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Unit 4 review

Apr 27, 2025

Lecture Notes: Mitosis, Meiosis, and Reproductive System

Mitosis vs. Meiosis

  • Mitosis: Chromosomes line up in single file and pull apart, resulting in two identical cells with 46 chromosomes each.
  • Meiosis:
    • Chromosomes line up as tetrads (four chromosomes), not single file.
    • Synapsis: Tetrads line up, allowing crossing over where chromosomes switch pieces, increasing genetic variation.
    • Results in genetically unique sperm cells.

Spermatogenesis and Spermiogenesis

  • Spermatogenesis: Formation of sperm cells occurring in the seminiferous tubules.
  • Spermiogenesis: Maturation of sperm in the epididymis (sperm develop tails and learn to swim).

Muscles Regulating Spermiogenesis

  • Cremaster Muscle: Elevates or depresses testes depending on temperature (acts like a hammock).
  • Dartos Muscle: Causes the skin to wrinkle, bringing testes closer or further from the body.

Hormones Initiating Puberty

  • GnRH (Gonadotropin-releasing hormone) from the hypothalamus starts puberty.
  • Pituitary releases FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone).

Fertilization and Early Embryonic Development

  • Fertilization usually occurs in the uterine tube.
  • Zygote develops and implants in the uterus.
  • Stages:
    • Zygote (fertilized egg)
    • Embryo (following cleavage)
    • Fetus (when bone cells start developing)

Male Reproductive Structure

  • Seminal Vesicles: Make seminal fluid.
  • Prostate: Produces prostatic fluid.
  • Ejaculatory Duct: Where sperm, seminal fluid, and prostatic fluid mix to form semen.
  • Bulbourethral (Cowper’s) Gland: Produces alkaline fluid to neutralize urine acidity.

Female Reproductive Structure

  • Clitoris: Erectile tissue analogous to the male penis.
  • Endometrium: The lining of the uterus, specifically the stratum functionalis is shed during menstruation.

Hormones and Ovulation

  • FSH: Stimulates follicle development.
  • LH Surge: Triggers ovulation.
  • Estrogen and Progesterone: Regulate the menstrual cycle.
  • HCG (Human Chorionic Gonadotropin): Maintains the corpus luteum during early pregnancy.

Pregnancy and Childbirth

  • Placenta: Provides nutrition, oxygen, and waste removal for the fetus.
  • Umbilical Cord: Connects fetus to placenta.
  • Cervix: Must dilate to 10 cm during childbirth.

Menstrual Cycle

  • Divided into phases: follicular phase, ovulation, luteal phase, and menstruation.
  • Progesterone maintains uterine lining post-ovulation.
  • Corpus Luteum: Degenerates if no pregnancy, leading to menstruation.

Key Terms and Concepts

  • Secondary Sex Characteristics: Traits such as breast development and facial hair growth.
  • Flagellum: Tail of sperm for motility.
  • Sertoli Cells: Protect immature sperm cells.
  • Erectile Tissue: Corpus spongiosum and corpus cavernosum in males.

Graph Analysis

  • GnRH: Initiates cycle, increases FSH and LH.
  • FSH: Stimulates follicle growth and estrogen production.
  • Estrogen Peak: Triggers LH surge, leading to ovulation.
  • Progesterone: Maintains uterine lining, decreases if no implantation.

These notes capture the key points discussed in the lecture, focusing on the biological processes of cell division, the endocrine regulation of reproduction, and the anatomy and physiology of the human reproductive systems.

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