum fused with 8th and 9th sterna) 3. Anal style absent. |
- Anatomy : Study of the morphology of internal organs.
- Alimentary canal : Divided into foregut, midgut and hindgut.
- Mouth → Pharynx → Oesophagus → Crop(stores food) → Gizzard(grinding of food) →
Hepatic caecae (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 consist of enlongated musucular tube and differntiated into funnel shaped chamebers with ostia on either side. Blood form sinuses enters heart through ostia and is pumped anteriorly to sinuses again. Blood is colourless (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 excertory 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 supraoesophageal ganglion. Each eye conists of 200 hexagonal ommatidia.
Male 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. Fertilised 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.
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Interaction with man
- Pests as destory food and contaminate it.
- Can transmit a variety of bacterial diseases (Vector).
