Perineum and external genitalia week 2 Flashcards
Explain the following sex differences in the pelvis:
pelvic inlet
pelvic outlet
pubic arch
Pelvic inlet.
- Female: usually more circular-shaped
- Male: more heart-shaped.
Pelvic outlet.
- Female: wider and has shorter and straighter ischial spines.
- Male: has ischial spines that project more medially. Pubic arch. (the angle between adjacent ischiopubic rami.)
- Female: usually larger (85 degrees) can be estimated by the angle between the thumb and the forefinger.
- Male: male pubic arch (60 degrees). estimated by the angle between the index and the middle fingers.
Explain the orientations fo the following structures:
anterior superior ilac spines and anterior/superior edge of pubic symphsys
pelvic inlet
urogenital triangle
anal triangle
Key Concept: Orientation of the perineum within the pelvis in the anatomic position.
- The anterior superior iliac spines and the anterior/superior edge of the pubic symphysis lie in the same vertical plane.
- The pelvic inlet faces anterior/superior.
- The urogenital triangle of the perineum is oriented in an almost horizontal plane and faces inferiorly.
- The anal triangle is more vertical and faces posteriorly.
What is contained generally within the greater pelvis? What are the boundaries of the greater pelvis? What are other names for the greater pelvis?
What is generally contained within the lesser pelvis? What are the boundaries of the lesser pelvis? What are other names for the lesser pelvis?
GREATER PELVIS (false pelvis, major pelvis)
- Superior to the pelvic brim (inlet)
- Location of some abdominal viscera (ileum, sigmoid colon)
LESSER PELVIS (true pelvis, minor pelvis)
- Between pelvic inlet (brim) and outlet
- Location of pelvic viscera
What muscles form the pelvic diaphragm?
What are the origins and insertions of the pelvic diaphragm?
What is the pelvic diaphragm innervated by?
Pelvic diaphragm
- formed by the levator ani (pubococcygeus, puborectalis, iliococcygeus) and the coccygeus muscles.
- attaches along the pubis, lateral pelvic walls, sacrum and coccyx.
Levator ani muscles insert on the anococcygeal ligament and coccyx. Coccygeus inserts on the ischial spine.
innervation: direct branches from sacral plexus
levator ani is also innervated by the inferior anal nerve
Where does the rectum exit the pelvic diaphragm?
Where does the urethera and vagina (in females) and the urethra (in males) exit the pelvic diaphragm?
- rectum pierces the center of the pelvic diaphragm.
- the urethra and vagina (in females) and the urethra (in males) pierce the pelvic diaphragm through the genital hiatus
What are the functions of the pelvic diaphragm?
Functions of the pelvic diaphragm are as follows:
- forms the floor of the pelvis and serves as a bed for the pelvic organs.
- Closes the pelvic outlet.
- Supports the abdominopelvic viscera.
- Resists increases in intra-abdominal pressure.
- Controls the openings of the rectum (e.g., helps retain or release feces during a bowel movement).
What muscles form the walls of the pelvic floor?
What are their origins and insertions?
What foramina do they pass through to their insertion points?
What are these muscles innervated by?
What are their actions?
Muscles of the Lateral Pelvic Wall - originate in the pelvic cavity but attach to the femur.
Obturator internus - a flat, fan-shaped muscle that forms a tendon that leaves the pelvic cavity through the lesser sciatic foramen, makes a 90° bend around the ischium between the ischial spine and ischial tuberosity, passes posteriorly, and crosses the hip joint to insert on the femur.
Piriformis - is triangular in shape and originates in the pelvic cavity and then passes laterally through the greater sciatic foramen, crosses the posterosuperior aspect of the hip joint, and inserts on the femur.
Innervated by direct branches from the sacral plexus.
action: stabilization of the hip, external rotation, abduction of flexed hip
Identify the following structures.
What is the location of the perineum relative to the pelvic diaphragm?
What is its shape?
What are the borders of the perineum?
Into what 2 areas is the perinuem divided into? By what imaginary line?
PERINEUM
Location: inferior to the pelvic diaphragm
Shape: diamond-shaped region
Borders: pubic symphysis, pubic arches, ischial tuberosities, and coccyx 2 triangles: (an imaginary line between the ischial tuberosities divides the perineum into 2 triangles)
- anterior (urogenital) triangle
- posterior (ischioanal) triangle
What is the perineal body?
The central tendon of the perinuem.
What are the bounaries of the urogenital triangle?
What are the general contents of the urogenital triangle?
What are the subdivisions of the urogenital triangle?
Boundaries - pubic symphysis ↔ ischiopubic rami ↔ transverse line between the ischial tuberosities The free edge of the triangle is along an imaginary line joining the two ischial tuberosities. The apex of the triangle is the pubic symphysis. The lateral edges are formed by the ischiopubic rami, which can be felt with deep palpation.
Contents - muscles, organs, vessels and nerves (VANs), erectile tissue, and glands. The urogenital triangle also contains the roots of the external genitalia and the openings of the urogenital system.
Subdivisions
A. Deep perineal space
B. Superficial perineal space
What is the deep perineal space?
What is contained within the deep perineal space in males?
What are the fascias of the deep perineal space?
An area of muscle, blood vessels, lymphatics and nerves with a superficial and a deep layer of fascia. The fascia which is on the inferior surface is formally known as the Perineal Membrane.
Deep Perineal Space
The Deep Perineal Space in males is filled with the:
- External urethral sphincter.
- Deep transverse perineal muscle.
- Bulbourethral (Cowper’s) gland. (lubrification of urethra)
- blood vessels, nerves, lymphatics
Fascias.
- The undersurface of the Deep Perineal Space is covered by inferior fascia, but since it has a formal name it is referred to as the Perineal Membrane.
- The upper surface of the Deep Perineal Space is covered by the Superior Fascia . The superior fascia does not have a formal name, just the superior fascia of the deep perineal space!
What are the origins and insertions of the deep transverse perineal muscle?
What is the deep transverse perineal muscle innervated by?
What are the actios of this muscle?
origin: inferior pubic ramus, ischial ramus
insertion: wall of vagina or prostate, perineal body
innervation: pudendal nerve (S2-S4)
action: holds pelvic organs in place, closes urethra
deep transverse perineal muscle is labeled 4 in attached pic
Where is the superficial perineal space in relation to the deep perineal space?
What fascias enclose the superficial perineal space?
What are the contents of the superificial perineal space in males?
Superficial Perineal Space
- inferior to the Deep Perineal Space
- enclosed by the perineal membrane (above) and the superficial perineal (Colles’) fascia (below).
- Superficial Perineal Space contains roots of the penis, muscles, and nerves.
When you hear superficial perineal space, think external genitalia!
see reverse
Male external genitalia
What is the corpus cavernosum?
How is the corpus cavernosum anchored? To what bony structure is it anchored?
What structures join to form the corpus cavernosum?
Where does the corpus cavernosum terminate?
Corpus cavernosum.
- paired tubes of erectile tissue
- anchored to the ischiopubic ramus by the Crura.
- Crura join in the midline to form the Corpus Cavernosum. • Corpus cavernosum terminates close to the beginning of the glans penis.
What muscle covers the beginning of the corpus cavernosum and the crura of the penis?
Ischiocavernosus muscle
Male external genitalia
What is the corpus spongiosum?
What anchors the corpus spongiosum? To what structure is it anchored?
What structure does the corpus spongiosum enclose?
What is the termination of the corpus spongiosum?
What muscle covers the corpus spongiosum?
Corpus spongiosum.
- single tube of erectile tissue.
- anchored to the perineal membrane by the Bulb of the Penis.
- Corpus spongiosum encloses the penile part of the urethra.
- terminates to form the glans penis.
- The corpus spongiosum is covered by the bulbospongiosus muscle.
Identify the labeled structures.
Identify the following parts of this cross section of a male penis.
Cross sectional anatomy of the Male External Genitalia.
- Consists of three masses of erectile tissue: 2 corpora cavernosa + 1 corpus spongiosum.
- Surrounded by tunica albuginea (dense fibrous layer)
What are the fascias of the deep perineal space of the urogenital triangle in females?
What is contained within the deep perineal space in females?
What do we mean by the Deep Perineal Space?
An area of muscle, blood vessels, lymphatics and nerves with a superficial and a deep layer of fascia. The fascia which is on the inferior surface is also called the perineal membrane. Fascia on superior surface is the superior fascia of the deep perineal space.
The Deep Perineal Space in females is filled with the:
- External urethral sphincter.
- Deep transverse perineal muscle.
- blood vessels, nerves, lymphatics
Where is the superficial perineal space in relation to the deep perineal space in females?
What fascias enclose the superficial perineal space?
What are the general contents of the superficial perineal space?
Superficial Perineal Space (FEMALE)
- inferior to the Deep Perineal Space.
- enclosed by the perineal membrane (above) and the superficial perineal (Colles’) fascia (below).
- Superficial Perineal Space contains roots of the external genitalia, muscles, and nerves.
see reverse
Female external genitalia
What are the corpora cavernosa anchored to? What anchors them to this structure?
What do the corpora cavernosa form?
What muscle covers the crura of the corpus cavernosum?
What are bulbs of the vestiule? What muscle are they covered by?
What is the vestibule?
Superficial perineal space continued (females)
- pair of erectile tissues.
- corpora cavernosa are attached to the ischiopubic rami by the crura.
- the distal ends of the corpora cavernosa fuse to form the clitoris.
- crura of the corpus cavernosum are covered by the ischiocavernosus muscle.
- bulbs of erectile tissue called the bulb of the vestibule lie on both sides of the vaginal opening and are covered by the bulbospongiosus muscle.
- the vestibule is a space that can be seen when the labia minora are separated.
What is the origin and insertion of the superficial transverse perineal muscle?
What is it innervated by?
What is its action?
origin: ishcial ramus
insertion: perineal body
innervation: pudendal nerve
action: holds pelvic organs in place, closes urethra
this muscle is in males and females
superficial transverse perineal muscle labeled 5 in picture
State what the following structures are and their anatomical relationships to each other.
mons pubis
labia majora
labia minora
vestibule
- Mons pubis. A rounded area superficial to the pubic symphysis containing adipose tissue.
- Labia majora. Paired longitudinal ridges of skin that are inferior to the mons pubis.
- Labia minora. Paired hairless skin ridges flanking a midline space known as the vestibule.
- Vestibule an area containing the urethra and the vagina.
What is the function of the greater vestibular glands?
What does the clitoris consist of? What structures are joined at the clitoris? What covers the clitoris?
- greater vestibular glands - release mucus into the vestibule for lubrication
- Clitoris
o junction of the labia minora folds.
o consists of erectile tissue that is continuous with two crura (corpora cavernosa), and a glans.
Prepuce covers the clitoris. Is like a hood.
What fascia do the pudendal nerve and internal pudendal artery and vein travel in? What does this form?
The pudendal nerve and the internal pudendal artery and vein, travel in the fascia of the obturator internus muscle forming the pudendal (Alcock’s) canal.
What is the ischioanal fossa? What is its purpose?
KEY CONCEPT: The ischioanal fossa is a cavernous structure with several recesses. These recesses are filled with fat. This fat helps to protect all the vessels and nerves passing through this region.
Ischio-anal fossa on each side of the anal aperture. Careful palpation and dissection of this region should expose the greater and lesser sciatic foramina formed by the sacrotuberous and sacrospinous ligaments. The piriformis muscle (greater sciatic foramen) and internal obturator muscle (lesser sciatic foramen) can be located along with the pudendal nerve and internal pudendal artery and vein.
