The internal female reproductive organs consist of the ovaries, fallopian tubes, uterus, and vagina.
The fallopian tubes are also often called the uterine tubes or oviducts.
These fibromuscular tubes transport a mature female reproductive cell or egg cell called an ovum from the ovary to the uterus.
Each fallopian tube is about 10-12 cm in length and is divided into four regions: closest to the ovaries is the infundibulum, which has finger-like projections called fimbriae; next is the ampulla; then the isthmus; and finally the intramural part, which travels through the wall of the uterus in order to transport the ovum into either the upper left or right of the uterine cavity.
The ampulla is the longest region and fertilization of an ovum is most likely to occur in this region.
The uterus is a hollow pear-shaped muscular organ that nourishes and supports the growth of an embryo during pregnancy.
The curved top or superior part of the uterus is called the fundus; the largest section in the middle is the body; and the bottom, more cylindrical portion is the cervix.
Although the cervix is part of the uterus, it’s histologically different from the rest of the uterus and will be covered in a separate video.
This video will just focus on the fundus and body of the uterus, which consist of three major layers: the inner endometrium, myometrium, and outer perimetrium, although the perimetrium is too thin to easily see in this image.
The endometrium is the inner mucosal layer that’s lined with simple columnar cells.
The myometrium is a thick and highly vascular wall of smooth muscle.
And the perimetrium consists mostly of a serosal layer or visceral peritoneum that’s continuous with the broad ligament, although, there are portions of the uterus that are surrounded by an adventitial layer of connective tissue instead.
Alright, let’s first take a closer look at the fallopian tubes.
The wall of each fallopian tube also consists of three main layers: an inner mucosa; a thick layer of smooth muscle called the muscularis; and a thin outer serosa.
At low magnification, the outer serosa is difficult to see, but if we zoom in closer, we can see that this layer is composed of only a single layer of basophilic or purple simple cuboidal cells and a very thin layer of supporting connective tissue.
The mucosa of the fallopian tubes have many long, thin, and branching folds, which mostly run longitudinally in the same direction as the tube itself.
The mucosal folds are more prominent in the ampulla and gradually become smaller in the regions closer to the uterus, with the intramural part of the tube no longer having any mucosal folds at all.
At high magnification, we can see that the mucosa is lined with a simple columnar epithelium.
This epithelium actually consists of two distinct types of cells: ciliated cells and secretory peg cells.
The ciliated cells can be identified by their visible cilia, that wave or sweep fluid toward the uterus in order to help an ovum or fertilized zygote to continue moving in the correct direction within the fallopian tube.
Also, the cytoplasm of the ciliated cells often don’t stain as dark when compared to peg cells, making it slightly easier to distinguish the two types of cells.
Each peg cell has an apical bulge that literally looks like a peg that’s protruding into the lumen.
These cells secrete a mucus that forms a film that covers the epithelium and provides nutrients for the ovum or fertilized zygote.
Unlike many other tubular tissues, there are no goblet cells or glands in the mucosa of fallopian tubes.
In this image of the muscularis, it’s easier to identify the two layers of smooth muscle that make up this layer.
Since this image is a cross-section of the fallopian tube, muscle fibers that are parallel to the plane of the cross-section will have a longer appearance.
As a result, the inner interwoven circular or spiral layer of smooth muscle will have muscle fibers that look longer; and the outer longitudinal layer will have muscle fibers that look more round. The inner circular muscles have peristaltic or wave-like contractions that help physically move an ovum or fertilized zygote towards the uterus.
Now, let's move to the uterus.