Human Reproductive Biology Quiz
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Questions and Answers

What is the primary purpose of meiotic divisions during gametogenesis?

  • To reduce the chromosomal number from diploid to haploid (correct)
  • To enhance the size of germ cells
  • To facilitate morphological changes in germ cells
  • To maintain the diploid chromosomal number

Which statement best describes the transformation of male germ cells during spermatogenesis?

  • They undergo mitotic division to remain diploid.
  • They lose most of their cytoplasm and form a definitive structure. (correct)
  • They remain large and round throughout the process.
  • They develop a head, neck, and tail through gradual protein synthesis.

At what stage do primary spermatocytes undergo their first meiotic division?

  • During the process of spermiogenesis
  • Immediately following fertilization
  • After transformation from spermatogonia (correct)
  • Prior to mitotic divisions of spermatogonia

What morphological change do female germ cells undergo during gametogenesis?

<p>They gradually increase in size due to cytoplasmic growth. (A)</p> Signup and view all the answers

Which of the following best describes spermiogenesis?

<p>The maturation process where spermatids develop into mature spermatozoa. (B)</p> Signup and view all the answers

During which phase of the menstrual cycle does implantation occur?

<p>Secretory phase (C)</p> Signup and view all the answers

Which type of implantation is considered the most dangerous?

<p>Tubal implantation (B)</p> Signup and view all the answers

What is the primary role of early pregnancy factor (EPF) in pregnancy?

<p>To serve as a basis for pregnancy testing (B)</p> Signup and view all the answers

Which hormone's high levels in urine form the basis for a pregnancy diagnostic test by the end of the second week?

<p>Chorionic gonadotrophic hormone (B)</p> Signup and view all the answers

Which phase does the uterine endometrium not undergo during the menstrual cycle?

<p>Pre-ovulatory phase (C)</p> Signup and view all the answers

What can inhibit implantation in the event of conception?

<p>High doses of hormone combinations (B)</p> Signup and view all the answers

Where does the implantation typically occur in the uterus?

<p>Near the fundus (A)</p> Signup and view all the answers

Which of the following is a characteristic of the menstrual phase?

<p>Endometrial glands disintegrate (C)</p> Signup and view all the answers

What primarily occurs during the ovarian cycle in response to GnRH from the hypothalamus?

<p>Secretion of gonadotrophins FSH and LH (A)</p> Signup and view all the answers

What is formed from the notochordal plate during development?

<p>Notochord (D)</p> Signup and view all the answers

During which phase does the secondary oocyte complete the second meiotic division?

<p>After fertilization (A)</p> Signup and view all the answers

What occurs during the invagination process at the primitive streak?

<p>Cells separate from the epiblast and move downward (A)</p> Signup and view all the answers

Which of the following statements about granulosa cells and the cumulus oophorus is true?

<p>Cumulus oophorus is formed by intact granulosa cells during maturation (C)</p> Signup and view all the answers

What happens to the majority of follicles developed during an ovarian cycle?

<p>They degenerate and become atretic (C)</p> Signup and view all the answers

What indicates the future site of the vertebral bodies?

<p>Notochord (A)</p> Signup and view all the answers

Which of the following structures temporarily connects the yolk sac and amniotic cavity?

<p>Neurenteric canal (B)</p> Signup and view all the answers

What event triggers the maturation of the follicle and subsequent ovulation?

<p>Increase in LH levels (B)</p> Signup and view all the answers

During which week of development does the primitive streak begin to appear?

<p>3rd week (A)</p> Signup and view all the answers

Which of the following best describes the state of primary oocytes by the onset of puberty?

<p>Only 40,000 remain present (C)</p> Signup and view all the answers

Which cells are primarily responsible for estrogen production during follicle development?

<p>Theca and follicular cells (D)</p> Signup and view all the answers

What happens to the notochord in the region of the vertebral bodies as the vertebral column forms?

<p>It disappears but persists as the nucleus pulposus (B)</p> Signup and view all the answers

Which of the following regions does NOT have secondary mesoderm spread over it?

<p>Prechordal plate (A), Region of the notochord (D)</p> Signup and view all the answers

What is the outcome for oocytes that are not fertilized within 24 hours after ovulation?

<p>They degenerate (D)</p> Signup and view all the answers

What is the primary function of the notochord during embryonic development?

<p>Support and organize the embryo (B)</p> Signup and view all the answers

Which division of the secondary mesoderm is responsible for forming the skeletal muscles of the trunk and limbs?

<p>Paraxial mesoderm (C)</p> Signup and view all the answers

What structure is formed from the ventral portion of somites?

<p>Vertebral body (A)</p> Signup and view all the answers

Which type of mesoderm is situated lateral to the intermediate mesoderm?

<p>Lateral plate mesoderm (D)</p> Signup and view all the answers

Which of the following structures is NOT formed by derivatives of the lateral plate mesoderm?

<p>Skeleton except skull (B)</p> Signup and view all the answers

At which day does the first pair of somites appear in the cervical region?

<p>20th day (A)</p> Signup and view all the answers

How many pairs of somites are typically present by the end of the 5th week?

<p>42 - 44 pairs (B)</p> Signup and view all the answers

Which embryonic structure does NOT correspond to a subdivision of the secondary mesoderm?

<p>Somatopleuric mesoderm (A)</p> Signup and view all the answers

What does the term somite refer to in embryonic development?

<p>A segment of paraxial mesoderm (B)</p> Signup and view all the answers

What is the primary function of the myotome?

<p>Forming skeletal muscles (D)</p> Signup and view all the answers

Which component is exclusively formed by the sclerotome?

<p>Cartilage and bone (B)</p> Signup and view all the answers

Which of the following is NOT a derivative of the ectoderm?

<p>Dermis of the skin (D)</p> Signup and view all the answers

Which mesodermal component is responsible for developing the urogenital system?

<p>Intermediate mesoderm (C)</p> Signup and view all the answers

What function do fetal membranes serve during embryonic development?

<p>Providing growth and survival of the embryo (D)</p> Signup and view all the answers

From which germ layer does the thyroid gland develop?

<p>Endoderm (A)</p> Signup and view all the answers

Which of the following structures is derived from mesoderm?

<p>Urogenital system (B)</p> Signup and view all the answers

Which of the following statements about the dermatome is correct?

<p>It gives rise to dermis and subcutaneous tissue. (C)</p> Signup and view all the answers

Flashcards

Gametogenesis

The process of creating haploid (23 chromosomes) gametes from diploid (46 chromosomes) germ cells through meiotic divisions and morphological changes.

Spermatogenesis

The process of producing mature sperm in the seminiferous tubules of the testes. It involves multiple stages, from primordial germ cells to spermatogonia, spermatocytes, spermatids, and finally, mature spermatozoa.

What is the purpose of meiotic divisions in gametogenesis?

The reduction in the number of chromosomes from diploid (46) to haploid (23) during gametogenesis. This ensures each gamete contributes half the chromosomes needed for a zygote.

Describe the morphological changes during spermatogenesis.

Morphological changes during spermatogenesis include the formation of a head (containing condensed DNA), neck, middle piece (with mitochondria for energy), and tail (for movement). Most cytoplasm is shed.

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When does spermatogenesis begin?

Spermatogenesis begins at puberty, when primordial germ cells differentiate into spermatogonia. These cells multiply through mitosis, leading to the development of mature sperm.

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Cumulus Oophorus

The collection of granulosa cells surrounding the oocyte in a developing follicle.

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Graafian follicle

A mature follicle, characterized by a large antrum filled with fluid and a prominent oocyte.

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Follicle Maturation

The process of follicle development where the primary oocyte continues through the first meiotic division.

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Atresia

A phenomenon where follicles start to develop but only one reaches full maturity while others degenerate.

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Follicle-Stimulating Hormone (FSH)

The hormone responsible for stimulating the growth of ovarian follicles, particularly in the early stages of the ovarian cycle.

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Luteinizing Hormone (LH)

The hormone responsible for final follicle maturation and triggering ovulation.

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Ovulation

The rupture of a Graafian follicle and the release of a secondary oocyte.

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Corpus Luteum

The site of the ruptured Graafian follicle after ovulation, which transforms into a temporary endocrine gland producing hormones like progesterone.

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Implantation

The process of the early blastocyst embedding into the uterine wall, marking the beginning of pregnancy.

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Where does implantation usually occur?

The site where implantation typically occurs, usually on the posterior or anterior wall of the uterus near the fundus.

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Menstrual Cycle

The cyclical changes in the endometrium of the uterus, occurring roughly every 28 days, from puberty to menopause.

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Secretory Phase

The phase of the menstrual cycle when the endometrium prepares for potential implantation of a fertilized egg.

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Ectopic Pregnancy

A pregnancy that occurs outside of the uterus, often in the fallopian tubes.

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Placenta Previa

A condition where the placenta implants too close to the cervix, potentially blocking the birth canal.

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Early Pregnancy Factor (EPF)

A protein secreted by the trophoblast after fertilization, used in early pregnancy tests.

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Chorionic Gonadotrophic Hormones

Hormones produced by the developing placenta, detected in urine for pregnancy tests.

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What is the notochord?

The notochord is a flexible rod-like structure that forms during embryonic development. It's composed of cells that support the embryo and serve as the future site for the vertebral bodies.

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How does the notochord form?

The notochord forms from the notochordal plate, which itself arises from the notochordal process. It's like a transformation process: process to plate to chord.

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Where does the notochord disappear?

The notochord disappears in most areas of the vertebral column, but persists as the nucleus pulposus in the intervertebral discs, which are the cushions between vertebrae.

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What is secondary mesoderm?

Secondary mesoderm, also known as intraembryonic mesoderm, is a vital layer in the developing embryo that gives rise to various organs and systems.

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How does secondary mesoderm form?

Secondary mesoderm arises from the migration of cells from the epiblast through the primitive streak.

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What is the primitive streak?

The primitive streak is a transient structure that appears during the third week of development and is essential for the formation of secondary mesoderm.

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When does the primitive streak disappear?

The migration of cells through the primitive streak ceases by the end of the fourth week, after which the streak disappears.

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Where does secondary mesoderm spread?

The secondary mesoderm spreads throughout the embryonic disc, but there are exceptions: it's absent in the midline region of the notochord and the prechordal plate.

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Somite

A somite is a segment of mesoderm that forms during embryonic development. Each somite gives rise to three distinct structures:

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Myotome

Forms the skeletal muscles, responsible for movement.

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Dermatome

Forms the dermis and subcutaneous tissue, responsible for skin structure and insulation.

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Sclerotome

Forms cartilage and bones, providing support and structure.

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Germ Layers

The three germ layers are ectoderm, mesoderm, and endoderm. These layers give rise to all tissues and organs of the body.

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Surface ectoderm

Forms the outer layer of the skin, hair, nails, and some glands.

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Neuroectoderm

Forms the nervous system, including the brain and spinal cord.

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Paraxial mesoderm

Forms muscles, bones, connective tissue, and the dermis of the skin.

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What are the three subdivisions of the secondary mesoderm?

The secondary mesoderm, essential for development, splits into three critical regions: paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm. Each region contributes to different bodily structures.

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What are the derivatives of the paraxial mesoderm?

Paraxial mesoderm, lying close to the midline, is responsible for forming various structures including the skeleton (except the skull), head muscles, skeletal muscles in the trunk and limbs, the dermis of the skin, and connective tissue.

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What does the intermediate mesoderm develop into?

Intermediate mesoderm, positioned lateral to the paraxial mesoderm, gives rise to the urogenital system, which encompasses the kidneys, gonads, and their associated ducts.

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What structures arise from the lateral plate mesoderm?

Lateral plate mesoderm, the outermost layer of secondary mesoderm, differentiates into many structures including the serous membranes (lining the heart, lungs, and abdominal cavity), the primitive heart, blood and lymph cells, connective tissue and muscles of internal organs, the spleen, and the adrenal cortex.

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What are somitomeres?

Somitomeres are segments of paraxial mesoderm that form along the developing neural tube. They are precursors to somites, which are organized units that further differentiate into specific structures.

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How do somites form?

Somitomeres, except the first seven pairs, transform into somites. These segmental blocks of tissue contribute to the axial skeleton by forming the vertebrae, as well as developing the dermis and muscles.

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What are sclerotomes and what do they form?

The ventral portion of a somite, known as the sclerotome, encloses the notochord and eventually forms the vertebral body, while the dorsal portion forms the vertebral arch.

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What is a dermomyotome and what does it become?

The dorsal portion of the somite, called the dermomyotome, differentiates into the dermis of the skin and the muscles of the back.

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Study Notes

General Embryology

  • This document covers general principles of embryology, including various stages and processes.
  • It provides detailed information on gametogenesis, ovarian cycle, fertilization, cleavage, implantation, formation of germ layers, fetal membranes, placenta, fetal period, multiple pregnancy, and teratogenesis.

Gametogenesis

  • Gametogenesis is the process by which male and female germ cells undergo chromosomal and morphological changes.
  • Chromosomal changes reduce the diploid number of chromosomes to haploid.
  • Morphological changes alter the size and shape of the germ cells.

Ovarian Cycle

  • The ovarian cycle is a cyclical process controlled by the hypothalamus and pituitary gland.
  • Follicular and theca cells produce estrogen, which stimulates the pituitary to secrete LH.
  • LH causes follicle maturation and oocyte shedding.

Fertilization

  • It's the fusion of male and female gametes to form a zygote.
  • Sperm transport involves flagella and muscular contractions through the female reproductive tract.
  • The oocyte is transported by fimbriae and cilia, moving towards the uterine cavity.
  • Sperm maturation involves capacitation (removal of glycoprotein coat) and acrosome reaction (release of acrosomal enzymes).
  • Fertilization phases include penetration of the corona radiata and zona pellucida, and fusion of oocyte and sperm cell membranes.

Cleavage

  • The single-celled zygote undergoes mitotic divisions.
  • It increases the number of cells (blastomeres).
  • Cleavage begins 30 hours after fertilization.
  • Zygote is within the zona pellucida during cleavage.

Implantation

  • Implantation is the embedding of the blastocyst into the uterine endometrium.
  • Site of implantation is typically the posterior or anterior wall of the uterus near the fundus.
  • The endometrium is in the secretory phase at the time of implantation.
  • Abnormal sites of implantation include ectopic pregnancy (outside the uterus).

Formation Of Germ Layers

  • During gastrulation, three germ layers, ectoderm, mesoderm, and endoderm, are established.
  • The primitive streak appears on the surface of the epiblast.
  • Cells migrate into the primitive streak, forming the endoderm and mesoderm.
  • Cells remaining in the epiblast form the ectoderm.

Fetal Membranes

  • Tissues and structures, derived from the zygote, that support development until birth are fetal membranes.
  • They include the yolk sac, amnion, chorion, allantois, umbilical cord, and placenta.
  • Placenta develops to connect the embryo to the mother for nutrition exchange.
  • It is a feto-maternal organ about 15-25cm in diameter.
  • Maternal surface is irregular, with lobules (cotyledons).
  • Fetal surface is smooth, with the umbilical cord attachment.

Placenta

  • The placenta supports the fetus during pregnancy for gas and nutrient exchange.
  • Maternal portion is derived from the decidua basalis, while the fetal portion from the chorion frondosum.
  • The chorionic villi extend into the decidua basalis, forming maternal-fetal exchange areas (intervillous spaces).

Fetal Period

  • The fetal period (weeks 9-40) is characterized by the maturation of tissues and organs, and rapid growth.
  • The fetus's size (CRL or CHL) is a measure of development.
  • Many noticeable changes in the structure of the body and systems occur during this stage.

Multiple Pregnancy

  • Multiple pregnancies (twins, triplets etc) result from the fertilization of multiple eggs (dizygotic) or a single fertilized egg that splits (monozygotic).
  • Monozygotic twins share a common placenta.
  • Dizygotic twins have separate placentas.

Teratogenesis

  • Teratology is the study of abnormalities due to birth defects.
  • Causes include genetic, environmental factors.
  • There are four major categories of abnormalities:
    • Malformations
    • Disruptions
    • Deformations
    • Syndromes

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General Embryology PDF

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Test your knowledge on human reproductive biology, focusing on gametogenesis, spermatogenesis, and the menstrual cycle. This quiz covers key concepts such as meiotic divisions, implantation stages, and hormonal roles in pregnancy. Challenge yourself and see how well you understand these essential biological processes!

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