Transcription
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Hello everyone, this is Dr. Aragala, your faculty. We'll start our first topic, that is external genitalia. External genitalia is otherwise known as the vulva or pudenda. Now, this extends superficially from the pubic symphysis to the perineum to the perianal body.
Now, what are the structures in the external genitalia? The structures include mons pubis or mons veneris, labia majora, labia minora, clitoris, vestibule, hymen, then glands, namely Bartholin's gland and Skene's gland.
So, once again, we'll come to the structures. The structures include mons pubis or mons veneris, labia majora and minora, clitoris, vestibule, hymen, hymen, then glands like Bartholin's glands and Skene's glands.
So, this is the picture to show the vulval structures. So we have the mons veneris, the labia majora, labia minora, this is the vestibule, we have the clitoris over here, and this is the perineum. Okay. So this is the perineal region and anus.
Now, we'll see each one of it in order. Number one is mons pubis. Mons pubis is a fat-filled cushion area located over the pubic bone. This is in an inward triangular shape. So the base is in alignment with the pubic bone, and this tip comes up to the clitoris. You have numerous hair follicles over here. And this hair growth starts during puberty due to the action of the hormones and androgens. And the stage of hair growth over the small area happens in Tanner's stage three.
Once we come down, we'll be able to see the labia majora. So this is the, this pink shading structure is the labia majora that is seen over here. Now, this labia majora corresponds, labia majora corresponds to the scrotum in males. This measures in length about 7 to 8 cm and width will be some 1 to 1.5 cm, and it's composed of only adipose tissue. It consists of hair follicles on the outside. Whereas inside, there is nothing like that. Okay. Just the hair follicles are seen on the outside alone, and on the outside, you have numerous hair follicles, sweat glands, and sebaceous glands.
Now, what is the lining? The lining is by keratinized squamous epithelium. Okay. Then another important point is, in its anterior end, the round ligament comes and ends. So it has an attachment of the round ligament at its anterior end. Okay.
So, next one is labia minora. So if you see in the picture, this is the labium major, and this is the labium minora here, over here. Okay. So labia minora is also a tissue seen inside or medial to the labia majora. The length is between 2 to 10 cm, and width will be between 1 to 5 cm. Labia minora does not have hair follicles or sweat glands, but it does have some sebaceous glands and the lining. If you see, if this is the labia minora, the outside is lined by keratinized stratified squamous epithelium, and if you take the inner side, half of it is lined by keratinized squamous epithelium, and half of it is lined by non-stratified squamous epithelium. This region. So the differentiating line between these two lining epithelia, this is known as Hart's line.
Now, what is the clinical importance of this labia majora and minora? They may get lacerated during childbirth. And remember, labia majora and minora greatly vary in appearance and their length.
Next part is clitoris. Clitoris is homologous to the penis in males. So this is how the clitoral tissue is located over here. It consists of glans, body, then two crura. It is a female erogenous organ. It is, if you take the clitoris, we have seen the labia minora, right? So this labia minora comes and splits into two layers to cover this clitoris. This upper region is known as the prepuce, and this lower tissue is known as the frenulum.
Now, if we take a cross-section of the clitoris, you'll be able to see two corpora cavernosa in the body, and that is being surrounded by tunica albuginea and a clitoral fascia. This region over here is known as the clitoral hood. The blood supply of the clitoris to the corpora is by the deep artery. Then this region, that is the prepuce region and the glans, is supplied by the deep dorsal artery and drained by the deep dorsal and superficial dorsal vein, and the nerve supply is by the dorsal nerve.
Next structure is vestibule. Vestibule is derived from the female urogenital membrane. This is basically nothing but the space what you see here. Okay. So this region is the vestibule. It consists of openings. Six openings are there. Number one is the female external urethral opening. Two is the vagina. Three and four are the openings of the Bartholin's gland on either side. Five and six are the openings of Skene's gland. Okay. Then you'll have the vestibular bulb that is homologous to the bulb of the penis in males. It is located beneath this mucous membrane and below the bulbospongiosus muscle. So basically, this region is the vestibule.
Now, if you see the boundary of the vestibule, it is lined on the laterally, it is bound by the Hart's line. Medially, it is bound by the hymen. Anteriorly, we'll have the frenulum, and posteriorly, you will have the fourchette. See, what is fourchette? Fourchette is nothing but a thin layer of mucous membrane that is connecting the labia minora over here. Okay. So you also have something here called the fossa navicularis. Fossa navicularis is nothing but this space. Fossa navicularis is a depressional space that is seen between the vaginal opening and the posterior fourchette.
Next part, next structure is hymen. So what is hymen? It is a thickened mucous membrane seen covering the vaginal orifice. It is composed of elastic and collagen. Elastic tissue and collagen, they vary in thickness, and there are various types of hymen. These are the various types of hymen you have. So number one, there can be imperforate hymen also, without any opening. Then there can be cribriform hymen, where there are multiple numerous openings. Septate hymen, where a thin membrane is seen between two openings. A crescentic hymen and annular. A crescentic hymen, like just like a half-moon shape. Then annular opening, it's just a round shape, and fimbriated, like you have so many irregular openings, and a microperforate opening, where the opening is very small.
So, what is the clinical significance of hymen? Hymen, especially in the imperforate hymen, blood can accumulate during puberty age. If menstruation occurs, and it can lead to cryptomenorrhea, that is accumulation of the menstrual blood without coming to the exterior, that will present in the girl with pain and cyclical abdominal pain, especially swelling and cyclical abdominal pain. During pregnancy, this becomes thick and rich in glycogen. Next one. After birth. After childbirth. This hymen or left is numerous thickened nodules known as carunculae myrtiformes.
Coming to the glands, we'll see Bartholin's gland. This is located in the superficial perineal pouch. It is also known as greater vestibular glands. So this is the picture to show their location. Okay. So this is the Bartholin's gland that is located in the superficial perineal pouch. If you see, they are located at some 5:00 and 7:00 position, and the duct length is around 1.5 to 2 cm, and the gland length size is around 1.5 to 1 cm. So these are compound glands that secrete mucus during arousal. Sometimes, when there is infection or any trauma, this opening of the duct can get blocked, and there can be formation of Bartholin's cyst, which is a mere collection of fluid within the gland. Suppose if this cyst gets infected again, then it will lead to the formation of Bartholin's abscess.
Next is Skene's gland. This is also known as paraurethral gland. This is homologous to the prostate in males. So this is the picture. So these are the location of Skene's glands. Since it is located just around the urethra, it is also known as paraurethral glands. So any inflammation or duct obstruction may lead to urethral diverticulum formation since the ducts are opening into the urethra.
Now, we'll see the arterial supply of the pudendum. So the arterial supply is mainly by the internal pudendal artery, which is a branch of the internal iliac artery. Also, superficial external pudendal artery, which is a branch of the femoral artery, also supplies the mons pubis.
Coming to the venous drainage, we have the internal pudendal vein and the external pudendal vein. Internal pudendal vein drains into the internal iliac vein. External pudendal vein drains into the great saphenous vein, which drains into the femoral vein. And we all know this femoral vein, as it crosses the inguinal ligament, it becomes the external iliac vein. Now, both of these together will drain into the common iliac vein, which will further drain into the inferior vena cava.
Coming to the lymphatic drainage. Lymphatic drainage is mostly by the superficial inguinal lymph nodes. Already we have seen, clitoris alone is supplied by the deep inguinal lymph nodes.
Nerve supply is by the pudendal nerve. Root value of pudendal nerve is S2, S3, S4. So this gives the motor, sensory, and sympathetic innervation. Now, how the pudendal nerve enters into the pelvis? It enters the pelvis into the lesser sciatic foramen, and as it reaches the ischial spine, it winds around there and supplies all the regions. So any, any procedure in the perineum or the vulva will be blocking this pudendal nerve by blocking this, blocking this, any procedure in the pudendum or vulva. Any proced, sorry, any procedure in the pudendum or vulva will be blocking this pudendal nerve by locating this nerve around the ischial spine. Also, the mons pubis is supplied by the genital branch of the genitofemoral nerve. Mons pubis is supplied by the genital branch of genitofemoral nerve, and labia majora is supplied by the anterior labial nerve, which is a branch of the ilioinguinal nerve.
We have done with external genitalia. See you all in the next video. Until then, see you.