Female Internal Genitalia

The female internal genital organs are essential for reproduction and include several key structures that work together to enable the processes of menstruation, fertilization, and childbirth. 

1.0Female Internal Genitalia

The Uterus

Structure

The uterus is a single organ in the midline of the pelvic cavity between the bladder and the rectum.

Divisions of Uterus 

• The uterus is divided into three portions: 
• Fundus (above the entrance points of fallopian tubes)
• Body (between fundus and Isthmus)
• The Isthmus, a short, narrowed part of the body at its inferior end and 
• Cervix (below Isthmus), which extends into the vagina 
• The uterus is made up of three layers: 
• The serous or outer layer is called the perimetrium. 
• The myometrium or middle muscular layer
• Endometrium or inner mucus layer.
• The luminal surface of the endometrium is covered with a simple cuboidal/columnar epithelium. 
• The epithelium is continuous, with mucosal glands (uterine glands) extending deep into the endometrium. The lamina propria itself is densely cellular.
• The stromal cells of the lamina propria play important roles during pregnancy and menstruation.
• About two-thirds of the luminal side of the endometrium is lost during menstruation and is called the functional zone (also called the stratum functionalis) 
• The basal third of the endometrium that remains after menstruation is called the basal zone (also called the stratum basale).

Function:

• The established functions of the uterus are all related to fertilization and pregnancy. The main functions of the uterus are to
• Assist the movement of sperm from the vagina to the oviducts.
• Provide a suitable site for attachment and implantation of the blastocyst, including a thick, nutrient-rich stroma.
• Limit the invasiveness of the implanting embryo so that it stays in the endometrium and does not reach the myometrium. 
• Provide a maternal side of the mature placental architecture. This includes the basal plate, which the fetal side attaches, and large intervillous spaces filled with maternal blood after the first trimester. 
• Grow and expand with the growing fetus so that the fetus develops within an aqueous, non-adhesive environment.
• Provide muscular solid contractions to expel the fetus and placenta at term. 

Cervix

• The cervix is the lower constricted part of the uterus.
• It is divided into two portions: 
• The upper supravaginal portion communicates with the body of the uterus through the internal os (orifice) of the cervix. The mucus membrane of this portion has glandular follicles, which secrete mucus.
• Lower vaginal portion, which projects into the anterior wall of the vagina and it communicates with the vagina through external os (orifice) of the cervix. The mucus membrane of this portion is formed by stratified epithelial cells.

The Oviduct

Structure:

• Females have two fallopian tubes (or oviducts) that extend from the sides of the uterus, each measuring about 10 cm (4 inches) in length. 
• These tubes are situated within the folds of the uterus's broad ligaments. 
• The funnel-shaped section of each tube, known as the infundibulum, is positioned near the ovary and opens into the pelvic cavity. 
• The infundibulum ends in finger-like projections called fimbriae, one of which is attached to the ovary. 
• The fimbriae help guide the secondary oocytes from the peritoneal cavity into the fallopian tube.
• The ampulla is the widest and longest section of the fallopian tube, accounting for about two-thirds of its length. The isthmus is the more medial, shorter, narrower portion that connects directly to the uterus. 

The fallopian tubes consist of three histological layers

• Mucosa : Made up of an epithelium and lamina propria (areolar connective tissue). The epithelium contains ciliated columnar cells, which act like a "ciliary conveyor belt," helping to move a fertilized egg or secondary oocyte toward the uterus. There are also non-ciliated peg cells with microvilli that secrete a fluid providing nourishment for the ovum.
• Muscularis : Composed of an inner circular layer and an outer longitudinal layer of smooth muscle. The movement of the oocyte or fertilized egg is facilitated by peristaltic contractions and the ciliary activity of the mucosa.
• Serosa : The outermost layer, which is a serous membrane, providing protection to the tube.

Function:

The fallopian tubes serve as a pathway for sperm to reach the egg and transport secondary oocytes and fertilized eggs from the ovaries to the uterus.

The Ovary

Structure:

• The ovary is situated within a fold of the peritoneum known as the broad ligament, typically near the lateral wall of the pelvic cavity. Since the ovary extends into the peritoneal cavity, ovulated eggs temporarily reside there before being captured by the fallopian tubes. 
• The ovary consists of two main regions: the outer cortex and the inner medulla. The medulla is innervated by neurovascular elements, while the cortex contains a densely cellular stroma, covered by a connective tissue capsule called the tunica albuginea and a layer of simple epithelium made up of ovarian surface epithelial cells.
• Within the stroma lie ovarian follicles, each containing a primary oocyte surrounded by follicle cells. As the ovary has no ducts to transport gametes, ovulation involves an inflammatory process that breaks down the ovarian wall. Following ovulation, ovarian surface epithelial cells quickly divide to repair the wall.

Function:

• The ovaries produce gametes secondary oocytes that develop into mature ova (eggs) after fertilization and
• Hormones, including progesterone and estrogens (the female sex hormones), inhibin, and relaxin.

Vagina

• The vagina is a fibromuscular, membranous channel that connects the uterine cavity to the exterior at the vulva. 
• It serves as the excretory pathway for uterine secretions and menstrual blood. Additionally, it functions as the organ of copulation and serves as the birth canal during childbirth. 
• The canal is oriented upwards and backwards, forming a 45° angle with a horizontal position. Its diameter is approximately 2.5 cm, being widest at the upper part and narrowest at the introitus. 
• The vagina has significant distensibility, as demonstrated during childbirth. Unlike the skin, it lacks hair follicles, sweat glands, and sebaceous glands.
• Vaginal secretions are minimal, sufficient to keep the surface moist. They may increase slightly during the mid-menstrual phase, just before menstruation, during pregnancy, or with sexual arousal. 
• These secretions primarily originate from the glands of the cervix and uterus, transudation of the vaginal epithelium, and Bartholin's glands.
• The vaginal pH is acidic and fluctuates throughout different life stages and menstrual cycles. 
• The conversion of glycogen in exfoliated squamous cells to lactic acid by Doderlein's bacilli is influenced by estrogen. 
• As a result, the pH is more acidic during the childbearing years, typically ranging from 4 to 5.5, with an average of 4.5. The upper vagina may have a higher pH due to the presence of alkaline cervical secretions.
• Vaginal secretions consist of tissue fluid, epithelial debris, a few leukocytes (rarely more than an occasional pus cell), electrolytes, proteins, and lactic acid at a concentration of 0.75%.

2.0Vulva or External Genitalia

• The vulva, also known as the pudendum, encompasses the external female genitalia. It consists of several components:
• At the front, above the vaginal and urethral openings, is the mons pubis, a fatty tissue elevation covered by skin and coarse pubic hair that cushions the pubic symphysis. Extending downwards and backwards from the mons pubis are the labia majora, or "major lips." 
• These longitudinal folds of skin are covered in pubic hair and contain abundant adipose tissue, sebaceous glands, and apocrine sweat glands. They are homologous to the scrotum in males.