The gonads, namely the testes in males and the ovaries in females, are pivotal in producing gonadal hormones that orchestrate the intricate processes of sexual development and reproduction.
In males, testosterone is the primary gonadal androgen. It plays a central role in the maturation of male reproductive organs — the penis and testes. Additionally, testosterone is instrumental in the development of secondary sexual characteristics — a deep voice as well as facial and pubic hair growth — and...

Blood plasma is a fluid that contains approximately 92% water and 8% solutes. The solutes include various types of proteins, which constitute about 7% of the total solutes in the plasma. The high-molecular-weight proteins—albumins, globulins, and fibrinogen—are essential to plasma function. Albumins, making up about 60% of the plasma proteins, maintain the osmotic balance within blood vessels by preventing excessive water leakage. Additionally, albumins serve as carrier proteins, binding to...

Fetal circulation is a unique system that facilitates the exchange of gases, nutrients, and waste products between the developing fetus and the mother. This intricate process takes place through a special organ called the placenta.
Two umbilical arteries transport blood from the fetus to the placenta. At the placenta, the blood absorbs oxygen and nutrients while simultaneously eliminating waste products. This oxygen-enriched and nutrient-rich blood then returns to the fetus through one...

The blood in our bodies comprises three major components: blood plasma, formed elements, and the extracellular matrix. Blood plasma is a yellowish fluid that constitutes 55% of the total blood volume. It is primarily made up of water and essential substances such as electrolytes and proteins. Blood plasma serves as a medium for transporting blood cells and also contains nutrients, enzymes, hormones, antibodies, and gases.
Formed elements constitute the remaining 45% of the blood volume. These...

During early development, the embryo forms two types of connective tissues— the mesenchyme and mucoid connective tissue.
The mesenchyme is the first connective tissue that emerges in the developing embryo. It consists of loosely arranged multipotent mesenchymal cells and reticular fibers in the extracellular matrix. This loose arrangement allows easy migration of cells, which is essential for germ layer positioning, patterning, and organ morphogenesis during embryonic development. Mesenchyme is...

Transcytosis is the process in which molecules are internalized by endocytosis, transported across the cell, and released through exocytosis from the opposite end of the cell. Molecules such as insulin, immunoglobulins, and certain nutrients are transferred through the recycling endosomes by recycling and transcytosis.
IgG molecules from a mother undergo transcytosis starting around 13 weeks of gestation. The amount of IgG transferred and entering the fetal blood circulation increases with...