The term “fundus” is an anatomical descriptor used across several different organs. Derived from the Latin word for “bottom,” it consistently refers to the part of a hollow organ farthest away from its opening or exit point. This location can be at the top, back, or bottom of an organ depending on its orientation. The fundus often performs a specialized function or serves as a reference point for medical professionals, requiring context to understand its exact location and physiological role.
The Fundus of the Eye
The fundus of the eye, or fundus oculi, is the interior posterior surface of the eyeball, visible through the pupil when examined by a doctor. This region is a unique window into the body, as it is the only place where the microcirculation can be directly observed in a living person. The structures contained within the fundus are instrumental for vision, including the light-sensitive retina, the optic disc, the macula, and the central fovea.
The retina, a layer of photoreceptor cells, converts light into electrochemical impulses that travel through the optic nerve to the brain. The optic disc is the point where the optic nerve fibers converge and exit the eye, and it is notable for lacking photoreceptors, resulting in the physiological blind spot. The macula, located near the center of the fundus, is responsible for sharp, detailed central vision and color perception.
A medical examination of this area is called ophthalmoscopy or a fundoscopic exam, where a doctor uses a specialized instrument to shine a light through the pupil. This allows for the direct visualization of the retinal blood vessels, which can reveal signs of systemic diseases that affect blood flow throughout the body. For example, changes in the vessels, such as hemorrhages or vessel narrowing, can indicate conditions like uncontrolled hypertension, diabetic retinopathy, or glaucoma. Examining the fundus is a routine procedure that offers a non-invasive way to assess not just eye health, but also a patient’s overall cardiovascular and neurological status.
The Fundus of the Uterus
The uterine fundus is the dome-shaped, uppermost portion of the uterus, positioned above the entry points of the fallopian tubes. This highly muscular part plays a significant role in both pregnancy and childbirth. During gestation, the fundus expands dramatically to accommodate the growing fetus, increasing the organ’s capacity significantly.
In clinical practice, the measurement of “fundal height” is a routine procedure used during prenatal appointments, typically starting around 20 weeks of pregnancy. This measurement tracks the distance in centimeters from the top of the pubic bone to the top of the uterine fundus. After 20 weeks, the fundal height in centimeters generally corresponds closely to the number of weeks of gestation, providing a simple way to track fetal growth and verify the gestational age.
During labor, the uterine fundus is the primary source of the powerful contractions that facilitate childbirth. The muscle fibers contract strongly, pulling upward on the cervix and generating the force needed to push the baby downward. After delivery, the uterus contracts back down, and the fundus location is monitored. This monitoring ensures the muscle is firm and returning to its non-pregnant size, which helps prevent postpartum hemorrhage.
The Fundus of the Stomach
The fundus of the stomach is the rounded, superior section that extends upward, sitting slightly left of the cardiac opening where the esophagus connects. Positioned above the main body of the stomach, this region typically retains a cushion of gas resulting from digestion. The presence of this gas bubble is a normal finding often observed in medical imaging.
The gastric fundus serves an accommodative function, relaxing to allow the stomach to increase its capacity after a large meal. While the main body of the stomach handles active mixing of food and digestive secretions, the fundus acts as a temporary storage area. Food may rest here, allowing the initial digestion of starches by salivary amylase to continue before mixing with the stomach’s acid and enzymes.
Less Common Anatomical Fundi
The term fundus is also applied to other hollow organs, including the gallbladder and the urinary bladder, to denote their farthest ends. The fundus of the gallbladder is the rounded, closed, distal end of the pear-shaped organ, projecting slightly beyond the inferior edge of the liver. It forms the terminal boundary of the organ that concentrates and stores bile.
The fundus of the urinary bladder refers to the base or posterior-inferior surface of the organ. This area is opposite the neck of the bladder, which connects to the urethra. Defined as the furthest point from the exit, this region contributes to the overall structure and capacity of the organ that stores urine.