Reproductive Systems and Gametogenesis

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Questions and Answers

What does CRL stand for in the context of embryonic measurements?

Crown Radii Length

Crown Head Length

Crown Heel Length

Crown Rump Length (correct)

What are the primary germ layers in embryonic development?

Neuroectoderm, endoderm, and ectoderm

Somites, dermatomes, and myotomes

Ectoderm, mesoderm, and endoderm (correct)

Epidermis, mesoderm, and neural crest

What developmental stage is referred to as a fetus?

From the ninth week of pregnancy until birth (correct)

From the first week to the eighth week of pregnancy

From the moment of conception until birth

From the fourth week until the tenth week of pregnancy

Which structures are derived from the parasympathetic mesoderm?

Vertebrae and ribs Signup and view all the answers

What condition does having only one umbilical artery potentially indicate?

Increased risk of congenital anomalies Signup and view all the answers

What is the most likely explanation for bleeding in the last trimester of pregnancy?

Placental abruption or previa Signup and view all the answers

How many pairs of somites are present by the end of the fifth week of development?

44 Signup and view all the answers

Which component provides the epidermis of the skin?

Dermoectoderm Signup and view all the answers

Where is the most common site of ectopic pregnancy implantation?

Fallopian tube Signup and view all the answers

What is the role of the intraembryonic celom?

To give rise to body cavities Signup and view all the answers

What characterizes the fetal side of the placenta?

Smooth and covered by amniotic membrane Signup and view all the answers

What does the lateral plate mesoderm differentiate into?

Visceral and parietal layers Signup and view all the answers

What are the primary sex organs responsible for producing gametes in males and females?

Testes and ovaries Signup and view all the answers

Which of the following correctly describes the female gamete?

Secondary oocyte Signup and view all the answers

What is the average weight of a full-term placenta?

500 g Signup and view all the answers

What is the significance of fertilization in terms of chromosomal composition?

It restores the diploid number of chromosomes Signup and view all the answers

During which phase of the menstrual cycle does the endometrium thicken in preparation for potential implantation?

Proliferative phase Signup and view all the answers

What happens during the cleavage stage of embryonic development?

Mitosis of the zygote into blastomeres Signup and view all the answers

Where does fertilization typically occur in the female reproductive system?

Ampulla of the uterine tube Signup and view all the answers

Which layer forms the inner lining of the uterus?

Endometrium Signup and view all the answers

What chromosomal composition does a typical gamete contain?

22 autosomes and 1 sex chromosome Signup and view all the answers

What is the significance of the primitive streak in embryonic development?

It is the site of gastrulation. Signup and view all the answers

Which statement correctly describes the notochord?

It develops from the primitive node. Signup and view all the answers

What structure replaces the notochord in adult humans?

Nucleus pulposus Signup and view all the answers

What marks the changes of the embryonic disc into a cylindrical structure?

Embryonic folding Signup and view all the answers

Which germ layer is formed by the displacement of the hypoblast by epiblast cells?

Endoderm Signup and view all the answers

What is the role of chorionic villi at the end of the third week?

To develop into tertiary chorionic villi. Signup and view all the answers

During the folding of the embryo, which aspect of development is notably modified?

Formation of the tail and head folds. Signup and view all the answers

How does the embryonic disc change shape during the third week?

It elongates with a broad cephalic and narrow caudal end. Signup and view all the answers

What forms from the outer cells of the morula during the first week of pregnancy?

Trophoblast Signup and view all the answers

Where is the common site of implantation in the uterus?

Upper posterior wall of the fundus Signup and view all the answers

What is the name of the process where a cavity develops inside the morula during the second week?

Blastogenesis Signup and view all the answers

What do the cells of the wall of the umbilical vesicle produce?

Extraembryonic mesoderm Signup and view all the answers

What fills the defect left by the embedded blastocyst in the endometrium by the 10th day?

Closing plug Signup and view all the answers

What are the two layers formed from the embryoblast during the early stages of the second week?

Hypoblast and epiblast Signup and view all the answers

Which layer of the trophoblast develops into the syncytiotrophoblast during the second week?

Cytotrophoblast Signup and view all the answers

What signifies the beginning of gastrulation in the development process?

Formation of the primitive streak Signup and view all the answers

What is the primary function of the placenta related to metabolism?

Synthesizing glycogen and fatty acids Signup and view all the answers

What condition results from abnormal implantation of the placenta inside the endometrium?

Placenta previa Signup and view all the answers

What significant change occurs to the placental membrane in the last trimester of pregnancy?

It reduces to two layers Signup and view all the answers

What is hydramnios characterized by?

Excessive amniotic fluid over 1500-2000 ml Signup and view all the answers

What structure is responsible for maintaining homeostasis of fluid and electrolytes around the embryo?

Amnion Signup and view all the answers

Which type of twins originate from two separate zygotes?

Dizygotic twins Signup and view all the answers

At full term, what is the approximate length of the umbilical cord?

50 cm Signup and view all the answers

What is the expected date of delivery of a fetus calculated from fertilization?

38 weeks ± 2 weeks Signup and view all the answers

Study Notes

A. Reproductive Systems

The female reproductive system comprises two ovaries, two uterine tubes, a uterus, and a vagina.
The uterine wall has three layers: endometrium, myometrium, and perimetrium.
Fertilization occurs within the uterine tubes.
The male reproductive system includes two testes, two epididymis, two seminal vesicles, two ejaculatory ducts, a prostate, and a penis.
The primary sex organs (gonads) produce gametes: testes in males and ovaries in females.

B. Gametogenesis

Gametes develop from germ cells that originate in the umbilical vesicle and migrate to the gonads.
Gametogenesis transforms germ cells (46 chromosomes, diploid) into male and female gametes (23 chromosomes, haploid).
The female gamete is a secondary oocyte (X).
The male gamete is a sperm (X or Y).
Gametes contain 22 autosomes and one sex chromosome.
Errors in meiosis can lead to abnormal gametes, such as in Down syndrome.

C. Female Reproductive Cycles

The ovarian cycle involves cyclical changes in the ovary monthly.
The menstrual cycle involves cyclical changes in the endometrium monthly.
The ovarian cycle phases are follicular, ovulation, and luteal.
The menstrual cycle phases are ischemic, menstrual, proliferative, and luteal.
Breastfeeding can temporarily cease menstruation.

D. Fertilization

Fertilization is the fusion of male and female gametes to form a zygote.
Fertilization typically occurs in the ampulla of the uterine tube.
Fertilization restores the diploid chromosome number (46 chromosomes).
Fertilization determines the embryo's sex (XX or XY).
Embryonic age begins two weeks after the last normal menstrual period (LNMP).

E. Cleavage (Segmentation)

Cleavage involves repeated mitotic divisions of the zygote, producing blastomeres.
Cleavage occurs in the uterine tube during the first week of pregnancy.
The morula is a solid ball of cells formed during cleavage.
The morula develops into a blastocyst with an inner cell mass (embryoblast) and outer layer (trophoblast).

F. Implantation

Implantation is the embedding of the blastocyst into the endometrium of the uterus.
The usual implantation site is the upper posterior wall of the uterus's fundus.
By day 10, the blastocyst is fully embedded, creating a closing plug within the endometrium.
By the end of the second week, the endometrium is filled with edematous cells rich in glycogen and lipids (decidua).

G. Gastrulation

Gastrulation is the beginning of morphogenesis (body form development), occurring during week 3.
The first sign of gastrulation is the primitive streak formation, a thickened linear band of epiblast cells.
The primitive node is at the cranial end of the primitive streak.
The primitive streak's growth leads to the development of the notochord.

H. The 3rd Week

The notochordal process forms a plate, which folds to form the notochord, the primordial axis of the embryo.
The notochord is crucial for central nervous system and axial musculoskeletal development.
The end of the 3rd week finds the embryonic disc changing shape to a flat, elongated form with a broad head and narrow tail.
Tertiary chorionic villi form during this period.

I. Folding of the Embryo

During the fourth week, the flat embryonic disc folds to form a cylindrical embryo.
Folding involves the formation of a head, tail, and lateral folds, resulting in the umbilical ring.
The chorionic villi at the embryonic pole grow and branch, forming the chorion frondosum part of the placenta.

J. Derivatives of the Germ Layers

The epiblast forms the three germ layers (ectoderm, mesoderm, endoderm).
The ectoderm differentiates into neuroectoderm and dermoectoderm.
The neuroectoderm gives rise to the neural tube and crest.
The mesoderm is segmented into paraxial, intermediate, and lateral plate mesoderms.
The paraxial mesoderm forms somites, crucial for skeletal, muscular and connective tissue development.
The number of somites can be used to determine the embryo's age.
The intermediate mesoderm contributes to the urogenital system.
The lateral plate mesoderm forms the intraembryonic coelom and subsequently the pericardial, pleural and peritoneal cavities.

K. Placenta

The placenta is the fetal-maternal organ responsible for gas and nutrient exchange.
The full-term placenta is discoid, weighing approximately 500g and expelled within 30 minutes of birth.
The fetal side of the placenta, derived from the chorion frondosum, is smooth and covered by the amnion.
The maternal side, derived from the decidua basalis, is irregular and divided into cotyledons.

L. Umbilical Cord

The umbilical cord is about 50 cm long at full term.
The cord contains two arteries and one vein, enveloped in Wharton's jelly.

M. Twins

Dizygotic twins arise from two separate zygotes.
Monozygotic twins arise from one zygote.
Conjoined twins result from incomplete separation.

THE Amnion

The amnion forms a fluid-filled sac that surrounds the embryo, maintaining homeostasis and supporting growth.
Amniotic fluid volume varies but typically 800-1000ml.
The umbilical vesicle, an older name for the yolk sac, is a pear-shaped structure connected to the midgut by a duct. It plays a role in germ cell development.

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Description

This quiz explores the anatomy and functions of the male and female reproductive systems, including gametogenesis and the processes involved in the formation of gametes. Additionally, it will cover the structure of the ovarian and menstrual cycles. Test your knowledge on the biological aspects of reproduction!