practicals XII



Experiment on Histology of Ovaries

  • Background Information: The production of eggs begins before birth with the development of oogonia, leading to primary oocytes that remain inactive during childhood.

  • Follicle Development:

    • Primordial Follicles: Approximately 2 million at birth, only 450 develop into secondary oocytes during a woman's reproductive years.

    • Graafian Follicle: A mature follicle (~1 cm diameter) containing a secondary oocyte.

    • Hormonal Influence: Estrogen is secreted by granulosa cells, promoting follicle growth.

  • Stages of Follicle Development:

    • Primary Follicle: Formation begins as granulosa cells multiply around primary oocytes.

    • Secondary Follicle: Fluid secretion leads to the formation of antrum, allowing further growth.

    • Mature Follicle: At ovulation, the primary oocyte undergoes meiosis I to form a haploid secondary oocyte and a polar body.

Menstrual Cycle

  • Phases:

    • Continuous cyclic changes occur from puberty to menopause.

    • Ovulation: Typically around day 14 of a 28-day cycle, one ovum is released from alternating ovaries.

    • Menstrual Cycle: Shedding of the proliferated uterine lining if no implantation follows ovulation.

    • Correlation with Hormones: Controlled by ovarian hormones, primarily during the conversion of the follicle into corpus luteum, which secretes progesterone.

Experiment on Chick Embryo Development

  • Background: Similarities in chick and mammalian embryonic development make chick embryos useful for study.

  • Key Stages:

    • Cleavage: From fertilization to formation of zygote and divisions leading to blastomeres.

    • Gastrulation: Formation of germ layers (ectoderm, mesoderm, endoderm).

    • Organogenesis: Development of body organs and structures.

  • Tools: Charts/models used to examine development; visual representation of stages for different vertebrates.

Data Collection: Blood Group Study

  • Experiment Goals: Assess blood group distribution in a class and visualize data using pie charts and histograms.

  • Variation:

    • Discontinuous Variation: Clear categories, e.g., blood types.

    • Continuous Variation: Range of traits like height.

  • Visualization: Use of bar graphs (histograms) and pie charts to represent relative frequencies and characteristics.

Questions & Answers: Key Concepts

  1. Genetics: Study of heredity and genetic variation.

  2. Blood Groups: Types based on antigens (A, B, AB, O).

  3. Universal Recipients/Donors: AB as universal recipients; O as universal donors.

  4. Fertilization: The union of sperm and egg.

  5. Rh Factor: Identifies blood groups minus (Rh-) and positive (Rh+).

  6. Adaptations of RBCs: Small size, biconcave shape, no nucleus for oxygen transport efficiency.

  7. Agglutination: Clumping of RBCs in mismatched transfusions.