STRUCTURAL ORGANISATION IN ANIMALS

 

Smooth muscle :

  • The smooth muscle fibres tapers or pointed at both ends
  • Do not show cross striation.
  • Cell junctions hold them together.
  • They are bundled together in a connective tissue sheath.
  • Present in wall of blood vessels, stomach and intestine.
  • They are involuntary in nature.

Cardiac muscles:

  • Contractile muscular tissue present in heart.
  • Cell junctions fuse the plasma membranes of cardiac muscles cells and make them stick together.
  • Communication junction or intercalated discs at some fusion points allow the cells to contract as a unit.
  • Muscle cells are branched and Uninucleated.

Neural tissues:

  • Neural tissues exert greatest control over body’s response to changing condition.
  • Neurons are the units of nervous tissues.
  • Neuroglial cells non-conducting and protects and support neurons.
  • Neuroglia makes up more than one-half the volume of neural tissue.
  • Electrical impulse is conducted through the plasma membrane of neuron.

EARTHWORM :

Morphology :

  • Earthworm has long cylindrical body.
  • The body divided into more than 100 equal segments called metamere.
  • Mid-dorsal dark line indicates the dorsal blood vessel.
  • The ventral surface is distinguished by genital openings.
  • Anterior end consists of the mouth and prostomium.
  • The first segment is called peristomium, which contain the mouth.
  • In matured worm, segments 14-16 are covered by dark band of glandular tissue called clitellum.
  • Body divisible into:
    • Preclitellar.
    • Clitellar.
    • Postclitellar

  • External apertures:
    • Four pairs of spermathecal aperture 5th – 9th segments.
    • A female genital aperture- 14th segment.
    • A pair of male genital apertures in 18th segment.
    • Numerous nephridial pores on the skin of each segment.

  • There are row of S- shaped Setae in each segment except 1st and last segment.
  • Setae have principal role in locomotion.

ANATOMY :

Body wall :

  • Body wall externally covered by thin non-cellular cuticle.
  • Body wall contains epidermis below cuticle.
  • Epidermis is made of single layer of columnar epithelium with secretory glands.
  • Two layers of muscles (circular and longitudinal).

Digestive system:

  • Alimentary canal is a straight tube between 1st and last segment.
  • Mouth present in the 1st segment.
  • Mouth opens into buccal cavity 1-3 segments.
  • Buccal cavity leads into muscular pharynx in 4th segment.
  • Narrow oesophagus at 5-7 segments.
  • Muscular gizzard in 8-9 segments helps in grinding of ingested food.
  • Stomach extended from 9-14 segments.
  • Calciferous gland present in the stomach, neutralize the acidic nature of humic acid present in the humus.
  • Intestine starts from 15th segment and continues till last segment.
  • A pair of Intestinal caecae present in the 26th segment.
  • Presence of internal median fold of dorsal wall of intestine called typhlosole between 26-35 segments.
  • Typhlosole increases the surface area for absorption.
  • Intestine opens to outside by means of anus.

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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