L27 2025 – Genetics VII - Tagged

Page 1: Attendance

• Attendance recorded.

Page 2: Title Slide

• Main Topic: Mammalian Gametogenesis, Fertilisation, and Embryogenesis.

• Introduction to the session.

Page 3: Revision of Adult Human Reproductive Anatomy

• Review of previous session on molecular biology and anatomical development.

• Focus: Revision of adult human reproductive anatomy.

• Reference: Campbell Chapter 45 provides comprehensive coverage.

Page 4: Adult Anatomy (Females)

• Major Structures:

  • Oviduct

  • Ovaries

  • Uterine wall

  • Uterus

  • Cervix

  • Endometrium

  • Vagina

  • Follicles

  • Corpus luteum

Page 5: Female Reproductive System

• Diagram includes:

  • Rectum

  • Cervix

  • Vagina

  • Bartholin glands (Bulbourethral)

  • Vaginal opening

  • Other structures: Urethra, Clitoris, Labia minora, Labia majora, and Vulva.

• Description of Vagina as internal structure connecting vulva to cervix.

Page 6: Adult Anatomy (Males)

• Major Structures:

  • Seminal vesicle

  • Prostate gland

  • Urethra

  • Scrotum

  • Bulbourethral gland

  • Erectile tissue of penis

  • Vas deferens

  • Epididymis

  • Testis

Page 7: Male Reproductive System Anatomy

• Components include:

  • Seminal vesicle

  • Rectum

  • Vas deferens

  • Penis and its parts (e.g., Glans, Prepuce)

  • Description of ejaculation and fluid contributions from seminal vesicle, prostate, and bulbourethral glands.

Page 8: Meiosis Overview

• Brief note that the next topic will cover meiosis.

• Focus on sex-specific differences in meiosis for animals.

Page 9: Oogenesis vs. Spermatogenesis

• Timeframe of gametogenesis in females (puberty to menopause) vs. males (puberty onwards).

• Key points on the development of oocytes and sperm:

  • Birth arrest in prophase for oocytes.

  • Continuous production of sperm after puberty.

Page 10: Sex-specific Differences in Gametogenesis

• Modified female meiosis produces one large ovum and four smaller sperm.

• Ovum characteristics:

  • Approximately 10 million times the volume of sperm.

  • Contains maternal resources vital for early development.

• Characteristics of sperm:

  • Smallest human cell with nucleus, mitochondrion, and tail.

  • Continuous spermatogenesis in males.

Page 11: Testes Structure

• Structural components include:

  • Testis (x2)

  • Vas deferens

  • Epididymis

  • Duct system

  • Seminiferous tubules

Page 12: Cross-section of Seminiferous Tubule

• Description of sperm maturation process within seminiferous tubules.

Page 13: Spermatogenesis Basics

• Spermatogonia develop through mitosis and meiosis over ~70 days.

• Role of Sertoli cells in supporting spermatogenesis.

Page 14: Ovarian Cycle Overview

• Key phases and timings:

  • Days 0-1: Selection of primary oocyte.

  • Days 2-12: Growth and maturation of the follicle.

  • Day 14: Ovulation and completion of Meiosis I.

  • Days 15-26: Corpus luteum develops from follicle remnants.

  • Day 28: Breakdown of corpus luteum.

Page 15: Fertilization Process

• Sequence from ovulation to implantation:

  1. Ovulation

  2. Fertilization

  3. Cleavage begins

  4. Blastocyst implantation in the endometrium.

Page 16: Sperm Capacitation and Acrosome Reaction

• Importance of the acrosome in sperm function:

  • Acrosome contains hydrolytic enzymes for penetrating the egg.

  • Capacitation prepares sperms for successful fusion with the egg.

Page 17: Fertilisation Steps in Sea Urchin

• Sperm binding dynamics:

  • Reception by jelly coat, triggering acrosome reaction.

  • Cortical reaction prevents polyspermy after fertilization.

Page 18: Zona Pellucida Function

• Structure surrounding the ovum, similar to jelly coat.

• Binding molecules that initiate the acrosome reaction in sperm.

Page 19: The Blastocyst Formation

• Formation of the blastocyst:

  • Trophoblast (outer layer) and its role in implantation.

  • Inner cell mass developing into the embryo.

Page 20: Development Focus on Epiblast

• Most of the embryo derives from epiblast cells.

• Structures developed include placenta and umbilical cord from extra-embryonic tissues.

Page 21: Embryonic Development Comparison

• Differences in aquatic vs. terrestrial embryos:

  • Aquatic embryos simpler, while terrestrial embryos include necessary structures for survival.

Page 22: Cleavage Overview

• Description of cleavage as rapid cell division:

  • Creation of blastomeres forming the blastula.

Page 23: Early Blastula Stages

• Descriptions and images:

  • Stages from fertilization to early blastula formation.

  • Totipotency of early cells reduces as they differentiate.

Page 24: Developmental Adaptations of Amniotes

• Key adaptations:

  • Shelled eggs and uterus in vertebrates colonizing land.

  • The absorbable amniotic fluid.

  • Complex extraembryonic structures in mammals.

Page 25: Placenta's Role in Fetomaternal Exchange

• Placenta functions post 4-week development:

  • Secretion of hCG to maintain corpus luteum.

  • Hormonal changes and adjustments after early pregnancy.

Page 26: Maternal-fetal Blood Interaction

• Details on blood flow and substance exchange:

  • Significant surface area for transport.

  • Prevention of direct mixing of maternal and fetal blood.

Page 27: Immunology of Pregnancy

• Importance of immune regulation to avoid rejection:

  • Changes in immune response during pregnancy to prevent embryo rejection.

Page 28: Summary of Human Prenatal Development Timeline

• Key developmental milestones:

  • Day 1: Fertilization

  • Day 4: Embryo reaches uterus

  • Day 12: Implantation

  • Week 5: Placenta develops hormones

  • 1st trimester completion and ongoing development in subsequent trimesters.