Anatomy Flashcards
What are Langer Lines?
Orientation of dermal fibres arranged transversely in the anterior abdo wall.
Layers of the anterior abdominal wall
Skin, 2x SC layer (fatty layer of the SC tissue - Campers & membranous layer of the SC tissue - Scarpas), rectus fascia, rectus sheath, peritoneum
What is the rectus sheath made of?
The medial fibrous aponeurosis of the external oblique, internal oblique and transversus abdominis muscles
In the midline, the aponeurotic layers of the flank muscles fuse to create…
linea alba
Arcuate line
1/3 the distane between the umbi and pubis. Gradual transition zone where fibers of the posterior rectus sheath disappear to form only the anterior sheath
Urachus
Forms the single median umbilical ligament. It is an obliterated tube that extends from the apex of the bladder to the umbilicus.
Paired medial umbilical ligaments
Formed by obliterated umbilical arteries that connected the internal iliac arteries to the umbilical cord in fetal life
Paired lateral umbilical ligaments
Contains the patent inferior epigastric vessels.
Ddx of anterior abdominal wall cyst
Urachal cyst, urachal sinus, urachal diverticulum
Transversalis fascia
Thin fibrous tissue layer that lies between the inner surface of the transversus abdominis muscle and the extraperitoneal fatty layer (preperitoneal fat). Serves as part of general fascial layer that lines with the abdominal cavity.
Inguinal ligament (@Poupart ligament)
Dense connective tissue that constitutes the inferior edge of the external oblique aponeurosis
Inguinal canal consists of
round ligament (ends as labium majus), genital branch of genitofemoral nerve and ilioinguinal nerve
What is the umbilicus?
A defect in the linea alba through which the fetal umbilical vessels previously passes. Contains the umbilical ring, skin, transversalis fascia and peritoneum. Innervated by T10. Lies between 3rd and 4th lumbar vertebrae. Level at which iliac veins join to form the vena cava and at which the abdominal aorta bifurcates.
Superficial epigastric artery
Arises from the femoral artery just below the inguinal lig, in the femoral triangle. It courses diagonally towards the umbilicus and risks injury during low transverse incision bet skin and rectus fascia, few centimetres from the midline
External pudendal vessels
Branch of the femoral artery. Supplying the mons pubis area. Clinically can cause extensive bleeding often with incisions made in the mons pubis area such as for retropubic midurethral sling incisions.
Arterial supply to the muscles and fascia of the anterior abdominal wall
Branches of external iliac vessels: The inferior epigastric vessels (found in lateral umbi ligaments) and deep circumflex vessels (branches of external iliac vessels)
The inguinal ‘Hesselbach’ triangle
The region on the ant abdo wall bounded inferiorly by the inguinal ligament, medially by the lateral border of the rectus muscles and laterally by the inferior epigastric vessels
Innervation of the anterior abdominal wall
Via the abdominal extensions of the intercostal nerves (T7-T11), the subcostal nerve (T12) : these nerves traverse between the internal oblique muscle and transversus abdominis muscles. ‘Transversus abdominis plane - essential for TAP blocks’.
The iliohypogastric and ilioinguinal nerves (L1) supply the mons pubis
Anatomical layout of the external genitalia / perineum
Bound anteriorly by mons pubis, behind by the buttocks and laterally by the thighs.
Bony boundaries: pubic symphysis anteriorly, ischiopubic rami and ischial tuberosities anterolaterally, sacrotuberous ligaments posterolaterally and coccyx posteriorly.
Skene’s ducts (Para urethral glands)
Lie posterolateral aspect of the urinary orifice. It runs below and parallel to the urethra for a distance of 1 - 1.5cm. It releases secretions that help lubricate the urethra and vaginal opening.
Duct obstructions can cause urethral diverticulum formation
Bartholin’s ducts / glands (@ Greater vestibular gland)
Paired glands that are found at the 4 o’clock and 8 o’clock location in relation to the vaginal opening on the labia minora.
The gland is covered by the Bulbospongiosus m - these muscles constrict the vaginal lumen and aid release of the bartholins secretions.
Hymen
A thin, vascularised membrane or its remnant (the hymenal ring) which separates the vagina from the vestibule. After coitus/ childbirth, the shrunken remnants of the hymen are known as hymenal caruncles
Fascial layer of the perineal floor
Superficial fatty layer - continuous from the anterior abdo wall; Campers fascia.
Deeper membranous layer - continuous from the anterior abdo wall (Scarpa’s fascia) but known as Colles fascia which is limited to the anterior half of the perineum.
Arterial supply of the skin and SC layers of the anterior abdo wall and mons pubis
The superficial epigastric, superficial circumflex iliac and superficial external pudendal arteries (from the femoral artery, within the femoral triangle)
Vulval arterial and nerve supply
Via pudendal vessels and nerve.
Clitoris
principle female erogenous organ. Located between the frenulum posteriorly and prepuce anteriorly. Rarely exceed 2cm length and is composed of a glans, a corpus and 2 crura. Innervated by paired dorsal nerves of the clitoris . Clitoral blood supply - branches of internal pudendal artery. The deep artery of the clitoris supplies the clitoral body and the dorsal artery of the clitoris supplies the glans and prepuce.
Arterial supply of the vagina
Proximal portion: cervical branch of the uterine artery and vaginal artery
Posterior vaginal wall: midlle rectal artery
Distal vaginal wall: internal pudendal artery
Lymphatic drainage of the vagina
Lower 1/3 of the vagina, along with those of the vulva drain into the inguinal lymph nodes. The remainder drains into the pelvic lymph nodes.
Urogenital triangle
Superficial space (under the Colles fascia)
- Ischiocavernosus m, Bulbosponginosus m, Perineal membrane, Superficial transverse perineal m and external anal sphincter.
Deep space
- Levator ani m (Pubococcygeus m, puborectalis m, iliococcygenus m)
*Levator ani trauma can lead to POP
Anal triangle
Contains the anal canal, anal sphincter complex (external and internal anal sphincter and puborectalis muscle) and ischioanal fossae. Also contains the banches of the pudendal nerve and internal pudendal vessels)
Perineal body
Fibromuscular pyramidal mass lies in the midline at the junction between the urogenital and anal triangles.
Clinically, measures 3.5 - 5cm in nulliparas from the posterior midline hymen to the mid-anal opening (standard POP-Q landmark)
Superficially, the bulbosponginosus, sup transverse perineal and EAS converges on the perineal body. More deeply, the perineal membrane, pubococcygeneus and IAS contribute
Lateral laparoscopic port sites insertion, how to avoid injuring the inferior epigastric vessel (in the lateral umbi ligament)
The inferior epigastric vessel (branch of the external iliac) sits lateral to the medial umbilical ligament (obliterated umbilical vessels) and medial to round ligament
Hasselbach triangle
Clinical risk of direct inguinal hernias in the ant abdo wall.
Artery to the round ligament (Sampson artery) is a branch of
Branch of the uterine artery and runs in the round ligament.
Branches of the anterior branch of the internal iliac artery
Blood supply to the pelvis is predominantly provided by branches of the internal iliac artery. The anterior division provides blood supply to the pelvic organs and perineum and includes the inferior gluteal, internal pudendal, middle rectal, vaginal, uterine, and obturator arteries, as well as the umbilical artery and its continuation as the superior vesical artery.
Posterior branch of the internal iliac artery
The posterior division branches extend to the buttock and thigh and include the superior gluteal, lateral sacral, and iliolumbar arteries. For this reason, during internal iliac artery ligation, many advocate ligation distal to the posterior division to avoid compromise to the areas supplied by this division
Arcus tendineus levator ani
Condensation of parietal fascia covering the medial surface of the obturator internus muscle. This structure serves as the point of origin for parts of the levator ani muscle.
Pelvic floor overview
Pelvic organ prolapse
is when 1 or more of the organs in the pelvis slip down from their normal position and bulge into the vagina.
Anterior division of the internal iliac artery
Internal pudendal
Obturator
Inferior gluteal
Branches that supply the pelvic viscera: uterine, vaginal, middle rectal and superior vesical arteries
2 direct branches of the aorta that supply the pelvic organs
Superior rectal artery: terminal branch of the inferior mesenteric artery anastomoses with the middle rectal arteries; contributing blood to the rectum and vagina.
Ovarian artery: anastomoses with the ascending branch of the uterine artery and contribute blood to the uterus and adnexa. Traversus via IP ligament. leaving a torniquet here will help slow blood supply down to the uterus
Pelvic innervation
Nerve supply to the visceral structures in the pelvis arises from the autonomic nervous system. 2 most important components of this system include the superior and inferior hypogastric plexuses.
The superior hypogastric plexus terminates by dividing into 2 trunks known as hypogastric nerves. These nerves join parasympathetic efferents from the 2nd - 4th nerve roots (pelvic splanchic nerves) to form the inferior hypogastric plexus. The sacral sympathetic trunk also contributes to the inferior hypogastric plexus
Anatomy in-relation to hysterectomy
Cardinal ligaments (transverse cervical ligaments/ Mackenrodt ligaments)
Primarily consists of vessels and connective tissue and contain some pelvic autonomic nerves in the lower portion. They attach to the posterolateral pelvic walls near the origin of the internal iliac and contain vessels supplying the uterus and vagina.
Paravesical space boundaries and clinical relevance
Anterior: symphysis pubis
Posterior/ cephalad: cardinal ligament
Lateral: external iliac artery
Medial: bladder, obliteral umbi ligament (medial)
Clinical relevance: to expose the parametrium prior to radical hysterectomy
Boundaries of the Retropubic space @ Retzius space
Anterior & laterally: bony pelvis and muscle of the pelvis wall
Posterior: bladder and proximal urethra
Clinical significance: potential surgical space filled with loose connective tissue that contains important neurovascular structures
What is the trajectory of the ureter
28-35cm long tubular structure. Proximal half in abdomen
Enters pelvis at the SI joint (level of pelvic brim) and crosses over the bifurcation of common iliac artery. Once on the medial aspect, it lies inferior to the IP.
It follows the ant. branch of internal iliac; medially.
After passing under the uterine A (near the level of the uterine isthmus), the ureter enters the parametrium. It lies approximately 1 to 2 cm lateral to the cervix and courses within a “ureteral tunnel” surrounded by loose areolar tissue that allows for its peristalsis. Within this tunnel, the ureter roughly separates the anterior fibers of the cardinal ligament from the posterior fibers of the uterosacral ligament. The ureter then travels anteromedially toward the bladder base. In this path, it runs close to the proximal third of the anterior vaginal wall. Finally, the ureter courses obliquely within the bladder wall for approximately 1.5 cm to terminate at the ureteric orifices.
