Reproductive System II: Menstrual Cycle, Cellular Development, and Signs of Pregnancy

The Ovarian Cycle

  • The ovarian cycle refers to the cyclical changes occurring within the ovaries, which are regulated by hormones produced by the anterior pituitary gland.
  • These changes occur in direct response to two primary hormones:
    • Follicle-stimulating hormone (FSH).
    • Luteinizing hormone (LH).
  • The cycle is composed of two distinct phases, which are defined by the hormone that maintains dominant control during that time period:
    • Follicular Phase:
    • Primary Controlling Hormone: Follicle-stimulating hormone (FSH).
    • Duration: This phase encompasses days 11 to 1414 of a standard 2828-day cycle.
    • Luteal Phase:
    • Primary Controlling Hormone: Luteinizing hormone (LH).
    • Duration: This phase encompasses days 1515 to 2828 of the cycle.

The Uterine Cycle

  • The uterine cycle consists of physical changes that take place in the endometrium (the inner lining of the uterus).
  • These physiological changes occur in response to the fluctuations of the ovarian hormones:
    • Estrogen.
    • Progesterone.
  • The cycle is categorized into four sequential phases:
    • Menstrual Phase
    • Proliferative Phase
    • Secretory Phase
    • Ischemic Phase

Cellular Development and Genetics

  • Human biological development involves several types of cells and specific genetic structures:
    • Soma Cells: These are the cells that make up the various organs and bodily tissues of the human body.
    • Gametes: These are the germ cells or sex cells, which are located exclusively within the reproductive glands.
  • Chromosomal Structure and Inheritance:
    • The nucleus of a human cell contains 2323 pairs of chromosomes.
    • Inheritance is a dual-parental contribution: Each parent donates 11 part of the chromosome set.
    • A complete set for a developing human (referred to in the transcript as "little Mikey") consists of 4646 chromosomes.
  • Types of Chromosomes:
    • Autosomes: Each parent donates 2222 pairs of autosomes. These chromosomes carry the genetic code for specific traits, such as:
    • Eye color.
    • Hair color.
    • Ear wax consistency.
    • Sex Chromosomes: There is 11 pair of sex chromosomes that determines biological sex.

Stages of Fetal Development

  • Fetal development is divided into three major chronological stages throughout gestation:
    • Pre-embryonic Stage: Spans from 33 to 44 weeks of gestation.
    • Embryonic Stage: Spans from 55 to 1010 weeks of gestation.
    • Fetal Stage: Spans from 1111 to 4040 weeks of gestation.

Signs of Pregnancy

  • There are three distinct categories used to classify the clinical signs and symptoms of pregnancy, varying by certainty and data source:
    • Presumptive Signs:
    • These consist of subjective data reported by the woman to a Healthcare Provider (HCP).
    • Example: A patient reporting, ‘My breasts hurt.’
    • Probable Signs:
    • These consist of objective clinical data observed by a professional during an examination.
    • Example: Identifying objective cervical changes.
    • Positive Signs:
    • These are diagnostic confirmations that definitively prove the presence of a pregnancy.
    • Examples:
      • Detection of the fetal heartbeat.
      • Visualization of the fetus via ultrasound.