The term “infundibulum” originates from Latin, meaning “funnel,” a shape that aptly describes several distinct anatomical structures within the human body. These structures, despite their varied locations and functions, share this common descriptive name.
The Infundibulum of the Brain
The infundibulum in the brain is a slender, funnel-shaped stalk that serves as a physical and functional connection between two crucial endocrine glands: the hypothalamus and the pituitary gland. It is situated at the base of the brain, extending downward from the hypothalamus. This structure is also commonly referred to as the pituitary stalk or infundibular stalk.
This brain infundibulum contains a network of nerve fibers and blood vessels. These components facilitate communication and transport between the hypothalamus and the pituitary gland. Hormones synthesized in the hypothalamus, such as oxytocin and vasopressin, travel down the nerve fibers within the infundibulum to the posterior pituitary, where they are released into the bloodstream.
The infundibulum plays a crucial role in the endocrine system’s regulation of various bodily processes. It ensures that signals from the hypothalamus, which acts as the brain’s central command center, reach the pituitary gland. This connection allows for the coordinated release of hormones that influence growth, metabolism, reproduction, and stress responses. Damage to this delicate structure can disrupt hormonal balance, leading to conditions like central diabetes insipidus, characterized by excessive thirst and urination.
The Infundibulum of the Fallopian Tube
Another significant anatomical structure bearing the name infundibulum is found in the female reproductive system, specifically as part of the fallopian tube. This infundibulum represents the funnel-shaped, outermost (distal) end of the fallopian tube. It is positioned in close proximity to the ovary, although it is not directly attached.
The structure is characterized by numerous finger-like projections called fimbriae that extend from its edges. These fimbriae are highly mobile and contain cilia, which are tiny hair-like structures. During ovulation, when an egg is released from the ovary, the fimbriae swell with blood and gently sweep over the surface of the ovary.
The coordinated movement of the fimbriae and the beating action of their cilia create currents that effectively capture the ovulated egg. This mechanism directs the egg into the fallopian tube, where it can then travel towards the uterus for potential fertilization. The infundibulum and its fimbriae are thus essential for successful egg capture and the initiation of the reproductive process.
Infundibula in Other Body Parts
The term “infundibulum” is also applied to other, less commonly discussed, funnel-shaped or conical structures in the human body. One such location is within the heart, where the conus arteriosus is also known as the infundibulum. This muscular, conical pouch forms the outflow tract of the right ventricle, directing deoxygenated blood into the pulmonary artery. It plays a role in supporting the pulmonary valve.
Another example is the ethmoidal infundibulum, located within the ethmoid bone in the nasal cavity. This narrow, funnel-shaped channel is part of the complex drainage pathway for several paranasal sinuses, including the frontal, maxillary, and anterior ethmoid sinuses. It connects the frontal sinus drainage pathway and the anterior ethmoid air cells to the middle nasal meatus, facilitating the flow of mucus.