Human Reproduction: Fertilization Process

Questions and Answers

What is the location where fertilization typically occurs?

Vagina

Uterine tube (correct)

Ampulla

Uterus

What is the stage of meiosis at which the secondary oocyte is suspended?

Metaphase of Meiosis I

Telophase of Meiosis I

Anaphase of Meiosis II

Metaphase of Meiosis II (correct)

What is the function of hyaluronidase in fertilization?

To release acrosin

To break down the zona pellucida

To break down the bonds between adjacent follicle cells (correct)

To digest a pathway to the oocyte surface

What is the structure that surrounds the secondary oocyte and protects it?

Corona radiata Signup and view all the answers

What is the outcome if the secondary oocyte is not fertilized?

It will disintegrate Signup and view all the answers

What is the function of acrosin in fertilization?

To digest a pathway to the surface of the oocyte Signup and view all the answers

What is the process by which the spermatozoon reaches the oocyte?

Penetration of the corona radiata Signup and view all the answers

What triggers oocyte activation and the completion of meiosis?

Contact with a single spermatozoon Signup and view all the answers

Which of the following systems develops from the mucous epithelium of the nasal passageways?

Respiratory system Signup and view all the answers

What is the function of the yolk sac?

Important site of blood cell formation Signup and view all the answers

During placentation, what happens to the embryo by week 4?

It becomes suspended in a fluid-filled chamber Signup and view all the answers

Which of the following is NOT one of the four extra-embryonic membranes formed?

Trophoblast Signup and view all the answers

What is the function of the chorion?

Creates a rapid-transit system for nutrients Signup and view all the answers

Which of the following is formed by the combination of ectoderm and mesoderm?

Amnion Signup and view all the answers

What is the base of the allantois later derived from?

Urinary bladder Signup and view all the answers

What is the function of the chorionic villi?

Creates a network within the endometrium Signup and view all the answers

Which of the following systems develops from the gonads and the adjacent portions of the duct systems?

Reproductive system Signup and view all the answers

What is the purpose of the amniotic fluid?

Cushions and supports the developing embryo Signup and view all the answers

What is the probability that Lydia will inherit the disease allele from her mother?

0.5 Signup and view all the answers

What type of gene action occurs when one gene suppresses the effect of another gene?

Suppressor gene action Signup and view all the answers

Which of the following is a characteristic of X-linked inheritance?

Genes affect only somatic structures Signup and view all the answers

What is the difference between the X and Y chromosomes?

X is larger and has more genes than Y Signup and view all the answers

What is the genotype of a woman with normal color vision, with respect to an X-linked trait?

XCXC or XCXc Signup and view all the answers

What type of inheritance pattern is shown by the disease in the initial example?

Autosomal dominant Signup and view all the answers

What is the significance of the Y chromosome in sex determination?

It includes dominant alleles specifying that the individual will be male Signup and view all the answers

What is the difference between sperm and oocytes in terms of sex chromosomes?

Sperm have either X or Y chromosomes, while oocytes have two X chromosomes Signup and view all the answers

What is the minimum number of recessive alleles required for a female to be colour blind?

Two Signup and view all the answers

Why do X-linked recessive traits appear more frequently in males?

Because males have only one X chromosome Signup and view all the answers

What is the name of the gene responsible for sex determination in humans?

SRY gene Signup and view all the answers

During what week of fetal development do testes develop in a male embryo?

8th week Signup and view all the answers

What happens to the gonads in a female embryo if the SRY gene is not present?

They develop into ovaries Signup and view all the answers

Which of the following is NOT an X-linked recessive trait?

Cystic fibrosis Signup and view all the answers

Why do females have a lower frequency of X-linked recessive traits compared to males?

Because females have two X chromosomes Signup and view all the answers

What is the term for the initial stage of gonad development in which they have the potential to become either ovaries or testes?

Bipotential Signup and view all the answers

What is the primary function of the chorionic villi in embryonic development?

To facilitate exchange of oxygen and nutrients between the mother and the fetus Signup and view all the answers

At what stage of development does the fiberoptic view of the human embryo show the formation of the arm and leg buds?

Week 4 Signup and view all the answers

What is the primary function of the syncytial trophoblast in the placenta?

To produce hormones that regulate maternal physiology Signup and view all the answers

What is the role of progesterone in embryonic development?

It maintains the uterine lining during pregnancy Signup and view all the answers

What is the function of human chorionic gonadotropin (hCG) in embryonic development?

It maintains the corpus luteum, supporting progesterone production Signup and view all the answers

What is the primary function of the umbilical cord in embryonic development?

It facilitates the exchange of oxygen and nutrients between the mother and the fetus Signup and view all the answers

What is the role of the amnion in embryonic development?

It forms a protective barrier around the fetus Signup and view all the answers

What is the primary function of the placenta as an endocrine organ?

It produces hormones that regulate maternal physiology Signup and view all the answers

Study Notes

Fertilization

Occurs in the uterine tube within a day after ovulation
Secondary oocyte travels a few centimeters, while spermatozoa must cover the distance between the vagina and ampulla
The secondary oocyte is suspended in metaphase of Meiosis II and is surrounded by corona radiata, which protects it
If not fertilized, it will disintegrate

Acrosomal Enzymes

Release hyaluronidase and acrosin
Penetrate corona radiata and zona pellucida, towards the oocyte surface
Hyaluronidase breaks down bonds between adjacent follicle cells, allowing spermatozoon to reach the oocyte
Acrosin is a proteolytic enzyme required to reach the oocyte and digests a pathway to the oocyte surface

Fertilization and Oocyte Activation

Acrosomal enzymes from multiple sperm create gaps in the corona radiata
A single sperm then makes contact with the oocyte membrane, triggering oocyte activation and the completion of meiosis

Embryonic Development

The germ layers (ectoderm, endoderm, and mesoderm) are involved in the formation of the embryonic disc
The embryonic disc is a three-layered sheet produced by gastrulation and will form the body of the embryo
The rest of the blastocyst will be involved in forming extraembryonic membranes

Extraembryonic Membranes

Support embryonic and fetal development
Four extraembryonic membranes are formed: yolk sac (endo- and mesoderm), amnion (ecto- and mesoderm), allantois (endo- and mesoderm), and chorion (meso- and trophoblast)
Each membrane has a specific function, such as blood cell formation (yolk sac), cushioning the developing embryo or fetus (amnion), and creating a functional placenta (chorion)

Placentation

The chorion continues to enlarge and creates an intricate network within the endometrium, carrying maternal blood
The embryo, amnion, and yolk sac are suspended in a fluid-filled chamber by week 4
The fetus moves further away from the placenta and is connected by the umbilical cord

Endocrine Placenta

The placenta synthesizes and releases hormones into the maternal bloodstream, including human chorionic gonadotropin (hCG), human placental lactogen (hPL), placental prolactin, relaxin, and progesterone and estrogens

Polygenic Inheritance

Some phenotypic traits are determined by the interaction between several genes
Resulting phenotype depends on how alleles interact
Examples include suppression, where one gene suppresses the other, and complementary gene action, where dominant and recessive alleles on two different genes interact

Sex-Linked Inheritance

Sex chromosomes (X and Y) have different genes and functions
The X chromosome is larger and has more genes than the Y chromosome
X-linked genes affect somatic structures and are carried by the X chromosome
Inheritance of X-linked traits follows a specific pattern, with females being carriers and males being affected

Sex Determination

The SRY gene on the Y chromosome determines male sex determination
Gonads are initially undifferentiated (bipotential) and require male-specific transcription factors to develop into testes (8th week)
If the SRY gene is not present, gonads will develop into ovaries (12th week)

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Description

This quiz covers the process of fertilization, including the journey of the secondary oocyte and spermatozoa, and the site where fertilization occurs. Understand the stages of meiosis and the role of the corona radiata.