2.5.3. ANAT LAB - Gluteal, Anal and Post Thigh Flashcards
What is the largest nerve in the body?
Sciatic nerve (Saphenous nerve is the longest)
What are the two triangles in the perineum?
The urogenital triangle (anterior) & the anal triangle (posterior)
What forms the pudendal canal?
What passes through the pudendal canal (3)?
The pudendal canal is formed by the obturator fascia
The pudendal artery, internal pudendal veins, and pudendal nerve pass through the pudendal canal.
Is the internal anal sphincter voluntary or involuntary?
What part of the anal canal does it surround?
Its contraction is stimulated and maintained by what?
What inhibits contraction?
The internal anal sphincter is involuntary
It surrounds the superior 2/3 of the anal canal
Contraction is stimulated and maintained by sympathetic fibers from the superior rectal and hypogastic plexuses.
Contraction is inhibited by parasympathetic fiber stimulation.
Is the external anal sphincter voluntary or involuntary?
It forms a broad band on each side of which part of the anal canal?
It is attached anteriorly to what?
What is its posterior attachment?
The external anal sphincter is a large voluntary sphincter
It forms a broad band on each side of the inferior two thirds of the anal canal
It is attached anteriorly to the perineal body
It is attached posteriorly to the coccyx via the anococcygeal ligament
What separates the superior part of the anal canal from the inferior part of the anal canal?
What are the four ways in which the superior and inferior parts of the anal canal differ?
What is the reason for the differences between the two parts of the anal canal?
The pectinate line
The superior and inferior parts of the anal canal differ in arterial supply, innervation, venous drainage, and lymphatic drainage
These differences are due to the different embryological origins of the superior and inferior parts of the anal canal
What is the puborectalis?
How does the puborectalis ‘sling’ work?
What is it’s major role?
The puborectalis is the thicker, narrower, medial part of the levator ani, consisting of muscle fibers that are continuous between the posterior aspects of the bodies of the right and left pubic bones.
It forms a U-shaped muscular sling that passes posterior to the anorectal junction bounding the urogenital hiatus.
The puborectalis plays a major role in maintaining fecal continence.
Why is the internal anal sphincter contracted most of the time?
Why/when does it relax temporarily?
It is contracted most of the time to prevent leakage of fluid or flatus.
It relaxes temporarily to distension of the rectal ampulla by feces or gas.
Gluteus maximus:
Origin (2)
Insertion (2)
Innervation
Action
Origin: Posterior gluteal line, posterior sacrum & coccyx (sacrotuberous ligament)
Insertion: Upper fibers insert on the iliotibial tract
Lower fibers insert on the gluteal tuberosity of the femur
Innervation: Inferior gluteal nerve
Action: Extends thigh and trunk, laterally rotates thigh
Gluteus medius:
Origin
Insertion
Innervation
Action
Origin: Ilium between posterior and anterior gluteal lines
Insertion: Greater trochanter of femur
Innervation: Superior gluteal nerve
Action: Abducts and medially rotates thigh
Gluteus minimus:
Origin
Insertion
Innervation
Action
Origin: Ilium between anterior and inferior gluteal lines
Insertion: Greater trochanter of femur
Innervation: Superior gluteal nerve
Action: Abducts and medially rotates thigh
Tensor fascia lata:
Origin (2)
Insertion
Innervation
Action
Origin: Anterior part of iliac crest, anterior superior iliac spine (ASIS)
Insertion: Iliotibial tract
Innervation: Superior gluteal nerve
Action: Flexes, abducts, and medially rotates thigh
Piriformis:
Origin
Insertion
Innervation
Action
Origin: Anterior surface of sacrum
Insertion: Upper border of greater trochanter of femur
Innervation: Ventral rami of S1-S2
Action: Laterally rotates and abducts thigh
Obturator internus:
Origin
Insertion
Innervation
Action
Origin: Margin of obturator foramen and internal surface of obturator membrane
Insertion: Greater trochanter, medical surface above the trochanteric fossa
Innervation: Nerve to obturator internus (L5, S1-2)
Action: Laterally rotates and abducts thigh
Obturator externus:
Origin
Insertion
Innervation
Action
Origin: External surface of obturator membrane and anterior bony margins of obturator foramen
Insertion: Posteromedial surface of greater trochanter of femur
Innervation: Obturator nerve
Action: Lateral rotation of thigh; also aids in thigh adduction
Gemellus superior:
Origin
Insertion
Innervation
Action
Origin: Ischial spine
Insertion: Medial surface of greater trochanter of femur
Innervation: Nerve to obturator internus (L5, S1)
Action: Laterally rotates thigh, abducts flexed thigh; steadies femoral head in acetabulum
Gemellus inferior:
Origin
Insertion
Innervation
Action
Origin: Ischial tuberosity
Insertion: Medial surface of greater trochanter of femur
Innervation: Nerve to quadratus femoris (L5, S1)
Action: Lateral rotation of thigh; Abducts flexed thigh; Steadies femoral head in acetabulum
Quadratus femoris:
Origin
Insertion
Innervation
Action
Origin: Lateral border of ischial tuberosity
Insertion: Quadrate tubercle on inter-trochanteric crest of femur and area inferior to it
Innervation: Nerve to quadratus femoris (L5, S1)
Action: Laterally rotates thigh; Steadies femoral head in acetabulum
Semitendinosus:
Origin
Insertion
Innervation
Action
Origin: Ischial tuberosity
Insertion: Medial surface of superior part of tibia
Innervation: Tibial nerve (L5, S1, S2) (aka Tibial division of sciatic nerve)
Action: Extends thigh; Flex leg; Medially rotate leg when knee is flexed
Semimembranosus:
Origin
Insertion
Innervation
Action
Origin: Ischial tuberosity
Insertion: Posteiror part of medial condyle of tibia
Innervation: Tibial nerve (L5, S1, S2) (aka Tibial division of the sciatic nerve)
Action: Extend thigh; Flex leg; Rotate leg medially when knee is flexed
Biceps femoris:
Origin (2)
Insertion
Innervation (2)
Action
Origins:
Long head: ischial tuberosity
Short head: linea aspera and lateral supracondylar line of femur
Insertion: Lateral side of head of fibula; tendon is split at this site by fibular collateral ligament of knee
Innervation:
Long head: Tibial nerve (L5, S1, S2)
Short head: Common fibular division of sciatic nerve (L5, S1, S2)
Action: Flexes leg and rotates it laterally when knee is flexed; extends thigh
Explain how the muscles in the hip support the pelvis when standing and walking. What is the role of the medial and lateral rotators?
When the weight is on both feet, the pelvis is evenly supported and does not sag. When the weight is borne by one limb the muscles on the supported side fix the pelvis so that it does not sag to the unsupported side. The medial rotators that act unilaterally during the stance phase (planted limb) to keep the pelvis level via abduction can simultaneously produce medial rotation at the hip joint, advancing the opposite unsupported side of the pelvis. The lateral rotators of the advancing (free) limb act during the swing phase to keep the foot parallel to the direction of advancement.
Lymphatic vessels from deep parts of the perineum accompany the internal pudendal blood vessels and drain mainly into _____ _____ nodes in the pelvis.
Internal iliac
Identify the labeled structure: (This is a picture from the cadaver’s left side)
- Gluteus Maximus
Lymphatic channels from superficial tissues of the penis or the clitoris accompany the superficial external pudendal blood vessels and drain mainly into _______ ________ nodes, as do lymphatic channels from the scrotum or labia majora.
Superficial inguinal
The glans penis, the glans clitoris, labia minora, and the terminal inferior end of the vagina drain into ________ _______ nodes and _______ _________ nodes.
Deep inguinal nodes and external iliac nodes
Identify the following structure:
- Gluteus medius
Identify the following structures:
- Superior gluteal nerve and artery
- Inferior gluteal nerve and artery
- Pyriformis muscle
Note: Pay attention to the relationship between the Superior and Inferior Nerves and Arteries and the Pyriformis muscle. This relationship helps you to identify the structures.
Identify the following structures (Note: This is a closeup of the area, showing the structures deep to the Gluteus Maximus):
- Gluteus medius
- Obturator internus
- Superior gemellus
- Quadratus femoris
- Pyriformis
- Inferior gemellus
Identify the following structures:
- Sacrotuberous ligament
- Inferior rectal nerve
- Sciatic nerve
- Inferior gluteal nerve and artery
- Inferior rectal artery (cut)
- Inferior rectal vein
What are the boundaries of the Ischioanal Fossa? (4)
Medially: Levator Ani muscle
Laterally: Obturator internus fascia
Posteriorly: Gluteus maximus muscle lying superficial to the Sacrotuberous ligament
Anteriorly: Perineal membrane
Identify the following structures:
- Sacrotuberous ligament
- Inferior rectal nerve
- Fascia of obturator internus muscle
Identify the following structures:
- Coccyx
- Sacrum
Identify the following structures:
- Ischial Spine
- Ischial tuberosity
Identify the following structures:
- Greater sciatic notch
- Lesser sciatic notch
Red circle: Greater sciatic Foramen
What makes the piriformis muscle a key anatomical/surgical landmark?
The Superior and Inferior gluteal “bundles” (nerves, arteries and veins) exist the pelvis superior and inferior to the piriformis muscle.
Where does the sciatic nerve emerge from the pelvis?
Inferior to the piriformis muscle
The pudendal nerve and internal pudendal vessels cross between the ______ spine and the ________ ligament on their way to supply the ________.
Ischial spine
Sacrospinous ligament
Supply the perineum (genitourinary areas)
