Human Development and Birth Defects

The time period during fetal development when organs are most susceptible to developmental defects, typically from week 3 to 8.

Chemical, physical, or biological agents that can cause harm to a developing fetus, potentially leading to birth defects.

The prenatal period spanning weeks 9 to 38, characterized by organ maturation and growth.

The process of producing gametes (sex cells) - sperm in males and eggs in females.

The process of a sperm cell fertilizing an egg cell, marking the beginning of pregnancy.

The early stages of embryonic development characterized by rapid cell division.

The process of forming the three primary germ layers (ectoderm, mesoderm, and endoderm) which give rise to all other tissues and organs in the body.

The process of forming the basic structure and shape of the body, including the development of organ rudiments.

The process of organ development, including the formation of specialized tissues and structures.

A genetic disorder caused by a mutation in the LMNA gene, leading to accelerated aging and premature death.

The process of a primordial follicle developing into a primary follicle.

A layer of glycoproteins and glycosaminoglycans that surrounds the oocyte in the primary follicle.

A second messenger molecule that plays a role in regulating oocyte maturation.

Special junctions that allow communication between the oocyte and follicular cells.

The stage of meiosis where the oocyte is arrested before fertilization.

The cells surrounding the oocyte in a growing follicle that start to express receptors for FSH.

The layer of cells that surrounds the oocyte in the growing follicle, formed by the developing granulosa cells.

The hormone that stimulates follicle growth and development.

Sertoli cells within the testes convert a portion of testosterone into estrogens. These estrogens then travel back to the Leydig cells, working in a paracrine fashion, alongside a stimulating factor.

Inhibin, produced by Sertoli cells, negatively regulates the secretion of FSH from the pituitary gland. Inhibin travels through the bloodstream to reach the pituitary, acting as a feedback mechanism.

Sperm count below 10 million per ml of semen, impaired sperm movement, abnormal sperm morphology, alterations in sperm genetic material, medication side effects, hormonal imbalances, environmental factors, smoking, and blockages within the reproductive tract are all potential causes of male infertility.

The process of egg development within the female reproductive system, involving the maturation of both the oocyte (egg) and its surrounding follicle.

Immature follicles containing oogonia (egg precursor cells) surrounded by a single layer of squamous granulosa cells, which are somatic cells that contribute to oocyte development.

These follicles consist of the oocyte surrounded by a simple cuboidal layer of granulosa cells, indicating an initial stage of development.

These follicles, also known as Graafian follicles, contain a mature oocyte and a layered, stratified arrangement of granulosa cells, signifying the advanced maturity of the developing egg.

These cell junctions, found between follicular cells and the oocyte, facilitate communication and exchange of essential molecules for oocyte maturation.

The initial phase of follicle development where follicles grow independently of gonadotropins.

The phase where follicles become responsive to gonadotropins, particularly FSH, and start growing rapidly.

The phase where follicles rely on gonadotropins for survival and growth. If they don't receive enough gonadotropin, they die.

The mature follicle that becomes independent of FSH and starts releasing inhibin, inhibiting further FSH production.

The resumption of meiosis I in the oocyte, triggered by an LH surge, leading to the formation of the secondary oocyte.

The process where the follicular cells surrounding the oocyte produce estrogen and estradiol, preparing the female reproductive tract for fertilization and implantation.

The region on the surface of the ovary where the Graafian follicle will rupture during ovulation.

The release of the mature ovum from the Graafian follicle, triggered by an LH surge and characterized by follicular wall rupture.

The vaginal environment is acidic (low pH), which is harmful to sperm. Seminal fluid temporarily buffers this acidity, allowing sperm to reach the cervix, where the pH is more suitable for swimming.

During ovulation, the cervical mucus becomes more fluid, allowing some sperm to pass through. This allows for fertilization to occur.

Sperm can quickly reach the uterine tube, but they are less likely to fertilize the egg at this time due to the egg's location and sperm's immaturity. Movement in this phase is primarily due to the contractions of the female reproductive tract.

Sperm travel slower through the cervical mucus, allowing for maturation. Some sperm may be stored in the cervical crypts for a couple of days, increasing their chances of fertilization.

Sperm bind to the isthmus of the uterine tube for 24 hours to undergo capacitation, a process that removes glycoproteins and cholesterol. This allows sperm to become hyperactive and bind to the zona pellucida of the egg.

Capacitation involves changes in the sperm's plasma membrane making it more fluid and permeable. This also leads to increased motility, protein phosphorylation, protein kinase activity, bicarbonate concentration, and intracellular pH, Ca++ and cAMP levels.

Sperm become hyperactive in bursts to break free from the isthmus and reach the ampulla, where they can meet the egg.

The ampulla is the meeting place for the oocyte and sperm. The egg is slowly moving towards the uterus.

The ovum is the female gamete, a secondary oocyte surrounded by a protective layer called the zona pellucida. The corona radiata, part of the cumulus oophorus, further envelops the oocyte. This entire structure, including the surrounding fluid containing hyaluronic acid, is known as the ovulated complex.

Leucin-rich-containing G-protein-coupled receptor 5 (Lgr5) is a marker found on stem cells in various organs, including the ovaries. These stem cells are responsible for regenerating the ovarian epithelium after ovulation.

Mittleschmerz refers to pain experienced by some women around the time of ovulation. This pain can be caused by the expansion of follicles before ovulation or by slight bleeding in the abdominal cavity after the follicle ruptures.

The corpus luteum is a yellowish structure that forms in the ovary after ovulation. It arises from the collapsed theca and granulosa cells of the follicle. It plays a crucial role in hormone production, primarily progesterone and estrogen, to prepare the uterine lining for a potential pregnancy.

The corpus luteum's life span is about 2 weeks. If fertilization occurs, the corpus luteum becomes the 'gravidic corpus luteum' and remains functional for several months. If fertilization does not occur, it degenerates into the 'menstrual corpus luteum' and eventually becomes the corpus albicans, a scar tissue.

After ovulation, the ovulated complex is captured by the fimbriae, finger-like projections at the end of the fallopian tube. This 'egg capture' is crucial for the egg to reach the uterus for potential fertilization.

Human chorionic gonadotropin (HCG) is a hormone produced by the developing embryo, specifically the syncytiotrophoblast. Its primary function is to maintain the corpus luteum's functionality, ensuring continued hormone production during early pregnancy.

The corpus luteum transforms from the corpus haemorrhagicum after ovulation. This transformation involves luteinization, leading to a whiter appearance, increased size, and enhanced hormone production due to a rich vascular network.