9)Preformationism vs Epigenesis Theory

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Who proposed the theory of epigenesis?

Karl Ernst von Baer

Aristotle (correct)

Nicolaas Hartsoeker

William Harvey

What process produces haploid male and female germ cells?

Fertilization

Oogenesis

Gametogenesis (correct)

Spermatogenesis

Which scientist proved the theory of epigenesis with the discovery of the mammalian ovum?

Karl Ernst von Baer (correct)

Aristotle

Nicolaas Hartsoeker

William Harvey

What is the process of formation of sperm cells called?

Spermatogenesis Signup and view all the answers

What is the term for the merging of male and female germ cells?

Fertilization Signup and view all the answers

What is the term for the new structure formed by the combination of male and female cells?

Zygote Signup and view all the answers

What is the term used to describe the embryo after 3 months of development?

Fetus Signup and view all the answers

Which of the following is not a part of the conceptus?

Placenta Signup and view all the answers

What is the term used to describe the period after birth?

Postnatal period Signup and view all the answers

What is the term used to describe the period between 12-15 years of age?

Puberty Signup and view all the answers

What is the term used to describe the process of formation and development of specialized generative cells, gametes?

Gametogenesis Signup and view all the answers

What is the chromosome number of gametes after meiosis?

23N Signup and view all the answers

What is the main function of the acrosome in a sperm cell?

To help the sperm penetrate the egg's outer layer Signup and view all the answers

During which phase of spermiogenesis is the unneeded cytoplasm shed from each spermatozoon?

Maturation phase Signup and view all the answers

Which of the following is not a function of the female reproductive system?

Producing male hormones Signup and view all the answers

How do females and males differ in their ability to produce gametes?

Males can produce sperm throughout their lives, while females can only produce a finite number of eggs Signup and view all the answers

What is the main function of the mitochondria in the midpiece of a sperm cell?

To provide energy for the sperm's flagellum Signup and view all the answers

What is the purpose of the uterine tubes in the female reproductive system?

To transport the eggs from the ovaries to the uterus Signup and view all the answers

What is the fluid-filled cavity known as?

Blastocoel Signup and view all the answers

Which layer surrounds the cavity in the blastocyst?

Trophoblast Signup and view all the answers

When does implantation begin?

5-6 days after fertilization Signup and view all the answers

What is the primary function of syncytiotrophoblast?

Invasion of maternal tissues Signup and view all the answers

At what stage does the embryo enter the blastocyst stage of development?

Blastocyst Signup and view all the answers

During diagnostic amniocentesis, what is the purpose of taking up amniotic fluid?

To analyze biochemistry and genetics Signup and view all the answers

During which phase of the ovarian cycle does the release of the oocyte from the mature follicle occur?

Ovulatory phase Signup and view all the answers

What hormone is responsible for the initial growth of primordial follicles in the ovary?

Follicle-stimulating hormone (FSH) Signup and view all the answers

What happens to the secondary oocyte if it is not fertilized?

It remains arrested in Metaphase II Signup and view all the answers

Which structure is formed in the ovary after ovulation and plays a role in producing progesterone?

Corpus Luteum Signup and view all the answers

Which two hormones control the monthly changes in the ovary and uterus during a woman's reproductive life?

FSH and LH Signup and view all the answers

What is the fate of a primordial follicle that begins a process of follicular growth?

It develops into a mature follicle Signup and view all the answers

Study Notes

Preformationism Theory

Nicolaas Hartsoeker's 1656 sketch of the homunculus, a tiny preformed human believed to exist in the head of spermatozoa

Epigenesis

William Harvey's accepted theory of development from a seed or egg in a sequence of steps
Originally proposed by Aristotle 2,000 years earlier
Modern embryology developed from Karl Ernst von Baer's work, who proved epigenesis with his discovery of the mammalian ovum (egg) in 1827

Terminology in Embryology

Gametogenesis: Production and development of haploid male and female germ cells
Spermatogenesis: Process of formation of sperms (testes)
Oogenesis: Process of formation of ovum (ovary)
Coitus: Sexual intercourse
Fertilization: Merging of male and female germ cells
Zygote: New structure formed by combination of male and female cells
Blastocyst: Hollow structure in 1st and 2nd weeks
Gastrula: 3-layer (trilaminar disc) disc formation in 3-week embryo
Embryo: Embryo in the first 3 months
Fetus: Embryo after 3 months
Conceptus: Fetus with all additional membranes (vitellus amnion-umblical cord-chorion)

Terminology in Embryology-2

Abortion: Birth before 20 weeks (a- spontaneous, b- therapeutic)
Trimester: Clinically divided 9 months of pregnancy into 3 months
Organogenesis: Differentiation of organs
Prenatal Period: Period before birth
Postnatal Period: Period after birth
Newborn: First 4 weeks after birth
Infantile (infancy): Period from birth to the end of first year
Childhood: Period between 2 to 12 years
Puberty: Period between 12-15 years
Adolescence: 3-4 years after puberty
Adulthood: Period between 20-60 years
Senility: Period after 60 years and older

Gametogenesis

Process of formation and development of specialized generative cells, gametes
Involves reduction of chromosome number by half during meiosis
Gamete maturation called spermatogenesis in males and oogenesis in females
Acrosome: Specialized type of lysosome containing hydrolytic enzymes
Sperm Morphology: Adapted for reaching and fertilizing the egg

Female Reproductive System

Produces female gametes (oocytes), provides environment for fertilization, and holds embryo during development until birth
Ovaries produce eggs (oocytes) and hormones
Uterine tubes transport eggs
Uterus: Site of embryonal and fetal development
Vagina: Birth canal

Ovaries

Covering: Simple cuboidal epithelium (Germinal Epithelium) and dense connective tissue (Tunica Albuginea)
Secondary oocyte begins Meiosis II, but stops in Metaphase II
Secondary oocyte is ovulated, Meiosis II is completed only if fertilized, forming a zygote

Ovarian and Menstrual Cycle

Monthly changes occur in ovary and uterus under control of FSH and LH secreted from pituitary gland
Ovarian cycle: Follicular phase (FSH), Ovulatory phase (LH), Luteal phase (LH)

Follicular Growth & Development

Begins in puberty with release of FSH from pituitary
Growth of oocyte, proliferation and changes in follicular cells, and stromal fibroblasts around each follicle

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the contrasting theories of preformationism and epigenesis in developmental biology, including the historical background, key proponents, and fundamental concepts. Learn about Nicolaas Hartsoeker's homunculus theory and William Harvey's contributions to the epigenesis theory.