Female reproductive sysytem-2

Female Internal Genitalia

The internal organs of female reproductive system lie in the pelvic cavity and consists of:

• The vagina-1
• Uterus-1
• Fallopian tube -2
• Ovaries-2

Vagina

The vagina, which runs from the cervix to the vaginal aperture in the perineum, is an 8–10 cm long tubular fibro-muscular canal coated with mucus membrane. The adult's front wall measures around 7.5 cm in length, while the back wall measures 10 cm. The cervix's angle of insertion through the anterior wall is what causes the variation. The cervix projects into the vagina roughly at right angles, creating four fornices, which are recesses in the vaginal wall that widen at the upper portion of the wall. The lateral fornices are deeper than the anterior fornix, which is shallow, and the posterior fornix is deep.The inferior end of the vaginal opening is sealed off by a little hymen, or fold, of vascularized mucus membrane. It absorbs sperm from the penis during sexual activity, serves as an exit for menstrual blood flow, and, towards the conclusion of pregnancy, transforms into the birth canal. The vagina has a pH of 4.5 because of the lactic acid that is produced when lactobacilli (also known as Doderlein's bacilli) break down glycogen in the squamous cells that line the vagina. They create lactic acid, which aids in the destruction of any harmful germs that may enter the vagina.

Organ Associated with the Vagina

• Anteriorly: The fundus of urinary bladder and the urethra.
• Posteriorly: The upper third of the vagina is in contact with the peritoneum of the recto-vaginal pouch of douglas. The middle third is in a pposition with rectum, while the lower third is related to the perineal body.
• Laterally: the levator ani, visceral pelvic fascia.    
• Superiorly: the uterus and uterine arteries pass just above the lateral fornices.

Structure of the Vagina

The vaginal wall has three layers:

• An Adventitia: It is the superficial layer of the vagina which consists of areolar connective tissue. It contains blood vessels, lymphatics and nerves.
• The Muscularis: It is the middle muscular layer of the vagina, contains a few glands It is composed of an outer circular layer and inner layer of smooth muscle that can stretch to accommodate penis during sexual intercourse and child birth.
• The Mucosa: It is an inner layer and continuous with that of the uterus. It consists of stratified squamons epithelium and areolar connective tissue arranged in transverse folds (small folds) called rugae which are pink in appearance. This facilitates stretching of the vagina during child birth and intercourse.

Blood Supply of the Vagina

An arterial blood is supplied from the branches of internal illiac artery which includes vaginal artery and a descending branch of the uterine artery. The venous blood drains into the internal illiac veins. The lymphatic drainage of the lower third of the vagina drains into the inguinal glands and upper two thirds into the internal iliac glands.

Nerve Supply of the Vagina

The vagina is supplied by sympathetic and parasympathetic nerve from a branch of the pelvic plexus (situated in the floor of the pouch of Douglas in the region of the uterosacral ligaments) which originate from branches of the 2nd, 3rd and 4rh sacral nerves. The vaginal nerves follow the vaginal arteries to supply the vaginal wall and also the erectile tissue of the vulva.

Uterus

The uterus (womb) is a hollow muscular pear-shaped organ. It is situated in the cavity of true pelvis, behind the bladder and in front of the rectum. This is the main organ of the internal female reproductive system. It serves as part of the pathway for sperm deposit in the vagina to reach the uterine tubes and also the site of implantation of a fertilized ovum and development of fetus during pregnancy and labour. During reproductive cycles when implantation does not occur, the uterus is the source of menstrual flow.

The non-pregnant uterus is a hollow, muscular pear-shaped organ situated in the true pelvis. It is 7.5cm (3 inch) long, 5 cm (2 inch) wide and 2.5 cm (1 inch) thick at the site of cornu and weigh about 40-60 grams in adult nuliparous. During pregnancy, it increases 3-6 times.

Positions of the Uterus

The adult uterus is usually anteverted (tipped anterosuperiorly relative to the axis of the vagina) and anteflexed (flexed or bent anteriorly relative to the cervix, creating the angle of flexion) so that its mass lies over the bladder. Anteversion is the angle formed by long axis of the uterus with long axis of vagina, it is 90 degrees normally. Anteflexion is the angle formed by the axis of uterus with axis of cervix, it is normally 125 degrees.

Major Parts of the Uterus

• The fundus: This is the dome shaped upper portion of the uterus between the insertion of the uterine tubes. The point at which the fallopian tube enters is called the cornu or horn.
• The body or corpus: A tapering central portion is called body or corpus. This is the main part of the uterus.
• The isthmus: This is a narrow area between the cavity and the cervix, which is 1cm long. It enlarges during late pregnancy and labour to form the lower uterine segment.
• The cavity: The interior of the body of the uterus is called uterine cavity. This is the potential space between the anterior and posterior walls. It is triangular in shape, the base of the triangle being uppermost.
• The cervix or neck: The cervix is the lower part of the uterus. It is cylindrical in shape and 2.5 cm in length. It has two opening, called os. The cervical opening into the vagina is called the external os; the cavity running the length of the cervix is the endocervical canal and the opening of the endocervical canal into the uterine cavity is called the internal os. The cervix contains alkaline fluid. During childbirth the canal is greatly stretched.

Organ Associated with the Uterus

• Anteriorly: The uterovesical pouch and the bladder.
• Posteriorly: The rectouterine pouch of Douglas and the rectum.
• Laterally: The broad ligaments, the uterine tubes and the ovaries.
• Superiorly: The intestines.
• Inferiory: The vagina.

Structures of the Uterine Wall

The uterus consists of three layers of tissues; perimetrium, myometrium and endometrium.

Perimetrium

The visceral peritoneum's outermost layer, the perimetrium, also known as serosa, covers the uterus and fallopian tubes. Simple squamous epithelium and areolar connective tissue make up its structure. It changes into the wide ligaments laterally. It forms the vesicouterine pouch, a shallow pouch that covers the urinary bladder from the front. It forms a deep pouch between the uterus and bladder that is posterior, known as the rectouterine pouch or the Douglas pouch, and it covers the rectum.

Myometrium

The smooth muscle layer is located in the middle layer of the uterus, the myometrium. The three layers of smooth muscle fibers that make up the myometrium are thickest in the fundus and thinnest in the cervix. The inner and outer layers are longitudinal or oblique, while the middle layer is thicker and circular. The size and thickness of the muscle cells both increase during pregnancy.

Endomentrium

The endometrium, or inner layer of the uterus is highly vascular. It prevents adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. It is divided functionally into two layers:

• The functional layer (Stratum functionalis): It is the upper layer that shed during every menstruation, and if pregnancy occurs, it continues to be site of attachment and nourishment for morula (fertilized zygote)
• The Basal layer (Stratum basalis): It lies next to the myometrium and is not lost during menstruation. New stratum functionalis rise from this layer after each menstruation. During the menstrual cycle, the endometrium grows into a thick, blood vessel rich, glandular tissue layer. This represents an optimal environment for the implantation of fertilized ovum (blastocyst). During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta.

Supporting Structures of the Uterus

The uterus is supported in the pelvic cavity by surrounding organs, muscle of the pelvic floor and several ligaments that suspend it from the wall of the pelvis and maintains the position of the

uterus.

Primary Supports

• Muscular support
  • Pelvic diaphragm,
  • Perineal body,
  • Distal urethral sphincter mechanism.
• Fibro-muscular support,

• Uterine axis,
• Pubocervical ligaments,
• Transverse cervical ligaments of Meckenrodt,
• Uterosacral ligaments,
• Round ligaments of uterus.

Secondary Supports

These are of doubtful value and are formed by peritoneal ligaments.

• Broad ligaments,
• Vesico-uterine pouch and fold of peritoneum,
• Rectovaginal or rectouterine pouch and fold of peritoneum.