Anatomy of Cockroach

Anatomy of Cockroach

• Brood pouch is absent.

• Digestive system:

  • Alimentary canal has three parts: foregut, midgut, and hindgut.
  • Foregut:
    • Mouth, pharynx, esophagus, crop, and gizzard.
    • Lined by cuticle.
    • Crop is used to store food.
    • Gizzard grinds food.
    • Gizzard has an outer layer of thick circular muscles and a thick inner cuticle forming six chitinous plates (teeth).
  • Midgut (Mesenteron):
    • Not lined by cuticle.
    • Has 6-8 tubules (hepatic or gastric caecae) at the junction of the foregut and midgut.
    • They secrete digestive juice.
    • 100-150 yellow-colored thin filamentous Malpighian tubules are present at the junction of the midgut and hindgut.
  • Hindgut:
    • Broader than the midgut and lined internally by cuticle.
    • Includes the ileum, colon, and rectum.
    • Rectum opens through the anus.

• Mouthparts: Labrum (upper lip), two mandibles, two maxillae, hypopharynx (tongue), and a labium (lower lip).

• Thorax:

  • Has three parts: prothorax, mesothorax, and metathorax.
  • The head is connected to the thorax by a neck (short extension of the prothorax).

• Circulatory system: Open type blood vascular system.

• Testes: Located laterally in the 4th to 6th abdominal segments.

Morphology and Anatomy of Earthworm

• Systematic position: Phylum Chordata.

• Epidermis: Single layer of columnar epithelial cells with secretory gland cells.

• Nervous system:

  • Segmentally arranged ganglia on the ventral paired and fused nerve cord.
  • The nerve cord in the anterior region (3rd and 4th segments) divides and encircles the pharynx, joining the cerebral ganglia dorsally to form a nerve ring.
  • The nerve ring with the cerebral ganglia represents the brain.
  • Sensory system: Light and touch-sensitive receptor cells, no eyes; chemoreceptors (taste receptors): react to chemical stimuli.

• Reproductive system:

  • Hermaphrodite.
  • Male reproductive organs:
    • Paired testes: Attached to the inter-segmental septum of the 10th and 11th segments.
    • Funnels: Connect to the tubular part of the nephridium which delivers wastes into the digestive tube.
  • Female reproductive organs:
    • Paired ovaries: Attached at the inter-segmental septum of the 12th and 13th segments.
    • Ovarian funnels: Present beneath the ovaries and continue into the oviduct, joining together and opening on the ventral side as a single median female genital pore on the 14th segment.

• Mating process:

  • Two worms exchange sperms.
  • Worms mate juxtaposing opposite gonadal openings, exchanging spermatophores (packets of sperms).

• Fertilization and development:

  • Mature sperm, ova, and nutritive fluid are deposited in cocoons produced by gland cells of the clitellum.
  • The cocoon with fertilized ova slips off and deposits in the soil.
  • After three weeks, the cocoon produces 2-20 baby worms (no larva).

Economic Importance of Earthworms

• Known as "friends of farmers" because they make burrows in the soil, making it porous.
• This helps with soil respiration and penetration of plant roots.
• Vermicomposting is the process of increasing soil fertility through earthworms.
• Used as bait in game fishing.

Morphology and Anatomy of Frog

• Systematic position: Phylum Chordata.

• Digestion: Gastric juice and HCl secreted from the gastric wall digest food. Partially digested food (chyme) is passed from the stomach to the duodenum.