19. Pelvis and Perineum Flashcards
What are the 3 Bony Constituents of the Pelvic Girdle?
- Hip Bones
- Sacrum
- Coccyx
What are the 3 Sections of the Hip Bones?
- Ilium
- Ischium
- Pubis
What is the Hip Bone also known as?
Os Innominatum
Coxa Bone
How can the Hip Bone be described?
It is like a Propeller:
- Acetabulum at the Hub,
- One Blade is the Iliac Bone,
- The other Blade is the Ischium and Pubis,
- Perforated by the Obturator Foramen.
What Bones is the Sacro - Iliac Joint between?
Between the Ilium of the Hip Bones and the Sacrum
What Type of Joint is the Sacro - Iliac Joint?
Synovial Joint
What Bones is the Pubic Symphysis between?
Between the Pubis Bodies of the Two Hip Bones
What Type of Joint is the Pubic Symphysis?
Secondary Cartilaginous Joint
What are the 2 Parts of the Pelvis?
- Greater/False Pelvis
2. Lesser/True Pelvis
Where is the Greater Pelvis located?
Situated Above and In Front of the Pelvic Brim.
Found Superior to the Pelvic Inlet.
What does the Greater Pelvis contain?
Contains the Inferior Parts of the Abdominal Organs.
Occupied by portions of the Small and Large Intestines.
Why is the Greater Pelvis called the False Pelvis?
Because it is more Closely Associated with the Abdominal Cavity
Where is the Lesser Pelvis located?
The Lesser Pelvis is located between the Pelvic Inlet and Pelvic Outlet
What does the Lesser Pelvis contain?
- Bladder
- Internal Reproductive Organs
- The Perineum
Why is the Lesser Pelvis called the True Pelvis?
Because it contains the Pelvic Organs
What separates the Greater from the Lesser Pelvis?
The Pelvic Brim/Inlet forms the Superior Margin of the Lesser Pelvis,
Separating it from the Greater Pelvis.
What are the borders of the Pelvic Brim?
Anterior Border:
- Upper Margin of the Pubic Symphysis
Posterior Border:
- The Pectineal Line of the Pubis
- The Arcuate Line of the Ilium
- Sacral Promontory Posteriorly
What are the borders of the Pelvic Inlet?
Anterior:
- Pubic Symphysis
Lateral:
- Arcuate Line on the Inner Surface of the Ilium
- Pectineal Line on the Superior Pubic Ramus.
Posterior:
- Sacral Promontory
- Sacral Ala
What does the Pelvic Inlet separate?
The Pelvic Inlet marks the Boundary between the Greater Pelvis and Lesser Pelvis.
What is the Sacral Promontory?
The Anterior Margin of the Superior Sacrum.
How is the Pelvic Inlet related to Childbirth?
The Pelvic Inlet determines the size and shape of the Birth Canal.
What attaches to the Pelvic Inlet?
The Prominent Ridges of the Pelvic Inlet are key areas of Muscle and Ligament Attachment.
Where is the Pelvic Oulet located?
The Pelvic Outlet is located at the End of the Lesser Pelvis,
And the Beginning of the Pelvic Wall.
What are the borders of the Pelvic Outlet?
Anterior Border:
- The Pubic Arch
- Pubic Symphysisthe
- Inferior Border of the Ischiopubic Rami.
Lateral Border:
- The Ischial Tuberosities and the Inferior Margin of the Sacrotuberous Ligament.
Posterior Border:
- The Tip of the Coccyx.
What is the Sub - Pubic Angle?
The Angle beneath the Pubic Arch is known as the Sub - Pubic Angle,
Is of a Greater Size in Women.
What are the 4 Varieties of Pelvic Shapes?
- Gynecoid (Female)
- Android (Male)
- Anthropoid
- Platypelloid
List the Main Features of the Female Pelvis:
- Bones are Lighter and Thinner.
- False Pelvis is Shallow.
- Pelvic Cavity is Wide and Shallow.
- Pelvic Inlet is Round and Oval.
- Pelvic Outlet comparitively Large.
- Subpubic Angle Large.
- Coccyx more Flexible and Straighter.
- Ischial Tuberosities more Everted.
List the Main Features of the Male Pelvis:
- Bones are Heavier and Thicker.
- False Pelvis is Deep.
- Pelvic Cavity is Narrow and Deep.
- Pelvic Inlet is Heart Shaped and Smaller.
- Pelvic Outlet comparitively Small.
- Subpubic Angle more Acute.
- Coccyx Less Flexible and More Curved.
- Ischial Tuberosities more Everted.
How does the the Foetal Head enter the Pelvic Inlet?
- The Foetal Head enters the Pelvic Inlet Transverse.
- As the Baby Descends, its head rotates 90 Degrees.
- The head will be Flexed and U-shaped.
- The Head then Extends During Delivery.
What is the Ideal/Common Position for the Foetal Head?
The Occiput Anterior Fetal Position is a Cephalic Presentation,
In which the Fetus is Face Down, facing the Mother’s Spine.
This is the Ideal Position for Childbirth.
How Wide is the Pelvic Inlet and Outlet?
Pelvic Inlet is 13 cm Wide,
Pelvic Outlet is only 11 cm Wide.
What is the Widest Portion of the Pelvic Outlet?
12.5 cm from top to bottom
Why does the Foetus have to Rotate?
- The Fetus has to Rotate in order to get through the Pelvic Canal.
- This is as the Pelvic Inlet is Wider than the Pelvic Oulet.
- In order to fit through the Pelvic Outlet at its Widest Dimension
- The Fetus must rotate so it presents its head to the Widest Dimension of the Pelvic Cavity,
At each Point of the Pelvic Cavity that it Passes through.
What is the Largest part of the Foetal Head?
The largest part of the Fetus is the Skull,
So the Baby’s Head Rotates First,
And the Shoulders and the Rest of the Body follow.
Where does the True Pelvis Project?
The True Pelvis projects Posteriorly into the Gluteal Region.
What does the True Pelvis contain?
Contains the Pelvic Organs.
How can the Pelvic Organs be Palpated?
Not Palpable Abdominally,
Must be Examined Vaginally/Rectally
What Angle does the Pelvic Inlet make with the Horizontal?
55 - 60 Degrees
What is the Angle of the Pelvic Inlet called?
Pelvic Inlet Angle is called Anterior Pelvic Tilt
What is the Obstetric Significance of the Anterior Pelvic Tilt?
The Mother can be repositioned during Childbirth.
Which structures does Anterior Pelvic Tilt align?
Brings the Pubic Tubercle into the same Vertical Plane as the ASIS,
And the same Horizontal Plane as the Ischial Spine.
What Angle does the Pelvic Outlet make with the Horizontal?
10 - 15 Degrees
What is the Axes of the Pelvic Cavity?
Axes describes the direction in which the Fetus progresses as it passes through the Birth Canal.
Hypothetic Curved Line joining the Center Point of each of the Four Planes of the Pelvis,
Marking the Center of the Pelvic Cavity at every level.
How would you Perform a Manual Pelvimetry?
Compare the Size of the Pelvic Cavity with a Clenched Fist
Where are the Common Sites of Fracture of the Pelvis?
- Breaks across the Top of One Ilium
- Cracks to the Pubic Ramus on one side,
- Or cracks in the Sacrum.
How is the Pelvis similar to a Pretzel?
Because the Pelvis is Shaped like a Pretzel,
When one Part of the Pelvic area is Fractured
It is likely that you will have a Fracture in another area of the Pelvis as well.
What are the Complications of a Frature to the Pelvis?
- Bleeding:
- Especially of the Iliac Artery,
- May be Profuse due to Injury to Local Blood Vessels.
- Hematuria:
- Blood in the Urine,
- Due to Injury to the Bladder or Urethra.
- The Lower Intestine or Rectum may also be Torn or Ruptured.
- Damage to Reproductive Organs
- Infection
- Venous Thrombosis
What is Symphysial Diastasis?
Separation of Normally Joined Pubic Bones.
Dislocation of the Bones, but Without a Fracture.
Who commonly suffers from Symphysial Diastasis?
Can occur spontaneously in at least 1 in 800 Vaginal Deliveries.
Common in Pregnant Women.
What are the Important Features of the Iliac Bone?
- Iliac Crest
- Tubercule of Iliac Crest
- Wing/Ala of Ilium
- Anterior Superior Iliac Spine (ASIS)
- Anterior Inferior Iliac Spine (AIIS)
- Posterior Superior Iliac Spine (PSIS)
- Posterior Inferior Iliac Spine (PIIS)
What is the Importance of the Level of the Iliac Crest?
Top of Iliac Crest also marks the level of the Fourth Lumbar Vertebral Body (L4).
A Lumbar Puncture may be performed above and below L4 as well as Epidural.
What level is the Iliac Tubercule found at?
The Iliac Tubercle is found at L5.
What is the Widest Part of the Iliac Crest?
Iliac Tubercule
Which Muscles are connected to the Iliac Crest?
Gives Partial Origin to:
- Internal Oblique Muscle
- Transversus Abdominis Muscle
Provides Insertion for:
- External Oblique Muscle
Which Muscles attach to the ASIS?
Inguinal Ligament
Sartorius Muscle
What Vertebral Level is the PSIS?
L5/S1
What is the Gluteal Surface of the Ilium?
The Gluteal Surface of the Ilium faces Posterolaterally,
Lies below the Iliac Crest.
Marked by Three Curved Lines.
Where are the Gluteal Lines located?
Posterior Aspect of the Wing/Ala of Ilium.
On the Gluteal Surface of the Ilium
What are the 3 Gluteal Lines?
- Posterior Gluteal Line
- Anterior Gluteal Line
- Inferior Gluteal Line
What do the Gluteal Lines divide?
The Gluteal Lines divide the Gluteal Surface into 4 Regions.
Where does the Inferior Gluteal Line originate?
The Inferior Gluteal Line originates just Superior to the Anterior Inferior Iliac Spine.
Where does the Inferior Gluteal Line End?
Curves Inferiorly across the Bone to End near the Posterior Margin of the Acetabulum.
Where does the Rectus Femoris Muscle attach?
The Rectus Femoris Muscle attaches to:
- Anterior Inferior Iliac Spine
- Roughened patch of Bone between the Superior Margin of the Acetabulum,
- And the Inferior Gluteal Line.
Where does the Anterior Gluteal Line originate?
The Anterior Gluteal Line originates from the Lateral Margin of the Iliac Crest,
Between the Anterior Superior Iliac Spine and the Tuberculum of the Iliac Crest.
Where does the Anterior Gluteal Line run?
Arches Inferiorly across the Ilium,
To Disappear just Superior to the Upper Margin of the Greater Sciatic Foramen.
Where does the Gluteus Minimus Muscle originate?
The Gluteus Minimus Muscle Originates from between the Inferior and Anterior Gluteal Lines.
Where does the Posterior Gluteal Line run?
The Posterior Gluteal Line descends almost Vertically from the Iliac Crest,
To a position near the Posterior Inferior Iliac Spine.
Where do the Gluteus Medius/Maximus Muscle originate?
The Gluteus Medius Muscle attaches to Bone between the Anterior and Posterior Gluteal Lines
The Gluteus Maximus Muscle attaches Posterior to the Posterior Gluteal Line.
Which Muscle occupies the Iliac Fossa?
Iliacus Muscle:
Flat, Triangular Muscle.
What is the Origin of the Iliacus Muscle?
Iliac Fossa of the Pelvis
What is the Insertion of the Iliacus Muscle?
Lesser Trochanter of the Femur.
What is the Action of the Iliacus Muscle?
Flexes the Thigh at the Hip Joint.
Flexion of the Trunk at the Hip.
External Rotation of the Thigh at the Hip.
What is the Innervation of the Iliacus Muscle?
Femoral Nerve.
Nerve Roots: L2 - L4
How is the Iliac Bone useful in Haematology?
A Bone Marrow Biopsy/Transplant or Needle Aspiration is usually done from the Iliac Bone.
What are the Important Features of the Pubic Bone?
- Body
- Superior Rami
- Obturator Foramen
- Inferior Rami
- Pubic Arch
- Pubic Crest
- Pectineal Line
- Pubic Tubercule
What Structures attach to the Pubic Tubercule?
Inguinal Ligament
What Structures attach to the Pubic Crest?
Conjoint Tendon
Rectus Abdominis
Abdominal External Oblique
What Structures attach to the Pectineal Line?
Pectineus Muscle
Pyramidalis Muscle
What forms the Lower Border of the Obturator Foramen?
Inferior Ramus
Ramus of the Ischium