Structural Organisation in Animals | Plus 1 Exam Capsule Notes (Web and PDF)

STRUCTURAL ORGANISATION IN ANIMALS: CHAPTER AT A GLANCE

CLASSIFICATION OF ANIMAL TISSUES

1. Epithelial tissues (Epithelium)

a. Simple (single layered)

    i. Squamous: 

• Location: Walls of blood vessels and alveoli.
• Function: Diffusion.

    ii. Cubical (cuboidal): 

• Location: Ducts of glands and tubular parts of nephrons.
• Function: Secretion & absorption

    iii. Columnar:

• Location: Lining of stomach and intestine.
• Function: Secretion & absorption

b. Compound (Multi-layered)

• Location: Skin, buccal cavity, pharynx, pancreatic ducts.
• Function: Protection.

Modification of columnar or cuboidal cells

i. Ciliated epithelium: 

• Bear cilia.
• Seen in bronchioles & fallopian tubes.
• Function: move substances over epithelium.

ii. Glandular epithelium: 

    For secretion.

    2 types: Unicellular (E.g. Goblet cells) & Multicellular (E.g. salivary glands).

    Based on mode of secretion, glands are 2 types:

• Exocrine glands: have ducts. E.g. Salivary gland.
• Endocrine glands: Ductless. Produce hormones.

Cell junctions 

The junctions that provide link between adjacent cells.

They are 3 types: 

1. Tight junction: Stop substances from leaking across a tissue.
2. Adhering junction: Perform cementing to keep neighbouring cells together.
3. Gap junction: For communication b/w adjoining cells by connecting cytoplasm for rapid transfer of ions, molecules etc.

2. Connective tissues 

3 Types: Loose, Dense & Specialised.

a. Loose CT

    Loosely packed Fibres and fibroblasts. 2 types: 

• Areolar: Under skin. Support for epithelium.
• Adipose: Under skin. Its cells (adipocytes) store fats.

b. Dense CT

    Compactly packed Fibres and fibroblasts. 

    2 types:

• Dense regular (Tendon & Ligament): 

            Collagen fibres are regular. 

            Tendon: Attach muscles to bones. 

            Ligament: Attach bone to bone.

• Dense irregular: Fibroblasts & fibres are irregular. Present in skin.

c. Specialized CT

    3 types: 

    i. Cartilage: 

        Pliable due to chondroitin salts. 

        Cartilage cells → chondrocytes.

    ii. Bone: 

        Non-pliable. Rich in calcium salts. 

        Bone cells → osteocytes.
        Function: Protection, support, locomotion.

    iii. Blood: 

        Fluid CT. 

        Circulation. 

3. Muscle tissues 

3 types: 

1. Skeletal (striated or voluntary): Attached to bones. Striations present.
2. Visceral (Non-striated/ smooth): Involuntary & fusiform. No striations. Found in blood vessels, stomach, intestine etc.
3. Cardiac: Involuntary. Seen in heart. Communication junctions (intercalated discs).

4. Neural tissue

Found in Neural system. 

Made up of neurons & Neuroglia.

MORPHOLOGY OF COCKROACH 

(Periplaneta americana) 

Chitinous exoskeleton (cuticle).

The body has 3 regions – head, thorax and abdomen.

Head: 

• Antennae, compound eyes. Biting & chewing mouth parts.
• Mouthparts: labrum (upper lip), 2 mandibles, 2 maxillae, hypopharynx (tongue) & a labium (lower lip).

Thorax: 

    3 parts: prothorax, mesothorax & metathorax.

    2 pairs of wings:

• Forewings (mesothoracic) or tegmina: Opaque, dark.
• Hind wings (metathoracic): Transparent, used in flight.

Abdomen: 10 segments. 

Differences between male & female cockroaches 

Male	Female
i. Wings beyond the tip of the abdomen.	Wings up to the tip of abdomen.
ii.  Anal styles present	Absent

ANATOMY OF COCKROACH 

Digestive system:

Alimentary canal has 3 parts: foregut, mid gut & hindgut.

• Foregut: Mouth → pharynx → oesophagus → crop (to store food) → gizzard (proventriculus- for grinding food).
• Mid gut (Mesenteron): 6-8 tubules (hepatic or gastric caecae) are seen at the junction of foregut & mid gut. They secrete digestive juice.
• Hindgut: It includes ileum, colon & rectum.

Excretory system:

• Uricotelic. 
• Excretory organ is Malpighian tubules.

Respiratory system:

• Trachea with 10 pairs spiracles. 
• Branches of tracheal tubes are tracheoles. 

Circulatory system:

• Open type.
• Haemolymph (blood)= colourless plasma + haemocytes.
• Blood from sinuses (haemocoel) → ostia → heart → anterior aorta → sinuses.

Nervous system: 

• 3 ganglia in thorax and 6 in the abdomen.
• The head holds only a bit of nervous system. So, if the head of cockroach is cut off, it will still live for one week.
• Supra-oesophageal ganglion (brain).

    Sense organs: 

• Antennae, eyes, maxillary palps, labial palps, anal cerci etc.
• Each compound eye has 2000 ommatidia. 
• Cockroach can receive several images of an object (mosaic vision).

Reproductive system:

A. Male reproductive system: 

• 2 testes, seminal vesicles, accessory glands & external genitalia (male gonapophysis or phallomeres).
• Testis → vas deferens → seminal vesicle → ejaculatory duct → male gonopore.
• Seminal vesicles: To store sperms. Sperms → spermatophores.
• Accessory glands: mushroom gland & phallic gland. They nourish the sperms.

B. Female reproductive system: 

• 2 large ovaries, oviducts, spermatheca, genital chamber, Colleterial glands etc.
• Each ovary has 8 ovarian tubules (ovarioles) containing developing ova.
• Oviducts unite into a median oviduct (vagina) → genital chamber.
• A pair of spermatheca is present. 
• Fertilised eggs are encased in oothecae.
• Development is paurometabolous (nymphal stage).

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